Studies on pH-sensitivity of double hydrophilic block copolymers of poly(n-vinylcaprolactam)-b-poly(hydroxymethyl acrylamide)

pH-sensitive block copolymers of poly(N-vinylcaprolactam)-block-poly(N-hydroxymethyl acrylamide) (PNVCL-b-PNMA) were synthesized via macroinitiator approach of atom transfer radical polymerization (ATRP). In this work, the amount of NMA in the monomer feed was varied to study their changes in particle size in different pH which correlated with their pH-sensitive behavior. The respective macroinitiator of PNVCL-Br and PNVCL-b-PNMA block copolymers were characterized by FT-IR to analyze the functional groups on the polymers, and 1H-NMR for structural analysis, the number of polymers repeat units, and molecular weight (Mn). Meanwhile, particle size analysis at various pH was carried out using a Particle Size Analyzer (PSA) to investigate the sensitivity of the block copolymers to pH. The FT-IR spectra showed the presence of typical functional groups from PNVCL and PNMA in PNVCL-b-PNMA, without the presence of a vinyl group that proves that polymerization had occurred. Based on the 1H-NMR spectrum, the PNVCL-Br macroinitiator was obtained with 45 repeating units of monomer. PSA analysis was carried out at pH of 3, 5, 7, 9, 12, in which, in general, there was a decrease in particle sizes with increasing pH. In our opinion, such pH-sensitivity block copolymers are potential candidates for a pH-controllable cargo delivery system.