Article,
Scleroglucan gelation by in situ neutralization of the alkaline solution
Biomacromolecules, 4 (4): 914 -- 921 (July 2003)
Abstract
Scleroglucan gels were prepared by neutralization of aqueous alkaline
solution of scleroglucan by in situ release of acid. Transition of
scleroglucan chains in a disordered state to the triple-helical state
result in cross-linking of the polysaccharide. The pH and the storage
and loss moduli, G' and G", were determined as a function of time
after initiating the pH reduction. Experiments were performed in
the temperature range from 20 to 90 degreesC and in the polymer concentration
range from C-p = 10-200 mg/mL. The concentration dependence of the
apparent plateau value of the storage modulus showed a lower critical
concentration, C-p,C-0,C- in the range 12-15 mg/mL needed for gelation
and a second power dependence of G' on concentration in the range
50-200 mg/mL. In situ pH reduction was achieved using formamide (methanoic
acid) or ethyl acetate (ethyl ethanoate) which hydrolyze in alkaline
solution, yielding carboxylic acids. The more rapid hydrolyses of
ethyl acetate compared to formamide yielded a faster decrease of
pH in solution and a more rapid increase of the storage modulus.
The present gelation process of scleroglucan based on the in situ
reduction of pH has advantages in applications where external control
of the conditions is difficult to achieve.
Tags
- ;;
- aqueous-solution;
- behavior;
- conformational
- electron-microscopy;
- gels
- kinetics;
- melting
- order-disorder
- polysaccharide;
- schizophyllan;
- system;
- transition;
- transitions;
- triple-helical
- [isi:]
