Thermo-Responsive Cellulose Paper via ARGET ATRP

Thermo-responsive poly(N-isopropylacryl-amide) (PNIPAM), was grafted from cellulose paper via activators regenerated by electron transfer atom transfer radical polymerization (ARGET ATRP). Six solvents with different polarities, including water, methanol, isopropanol, anisole, and methanol/H2O, isopropanol/H2O mixed solvents, were utilized to perform the grafting polymerization. The results suggested that solvent system with moderate polarity was favored to ensure successful polymerization as well as avoid the destruction of the structure of virgin paper. Modified papers with various grafting ratios were achieved by changing the reaction solvent. Compared to lump-sum addition of excess reducing agent, intermittent addition of reducing agent during the reaction process made the polymerization rate more controllable. ATR-FTIR. and SEM characterization indicated the successful grafting of PNIPAM from the paper surface. Water contact angle measurements revealed that the polymer-grafted papers were thermo-responsive, presenting reversible switching in wettability with the change of temperature.