Synthesis, characterization, and gas permeation properties of t-butylcarbamates of cellulose derivatives

t-Butylcarbamates of ethyl cellulose (1: DSEt, 2.69; 2: DSEt, 2.50) and cellulose acetate (3: DSAc, 2.46; 4: DSAc, 1.80) were synthesized by the reaction of residual hydroxy groups of cellulose derivatives with t-butylisocyanate. The 1H NMR spectra and elemental analysis were employed to determine the degree of incorporation of carbamoyl moiety (DSCarb) and almost complete substitution of the residual hydroxy protons was observed. The presence of the peaks characteristic of the carbamate linkage in the FTIR spectra furnished further evidence for the successful carbamoylation of ethyl cellulose and cellulose acetate. The resulting polymers (1a–4a) were soluble in common organic solvents. The onset temperatures of weight loss of 1a–4a were 177–204 °C, indicating fair thermal stability. The free-standing membranes of 1–4 and 1a–4a were fabricated, and derivatized polymers exhibited enhanced gas permeability, especially the gas permeability of cellulose acetate (3: DSAc, 2.46; 4: DSAc, 1.80) underwent a significant increment. 4a exhibited a remarkable increase in CO2 permeability, i.e., 22 times higher than that of 4 (image 38 barrers; cf. image of 4, 1.7 barrers). Quite interestingly, a more or less retainment of CO2/N2 permselectivity was revealed.