Fabrication of honeycomb structured porous membranes for biological application

Abstract

This thesis studies the synthesis of diverse architectures of polymers via the reversible addition fragmentation chain transfer (RAFT) polymerisation process that is one of the most novel and versatile controlled polymerisation techniques. Star polymers, comb polymers, amphiphilic block copolymers, and random copolymers were utilised to fabricate porous films with hexagonal arrangement via a ‘bottom-up’ engineering approach, namely a ‘breath figure’ technique. The quality (i.e. pore regularity and pore size) of the films was optimised by controlling casting variables including humidity, airflow, concentration of polymer solution, polymer architecture, molecular weight of polymer, substrate, and casting volume. Porous membranes were chemically crosslinked to improve their mechanical strength if required. Furthermore, chemical surface modification of porous films was performed by grafting desired polymer (i.e. PNIPAAm or PAGA) via RAFT polymerisation. The RAFT groups present in the films play a role as anchoring sites for polymerisation, thus the complex initiator immobilising can be avoided in our system. The desired polymer grafting is able to enhance wettability and provide binding sites for adhesion and proliferation of cells. The topography of ungrafted and grafted films was analysed using optical microscopy, scanning electron microscopy, atomic force microscopy, confocal microscopy, ATR-FTIR, and XPS.