In the presentation we focus on three topics related to soft matter physics, especially to polymer physics revealed by neutron scattering.
One is polymer crystallization under flows. It is well know that when polymers are crystallized under shear flow or elongational flow, characteristic morphology, the so-called shish-kebab, is often observed. It is believed that the morphology is a structure origin of ultra-high modulus fiber, and hence many studies were performed by various groups. Our group also studied the formation mechanism of the shish-kebab using small-angle neutron and X-ray scattering.
The second topic is on anomalous thermal properties of polymer thin films. Resent extensive studies have revealed that glass transition temperature Tg of polymer thin films decreases with film thickness when the interactions between polymer thin film and substrate are not strong. We have investigated structure and dynamics of polymer thin films using quasielastic neutron scattering and neutron reflectivity to find that the heterogeneity of thin films is the origin of the anomalous properties.
The third topic is the dynamics of poly(vinyl alcohol) (PVA) studied by small-angle neutron scattering and neutron spin-echo technique in nm scale. This polymer forms physically cross-linked gels in many solvents and also chemically cross-linked gels through a reaction with many kinds of cross-linkers. We have studied three types of PVA gels and separated the fluctuations into dynamics and static contributions to see the role of dynamics in their properties.