We have utilized the fact that syndiotactic and isotactic Poly(methyl methacrylate) {PMMA} form a stereocomplex to spin semi-crystalline PMMA fibers. Our goal is to produce oriented semi-crystalline fibers with a high enough melting point to withstand atactic-PMMA processing conditions. We successfully developed stereocomplex PMMA fibers by wet spinning and gel spinning, and characterized their properties by means of differential scanning calorimetry, optical/electron microscopy, mechanical testing and X-ray crystallography. Stereocomplex fibers from gel spinning have highest melting points and polymer chain orientation, hence are the best reinforcing agents. We are currently working on producing self-reinforced composites using these fibers.

Conventional Ge2Sb2Te5 (GST) was modified by adding up a small amount of SiOx, using co-sputtering technique from multiple targets. The SiOx content was gradually increased by increasing the power applied to SiOx target, up to 8 volume percent. The sheet resistance of SiOx-containing GST exponentially increased, when the room-temperature-deposited samples were annealed at 300 °C. Transmission electron microscopy images revealed that no SiOx particulates were formed, which was confirmed by Gattan image filtering. It was indicated by x-ray diffraction patterns that the grain size of SiOx-containing GST is smaller than normal GST with lattice locally distorted at its crystalline state, suggesting that molecular SiOx is homogeneously distributed throughout the GST matrix. We observed that the crystallization temperature of SiOx-containing GST is gradually elevated by increasing the SiOx content, while the melting point decreased. These observations led to the reset current reduction, which is a critical requirement for the high density PRAM.

We describe a new polymer patterning technique that produces controllable morphological and optical anisotropy in a polymer network. This technique is based on the use of pattern-forming states of nematic and cholesteric liquid crystals as templates for forming ordered polymer networks. One and two-dimensional optical patterns are induced by applying an electric field across a narrow gap of an electro-optical cell. These field-induced optical patterns are then stabilized by UV-induced polymerization of a typically 5 wt% reactive monomer in liquid crystal host. Depending on specific conditions (e.g., thickness to pitch ratio of a cholesteric, applied electric field, and wavelength of UV illumination), the polymer captures various degrees of the orientational order and spatial periodicity of the pattern-forming states of liquid crystals. The fidelity of the templating effect is explored using polarizing optical microscopy and SEM. We also describe the effect of UV wavelength on the network morphology and the morphological control over the”third” dimension (normal to the cell substrates).

Poly(CMPV-co-PV) have been synthesized via water soluble sulfonium salt precursor route and their linear and non-linear optical properties were characterized. The electro-optic response was stable up to 100°C when the materials were poled during the elimination. The thermal stability and mechanical strength of PPV and its derivatives, and easy processibility from the precursor polymers suggest a new approach for the molecular design of the 2nd order non-linear optical polymers.