Effects of solvent perturbation on gelation driven by spinodal demixing

We study effects of solvent perturbation on kinetic competition between spi nodal demixing and gelation in agarose solutions at a concentration of 5 g/ l. Two different cosolutes (tert-butyl alcohol and trimethyl amine N-oxide) known for altering in opposite way solvent-mediated interactions are chose n. By rheometry, static and dynamic light scattering experiments, we show t hat the cosolute presence shifts the boundary of the instability region of solution leaving unaffected temperature and polymer concentration values re quired for percolation. Results suggest that an appropriate choice of quenc hing temperature and solvent allows controlling the gelation time and the g el structural properties. (C) 1999 Elsevier Science B.V. All rights reserve d.