Controlled Radical Polymerization for Novel Soft Materials

可逆失活自由基聚合(RDRP)是近二十年来出现的一种可替代活性聚合(LP)方法来制备具有可控微观结构的聚合物。几乎所有的现代技术都依赖于具有明确分子性质的材料；聚合物对于微电子(直接自组装、光刻)、生物材料(例如。控制释放(薄膜)和结构材料(涂层、密封剂、热塑性弹性体)。与LP相比，RDRP的主要优势在于它模拟了LP的表面特征(聚合度与转化率的线性递增、窄的分子量分布、活性链端)，而不需要对后者进行严格的纯化和所需的条件。此外，RDRP可以在水中进行，并结合在一起的单体，否则不能通过LP进行。该研究计划应用RDRP来开发新材料，主要使用一种称为氮氧化物介导聚合(NMP)的变体，这种方法避免了金属配体催化剂残留物或其他常见RDRP工艺中存在的硫基链转移剂导致的树脂变色。未来5年计划的重点是使用NMP：1)将锥形/梯度共聚物定向自组装成微电子图案化表面；2)通过点击化学合成水凝胶和自愈聚合物的新功能材料；3)合成用于动力学水合物抑制剂/促进剂的两亲性嵌段共聚物。定向自组装已经被用于介电材料(IBM的气隙技术)，并被认为是光刻的后续微电子技术，在光刻中，通过缩小波长来获得更小的特征尺寸变得更加困难。我们将使用梯度共聚物代替嵌段共聚物，因为在从一个嵌段到另一个嵌段时，可以避免中间的纯化步骤。不过，界面更弥漫着有趣的自组装挑战。我们将探索如何在以受控方式编程界面宽度的同时获得更小的特征尺寸。NMP在采用点击化学和水凝胶等正交官能化方法方面落后于其他RDRP方法。我们还将研究基于新设计的引发剂改性，这种设计可以使甲基丙烯酸酯均聚，并干净地与其他单体家族交叉，产生新的材料。同时，我们还将采用正交功能化策略，如点击化学，以获得比NMP更早可能获得的更广泛的材料性质。最后，我们最近报道了两亲性水溶性嵌段共聚物作为动力学水合物抑制剂(KHIS)是相当有效的。水合物的形成是天然气管道保流面临的最关键问题之一。我们最初的尝试将用于发展结构-性质关系，并最终设计可生物降解的无毒KHIS。

Reversible de-activation radical polymerization (RDRP) has emerged over the past two decades as a viable alternative to living polymerization (LP) methods to produce polymers with controlled microstructure. Virtually all modern technologies depend on materials with defined molecular properties; polymers are critical for microelectronics (directed self-assembly, lithography), biomaterials (eg. controlled release, membranes) and structural materials (coatings, sealants, thermoplastic elastomers). RDRP's key advantage over LP is it mimics superficially hallmarks of LP (linear progression of degree of polymerization vs. conversion, narrow molecular weight distribution, active chain ends) without applying the stringent purification and conditions required of the latter. Further, RDRP can be done in water and combine monomers that otherwise could not be done by LP. The research program applies RDRP to develop new materials, using mostly a variant termed nitroxide mediated polymerization (NMP), which avoids resin discolouration  from metallic ligand catalyst residues or sulfur-based chain transfer agents that are present in other common RDRP processes. The program planned for the next 5 years will focus on using NMP for: 1) directed self-assembly of tapered/gradient copolymers towards patterning surfaces for microelectronics; 2) new functional materials via click chemistry for hydrogels and self-healing polymers; 3) synthesizing amphiphilic block copolymers for application in kinetic hydrate inhibitors/promoters. Directed self-assembly is already exploited in dielectric materials (IBM's AirGap technology) and is considered the successor microelectronics technology to photolithography, where it becomes more difficult to obtain smaller feature sizes by shrinking the wavelength. We will use gradient copolymers instead of block copolymers as an intermediate purification step is avoided when crossing from one block to the other. However, the more diffuse interface interesting self-assembly challenges. We will explore how to obtain smaller feature sizes while programming the interfacial width in a controlled manner. NMP has lagged behind other RDRP methods in adopting orthogonal functionalization methods like click chemistry and hydrogels. We will also examine initiator modification based on new designs which can homopolymerize methacrylates and cross-over cleanly to other monomer families, yielding new materials. Concurrently, we will also adopt orthogonal functionalization strategies like click chemistry to access a wider range of material properties than that was possible earlier by NMP. Finally, amphiphilic water-soluble block copolymers as kinetic hydrate inhibitors (KHIs) were recently reported by us to be quite effective. Formation of hydrates is one of the most critical problems facing flow assurance in gas pipelines. Our initial forays will be used to develop structure-property relationships and eventually design biodegradable non-toxic KHIs.