Novel liquid crystal resins for stereolithography: Mechanical and physical properties

This paper considers photocurable liquid crystal (LC) monomers which are a new class of stereolithography resins. These resins form polymers with high upper-use temperatures. The rodlike molecules can be aligned by an external force. When cured in an aligned state, the aligned structure is "locked in" resulting in materials with anisotropic physical and mechanical properties. FTIR spectroscopy, thermo-mechanical analysis (TMA), dynamic mechanical analysis (DMA), and large strain mechanical tests were applied to liquid crystal photo-polymers, both in the green state and after postcure. These measurements showed that the photo-polymerization reaction locked in the molecular order. Elastic modulus in the glassy state, revealed approximately a factor of two difference between the directions parallel and perpendicular to the alignment. Thermal expansion measurements showed an anisotropic linear expansion that was very small, and sometimes negative in the alignment direction. Finally, these resins demonstrated high glass transition temperatures which could be advanced to as high as 150 degrees C by postcuring.