Carboxymethyl cassava starch (CMS) was synthesized and its hydrogels were prepared by
cross-linking it with di- or polyfunctional carboxylic acids using glutaric (CASXGLU), suberic
(CASXSUB), pimelic (CASXPIM) and butanetetracarboxylic acids (CASBTC) as the crosslinkers.
The characterization of the CMS showed that its degree of substitution was 0.86,
average molar mass (Mw) was 5.6  106 g mol1 and the 13C NMR showed strong peak at
d = 180.42 ppm which was assigned to the ACO carbon in the carboxymethyl group. The
absorption under load (AUL) and free swelling capacity (FSC) studies showed that the
hydrogels have fast swelling properties and that they reached equilibrium after 1 h. Furthermore,
all the hydrogels were sensitive to the increasing salt concentrations and pH
of the medium. Both AUL and FSC reduced in saline solution while their values increased
in alkaline buffer solutions. The result indicate that the difunctional carboxylic acids produced
hydrogels with stronger material functions compared with the polyfunctional carboxylic
acid and the order of increases in both AUL and FSC was CASXBTC, CASXPIM,
CASXSUB and CASXGLU.
 
Carboxymethyl cassava starch (CMS) was synthesized and its hydrogels were prepared bycross-linking it with di- or polyfunctional carboxylic acids using glutaric (CASXGLU), suberic(CASXSUB), pimelic (CASXPIM) and butanetetracarboxylic acids (CASBTC) as the crosslinkers.The characterization of the CMS showed that its degree of substitution was 0.86,average molar mass (Mw) was 5.6  106 g mol1 and the 13C NMR showed strong peak atd = 180.42 ppm which was assigned to the ACO carbon in the carboxymethyl group. Theabsorption under load (AUL) and free swelling capacity (FSC) studies showed that thehydrogels have fast swelling properties and that they reached equilibrium after 1 h. Furthermore,all the hydrogels were sensitive to the increasing salt concentrations and pHof the medium. Both AUL and FSC reduced in saline solution while their values increasedin alkaline buffer solutions. The result indicate that the difunctional carboxylic acids producedhydrogels with stronger material functions compared with the polyfunctional carboxylicacid and the order of increases in both AUL and FSC was CASXBTC, CASXPIM,CASXSUB and CASXGLU.
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