A review with 35 refs. on various possibilities of making structured, oriented polymer films by in situ photopolymn. of pre-ordered liq.-cryst. monomers. Formation of uniaxially oriented films and their basic process parameters and the formation of superstructures with high degrees of director control are discussed. Photoinitiated polymn. of pre-oriented mesogenic polyfunctional monomers yields films of densely crosslinked polymers with a monodomain liq.-cryst. mol. order. The morphol. of the monomer mesogenic phase is fixed by the rapid photocrosslinking, which enables the formation of either nematic or one of the various smectic structures, depending on the phase behavior of the monomers. The desired macroscopic mol. order in the monomeric state can be accomplished by using techniques such as external fields or surface-induced orientation. Surface structures are also produced by replication polymn., and combinations of these techniques enable the modulation of the orientational director in the plane of the films and also into the third dimension perpendicular to the film surface. Photocrosslinking enables lithog. techniques to fix the director selectively by local polymn., before permanently fixing the total structure. The introduction of chiral centers in the liq.-cryst. monomers produces helicoidally ordered networks, whose pitch of the mol. helix can be adjusted accurately by compn. or by polymn. temp. This fine tuning of 3-D mol. orientation within thin polymeric films makes this process very unique in the world of oriented polymers.
|Title of host publication
|Desk reference of functional polymers : syntheses and applications
|Place of Publication
|American Chemical Society
|Published - 1997