Functionalization of poly(vinyl alcohol) by addition of methacryloyl groups: characterization by FTIR and NMR and optimization of reaction conditions by RSM

Abstract

Abstract:The modification of poly(vinyl alcohol) (PVA) with glycidyl methacrylate (GMA) in DMSO catalyzed by TEMED is reported in this paper. PVA was dissolved in DMSO and reacted with GMA at 30 ºC in a closed vessel under N 2 gas bubbling for 24 hours. The reaction was characterized by FTIR and NMR ( 1 H, 13C/DEPT and HETCOR) spectroscopies. The reaction occurs by transesterification through the insertion of methacryloyl groups into PVA chains and probably with the formation of glycidol as a by-product. The degree of substitution (DS) that represents the number of methacryloyl groups inserted was determined through 1 H NMR spectra based on the ratio between the averaged area due to the vinyl hydrogen from methacryloyl groups at δ  5.6 ppm and δ 6.0 ppm and the total area of the vinyl hydrogen and hydroxyl hydrogen of PVA. By use of response surface methodology the experimental conditions were optimized. The optimum conditions were 62 ºC with a reaction time of 6 hours. In these optimized conditions, the reactions using the molar ratios [-OH(PVA)/GMA] equal to 1/0.10, 1/0.25, 1/0.50, 1/0.75 and 1/1 were investigated. The response surface was based on the model , where T is the temperature (°C) and t the reaction time (hours). This model explained 99.20 % of the 99.64 % explainable statistical data. Using the optimized conditions, it is possible to produce a desired modified PVA, (or PVA-Ma), because DS raises linearly to the ratio [-OH(PVA)/GMA] up to 25 mol-% and the respective yield ranged from 83 to 92 %. It is difficult to obtain more than 50 mol-% substitution of PVA hydroxyl by methacryloyl groups even in these optimized conditions due to increased steric hindrance by the large number of the methacryloyl groups inserted into PVA.

Hydrogels based on chemically modified poly(vinyl alcohol) (PVA-GMA) and PVA-GMA/chondroitin sulfate: Preparation and characterization

“…The FTIR spectrum of PVA-GMA100 hydrogel (Figure 1a) presents a broad band at 3421 cm -1 assigned to the -OH stretching, a band at 2936 cm -1 assigned to C-H vibrational stretching, and a band at 1094 cm -1 assigned to C-O vibrational stretching. Moreover, the bands at 1727 and 1642 cm -1 , which are assigned to C=O and C=C stretching, proceeding from methacrylate groups of GMA used for modifying PVA [36]. The FTIR spectrum of CS (Figure 1d) shows a broad band between 3100-3600 cm -1 assigned to -OH and to N-H vibrational stretching in which the -OH stretching overlaps the N-H one.…”

Preparation of hydrophilic woven fabrics: Surface modification of poly(ethylene terephthalate) by grafting of poly(vinyl alcohol) and poly(vinyl alcohol)‐g‐(N‐vinyl‐2‐pyrrolidone)

“…In only a few studies, synthesis of block copolymers of vinyl acetate and NVP has been reported with the cobalt‐mediated living polymerization and reversible addition‐fragmentation chain transfer polymerization techniques . For this purpose, to provide grafting of NVP to the PVA chains by means of free‐radical polymerization, first, a PVA–GMA prepolymer was prepared by the chemical modification of PVA with GMA monomer according to a method published in the literature . It has been reported that a transesterification reaction between a GMA monomer and PVA takes place in the media of polar‐aprotic solvents such as DMSO and DMF, and the vinyl methacrylate side of the GMA is attached to PVA chains from hydroxyl groups of PVA .…”

“…For this purpose, to provide grafting of NVP to the PVA chains by means of free‐radical polymerization, first, a PVA–GMA prepolymer was prepared by the chemical modification of PVA with GMA monomer according to a method published in the literature . It has been reported that a transesterification reaction between a GMA monomer and PVA takes place in the media of polar‐aprotic solvents such as DMSO and DMF, and the vinyl methacrylate side of the GMA is attached to PVA chains from hydroxyl groups of PVA . The glycidol side of GMA has occurred as a byproduct during the reaction.…”

“…To synthesize the PVA‐ g ‐NVP copolymers, first, a PVA–GMA prepolymer was prepared by introducing vinyl methacrylate groups to PVA chains according to a previous method in the literature . Briefly, 5.0 g PVA was taken into a two‐necked round bottom flask and dissolved in 50 mL of DMSO medium at 70 °C with stirring.…”

“…The impurities of unreacted GMA, TEMED, and PVA and possible byproducts were removed by the multiple steps of dissolving the prepolymer in 1/1 acetone/ethyl alcohol mixture (V/V) at 60 °C with stirring and reprecipitation with distilled water. The PVA–GMA prepolymer was dried in a vacuum oven at 30 °C and stored in a refrigerator at −5 °C to prevent the formation of possible unwanted byproducts with the effect of heat or light, according to the literature …”