The authors gratefully acknowledge the National Science Foundation (DMR-1409034) for support of this project. We also acknowledge the support of the National Institute of Standards and Technology, U.S. Department of Commerce, in providing the USANS facilities used in this work, where these facilities are supported in part by the National Science Foundation under Agreement No. DMR-0944772. The SANS experiments of this research were completed at ORNL&#39;s High Flux Isotope Reactor, which was sponsored by the Scientific User Facilities Division, Office of Basic Energy Sciences, US Department of Energy.

All handling of chemicals should be carried out with proper personal protective equipment and within a safety hood. All samples exposed to ionizing radiation should be handled under the supervision of the facilities radioactive control technicians. This protocol was performed by individuals who had completed appropriate radiation safety training.
1. Preparation of P3HT in d-ODCB Solutions
<ol>
	<li>Sample Acquisition
	<ol>
		<li>Purchase 1 g of high regioregularity (&#62;90%) P3HT in the molecular weight range 15 - 40 K.</li>
		<li>Purchase 5 g of high purity (&#62;90 atom% deuterated) d-4 1,2-ODCB.</li>
	</ol>
	</li>
	<li>Sample Preparation
	<ol>
		<li>Filter all d-ODCB solution with 0.45 &#181;m sieve into a glass vial.</li>
		<li>Combine 0.34 g of P3HT in 1.66 g of d-ODCB in a 5 g glass vial with foil lined cap. 
		NOTE: Throughout the sample creation and transfer process, minimize the ambient light intensity to which the sample is exposed at all times.</li>
		<li>Add a magnetic stir bar to the vial, secure the cap, and seal with parafilm.</li>
		<li>Wrap vial entirely in aluminum foil to prevent any light exposure to solution.</li>
		<li>Place sample on hot plate at 70 &#176;C for 1 - 3 h with the magnetic stir bar enabled.</li>
		<li>Remove from heat and stirring once solution is completely homogeneous (preferably leaving the sample heating/stirring overnight to ensure complete dispersion).</li>
		<li>Transfer solution from vial to a properly cleaned (with separate rinses of acetone and water) 1 or 2 mm thick quartz banjo cell using a glass pipette. 
		NOTE: Heating the glass pipette in a heating oven to 70 &#176;C immediately before transfer greatly simplifies this process.</li>
		<li>Affix banjo cell cap and seal with parafilm.</li>
		<li>Place banjo cell in complete darkness (i.e. inside a sealed box or wrapped in aluminum foil).</li>
		<li>In a similar fashion assemble a sample which contains only d-ODCB (filled to capacity) and an empty banjo cell, to act as the solvent background and empty cell, respectively, for the scattering experiments.</li>
	</ol>
	</li>
</ol>
2. Neutron Scattering Experiments
<ol>
	<li>SANS Experiments in the &#34;dark&#34; environment
	<ol>
		<li>With assistance from the&#160;instrument scientist, ensure a sample stage is affixed with the required temperature controls capable of directing a temperature ramp from 70 -&#160;20 &#176;C.</li>
		<li>Place the banjo cells in the appropriately sized holding blocks, secure, and label.</li>
		<li>Wrap entire block with 0.1 mm thick aluminum foil to ensure no ambient light is incident to the sample. Minimize deformations of the foil to ensure proper fitting of the wrapped block in the sample stage. Place this wrapped block and sample within the sample stage.</li>
		<li>With&#160;assistance from&#160;the instrument scientist, complete the proper instrument alignment and calibration using the appropriate standard measurements. Set the detector distance close to its maximum setting (for instance at 18 m) to ensure access to the lowest Q region (~0.001 &#197;-1), ultimately allowing a full Q range of roughly 0.001-0.1 &#197;-1. This will allow probing of length scales up to ~500 nm.</li>
		<li>With the assistance of the instrument scientist, collect count rates for the P3HT and solvent samples and perform calculations to determine the amount of scattering time required to achieve total detector counts per sample of roughly 500,000 to 1,000,000, ensuring good statistical quality in the data.</li>
		<li>With this information, create a sample script which will direct the 70-20 &#176;C temperature ramp and data collection process. Choose a range of discrete temperature points to best cover the entire range within the given time restraints, for instance every 2 &#176;C. For every point on the ramp make 3 separate entries in the script: a change to the desired temperature, a wait period (~15 minutes) to allow the system to thermally equilibrate before scattering is collected, and the scattering measurement itself conducted over the appropriate time duration to achieve the required detector counts</li>
		<li>Once the instrument and script are prepared, execute the script and begin the experiment. Be sure to collect data for the solvent and empty cell as well (without temperature ramp). Additionally, collect transmission data for each sample and a blocked beam measurement.</li>
	</ol>
	</li>
	<li>SANS Experiments in the &#34;light&#34; environment
	<ol>
