J. Phys. II France
Volume 2, Numéro 12, December 1992
Page(s) 2081 - 2088
DOI: 10.1051/jp2:1992253
J. Phys. II France 2 (1992) 2081-2088

Brillouin scattering from cross-linked gels

Francesco Mallamace1, Norberto Micali2, Cirino Vasi2, Rama Bansil3, Sinisa Pajevic3 and Francesco Sciortino3

1  Dipartimento di Fisica, Universita' di Messina, 98166 Villagio S. Agata, C.P. 55, Messina, Italy
2  Istituto Tecniche Spettroscopiche del C.N.R., 98166 Messina, Italy
3  Center for Polymer Studies and Department of Physics, Boston University, Boston, MA 02215, U.S.A.

(Received 12 August 1992, accepted in final form 12 October 1992)

In this letter we report Brillouin scattering measurements on methyl-methacrylate (MMA) gels crosslinked with varying amounts of ethylene-dimethacrylate (EDMA). We find that the k dependence of the phase velocity changes on increasing the cross-link content. For higher concentrations of crosslink we observe maxima and minima in the k dependence of the phase velocity. We associate these minima and maxima with spatial inhomogeneities in the gel, with the formation of regions of low and high cross-link density, respectively. This micro-phase separation is frozen in by the presence of the already existing spanning network.

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