Crystallization Studies of Highly Monodisperse Oligomeric Poly(Ethylene Oxide)

Abstract

Poly(ethylene oxide) is one of the most intensively studied polymers in terms of crystallization, because of its linear structure. In this thesis the chapters are organized in a self-contained fashion, with a general introduction and a brief conclusion. We introduce the purification and characterization of highly monodisperse PEO oligomers, and the analysis of their melting and crystallization behaviours. Through evaporative purification, we have been able to purify low molecular weight PEO, and achieve a polydispersity index six times better than the neat commercial sample, as measured by mass spectroscopy. Melting temperatures are obtained using differential scanning calorimetry. Based on the Gibbs Thomson relation, we claim that during crystallization, some purified PEO samples can form crystal lamellae not only with extended chains, but also with once-folded chains, which is normally not expected for polymers with such short chain lengths. The fact that we are able to control the melting temperature through annealing treatment on the crystal validates our chain-folding model of folded and extended chains.