Name: the preparation and properties of thermo-reversibly cross-linked rubber via diels-alder chemistry
Uploaded: 2016-08-25T15:00:00.000+00:00
Duration: 7 min 2 s
Description: Watch this Scientific Journal Video about The Preparation and Properties of Thermo-reversibly Cross-linked Rubber Via Diels-Alder Chemistry at JoVE.com

This research forms part of the research program of the Dutch Polymer Institute, project #749.

1.橡胶改性<ol><li>在步骤表示开始实验前准备马来酸EPM（EPM-G-MA，49％乙烯，2.1％（重量）MA，锰= 50公斤/摩尔，PDI = 2.0）橡胶和糠（FFA）1.1.1- 1.1.4。5 <ol><li>干燥在真空烘箱中的EPM-G-MA橡胶一小时在175℃至本二酸转化成酐。11 </li><li>压缩模具中热压机在150℃10分钟，100巴0.1毫米厚的橡胶膜。 </li><li>将其放置在KBr压片保持器后记录所得膜的透射红外光谱。 注:水解的二羧酸成酸酐的转换完成，如果典型的羧酸峰（ <img alt="方程" src="/files/ftp_upload/54496/54496eq_v-sCO.jpg" /> =1710厘米-1）不存在和特征环酐峰（ <img alt="方程" src="/files/ftp_upload/54496/54496eq_v-asCO.jpg" /> =1856厘米-1 </s达&gt;）存在。5 </li><li>利用标准蒸馏法玻璃器皿，蒸馏2.8克FFA（沸点= 145℃，​​28.9毫摩尔; 3.0当量基于在EPM-G-MA MA含量。）在大气压力下。 </li></ol></li><li>通过称重45.0克EPM-G-MA橡胶（9.6毫摩尔，MA），并且它在500毫升四氢呋喃（THF），在23℃下在剧烈搅拌下的封闭烧杯中溶解制备10重量％的橡胶溶液。 </li><li>添加新鲜蒸馏的FFA至10重量％的橡胶溶液2.8克</li><li>搅拌在封闭系统中，将反应混合物在23℃下至少1小时。 </li><li>通过倾倒它慢慢倒入机械搅拌下丙​​酮的十倍（5L），产生聚合物产物，很容易掏出使用大镊子烧杯白色线程沉淀反应混合物中。 </li><li>干燥收集的产物（EPM-G-呋喃）至恒重，在35℃的真空烘箱中（这需要约1天）。 </li><li>压缩模具产生的，SLIghtly在热压两个金属板之间的模具在175℃下10分钟，100巴淡黄色产物在中间马来酰胺酸产物转化成酰亚胺产物。 </li><li>切成橡胶的小块用剪刀将所得噬菌斑（0.05克）和由在丙酮中浸渍它们以除去任何未反应的FFA彻底清洗。 </li><li>记录在压缩后KBr片剂夹持模塑成0.1mm厚的膜产品的透射红外光谱。5 注:没有任何剩余的酰胺酸可从没有一个峰在1530厘米-1推断39，40为修改成功的最说明问题的指示是几乎完全消失。 <img alt="方程" src="/files/ftp_upload/54496/54496eq_v-asCO.jpg" />在酸酐的1856厘米-1和外观<img alt="方程" src="/files/ftp_upload/54496/54496eq_v-sCO.jpg" />在1710厘米-1和CN伸缩振动（ <img alt="方程" src="/files/ftp_upload/54496/54496eq_v-sCN.jpg" /> =马来酰亚胺的1378厘米-1）。 </li><li>确定的EPM-G-MA以的反应转化EPM-G-呋喃来自酸酐基团的C = O对称伸缩振动的吸收率的降低（ <img alt="方程" src="/files/ftp_upload/54496/54496eq_v-asCO.jpg" /> =1856厘米-1）通过解卷积（R 2&gt; 0.95）后积分下的各个红外（FT-IR）的峰面积。5 注:甲基摇摆振动（ <img alt="方程" src="/files/ftp_upload/54496/54496eq_rho_ip_CH3.jpg" /> =723厘米-1），从EPM骨干始发，保持在修改不变，并可以被用作内部参考。 </li><li>通过在洗涤和干燥橡胶样品进行对于N，C和H元素分析（EA）确定的变形转换。5 注意:的摩尔含量可以从测量的质量百分比得出。在EPM-G-呋喃摩尔氮含量等于接枝呋喃基。所述的EPM EPM-G-:转换可以通过在EPM-G-MA前体（7.69×10 -3）用摩尔比N，MA接枝的单体的摩尔比进行比较，以对非接枝的EPM单体来计算呋喃样本。 </li><li>测量肖氏A硬度在压缩模塑的样品的至少10倍按压硬度上的橡胶样品，覆盖硬度的整个圆柱形表面。5 注:样品厚度为2±0.1毫米应该用于这些测试。 </li><li>测量伸长率（断裂）和宽使用15mm的夹钳长度为500±50mm /分钟的应变速率在大约1mm厚5毫米的样品进行拉伸试验的极限拉伸强度。从所得stres的初始斜率确定的杨氏模量第S - 应变曲线。 注:对于每个测量，试验10个样品，并排除异常数据的最高和最低值。 </li><li>通过用厚度为6±0.1毫米（T0）和一个直径与金属板之间13±0.1mm至3/4 次他们的初始厚度（t n）的的压缩圆柱形样品确定压缩设定在23℃ 70小时，让他们在50℃半小时放松并测量厚度（T I）。 注:压缩变定值可从（叔0 -tⅰ）/（T 0 -t n）的确定。 </li></ol> 2.狄尔斯 - 阿尔德交联和后处理<ol><li>实验前，根据报道的步骤合成由didodecylamine和马来酐（MA）的脂族双马来酰亚胺（BM）41 </li><li>称取40.0克的EPM-G-呋喃橡胶（8.6毫摩尔呋喃含量）和0.04g的酚类抗牛idant（十八烷基-1- [3,5-二 - 叔丁基-4-羟基苯基]丙酸酯），并在一个大的溶解它们，在23℃下封闭烧杯用500ml THF中。 </li><li>添加1.48克脂族双马来酰亚胺（4.3毫摩尔，0.5当量基于在EPM-G-呋喃呋喃含量）与10％（重量）溶液于烧杯。 </li><li>搅拌该反应混合物在50℃下在密闭烧杯至少1小时，然后取出盖打开系统以蒸发溶剂。也可使用旋转蒸发器进行蒸发THF。 </li><li>在35℃下干燥所收集的产物至恒重，在真空烘箱中。 </li><li>压缩模在175℃，30分钟和100巴的产物。 </li><li>通过在50℃的烘箱存放为至少三天退火所得的产物。 </li><li>用剪刀剪断得到的橡胶在小片（0.05克）的斑块和通过在丙酮中浸渍它们以除去任何未反应的组分和压缩模成一个0.1mm厚˚F彻底清洗ILM。 </li><li>记录所得到的膜的透射红外光谱在KBr压片保持器，使用作为1.9.1中描述的相同设置。5 </li><li>确定在呋喃环的COC对称伸缩振动从相对减少交联的转换（ <img alt="方程" src="/files/ftp_upload/54496/54496eq_v-sCOC.jpg" />如在1.10中描述=1013厘米-1）。5 </li><li>确定由对洗涤和干燥橡胶样品对于N，C和H进行的EA的交联的转换。5 </li><li>确定肖氏A硬度，杨氏模量，断裂伸长率，极限拉伸强度和压缩在如1.12-14描述的相同的方式设置在23℃。 </li><li>通过使用剪刀切割它们切成小块重新处理试验后的样品（±50 立方毫米）和压缩在相同的条件与相同尺寸的新的，均匀的样本下成形这些。 </li></ol><ol><li>加热内部间歇式混合机至70℃，并让它旋转在50rpm。 注:初始调节步骤通过用氮气使交联过程的更好的控制冲洗腔室。 </li><li>订阅18.1克ENB-EPDM（48重量％的乙烯，5.5％（重量）ENB）的到内部间歇式混合机，达到70％的填充因数并混合2分钟，得到一均匀的熔融物。 </li><li>饲料1.25份过氧化二（叔丁基过氧异丙基）苯），或1.88份80％纯，标准，半有效硫硫化体系中，并在70℃下将其与橡胶混合3分钟。 </li><li>压缩模具中热压得到的化合物在175℃下30分钟，100巴至固化。 </li><li>确定肖氏A硬度，杨氏模量，断裂伸长率和极限抗拉强度压缩在如1.12-14描述的相同的方式设置。 </li></ol> 4.ç罗斯 - 链路密度测定<ol><li>切一块约50毫克用剪刀压缩成型，交联的橡胶。 <ol><li>正是通过称量其在20ml的玻璃小瓶（W 0）确定的橡胶样品的初始重量。 </li><li>浸泡称量橡胶在15ml萘烷中。 </li></ol></li><li>让橡胶在萘烷溶胀直到其重量不再增加，当达到（约3天）平衡溶胀。 </li><li>小心地溶胀样品从瓶中，并仔细用薄纸轻拍表面以从表面去除任何溶剂而不挤压它。 </li><li>称量溶胀橡胶样品中的新的样品瓶（W 1）。 </li><li>在80℃干燥在真空烘箱中溶胀样品，直到达到恒重，并测定样品的干重量（W 2）。 </li><li>获得W 2 / W 0×100％的凝胶含量</li><li>确定交叉联密度（[XLD]在摩尔/厘米3）使用的Flory-Rehner公式42，43，[XLD] =（LN（1-V R）+ V R +χVR 2）/（2V S（0.5Vř -Vř1/3））采用V S上的溶剂（萘烷的摩尔体积:在23℃154毫升/摩尔），χ相互作用参数（萘烷-EPDM:0.121 + 0.278V R 44）和V R中的用为860千克/米3的密度（ρ）橡胶溶胀样品中，可以从W 2 /（W 2 +（W 1 -W 2）∙ρEPM-G-呋喃 /ρ 萘烷 ）来测定的体积分数EPM-G-呋喃和896公斤/米3为萘烷，分别。 </li></ol>

