Photopolymerization Induced Phase Transitions & Evolution of Morphology Landscape in Holographic Polymer Dispersed Liquid Crystals and Photonic Cyrstals

技术摘要：本奖项的重点是在聚合物和液晶混合物中的定向中间相有序，这些聚合物和液晶在制造主动和被动全息聚合物分散液晶和光子晶体的过程中受到光学干涉产生的强度梯度。光聚合诱导相变是由光化学反应驱动的一种现象，在光图案化过程中，由于光强梯度的作用，发生了定向相序现象。全息光聚合技术基于多波光学干涉原理，已被应用于全息聚合物分散液晶和光子晶体的制备以及相关电光器件的开发。全息成像的电光开关性能和衍射效率在很大程度上取决于球体条纹和/或球体阵列内两相结构的优化。结构有序化的动力学不仅取决于相变的热力学和动力学，还取决于纳米尺度在这些条纹中所产生的约束效应。在聚合物分散液晶基全息薄膜的受限纳米图形中，与各向异性相分离和扩散相关的纳米科学的理解对于实际应用是至关重要的。拟议的研究涉及几个信任领域；(I)光聚合引起的涉及相分离、结晶和中间相有序化的相变，(Ii)包含液晶和导电有机晶体的聚合物光子晶体系统的非平衡非线性动力学的粗粒度建模，(Iii)热梯度和光强梯度对定向有序化的影响，以及(Iv)在2-D和3-D光子带隙结构中对微结构发展的限制效应。因此，这种技术的发展对光学计算机和电信芯片至关重要。此外，拟议的柱状腔阵列研究如果成功，将立即导致应用，例如：(1)微孔隐形眼镜的制造将由于良好的透氧性而对当前市场产生很大影响。微孔阵列在充满水(即泪水)后，将表现为具有增强视力的微透镜，类似于一些昆虫的复眼，因此所提出的纳米多孔膜可以用作生物仿生膜。(2)在可混溶聚合物共混的情况下，可以产生折射率梯度结构，以产生光学质量的薄平板会聚透镜，这比现有的具有凸曲率的会聚透镜具有很大的优势。所提出的平面会聚透镜可能在空间有限的情况下用于成像。作为阿克伦大学阿克伦全球聚合物学院AGPA远程学习计划的一部分，首席研究人员(PI)小组将开发一项基于网络的全息成像实验。聚合物软物质中丰富的形态具有共同的起源，自然界中有多种形态，如雪花、冰晶、金属焊接和电化学沉积中的涂层生长。雪花状结构的生长将在课堂教学中以生活模式进行演示；这一主题将引起所有年龄段的学生(K12)和普通公众的兴趣。PI的团队将继续与莱特-帕特森空军基地的蒂姆·邦宁博士的团队合作。尽管PI的小组配备了全息光学设备(主要是Ar离子激光器)和时间分辨光散射来现场监测衍射效率，但空军小组配备了更好的UV激光，这无疑增加了使用商业光刻剂和基质树脂设计和制造光刻的灵活性。PI的小组已经展示了对全息聚合物分散液晶和光子晶体中微结构形成的理论建模和模拟能力，这对我们空军的同行来说是非常感兴趣的。

TECHNICAL SUMMARY:The present award focuses on the directional mesophase ordering in mixtures of polymers and liquid crystals subjected to intensity gradient created by optical interference during fabrication of active and passive-type holographic polymer dispersed liquid crystals and photonic crystals. Photopolymerization induced phase transition is a phenomenon driven by photochemical reaction, in which directional phase ordering occurs by virtue of light intensity gradient during photo-patterning. The holographic photo-polymerization technique operates based on the principles of optical interference of multiple waves that has been applied to fabrication of holographic polymer dispersed liquid crystals and photonic crystals, as well as development of related electro-optical devices. The electro-optical switching performance and diffraction efficiency of the holographic imaging critically depends on the optimization of the two-phase structure within the stripes and/or arrays of spheres. The dynamics of structure ordering again depends not only on thermodynamics and kinetics of phase transition, but also on the confinement effect caused by the nano-size within these striations. The understanding of nano-science associated with anisotropic phase separation and diffusion within the confined nano-patterns of polymer dispersed liquid crystals based holographic films is of paramount importance for practical applications. The proposed studies entail several trust areas; (i) photopolymerization-induced phase transitions involving phase separation, crystallization, and mesophase ordering, (ii) coarse-grain modeling of non-equilibrium non-linear dynamics of polymer photonic crystal systems containing liquid crystals and conductive organic crystals, (iii) effects of thermal gradient and light intensity gradient on directional ordering, and (iv) confinement effect on microstructure development in 2-D and 3-D photonic band-gap structures.NON-TECHNICAL SUMMARY Polymeric photonic band-gap structures operate on a similar principle to that of electronic transistors or semiconductor band-gap materials, except that information is transmitted through light which is faster than electrons, and thus the development of such technology is vital to optical computers and chips for telecommunications. In addition, the proposed studies on the arrays of columnar cavities, if successful, will lead to immediate applications, e.g., (1) fabrication of the microporous contact lens would have high impact on the current market by virtue of excellent oxygen permeability. The microporous arrays, upon filling with water (i.e., tear), would perform like microlens with enhanced vision similar to the compound eyes of some insects and thus the proposed nano-porous films may be used as bio-mimetic membranes. (2) In the case of miscible polymer blends, the refractive index gradient structure can be created to produce thin flat converging lens of optical quality which has great advantageous over the existing converging lens that invariably has convex curvatures. The proposed flat converging lens may be useful for imaging where space is limited. The Principle Investigator's (PI) group will develop a web-based experimentation on holographic imaging as part of the distant-learning program of the Akron Global Polymer Academy AGPA at University of Akron. The enriched morphologies in polymer soft matter share the common origin with a variety of patterns in nature such as snow-flakes, ice crystals, metal welding, and coating growth in electrochemical deposition. Growth of snow-flake-like structures will be demonstrated in life-mode during class-room teaching; this subject matter would be of interest to students of all ages (K12) and also to the general public. The PI's group will continue their collaboration with Dr. Tim Bunning's group at Wright-Patterson Air Force Base. Although the PI's group is reasonably equipped with the holographic optical equipment (primarily Argon ion laser) and time-resolved light scattering for in-situ monitoring of the diffraction efficiency, the Air Force group is better equipped with UV laser which certainly gives added flexibility in the design and fabrication of photolithography with commercially available photo-curatives and matrix resins. The PI's group has demonstrated capability of theoretical modeling and simulation on the formation of microstructures in holographic polymer dispersed liquid crystals and photonic crystals, which is of immense interest to our counterpart at the Air Force.