POLARIZED-LIGHT SCATTERING STUDY FROM GELATIN SOLUTIONS AND GELS

Polarized static laser light scattering experiments have been reported on dilute sols, semi-dilute sols and gels of gelatin in the concentra tion range of 0.05% to 10% (w/v) at various ionic strengths. The stati c structure factor S(q) and the helix contents chi of the gelling solu tions have been deduced from the measured intensity of scattered light , I-vv(q) data and compared with optical rotatory dispersion (ORD) mea surements. Below the threshold gelation concentration c, S(q) similar to q(-d) with d = 2.15 +/- 0.08 in conformity with Guinier results. A bove this concentration, at any temperature, S(q) could be empirically described as S(q)= (1 - chi)exp(-q(2)R(g)(2)/3) + chi exp(-q(2)L(2)); for R-g being the radius of gyration of gelatin chain and L being the length of the triple helices formed. In the gel state, this yielded t wo characteristic length scales; one corresponding to R-g (at large q) and another corresponding to L (at small q) as opposed to the single length scale R-g observed in all sol states. (C) 1998 Elsevier Science Ltd. All rights reserved.