The author Martin van Duin is an employee of LANXESS Elastomers B.V. that produces EPM-g-MA rubbers used in this Article.

商业EPM-G-MA橡胶是热可逆的交联在一个简单的两步骤方法。该马来化的橡胶首先用FFA改性接枝呋喃基到橡胶骨架。所得未决呋喃显示反应性狄尔斯 - 阿尔德二烯。脂族的BM被用作交联剂，得到两个呋喃部分之间的热可逆桥。两个反应均成功使用根据红外光谱，元素分析好的转换（&gt; 80％）。交联是通过溶胀和溶解性试验，得到100％的凝胶含量示出。 为描述的协议的成功执行，这是至关重要的是，各个组件精心准备。不幸的是，通过利用这里描述的方法的可再加工的橡胶的制备不允许容易升频到较大数量。虽然编写本可修复橡胶制品，没有其他方法已经DES在公开的文献cribed，与马来酸酐的公知的自由基接枝EPM橡胶类比在这方面可以绘制。橡胶的32熔体修饰是不需要的溶剂，中间纯化或一个有前途的替代干燥的步骤，并且可以在商用设备例如熔体混合器或挤出机来执行。生产这种可再加工的橡胶会更时间，如果它是通过熔融加工要执行成本效益。另一方面，所描述的方法允许在反应更多的控制和更明确定义的终产物。 关于实现再加工橡胶和其它回收方法（ 如，脱硫）目前的方法之间的比较的更一般的水平，但必须指出的是，材料具有交联之前和所形成的交联无法在相对 ​​要修改低的温度（&gt; 180％）。然而，这种方法确实允许用于制造"摇篮到摇篮"可回收橡胶产物而devulcanized橡胶的可回收严重与处女部件限于最多百分之几的重用组合使用。54，55 的交联密度的从FT-IR和EA决定对应于从膨胀试验确定的DA的交联的EPM-G-呋喃。所得值是松散的交联橡胶状网络特性，并且对应于硫和过氧化物硫化的EPDM胶（1-5×10 -4摩尔/厘米3）的典型交联密度在文献中报道的53，54的对DA的交联样品的交联密度是与那些含硫和过氧化物硫化的EPDM的引用的，允许属性的比较。 最后，该肖氏A硬度，杨氏弹性模量，断裂伸长率，极限拉伸强度和压缩变定所有indicatË粘性聚合物的转化在加入BM的弹性橡胶网络。这些机械性质对应于那些含硫和过氧化物硫化的引用样品和它们再处理的热可逆交联橡胶后保留。达5次无属性的任何显著损失进行的材料的再处理。 所提出的研究结果为（可逆）的（EPM）橡胶通过（复古）交联的新的路线Diels-Alder反应，补充橡胶回收的工具箱。它们铺平对这种交联的策略（并且这些可能带来的可回收）用于各种橡胶产品的应用的方式。

硫磺硫化和过氧化物固化是目前在橡胶工业中的主要工业交联技术，产生不可逆的化学交联，以防止熔融后处理:1，2 A&#39;摇篮到摇篮"的方式回收交联的橡胶，需要一种材料表现在提供服务的条件类似于永久交联的橡胶，而具有热塑性的高温下的加工性和完整的可回收性。要达到这样的可回收的方法使用与该对外部刺激作出反应的可逆交联，如温度（从未来的工业应用的观点出发最可行的）的橡胶状网络。3-5这些交联的以相对较低的服务的形成温度是必需的橡胶的良好的机械特性，而在高温下（类似于原始的非交联的化合物的处理温度）的裂解允许当r该材料的ecycling。 一些具体的材料可以是可逆地通过经由缩聚反应6或通过所谓的可逆网络拓扑利用所谓的动态共价网络经由酯交换反应冷冻交联的。7-9这些方法的缺点是设计的必要性和合成新的聚合物，而不是修改已经具有所需性质的现有商业橡胶。技术来热-可逆交联橡胶涉及氢键，离子相互作用和共价键，如通过热活化的二硫化物重排。10-13最近，热可逆交联通过狄尔斯-阿尔德（DA）的化学开发的。14 -21 DA化学可以应用于范围广泛的聚合物，并代表一个流行的选择，特别是因为对DA反应允许相对快的动力学和反应条件温和。17，22-24钍EIR低耦合和高的去耦的温度使呋喃和马来酰亚胺优良候选可逆聚合物交联。18-20，25-28 本工作的目的是提供一种用于使用DA化学作为用于工业橡胶产品（ 图1）的热可逆交联的工具的方法。5首先，饱和烃类弹性体，如乙烯的反应性/丙烯橡胶（EPM），必须增加。促进这方面的一个商业相关的例子是马来酸酐（MA）的过氧化物引发自由基接枝29-34其次，呋喃组可以通过插入糠（FFA）插入挂件酸酐接枝到这样一种马来EPM橡胶以形成酰亚胺。35，36最后，从而被附接到橡胶骨架上的呋喃基部分可以再参加热可逆DA化学作为富电子二烯。25，37的电子婆或双-马来酰亚胺（BM）是该交联反应的合适的亲二烯体。19，26，38 <img alt="图1" src="/files/ftp_upload/54496/54496fig1.jpg" /> 图1. 反应方案。呋喃嫁接和EPM-G-MA橡胶（从5许可转载）双马来酰亚胺的交联。 <a href="https://www-jove-com.remotexs.ntu.edu.sg/files/ftp_upload/54496/54496fig1large.jpg" target="_blank">请点击此处查看该图的放大版本。</a>

<table><tbody><tr><td>ENB-EPDM</td><td>LANXESS Elastomers B.V.</td><td>Keltan 8550C</td><td></td></tr><tr><td>EPM-g-MA</td><td>LANXESS Elastomers B.V.</td><td>Keltan DE5005</td><td>Vacuum oven for one hour at 175&amp;nbsp;&amp;deg;C</td></tr><tr><td>furfurylamine</td><td>Sigma-Aldrich</td><td>F20009</td><td>Freshly distillated before use</td></tr><tr><td>di-dodecylamine</td><td>Sigma-Aldrich</td><td>36784</td><td></td></tr><tr><td>maleic anhydride</td><td>Sigma-Aldrich</td><td>M0357</td><td></td></tr><tr><td>octadecyl-1-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate</td><td>Sigma-Aldrich</td><td>367079</td><td></td></tr><tr><td>bis(tert-butylperoxy-iso-propyl) benzene</td><td>Sigma-Aldrich</td><td>531685</td><td></td></tr><tr><td>tetrahydrofuran</td><td>Sigma-Aldrich</td><td>401757</td><td></td></tr><tr><td>decalin</td><td>Sigma-Aldrich</td><td>294772</td><td></td></tr><tr><td>acetone</td><td>Sigma-Aldrich</td><td>320110</td><td></td></tr></tbody></table>

the preparation and properties of thermo-reversibly cross-linked rubber via diels-alder chemistry