		<li>Upon completion of the &#34;dark&#34; experiment, move the samples from the stage, place on a secure benchtop, and remove all aluminum foil while observing radiation safety protocols.</li>
		<li>Position an optical illuminator featuring a halogen light source near the sample stage such that the leads effectively illuminate the sample slot in the stage associated with the scattering collection position.</li>
		<li>Using a calibrated light meter, record the light intensity provided by the illuminator at maximum intensity at the position where the sample will sit. Intensity values will vary with illuminator and sample stage configuration, however, illumination intensity of at least 5,000 lux is desired.</li>
		<li>Once this illumination setup is properly assembled, return the samples to the stage, ensure the illuminator is properly lighting the active sample, heat again to 70 &#176;C, allow proper equilibration, and repeat&#160;the data collection procedure performed on the dark samples, with the optical illuminator providing uninterrupted direct light exposure thorough the entire duration of this step.</li>
	</ol>
	</li>
	<li>USANS Experiments
	<ol>
		<li>Prepare USANS samples in a similar fashion using quartz banjo cells and place in copper or titanium blocks within a temperature controlled sample stage.</li>
		<li>With the help of the instrument scientist, align and calibrate the instrument employing the requisite number of buffers at the given neutron wavelength to allow analysis of Q values from roughly 10-5 -&#160;10-3 &#197;-1, allowing&#160;length scales on the order of microns to be probed.</li>
		<li>Develop the experimental script in a similar fashion to the SANS experiments, allowing for thermal equilibration and data collection at each temperature studied previously.</li>
		<li>Replicate the SANS experiments again, execute the script once under &#34;dark&#34; conditions and again under &#34;&#34;light&#34; conditions.</li>
	</ol>
	</li>
</ol>
3. Data Reduction and Analysis
<ol>
	<li>SANS reduction and analysis
	<ol>
		<li>Using the respective reduction program,32 input the data files for scattering, background (solvent), empty cell, blocked beam, and transmission measurements to accomplish proper background subtraction and conversion of scattering data to absolute units of intensity in cm-1.</li>
		<li>With the data appropriately reduced, begin analysis by fitting the experimental scattering data to a model that is the linear addition of two fitting equations, one representing the nanofibril aggregates through the elliptical cylinder model,33 and another taking into account the free chains in solution through the polymer excluded volume model.34,35 The equation below describes this combination model approach: 
		<img alt="Equation 1" src="/files/ftp_upload/56163/56163eq1.jpg" /> 
		In this equation, &#981;P3HT describes the total volume fraction of P3HT in the solution, <img alt="Equation 2" src="/files/ftp_upload/56163/56163eq2.jpg" /> is the volume fraction of aggregated P3HT present and modeled as an elliptical cylinder, PPEV is the free chain excluded volume form factor for P3HT, PECM describes the elliptical cylinder form factor for the aggregates, and <img alt="Equation 3" src="/files/ftp_upload/56163/56163eq3.jpg" /> and <img alt="Equation 4" src="/files/ftp_upload/56163/56163eq4.jpg" /> are the scattering length density (SLD) contrast between P3HT aggregates and the solvent and between the free P3HT chains and the solvent, respectively. SLD values for all components of the system can be calculated with a knowledge of their chemical composition and mass density and the use of an SLD calculator available as part of most neutron analysis programs or online.36</li>
		<li>Upon proper fitting procedures using NCNR Igor fitting macros37 or the SASView fitting program, acquire values for the key structural parameters for the gelled system at all temperatures in the light and dark, allowing quantification of the morphological evolution occurring throughout this process as a function of temperature and light exposure. These structural parameters include the cross-sectional areas of the nanofibrils, free chain radius of gyration (Rg) and Porod exponent, and a qualitative assessment of the total amount of material present in the nanofibril phase.</li>
	</ol>
	</li>
	<li>USANS reduction and analysis
	<ol>
		<li>Using the respective reduction program, input the scattering data and background data for each buffer to merge the data into a single reduced curve in absolute intensity units of cm-1.</li>
		<li>Analyze the data using a Guinier-Porod power law model which allows quantitative assessment of the aggregate scattering patterns probed by the USANS length scale, and allows acquisition of the aggregate Rg values.38 Fit using this method through NCNR Igor fitting macros37 or the SASView fitting program to allow comparison of macro-aggregate Rg across all temperatures and illumination conditions.</li>
	</ol>
	</li>
</ol>

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Crystallogr. 39 (6), 895-900 (2006).</li><li>Guinier, A., Fournet, G. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=.">.</a> Small-Angle Scattering of X-Rays. , (1955).</li></ol>

The authors have nothing to disclose.

