Reaction of Glycidyl Methacrylate at the Hydroxyl and Carboxylic Groups of Poly(vinyl alcohol) and Poly(acrylic acid): Is This Reaction Mechanism Still Unclear?

Abstract

Transesterification and epoxide ring-opening reactions are two mechanism routes that explain chemical modifications of macromolecules by glycidyl methacrylate (GMA). Although the coupling reaction of the GMA with macromolecules has widely been investigated, there are still mechanisms that remain to be explained when GMA is processed in an aqueous solution at different pH conditions. To this end, reaction mechanisms of poly(vinyl alcohol) (PVA) and poly(acrylic acid) (PAAc) by GMA in water in acidic and basic conditions were investigated thoroughly. The presence of hydroxyl groups in PVA and carboxyl groups in PAAc allowed for a better evaluation of the reaction mechanisms. The analysis of the (1)H and (13)C NMR spectra clearly demonstrated that the chemical reactions of GMA with carboxyl groups and alcohols of the macromolecules in an aqueous solution are dependent on pH conditions. At pH 3.5, the GMA reacts with both the carboxylic and the hydroxyl groups through an epoxide ring-opening mechanism. At pH 10.5, the GMA undergoes a hydrolysis process and reacts with hydroxyl groups by way of both the transesterification and the epoxide ring-opening mechanisms, whereas the ring-opening reaction is the preferential pathway.

A cost effective hydrogel test kit for pre and post blast trinitrotoluene

“…A band with maximum absorption at 3266 cm -1 was attributed to the O-H stretching vibration peak from the PVA [17,36,37], while the maximum absorption peak at 1096 cm -1 can be attributed to C-O-C stretching vibration from the cross-link reaction of the PVA and the EGDE [23,38]. The stretching vibration of the alkyl groups (R-CH2) from the EGDE [38] and/or the PVA [26] was observed at a wave peak between 3000 and 2850 cm -1 with the maximum peak at 2910 cm -1 .…”

“…Chemical cross-linking can be conducted by irradiation or the use of bifunctional cross-linkers such as glutaraldehyde, while physical cross-linking can be achieved by the use of freezing/thawing cycles to form crystals. The hydrogel made by physical cross-linking processes produce a gel with a larger mesh or pore size [25] but with poorer mechanical properties and less thermal stability than gels formed by chemical cross-linking [26]. The properties of the synthesized material can be improved by the combination of cryogenic treatment with a chemical cross-linking process which can induce both physical and chemical cross-linking [27].…”

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

“…Although PVA can be easily cross-linked by contact with glutaraldehyde in acidic medium [14] such process presents limitations due to non-uniformity of the obtained matrix and to the severe toxicity of glutaraldehyde. PVA can also be physically crosslinked by repeated freezing-thawing cycles in aqueous solution, creating crystalline clusters that actuate as reticules [15,16]. The advantage of this process is the absence of moieties that could obliterate the biocompatibility.…”

“…The advantage of this process is the absence of moieties that could obliterate the biocompatibility. However, the PVA hydrogels obtained through freezing-thawing process are mechanically poorer and less thermally stable than those obtained by chemical cross-linking [15]. In addition, it is difficult to obtain physical gels in situ using this methodology.…”

Electrospinning fabrication, structural and mechanical characterization of rod-like virus-based composite nanofibers

“…6,7 Efforts have also been made to mimic the unique structures and specific functions of natural ECM by co-electrospinning PVA with proteins providing new materials and scaffolds. 8,9 Co-electrospinning of polymers and nanoparticles has been applied to improve cell-scaffold interactions to guide cell fate.…”