Enclosure of Secondary Chirality Based on Highly-Oriented Lipid Aggregates into a Polymer Sheet by Photo-Induced Polymerization of Polymerizable Monomer Gels

摘要

The L-glutamide derivative with double long-chain alkyl groups and a pyrenyl head group (Pyr-lipid) worked as organogelator in benzene and cyclohexane. Gelation was brought about through network formation with well-developed fibrous aggregates based on lipid membrane-like highly-oriented structures. Gelation was observed in polymerizable monomers such as methyl methacrylate (MMA) and styrene (St). Extremely intense CD spectra were observed at the absorption band of pyrenyl group in a monomer solution at gel-forming temperature, but the intensity decreased remarkably at the sol-forming temperature. The transparent solid sheet was obtained by photo-irradiation to the MMA gel in a quartz cell. More than 99% of MMA was polymerized even in the gel state and the weight-average molecular weight (M_w) of the resultant polymer was 7.2 × 104 g mol−1. CD spectra indicated that chirally-oriented structures in the gel state were maintained after polymerization of MMA and were stable at the temperature above the original gel-to-sol transition temperature. Fluorescence spectra of Pyr-lipid in the monomer solutions supported that the pyrene excimer was formed in the lipid aggregates and the stabilization of the excimer formation was achieved by polymerization of MMA in the gel state.