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Novel nematic bis‐1,5‐hexadiene monomers: Synthesis and photopolymerization to cholesteric polymer networks
Author(s) -
Pfeuffer Thomas,
Kürschner Kathrin,
Strohriegl Peter
Publication year - 1999
Publication title -
macromolecular chemistry and physics
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.57
H-Index - 112
eISSN - 1521-3935
pISSN - 1022-1352
DOI - 10.1002/(sici)1521-3935(19991101)200:11<2480::aid-macp2480>3.0.co;2-4
Subject(s) - photopolymer , liquid crystal , monomer , mesophase , acrylate polymer , materials science , polymer chemistry , polymer , refractive index , phase (matter) , acrylate , photochemistry , chemistry , organic chemistry , composite material , optoelectronics
The synthesis of two novel nematic monomers 1 a and 1 b with two polymerizable 1,5‐hexadiene groups is described. Their photopolymerization in the nematic mesophase has been investigated by photo‐DSC‐measurements and IR‐spectroscopy. The hexadienes photopolymerize within 30 min to a final conversion of 87% and thus slower than the corresponding acrylates. Mixtures of hexadienes and acrylates copolymerize and photopolymerization is finished after two minutes of UV‐irradiation. By mixing a nematic bis‐1,5‐hexadiene compound with a cholesterol bisacrylate, enantiotropic cholesteric phases are obtained. Photopolymerization of such mixtures in the liquid crystalline phase leads to crosslinking. Networks with reflection colors from red to blue are obtained by variation of the amount of the chiral component. The helical twisting power (HTP) for networks of the bishexadiene 1a and the cholesterol derivative 3 is HTP/ n = 5.6 μm –1 ( n : average refractive index) which is almost by 50% larger than the value for the corresponding bisacrylate network.