Controlled Radical Polymerization for Novel Soft Materials

新型软材料的受控自由基聚合

• 批准号: RGPIN-2014-05671
• 负责人: Maric, Milan
• 金额: $ 2.11万
• 依托单位: McGill University
• 依托单位国家: 加拿大
• 项目类别: Discovery Grants Program - Individual
• 财政年份: 2017
• 资助国家: 加拿大
• 起止时间: 2017-01-01 至 2018-12-31
• 项目状态: 已结题
• 来源: https://www.nserc-crsng.gc.ca/ase-oro/Details-Detailles_eng.asp?id=638320
• 关键词: Controlled; Radical; Polymerization; Novel; Soft

The research program's broad objective is to synthesize, characterize and process novel block, random and gradient copolymers for tailored stimuli-responsive polymers to organic photovoltaic/light emitting diode (OPV/OLED) materials. We have applied state-of-the-art controlled radical polymerization (CRP) techniques to achieve the requisite microstructure vital for such applications. CRP approaches the control of microstructure found in truly "living" polymerization methods without the exhaustive purification, functional group protection and air-free conditions required of the latter. Further, CRP can link different blocks and/or monomers which otherwise could not achieved by ionic polymerization and offers the possibility of controlled polymerization in dispersed aqueous media. This versatility allows an unprecedented myriad of possible combinations to achieve desired nano-structured materials. In particular, we use a CRP technique termed nitroxide mediated polymerization (NMP), which has some favourable characteristics compared to other CRP methods. For example, it does not require metallic-containing catalysts or sulfur-based chain transfer agents that may remain as impurities which may affect the performance of stimuli-responsive biomedical materials and organic electronic materials. A traditional drawback to NMP was its restriction to the polymerization of styrenic monomers – this has been largely lifted by the use of second-generation alkoxyamine initiators such as BlocBuilder, which has enabled the homopolymerization of acrylates and the polymerization of methacrylate-rich compositions by using a small amount of co-monomer (typically styrenic ~ 5-10 mol%). We have examined controlling co-monomers that have added functionality such as the carbazole-functional controlling co-monomer (eg. VBK) to impart electron-donating/fluorescent properties in stimuli-responsive poly(methacrylates). We applied NMR and ESR to identify species and understand radical copolymerization kinetics. Notably, we found radical reactivity ratios were pivotal in determining how little co-monomer was necessary to maintain a controlled methacrylate polymerization with BlocBuilder initiators. Extending our scope to OPV/OLED applications, we have begun examining electron-acceptor groups in the controlling co-monomer, such as oxadiazoles. We have recently found that not all styrenic co-monomers are effective as controllers for methacrylates, even if the homopolymerizations were controlled. A short-term objective is thus to determine the effect of co-monomer donor/acceptor functionality on methacrylate-rich NMP via a pseudo-Hammett parameter analysis, which will enable how to incorporate such functionality into the desired poly(methacrylate).The longer-term goal for pursuing the electron-donor/acceptor side chain polymers is to take advantage of their easier processability and to self-assemble them into well-ordered domains not necessarily found in the typically stiff, lamellar main-chain polymers associated with OPV/OLEDs. Our initial studies will examine the combination of donor-acceptor block copolymers that could be applied as a water-borne latex, followed by selective removal of the poly(methacrylate) domain (eg. via photolithography). Further, domain amplification and epitaxial growth that has been applied in other block copolymer systems will be attempted as few studies have addressed directed self-assembly of side-chain donor/acceptor copolymers, despite reports of the critical role of morphology on device performance. The program focus on stimuli-responsive and OPV/OLED materials via NMP is a unique niche and will provide HQP (2 PhDs) with synthetic and processing skills that are portable to many vital sectors of the Canadian economy.

该研究计划的广泛目标是合成，表征和加工新型嵌段，无规和梯度共聚物，用于定制有机光伏/发光二极管（OPV/OLED）材料的刺激响应聚合物。我们采用了最先进的可控自由基聚合（CRP）技术，以实现这些应用所必需的微观结构。CRP接近在真正的“活性”聚合方法中发现的微观结构的控制，而无需后者所需的彻底纯化、官能团保护和无空气条件。此外，CRP可以连接不同的嵌段和/或单体，否则不能通过离子聚合实现，并提供在分散的水性介质中的受控聚合的可能性。这种多功能性允许前所未有的无数可能的组合，以实现所需的纳米结构材料。特别是，我们使用的CRP技术称为氮氧化物介导的聚合（NMP），它有一些有利的特点相比，其他CRP方法。例如，它不需要含金属的催化剂或硫基链转移剂，这些催化剂或硫基链转移剂可能作为杂质保留，这些杂质可能影响刺激响应性生物医学材料和有机电子材料的性能。NMP的传统缺点是其对苯乙烯类单体聚合的限制-这在很大程度上通过使用第二代烷氧基胺引发剂如BlocBuilder而得以解除，BlocBuilder通过使用少量共聚单体（通常为苯乙烯类~ 5-10摩尔%）实现了丙烯酸酯的均聚和富含甲基丙烯酸酯的组合物的聚合。我们已经研究了具有添加的官能度的控制共聚单体，例如咔唑官能控制共聚单体（例如，VBK）在刺激响应性聚（甲基丙烯酸酯）中赋予电子供体/荧光性质。我们应用NMR和ESR来鉴定物种并理解自由基共聚动力学。值得注意的是，我们发现自由基的竞聚率是关键，在确定有多少共聚单体是必要的，以保持可控的甲基丙烯酸酯聚合与BlocBuilder引发剂。将我们的范围扩展到OPV/OLED应用，我们已经开始研究控制共聚单体中的电子受体基团，例如恶二唑。我们最近发现，并非所有的苯乙烯类共聚单体作为甲基丙烯酸酯的控制剂都是有效的，即使均聚反应是受控的。因此，短期目标是通过伪Hammett参数分析确定共聚单体供体/受体官能度对富甲基丙烯酸酯NMP的影响，这将使得能够如何将这样的功能结合到所需的聚追求电子给体/受体侧链聚合物的长期目标是利用它们更容易加工的优点，并将它们自组装成良好的聚合物。有序域不一定存在于与OPV/OLED相关的典型刚性层状主链聚合物中。我们的初步研究将检查可以作为水性胶乳应用的供体-受体嵌段共聚物的组合，然后选择性去除聚（甲基丙烯酸酯）结构域（例如，通过光刻）。此外，域放大和外延生长，已被应用在其他嵌段共聚物系统将尝试很少的研究已经解决了定向自组装的侧链供体/受体共聚物，尽管报告的关键作用的形态器件的性能。该计划通过NMP专注于刺激响应和OPV/OLED材料是一个独特的利基市场，并将为HQP（2个博士学位）提供合成和加工技能，这些技能可移植到加拿大经济的许多重要部门。