Molecular modeling of thermo-responsive hydrogels: observation of lower critical solution temperature

Stimuli-sensitive hydrogels offer enormous potential as 'intelligent' drug delivery vehicles, i.e. ones which are targeted and responsive to symptomatic needs. In particular, temperature sensitive hydrogels exhibit a dramatic, but well defined, volume phase transition (lower critical solution temperature (LCST)), which depending upon the hydrogel, results in either an expansion or shrinkage of the hydrogel. The exact mechanism of the LCST is not fully understood, weakening the ability to design devices a priori. Here, molecular simulation techniques are used to model the hydrogel poly (N-isopropyl acrylamide) (PNIPAM) above, below and at the LCST to probe the molecular level mechanisms governing its origin and transport mechanisms within the hydrogel under NPT ensembles.