Nonequilibrium morphologies of random block copolymers processed by solvent evaporation

This thesis describes the investigation of solvent evaporation processing of random block copolymers and its effects on morphology. Molecular dynamics simulations were performed on a coarse-grained bead spring model of a generic random block copolymer. A standard Lennard-Jones nonbonded potential and a finitely extensible nonlinear elastic (FENE) bonded potential were used. The model was first characterized without the use of solvent processing by ‘quenching' the polymer. The Lennard-Jones well depth, ?, was increased for one monomer to produce a block copolymer with blocks of different glass transition temperatures. A co-solvent was then added and the evaporation process was carried out by randomly removing solvent particles from the simulation box. The effect of the solvent evaporation process on morphology was investigated and compared to the quenched polymer. Effect of the strength of solvent, evaporation rate, and Lennard-Jones well depth were all looked at. It was concluded that quenching of random block copolymer melts under conditions where one of the blocks is glassy leads to a kinetically arrested morphology. This morphology has a smaller domain size and more extended chain conformation than the morphology when both blocks are nonglassy. Solvent evaporation processing, however, reduces these effects and produces a larger domain size.