论证一种利用狄尔斯阿尔德热可逆化学为橡胶制品交联方法工具。在这项工作中，一个商用乙烯 - 丙烯橡胶，马来酸酐接枝，是热可逆分两步交联的。挂起的酸酐部分首先与糠胺接枝呋喃基的橡胶主链改性。这些挂件呋喃基是然后经由狄尔斯 - 阿尔德偶联反应的双 - 马来酰亚胺交联的。两个反应可以在广泛的实验条件下进行，并且可以很容易地在大范围的应用。所得狄尔斯 - 阿尔德交联橡胶的材料性质类似于过氧化物固化的乙烯/丙烯/二烯橡胶（EPDM）参考。该交联通过复古Diels-Alder反应在升高的温度下破裂（&gt; 150℃），并且可以通过在较低温度下热退火（50-70℃）进行改革。该系统的可逆性被证明机智ħ红外光谱，溶解度试验和机械性能。该材料的可回收也显示在一个实际的方式， 也就是说，通过切割的交联样品分成小份并压缩它们成型为新的样本显示可比的机械性能，这是不可能的常规交联的橡胶。

EPM-G-MA的成功修饰成EPM-G-呋喃和交联与双马来酰亚胺由傅立叶所示变换红外光谱（FTIR）（ 图2）。呋喃基的在EPM-G-呋喃产物的存在可以从CC脂族伸缩峰的分裂（推断<img alt="方程" src="/files/ftp_upload/54496/54496eq_v-sCC.jpg" /> =1050厘米-1）分为两个呋喃峰（ <img alt="方程" src="/files/ftp_upload/54496/54496eq_v-asCOC.jpg" /> =1073厘米-1 <img alt="方程" src="/files/ftp_upload/54496/54496eq_v-sCOC.jpg" /> =1013厘米-1）时，C = C呋喃伸缩振动的外观（ <img alt="方程" src="/files/ftp_upload/54496/54496eq_v-sCC.jpg" /> =1504厘米-1）为599 -1。15，37，37呋喃环和1,4361345厘米拉伸峰-1不可不为O变形振动bserved因为它们是由橡胶主链的大重叠CH 2 -vibrations为1450 -1 1350 -1。15对BM的掺入隐藏可从外观推断<img alt="方程" src="/files/ftp_upload/54496/54496eq_delta_ip_DAring.jpg" />在1190厘米-1和特性琥珀酰亚胺频带（ <img alt="方程" src="/files/ftp_upload/54496/54496eq_v-sCNC.jpg" /> =1385厘米-1， <img alt="方程" src="/files/ftp_upload/54496/54496eq_delta_ip_HNC.jpg" /> =1311厘米-1和<img alt="方程" src="/files/ftp_upload/54496/54496eq_delta_asoop_OCN.jpg" /> =620厘米-1）。45，46的呋喃相关吸收（ <img alt="方程" src="/files/ftp_upload/54496/54496eq_v-sCOC.jpg" />一旦交联和）减小<img alt="方程" src="/files/ftp_upload/54496/54496eq_v-sCO.jpg" />羰基带随着周围1770厘米第二吸收的结果-1<html>被归因于由环合加成得到的琥珀酰亚胺环。25 FTIR和元素分析用于测定修饰和交联转化（ 表1）。的FT-IR和EA转换被用来确定的交联密度对DA的交联的EPM-G-呋喃，其被发现是1.8×10 -4±3×10 -5摩尔/厘米3。根据溶胀试验（协议4），所有的交联样品的凝胶含量为约100％和DA的交联的EPM-G-呋喃的交联密度是2.1×10 -4±2×10 - 5摩尔/厘米3。的含硫和过氧化物固化的EPDM参考系统的交联密度，结果分别为1.7×10 -4±6×10 -6和1.8×10 -4±8×10 -6摩尔/分别厘米3， 。 T"FO:保together.within页="1"&gt; <img alt="图2" src="/files/ftp_upload/54496/54496fig2.jpg" /> 图 2. FT-IR吸收光谱的左光谱:EPM-G-MA（红色）和改性的EPM-G-呋喃（黑色）和右:非交联的EPM-G-呋喃（黑色）的和第尔斯-阿尔德交联EPM-G-呋喃（蓝色）（从5许可转载）。 <a href="https://www-jove-com.remotexs.ntu.edu.sg/files/ftp_upload/54496/54496fig2large.jpg" target="_blank">请点击此处查看该图的放大版本。</a> <table border="1" fo:keep-together.within-page="1" fo:keep-with-next.within-page="always"><tbody><tr><td></td><td> 重量％N </td><td> 重量％C </td><td> 重量％H </td><td> FT-IR转化率（％） </td><td> EA转化率（％） </td></tr><tr><td> EPM-G-MA </td><td> &lt;0.01 </td><td> 84.7 </td><td> 14.3 </td><td></td><td> - </td></tr><tr><td> EPM-G-呋喃</td><td> 0.3 </td><td> 84.8 </td><td> 14.2 </td><td> 96 </td><td> 93 </td></tr><tr><td> DA的交联的EPM-G-呋喃</td><td> 0.4 </td><td> 84.2 </td><td> 14 </td><td> 72 </td><td> 80 </td></tr></tbody></table> 表1. 反应转化。从元素分析和FT-IR结果（适于与许可5）。 对DA的交联的EPM-G-呋喃产物的解交联随后透射FT-IR（ 图3）。一些特征呋喃峰如，在分别1504 1013 -1在50℃下在热退火降低和在175℃下压缩成形后增加。这表明，交联和去交联通过接枝呋喃基之间的可逆的DA反应发生和添加的BM交联剂。