Poly(vinyl alcohol) Membranes Cross-linked with Maleic Anhydride and 2,5-Furandicarboxylic Acid: Conventional Heating and Microwave Irradiation

Poly(vinyl alcohol) (PVA) was cross-linked with maleic anhydride (MA) and 2,5-furandicarboxylic acid (FDCA) under conventional heating (CH) and microwave irradiation (MW) to obtain different membranes of PVA/MA and PVA/FDCA modified by the cross-linking agent concentration, reaction time and type of activation method. The influence of the latter parameters, was studied by comparing the swelling degree of the membranes, swelling kinetics, solubility parameter (delta), Flory interaction parameter (chi(12)), molecular weight between cross-links (M-c) and the fractional free volume (FFV). Conditions to cross-link the membranes were chosen from swelling percentage tests and the samples with the lowest water uptake were characterized by means of Fourier transform infrared spectroscopy (FTIR), C-13 nuclear magnetic resonance (C-13 NMR), thermogravimetric analysis (TGA) and atomic force microscopy (AFM). MW activation used from 23 to 30 minutes to cross-link the membranes, meanwhile, conventionally heated samples were introduced in an oven for 120 min, meaning that MW activation provided high reaction yields in shorter times. For both activation methods, FTIR spectra recorded peaks in an interval of 1706-1713 cm(-1), and C-13 NMR presented signals from 162 to 171 ppm, meaning that carbonyl groups from esters were formed. AFM images showed that the rise in roughness was not necessarily directly proportional to the increase in the concentration of cross-linking agent.