Molecular recognition of barbiturate artificial receptor covalently bound to an amphiphilic copolymer

Binding of a purely hydrogen bonding based artificial receptor in aqueous solutions has been achieved by employing a polymeric surfactant as a hydrophobic scaffold. The polymer consists of 70% (mole) 3-sulfopropyl methacrylate, 27% n-dodecyl acrylate and 3% barbiturate receptor (Scheme). UV-spectra of aqueous solutions containing phenobarbital and the receptor-bound polymer show prominent features that are indications of formation of complexes. These features were absent when a receptor-free blank polymer was characterized. Based on capillary electrophoresis, at pH 4, the mobilities of phenobarbital were near zero, both in pure buffer and in a buffer containing the blank polymer. This was anticipated as phenobarbital is nearly neutral and its polarity leads to weak partitioning. In contrast, when receptor-bound polymer was added to the buffer, the mobility of phenobarbital increased nearly two orders of magnitude. Equilibrium dialysis studies indicate the association constant to be at the order of 103-104 M-1.