Synthesis and characterization of thermosensitive copolymers for oral controlled drug delivery

Poly(N-isopropylacrylamide) (PNIPAAm) copolymers were synthesized in order to obtain co-polymers with a phase transition temperature slightly higher than the physiological temperature, as required by a new drug delivery concept described in a previous paper. Six hydrophilic comonomers bringing about a rise of the phase transition temperature were evaluated. The synthesized copolymers were characterized and the influence of the type and of the amount of the used comonomer on the phase transition temperature was discussed. Among the comonomers, Acrylamide (AAm), N-methyl-N-vinylacetamide (MVA), N-vinylacetamide (NVA), and N-vinyl-2-pyrrolidinone (VPL) were found to be capable to raise the phase transition temperature to a value slightly higher than 37 °C and to have adequate phase transition behavior. The selected four copolymers were subjected to an additional purification step that should make them fit to use as a controlling agent in drug delivery systems.