Effects of heating on the molecular orientation of polymeric lipids

Asymmetric membranes consisting of multilayers of polymeric lipids on a porous Teflon substrate were fabricated by the Langmuir-Blodgett technique. Fourier transform IR transmission spectroscopy was used to measure the level of molecular order in the n-alkyl side-chains of the polymeric lipids. The level of orientational order was monitored as a function of heat treatment temperature. We find that in the two polymer lipids studied, annealing below the bulk melting temperature leads to only a small decrease of order in the n-alkyl tails while removing a significant percentage of macroscopic defects. Heating to above the melting point results in an irreversible disordering of the alkyl chains.