First, looking at the SANS data as a function of temperature, the increase in the Elliptical Cylinder Model scale factor indicates a marked increase in the amount of P3HT present in the nanofibril phase, which isconsistent with the progression of the gelation process. Simultaneously, the decrease in free chain Rg paired with an increase in Porod exponent reveals that the deteriorating thermodynamic conditions associated with temperature decrease are causing a chain collapse in the P3HT chains still present in solution. These results, combined with the USANS data showing a marked increase in macroaggregate Rg upon temperature decrease, indicate that the scattering experiments have effectively captured and analyzed the progression of the structural self-assembly process central to the sol-gel transition, a process that is visualized in Figure 6. Analyzing the results of these experiments as a function of light exposure provides further information related to the effect of illumination on the gelation process and the ultimate aggregate structures formed. Comparison of all SANS parameters in Figure 2 reveals differences between the light and dark samples over a range of temperatures, as does the USANS data in Figure 3. Taken together, this information indicates that light exposure effectively hinders the P3HT aggregation process, resulting in less material aggregating in the nanofibril phase (indicated by the ECM scale factor results) and smaller micron scale aggregates (given by the USANS Rg values). Thus, this experiment has also emphasized the differences between conjugated polymer gelation conducted in the light versus the dark and underlined the importance of illumination conditions upon the device-relevant active layer morphologies which are formed.
When considering a similar experimental approach to the above method it is important to keep in mind the limitations inherent to the system. Neutron scattering is a powerful technique for analyzing angstrom to nanometer scale structures in polymer systems, however, length scales that lie above or below this range are better probed by other techniques. Additionally, if one of the components of the polymer system of interest are not easily deuterated, it can be difficult to achieve the level of contrast necessary for acceptable results. Also, given the limited amount of neutron beam time, experiments must be carefully planned with a relatively concentrated focus. It is also important to have an appropriate robust fitting model pre-determined before the experiments begin to narrow the scope of the analysis process and ensure proper modeling of the system.
Assuming that an experiment meets these conditions, these neutron scattering methods offer a unique tool to unobtrusively monitor the structural evolution of polymer systems over a range of length scales as a function of multiple environmental stimuli, such as temperature and light exposure. Harnessing these approaches could allow for the expansion of these methods to a huge variety of polymer-solvent systems to explore structural changes occurring due to changes in a variety of conditions including (but not limited to) polymer concentration, solvent quality, dopant addition, and thermal history.

Conjugated polymers promise functional materials that can be utilized in a broad range of devices, such as organic light emitting diodes, organic semiconductors, chemical sensors, and organic photovoltaics.1,2,3,4,5,6 A crucial aspect of the performance in these devices is the ordering and packing of the conjugated polymer in the solid state in the active layer.7,8,9,10,11,12,13,14 This morphology is&#160;largely&#160;pre-determined by both the conformation of the polymer chain in solution as well as the structures that&#160;evolve as these solutions are cast unto a substrate and the solvent is removed. By studying the structures present throughout a typical sol-gel transition of a model optoelectronic polymer in a suitable solvent, these systems can be effectively modeled and a quantitative glimpse into the self-assembly that occurs during material deposition can be obtained.15,16,17,18,19,20
Specifically, we examine the conjugated polymer benchmark P3HT in the solvent deuterated ortho-dichlorobenzene (ODCB), a polymer-solvent system which has seen extensive use due to its suitability for a variety of organic electronic device fabrication techniques.23,24,25 In this given solvent environment, P3HT chains begin to aggregate upon an appropriate environmental stimuli, such as temperature decrease or loss of solvent quality. The exact mechanism for this assembly process is under investigation, with one of the leading proposed pathways believed to be a gradual process where individual P3HT molecules &#960;-stack to form lamellar nano-aggregates known as nanofibrils, which then themselves agglomerate to form larger micron scale macro-aggregates.24 Understanding these pathways and the resultant structures formed is&#160;key to properly predicting and influencing the formation of optimal device active layer morphologies.
Towards this ultimate goal of more precisely directing the formation of these active layer architectures, there exists a need to develop additional experimental and industrial methods to non-destructively alter conjugated polymer morphology in-situ. One relatively new methodology centers around the use of light exposure as an inexpensive means for altering polymer chain morphology, with both computational and experimental results pointing towards its feasibility.25,26,27 Recent work by our laboratory has indicated the existence of a light induced alteration of the conjugated polymer-solvent interaction in a dilute solution, leading to a notable change in polymer chain size upon illumination.30,31 Here, we present a protocol to continue this work by effectively monitoring the effects of exposing a much more concentrated conjugated polymer solution to direct light&#160;throughout a gelation process that is directed by a thermostat-controlled temperature ramp. We employ neutron scattering as it allows robust analysis of structural parameters of the polymer-solvent sol-gel system on length scales from angstroms to microns, an ability not possible through other more common rheological or spectroscopic instrumental methods.16,17,30,31 Thus, by comparing the properly analyzed small and ultra-small angle neutron data for the assembly of gels formed under illumination to identical data collected in complete darkness, structural differences brought on by illumination-driven effects can be comprehensively identified and quantified.

