Name: using polystyrene-block-poly(acrylic acid)-coated metal nanoparticles as monomers for their homo- and co-polymerization
Uploaded: 2015-07-09T15:00:00.000+00:00
Duration: 9 min 2 s
Description: Watch this Scientific Journal Video about Using Polystyrene-block-polyacrylic acid-coated Metal Nanoparticles as Monomers for Their Homo- and Co-polymerization at JoVE.com

The authors thank the NRF (CRP-4-2008-06), A*Star (SERC 112-120-2011) and MOE (RG14/13) Singapore for financial supports.

Caution: Please consult all relevant material safety data sheets (MSDS). Some chemicals used in these syntheses are corrosive, toxic and possibly carcinogenic. Nanomaterials may have unrecognized hazards as compared to their bulk counterparts. Please use appropriate safety practices when performing reaction, including the use of fume hood and personal protective equipment (safety glasses, gloves, lab coat, full length pants, closed-toe shoes, etc.).
1. Synthesis of Metal Nanoparticles
Note: All glassware used in the syntheses are washed with aqua regia (CAUTION: highly acidic and corrosive, handle with caution and dispose following the regulations), thoroughly rinsed, and then dried in 60 &#176;C oven. Metal impurity or residue may lead to premature nucleation and failure of the nanoparticle synthesis.
<ol>
	<li>Synthesis of 16 and 32 nm Au nanoparticles (AuNPs)
	<ol>
		<li>Dissolve 10 mg of hydrogen tetrachloroaurate(III) hydrate (HAuCl4&#8729;3H2O) into 100 ml of deionized (DI) water in a round-bottom flask equipped with a condenser and a stir bar.</li>
		<li>With stirring on, heat the solution to reflux (boiling, 100 &#176;C). The yellow color of the HAuCl4 remains unchanged.</li>
		<li>Prepare a 1% sodium citrate solution by dissolving 30 mg of sodium citrate into 3 ml of DI water.</li>
		<li>To synthesize 16 nm AuNPs, inject 3 ml of 1% sodium citrate solution (1.1.3) into the boiling HAuCl4 solution (1.1.2). The solution turns grey within 1 min, and then gradually turns red.
		<ol>
			<li>To synthesize 32 nm Au NPs, use 1.5 ml of the sodium citrate solution instead. The smaller amount of reductant leads to less extensive homogeneous nucleation, so that each nucleus can grow larger.</li>
		</ol>
		</li>
		<li>Keep the solution at boiling for another 30 min, and then cool down to RT for use in the subsequent reactions.</li>
		<li>Confirm the size and morphology of the resulting AuNPs by transmission electron microscopy (TEM).
		<ol>
			<li>To prepare the TEM sample, first concentrate the AuNPs by transferring 1.5 ml of the as-synthesized solution into a microcentrifuge tube, and centrifuge it at 16,000 x g for 15 min. After removing the transparent supernatant, drop a 10 &#181;l aliquot of the residue solution onto a TEM copper grid. Wick off the excess liquid sample using a filter paper and dry the copper grid in air.</li>
			<li>To conduct the TEM characterization, load the copper grid sample into the TEM holder, secure the sample, and load the holder into the specimen chamber following the standard operation procedures (specific to the type/brand of instrument).22</li>
		</ol>
		</li>
	</ol>
	</li>
	<li>Synthesis of Au nanorods (AuNRs)
	<ol>
		<li>Prepare the seed solution. Under vigorous stirring, add 0.6 ml of 10 mM ice-cooled sodium borohydride (NaBH4) to 10 ml of 0.25 mM HAuCl4&#8729;3H2O prepared in 0.1 M hexadecyltrimethylammonium bromide (CTAB) solution. Continue stirring for 10 min.</li>
		<li>Add 95 ml of 0.1 M CTAB, 1 ml of 10 mM silver nitrate (AgNO3), 5 ml of 10 mM HAuCl4&#8729;3H2O in sequence into a 200 ml conical flask.</li>
		<li>Add 0.55 ml of 0.1 M L-ascorbic acid to the solution, and shake gently to homogenize the solution.</li>
		<li>Immediately add 0.12 ml of the seed solution (Step 1.2.1). Mix the solution by gentle shaking and leave it undisturbed O/N (14-16 hr).</li>
	</ol>
	</li>
	<li>Synthesis of t-Te nanowires (TeNWs)
	<ol>
		<li>Prepare 10 ml of N2H4 solution by mixing 1 ml of neat N2H4&#183;H2O with 9 ml of DI water.</li>
		<li>Add 16 mg of TeO2 powder slowly to the N2H4 solution (Step 1.3.1) in a beaker at RT under constant stirring. In about 10 min, the powder completely dissolves. The solution would change from colorless to amber, to purple, and eventually to blue, indicating the formation of t-Te nanowires.</li>
		<li>Dilute the solution 10 times with sodium dodecylsulfate (10 mM) to terminate the reaction. The blue color of the solution becomes less intense after the dilution.</li>
	</ol>
	</li>
</ol>
2. Synthesis of PSPAA Encapsulated Metal Nanoparticles (the Monomers)
Note: In the following, precise amounts are used to achieve a precise ratio of the final DMF/water solvent mixture. Because the residue volume after centrifugation and extraction of the supernatant is always different, roughly measure the residue volume by pipette and then compensate for this volume when adding DMF/water to make the final solutions. Small variations of the solvent ratio are usually not a problem.
<ol>
	<li>Encapsulate AuNPs (dAu= 16 nm, 32 nm) with PSPAA (AuNP@PSPAA)
	<ol>
		<li>Purification of the AuNP solution. Add 3 ml of the as-synthesized AuNP solution (Step 1.1) to two microcentrifuge tubes (1.5 ml each), centrifuge at 16,000 x g for 15 min and remove the supernatant. Dilute the concentrated solution (~20 &#181;l) with 160 &#181;l of DI water.</li>
		<li>Prepare the PSPAA stock solution by dissolving 8 mg of PSPAA (PS154-b-PAA49 or PS144-b-PAA22) in 1 ml of DMF.</li>
		<li>Prepare a PSPAA solution by mixing 740 &#181;l of DMF with 80 &#181;l of PS154-b-PAA49 stock solution. For encapsulating the AuNPs in PS144-b-PAA22 shells, use 80 &#181;l of PS144-b-PAA22 stock solution.</li>
		<li>In a glass vial, add the AuNPs (~180 &#181;l solution, step 2.1.1) to 820 &#181;l of the PSPAA solution (Step 2.1.3). The final mixture has a volume of 1 ml with VDMF/VH2O = 4.5:1.</li>
		<li>Add 40 &#181;l solution of 1,2-dipalmitoyl-sn-glycero-3-phosphothioethanol (P-SH) in ethanol (2 mg/ml).</li>
		<li>Incubate the mixture at 110 &#176;C for 2 hr to allow polymer self-assembly.</li>
		<li>Slowly cool the solution to RT in the oil bath. The sample can be stored at this state for weeks.</li>
		<li>Confirm the formation of AuNP@PSPAA with TEM.
		<ol>
			<li>To prepare the TEM sample, concentrate the AuNP@PSPAA by transferring 200 &#181;l of the as-synthesized solution into a microcentrifuge tube, add 1.3 ml of DI water and centrifuge it at 16,000 x g for 15 min.</li>
			<li>Mix a 5 &#181;l aliquot of concentrated sample solution with 5 &#181;l of 1% ammonium molybdate stain solution (Note: stain is used for samples containing PSPAA to improve the contrast of the polymers), and drop the mixture onto a TEM copper grid. Wick off the excess liquid sample using a filter paper and dry the copper grid in air.</li>
		</ol>
		</li>
	</ol>
	</li>
	<li>Encapsulate AuNRs with PSPAA (AuNR@PS154-b-PAA49)
	<ol>
		<li>Purify the as-synthesized AuNR solution (Step 1.2) twice to remove the excess CTAB. Add 3 ml of the AuNR solution into two microcentrifuge tubes, and then centrifuge them at 8,100 x g for 15 min. After removing the supernatant, add 1.5 ml of DI water and centrifuge again to remove the supernatant.</li>
		<li>Combine the concentrated AuNR solutions, and add 160 &#181;l of DI water.</li>
		<li>In a glass vial, add the AuNR solution (~180 &#181;l) to 820 &#181;l of the PS154-b-PAA49 solution (Step 2.1.3). The final mixture has a volume of 1 ml with VDMF/VH2O = 4.5:1.</li>
		<li>Add 40 &#181;l solution of 2-naphthalenethiol (NpSH) in ethanol (2 mg/ml) into the mixture.</li>
		<li>Incubate the mixture at 110 &#176;C for 2 hr to allow polymer self-assembly.</li>
		<li>Slowly cool the solution to RT.</li>
	</ol>
	</li>
	<li>Encapsulate TeNWs with PSPAA (TeNW@PS154-b-PAA49)
	<ol>
		<li>Purify the as-synthesized TeNWs (Step 1.3) to remove the excess SDS. Add 3 ml of the TeNW solution into two microcentrifuge tubes, and centrifuge them at 2,900 x g for 10 min. After removing the supernatant, add 1.5 ml of ethanol and centrifuge the tubes again. Repeat this purification process once more (total 3 rounds of centrifugation).</li>
		<li>Combine the concentrated TeNWs solutions, and add 160 &#181;l of DI water.</li>
		<li>Add the TeNWs solution (~180 &#181;l) to 820 &#181;l of PS154-b-PAA49 solution (Step 2.1.3). The final mixture has a volume of 1 ml with VDMF/VH2O = 4.5:1.</li>
		<li>Incubate the mixture at 110 &#176;C for 2 hr.</li>
		<li>Slowly cool the solution to RT.</li>
	</ol>
	</li>
	<li>Encapsulate carbon nanotubes (CNTs) with PSPAA (CNT@PS154-b-PAA49)
	<ol>
		<li>Mix 730 &#181;l DMF with 80 &#181;l of the PS154-b-PAA49 stock solution (Step 2.1.2).</li>
