J. Am. Chem. Soc. doi:10.1021/ja104691j (2010)

Poorly soluble drugs and other chemicals can be dissolved in liquid by packaging them inside micelles — soluble molecular assemblies that often assume hollow spherical or floral shapes. Heat can rattle these structures apart, but attaching additional molecules to boost the micelles' heat resistance can change their size, shape or chemical properties.

Now Satoshi Honda, Takuya Yamamoto and Yasuyuki Tezuka at the Tokyo Institute of Technology show that a topological tweak improves the thermal stability of a micelle without affecting its other properties. Circular polymers formed micelles (pictured, left) that resisted fragmentation at temperatures some 40 °C higher than did physically and chemically identical micelles made from straight-chain polymers. The latter (right) have loose ends, which are more easily dislodged with heat. The authors showed that they could tune the thermal stability of micelles by creating them from varying ratios of the two polymers.

Credit: AM. CHEM. SOC.