<table border="0" cellpadding="0" cellspacing="0" width="822">
	<tbody>
		<tr height="21">
			<td height="21" style="height:21px;width:353px;">M(106) poly(3-hexylthiophene-2,5-diyl) (P3HT)</td>
			<td style="width:143px;">Ossila</td>
			<td style="width:160px;">104934-50-1</td>
			<td style="width:167px;">Conjugated polymer</td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;">deuterated 1,2 ortho-dichlorobenzene (ODCB)</td>
			<td style="width:143px;">Sigma Aldrich</td>
			<td>AC321260050</td>
			<td>solvent</td>
		</tr>
	</tbody>
</table>

monitoring the effects of illumination on the structure of conjugated polymer gels using neutron scattering

We demonstrate a protocol to effectively monitor the gelation process of a high concentration solution of conjugated polymer both in the presence and absence of white light exposure. By instituting a controlled temperature ramp, the gelation of these materials can be precisely monitored as they proceed through this structural evolution, which effectively mirrors the conditions experienced during the solution deposition phase of organic electronic device fabrication. Using small angle neutron scattering (SANS) and ultra-small angle neutron scattering (USANS) along with appropriate fitting protocols we quantify the evolution of select structural parameters throughout this process. Thorough analysis indicates that continued light exposure throughout the gelation process significantly alters the structure of the ultimately formed gel. Specifically, the aggregation process of poly(3-hexylthiophene-2,5-diyl) (P3HT) nano-scale aggregates is negatively affected by the presence of illumination, ultimately resulting in the retardation of growth in conjugated polymer microstructures and the formation of smaller scale macro-aggregate clusters.