		<li>Disperse about 0.05 mg of single-wall CNTs into the PS154-b-PAA49 solution. 
		Note: It is hard to measure the small weight of the CNTs; usually 0.2 mg of CNTs is weighed and about &#188; of the sample (by estimated volume) is added.</li>
		<li>Sonicate the mixture in an ice-water bath until it becomes a transparent dark solution. Use the clear solution and discard the insoluble residue CNTs.</li>
		<li>Add 180 &#181;l of DI H2O drop-wise to the solution. The final mixture has a volume of 990 &#181;l with VDMF/VH2O = 4.5:1.</li>
		<li>Sonicate the solution at about 50 &#176;C for 2 hr.</li>
		<li>Slowly cool the solution to RT.</li>
	</ol>
	</li>
	<li>Prepare spherical micelles of PS154-b-PAA49.
	<ol>
		<li>Add 80 &#181;l of the PS154-b-PAA49 stock solution (Step 2.1.1) to 740 &#181;l of DMF, then add 180 &#181;l water, making a solution of VDMF/VH2O = 4.5:1.</li>
		<li>Incubate the polymer solution at 110 &#176;C for 2 hr.</li>
		<li>Slowly cool the solution to RT.</li>
	</ol>
	</li>
</ol>
3. Homo-polymerization of the PSPAA Encapsulated Metal Nanoparticles
<ol>
	<li>Synthesis of single-line chains from the AuNP@PSPAA
	<ol>
		<li>Purify the AuNP@PSPAA.
		<ol>
			<li>Dilute 800 &#181;l of the as-synthesized AuNP@PSPAA (section 2.1) with 11.2 ml of water, divide the solution into individual microcentrifuge tubes (1.5 ml each), and centrifuge them at 16,000 x g for 30 min. Carry out two separate reactions, using the 16 nm AuNPs encapsulated in PS154-b-PAA49 and the 32 nm AuNPs encapsulated in PS144-b-PAA22 as the monomers.</li>
			<li>Remove and discard the supernatant, add 1.5 ml of 0.1 mM NaOH (pH = 10) to each tube and centrifuge them again at 16,000 x g for 30 min to remove the supernatant. 
			Note: The pH of the NaOH used for centrifugation in the purification process should not be too high. Higher pH would lead to aggregation during the centrifugation, and the residue base would comprise the effects of acid in the chain-growth step, leading to globular aggregates.</li>
		</ol>
		</li>
		<li>Disperse the concentrated AuNP@PSPAA (combine all the tubes) in 1 ml of DMF/H2O (VDMF/VH2O = 6:1) in a glass vial, and add 5 &#181;l of 1 M HCl. 
		Note: It is important to control the residue NaOH and loss of the AuNP@PSPAA in the previous steps, so that the HCl amount required in the assembly process is consistent among the different batches. Vortex the reaction mixture before incubation to ensure complete mixing of the components.</li>
		<li>Incubate the mixture at 60 &#176;C for 2 hr to allow the aggregation, coalescence, and morphological transformation of the core-shell nanoparticles.</li>
		<li>Cool the mixture to RT.</li>
		<li>For homo-polymerization of the AuNR@PS154-b-PAA49 and TeNW@PS154-b-PAA49, follow the same procedures, including the purification processes. 
		Note: In the experiments, plastic microcentrifuge tubes are typically used for purification and centrifugation, and glass vials are used for the reactions at elevated temperature. The PSPAA-coated nanoparticles are usually stable in solutions, except that when dispersed in high-DMF content solution in microcentrifuge tubes, they will stick to the plastic surface. To avoid this situation, high-DMF content solutions of the nanoparticles are only prepared in glass vials.</li>
	</ol>
	</li>
	<li>Synthesis of double-line chains from the AuNP@PSPAA
	<ol>
		<li>Purify the AuNP@PSPAA (by following Step 3.1.1). Only the 16 nm AuNPs encapsulated in PS154-b-PAA49 shells have been tested.</li>
		<li>Disperse the concentrated AuNP@PSPAA in 1 ml of DMF/H2O (VDMF/VH2O = 7:3) in a glass vial, and add 5 &#181;l of 1 M HCl.</li>
		<li>Incubate the mixture at 60 &#176;C for 2 hr.</li>
		<li>Cool the mixture to RT.</li>
	</ol>
	</li>
	<li>Purification of the nanoparticle chains 
	Note: The as-synthesize solutions contain the product nanoparticle chains, small chains/clusters, large agglomerates, AuNP@PSPAA monomers, empty PSPAA micelles, DMF and excess acid.
	<ol>
		<li>Remove the empty PSPAA micelles, DMF and acid.
		<ol>
			<li>Dilute 800 &#181;l of the as-synthesized solution with 11.2 ml of 0.1 mM NaOH, divide the solution into individual microcentrifuge tubes (1.5 ml each), and centrifuge them at 16,000 x g for 30 min.</li>
			<li>Add 1.5 ml of 0.1 mM NaOH to dilute the concentrated solutions, and centrifuge the tubes again at 16,000 x g for 30 min. Repeat this step once more.</li>
		</ol>
		</li>
		<li>Enrich the AuNPs chains 
		Note: The purified solution contains the product nanoparticle chains, small chains/clusters, and AuNP@PSPAA monomers. They were separated by differential centrifugation.
		<ol>
			<li>Centrifuge the tube at 300 x g for 25 min to isolate and remove the large agglomerates.</li>
			<li>Collect the supernatant, centrifuge it at 2,000 x g for 30 min. Remove the supernatant containing mostly monomers and small chains/clusters.</li>
			<li>Collect the bottom solution, dilute it in 1.5 ml of 0.1 mM NaOH, and centrifuge at 2,000 x g for 20 min to remove excess monomers. Repeat the process once more. 
			Note: The pH of the NaOH used in the centrifugation in the all purification process should not be too high. Higher pH would lead to aggregation during the centrifugation, causing the formation of globular aggregates.</li>
		</ol>
		</li>
	</ol>
	</li>
	<li>Transformation of single-line nanoparticle chains to double-/triple-line chains
	<ol>
		<li>Purify the single-line chains (Step 3.3.1, without the enriching step).</li>
		<li>Concentrate 800 &#181;l of the purified solution to ~20 &#181;l by centrifugation.</li>
		<li>To transform to double-line chains, disperse the solution in 1 ml of DMF/H2O mixture solvent (VDMF/VH2O = 7:3) and add 2.5 &#181;l of 1 M HCl, [HCl]final = 2.5 mM. To transform to triple-line chains, use 1 ml of DMF/H2O (VDMF/VH2O = 3:2) and 2.5 mM [HCl]final.</li>
		<li>Incubate the solution at 70 &#176;C for 1 hr to allow the transformation of the nanostructures.</li>
		<li>Slowly cool the solution to RT.</li>
	</ol>
	</li>
</ol>
4. Co-polymerization of the PSPAA Encapsulated Metal Nanoparticles
<ol>
	<li>Random co-polymerization of the 16 nm AuNP@PS154-b-PAA49 and the 32 nm AuNP@PS144-b-PAA22. The process is very similar to Step 3.1 except that two monomers are used.
	<ol>
		<li>Purify the two types of the as-synthesized AuNP@PSPAA separately (Step 3.1.1).</li>
		<li>Disperse the concentrated 16 nm AuNP@PS154-b-PAA49 and 32 nm AuNP@PS144-b-PAA22 in 1:1 ratio into 1 ml of DMF/H2O mixture (VDMF/VH2O = 6:1).</li>
		<li>Add 5 &#181;l of 1 M HCl, [HCl]final = 5 mM.</li>
		<li>Incubate the solution at 60 &#176;C for 2 hr to allow co-assembly of the nanoparticles.</li>
		<li>Cool the solution to RT.</li>
	</ol>
	</li>
	<li>Random co-polymerization of the 16 nm AuNP@PS154-b-PAA49 and AuNR@PS154-b-PAA49
	<ol>
		<li>Purify the AuNP@ PS154-b-PAA49 and AuNR@ PS154-b-PAA49 separately (Step 3.1.1).</li>
		<li>Disperse the AuNP@PS154-b-PAA49 and AuNR@PS154-b-PAA49 in 1:1 ratio into 1 ml of DMF/H2O mixture (VDMF/VH2O = 6:1).</li>
		<li>Add 5 &#181;l of 1 M HCl, [HCl]final = 5 mM.</li>
		<li>Incubate the solution at 60 &#176;C for 2 hr to allow co-assembly of the nanoparticles.</li>
		<li>Cool the solution to RT.</li>
	</ol>
	</li>
	<li>Random co-polymerization of the 16 nm AuNP@PS154-b-PAA49 and PS154-b-PAA49 micelles
	<ol>
		<li>Purification of the 16 nm AuNP@PS154-b-PAA49 (Step 3.1.1).</li>
		<li>Add the concentrated AuNP@PS154-b-PAA49 and 60 &#181;l of the spherical PS154-b-PAA49 micelles (Step 2.5) into 940 ml of DMF/H2O. In the final solution, VDMF/VH2O = 6:1.</li>
		<li>Add 5 &#181;l of 1 M HCl, [HCl]final = 5 mM.</li>
		<li>Incubate the solution at 60 &#176;C for 1.5 hr.</li>
		<li>Cool the solution to RT.</li>
	</ol>
	</li>
	<li>Random co-polymerization of AuNP@PS154-b-PAA49 and PS154-b-PAA49 vesicles
	<ol>
		<li>Follow the same procedures as Step 4.3.1-4.3.3.</li>
		<li>Incubate the solution at 60 &#176;C for 6 hr to allow shape transformation of the PSPAA cylinders to vesicles.</li>
		<li>Cool the solution to RT.</li>
	</ol>
	</li>
	<li>Block-copolymerization of TeNWs with AuNPs
	<ol>
		<li>Purify the 16 nm AuNP@PS154-b-PAA49 and TeNW@PS154-b-PAA49 (Step 3.1.1)</li>
		<li>Disperse the concentrated TeNW@PS154-b-PAA49 in 1 ml of DMF/H2O mixture (VDMF/VH2O = 6:1)</li>
		<li>Add 2 &#181;l of 1 M HCl.</li>
		<li>Incubate the mixture at 60 &#176;C for 20 min.</li>
		<li>Add the concentrated 16 nm AuNP@PS154-b-PAA49 and 3 &#181;l of 1 M HCl.</li>
		<li>Incubate the mixture at 60 &#176;C for 2 hr.</li>
		<li>Cool the solution to RT.</li>
		<li>For block-copolymerization of CNTs with AuNPs, follow the same procedures as Step 4.5.1-4.5.7 by using CNT@PS154-b-PAA49 (Step 2.4).</li>
	</ol>
	</li>
</ol>