47溶解度测试以观察交联和去交联的影响的更实用的方法。 EPM-G-呋喃可溶于23℃萘烷（5重量％）。相同的材料的交联用BM是在相同的条件下显然不溶。交联反应的热可逆性1小时加热至175℃期间的产物溶解中。最后，测试材料的再加工性的一个实用的方法是通过研磨或切割的交联橡胶和压缩在160℃和100巴30分钟成形的。所得再加工材料被发现有2.0×10 -4±2×10 -5摩尔/ cm 3的交联密度。当EPDM橡胶是不可逆地与过氧化物交联的，重塑的相同条件下的切割块不会产生一个相干样本（ 图4）。 图3. FT-IR吸收光谱。EPM的-G-呋喃和DA（DE /重）光谱交联EPM-G-呋喃（从5许可转载）。 <a href="https://www-jove-com.remotexs.ntu.edu.sg/files/ftp_upload/54496/54496fig3large.jpg" target="_blank">请点击此处查看这个大版本数字。</a> <img alt="图4" src="/files/ftp_upload/54496/54496fig4.jpg" /> 图4. 再加工橡胶样品。热可逆交联和含硫和过氧化物硫化橡胶，它们都在相同的条件下，再加工样品条。 <a href="https://www-jove-com.remotexs.ntu.edu.sg/files/ftp_upload/54496/54496fig4large.jpg" target="_blank">请点击此处查看该图的放大版本。</a> 硬度增加，补偿从非交联的EPM-G-MA和EPM-G-呋喃前体到DA交联的EPM-G-呋喃（ 图5）去时ression集减小。这清楚地表明了粘性聚合物的转化成在发生交联的弹性网络。硬度和压缩变定分别为44肖氏A和5％的再加工的样品是媲美原始DA的交联样品。硬度和压缩变定的硫和过氧化物交联EPDM橡胶的分别为60和61肖氏A和5％和8％。虽然这些不可逆交联的样品具有更高的硬度值，其压缩永久变形是稍差到DA的交联样品。 从非交联的EPM-G-MA要修改的EPM-G-呋喃（ 图6）时的断裂伸长率下降。这种差异可以通过挂起，conjugat的协同作用来解释编呋喃基。48及其增加刚性，π堆叠稳定和非常低的程度的自由基交联呋喃之间可能是足够的橡胶的弹性降低到一定程度。交联的EPM-G-呋喃样品显示显著更高的拉伸模量和断裂值低伸长相比，他们的非交联的前体。这些高拉伸模量和低的延伸率是指示用于交联的橡胶。49，50似乎也回收交联的橡胶保留的交联橡胶的这些特征的属性，这表明这些交联橡胶可以重塑或返工不管他们的高模量和低伸长率。平均应力 - 应变曲线还表明，该热可逆，DA的交联橡胶，前和后处理后，产率在较高的压力和比其株下部非交联的EPM-G-MA和EPM-G-呋喃前体。这种区分的illustra<html>如由过氧化物和硫硫化的EPDM的样品示出略去对交联的和非交联的橡胶的不同的行为。51，52，这些过氧化物和硫黄硫化的参考样本似乎具有的杨氏模量小于DA交叉略高尽管它们进行测定，以具有类似的交联密度联橡胶。拉伸强度和断裂伸长率然而对DA的交联样品的断裂，是至少与上述过氧化物和硫固化样品的一样好。 <img alt="图5" src="/files/ftp_upload/54496/54496fig5.jpg" /> 图5. 硬度和压缩永久变形，结果用于非交联的EPM-G-MA和EPM-G-呋喃，DA交联的EPM-G-呋喃和不可逆含硫和过氧化物硫化的EPDM橡胶。误差棒代表标准偏差（从5许可重印）。负载/ 54496 / 54496fig5large.jpg"目标="_空白"&gt;点击此处查看该图的放大版本。 <img alt="图6" src="/files/ftp_upload/54496/54496fig6.jpg" /> 图6. 拉伸试验。结果EPM-G-MA（1），EPM-G-呋喃（2），DA交联的EPM-G-呋喃（3）和再加工，DA交联的EPM-G-呋喃（4）与硫（5）和过氧化物（6）硫化的EPDM在一起。位应力 - 应变曲线图（左）和对应的杨氏模量，拉伸强度和断裂伸长率（右）。误差棒代表标准偏差。 （经许可后转载自5） <a href="https://www-jove-com.remotexs.ntu.edu.sg/files/ftp_upload/54496/54496fig6large.jpg" target="_blank">点击此处查看该图的放大版本。</a>

Watch this Scientific Journal Video about The Preparation and Properties of Thermo-reversibly Cross-linked Rubber Via Diels-Alder Chemistry at JoVE.com

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

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

热可逆交联橡胶通过的Diels-Alder反应的化学制备与性能

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

the-preparation-properties-thermo-reversibly-cross-linked-rubber-via

Nanyang Technological University

Research

Education

JoVE Core

JoVE Journal

Organic Chemistry

Chemistry

Unit 1

Dienes, Conjugated Pi Systems, and Pericyclic Reactions

SCIENTISTS IN ACTION

13.6K 次观看.  University of Groningen. A simple two-step approach involving rubber modification and cross-linking yields fully reworkable, elastic rubber products. 

