Light-scattering studies in cross-linked gels: Evidence of a microphase separation

Norberto Micali, Cirino Vasi, Francesco Mallamace, Rama Bansil, Sinisha Pajevic, and Francesco Sciortino
Phys. Rev. E 48, 4501 – Published 1 December 1993
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Abstract

In this paper we report experimental results from depolarized Rayleigh, Brillouin, and elastic (zero-frequency intensity) scattering, on methyl-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 cm1 while the Brillouin and the zero-frequency intensity data are measured at different scattering wave vectors in the angular ranges 90°–150° and 10°–150°, respectively. The behavior of the measured quantities confirms that in these gels a microphase separation phenomenon takes place. In particular, for samples with cross-linking content higher than 3%, Brillouin data (studied in terms of the group velocity) give information about the existence of well-defined solidlike and liquidlike islands (heterogeneities in the gel structure) with an extent of several hundred angstroms (as confirmed by elastic-scattering data). Increasing the cross-link concentration in the gel seems to generate an increase in the number of the liquidlike islands, with a reduction in their corresponding size. Depolarized-light-scattering data show (in the same concentration region of EDMA) a change in the freely rotating terminal groups of the MMA polymer.

  • Received 8 February 1993

DOI:https://doi.org/10.1103/PhysRevE.48.4501

©1993 American Physical Society

Authors & Affiliations

Norberto Micali and Cirino Vasi

  • Istituto di Tecniche Spettroscopiche del Consiglio Nazionale delle Ricerche, 98166, Vill. S. Agata, Messina, Italy

Francesco Mallamace

  • Dipartimento di Fisica dell’Università di Messina, 98166, Vill. S. Agata, Casella Postale 55, Messina, Italy

Rama Bansil, Sinisha Pajevic, and Francesco Sciortino

  • Center for Polymer Studies and Department of Physics, Boston University, Boston, Massachusetts 02215

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Vol. 48, Iss. 6 — December 1993

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