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Ed. 47, 3984-3987 (2008).</li><li>Yang, M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Mechanistic+investigation+into+the+spontaneous+linear+assembly+of+gold+nanospheres.">Mechanistic investigation into the spontaneous linear assembly of gold nanospheres.</a> Phys. Chem. Chem. Phys. 12, 11850-11860 (2010).</li><li>Keng, P. Y. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Colloidal+Polymerization+of+Polymer-Coated+Ferromagnetic+Nanoparticles+into+Cobalt+Oxide+Nanowires.">Colloidal Polymerization of Polymer-Coated Ferromagnetic Nanoparticles into Cobalt Oxide Nanowires.</a> ACS Nano. 3, 3143-3157 (2009).</li><li>Xia, H., Su, G., Wang, D. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Size-Dependent+Electrostatic+Chain+Growth+of+pH-Sensitive+Hairy+Nanoparticles.">Size-Dependent Electrostatic Chain Growth of pH-Sensitive Hairy Nanoparticles.</a> Angew. Chem. Int. Ed. 52, 3726-3730 (2013).</li><li>Wang, H. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Unconventional+Chain-Growth+Mode+in+the+Assembly+of+Colloidal+Gold+Nanoparticles.">Unconventional Chain-Growth Mode in the Assembly of Colloidal Gold Nanoparticles.</a> Angew. Chem. Int. Ed. 51, 8021-8025 (2012).</li><li>Wang, H. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Homo-+and+Co-polymerization+of+Polysytrene-block-Poly(acrylic+acid)-Coated+Metal+Nanoparticles.">Homo- and Co-polymerization of Polysytrene-block-Poly(acrylic acid)-Coated Metal Nanoparticles.</a> ACS Nano. 8, 8063-8073 (2014).</li><li>Fred, G. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Controlled+Nucleation+for+Regulation+of+Particle-size+in+Monodisperse+Gold+Suspensions.">Controlled Nucleation for Regulation of Particle-size in Monodisperse Gold Suspensions.</a> Nature-Phys. Sci. 241, 20-22 (1973).</li><li>Gole, A., Murphy, C. J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Azide-Derivatized+Gold+Nanorods:+Functional+Materials+for+&#8220;Click&#8221;+Chemistry.">Azide-Derivatized Gold Nanorods: Functional Materials for &#8220;Click&#8221; Chemistry.</a> Langmuir. 24, 266-272 (2007).</li><li>Lin, Z. -. H., Yang, Z., Chang, H. -. T. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Preparation+of+Fluorescent+Tellurium+Nanowires+at+Room+Temperature.">Preparation of Fluorescent Tellurium Nanowires at Room Temperature.</a> Cryst. Growth Des. 8, 351-357 (2007).</li><li>Xia, Y. N., Xiong, Y. J., Lim, B., Skrabalak, S. E. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Shape-Controlled+Synthesis+of+Metal+Nanocrystals.">Shape-Controlled Synthesis of Metal Nanocrystals.</a> Simple Chemistry Meets Complex Physics? Angew. Chem. Int. Ed. 48, 60-103 (2009).</li><li>Chen, H. Y. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Encapsulation+of+Single+Small+Gold+Nanoparticles+by+Diblock+Copolymers.">Encapsulation of Single Small Gold Nanoparticles by Diblock Copolymers.</a> ChemPhysChem. 9, 388-392 (2008).</li><li>Kang, Y., Taton, T. A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Controlling+Shell+Thickness+in+Core&#8722;Shell+Gold+Nanoparticles+via+Surface-Templated+Adsorption+of+Block+Copolymer+Surfactants.">Controlling Shell Thickness in Core&#8722;Shell Gold Nanoparticles via Surface-Templated Adsorption of Block Copolymer Surfactants.</a> Macromolecules. 38, 6115-6121 (2005).</li><li>Kang, Y., Taton, T. A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Core/Shell+Gold+Nanoparticles+by+Self-Assembly+and+Crosslinking+of+Micellar.+Block-Copolymer+Shells.">Core/Shell Gold Nanoparticles by Self-Assembly and Crosslinking of Micellar. Block-Copolymer Shells.</a> Angew. Chem. Int. Ed. 44, 409-412 (2005).</li><li>Chen, Y., Cui, H., Li, L., Tian, Z., Tang, Z. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Controlling+micro-phase+separation+in+semi-crystalline/amorphous+conjugated+block+copolymers.">Controlling micro-phase separation in semi-crystalline/amorphous conjugated block copolymers.</a> Polymer Chemistry. 5, 4441-4445 (2014).</li><li>Bates, F. S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Polymer-Polymer+Phase+Behavior.">Polymer-Polymer Phase Behavior.</a> Science. 251, 898-905 (1991).</li><li>Zhang, L. F., Shen, H. W., Eisenberg, A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Phase+separation+behavior+and+crew-cut+micelle+formation+of+polystyrene-b-poly(acrylic+acid)+copolymers+in+solutions.">Phase separation behavior and crew-cut micelle formation of polystyrene-b-poly(acrylic acid) copolymers in solutions.</a> Macromolecules. 30, 1001-1011 (1997).</li><li>Yu, Y., Zhang, L., Eisenberg, A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Morphogenic+Effect+of+Solvent+on+Crew-Cut+Aggregates+of+Apmphiphilic+Diblock+Copolymers.">Morphogenic Effect of Solvent on Crew-Cut Aggregates of Apmphiphilic Diblock Copolymers.</a> Macromolecules. 31, 1144-1154 (1998).</li><li>Liu, C. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Toroidal+Micelles+of+Polystyrene-block-Poly(acrylic+acid).">Toroidal Micelles of Polystyrene-block-Poly(acrylic acid).</a> Small. 7, 2721-2726 (2011).</li></ol>

