Induction and arrest of block polymer self-assembly in selectivity-controlled environments

Abstract

In this thesis, we propose a method to control the size and morphology of block polymer phase behaviors, and to prepare new polymer structures by varying the amount and types of selective additives. Systems containing selective additives such as a corresponding homopolymer, selective solvent, molecules with intermolecular interactions and non-solvents are proposed, and were used to investigate the effect of additives on polymerization-induced nanostructuring. The phase behavior of the block polymer materials was modulated by adding polylactide homopolymer (PLA-OH) and acetonitrile (MeCN) to a reaction mixture of styrene (S), divinylbenzene (DVB), polylactide macro-chain transfer agent (PLA-CTA). As a result, micro- and macrophase separation and self-assembly processes during polymerization were controlled, resulting in block polymer materials with controlled sizes and various morphologies. Also, by adding tannic acid, which forms intermolecular interactions with the PLA block, to a solution containing polystyrene-b-polylactide (PS-b-PLA), we studied how the chirality match between the polymer and additive molecules affected self-assembly behavior. Finally, we proposed a method of preparing a hierarchical structure, by inducing independent micro- and macro phase separation. A high internal phase emulsion (HIPE) was prepared by adding water as a non-solvent to a reaction mixture containing S, DVB and PLA-CTA, and then the water-oil interface was stabilized by the addition of a surfactant. By proceeding sequentially with the PIMS process and hyper-cross-linking, a hierarchically porous polymer with micro-, meso- and macroporous structures was successfully prepared.