A series of monoacryl and diacryl double-chain ammonium amphiphiles were synthesized and their bilayer characteristics before and after photopolymerization were examined. UV irradiation of unpolymerized bilayer dispersions in water gave polymerized bilayers without much change in the aggregation number, although the morphologies of the latter as observed by negative-staining electron microscopy were less ordered than those of the former. The molecular weight of the polymers in organic solvents amounted to several millions. Diacrylated bilayers gave large fractions of the insoluble product upon polymerization. The molecular organization in the polymerized bilayer was scrutinized by a combination of thermal and spectral measurements. Differential scanning calorimetry showed that sharp phase transitions observed in the unpolymerized bilayers became broader and were accompanied by hysteresis upon polymerization. The benzene unit in the spacer portion of a polymerizable amphiphile was a versatile internal probe for assessing the bilayer alignment. The much enhanced circular dichroism of the unpolymerized, crystalline bilayer was reduced and displayed large hysteresis upon polymerization. Strong fluorescence emission from the benzene unit was observed in the crystalline bilayers. Fluorescence recovery after rapid cooling and absorption spectral equilibration of a membrane-bound cyanine dye were also slow in the polymer. A certain degree of disordering in the molecular alignment remained for bilayers polymerized in the liquid-crystalline state.
All Science Journal Classification (ASJC) codes
- Organic Chemistry
- Polymers and Plastics
- Inorganic Chemistry
- Materials Chemistry