Molecular Gels Sport New Phase Transition

Researchers have discovered a gel-to-gel phase transformation mechanism in which solvent molecules are expelled from or incorporated into molecular gel networks. V. Ajay Mallia, Bijay Sarkar, K. Travis Holman, and Richard G. Weiss of Georgetown University and Paul D. Butler of the National Institute of Standards & Technology found that when gels of some (R)-18-(n-alkylamino)octadecan-7-ols in CCl₄ solvent are heated they undergo opaque-to-transparent phase transitions that are thermally reversible (J. Am. Chem. Soc., DOI: 10.1021/ja204371b). Structural and spectroscopic data indicate that CCl₄ molecules are expelled from the fibrillar networks on heating and incorporated into them on cooling. The transitions are caused by changes in molecular packing of gelator molecules within the fibers. If other molecular gels can be engineered to make similar transitions, such gels could be useful for preparing metal nanoparticles, controlling drug release, and other applications, the researchers note.