Polymer Science and Technology

Biography

Prof Hazel Assender has led a research activity at the Department of Mate­rials, University of Oxford, since 1996, with a focus in the area of thin films and coatings both of polymer materials or onto polymer substrates. She graduated from the University of Cambridge, following this with a PhD, and two years of postdoc in the Department of Materials Science & Metallurgy in Cambridge before moving to an academic post in Oxford. Her research spans fundamental studies of the thin film and near-surface properties of polymers, through to materials engineering of thin films and device struc­tures in large area on polymer substrates. Particular areas of interest include roll-to-roll deposition, gas barriers, photovoltaics, and transistors/circuits. Her research has a technology-facing approach bringing underpinning sci­entific understanding to development of materials and technologies that integrates research relevant to industrial processing such as scale-up of manufacture with the development of new materials and structures.

Abstract

The near-surface properties of thermoplastic polymers are of interest, particularly where thin film coatings or other structures are to be subsequently applied. Previous work by AFM and ellipsometry has established that the glass-transition temperature in the near-surface region is depressed by up to tens of Kelvin, leaving the surface vulnerable to deformation and penetration during coating processes such as metallization. We have also shown that the near-surface region of PET shows enhanced crystallinity. This paper will report our AFM studies of PET, PEN and copolymers thereof and the near-surface crystallization that can be induced by annealing at temperatures at which the surface molecular segments are mobile, but those in the bulk underneath are not. We demonstrate the characteristic morphologies associated with the surface crystallization and changes in the crystal orientation as growth proceeds. Comparison is made with other polymer systems we have studied including near-surface phase separation and unique crystal morphologies at the surface in polyurethanes.