A Comparative Study of the Phase Transition Behavior of Cross-Linked Thin Polymeric Films

The potential of polymeric materials that exhibit a variation in their structure and properties in response to an external cue makes them exciting candidates for “smart” surfaces. Polymers that respond to a change in temperature are known as thermoresponsive polymers. Thermally responsive polymers exhibit a reversal phase transition at a critical temperature known as lower critical solution temperature (LCST). We have synthesized a series of photo-cross-linkable co-polymers based on isomers of N-isopropylacrymide and 4-methacryloxybenzophenone (MaBP). In the presence of UV light, the MaBP segments cross-link with the neighboring aliphatic moieties and form a surface-tethered network. Using the quartz crystal microbalance (QCM), we have monitored the collapse and swelling of the films in real time to illustrate the role that permutations in structure play on LCST behavior.