Creating Silicones: Exerting Control at Interfaces

尽管有机硅聚合物比有机替代品成本更高，但由于其独特的界面行为，它们几乎在发达经济体的每个技术领域都有应用。由于缺乏有效的合成，大多数商用有机硅聚合物在分子量、分支的频率和类型、官能团的分布和网络结构方面都是不明确的混合物。推动研究计划的假设是，精确结构的有机硅聚合物将提高我们加强界面的能力，从而产生具有增强性能的更高价值的材料。除了纯有机硅外，还将制备具有新的亲水性功能的新型聚合物，以增强我们控制非均相界面的能力。所提出的研究结果将是新的合成策略，导致新型有机硅聚合物的应用范围从自润滑隐形眼镜表面到热稳定的LED圆顶。

In spite of their higher cost than organic alternatives, silicone polymers are found in almost every technological area of developed economies because of their unique interfacial behavior. Lacking efficient syntheses, most commercial silicone polymers are ill-defined mixtures with respect to molecular weight, frequency and type of branching, distribution of functional groups and network structures. The hypothesis driving the research program is that silicone polymers of precise structure will improve our ability to reinforce interfaces, leading to higher value materials with enhanced properties. In addition to pure silicones, new polymers with new hydrophilic functionalities will be prepared that can enhance our ability to control heterogeneous interfaces. The outcomes of the proposed research will be new synthetic strategies leading to novel silicone polymers with applications ranging from self-lubricating contact lens surfaces to thermally stable LED domes. New strategies to use the Piers-Rubinsztajn reaction (PR, R3SiH + R'OSilicone -> R3SiOSilicone (or R'OAr -> R3SiOAr) in the presence of B(C6F5)3) to create novel materials was an important outcome of the last 5 years. Structure matters! Small structural differences in the head group of branched silicone surfactants led to large changes in surface activity. This concept will be extended to yield a library of complex 3D silicone structures, including bottlebrush polymers, that will be assembled from precise dendrons in a mix and match' manner. Tuning behavior at interfaces requires new routes to hydrophilically modified silicones. New metal free strategies to link silicone to small and polymeric hydrophiles, particularly those based on natural materials, using xanthates, hydrazones and additionalmetal free click chemistry will be developed with hydrophiles. Hydrophiles will include lignin and saccharides such as guar and hyaluronic acid because they are associated with biocompatible surfaces. Green composites will be formed using these principles, by diluting of silicones with natural, renewable, biodegradable materials. Achieving these outcomes requires thorough characterization of the polymers and composites prepared in this program. This will include physical testing (modulus and extension at break), surface analysis (adhesion (peel tests), XPS), in addition to molecular characterization (NMR, MS). An important aspect of reaching the proposed scientific objectives is continued training of HQP (last 6 years: 32 undergrad, 8 MSc, 13 PhD students, 8 PDFs) in technical areas, such as polymer/materials synthesis and characterization. This will enhance the HQP's ability to attain employment in academia and industry, particularly the 3 silicone and the many polymer companies located in Southern Ontario. Training in polymer processing is required for Canada's continued economic growth.