N. Micali et al., LIGHT-SCATTERING-STUDIES IN CROSS-LINKED GELS - EVIDENCE OF A MICROPHASE SEPARATION, Physical review. E, Statistical physics, plasmas, fluids, and related interdisciplinary topics, 48(6), 1993, pp. 4501-4509
In this paper we report experimental results from depolarized Rayleigh
, Brillouin, and elastic (zero-frequency intensity) scattering, on met
hyl-methacrylate (MMA) gels cross-linked with ethylene-dimethacrylate
(EDMA). The study is performed by varying the cross-linking amount of
the gels from 0 to 6%. The depolarized Rayleigh scattering is studied
in the frequency range 0-150 cm(-1) while the Brillouin and the zero-f
requency intensity data are measured at different scattering wave vect
ors in the angular ranges 90 degrees-150 degrees and 10 degrees-150 de
grees, respectively. The behavior of the measured quantities confirms
that in these gels a microphase separation phenomenon takes place. In
particular, for samples with crosslinking content higher than 3%, Bril
louin data (studied in terms of the group velocity) give information a
bout the existence of well-defined solidlike and liquidlike islands (h
eterogeneities in the gel structure) with an extent of several hundred
angstroms (as confirmed by elastic-scattering data). Increasing the c
ross-link concentration in the gel seems to generate an increase in th
e number of the liquidlike islands, with a reduction in their correspo
nding size. Depolarized-light-scattering data show (in the same concen
tration region of EDMA) a change in the freely rotating terminal group
s of the MMA polymer.