Controlling effective interactions and spatial dispersion of nanoparticles in multiblock copolymer melts

Abstract

The microscopic Polymer Reference Interaction Site Model theory is employed to study, for the first time, the effective interactions, spatial organization, and miscibility of dilute spherical nanoparticles in non-microphase separating, chemically heterogeneous, compositionally symmetric AB multiblock copolymer melts of varying monomer sequence or architecture. The dependence of nanoparticle wettability on copolymer sequence and chemistry results in interparticle potentials-ofmean force that are qualitatively different from homopolymers. An important prediction is the ability to improve nanoparticle dispersion via judicious choice of block length and monomer adsorption-strengths which control both local surface segregation and chain connectivity induced packing constraints and frustration. The degree of dispersion also depends strongly on nanoparticle diameter relative to the block contour length. Small particles in copolymers with longer block lengths experience a more homopolymer-like environment which renders them relatively insensitive to copolymer chemical heterogeneity and hinders dispersion. Larger particles (sufficiently larger than the monomer diameter) in copolymers of relatively short block lengths provide better dispersion than either a homopolymer or random copolymer. The theory also predicts a novel widening of the miscibility window for large particles upon increasing the overall molecular weight of copolymers composed of relatively long blocks. The influence of a positive chi-parameter in the pure copolymer melt is briefly studied. Quantitative application to fullerenes in specific copolymers of experimental interest is performed, and miscibility predictions are made.

An extremely uniform dispersion of MWCNTs in olefin block copolymers significantly enhances electrical and mechanical performances

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Coarse-Grained Models for Automated Fragmentation and Parametrization of Molecular Databases

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Entropic depletion in colloidal suspensions and polymer liquids: role of nanoparticle surface topography

“…Multiple complementary strategies have been developed to counteract this including tuning chemistry to favor limited matrix-particle adsorption, [17][18][19][20] attaching chain molecules to provide steric stabilization, [21][22][23][24] and introducing packing frustration via sequence-designed AB copolymers. [25][26][27][28][29] A far less explored approach to reduce, control or eliminate depletion-induced clustering is to modify the particle surface by incorporating roughness. Since rough spheres present less exclusion volume to the matrix than their smooth analogs, a diminished contact depletion attraction is expected.…”