Functionalized Biocompatible Poly( N ‐vinyl‐2‐caprolactam) With pH‐Dependent Lower Critical Solution Temperature Behaviors

Functionalized temperature‐ and pH‐sensitive poly( N ‐vinyl‐2‐caprolactam) (PVCL) polymers are prepared by copolymerizing monomers of N ‐vinyl‐2‐caprolactam (VCL) and a VCL derivative, 3‐( tert ‐butoxycarbonyl)‐ N ‐vinyl‐2‐caprolactam (TBVCL). Different molar compositions are studied, with the functional monomer at 9 and 14 mol%, respectively, (COOH‐PVCL9 and COOH‐PVCL14). Sharp, complete, and reversible phase transitions of the copolymers with little hysteresis are shown to be pH‐dependent, with cloud points ranging from 35 to 44 °C for COOH‐PVCL9, and 29 to 64 °C for COOH‐PVCL14, upon pH change from 2.0 to 7.4. Cytotoxicity assay demonstrates that the functionalized PVCL copolymers are biocompatible with NIH/3T3 up to 2 mg mL −1 . Such new PVCL‐based water soluble copolymers with tunable properties could be useful in a variety of biomedical applications.