Design, synthesis and properties of comb copolymers with variable grafting density by controlled radical polymerization.

摘要

This thesis presents the results of some experiments at the present limits of controlled radical polymerization. More specifically, atom transfer radical polymerization (ATRP) was used to polymerize 2-hydroxyethyl acrylate and 2-hydroxyethyl methacrylate, monomers whose polymerizations were heretofore not controlled in their unprotected forms due to the nature of the polar side group. Molecular weights of the final polymers were predicted based on the ratio of consumed monomer to initiator (Δ[M]/[I]) and their polydispersities were low (M_w/M_n 1.3). The polymerization of the highly nonpolar lauryl acrylate was also controlled. The main achievement of the thesis is the design and synthesis of well-defined graft copolymers. We first experimented with the traditional method of preparing macromonomers, using ATRP rather than anionic or group transfer techniques, combined with conventional copolymerization to prepare the graft copolymeric hydrogels, poly(N-vinyl pyrrolidinone-g-styrene). The most interesting results, however, were provided using the grafting from approach. A well-defined macroinitiator was first prepared using ATRP, followed by transformation chemistry to generate an initiation site at every repeat unit in the main chain. Subsequent ATRP from these sites produced densely grafted copolymers with molecular weights in excess of 106, M_w/M _n 1.3. Although, the first grafts were prepared with styrene, primarily acrylates were used as the side chains which comprise >95% of the copolymer composition. Striking properties were observed in these materials, which can be resolved as individual molecules in thin films. Undergraduate experiments in ATRP were also developed and applied in the organic laboratory course at CMU.