A NEW APPROACH FOR ESTIMATING THE CROSS-LINK DENSITY OF COVALENTLY CROSS-LINKED IONIC POLYSACCHARIDE GELS

For an ideal polysaccharide gel with a known total polymer chain conto ur length, crosslinks all of the same functionality and elastic chains all with the same contour length and stiffness, the gel crosslink den sity can readily be determined from measurements of the maximum volume of the swollen gel (Moe et al., (1991) Food Hydrocolloids, 5, (1/2), 119-23. In the case of randomly crosslinked polysaccharide gels, where the chain contour length between two adjacent crosslinks may vary gre atly, it is often much more difficult to determine the crosslink densi ty. This paper reports on an attempt to extend the use of maximum gel volume measurements to estimate crosslink density for the latter type of gel. This is done by calculating the maximum swelling volume for po lymer networks with four-functional crosslinks, known elastic chain me an contour length and standard deviation. The numerical analysis invol ves the calculation of the equilibrium force at each crosslink as the network expands. This allows a detailed study of how the distribution of individual polymer chain contour lengths affects the maximum swelli ng volume. The computer simulation results are compared with the resul ts from experimental measurements of the maximum volume of swollen cov alently crosslinked sodium alginate gels.