The authors have nothing to disclose.

The mechanistic details of the syntheses are reported and discussed in the previous publications.20,21 Here we focus on the rationales of the synthetic conditions. For the polymerization of nanoparticles, it is preferred that nanoparticles of uniform size are used. We follow literature procedures to obtain the uniform Au nanoparticles,23 Au nanorods,24 and Te nanowires.25 In general, better size uniformity can be obtained when the nucleation and growth stages are separated.26 After the initial burst of homogeneous nucleation, all nuclei grow at the same rate for a same period, giving nanoparticles of similar sizes. Thus, the size of the nanoparticles depends on the total amount of growth material and total number of nuclei formed at the initial nucleation stage.
The encapsulation of the nanoparticles by PSPAA has been previously reported and discussed.27-29 The driving force of the PSPAA self-assembly is the phase segregation between PS and PAA domains.30,31 In a polar solvent, PSPAA forms micelles, with the PS blocks in the center and PAA blocks dissolved in the solvent facing outwards. In the presence of nanoparticles that are functionalized with hydrophobic ligands, the PS blocks can adsorb on the nanoparticle surface via van der Waals and hydrophobic interactions, forming a micellar shell with surface PAA blocks (Figure 1A-E). In the synthesis here, excess PSPAA is used to achieve single encapsulation of the nanoparticles.27 The excess polymer remains as empty PSPAA micelles (without nanoparticles) after the encapsulation and can be easily separated by centrifugation. The &#8211;SH ended hydrophobic ligands (P-SH and Np-SH) are used to render the surface of AuNPs and AuNRs hydrophobic. We add the ligands after PSPAA to minimize the aggregation among the hydrophobic nanoparticles. For TeNWs, no surface ligand is necessary as their surface is intrinsically hydrophobic. The solvent ratio (VDMFVH2O) is of importance, in terms of improving the mobility of PS domains by swelling32 and controlling the morphology of PSPAA micelles.33,34 Elevated temperature (60&#8211;110 &#176;C) is used to promote the association/dissociation dynamics of the polymer micelles so that near equilibrium conditions can be attained.
The polymerization of nanoparticle chains is driven by the tendency of the PSPAA micelles to transform from spheres to cylinders. As acid is added to protonate the surface PAA blocks and reduce their mutual repulsion, the transformation towards cylindrical micelles is thermodynamically favorable in terms of reducing the surface-to-volume ratio (S/V) of the micelles. The VDMFVH2O solvent ratio affects the polymer-solvent interfacial energy. The PS domain with a lower degree of swelling is more dissimilar to the solvent and thus the polymer-solvent interfacial energy is higher. In the synthesis, elevated temperature (60 &#176;C) is used to promote the coalescence of PSPAA domains after the nanoparticles aggregate. High DMF content solvent (VDMF: VH2O = 6:1) is used for synthesizing single-line nanoparticle chains (Figure 2A, 2B, 2D), whereas solvent with higher water content (VDMF : VH2O = 7:3) is used for synthesizing double-line chains (Figure 2C).
The extent of monomer aggregation depends on their mutual charge repulsion and reaction time. For 32 nm AuNPs, their large size leads to stronger charge repulsion (assuming a same surface charge density). Addition of more acid can lead to more extensive aggregation but it compromises the selectivity of chain formation.20 Thus, polymers with shorter PAA blocks (PS144-b-PAA22) are employed to reduce the charge repulsion without compromising the selectivity (Figure 2B).
To achieve &#8220;co-polymerization&#8221; of nanoparticles, two types of PSPAA-coated monomers are used in the self-assembly. When they are mixed before the addition of acid, random &#8220;copolymer&#8221; chains would be obtained (Figure 3A-B). The ratio of two types of nanoparticles in the resulting chains depends on, but is not directly proportional to, the initial concentration ratio of the monomers. Empty PSPAA micelles can also be used as monomers, giving cylindrical polymer segments within the nanoparticle chains (Figure 3C). Such segments can be transformed to vesicles upon prolonged heating (6 hr) at 60 &#176;C (Figure 3D). Block-chains of nanoparticles are more difficult to prepare, as the chains after synthesis and purification cannot be readily re-activated for the addition of 2nd type of monomers. Without purification, monomers remained in the sample after forming the 1st block would interfere with the growth of the 2nd block. We use CNTs and TeNWs with a high aspect ratio to construct the 1st block, so that nanoparticles can &#8220;polymerize&#8221; within the same reaction mixture for the growth of the 2nd block (Figure 3E-F).
In conclusion, we demonstrate a general method to prepare the PSPAA encapsulated nanoparticles chains. Metal nanoparticles with different size and aspect ratios are shown to aggregate into &#8220;homo-polymers&#8221;, which can be controlled from single-line to triple-line chains. Random or block &#8220;copolymers&#8221; of nanoparticles are also prepared by combining two types of the PSPAA encapsulated nanoparticles. Developing these new reaction pathways and exploring the underlying mechanisms are the stepping stones towards the rational synthesis of complex nanodevices.

