Anisotropically patterned photopolymerization-induced phase separation of self-assembled nano-composites with liquid crystals and multifunctional monomers

Thermodynamic phase diagrams of unpolymerized and photopolymerized (UV/laser) nematic liquid crystal (LC), multifunctional acrylate(s), and/or multi-walled carbon nanotube (MWNT) mixtures were established by using polarized optical microscope (POM) and differential scanning calorimetry (DSC). The study revealed an important observation that there existed a chimney type phase diagram between MWNT/LC mixtures. It has been shown for the first time that there is an appreciable alignment induced interaction between multi-walled nanotube and liquid crystal molecules. To highlight the importance of choice of initial conditions for photopolymerization reactions, phase diagrams were used as guidance for the dynamics of phase separation studies. The domain morphology resulting from phase separation induced by temperature quench and/or photopolymerization at various conditions (intensity, temperature) was investigated in-situ by using POM and P-DSC.; The photopolymerization behavior and reaction kinetics for a series of multifunctional acrylate monomer(s), LC and MWNT mixtures were experimentally characterized with particular attention paid on the determination of the kinetic rate constants of propagation and termination steps of photopolymerization. The parameters of the photopolymerization modeling can be extracted from the measurements of the kinetic data. Real time-IR instrument was modified in order to avoid the strong inhibition effect of atmospheric oxygen on the photopolymerization and to create a controlled temperature environment. A systematic study of the effect of various parameters (functionality, temperature, intensity, LC and MWNT) on the kinetics was also performed for these systems. In general, reaction diffusion was found to dominate the kinetics from the very beginning of the multifunctional acrylate photopolyemrization.; Self-assembly and orientation of carbon nanotubes through optical interference subjected to pattern-induced photopolymerization was applied into various multifunctional acrylate/LC/MWNT mixtures by using two-wave and four-wave interference technique. The final part of this study dealt with electro-optical properties of pattern-induced phase separated films. Detailed scanning electron microscope images revealed that MWNT bundles align perpendicular to film surface. Diffraction efficiency measurements showed little or no indication of switching response with the addition of MWNT.