MORPHOLOGICAL TRANSFORMATIONS IN POLYMER BRUSHES IN BINARY MIXTURES: DPD STUDY ABSTRACT OF THE THESIS Morphological transformations in polymer brushes in binary mixtures: DPD study

Jianli Cheng, Jianli Cheng, Alexander Neimark
2014 unpublished
Morphological transformations in polymer brushes in a binary mixture of good and bad solvents are studied using dissipative particle dynamics (DPD) simulations drawing on a characteristic example of polyisoprene natural rubber (PINR) in acetone-benzene mixture. A coarse-grained DPD model of this system is built based on the literature experimental data available. We focus on the transformation of dense collapsed brush in bad solvent (acetone) to expanded brush solvated in good solvent (benzene)
more » ... d solvent (benzene) as the concentration of benzene increases. A coarse-grained DPD model of this system is built based on the literature experimental data available. Compared to a sharp globule-to-coil transition observed in individual tethered chains, collapsed-to-expanded transformation in brushes is found to be gradual without a prominent transition point. The transformation becomes more leveled as the brush density increases. At low densities, the collapsed brush is highly inhomogeneous and patterned forming bunches composed of neighboring chains due to favorable polymer-polymer interaction. At high densities, the iii brush is expanded even in the bad solvent due to steric restrictions. In addition, we considered a model system similar to the PINR-acetone-benzene system, but with the interactions between the solvent components worsened to the limit of miscibility. Enhanced contrast between good and bad solvents facilitates absorption of the good solvent by the brush, shifting the collapsed-expanded brush transformation to lower concentrations of the good solvent. This effect is especially pronounced for higher brush densities. iv
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