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Macroporous Thermosets via Chemically Induced Phase Separation

Published online by Cambridge University Press:  15 February 2011

J. Kiefer
Affiliation:
Swiss Federal Institute of Technology, Materials Department, Polymers Laboratory CH-1015 Lausanne, Switzerland
R. Porouchani
Affiliation:
Swiss Federal Institute of Technology, Materials Department, Polymers Laboratory CH-1015 Lausanne, Switzerland
D. Mendels
Affiliation:
Swiss Federal Institute of Technology, Materials Department, Polymers Laboratory CH-1015 Lausanne, Switzerland
J. B. Ferrer
Affiliation:
Swiss Federal Institute of Technology, Materials Department, Polymers Laboratory CH-1015 Lausanne, Switzerland
C. Fond
Affiliation:
CNRS, Institut Charles Sadron, 6 rue Boussingault, F-67083 Strasbourg
J. L. Hedrick
Affiliation:
IBM Research Division, Almaden Research Center, 650 Harry Road San Jose, California 95120-6099
H. H. Kausch
Affiliation:
Swiss Federal Institute of Technology, Materials Department, Polymers Laboratory CH-1015 Lausanne, Switzerland
J. G. Hilborn
Affiliation:
Swiss Federal Institute of Technology, Materials Department, Polymers Laboratory CH-1015 Lausanne, Switzerland
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Abstract

We have explored a new technology based on chemically induced phase separation that yields porous epoxies and cyanurates with a closed cell morphology and micrometer sized pores with a narrow pore size distribution. When the precursor monomers are cured in the presence of a low molecular weight liquid, the desired morphology results from a phase separation and a chemical quench. After phase separation, the porosity is achieved by thermal removal of the secondary liquid phase, specifically by diffusion through the crosslinked matrix. In respect to the thermodynamics and kinetics, the origin of the phase separation process can be identified as nucleation and growth. The influence of internal and external reaction parameters, such as chemical nature of the low molecular weight liquid, its concentration and the curing temperature on the final morphology are presented. Thus, the morphology can be controlled ranging from a monomodal to bimodal pore size distribution with pore sizes inbetween 1 to 10 μm. These porous thermosets are characterized by a significantly lower density, without any loss in thermal stability compared to the neat matrix. Such new materials demonstrate great interest for lowering the dielectric constant and for improving the fundamental understanding of the role of voids in stress relaxation and toughening.

Type
Research Article
Copyright
Copyright © Materials Research Society 1996

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