Reverse thermal organogels

Abstract

The poly(ethylene glycol), poly(L-alanine-co-L-phenyl alanine) diblock copolymer (PEG-PAF), forming a free-flowing solution in chloroform at low temperature forms a gel as the temperature increases above 20°C. The transmission electron microscopy (TEM) image of the PEG-PAF developed in chloroform showed that spherical micelles with a size of 20-50 nm is packed together. The delicate balance between solvency and nonsolvency of a block copolymer might drive reverse thermal gelation in the solvent. This system expands the applications of organogels to sensors, media for electrochemistry carriers, and rheological modifiers, where the characteristics of low viscosity at low temperature and gel at high temperature are required.