A series of oligomers, containing oligo(ethylene glycol) (OEG) moieties, with the same composition of amphiphilic functionalities has been designed, synthesized, and characterized for their temperature sensitive behavior. The non-covalent amphiphilic aggregates, formed from these molecules, influence the temperature sensitivity of these molecules. Moreover, the covalent tethering of the amphiphilic units also has significant influence on their temperature sensitivity. The lower critical solution temperatures (LCST) of these oligomers show increasingly sharp transitions with increasing numbers of OEG functional groups, indicating enhanced cooperativity in dehydration of the OEG moieties when covalently tethered. These molecules were also engineered to be concurrently sensitive to enzymatic reaction and pH. This possibility was investigated using porcine liver esterase as the enzyme, where we show that enzymatic action on the pentamer lowers its temperature sensitivity. The product moiety from the enzymatic reaction renders the amphiphilic oligomer exhibit a pH-dependent temperature sensitivity.
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