Tunable pH- and CO2-Responsive Sulfonamide-Containing Polymers by RAFT Polymerization

摘要

The controlled RAFT polymerization of a library of pH- and CO2-responsive methacryloyl sulfonamides (MSAs) that possess pK(a) values in the biologically relevant regime (pH = 4.5-7.4) is reported. Initial polymerizations were conducted at 70 degrees C in DMF with 4-cyano-4-(ethylsulfanylthiocarbonylsulfanyl)pentanoic acid (CEP) or 4-cyanopentanoic acid dithiobenzoate (CTP), resulting in polymers of broad molecular weight distributions (K-w/M-n > 1.20). As well, chain extension of a poly(methacryloyl sulfacetamide) (pSAC) macro-CTA at 70 degrees C was unsuccessful, indicating a loss of "living" chain ends during polymerization. However, by conducting the RAFT polymerization of MSAs at 30 degrees C with 2,2'-azobis(4-methoxy-2,4-dimethylvaleronitrile), polymers with narrow molecular weight distributions (M-w/M-n < 1.15) and improved chain end retention were obtained. Homopolymers of each MSA derivative were synthesized, and the influence of the sulfonamide R group on monomer pK(a) and pH-dependent polymer solubility was determined during these studies. The facility by which these controlled poly(MSAs) can be prepared via low-temperature RAFT without the need for functional group protection and the resulting pK(a)-dependent pH- and CO2-responsive properties point to significant potential in areas including drug and gene delivery and environmental remediation.