Micromorphology Memory in Amphiphilic Polypeptides

Micromorphology memory was observed using thin films of PEGylated polypeptides, poly{(β-benzyl-L-aspartate) (BLA)-block-ethylene glycol (EG)-block-BLA}. The slow vaporization of polymer dichloromethane solutions led to the formation of multi-spherulite films, which disappeared upon heating above the PEG melting temperature, 57 °C, but reappeared by successive cooling, down to 30 °C, thereby changing the spherulite interface morphology. The water-immersion of recrystallized films caused the self-assembly of peptide chains to form water-swollen networks with spherulites, but surprisingly, spherulite interface morphologies remained completely the same as once-disappeared morphologies in the original dry films. A similar memory behavior was also observed in the pattern inside a milliscaled spherulite which entirely occupied the network. Spectroscopic and microscopic studies suggest that appropriate peptide conformations are very important for memorized micromorphology.