Modified guar gum-based hydrogels: Synthesis, characterisations and swelling behaviour / Mazrina Mazlan

Mazrina , Mazlan (2021) Modified guar gum-based hydrogels: Synthesis, characterisations and swelling behaviour / Mazrina Mazlan. Masters thesis, Universiti Malaya.

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Abstract

The growing concern for synthetic materials that are primarily derived from petroleum and coal as raw materials for the manufacture of hydrogel has opened a field of research focused on nature-based products. Massive efforts are being taken on biopolymer-based hydrogels due to their abundance, renewability, biodegradability and biocompatibility. Modification of biopolymer by grafting as alternative hydrogels is a promising strategy for imparting beneficial properties on them. Guar gum has solubility in water, possesses uncontrolled and enormous swelling that restricts its potential to be used in diverse applications. Thus, in this study, native guar gum (Native GG) was modified into guar gum acetate (GGA) and phthaloyl guar gum (PHGG) by transesterification and phthaloylation, respectively. These two modified guar gums have better solubility in organic solvents such as dimethylsulfoxide and dimethylformamide. The success of these modifications was confirmed through Fourier-transform infrared spectroscopy with new characteristic peaks at 1733 cm-1 for GGA and 1709 cm-1 for PHGG. The degree of substitution of GGA was 5.65 meanwhile PHGG was 1.04 as determined from proton nuclear magnetic resonance spectroscopy. X-ray diffractometry results revealed that both GGA and PHGG are less crystalline compared to Native GG. GGA was found to be thermally more stable than Native GG while PHGG was slightly less thermally stable in comparison with Native GG. The swelling behaviour revealed that Native GG had the highest swelling equilibrium with 918.4 ± 46.6%, followed by PHGG with 537.0 ± 2.9% and GGA with 393.0 ± 13.4% in distilled water. These hydrogels (Native GG, GGA and PHGG) were found to be stimuli sensitive towards pH and ionic salt solution. The samples responded to simulated normal saline isotonic solution, showing lower swelling compared to swelling in distilled water. For simulated gastric fluid (SGF) medium, GGA showed higher swelling while Native GG and PHGG showed higher swelling in simulated intestinal fluid (SIF) medium. Therefore, these guar gum hydrogels have potential to be used in biomedical fields such as tissue engineering and drug-delivery.

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