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Kajiyama, Tisato,Kikuchi, Hirotsugu,Jeong, Hwan Kyeong,Jeong, Noh Hee,Nam, Ki Dae 한국공업화학회 1998 Journal of Industrial and Engineering Chemistry Vol.4 No.3
The relationship between the polymer molecular weight and the electro-optical properties was investigated for the polymer/liquid crystal (LC) composite film prepared by a solvent-induced phase separation method. Poly(methyl methacrylate) (PMMA) and poly(diisopropyl fumarate) (Pdi-iPF) with significantly different weight-average molecular weight (M_w) were used as the matrix for the Polymer/LC composite film. It is confirmed from morphological observation by scanning electron microscope (SEM) that the size of LC channel or domain was strongly dependent on M_w of PMMA and Pdi-ipF. With increasing M_w in PMMA/LC composite film, the switching hysteresis was decreased due to a decrease of the compatibility at the polymer-LC interface. The hysteresis in (Pdi-iPF/LC) composite film was not detected for electro-optical switching and this result is not changed with MW of Pdi-iPF.
Kajiyama, Tisato,Kikuchi, Hirotsugu,Jeong, Hwan Kyeong,Jeong, Noh Hee 한국공업화학회 1997 Journal of Industrial and Engineering Chemistry Vol.3 No.4
Fluorine type low molecular weight liquid crystal(LC) dependence of the hysteresis of electrooptical switching and the phase-separated structure was investigated for the (polymer/LC) composite film cast from a uniform solution. It is confirmed from morphological observation by scanning electron microscopy (SEM) that the LC domain size of the composite film containing fluorine type LCs remarkably decreased. The interfacial phase-mixing behavior between polymer and LC components was evaluated by the time domain method based on the dielectric composite model of the (polymer/LC) composite film, the temperature dependence of the composite film and the atomic force microscopy (AFM). The hysteresis of electro-optical switching for the composite film was strongly dependent on the LC type. When the polymer and the LC were not compatible such as (Poly(methyl methacrylate)(PMMA)/fluorine type LC) composite system, the static hysteresis of the electro-optical switching for the composite film was not observed. It is found that the phase-mixing at the polymer-LC interface upon applying an a.c. electric field had great effect on the electro-optical switching hysteresis of the composite film.
Activated Physical Properties at Air-Polymer Interface
Kajiyama, Tisato The Polymer Society of Korea 2007 Macromolecular Research Vol.15 No.2
The surface molecular motion of monodisperse polystyrene (PS) films was examined using scanning vis-coelasticity microscopy (SVM) in conjunction with lateral force microscopy (LFM). The dynamic storage modulus, E', and loss tangent, $tan\delta$, at a PS film surface with number-average molecular weights, $M_n$, smaller than 30 k were found to be smaller and larger than those for the bulk sample, even at room temperature, meaning that the PS surface is in a glass-rubber transition or fully rubbery sate at this temperature when the $M_n$ is small. In order to quantitatively elucidate the dynamics of the molecular motion at the PS surface, SVM and LFM measurements were performed at various temperatures. The glass transition temperature, $T_g$, at the surface was found to be markedly lower than the bulk $T_g$, and this discrepancy between the surface and bulk became larger with decreasing $M_n$. Such an intensive activation of the thermal molecular motion at the PS surfaces can be explained in terms of an excess free volume in the vicinity of the film surface induced by the preferential segregation of the chain end groups.