Synthesis and Characterization of Novel Double-Functionalized Surface Modified Thermoplastic Elastomers

摘要该聚合物科学项目由材料研究部的聚合物项目和国际科学与工程办公室的中欧和欧亚项目共同资助。 本论文的目的是合成和表征新型非极性自组装纳米结构弹性嵌段共聚物，其表面修饰有极性羟基官能团。具体地，将合成无定形嵌段共聚物（arbPIB（OH）-b-P（St-co-TMeSt）），所述无定形嵌段共聚物包含在每个支化点处携带伯羟基的树枝状（树枝状）聚异丁烯（arbPIB）的核，侧接构成聚合物的约30重量%的聚（苯乙烯-共-对-胸腺甲基苯乙烯）玻璃态嵌段。通过使用4-（1，2-环氧乙烷-异丙基）-苯乙烯作为引发剂单体（引发剂-单体）与TiCl 4结合的异丁烯（IB）的活性碳阳离子聚合将在核的每个支化点处引入一个极性伯OH基团（arbPIB（OH））。初步证据表明，极性基团迁移到非极性聚合物的表面，可用于进一步改性。arbPIB（OH）核将通过NMR、SEC、FTIR、XPS和其他适当技术进行表征。在建立最佳合成条件后，嵌段共聚物将通过使用顺序单体加成的活性碳阳离子聚合来合成，然后通过适当的末端嵌段官能化来合成。块体的自组装由橡胶相和塑料相的相分离控制，从而导致材料的增强。静态和动态性能，这些后者在生物医学应用中的关键，将通过引入可逆氢键到苯乙烯相进行优化。这将通过St与pClMeSt的活性碳阳离子共聚来实现，然后将arbPIB（OH）-b-P（St-co-ClMeSt）的侧基苄基Cl基团转化为TMe基团，产生新型双官能化嵌段共聚物（arbPIB（OH）-b-P（St-co-TMeSt））。该嵌段共聚物将是热塑性弹性体（TPE），在室温下显示橡胶样行为，同时在高于玻璃态嵌段的玻璃化转变温度（Tg）下加工为塑料。将研究新型嵌段共聚物的本体和表面性质。具体而言，将研究动态疲劳和蠕变性能，并与目前使用的生物材料（硅橡胶、聚酯和聚氨酯）进行比较。预计支化PIB核和苯乙烯硬相中胸腺嘧啶官能团之间的氢键的组合将显著改善这种新型生物材料的动态疲劳和蠕变性能。表面羟基有望改善生物相容性。疲劳试验将在德国的拜罗伊特大学与Volker Altsdt教授合作进行，生物相容性试验将在波兰的斯切钦的波美拉尼亚医学院与Miroslawa El Fray教授合作进行。线性和星形支化PSt-b-PIB-b-PSt TPE（由PI共同发明）最近已获得FDA批准用作药物洗脱冠状动脉支架涂层。arbPIB-b-PSt嵌段共聚物是PIB基TPE家族的最新成员。目前的建议图表新的合成路线，引入OH基团在arbPIB为基础的嵌段共聚物的表面，并官能化的玻璃态端块。这项研究将导致两个新的材料家族：arbPIB（OH）-b-P（St-co-ClMeSt）和arbPIB（OH）-b-P（St-TMeSt）。由于氢键，P（St-co-TMeSt）末端嵌段预期具有比PSt更高的Tg（Tg ~100 ℃）。此外，还将检验通过氢键作用改善非晶嵌段TPE的动态疲劳和蠕变性能这一假设的有效性（氢键作用被认为是聚氨酯优异疲劳性能的原因）。这将是一个新的、具有普遍适用性的基本发展。这种新材料可能会成为医用级硅橡胶的替代品。更广泛的影响。与其他TPE一样，新材料是环保橡胶，因为它们可以再加工。生产和测试这些新生物材料的项目具有很强的国际性，在德国（机械测试）和波兰（生物相容性测试）有直接相关的合作。它是对提交给德国和波兰研究基金会（DFG）的提案的补充，该提案旨在研究新型纳米结构弹性体材料的动态蠕变和疲劳性能，这些材料有可能在特定的生物医学应用中取代硅橡胶。硅树脂乳房植入物是去年接受手术的25万美国妇女的唯一“选择”。这方面是非常受年轻人，特别是女性，所以这个程序将吸引潜在的美国女研究生，仍然在化学和材料科学领域的代表性不足。 项目的跨学科性质将使学生接触到各种科学学科（聚合物化学，有机化学，材料科学，生物化学，表面科学，聚合物工程，生物医学工程）。他们还将有机会在德国和波兰进行部分研究。接触不同的文化，组织和职业道德将使学生在全球经济中更好地工作，使他们对潜在雇主更具吸引力。

Summary. This project in polymer science is co-funded by the Polymers Program of the Division of Materials Research and the Central Europe and Eurasia Program of the Office of International Science and Engineering. It is aimed at the synthesis and characterization of novel non-polar self-assembling nanostructured elastomeric block copolymers, whose surface is decorated with polar hydroxyl functional groups. Specifically, amorphous block copolymers comprising a core of dendritic (arborescent) polyisobutylene (arbPIB) carrying a primary hydroxyl group at each branching point, flanked by poly(styrene-co-p-thymylmethylstyrene) glassy blocks constituting about 30wt% of the polymer, will be synthesized (arbPIB(OH)-b-P(St-co-TMeSt). Living carbocationic polymerization of isobutylene (IB) by using 4-(1,2-oxirane-isopropyl)-styrene as inimer (initiator-monomer) in conjunction with TiCl4 will introduce one polar primary OH group at each branching points of the core (arbPIB(OH)). Preliminary evidence suggests that polar groups migrate to the surface of non-polar polymers, available for further modification. The arbPIB(OH) core will be characterized by NMR, SEC, FTIR, XPS and other appropriate techniques. After establishing optimum synthesis conditions, block copolymers will be synthesized by living carbocationic polymerizations using sequential monomer addition, followed by appropriate functionalization of the end blocks. Self-assembly of the blocks is governed by the phase separation of the rubber and plastic phases, leading to reinforcement of the material. Both the static and dynamic properties, these latter critical in biomedical applications, will be optimized by introducing reversible hydrogen bonding into the styrenic phases. This will be accomplished by the living carbocationic copolymerization of St with pClMeSt, followed by converting the pendant benzylic Cl groups of the arbPIB-b-P(St-co-ClMeSt) into