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Phase Behavior of Poly(butyl acrylate) Networks in Nematic Liquid Crystal Solvents
Author(s) -
Vendamme Richard,
Bouchaour Tewfik,
Pakula Tadeusz,
Coqueret Xavier,
Benmouna Mustapha,
Maschke Ulrich
Publication year - 2004
Publication title -
macromolecular materials and engineering
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.913
H-Index - 96
eISSN - 1439-2054
pISSN - 1438-7492
DOI - 10.1002/mame.200300236
Subject(s) - liquid crystal , materials science , photoinitiator , acrylate , polymer chemistry , monomer , polymerization , polymer , swelling , chemical engineering , solvent , photopolymer , composite material , organic chemistry , chemistry , optoelectronics , engineering
Summary: This paper reports the phase behavior of photochemically crosslinked poly(butyl acrylate) networks in nematic liquid crystal (LC) solvents. The swelling properties are studied as a function of temperature for two low molecular weight nematic LCs, 4‐cyano‐4′‐pentylbiphenyl (5CB) and the eutectic mixture of cyanoparaphenylenes (E7). Chemically crosslinked polymer networks were formed by the UV radiation of initial solutions of the reactive monomer, butyl acrylate, a crosslinker (hexanediol diacrylate), and a photoinitiator. To obtain different network densities, the ratio of butyl acrylate to hexanediol diacrylate was varied prior to polymerization/crosslinking reactions. Immersion in an excess of the LC solvent allowed for the measurement of size increase by polarized optical microscopy in terms of temperature. Length, width, and diagonal ratios were calculated considering swollen to dry network states of the samples. In general, swelling leads to an increase in the network size by increasing the temperature with a significant dependence on the degree of crosslinking. A large shift in the swelling ratio was found in the vicinity of the nematic to isotropic transition temperatures of the LCs.