Hydrogel‐forming agar‐graft‐PVP and κ‐carrageenan‐graft‐PVP blends: Rapid synthesis and characterization

Abstract

Grafting of agar and k-carrageenan with polyvinylpyrrolidone (PVP, average molecular weight 10,000 D) in an aqueous medium at a pH of about 7 produced agargraft-PVP and k-carrageenan-graft-PVP blends capable of forming hydrogels. The reaction was carried out with microwave irradiation in the presence of a water-soluble initiator, potassium persulfate. Optimum microwave irradiation conditions for obtaining hydrogels of the grafted products were achieved. The structural characteristics and thermal stability of the grafted blends were studied by Fourier transform infrared, 13 C-NMR, and thermogravimetric analyses. Appearance of new IR bands at 1661, 1465, and 1426 cm À1 in the grafted products indicated the insertion of PVP into the polysaccharide structure. Powder X-ray diffraction studies revealed the enhanced crystallinity in the products compared to in the control polysaccharides as well as PVP. Agar and k-carrageenan were grafted to a considerable degree, with 62.5 E % and 125 G % for agar-graft-PVP and 65.5 E % and 131 G % for k-carrageenan-graft-PVP. Optical micrographs of the grafted blends indicated considerable changes in the morphology of the agar and the k-carrageenan, substantiating the X-ray diffraction data. A plausible mechanism for the crosslinking of PVP to agar and k-carrageenan is proposed. These hydrogels exhibited enhanced water-holding capacity despite weaker gel strength than that in the respective control polysaccharides.

Investigation of polymer electrolyte based on agar and ionic liquids

“…The stretching of the COH alcohol bond shifts from 1087 to 1038 cm -1 , which is probably due to the hydrogen bond formation between glycerol and macromolecule. Other bands from 920 to 960 cm -1 , depending on the sample, can be assigned to C-O-SO 3 or C-C stretching from polymer ring [26] and at 780; 790 cm -1 to IL ring HCCH symmetric bending [22] or 3,6-anhydro-!-galactose skeletal bending [26].…”

Agarose processing in protic and mixed protic–aprotic ionic liquids: dissolution, regeneration and high conductivity, high strength ionogels

“…Characteristic IR bands at 773, 894, and 932 cm −1 because of 3,6-anhydro-b-galactose skeletal bending in agarose 70 remain unaltered in the regenerated material except those regenerated from the solvent systems containing pyridinium based ILs wherein these bands appear slightly diminished. The IR bands at 1158 and 1071 cm −1 corresponding to -C-O-C-and glycosidic linkage 70,71 are also altered in the regenerated material. No peak corresponding to IL moieties indicates that ILs or mixed ILs are fairly non-coordinating media for the processing of agarose.…”

A review of extractions of seaweed hydrocolloids: Properties and applications

“…The synthesis of agar-graftpolyvinylpyrrolidone (PVP) and κ-carrageenan-graft-PVP blends by a microwave irradiation method has been reported by Prasad et al [55]. The physicochemical properties of corresponding hydrogels were studied and compared with control agar and kappacarrageenan hydrogels.…”