Cyclic ureas as solvents for esterification of poly(vinyl alcohol) and vinyl acetate‐vinyl alcohol copolymers with acid chlorides

Abstract

Poly(vinyl alcohol) (PVAL) and vinyl acetate-vinyl alcohol copolymers (VAVAL) were esterified with 3,5-dinitrobenzoyl chloride using the cycled urea N,N 0 -dimethylpropyleneurea (1,3-dimethyl-3,4,5,6-tetrahydro-2(1H)-pyrimidinone) (DMPU) as the solvent. Vinyl alcohol-vinyl-3,5-dinitrobenzoate copolymers (VALVDNB) and vinyl acetate-vinyl-3,5-dinitrobenzoate copolymers (VAVDNB) were obtained. High degrees of esterification were obtained when PVAL was esterified (86%). The degree of transformation was determined by 1 H-NMR as well as by chemical analysis, and the structure of the resulting polymers by means of IR spectroscopy and 1 Hand 13 C-NMR. The microstructure of PVA, PVAL, VAVAL copolymers and VALVDNB copolymers were determined from 1 H-and 13 C-NMR techniques. The sequence distributions for VAVAL copolymers prepared by base-catalyzed transesterification of PVA were blocky, while the distributions were close to random for VALVDNB copolymers obtained by esterification of PVAL. Thermal properties were studied by DSC. The T g values of VAVAL, VALVDNB, and VAVDNB copolymers as a function of copolymer compositions were determined.

Polymeric Modification of Graphene through Esterification of Graphite Oxide and Poly(vinyl alcohol)

“…This signal can be related to hydroxyl protons next to acetate groups as have been reported for esterification of PVA. 13,14 By integration of this 1 H NMR signal we can evaluate, within the experimental uncertainties, the degree of functionalization, obtaining a modification of around 1.8%. Interestingly, this value is reasonably low due to the huge volume of graphitic laminates (GLs) and is in agreement with the decrease of mm triad content, as consequence of being less sterically hindered internally than those at syndiotactic counterpart, specifically in the incorporation of the GLs.…”

Quantitative Poly(vinyl alcohol) Modification in Ionic Liquids: Esterification and Urethanation with Low Surface Tension Producing Reagents

“…[1][2][3][4][5][6][7] Current modification methodologies for these polymers, however, remain complex and time-consuming despite the long-tenure interest in this area of research. For PVOH specifically, esterification [8][9][10][11][12] and urethanation 13 have been demonstrated; however, slow reaction kinetics and nonquantitative reaction yields are reported. These reaction limitations are due to the limited number of solvents that dissolve PVOH and do not interfere with alcohol chemistry.…”

“…N-Methylpyrolidone may be sufficient for certain modifications, 12 but in other cases, designer solvents such as cyclic ureas are required to be synthesized to study potential solvent alternatives. 9 In all cases, however, the modification of PVOH is a time-intensive and nonquantitative process.…”

“…The modification of polymers that contain alcohol functionality, such as cellulose and poly(vinyl alcohol) (PVOH), has been of great interest for many years and has resulted in products ranging from guncotton to tissue scaffolds. − Current modification methodologies for these polymers, however, remain complex and time-consuming despite the long-tenure interest in this area of research. For PVOH specifically, esterification − and urethanation have been demonstrated; however, slow reaction kinetics and nonquantitative reaction yields are reported. These reaction limitations are due to the limited number of solvents that dissolve PVOH and do not interfere with alcohol chemistry.…”

“…Significant efforts have been made to find alternative solvents for PVOH that can facilitate rapid, quantitative modification of this polymer under simple reaction conditions. N -Methylpyrolidone may be sufficient for certain modifications, but in other cases, designer solvents such as cyclic ureas are required to be synthesized to study potential solvent alternatives . In all cases, however, the modification of PVOH is a time-intensive and nonquantitative process.…”