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

A Facile and Efficient Approach for the Production of Reversible Disulfide Cross-linked Micelles

Nanomedicine is an emerging form of therapy that harnesses the unique properties of particles that are nanometers in scale for biomedical application. Improving drug delivery to maximize therapeutic outcomes and to reduce drug-associated side effects are some of the cornerstones of present-day nanomedicine. Nanoparticles in particular have found a wide application in cancer treatment. Nanoparticles that offer a high degree of flexibility in design, application, and production based on the tumor microenvironment are projected to be more effective with rapid translation into clinical practice. The polymeric micellar nano-carrier is a popular choice for drug delivery applications.
In this article, we describe a simple and effective protocol for synthesizing drug-loaded, disulfide cross-linked micelles based on the self-assembly of a well-defined amphiphilic linear-dendritic copolymer (telodendrimer, TD). TD is composed of polyethylene glycol (PEG) as the hydrophilic segment and a thiolated cholic acid cluster as the core-forming hydrophobic moiety attached stepwise to an amine-terminated PEG using solution-based peptide chemistry. Chemotherapy drugs, such as paclitaxel (PTX), can be loaded using a standard solvent evaporation method. The O2-mediated oxidation was previously utilized to form intra-micellar disulfide cross-links from free thiol groups on the TDs. However, the reaction was slow and not feasible for large-scale production. Recently, an H2O2-mediated oxidation method was explored as a more feasible and efficient approach, and it was 96 times faster than the previously reported method. Using this approach, 50 g of PTX-loaded, disulfide cross-linked nanoparticles have been successfully produced with narrow particle size distribution and high drug loading efficiency. The stability of the resulting micelle solution is analyzed using disrupting conditions such as co-incubation with a detergent, sodium dodecyl sulfate, with or without a reducing agent. The drug-loaded, disulfide cross-linked micelles demonstrated less hemolytic activity when compared to their non-cross-linked counterparts.

To deliver cancer drugs to tumor sites with high specificity and reduced side effects, new methods based on nanoparticles are required. Here, we describe disulfide cross-linked micelles that can be easily prepared by hydrogen peroxide-mediated oxidation and are able to dissociate efficiently under a reducing tumor environment to release payloads.

可逆二硫键交联胶束生产的简便和有效途径

Nanomedicine is an emerging form of therapy that harnesses the unique properties of particles that are nanometers in scale for biomedical application. ...

科研

生物化学

Synthesis of Programmable Main-chain Liquid-crystalline Elastomers Using a Two-stage Thiol-acrylate Reaction

This study presents a novel two-stage thiol-acrylate Michael addition-photopolymerization (TAMAP) reaction to prepare main-chain liquid-crystalline elastomers (LCEs) with facile control over network structure and programming of an aligned monodomain. Tailored LCE networks were synthesized using routine mixing of commercially available starting materials and pouring monomer solutions into molds to cure. An initial polydomain LCE network is formed via a self-limiting thiol-acrylate Michael-addition reaction. Strain-to-failure and glass transition behavior were investigated as a function of crosslinking monomer, pentaerythritol tetrakis(3-mercaptopropionate) (PETMP). An example non-stoichiometric system of 15 mol% PETMP thiol groups and an excess of 15 mol% acrylate groups was used to demonstrate the robust nature of the material. The LCE formed an aligned and transparent monodomain when stretched, with a maximum failure strain over 600%. Stretched LCE samples were able to demonstrate both stress-driven thermal actuation when held under a constant bias stress or the shape-memory effect when stretched and unloaded. A permanently programmed monodomain was achieved via a second-stage photopolymerization reaction of the excess acrylate groups when the sample was in the stretched state. LCE samples were photo-cured and programmed at 100%, 200%, 300%, and 400% strain, with all samples demonstrating over 90% shape fixity when unloaded. The magnitude of total stress-free actuation increased from 35% to 115% with increased programming strain. Overall, the two-stage TAMAP methodology is presented as a powerful tool to prepare main-chain LCE systems and explore structure-property-performance relationships in these fascinating stimuli-sensitive materials.

A novel methodology is presented to synthesize and program main-chain liquid-crystalline elastomers using commercially available starting monomers. A wide range of thermomechanical properties was tailored by adjusting the amount of crosslinker, while the actuation performance was dependent on the amount of applied strain during programming.

的可编程主链液晶性弹性体用双级硫醇丙烯酸酯反应合成

This study presents a novel two-stage thiol-acrylate Michael addition-photopolymerization (TAMAP) reaction to prepare main-chain liquid-crystalline ...

化学

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.

使用Photoredox催化剂蠕虫状胶束的简便合成可见光介导的分散聚合

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

Synthesis of Soft Polysiloxane-urea Elastomers for Intraocular Lens Application

This study discusses a synthesis route for soft polysiloxane-based urea (PSU) elastomers for their applications as accommodating intraocular lenses (a-IOLs). Aminopropyl-terminated polydimethylsiloxanes (PDMS) were previously prepared via the ring-chain equilibration of the cyclic siloxane octamethylcyclotetrasiloxane (D4) and 1,3-bis(3-aminopropyl)-tetramethyldisiloxane (APTMDS). Phenyl groups were introduced into the siloxane backbone via the copolymerization of D4 and 2,4,6,8-tetramethyl-2,4,6,8-tetraphenyl-cyclotetrasiloxane (D4Me,Ph). These polydimethyl-methyl-phenyl-siloxane-block copolymers were synthesized for increasing the refractive indices of polysiloxanes. For applications as an a-IOL, the refractive index of the polysiloxanes must be equivalent to that of a young human eye lens. The polysiloxane molecular weight is controlled by the ratio of the cyclic siloxane to the endblocker APTMDS. The transparency of the PSU elastomers is examined by the transmittance measurement of films between 200 and 750 nm, using a UV-Vis spectrophotometer. Transmittance values at 750 nm (upper end of the visible spectrum) are plotted against the PDMS molecular weight, and &#62; 90% of the transmittance is observed until a molecular weight of 18,000 g&#183;mol&#8722;1. Mechanical properties of the PSU elastomers are investigated using stress-strain tests on die-cut dog-bone-shaped specimens. For evaluating mechanical stability, mechanical hysteresis is measured by repeatedly stretching (10x) the specimens to 5% and 100% elongation. Hysteresis considerably decreases with the increase in the PDMS molecular weight. In vitro cytotoxicity of some selected PSU elastomers is evaluated using an MTS cell viability assay. The methods described herein permit the synthesis of a soft, transparent, and noncytotoxic PSU elastomer with a refractive index approximately equal to that of a young human eye lens.

