Versatile poly(N-vinylcaprolactam)-grafted-hydroxypropyl cellulose polymers with tailored thermo- and pH-responsive properties via sustainable organocatalyzed atom transfer radical polymerization

Abstract

This study explores the synthesis of dual pH- and thermo-responsive poly(N-vinylcaprolactam)-grafted-hydroxypropyl cellulose (PNVCL-g-HPC) polymers via visible-light-driven, metal-free organocatalyzed atom transfer radical polymerization (O-ATRP). Three distinct PNVCL-g-HPC polymers were prepared with controlled molecular weights and narrow dispersity indexes by grafting PNVCL chains onto a cellulose-based macroinitiator. The polymerization was facilitated by 1,2,3,5-tetrakis(carbazol-9-yl)-4,6-dicyanobenzene, a photoredox catalyst that effectively uses visible light to start the polymerization. The resulting polymers were characterized using FT-IR spectroscopy, NMR spectroscopy, GPC, and TGA. By analyzing the transmittance of the PNVCL-g-HPC polymers as a function of temperature over a range of pH values (3-12), the lower critical solution temperature (LCST) of the polymers was determined. We successfully tuned the LCST of these polymers to a physiological range (25-38 °C) by adjusting the HPC and PNVCL monomer ratios. Notably, the HNC-18 polymer exhibited an LCST of approximately 37.2 °C, making it suitable for biological applications. These polymers, with adjustable LCSTs, hold promise for diverse applications in electronics, biosensors, pharmaceuticals, biomedical fields, and drug delivery systems.