TMe groups, yielding a novel double-functionalized block copolymer (arbPIB(OH)-b-P(St-co-TMeSt). This block copolymer will be a thermoplastic elastomer (TPEs), displaying rubber-like behavior at room temperature while processing as plastics at above the glass transition temperature (Tg) of the glassy blocks. The bulk and surface properties of the novel block copolymer will be investigated. Specifically, the dynamic fatigue and creep properties will be investigated and compared to currently used biomaterials (silicone rubber, polyesters and polyurethanes). It is expected that the combination of the branched PIB core and the hydrogen bonding between the thymine functional groups in the styrenic hard phases will dramatically improve dynamic fatigue and creep properties of this novel biomaterial. The surface hydroxyl groups are expected to improve biocompatibility. Fatigue testing will be carried out at the University of Bayreuth, Germany, in collaboration with Professor Volker Altsdt, and biocompatibility testing will be carried out at the Pomeranian Medical Academy in Szczecin, Poland, in collaboration with Professor Miroslawa El Fray.Intellectual Merit. Linear and star-branched PSt-b-PIB-b-PSt TPEs (coinvented by the PI) have recently received FDA approval for use as drug-eluting coronary stent coating. arbPIB-b-PSt block copolymers are the newest members of the family of PIB-based TPEs. The current proposal charts new synthetic routes to introduce OH groups at the surface of arbPIB-based block copolymers, and to functionalize the glassy end blocks. This research would lead to two new families of materials: arbPIB(OH)-b-P(St-co-ClMeSt), and arbPIB(OH)-b-P(St-TMeSt). The P(St-co-TMeSt) end blocks are expected to have higher Tg than PSt (Tg ~100 C), due to hydrogen bonding. In addition, the validity of the hypothesis of improving the dynamic fatigue and creep properties of amorphous block TPEs by hydrogen bonding will be tested (hydrogen bonding is believed to be the reason for the excellent fatigue properties of polyurethanes). This would be a new, fundamental development with general applicability. The new materials may emerge as an alternative to medical grade silicone rubber. Broader Impacts. The new materials, just like other TPEs, are environmentally friendly rubbers since they can be reprocessed. The project to produce and test these new biomaterials has strong international aspects, with directly relevant collaborations in Germany (mechanical testing) and Poland (biocompatibility testing). It is complementary to proposals submitted to the German and Polish Research Foundations (DFG) to investigate the dynamic creep and fatigue properties of novel nanostructured elastomeric materials that have the potential to replace silicone rubber in specific biomedical applications. Silicone-based breast implants were the single "choice" for a quarter of a million American women who underwent the procedure last year. This aspect is very popular with young people, especially females, so this program will be appealing to potential female American graduate students, still under-represented in the field of chemistry and material science. The interdisciplinary nature of the projects will expose students to a great variety of scientific disciplines (polymer chemistry, organic chemistry, material science, biochemistry, surface science, polymer engineering, biomedical engineering). They will also have a chance to carry out part of their research in Germany and Poland. Exposure to different cultures, organizations and work ethics will prepare the students to work better in the global economy, making them more attractive to potential employers.