Temperature-Responsive Surface-Functionalized Polyethylene Films

Abstract

Polyethylene−poly(ethylene glycol) co-oligomers were used to surface functionalize polyethylene films via an entrapment process. When immersed in water, the poly(ethylene glycol) groups at these surfaces had solvation behavior that resembled the known inverse temperature-dependent solubility properties of poly(ethylene glycol) in water. The responsiveness of these films' surfaces was characterized by fluorescence spectroscopy and kinetic studies using pyrene ester labels. Changes in the ratio of the I1/I3 peaks in the emission spectrum of the pyrene probe showed that the interface micropolarity was higher at low temperature and lower at high temperature. Repeated heating and cooling (5 °C → 65 °C → 5 °C → 65 °C) with the same sample showed that these interface changes were substantially reversible. Interface solvation was measured by comparing I1/I3 ratios for pyrene-labeled oligomers in water, ethanol, and toluene solutions with similar labels on films suspended in these same solvents. The results show t...