Synthesis, characterization, and swelling behavior of poly(N‐hydroxymethylacrylamide) grafted poly(vinyl alcohol)

Abstract

In this study, the graft copolymerization of N‐hydroxymethylacrylamide (NHMAAm) with poly(vinyl alcohol) (PVA) was carried out by using potassium persulfate/N,N,N,N‐tetramethylethylenediamine (K2S2O8) to improve physicochemical properties and functionality of PVA. The structures of PVA‐g‐poly‐NHMAAm (PNHMAAm) copolymers were characterized by Fourier transform infrared, elemental analysis, nuclear magnetic resonance (1H‐NMR), 13C‐NMR, and size exclusion chromatography. Their thermal behaviors were investigated by differential scanning calorimetry and thermogravimetric analysis (TGA). The TGA results indicated that the graft copolymers show better thermal stability then PVA. The effects of reaction time, temperature, NHMAAm, and K2S2O8 concentrations on grafting parameters were examined. The maximum grafting yield (34.01%) was provided when reaction was carried out under optimum conditions (time = 2 hr, T = 40°C, [NHMAAm] = 0.25 M, [K2S2O8] = 4.56 × 10−3 M). Moreover, PVA‐g‐PNHMAAm membranes were prepared and their swelling behaviors were studied. The results demonstrated that swelling degree of graft membranes increased almost 3.5‐fold compared to PVA membrane.

Pervaporation performance of poly(vinyl alcohol)‐graft‐poly(N‐hydroxymethyl acrylamide) membranes for dehydration of isopropyl alcohol‐water mixture

“…Furthermore, the absorption peak that appeared at 1088 cm −1 in both spectrums is the asymmetric stretching vibration of COC groups, which is well consistent with available literature reports 18,29 . The new two peaks at 1659 and 1544 cm −1 observed in the spectrum of the PVA‐g‐PNHMA 5 membrane were raised from the C═O stretching (amide I) and NH bending (amide II) vibrations, which confirm that NHMA groups are grafted onto PVA 20,30 . All of the other characteristic peaks of the PVA membrane appeared to the almost same wavenumbers for the grafted PVA membrane as illustrated in Table S1.…”

“…The spectrum of the PVA membrane showed the single signal at δ = 42 ppm and the triple signals at δ = 62, 68, and 74 ppm, which were corresponded to the  C H 2  and  C H carbons, respectively 18 . In addition to these signals, the PVA‐g‐PNHMA membrane's spectrum displayed a signal at 176 ppm belonging to the carbonyl group (> C ═O) of PNHMA branches, confirming chemical modification of PVA membrane with PNHMA chains 18,20 . Also, the signal at about 20 ppm and a shoulder at 32 ppm is attributed to the  C H 2 and  C H carbons in the PNHMA branches, respectively 20 …”

“…The synthesis of PVA‐g‐PNHMA copolymers was carried out as described in our previous study 20 . Briefly, 2% (m/v) of PVA solution was transferred into the three‐necked reaction vessel under the reflux.…”

“…The graft copolymer separated from its homopolymer was dried in the oven at 40°C up to it reached a constant weight. Equation () was used to calculate the grafting percentages of the copolymers 20 where N %, which was obtained from elemental analysis, and M indicates the nitrogen percentage (%) of the copolymer and molecular weight of NHMA, respectively.…”

“…Swelling studies of the PVA‐g‐PNHMA membranes were achieved via gravimetric measurements 20 . PVA‐g‐PNHMA membranes were dried completely and weighed to find out their dry mass ( m d ).…”