Jm. Sands et al., Synthesis and properties of elastomer-modified epoxy-methacrylate sequential interpenetrating networks, J APPL POLY, 81(3), 2001, pp. 530-545
The structure and properties of copolymerized sequential-interpenetrating n
etworks (SeqIPNs) synthesized from amine-cured epoxies and free-radical pol
ymerized dimethacrylates were examined. Materials were synthesized with and
without the incorporation of an epoxy-terminated butadiene-nitrile reactiv
e elastomer. Synthesis proceeded through full thermal cure of the epoxy-ami
ne network, followed by polymerization of the methacrylate network. The met
hacrylate reactions were free-radically induced using thermal (peroxide-ini
tiated) or photochemical [electron-beam (e-beam)] techniques. Fourier trans
form infrared spectroscopy was used to monitor epoxy-amine step-growth poly
merization in situ and to measure final cure conversion of methacrylates. S
tructural examination of the IPNs using atomic force microscopy and scannin
g electron microscopy revealed microphase separation in the neat-SeqIPN mat
erials and macroscopic phase separation of rubber-rich domains for elastome
r-modified networks. Dynamic mechanical analysis of the SeqIPN determined t
hat the properties of the network are strongly dependent on the cure condit
ions. Furthermore, the viscoelastic behavior of the e-beam-cured SeqIPN cou
ld be adequately described by the Williams-Landel-Ferry and Kohrausch-Willa
ms-Watts equations, presumably because of a strong coupling between the epo
xy-amine and methacrylate networks. (C) 2001 John Wiley & Sons, Inc.