Helical structure of sugar-carrying polystyrene in aqueous solution by circular dichroism.

Radical polymerization of N-p-vinylbenzyl-D-lactonamide (VLA) gave an optically active helical polymer. The stereoregularity of poly(N-p-vinylbenzyl-D-lactonamide) (PVLA) measured by 13C NMR spectroscopy showed a well-resolved sharp-line width, which was assigned to the phenyl C-1 carbon of the isotactic polystyrene (PS). The helical structure of PVLA shown by circular dichroism (CD) indicated that the aromatic groups were chirally supramolecular-packed giving optically active disaccharide units in the side chain covalently linked via an amide linkage with PS, the original PS not being optically active. The intensity of CD for PVLA (a) decreased with increasing temperature due to the change in the conformation of the phenyl group or to the breakdown of intermolecular hydrogen bonding of amide groups and (b) increased in a mixture of water and alcohol due to the increased hydrophobicity. The CD intensity for maltose-carrying PS (PVMA) was slightly higher than that of PVLA CD due to the more hydrophobic property of PVMA than PVLA.

Difference in the attachment of hepatocytes between a poly(gamma-benzyl L-glutamate) (PBLG)/poly(N-isopropylacrylamide) (PNIPAAm) diblock copolymer cast surface and a PBlg/PNIPAAm Langmuir-Blodgett one.

The effects of temperature on the monolayer behavior of the poly(gamma-benzyl L-glutamate) (PBLG)/poly(N-isopropylacrylamide) (PNIPAAm) diblock copolymer at the air-water interface were examined. Differences in the adhesion and morphology of hepatocytes between Langmuir-Blodgett (LB) films and cast surfaces of the PBLG/PNIPAAm diblock copolymer were investigated. The surface pressure (pi)-area (A) curve of the block copolymer had a tendency to expand with the temperature, due to a change in the conformation of PNIPAAm with the temperature change. Attachment of hepatocytes onto the PBLG/PNIPAAm block copolymer LB surface decreased slightly with an increase of the PNIPAAm content in the block copolymer, whereas that onto the cast surface decreased rapidly with an increase of the PNIPAAm content, due to the hydrophilic property of PNIPAAm in the microphase-separated structure. Rapid morphological changes of the hepatocytes adhered to the LB surfaces, from round shapes to spreading ones, were observed, compared with the cast films. The hepatocytes that adhered to the block copolymer LB surfaces showed less flattened and spread shapes than those that adhered to the PBLG one. Also, the spheroid formation of the hepatocytes increased with an increase of the PNIPAAm content in the block copolymer cast films.