Study of the physico-chemical properties of novel water-soluble copolymers of cationic type based on N-isopropylacrylamide

Novel water-soluble copolymers of cationic type have been synthesized by free-radical copolymerization of N-isopropylacrylamide (NIPAAm) and N-(2-vinyloxyethyl)-N-(2-cyanoethyl)amine (VOECEA) in ethanol solutions, employing 2,2’-azobisisobutyronitrile (AIBN) as radical initiator. The polymerization at 60°C was carried out in ampules in an argon atmosphere for 2 h. After the reaction, the resultant copolymers were precipitated twice in boiling water and was then vacuum-dried for 24 h. The obtained NIPAAm-VOECEA copolymers were characterized by means of Fourier transform infrared spectroscopy (FTIR), thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC). It was observed that for copolymers with low moieties of NIPAAm in composition the degradation starts at low temperatures due to thermal decomposition of nitrogen groups of the copolymer. The presence of an oxygen in VOECEA backbone contributes the decomposition of linear copolymers at low temperatures. It was measured the glass transition temperature (Tg) of the synthesized copolymers. It was observed that with increasing the units of NIPAAm in copolymer composition the Tg increases due to the folding of linear polymer chain and the rigidity of NIPAAm moieties.