(692a) Mesoscale Simulations of Block Copolymers and Their Blends

Microphase separated polymers exhibit unique properties useful in diverse types of applications such as fuel cells, batteries or protective and breathable barriers. One of promising class of polymers is block copolymers that may have several thermodynamically immiscible components causing the microphase separation that leads to complicated nanometer scale morphologies such as cylinders, lamellae or spheres. We are particularly interested in copolymers with sulfonated polystyrene (sPS) component such as sSIBS or the Li-sPS-POEM copolymer. The sSIBS (sPS-b-polyisobutylene-b-sPS) block copolymer exhibits desirable permeable properties necessary for a breathable barrier while the Li-sPS-POEM (Li-sPS-poly(oxy-ethylene)9 methacrylate) might be used as a single-ion conducting electrolyte in lithium-batteries.

We have used multiscale modeling to develop input parameters for the dynamic density functional method (Mesodyn) followed by the finite element calculation of macroscopic properties. Using this mesoscale approach morphology and the microphase ordering mechanisms were calculated. We will discuss the accuracy of the mesoscale technique to reproduce experimentally known phase diagram of PS-PI (polystyrene-polyisoprene) copolymer and shear-induced transitions of the gyroid and the BCC phases.

We have studied morphology and permeability of symmetric and asymmetric sulfonated, sSIBS copolymers. It is known that addition of polystyrene improves mechanical properties of SIBS copolymer. We will present morphology of sSIBS/PS and sSIBS/IB blends calculated at various ratios of polystyrene and isobutylene in order to optimize permeability and mechanical properties of the materials. We will also present the bulk and the surface morphologies of Li-sPS-POEM copolymer.

Mechanical properties based on mesoscale-calculated morphology were calculated using the self-consistent homogenization theory. This new implementation uses a microstructural approach, as implemented in the AEH3D code, to estimate key anisotropic tensoral properties including the elastic stiffness tensor, based on knowledge of microstructure morphology obtained from mesoscale calculations.