Organocatalysis In Polysiloxane Gels:a Magnetic-Stir-Bar Encapsulated Catalyst System Prepared By Thiol-Ene Photo-Click Immobilization

Immoblilized organocatalysts which are immoblized on some solid matrixes to facilitate catalyst regeneration and recycle. Immobilized organocatalysts can improve the stability of the catalyst, reduce wastes and emissions, which are benificial for the environment and large-scale continuous production. Besides that, we also describe a new mesogen-jacketed liquid crystal polymer (MJLCP) system, poly(vinyl benzoate)-backbone MJLCP, which is synthesized by solution polymerization and bulk photopolymerization methods respectively. This thesis can be divided into two parts:1. This thesis presents a facile thiol-ene photo-click chemistry method to prepare magnetic stir bar-encapsulated polysiloxane-based organocatalyst gels under benign conditions, meanwhile develops a Stir Bar-Encapsulated Catalysis (SBEC) technique. Through thiol-ene addition chemistry, we graft olefin-terminated organocatalysts (i.e. MacMillan catalyst, Proline catalyst, and N-heterocyclic carbene catalyst) on poly[3-mercaptopropylmethylsiloxane], which is further photo-crosslinked to coat the embedded magnetic stir bar. The prepared magnetic stir bar-encapsulated polysiloxane-based organocatalyst gels can be put into reaction flasks to perform stirring and catalysis functions at the same time. The most important benefit of SBEC technique is to infinitely simplify the catalyst/product separation procedure to using a simple stir-bar-retriever, even without any precipitation/filtration steps. The catalytic performances of three different organocatalyst gels applied in asymmetric Diels-Alder reaction, asymmetric aldol reaction and benzoin condensation reaction respectively are also examined herein.2. Previously reported polymer backbone structures of mesogen jacketed liquid crystalline polymers (MJLCPs) to date are limited to polyacrylate, polystyrene, polyacetylene, polysiloxane, polythiophene and polynorbornene. In this thesis, we describe a new system, poly(vinyl benzoate)-backbone MJLCPs which are synthesized by solution polymerization and bulk photopolymerization methods respectively. Due to the low reactivity of vinylbenzoate group, we can not achieve a high degree of polymerization. Ironically, benefiting from this low reactivity disadvantage, we successfully prepare two loosely cross-linked MJLCP (xMJLCP) films homogeneous-aligned and homeotropic-aligned respectively for the first time, by UV-illumination on a unidirectional oriented mixture of vinylbenzoate monomers, crosslinkers and photo-initiators to perform polymerization and cross-linking at the same time, which are however extremely difficult for traditional much more reactive acrylate-type or styrene-type MJLCPs’ precursor monomers due to the inevitable spontaneous thermal-polymerization reactions occurring at high temperatures.