Investigation Of Polymer Self-assemblies Through RAFT Polymerization

Reversible addition-fragmentation-transfer (RAFT) polymerization is a widely applied controlled/living radical polymerization (CRP) techniques. It is arguably the most versatile technique in terms of broad monomer selection and wide reaction conditions. RAFT polymerization provides a powerful method to synthesize various specially structured polymers, such as graft, block, star, comb and cycle, as well as many kinds of polymeric materials with significant applications. This dissertation describes several research results in the synthesis of polymeric materials based on RAFT polymerization. The main results obtained in this thesis are as follows:1. Through reversible addition-fragmentation chain transfer (RAFT) polymerization of t-butyl acrylate (tBA) with S-1-dodecyl-S′-(ɑ,ɑ′-dimethyl-ɑ,ɑ′-acetic acid) trithiocarbonate (DMP) as chain transfer agent and RAFT copolymerization of 2-dimethylaminoethyl methacrylate (DMAEMA) with poly(ethylene glycol) methyl ether methacrylate (PEGMEMA), block-comb copolymer of PtBA-b-P(PEGMEMA-co-DMAEMA) was prepared. After the self-assembly of PtBA-b-P(PEGMEMA-co-DMAEMA) into core-shell spherical micelles, P(PEGMEMA-co-DMAEMA) segments of the shell was crosslinked with 1, 2-bis(2-iodoethoxy)ethane and the core of PtBA was selectively hydrolysized with trifluoroacetic acid. Thus, zwitterionic shell-crosslinked micelles with positively charged outer shell and negatively charged inner core were obtained. Dynamic light scattering, transmission electron microscope, Zeta potential measurement and nuclear magnetic resonance were used to confirm the formation of the zwitterionic shell-crosslinked micelles.2. Yolk/shell and nanowire aggregates of poly(acrylic acid)-b-polystyrene (PAA-b-PS) were successively observed during RAFT dispersion polymerization with trithiocarbonate-capped polyacrylic acid (PAA-DMP) as macromolecular chain transfer agent (CTA) through polymerization-induced self-assembly and re-organization. They were formed by tuning the ratio of PAA-DMP to AIBN and the length of PAA-DMP. This will be useful for application. When the length of PAA-DMP was long, the aggregate morphology changed from complexity to simplicity, i.e. from yolk-shell, vesicle, nanowire to spherical micelle. The structures were stable. When the PAA-DMP was shorter, the structures were not stable as aforementioned. So the length of PAA-DMP is very important. The PAA-DMP is much longer, the polymeric assemblies are more stable and uniform. The variation of the morphology was also achieved by the modulating the feed ratio of PAA-DMP to DMP.