Despite great advances in the synthesis of nanoparticles over the past two decades, their orderly assembly remains a great challenge. Our synthetic capabilities in putting the basic building blocks together are of critical importance for the exploration and exploitation of their synergistic effects and collective properties. Thus, developing new reaction pathways and exploring the underlying mechanisms are the stepping stones towards the rational synthesis of complex nanodevices. 
Among the rich structural variety of possible nanoparticle assemblies, one-dimensional (1D) chains have shown useful applications in nanoelectronics, optoelectronics, and biosensors.1-4 Typically, self-assembly of nanoparticles into chain-like structures requires magnetic or electric dipole interactions, anisotropic electrostatic repulsion, or external templates.5-11 For dipole-induced assembly, one needs nanoparticles with permanent dipoles, such as magnetic nanoparticles and semiconductor nanoparticles under special environments.12-15 For nanoparticles with no permanent dipole, it has been shown that the relatively weaker electrostatic repulsion at the ends of the nanoparticle chains can promote the selective attachment of nanoparticle thereon and thus, 1D chain growth.16,17 Because the nanoparticles can aggregate with each other and with the oligomers, the aggregation often follows the intrinsic step-growth mode, leading to short chain length and the lack of control over branching. Lastly, nanoparticles can be adsorbed onto 1D templates to form chains, but usually it is very difficult to achieve secure anchoring and avoid gaps among the nanoparticles. 
With these existing methods, hetero-assembly or &#8220;co-polymerization&#8221; of nanoparticles is particularly difficult. A few pioneer works have demonstrated the &#8220;co-polymerization&#8221; of short nanoparticle chains exploiting magnetic dipole18 or electrostatic repulsion.19
Recently, we reported the homo- and co-polymerization of PSPAA-coated nanoparticles into chains.20,21 This new synthetic pathway involves facile colloidal synthesis and generic use of different types of nanoparticles. It affords ultralong chains without branching and allows ready control of their length and width (single-, double-, and triple-line chains). Most importantly, random- and co-polymers of nanoparticles can be synthesized with improved structural control. In this work, we provide video protocols for the related syntheses, intending to give a detailed demonstration and presentation.

<table><tbody><tr><td>Gold(III) chloride trihydrate, ACS reagent, &amp;ge;49.0% Au basis</td><td>Sigma-Aldrich</td><td>G4022</td><td>HAuCl&lt;sub&gt;4&lt;/sub&gt;</td></tr><tr><td>Sodium citrate dihydrate, 99%</td><td>Alfa Aesar</td><td>A12274</td><td></td></tr><tr><td>Sodium borohydride, &amp;ge;99%</td><td>Sigma-Aldrich</td><td>71321, Fluka</td><td></td></tr><tr><td>Hexadecyltrimethylammonium bromide, &amp;ge;98%</td><td>Sigma-Aldrich</td><td>H5882</td><td>CTAB</td></tr><tr><td>Silver Nitrate, 99.9999% trace metals basis</td><td>Sigma-Aldrich</td><td>204390</td><td></td></tr><tr><td>L-ascorbic acid, BioXtra, &amp;ge;99.0%, crystalline</td><td>Sigma-Aldrich</td><td>A5960</td><td></td></tr><tr><td>Tellurium dioxide, &amp;ge;99%&amp;nbsp;</td><td>Sigma-Aldrich</td><td>243450</td><td></td></tr><tr><td>Hydrazine monohydrate, 64-65%, reagent grade, 98%</td><td>Sigma-Aldrich</td><td>207942</td><td></td></tr><tr><td>Poly(styrene-&lt;em&gt;b&lt;/em&gt;-acrylic acid) (PS&lt;sub&gt;154&lt;/sub&gt;-PAA&lt;sub&gt;49&lt;/sub&gt;)</td><td>Polymer Source</td><td>P4673A-SAA</td><td>PS16000-PAA3500</td></tr><tr><td>Poly(styrene-&lt;em&gt;b&lt;/em&gt;-acrylic acid) (PS&lt;sub&gt;144&lt;/sub&gt;-PAA&lt;sub&gt;28&lt;/sub&gt;)</td><td>Polymer Source</td><td>P4002-SAA</td><td>PS15000-PAA1600</td></tr><tr><td>2-Naphthalenethiol, &amp;ge;99.0% (GC)</td><td>Sigma-Aldrich</td><td>88910, Fluka</td><td></td></tr><tr><td>Sodium dodecyl sulfate, 99%</td><td>Alfa Aesar</td><td>A11183</td><td></td></tr><tr><td>single wall carbon nanotubes, 99% ultra-pure</td><td>NanoIntegris</td><td>PC10344a</td><td></td></tr><tr><td>Sodium hydroxide</td><td>Sinopharm</td><td>S1900136</td><td></td></tr><tr><td>1,2-dipalmitoyl-&lt;em&gt;sn&lt;/em&gt;-glycero-3-phosphothioethanol (sodium salt)</td><td>Avanti polar lipids</td><td>870160P</td><td>PSH</td></tr><tr><td>&lt;em&gt;N,N&lt;/em&gt;-dimethylformamide</td><td>Merck</td><td>SA4s640012</td><td></td></tr><tr><td>Ethanol, absolute</td><td>Fischer</td><td>E/0650DF/17</td><td></td></tr><tr><td>Hydrochloric acid, 37%</td><td>Honey well</td><td>10189005</td><td>Dilute to 1&amp;nbsp;M before use</td></tr></tbody></table>

using polystyrene-block-poly(acrylic acid)-coated metal nanoparticles as monomers for their homo- and co-polymerization

We present a template-free method for &#8220;polymerizing&#8221; nanoparticles into long chains without side branches. A variety of nanoparticles are encapsulated in polystyrene-block-poly(acrylic acid) (PSPAA) shells and then used as monomers for their self-assembly. Spherical PSPAA micelles upon acid treatment are known to assemble into cylindrical micelles. Exploiting this tendency, the core-shell nanoparticles are induced to aggregate, coalesce, and then transform into long chains. When more than one type of nanoparticles are used, random and block &#8220;copolymers&#8221; of nanoparticles can be obtained. Detailed procedures are reported for the PSPAA encapsulation of nanoparticles, homo- and co-polymerization of the core-shell nanoparticles, separation and purification of the resulting nanoparticle chains. Transformations of single-line chains into double- and triple-line chains are also presented. The synergy between the polymer shell and the embedded nanoparticles leads to an unusual chain-growth polymerization mode, giving long nanoparticle chains that are distinct from the products of the traditional step-growth aggregation process.

