Structure Formation Mechanism of Isoporous Block copolymer Membranes
type: CreativeWork
description: This thesis deals with the microphase separation of poly(styrene-b-vinylpyridine) block copolymers in highly concentrated solutions induced by evaporation of a binary solvent mixture of a high and low boiling solvent. During self-assembly and non-solvent induced phase separation by immersion in water, asymmetric membranes consisting of a thin top layer with closely packed pore channels with diameters below 100 nm above a much thicker macroporous supporting layer are formed. These membranes can be used for filtration purposes of, e.g., biomolecules. The aim of this thesis was to discover the fundamental principles according to which these materials are developed in order to optimize the preparation conditions for future large-scale membrane productions. The first part of the thesis focused on the experimental and theoretical investigation of the compositional changes of the polymer/binary solvent mixture during evaporation. The calculated polymer/solvent volume fractions were used to construct compositional trajectories in a ternary phase diagram. The calculations revealed a peculiar region of the phase diagram where the PVP-volume fraction is sufficiently high to induce morphological transitions. The block copolymer morphologies resulting from microphase separation in this region were systematically investigated by AFM and SEM as a function of polymer concentration, solvent composition and evaporation times before immersion in water. Several characteristic morphologies during solvent evaporation were identified, such as spinodal networks (SpN), sphere percolation networks (SN), disordered cylinders (DC) and the desired highly symmetric pore network (PN). A general structure growth during film formation was observed and further confirmed by in situ synchrotron SAXS measurements. From these investigations basic conclusions for optimized membrane preparation in terms of solvent and polymer composition and immersion times could be drawn. Porous membrane formation was sh…
abstract: This thesis deals with the microphase separation of poly(styrene-b-vinylpyridine) block copolymers in highly concentrated solutions induced by evaporation of a binary solvent mixture of a high and low boiling solvent. During self-assembly and non-solvent induced phase separation by immersion in water, asymmetric membranes consisting of a thin top layer with closely packed pore channels with diameters below 100 nm above a much thicker macroporous supporting layer are formed. These membranes can be used for filtration purposes of, e.g., biomolecules. The aim of this thesis was to discover the fundamental principles according to which these materials are developed in order to optimize the preparation conditions for future large-scale membrane productions. The first part of the thesis focused on the experimental and theoretical investigation of the compositional changes of the polymer/binary solvent mixture during evaporation. The calculated polymer/solvent volume fractions were used to construct compositional trajectories in a ternary phase diagram. The calculations revealed a peculiar region of the phase diagram where the PVP-volume fraction is sufficiently high to induce morphological transitions. The block copolymer morphologies resulting from microphase separation in this region were systematically investigated by AFM and SEM as a function of polymer concentration, solvent composition and evaporation times before immersion in water. Several characteristic morphologies during solvent evaporation were identified, such as spinodal networks (SpN), sphere percolation networks (SN), disordered cylinders (DC) and the desired highly symmetric pore network (PN). A general structure growth during film formation was observed and further confirmed by in situ synchrotron SAXS measurements. From these investigations basic conclusions for optimized membrane preparation in terms of solvent and polymer composition and immersion times could be drawn. Porous membrane formation was sh…
author: Stegelmeier, Corinna
date published: 2015-07-23
date modified: 2026-07-27T18:49:46Z
provider: Universität Bayreuth
publisher: Networked Digital Library of Theses and Dissertations
type: WebPage
source organization: Universität Bayreuth