Synthesis backbone-dual-responsive of hyperbranched poly(bis(N,N-ethyl acrylamide))s by RAFT

Hyperbranched poly(bis(N,N-ethyl acrylamide))s (HPNAMs) with many vinyls as terminal groups were synthesized successfully using reversible addition fragmentation chain transfer polymerization (RAFT). Detailed analyses, based on the molecular weight, α value, degree of branching (DB), and lower critical solution temperature (LCST) obtained from nuclear magnetic resonance (NMR), multi detector-size exclusion chromatography (MDSEC), ultravioletvisible (UV-vis) spectroscopy, and dynamic light scattering (DLS), indicate that we acquired backbone-temperature and pH responsive HPNAM. Factors, such as DB, molecular weight, and pH value, that affect the LCST were investigated. It was found that the molecular weights of the hyperbranched polymers show significant influence on the LCSTs. For the HPNAMs with low molecular weight, the LCSTs decreased as the DB increased, and the LCSTs can also be adjusted by changing the pH value of solutions. Furthermore, the result of cell cytotoxicity indicates that this new dual responsive hyperbranched polymer has low cytotoxicity and exhibits potential for biomedical applications.