Through SANS and USANS experiments, the gelation process of P3HT in d-ODCB was effectively monitored from the dispersed solution state at 70 &#176;C to a fully gelled state at 20 &#176;C. These experiments were conducted in both complete darkness and under white light illumination. Figure 1 displays some example SANS reduced data curves from these experiments, with an example curve fit shown in Figure 2. From this data, the structural changes occurring as temperature decreases have been effectively captured, denoted by a clear increase in absolute intensity as temperature falls. Additionally, for each given temperature there is a clear discrepancy between the scattering data of the samples studied in the dark and those studied in the light as the data plots do not overlap. This indicates that light exposure significantly affects the aggregation process. Figure 3 displays values for a variety of structural parameters extracted using the combined fit model from the SANS data and provides&#160;structural information on both the nanofibril aggregates and the free chains still in solution. The nanofibril surface area describes the surface area of the face of the cylindrical nano-scale P3HT aggregates and the ECM scale factor gives a qualitative description of the amount of P3HT present in the aggregate phase, while the free chain Rg and Porod exponent describe the size and form factor of the P3HT chains not yet gelled in the solution. Significant differences in these parameters at each given temperature and between light and dark samples at a given temperature indicate that the experiment and fitting process have captured the effect of light exposure on this gelation process. Since they employ a substantially lower Q range, USANS experiments allow the characterization of larger length scales consistent with P3HT macro aggregates, and by mirroring the same approach used in the SANS experiments, the effect of temperature and light upon the size of these aggregates is effectively quantified. Figure 4 shows USANS data plotted alongside the SANS data for a single temperature, and Figure 5 displays the Rg data acquired through fitting USANS data with a power law model. This Rg value grows with decreasing temperature as gelation progresses and individual P3HT nanofibrils themselves aggregate to form large scale microstructures. And as with the SANS data, there exists clear difference between the light and dark data, specifically showing smaller Rg values with light exposure.
<img alt="Figure 1" class="xfigimg" src="/files/ftp_upload/56163/56163fig1.jpg" /> 
Figure 1: Small angle neutron scattering data for a 17 wt% sample of P3HT in d-ODCB through 70-20 &#176;C temperature ramp. Data collected under white light illumination (open symbols) and in complete darkness (closed symbols). Error bars report instrumental error. Reproduced from reference 28 with permission. <a href="https://cloudflare-jove-com.remotexs.ntu.edu.sg/files/ftp_upload/56163/56163fig1large.jpg" target="_blank">Please click here to view a larger version of this figure.</a>
<img alt="Figure 2" class="xfigimg" src="/files/ftp_upload/56163/56163fig2.jpg" /> 
Figure 2: Example fit using a combination model approach incorporating both the Elliptical Cylinder and Polymer Excluded Volume Model to 17 wt% P3HT SANS data collected at 34 &#176;C in the presence of white light illumination. Reproduced from reference 28 with permission. <a href="https://cloudflare-jove-com.remotexs.ntu.edu.sg/files/ftp_upload/56163/56163fig2large.jpg" target="_blank">Please click here to view a larger version of this figure.</a>
<img alt="Figure 3" class="xfigimg" src="/files/ftp_upload/56163/56163fig3.jpg" /> 
Figure 3: Select parameters obtained from the combined model fit for 17 wt% P3HT through a 70 - 20&#176;C temperature ramp, with black traces indicating samples studied in the dark, and red traces indicating samples studied under illumination: (A): nanofibril surface area, (B): Elliptical Cylinder Model scale factor, (C): radius of gyration of free chains, and (D): Porod exponent of free chains. Error bars report fit-generated standard deviation error values. Reproduced from reference 28 with permission. <a href="https://cloudflare-jove-com.remotexs.ntu.edu.sg/files/ftp_upload/56163/56163fig3large.jpg" target="_blank">Please click here to view a larger version of this figure.</a>
<img alt="Figure 4" class="xfigimg" src="/files/ftp_upload/56163/56163fig4.jpg" /> 
Figure 4: Small and ultra-small angle scattering data of 17 wt% P3HT at 24&#176;C for both illuminated (gray) and dark (black) samples. Error bars report instrumental error. Reproduced from reference 28 with permission. <a href="https://cloudflare-jove-com.remotexs.ntu.edu.sg/files/ftp_upload/56163/56163fig4large.jpg" target="_blank">Please click here to view a larger version of this figure.</a>
<img alt="Figure 5" class="xfigimg" src="/files/ftp_upload/56163/56163fig5.jpg" /> 
Figure 5: Radius of gyration values obtained from 17 wt% P3HT USANS data fit with a Guinier-Porod power law model for both illuminated (red) and dark (black) samples. Error bars report fit-generated standard deviation error values. Reproduced from reference 28 with permission.
<img alt="Figure 6" class="xfigimg" src="/files/ftp_upload/56163/56163fig6.jpg" /> 
Figure 6: Illustration of the P3HT assembly process from free chains to final micron-scale aggregates. Reproduced from reference 28 with permission. <a href="https://cloudflare-jove-com.remotexs.ntu.edu.sg/files/ftp_upload/56163/56163fig6large.jpg" target="_blank">Please click here to view a larger version of this figure.</a>

Watch this Scientific Journal Video about Monitoring the Effects of Illumination on the Structure of Conjugated Polymer Gels Using Neutron Scattering at JoVE.com

Monitoring the Effects of Illumination on the Structure of Conjugated Polymer Gels Using Neutron Scattering

A protocol for the analysis of gels formed from the optoelectronic conjugated polymer poly(3-hexylthiophene-2,5-diyl) (P3HT) using small and ultra-small angle neutron scattering in both the presence and absence of illumination is presented.

We demonstrate a protocol to effectively monitor the gelation process of a high concentration solution of conjugated polymer both in the presence and ...

monitoring-effects-illumination-on-structure-conjugated-polymer-gels

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5.6K Views.  University of Tennessee, Knoxville. A protocol for the analysis of gels formed from the optoelectronic conjugated polymer poly(3-hexylthiophene-2,5-diyl) (P3HT) using small and ultra-small angle neutron scattering in both the presence and absence of illumination is presented.