This study describes synthetic routes for aminopropyl-terminated polydimethylsiloxanes and polydimethyl-methyl-phenyl-siloxane-block copolymers and for soft polysiloxane-based urea (PSU) elastomers. It presents the application of PSUs as accommodating an intraocular lens. An evaluation method for in vitro cytotoxicity is also described.

软聚聚硅氧烷-尿素弹性体在人工晶体中的应用

This study discusses a synthesis route for soft polysiloxane-based urea (PSU) elastomers for their applications as accommodating intraocular lenses ...

Synthesis of Terpolymers at Mild Temperatures Using Dynamic Sulfur Bonds in Poly(S-Divinylbenzene)

Elemental sulfur (S8) is a byproduct of the petroleum industry with millions of tons produced annually. Such abundant production and limited applications lead to sulfur as a cost-efficient reagent for polymer synthesis. Inverse vulcanization combines elemental sulfur with a variety of monomers to form functional polysulfides without the need for solvents. Short reaction times and straight forward synthetic methods have led to rapid expansion of inverse vulcanization. However, high reaction temperatures (&#62;160 &#176;C) limit the types of monomers that can be used. Here, the dynamic sulfur bonds in poly(S-divinylbenzene) are used to initiate polymerization at much lower temperatures. The S-S bonds in the prepolymer are less stable than S-S bonds in S8, allowing radical formation at 90 &#176;C rather than 159 &#176;C. A variety of allyl and vinyl ethers have been incorporated to form terpolymers. The resulting materials were characterized by 1H NMR, gel permeation chromatography, and differential scanning calorimetry, as well as examining changes in solubility. This method expands on the solvent-free, thiyl radical chemistry utilized by inverse vulcanization to create polysulfides at mild temperatures. This development broadens the range of monomers that can be incorporated thus expanding the accessible material properties and possible applications.

Synthesis of Terpolymers at Mild Temperatures Using Dynamic Sulfur Bonds in PolyS-Divinylbenzene

The goal of this protocol is to initiate polymerization using dynamic sulfur bonds in poly(S-divinylbenzene) at mild temperatures (90 &#176;C) without using solvents. Terpolymers are characterized by GPC, DSC and 1H NMR, and tested for changes in solubility.

在高温下利用聚苯 (s-二硝基苯) 动态硫键合成三聚体

Elemental sulfur (S8) is a byproduct of the petroleum industry with millions of tons produced annually. Such abundant production and limited applications ...

Three-dimensional Biomimetic Technology: Novel Biorubber Creates Defined Micro- and Macro-scale Architectures in Collagen Hydrogels

Tissue scaffolds play a crucial role in the tissue regeneration process. The ideal scaffold must fulfill several requirements such as having proper composition, targeted modulus, and well-defined architectural features. Biomaterials that recapitulate the intrinsic architecture of in vivo tissue are vital for studying diseases as well as to facilitate the regeneration of lost and malformed soft tissue. A novel biofabrication technique was developed which combines state of the art imaging, three-dimensional (3D) printing, and selective enzymatic activity to create a new generation of biomaterials for research and clinical application. The developed material, Bovine Serum Albumin rubber, is reaction injected into a mold that upholds specific geometrical features. This sacrificial material allows the adequate transfer of architectural features to a natural scaffold material. The prototype consists of a 3D collagen scaffold with 4 and 3 mm channels that represent a branched architecture. This paper emphasizes the use of this biofabrication technique for the generation of natural constructs. This protocol utilizes a computer-aided software (CAD) to manufacture a solid mold which will be reaction injected with BSA rubber followed by the enzymatic digestion of the rubber, leaving its architectural features within the scaffold material.

An innovative biofabrication technique was developed to engineer three-dimensional constructs that resemble the architectural features, components, and mechanical properties of in vivo tissue. This technique features a newly developed sacrificial material, BSA rubber, which transfers detailed spatial features, reproducing the in vivo architectures of a wide variety of tissues.

三维仿生技术:新型Biorubber创建自定义微观和宏观尺度架构的胶原凝胶

Tissue scaffolds play a crucial role in the tissue regeneration process. The ideal scaffold must fulfill several requirements such as having proper ...

生物工程

Evaluation of the Curing of Adhesive Systems by Rheological and Thermal Testing

The analysis of thermal processes associated to the curing of adhesives and the study of mechanical behavior once cured, provide key information to choose the best option for any specific application. The proposed methodology for the curing characterization, based on thermal analysis and rheology, is described through the comparison of three commercial adhesives. The experimental techniques used here are Thermogravimetric Analysis (TGA), Differential Scanning Calorimetry (DSC) and Rheology. TGA provides information about the thermal stability and filler content, DSC allows the evaluation of some thermal events associated to the cure reaction and to thermal changes of the cured material when subjected to temperature changes. Rheology complements the information of the thermal transformations from a mechanical point of view. Thus, the curing reaction can be tracked through the elastic modulus (mainly the storage modulus), the phase angle and the gap. In addition, it is also shown that although DSC is of no use to study the curing of moisture curable adhesives, it is a very convenient method to evaluate the low temperature glass transition of amorphous systems.

