Miscibility of polymer blends
type: CreativeWork
description: In this work an attempt is made to correlate polymer miscibility with diffusion and with molecular interactions. A system with lower critical solubility temperature has been selected, namely polystyrene (PS) and polyvinyl methyl ether (PVME). Most of the published work has been done on polymers in solutions or on solvent cast specimens and therefore on ternary systems. The role of solvent has not yet been fully evaluated and it was of interest to compare the results on solvent cast samples with those prepared by mechanical blending and by diffusion. Molecular interaction is dependent on functional groups present and for this reason experiments have been performed on PVME blends with PS of different levels of sulfonation (SPS). Selective deuteration (d-PS) was used to identify and assign some absorption peaks in the infrared spectra. DSC measurements have shown that only one Tg is present for all blends prepared by solvent casting. It was necessary to use an extreme quenching rate down to liquid nitrogen in order to preserve the high temperature (above 150°C) phase separated structure, represented by two Tg of homopolymers. The mechanically blended system, on the other hand, did not show a single T g of the blend, unless annealed for one day at 110°C. This confirms the results obtained by diffusion studies using light microscopy and neutron reflectivity, that the diffusion rates are extremely slow and therefore do not control the phase formation and separation processes. These experiments also indicate that the microstructures of solvent cast samples and samples prepared by mechanical blending are different. The Tg of mechanical blended polymers indicate, that the composition of diffusion swollen PS does not correspond to the phase diagram measured in solutions, confirming thus the above result. The FTIR studies at different temperatures have shown that changes in spectra of polymer blends, as reported in the literature can be explained by temperature changes in pure…
abstract: In this work an attempt is made to correlate polymer miscibility with diffusion and with molecular interactions. A system with lower critical solubility temperature has been selected, namely polystyrene (PS) and polyvinyl methyl ether (PVME). Most of the published work has been done on polymers in solutions or on solvent cast specimens and therefore on ternary systems. The role of solvent has not yet been fully evaluated and it was of interest to compare the results on solvent cast samples with those prepared by mechanical blending and by diffusion. Molecular interaction is dependent on functional groups present and for this reason experiments have been performed on PVME blends with PS of different levels of sulfonation (SPS). Selective deuteration (d-PS) was used to identify and assign some absorption peaks in the infrared spectra. DSC measurements have shown that only one Tg is present for all blends prepared by solvent casting. It was necessary to use an extreme quenching rate down to liquid nitrogen in order to preserve the high temperature (above 150°C) phase separated structure, represented by two Tg of homopolymers. The mechanically blended system, on the other hand, did not show a single T g of the blend, unless annealed for one day at 110°C. This confirms the results obtained by diffusion studies using light microscopy and neutron reflectivity, that the diffusion rates are extremely slow and therefore do not control the phase formation and separation processes. These experiments also indicate that the microstructures of solvent cast samples and samples prepared by mechanical blending are different. The Tg of mechanical blended polymers indicate, that the composition of diffusion swollen PS does not correspond to the phase diagram measured in solutions, confirming thus the above result. The FTIR studies at different temperatures have shown that changes in spectra of polymer blends, as reported in the literature can be explained by temperature changes in pure…
author: Bhutto, Ali Asghar
language: en
date published: 1999
date modified: 2026-07-24T01:23:28Z
provider: University of Brunel
publisher: Networked Digital Library of Theses and Dissertations
type: WebPage
source organization: Brunel University School of Engineering and Design PhD Theses