Kaoru Adachi

Polymer hybrids of functionalized silsesquioxanes and organic polymers utilizing the sol-gel reaction of tetramethoxysilane

The ternary polymer hybrids were prepared by organic polymers such as poly(2-methyl-2-oxazoline) (POZO) or poly(N-vinylpyrrolidone) (PVP) and aminopropylsilsesquioxane (Cube-aminopropyl) utilizing the sol–gel reaction of tetramethoxysilane (TMOS). The prepared polymer hybrids were characterized by IR, thermogravimetric analysis (TGA), X-ray diffraction (XRD), 1H NMR, scanning electron microscopy (SEM), etc. In this hybrid system, hydrogen-bonding interactions played a critical role in the formation of the transparent polymer hybrids. Polymer hybrids using POZO showed high transparency and homogeneity in a wide range of the feed ratios of POZO to Cube-aminopropyl. On the other hand, in case of polymer hybrids using PVP, higher Cube-aminopropyl ratio brought about the phase separation, indicating the aggregation of the Cube-aminopropyl itself. The homogeneity of ternary polymer hybrids was found to be closely dependent on the difference between strength of hydrogen bonding interaction of polymer and residual silanol groups of silica gel and strength of that of polymer and Cube-aminopropyl. It is also observed that initial decomposition temperature of polymer hybrids was increased with increasing the Cube-aminopropyl ratio.

Dispersion Behavior of Multi-walled Carbon Nanotubes with Pyrene-Containing Linear and Graft Polymers as Non-covalent Surface Modifiers

Various effects on dispersion of multi-walled carbon nanotubes (MWCNTs) in organic solvent and in polymer film by means of pyrene-containing polymeric surface modifiers were investigated. Graft surface modifiers of poly(ethylene oxide) and of polystyrene with pyrene groups were synthesized by radical co-polymerization of corresponding macromonomers and a pyrene-containing methacrylate monomer. The effect of pyrene content on MWCNT dispersion was examined in THF with polymers of different unit ratio of macromonomer to pyrene monomer. The effect of the polymer architecture was explored with a linear polymer having a pyrene end-group and graft polymers having pyrene units. As a result, the dispersibility of MWCNT in THF was improved with increasing pyrene content in the graft polymer and was also improved by a branched architecture of the polymeric non-covalent surface modifier. Preparation of a homogeneously MWCNT dispersed polystyrene film was investigated with a pyrene-containing graft polystyrene as a compatibilizer between the polystyrene matrix and MWCNT as well.

Synthesis of macrocyclised dimetric compounds and their liquid crystal transition behaviours

Cyclic C-n dimers were synthesised by the ring-closing metathesis of linear L-n dimers with allyl tails under high dilution in the presence of the first Grubbs catalyst. The C-n dimers form a smectic phase similarly to the precursor L-n dimers, but the smectic structure and phase transition behaviour are remarkably different from those in L-n in the following respects. First, the C-n dimers invariably form a smectic A phase, although the L-n dimers as well as the conventional dimers form smectic A and smectic CA phases depending on whether the number of carbons on the spacer is even or odd. Second, the isotropisation temperature of the C-n dimer is significantly higher than that of the L-n dimer so that the smectic temperature span is expanded to 100°C from around 30°C for L-n. Third, the layer order in the smectic phase of the C-n dimer is remarkably higher than that of the L-n dimer, especially when n is small. These differences are explained as an effect of macrocyclisation, which forces the spacer to fold and thereby causes the two mesogens within a molecule to face each other closely.