Synthesis Of Block Copolymers Via Controlled Polymerization Initiated By ITX-Containing Precursor And Their Applications

Block copolymer has gained much interest due to its combination of properties of each block. The main purpose of modern polymer synthesis is to prepare polymer with special topology and property through design to control components, molecular weights and polydispersities in polymerization processes. Up to the present, living polymerization has been demonstrated to be an effective way to prepare block copolymer, and also macroinitiator has been used to produce block copolymer. In this dissertation, block copolymers were synthesized by a controlled polymerization initiated by commercial hydrogen abstract ing photoinitiator isopropyl thioxanthone (ITX) based on a reversible coupling-fragmentation mechanism. The detailed procedure was showed below. Firstly, a dormant group containing macroinitiator was synthesized by a photo polymerization initiated by a binary system of ITX and EDAB. Secondly, block copolymers were synthesized by simply heating the mixture of macroinitiator and monomer in a bulk, solution and emulsion system. The polymerization initiated by the reversible coupling-fragmention mechanism mentioned above was characterized the controlled polymerization, similar as the controlled polymerization mediated by N-O agent. Thus a simple and cheap method of preparing block copolymer can be achieved by using commercial hydrogen abstract photo initiator. Furthermore, by applying the resultant copolymer in a breath figure procedure, honeycomb structure films were prepared.The main contents of the present work can be summarized as follows:1. The dormant group containing precursor was synthesized by photo polymerization initiated by hydrogen abstract photo initiator. The UV spectrum was applied to identify the existence and concentration of dormant group. The effects of polymerization upon concentration of dormant group were studied. The precursors which were applied in following polymerization can be produced in a simple method.2. The bulk polymerization, solution polymerization and emulsion polymerization of styrene was initiated by a oil soluble precursor poly(methyl methacrylate) contained ITX dormant group in order to prepared PMMA-b-PSt block copolymer, and the reinitiation process was studied. During the polymerization the molecular weight was increased almost linearly with the increasing of styrene conversion, while the polydispersities were decreased, which was somewhat analogous to the controlled polymerization. The UV spectrum and FTIR spectrum analysis demonstrate the presence of PMMA-b-PSt block copolymer. The comparison experiments of convention emulsion polymerization and bulk polymerization initiated by precursor showed that higher monomer conversion and higher molecular weight can be achieved in emulsion polymerization.3. The PMV-b-PSt block copolymer was synthesized by solution polymerization of styrene initiated by PMV-ITXH macroinitiator. The honeycomb structure films were prepared by casting polymer solution according to a breath figure mechanism. The average pore diameter of the porous film was estimated at around 250nm, probably close to the lowest value of pore sizes that can be generated using breath figure approach, and comparable to that obtained with an amphiphilic block copolymer synthesize by living radical polymerization process. The polymer concentration, temperature, environment humidity and solvent can affect the casting process.4. The PMV-b-PMMA block copolymer microspheres with the diameter around 300nm were prepared by a soap free emulsion initiated by the water soluble PMV-ITXH macroinitiator. The amphiphilic block copolymer formed during the polymerization initiated by PMV-ITXH acted as emulsifier to sustain colloids. The aminolysis degree of macroinitiator can affect the stability of emulsion and the polymerization rate of monomer.