An experimental methodology based on thermal and rheological measurements is proposed to characterize the curing process of adhesives with to obtain useful information for industrial adhesive selection.

流变和热测试对粘合系统固化的评价

The analysis of thermal processes associated to the curing of adhesives and the study of mechanical behavior once cured, provide key information to choose ...

工程学

Fabricating Degradable Thermoresponsive Hydrogels on Multiple Length Scales via Reactive Extrusion, Microfluidics, Self-assembly, and Electrospinning

While various smart materials have been explored for a variety of biomedical applications (e.g., drug delivery, tissue engineering, bioimaging, etc.), their ultimate clinical use has been hampered by the lack of biologically-relevant degradation observed for most smart materials. This is particularly true for temperature-responsive hydrogels, which are almost uniformly based on polymers that are functionally non-degradable (e.g., poly(N-isopropylacrylamide) (PNIPAM) or poly(oligoethylene glycol methacrylate) (POEGMA)). As such, to effectively translate the potential of thermoresponsive hydrogels to the challenges of remote-controlled or metabolism-regulated drug delivery, cell scaffolds with tunable cell-material interactions, theranostic materials with the potential for both imaging and drug delivery, and other such applications, a method is required to render the hydrogels (if not fully degradable) at least capable of renal clearance following the required lifetime of the material. To that end, this protocol describes the preparation of hydrolytically-degradable hydrazone-crosslinked hydrogels on multiple length scales based on the reaction between hydrazide and aldehyde-functionalized PNIPAM or POEGMA oligomers with molecular weights below the renal filtration limit. Specifically, methods to fabricate degradable thermoresponsive bulk hydrogels (using a double barrel syringe technique), hydrogel particles (on both the microscale through the use of a microfluidics platform facilitating simultaneous mixing and emulsification of the precursor polymers and the nanoscale through the use of a thermally-driven self-assembly and cross-linking method), and hydrogel nanofibers (using a reactive electrospinning strategy) are described. In each case, hydrogels with temperature-responsive properties similar to those achieved via conventional free radical cross-linking processes can be achieved, but the hydrazone cross-linked network can be degraded over time to re-form the oligomeric precursor polymers and enable clearance. As such, we anticipate these methods (which may be generically applied to any synthetic water-soluble polymer, not just smart materials) will enable easier translation of synthetic smart materials to clinical applications.

Protocols are described for the fabrication of degradable thermoresponsive hydrogels based on hydrazone cross-linking of polymeric oligomers on the bulk scale, microscale, and nanoscale, the latter for preparation of both gel nanoparticles and nanofibers.

通过反应挤出、微流体、自组装和电纺丝制备多长尺度可降解 Thermoresponsive 水凝胶

While various smart materials have been explored for a variety of biomedical applications (e.g., drug delivery, tissue engineering, bioimaging, etc.), ...

Designed for Molecular Recycling: A Lignin-Derived Semi-aromatic Biobased Polymer

The development of chemically recyclable biopolymers offers opportunities within the pursuit of a circular economy. Chemically recyclable biopolymers make a positive effort to solve the issue of polymer materials in the disposal phase after the use phase. In this paper, the production of biobased semi-aromatic polyesters, which can be extracted entirely from biomass such as lignin, is described and visualized. The polymer poly-S described in this paper has thermal properties similar to certain commonly used plastics, such as PET. We developed a Green Knoevenagel reaction, which can efficiently produce monomers from aromatic aldehydes and malonic acid. This reaction has been proven to be scalable and has a remarkably low calculated E-factor. These polyesters with ligno-phytochemicals as a starting point show an efficient molecular recycling with minimal losses. The polyester poly(dihydrosinapinic acid) (poly-S) is presented as an example of these semi-aromatic polyesters, and the polymerization, depolymerization, and re-polymerization are described.

An example of a closed-loop approach towards a circular materials economy is described here. A whole sustainable cycle is presented where biobased semi-aromatic polyesters are designed by polymerization, depolymerization, and then re-polymerized with only slight changes in their yields or final properties.

专为分子回收而设计:一种褐宁衍生的半芳烃生物基聚合物

The development of chemically recyclable biopolymers offers opportunities within the pursuit of a circular economy. Chemically recyclable biopolymers make ...

Depolymerizable Olefinic Polymers Based on Fused-Ring Cyclooctene Monomers

The growing consumption of synthetic polymers and the accumulation of polymer waste have led to a pressing need for new routes to sustainable materials. Achieving a closed-loop polymer economy via chemical recycling to monomer (CRM) is one such promising route. Our group recently reported a new CRM system based on polymers prepared by ring-opening metathesis polymerization (ROMP) of trans-cyclobutane fused cyclooctene (tCBCO) monomers. This system offers several key advantages, including the ease of polymerization at ambient temperatures, quantitative depolymerization to monomers under mild conditions, and a broad range of functionalities and thermomechanical properties. Here, we outline detailed protocols for the preparation of tCBCO-based monomers and their corresponding polymers, including the preparation of elastic polymer networks and compression molding of linear thermoplastic polymers. We also outline the preparation of high ring strain E-alkene tCBCO monomers and their living polymerization. Finally, the procedures for the depolymerization of linear polymers and polymer networks are also demonstrated.

Here, we describe protocols for the preparation of trans-cyclobutane fused cyclooctenes (tCBCO),&#160;their polymerization to prepare depolymerizable olefinic polymers, and the depolymerization of these polymers under mild conditions. Additionally, protocols for the preparation of depolymerizable networks and compression molding of rigid linear plastics based on this system are described.

基于熔环环辛烯单体的可解聚烯烃聚合物

The growing consumption of synthetic polymers and the accumulation of polymer waste have led to a pressing need for new routes to sustainable materials. ...