The nanoparticle monomers and chains are characterized by TEM. Figure 1 shows the representative TEM images of the PSPAA encapsulated monomers, confirming the morphologies and sizes (Figure 1). As some monomers typically remain in the sample after the &#8220;polymerization&#8221;, the sample is usually purified and concentrated before being used for TEM characterization. A stain was introduced during the preparation of the TEM samples by mixing the sample solution with 1% ammonium molybdate, in order to render the polymer shell with clear contrast in the TEM images. The representative TEM images of the &#8220;homo-polymers&#8220; and &#8220;co-polymers&#8221; are presented in Figure 2 and Figure 3.
<img alt="Figure 1" src="/files/ftp_upload/52954/52954fig1.jpg" /> 
Figure 1. TEM images of the monomers.&#160;(A) 16 nm AuNP@PS154-b-PAA49, (B) 32 nm AuNP@PS144-b-PAA22, (C) AuNR@PS154-b-PAA49, (D) TeNW@PS154-b-PAA49, (E) CNT@PS154-b-PAA49 and (F) PS154-b-PAA49 micelles. <a href="https://www-jove-com.remotexs.ntu.edu.sg/files/ftp_upload/52954/52954fig1highres.jpg" target="_blank">Please click here to view a larger version of this figure.</a>
<img alt="Figure 2" src="/files/ftp_upload/52954/52954fig2.jpg" /> 
Figure 2. TEM images of the &#8220;homo-polymers&#8221; of nanoparticles.&#160;(A) Single-line chains of 16 nm AuNP encapsulated in PS154-b-PAA49, (B) single-line chains of 32 nm AuNPs encapsulated in PS144-b-PAA22, (C) double-line chains of 16 nm AuNPs encapsulated in PS154-b-PAA49 and (D) single-line chains of AuNR@PS154-b-PAA49. <a href="https://www-jove-com.remotexs.ntu.edu.sg/files/ftp_upload/52954/52954fig2highres.jpg" target="_blank">Please click here to view a larger version of this figure.</a>
<img alt="Figure 3" src="/files/ftp_upload/52954/52954fig3.jpg" /> 
Figure 3. TEM images of &#8220;co-polymers&#8221; of nanoparticles.&#160;(A) random chains of 16 nm AuNP encapsulated in PS154-b-PAA49 and 32 nm AuNP encapsulated in PS144-b-PAA22, (B) random chains of 16 nm AuNP encapsulated in PS154-b-PAA49 and AuNR@PS154-b-PAA49, (C) random chains of 16 nm AuNP encapsulated in PS154-b-PAA49 and PS154-b-PAA49 micelles, (D) random chains of 16 nm AuNP encapsulated in PS154-b-PAA49 and PS154-b-PAA49 vesicles, (E) block chains of CNT@PS154-b-PAA49&#160;and 16 nm AuNP encapsulated in PS154-b-PAA49.&#160; (F) block chains of TeNW@PS154-b-PAA49&#160;and 16 nm AuNP encapsulated in PS154-b-PAA49. <a href="https://www-jove-com.remotexs.ntu.edu.sg/files/ftp_upload/52954/52954fig3highres.jpg" target="_blank">Please click here to view a larger version of this figure.</a>

Watch this Scientific Journal Video about Using Polystyrene-block-polyacrylic acid-coated Metal Nanoparticles as Monomers for Their Homo- and Co-polymerization at JoVE.com

Using Polystyrene-block-polyacrylic acid-coated Metal Nanoparticles as Monomers for Their Homo- and Co-polymerization

We report protocols for &#8220;polymerizing&#8221; various types of polymer-encapsulated metal nanoparticles into long chains of &#8220;homo-&#8220; and &#8220;co-polymers&#8221;.

Using Polystyrene-block-poly(acrylic acid)-coated Metal Nanoparticles as Monomers for Their Homo- and Co-polymerization

We present a template-free method for &#8220;polymerizing&#8221; nanoparticles into long chains without side branches. A variety of nanoparticles are ...

using-polystyrene-block-poly-acrylic-acid-coated-metal-nanoparticles

Nanyang Technological University

Research

JoVE Journal

Chemistry

12.1K Views.  Nanyang Technological University. We report protocols for “polymerizing” various types of polymer-encapsulated metal nanoparticles into long chains of “homo-“ and “co-polymers”. 

Video: Using Polystyrene-block-polyacrylic acid-coated Metal Nanoparticles as Monomers for Their Homo- and Co-polymerization

Gyroid Nickel Nanostructures from Diblock Copolymer Supramolecules

Nanoporous metal foams possess a unique combination of properties - they are catalytically active, thermally and electrically conductive, and furthermore, have high porosity, high surface-to-volume and strength-to-weight ratio. Unfortunately, common approaches for preparation of metallic nanostructures render materials with highly disordered architecture, which might have an adverse effect on their mechanical properties. Block copolymers have the ability to self-assemble into ordered nanostructures and can be applied as templates for the preparation of well-ordered metal nanofoams. Here we describe the application of a block copolymer-based supramolecular complex - polystyrene-block-poly(4-vinylpyridine)(pentadecylphenol) PS-b-P4VP(PDP) - as a precursor for well-ordered nickel nanofoam. The supramolecular complexes exhibit a phase behavior similar to conventional block copolymers and can self-assemble into the bicontinuous gyroid morphology with two PS networks placed in a P4VP(PDP) matrix. PDP can be dissolved in ethanol leading to the formation of a porous structure that can be backfilled with metal. Using electroless plating technique, nickel can be inserted into the template&#39;s channels. Finally, the remaining polymer can be removed via pyrolysis from the polymer/inorganic nanohybrid resulting in nanoporous nickel foam with inverse gyroid morphology.

This article describes the preparation of well-ordered nickel nanofoams via electroless metal deposition onto nanoporous templates obtained from self-assembled diblock copolymer based supramolecules.

Nanoporous metal foams possess a unique combination of properties - they are catalytically active, thermally and electrically conductive, and furthermore, ...

