Polyacrylic acid supported TEMPO for selective catalytic oxidation of cellulose: recovered by its pH sensitivity

Abstract Water-soluble polyacrylic acid was prepared by solution polymerization, and then partially acylated by SOCl 2 to give a random copolymer of poly(acrylic acid- co -acryloyl chloride) (P(AA- co -AC)). Through the reaction of acyl chloride groups in P(AA- co -AC) with hydroxyl groups in 4-hydroxy-2,2,6,6-tetramethyl-piperidinooxy (4-OH-TEMPO), the water-soluble TEMPO immobilized copolymer of poly(acrylic acid- co -2,2,6,6-tetramethylpiperidinyloxy-4-yl-acrylate) (P(AA- co -TA)) with different TEMPO loadings were prepared and characterized by Fourier transform infrared spectroscopy and conductometric titration. P(AA- co -TA) was used as a recoverable catalyst instead of free TEMPO for selective catalytic oxidation of cellulose in water. The carboxyl content of oxidized cellulose with P(AA- co -TA) as catalyst was up to 60% of the free TEMPO level. Furthermore, P(AA- co -TA) was easy to recycle by its pH-sensitivity and the activity did not decrease after 4 cycles. Graphical abstract