Video: Monitoring the Effects of Illumination on the Structure of Conjugated Polymer Gels Using Neutron Scattering

Structure and Coordination Determination of Peptide-metal Complexes Using 1D and 2D 1H NMR

Copper (I) binding by metallochaperone transport proteins prevents copper oxidation and release of the toxic ions that may participate in harmful redox reactions. The Cu (I) complex of the peptide model of a Cu (I) binding metallochaperone protein, which includes the sequence MTCSGCSRPG (underlined is conserved), was determined in solution under inert conditions by NMR spectroscopy.
NMR is a widely accepted technique for the determination of solution structures of proteins and peptides. Due to difficulty in crystallization to provide single crystals suitable for X-ray crystallography, the NMR technique is extremely valuable, especially as it provides information on the solution state rather than the solid state. Herein we describe all steps that are required for full three-dimensional structure determinations by NMR. The protocol includes sample preparation in an NMR tube, 1D and 2D data collection and processing, peak assignment and integration, molecular mechanics calculations, and structure analysis. Importantly, the analysis was first conducted without any preset metal-ligand bonds, to assure a reliable structure determination in an unbiased manner.

Structure and Coordination Determination of Peptide-metal Complexes Using 1D and 2D 1H NMR

The NMR-solution structure of a metallochaperone model peptide with Cu (I) was determined, and a detailed protocol from sample preparation and 1D and 2D data collection to a three-dimensional structure is described.

Copper (I) binding by metallochaperone transport proteins prevents copper oxidation and release of the toxic ions that may participate in harmful redox ...

Preparation of Highly Porous Coordination Polymer Coatings on Macroporous Polymer Monoliths for Enhanced Enrichment of Phosphopeptides

We describe a protocol for the preparation of hybrid materials based on highly porous coordination polymer coatings on the internal surface of macroporous polymer monoliths. The developed approach is based on the preparation of a macroporous polymer containing carboxylic acid functional groups and the subsequent step-by-step solution-based controlled growth of a layer of a porous coordination polymer on the surface of the pores of the polymer monolith. The prepared metal-organic polymer hybrid has a high specific micropore surface area. The amount of iron(III) sites is enhanced through metal-organic coordination on the surface of the pores of the functional polymer support. The increase of metal sites is related to the number of iterations of the coating process.
The developed preparation scheme is easily adapted to a capillary column format. The functional porous polymer is prepared as a self-contained single-block porous monolith within the capillary, yielding a flow-through separation device with excellent flow permeability and modest back-pressure. The metal-organic polymer hybrid column showed excellent performance for the enrichment of phosphopeptides from digested proteins and their subsequent detection using matrix-assisted laser desorption/ionization time-of-flight mass spectrometry. The presented experimental protocol is highly versatile, and can be easily implemented to different organic polymer supports and coatings with a plethora of porous coordination polymers and metal-organic frameworks for multiple purification and/or separation applications.

A procedure for the preparation of porous hybrid separation media composed of a macroporous polymer monolith internally coated by a high surface area microporous coordination polymer is presented.

We describe a protocol for the preparation of hybrid materials based on highly porous coordination polymer coatings on the internal surface of macroporous ...

Photodynamic Therapy with Blended Conducting Polymer/Fullerene Nanoparticle Photosensitizers

In this article a method for the fabrication and reproducible in-vitro evaluation of conducting polymer nanoparticles blended with fullerene as the next generation photosensitizers for Photodynamic Therapy (PDT) is reported. The nanoparticles are formed by hydrophobic interaction of the semiconducting polymer MEH-PPV (poly[2-methoxy-5-(2-ethylhexyloxy)-1,4-phenylenevinylene]) with the fullerene PCBM (phenyl-C61-butyric acid methyl ester) in the presence of a non-compatible solvent. MEH-PPV has a high extinction coefficient that leads to high rates of triplet formation, and efficient charge and energy transfer to the fullerene PCBM. The latter processes enhance the efficiency of the PDT system through fullerene assisted triplet and radical formation, and ultrafast deactivation of MEH-PPV excited stated. The results reported here show that this nanoparticle PDT sensitizing system is highly effective and shows unexpected specificity to cancer cell lines.

This protocol describes a method for the fabrication of conducting polymer nanoparticles blended with fullerene. These nanoparticles were investigated for their potential use as a next generation photosensitizers for Photodynamic Therapy (PDT).

In this article a method for the fabrication and reproducible in-vitro evaluation of conducting polymer nanoparticles blended with fullerene as the next ...