Formulation of Diblock Polymeric Nanoparticles through Nanoprecipitation Technique

Nanotechnology is a relatively new branch of science that involves harnessing the unique properties of particles that are nanometers in scale (nanoparticles). Nanoparticles can be engineered in a precise fashion where their size, composition and surface chemistry can be carefully controlled. This enables unprecedented freedom to modify some of the fundamental properties of their cargo, such as solubility, diffusivity, biodistribution, release characteristics and immunogenicity. Since their inception, nanoparticles have been utilized in many areas of science and medicine, including drug delivery, imaging, and cell biology1-4. However, it has not been fully utilized outside of "nanotechnology laboratories" due to perceived technical barrier. In this article, we describe a simple method to synthesize a polymer based nanoparticle platform that has a wide range of potential applications. 
The first step is to synthesize a diblock co-polymer that has both a hydrophobic domain and hydrophilic domain. Using PLGA and PEG as model polymers, we described a conjugation reaction using EDC/NHS chemistry5 (Fig 1). We also discuss the polymer purification process. The synthesized diblock co-polymer can self-assemble into nanoparticles in the nanoprecipitation process through hydrophobic-hydrophilic interactions.
The described polymer nanoparticle is very versatile. The hydrophobic core of the nanoparticle can be utilized to carry poorly soluble drugs for drug delivery experiments6. Furthermore, the nanoparticles can overcome the problem of toxic solvents for poorly soluble molecular biology reagents, such as wortmannin, which requires a solvent like DMSO. However, DMSO can be toxic to cells and interfere with the experiment. These poorly soluble drugs and reagents can be effectively delivered using polymer nanoparticles with minimal toxicity. Polymer nanoparticles can also be loaded with fluorescent dye and utilized for intracellular trafficking studies. Lastly, these polymer nanoparticles can be conjugated to targeting ligands through surface PEG. Such targeted nanoparticles can be utilized to label specific epitopes on or in cells7-10.

This article describes a nanoprecipitation method to synthesize polymer-based nanoparticles using diblock co-polymers. We will discuss the synthesis of diblock co-polymers, the nanoprecipitation technique, and potential applications.

Nanotechnology is a relatively new branch of science that involves harnessing the unique properties of particles that are nanometers in scale ...

Bioengineering

Polymer Microarrays for High Throughput Discovery of Biomaterials

The discovery of novel biomaterials that are optimized for a specific biological application is readily achieved using polymer microarrays, which allows a combinatorial library of materials to be screened in a parallel, high throughput format1. Herein is described the formation and characterization of a polymer microarray using an on-chip photopolymerization technique 2. This involves mixing monomers at varied ratios to produce a library of monomer solutions, transferring the solution to a glass slide format using a robotic printing device and curing with UV irradiation. This format is readily amenable to many biological assays, including stem cell attachment and proliferation, cell sorting and low bacterial adhesion, allowing the ready identification of 'hit' materials that fulfill a specific biological criterion3-5. Furthermore, the use of high throughput surface characterization (HTSC) allows the biological performance to be correlated with physio-chemical properties, hence elucidating the biological-material interaction6. HTSC makes use of water contact angle (WCA) measurements, atomic force microscopy (AFM), X-ray photoelectron spectroscopy (XPS) and time-of-flight secondary ion mass spectrometry (ToF-SIMS). In particular, ToF-SIMS provides a chemically rich analysis of the sample that can be used to correlate the cell response with a molecular moiety. In some cases, the biological performance can be predicted from the ToF-SIMS spectra, demonstrating the chemical dependence of a biological-material interaction, and informing the development of hit materials5,3.

A description of the formation of a polymer microarray using an on-chip photopolymerization technique. The high throughput surface characterization using atomic force microscopy, water contact angle measurements, X-ray photoelectron spectroscopy and time of flight secondary ion mass spectrometry and a cell attachment assay is also described.

The discovery of novel biomaterials that are optimized for a specific biological application is readily achieved using polymer microarrays, which allows a ...

Facile Synthesis of Worm-like Micelles by Visible Light Mediated Dispersion Polymerization Using Photoredox Catalyst

Presented herein is a protocol for the facile synthesis of worm-like micelles by visible light mediated dispersion polymerization. This approach begins with the synthesis of a hydrophilic poly(oligo(ethylene glycol) methyl ether methacrylate) (POEGMA) homopolymer using reversible addition-fragmentation chain-transfer (RAFT) polymerization. Under mild visible light irradiation (&#955; = 460 nm, 0.7 mW/cm2), this macro-chain transfer agent (macro-CTA) in the presence of a ruthenium based photoredox catalyst, Ru(bpy)3Cl2 can be chain extended with a second monomer to form a well-defined block copolymer in a process known as Photoinduced Electron Transfer RAFT (PET-RAFT). When PET-RAFT is used to chain extend POEGMA with benzyl methacrylate (BzMA) in ethanol (EtOH), polymeric nanoparticles with different morphologies are formed in situ according to a polymerization-induced self-assembly (PISA) mechanism. Self-assembly into nanoparticles presenting POEGMA chains at the corona and poly(benzyl methacrylate) (PBzMA) chains in the core occurs in situ due to the growing insolubility of the PBzMA block in ethanol. Interestingly, the formation of highly pure worm-like micelles can be readily monitored by observing the onset of a highly viscous gel in situ due to nanoparticle entanglements occurring during the polymerization. This process thereby allows for a more reproducible synthesis of worm-like micelles simply by monitoring the solution viscosity during the course of the polymerization. In addition, the light stimulus can be intermittently applied in an ON/OFF manner demonstrating temporal control over the nanoparticle morphology.

This article describes a process for producing polymeric self-assembled nanoparticles using visible light mediated dispersion polymerization. Using low energy visible light to control the polymerization allows for the reproducible formation of self-assembled worm-like micelles at high solids content.

Presented herein is a protocol for the facile synthesis of worm-like micelles by visible light mediated dispersion polymerization. This approach begins ...

Anionic Polymerization of an Amphiphilic Copolymer for Preparation of Block Copolymer Micelles Stabilized by &#960;-&#960; Stacking Interactions

In this study, an amphiphilic copolymer that includes a core-forming block with phenyl groups was synthesized by living anionic polymerization of phenyl glycidyl ether (PheGE) on methoxy-polyethylene glycol (mPEG-b-PPheGE). Characterization of the copolymer revealed a narrow molecular distribution (PDI &#60; 1.03) and confirmed the degree of polymerization of mPEG122-b-(PheGE)15. The critical micelle concentration of the copolymer was evaluated using an established fluorescence method with the aggregation behavior evaluated by dynamic light scattering and transmission electronic microscopy. The potential of the copolymer for use in drug delivery applications was evaluated in a preliminary manner including in vitro biocompatibility, loading and release of the hydrophobic anti-cancer drug doxorubicin (DOX). A stable micelle formulation of DOX was prepared with drug loading levels up to 14% (wt%), drug loading efficiencies &#62; 60% (w/w) and sustained release of drug over 4 days under physiologically relevant conditions (acidic and neutral pH, presence of albumin). The high drug loading level and sustained release is attributed to stabilizing &#960;-&#960; interactions between DOX and the core-forming block of the micelles.

The key steps of living anionic polymerization of phenyl glycidyl ether (PheGE) on methoxy-polyethylene glycol (mPEG-b-PPheGE) are described. The resulting block copolymer micelles (BCMs) were loaded with doxorubicin 14% (wt%) and sustained release of drug over 4 days under physiologically relevant conditions was obtained.

In this study, an amphiphilic copolymer that includes a core-forming block with phenyl groups was synthesized by living anionic polymerization of phenyl ...

