علوم و تکنولوژی پلیمر (Oct 2018)
Functionalization of Poly(vinyl alcohol) and Ethylene-Vinyl Alcohol Copolymer with Various Reactive Functional Groups: Synthesis and Characterization
Abstract
Hypothesis: Discovering new chemical modifications for polymers is an interesting way to change the properties and final applications of the polymers. Poly(vinyl alcohol) (PVA) and ethylene-vinyl alcohol copolymer (EVA) are useful in practical investigations of functional polymers because they can be modified through their hydroxyl groups. In this study, PVA and EVA were modified to incorporate different reactive functional groups using esterification reaction. Then, substitution reaction was used to incorporate benzimidazole groups into the modified EVA. Azolated EVA can be utilized in other applications such as fuel cell as a proton exchange membrane.Methods: Functional modification of PVA was carried out by acryloyl chloride and maleic anhydride in 1-methyl-2-pyrolydone (NMP, room temperature) and dimethyl sulfoxide (DMSO, 100°C), respectively. Similarly, EVA was modified with chloroacetyl chloride and α-bromoisobutyryl bromide via esterification reaction in NMP at room temperature. Next, benzimidazole group was incorporated into the α-bromoisobutyrylated EVA through substitution nucleation reaction with sodium-2-mercaptobenzimidazole in THF at 80°C.Findings: Chemical structures of polymers were investigated by FTIR and 1H NMR. Functionalization of PVA with acryloyl chloride and maleic anhydride was calculated to be 9.31 and 46.28 mol% and that of EVA with chloroacetyl chloride and α-bromoisobutyryl bromide was obtained to be 71.50 and 63.46 mol%. The high yield obtained in all of the different proposed routes makes them feasible for activation of EVA copolymers. Moreover, to predict the solubility behavior of functionalized polymers, the Hansen solubility parameters of original and modified polymers were calculated via Hoftyzer-Van Krevelen's (HVK) and Hoy's group contribution methods. Calculations showed that, among studied solvents, dimethylacetamide is the best solvent for acryloylated PVA, carboxyvinylated PVA and EVA copolymer, while acetone is the best one for copolymers modified with chloroacetyl chloride and α-bromoisobutyryl bromide and azolated copolymer, which was in good agreement with the experimental results.
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