Layer-by-layer Synthesis and Transfer of Freestanding Conjugated Microporous Polymer Nanomembranes

CMP as large surface area materials have attracted growing interest recently, due to their high variability in the incorporation of functional groups in combination with their outstanding thermal and chemical stability, and low densities. However, their insoluble nature causes problems in their processing since usually applied techniques such as spin coating are not available. Especially for membrane applications, where the processing of CMP as thin films is desirable, the processing problems have hindered their commercial application.
Here we describe the interfacial synthesis of CMP thin films on functionalized substrates via molecular layer-by-layer (l-b-l) synthesis. This process allows the preparation of films with desired thickness and composition and even desired composition gradients.
The use of sacrificial supports allows the preparation of freestanding membranes by dissolution of the support after the synthesis. To handle such ultra-thin freestanding membranes the protection with sacrificial coatings showed great promise, to avoid rupture of the nanomembranes. To transfer the nanomembranes to the desired substrate, the coated membranes are upfloated at the air-liquid interface and then transferred via dip coating.

In this paper we describe the interfacial synthesis of conjugated microporous polymers (CMP) on sacrificial substrates, and the dissolution of the substrate for the preparation of freestanding CMP nanomembranes. In addition, we will describe how the fragile nanomembranes can be transferred to other substrates.

CMP as large surface area materials have attracted growing interest recently, due to their high variability in the incorporation of functional groups in ...

Functionalization of Single-walled Carbon Nanotubes with Thermo-reversible Block Copolymers and Characterization by Small-angle Neutron Scattering

We demonstrate a protocol for single-walled carbon nanotube functionalization using thermo-sensitive PEO-PPO-PEO triblock copolymers in an aqueous solution. In a carbon nanotube/PEO105-PPO70-PEO105 (poloxamer 407) aqueous solution, the amphiphilic poloxamer 407 adsorbs onto the carbon nanotube surfaces and self-assembles into continuous layers, driven by intermolecular interactions between constituent molecules. The addition of 5-methylsalicylic acid changes the self-assembled structure from spherical-micellar to a cylindrical morphology. The fabricated poloxamer 407/carbon nanotube hybrid particles exhibit thermo-responsive structural features so that the density and thickness of poloxamer 407 layers are also reversibly controllable by varying temperature. The detailed structural properties of the poloxamer 407/carbon nanotube particles in suspension can be characterized by small-angle neutron scattering experiments and model fit analyses. The distinct curve shapes of the scattering intensities depending on temperature control or addition of aromatic additives are well described by a modified core-shell cylinder model consisting of a carbon nanotube core cylinder, a hydrophobic shell, and a hydrated polymer layer. This method can provide a simple but efficient way for the fabrication and in-situ characterization of carbon nanotube-based nano particles with a structure-tunable encapsulation.

A method for the functionalization of carbon nanotubes with structure-tunable polymeric encapsulation layers and structural characterization using small-angle neutron scattering is presented.

We demonstrate a protocol for single-walled carbon nanotube functionalization using thermo-sensitive PEO-PPO-PEO triblock copolymers in an aqueous ...

The Preparation and Properties of Thermo-reversibly Cross-linked Rubber Via Diels-Alder Chemistry

A method for using Diels Alder thermo-reversible chemistry as cross-linking tool for rubber products is demonstrated. In this work, a commercial ethylene-propylene rubber, grafted with maleic anhydride, is thermo-reversibly cross-linked in two steps. The pending anhydride moieties are first modified with furfurylamine to graft furan groups to the rubber backbone. These pendant furan groups are then cross-linked with a bis-maleimide via a Diels-Alder coupling reaction. Both reactions can be performed under a broad range of experimental conditions and can easily be applied on a large scale. The material properties of the resulting Diels-Alder cross-linked rubbers are similar to a peroxide-cured ethylene/propylene/diene rubber (EPDM) reference. The cross-links break at elevated temperatures (&#62; 150 &#176;C) via the retro-Diels-Alder reaction and can be reformed by thermal annealing at lower temperatures (50-70 &#176;C). Reversibility of the system was proven with infrared spectroscopy, solubility tests and mechanical properties. Recyclability of the material was also shown in a practical way, i.e., by cutting a cross-linked sample into small parts and compression molding them into new samples displaying comparable mechanical properties, which is not possible for conventionally cross-linked rubbers.

A simple two-step approach involving rubber modification and cross-linking yields fully reworkable, elastic rubber products.

A method for using Diels Alder thermo-reversible chemistry as cross-linking tool for rubber products is demonstrated. In this work, a commercial ...