Grafting Multiwalled Carbon Nanotubes with Polystyrene to Enable Self-Assembly and Anisotropic Patchiness

We demonstrate a straightforward protocol to graft pristine multiwalled carbon nanotubes (MWCNTs) with polystyrene (PS) chains at the sidewalls through a free-radical polymerization strategy to enable the modulation of the nanotube surface properties and produce supramolecular self-assembly of the nanostructures. First, a selective hydroxylation of the pristine nanotubes through a biphasic catalytically mediated oxidation reaction creates superficially distributed reactive sites at the sidewalls. The latter reactive sites are subsequently modified with methacrylic moieties using a silylated methacrylic precursor to create polymerizable sites. Those polymerizable groups can address further polymerization of styrene to produce a hybrid nanomaterial containing PS chains grafted to the nanotube sidewalls. The polymer-graft content, amount of silylated methacrylic moieties introduced and hydroxylation modification of the nanotubes are identified and quantified by Thermogravimetric Analysis (TGA). The presence of reactive functional groups hydroxyl and silylated methacrylate are confirmed by Fourier Transform Infrared Spectroscopy (FT-IR). Polystyrene-grafted carbon nanotube solutions in tetrahydrofuran (THF) provide wall-to-wall collinearly self-assembled nanotubes when cast samples are analyzed by transmission electron microscopy (TEM). Those self-assemblies are not obtained when suitable blanks are similarly cast from analogous solutions containing non-grafted counterparts. Therefore, this method enables the modification of the nanotube anisotropic patchiness at the sidewalls which results into spontaneous auto-organization at the nanoscale.

A procedure for the synthesis of polystyrene-grafted multiwalled carbon nanotubes using successive chemical modification steps to selectively introduce the polymer chains to the sidewalls and their self-assembly via anisotropic patchiness is presented.

We demonstrate a straightforward protocol to graft pristine multiwalled carbon nanotubes (MWCNTs) with polystyrene (PS) chains at the sidewalls through a ...

Preparation of Hollow Polystyrene Particles and Microcapsules by Radical Polymerization of Janus Droplets Consisting of Hydrocarbon and Fluorocarbon Oils

In this article, we have demonstrated a method for producing hollow particles and microcapsules using oil droplets consisting of hydrocarbon oil (styrene) and fluorocarbon oil (perfluoro-n-octane, PFO) in aqueous surfactant (sodium dodecylsulfate, SDS) solutions. Since fluorocarbon oils are immiscible with hydrocarbon oils, the two oils are separated. Emulsions are prepared by stirring styrene/PFO/aqueous SDS solution mixtures at 80 &#176;C. The type of emulsions and the morphology of droplets in the emulsions are observed by light microscope and scanning confocal fluorescence microscope. It is found that oil droplets with Janus-type morphologies consisting of mutually immiscible styrene and PFO are formed in aqueous SDS solutions. Polystyrene particles are fabricated by radical polymerization of the ternary mixtures of styrene/PFO/aqueous SDS solution at 80 &#176;C. The morphologies of the polystyrene are confirmed by scanning electron microscopy and scanning transmission electron microscopy observations. These observations show the preparation of hollow polystyrene particles with a single hole on the surface. To our knowledge, this method is a novel strategy using the immiscibility of hydrocarbon and fluorocarbon oils. The hollow particles can also be applied to the preparation of microcapsules.

A protocol for the fabrication of hollow polymer particles and microcapsules by radical polymerization using emulsions consisting of styrene, perfluoro-n-octane, and aqueous SDS (sodium dodecylsulfate) solution is presented.

In this article, we have demonstrated a method for producing hollow particles and microcapsules using oil droplets consisting of hydrocarbon oil (styrene) ...

Synthesis of Monodisperse Cylindrical Nanoparticles via Crystallization-driven Self-assembly of Biodegradable Block Copolymers

The production of monodisperse cylindrical micelles is a significant challenge in polymer chemistry. Most cylindrical constructs formed from diblock copolymers are produced by one of three techniques: thin film rehydration, solvent switching or polymerization-induced self-assembly, and produce only flexible, polydisperse cylinders. Crystallization-driven self-assembly (CDSA) is a method which can produce cylinders with these properties, by stabilizing structures of a lower curvature due to the formation of a crystalline core. However, the living polymerization techniques by which most core-forming blocks are formed are not trivial processes and the CDSA process may yield unsatisfactory results if carried out incorrectly. Here, the synthesis of cylindrical nanoparticles from simple reagents is shown. The drying and purification of reagents prior to a ring-opening polymerization of &#949;-caprolactone catalyzed by diphenyl phosphate is described. This polymer is then chain extended by methyl methacrylate (MMA) followed by N,N-dimethyl acrylamide (DMA) using reversible addition&#8722;fragmentation chain-transfer (RAFT) polymerization, affording a triblock copolymer that can undergo CDSA in ethanol. The living CDSA process is outlined, the results of which yield cylindrical nanoparticles up to 500 nm in length and a length dispersity as low as 1.05. It is anticipated that these protocols will allow others to produce cylindrical nanostructures and elevate the field of CDSA in the future.

Crystallization-driven self-assembly (CDSA) displays the unique ability to fabricate cylindrical nanostructures of narrow length distributions. The organocatalyzed ring-opening polymerization of &#949;-caprolactone and subsequent chain extensions of methyl methacrylate and N,N-dimethyl acrylamide are demonstrated. A living CDSA protocol that produces monodisperse cylinders up to 500 nm in length is outlined.

The production of monodisperse cylindrical micelles is a significant challenge in polymer chemistry. Most cylindrical constructs formed from diblock ...

Self-Assembly of Polymer-Grafted Metal Organic Framework Monolayers

Synthesis and Characterization of Self-Assembled Metal-Organic Framework Monolayers Using Polymer-Coated Particles

Metal-organic frameworks (MOFs) are materials with potential applications in fields such as gas adsorption and separation, catalysis, and biomedicine. Attempts to enhance the utility of MOFs have involved the preparation of various composites, including polymer-grafted MOFs. By directly grafting polymers to the external surface of MOFs, issues of incompatibility between polymers and MOFs can be overcome. Polymer brushes grafted from the surface of MOFs can serve to stabilize the MOF while enabling particle assembly into self-assembled metal-organic framework monolayers (SAMMs) via polymer-polymer interactions.
Control over the chemical composition and molecular weight of the grafted polymer can allow for tuning of the SAMM characteristics. In this work, instructions are provided on how to immobilize a chain transfer agent (CTA) onto the surface of the MOF UiO-66 (UiO = Universitetet i Oslo). The CTA&#160;serves as initiation sites for the growth of polymers. Once polymer chains are grown from the MOF surface, the formation of SAMMs is achieved through self-assembly at an air-water interface. The resulting SAMMs are characterized and shown to be freestanding by scanning electron microscopy imaging. The methods presented in this paper are expected to make the preparation of SAMMs more accessible to the research community and thereby expand their potential use as a&#160;MOF-polymer composite.

Author Spotlight: Exploring Self-Assembled MOF-Polymer Composites

A protocol for the synthesis and characterization of self-assembled metal-organic framework monolayers is provided using polymer-grafted, metal-organic framework (MOF) crystals. The procedure shows that polymer-grafted MOF particles can be self-assembled at an air-water interface resulting in well-formed, free-standing, monolayer structures as evidenced by scanning electron microscopy imaging.

Metal-organic frameworks (MOFs) are materials with potential applications in fields such as gas adsorption and separation, catalysis, and biomedicine. ...

Polymerization

Source: Vy M. Dong and Jan Riedel, Department of Chemistry, University of California, Irvine, CA
Polymers are made from macromolecules, which are composed of repeating units (the so called monomeric units). In our modern world, polymers play an important role. One of the first important polymers was nylon, which is a polyamide. It found widespread application in tooth brushes and stockings.

Polymerization: Types of Polymerizations and Applications

Source: Vy M. Dong and Jan Riedel, Department of Chemistry, University of California, Irvine, CA
Polymers are made from macromolecules, which are composed ...

Using Polystyrene-block-poly(acrylic acid)-coated Metal Nanoparticles as Monomers for Their Homo- and Co-polymerization

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