Volume holographic storage and multiplexing in blends of PMMA and a block methacrylic azopolymer, using 488nm light pulses in the range of 100ms to 1s

An Electron Spin Resonance Study Comparing Nanometer-Nanosecond Dynamics in Diblock Copolymers and Their Poly(methyl Methacrylate) Binary Blends

Block copolymers are a class of materials that are particularly interesting with respect to their capability to self-assemble in ordered structures. In this context, the coupling between environment and dynamics is particularly relevant given that movements at the molecular level influence various properties of macromolecules. Mixing the polymer with a second macromolecule appears to be an easy method for studying these relationships. In this work, we studied blends of poly(methyl methacrylate) (PMMA) and a block copolymer composed of PMMA as the first block and poly(3-methyl-4-[6-(methylacryloyloxy)-hexyloxy]-4'-pentyloxy azobenzene) as the second block. The relaxational properties of these blends were investigated via electron spin resonance (ESR) spectroscopy, which is sensitive to nanometric length scales. The results of the investigations on the blends were related to the dynamic behavior of the copolymers. At the nanoscale, the study revealed the presence of heterogeneities, with slow and fast dynamics available for molecular reorientation, which are further modulated by the ability of the block copolymers to form supramolecular structures. For blends, the heterogeneities at the nanoscale were still detected. However, it was observed that the presence of the PMMA as a major component of the blends modified their dynamic behavior.

Polarization Gratings in Azobenzene-Based Fully Liquid Crystalline Triblock Copolymer

Photosensitive liquid crystalline (LC) block copolymers are a universal platform for designing functional materials for optics and photonics. Here, azobenzene LC ABA triblock copolymer containing mesogenic groups in each block is studied as a medium for the recording of polarization holographic gratings. The fast recording of polarization gratings is successfully performed with two orthogonally circularly polarized light beams of a 532-nm laser. It is shown that annealing of the recorded polarization grating increases diffraction efficiency considerably, by a factor of 70, and provokes simultaneous erasing of the surface relief grating if it has been recorded. Holographic behavior of the triblock copolymer is compared with that of an azobenzene homopolymer and a random copolymer, which has the same monomer ratio as the triblock copolymer. The obtained results are expected to allow designing new materials for the polarization of optical elements and holographic data storage.