Electrochemical Impedance Spectroscopy as a Tool for Electrochemical Rate Constant Estimation

Electrochemical impedance spectroscopy (EIS) was used for advanced characterization of organic electroactive compounds along with cyclic voltammetry (CV). In the case of fast reversible electrochemical processes, current is predominantly affected by the rate of diffusion, which is the slowest and limiting stage. EIS is a powerful technique that allows separate analysis of stages of charge transfer that have different AC frequency response. The capability of the method was used to extract the value of charge transfer resistance, which characterizes the rate of charge exchange on the electrode-solution interface. The application of this technique is broad, from biochemistry up to organic electronics. In this work, we are presenting the method of analysis of organic compounds for optoelectronic applications.

Electrochemical impedance spectroscopy (EIS) of species that undergo reversible oxidation or reduction in solution was used for determination of rate constants of oxidation or reduction.

Electrochemical impedance spectroscopy (EIS) was used for advanced characterization of organic electroactive compounds along with cyclic voltammetry (CV). ...

Raman and IR Spectroelectrochemical Methods as Tools to Analyze Conjugated Organic Compounds

In the presented work, two spectroelectrochemical techniques are discussed as tools for the analysis of the structural changes occurring in the molecule on the vibrational level of energy. Raman and IR spectroelectrochemistry can be used for advanced characterization of the structural changes in the organic electroactive compounds. Here, the step-by-step analysis by means of Raman and IR spectroelectrochemistry is shown. Raman and IR spectroelectrochemical techniques provide complementary information about structural changes occurring during an electrochemical process, i.e. allows for the investigation of redox processes and their products. The examples of IR and Raman spectroelectrochemical analysis are presented, in which the products of the redox reactions, both in solution and solid state, are identified.

A protocol of step-by-step Raman and IR spectroelectrochemical analysis is presented.

In the presented work, two spectroelectrochemical techniques are discussed as tools for the analysis of the structural changes occurring in the molecule ...

Using Cyclic Voltammetry, UV-Vis-NIR, and EPR Spectroelectrochemistry to Analyze Organic Compounds

Cyclic voltammetry (CV) is a technique used in the analysis of organic compounds. When this technique is combined with electron paramagnetic resonance (EPR) or ultraviolet-visible and near-infrared (UV-Vis-NIR) spectroscopies, we obtain useful information such as electron affinity, ionization potential, band-gap energies, the type of charge carriers, and degradation information that can be used to synthesize stable organic electronic devices. In this study, we present electrochemical and spectroelectrochemical methods to analyze the processes occurring in active layers of an organic device as well as the generated charge carriers.

In this article, we describe electrochemical, electron paramagnetic resonance, and ultraviolet-visible and near-infrared spectroelectrochemical methods to analyze organic compounds for application in organic electronics.

Cyclic voltammetry (CV) is a technique used in the analysis of organic compounds. When this technique is combined with electron paramagnetic resonance ...

Reactive Vapor Deposition of Conjugated Polymer Films on Arbitrary Substrates

We demonstrate a method of conformally coating conjugated polymers on arbitrary substrates using a custom-designed, low-pressure reaction chamber. Conductive polymers, poly(3,4-ethylenedioxythiophene) (PEDOT) and poly(3,4-propylenedioxythiophene) (PProDOT), and a semiconducting polymer, poly(thieno[3,2-b]thiophene) (PTT), were deposited on unconventional highly-disordered and textured substrates with high surface areas, such as paper, towels and fabrics. This reported deposition chamber is an improvement of previous vapor reactors because our system can accommodate both volatile and nonvolatile monomers, such as 3,4-propylenedioxythiophene and thieno[3,2-b]thiophene. Utilization of both solid and liquid oxidants are also demonstrated. One limitation of this method is that it lacks sophisticated in situ thickness monitors. Polymer coatings made by the commonly used solution-based coating methods, such as spin-coating and surface grafting, are often not uniform or susceptible to mechanical degradation. This reported vapor phase deposition method overcomes those drawbacks and is a strong alternative to common solution-based coating methods. Notably, polymer films coated by the reported method are uniform and conformal on rough surfaces, even at a micrometer scale. This feature allows for future application of vapor deposited polymers in electronics devices on flexible and highly textured substrates.

This paper presents a protocol for reactive vapor deposition of poly(3,4-ethylenedioxythiophene), poly(3,4-propylenedioxythiophene), and poly(thieno[3,2-b]thiophene) films on glass slides and rough substrates, such as textiles and paper.