含可控交联基团的二阶非线性光学聚合物的设计及其性能研究

Organic second-order nonlinear optical (NLO) materials have been identified as one of the key enabling elements to drive rapid development of optical modulators that can encode electrical signals into optical domain with low driven voltage and small device footprint. This is crucial to meet the energy reduction and bandwidth enhancement challenges with exponentially increasing demands to store, communicate, and compute information. The current research focus is to develop advanced second-order NLO materials that exhibit large Pockels coefficients, good thermal stability, high photo-stability, excellent optical transparency, and exceptional processibility to be integrated with other materials in the system. .A series of crosslinkable NLO polymer with controllable onset of curing group are designed and investigated in this project. Incorporation of the controllable group is to separate process of the poling and crosslinking reaction through an orthogonal initiation process. If the crosslinking process beginning too early, the bulk electro-optic activity of the final material might be limited. Suitable crosslinking reaction should be carefully selected to prevent decomposition of the chromophores with strong push-pull conjugated structure. Photo crosslinkable group was used for thermal-assisted poling and thermal crosslinkable group was used for photo-assisted poling. Crosslinking could be monitored by IR or UV-vis spectroscopy and optimal conversion will also be investigated. By molecular engineering of the shape, nonlinearity, Tg, and crosslinking moieties of the chromophores and polymers, we believe that materials with enhanced EO activities and temporal stability could be obtained.

有机非线性光学材料因其具有高响应、高集成及分子设计方面的高灵活性等优势而受到广泛关注，但是它的长期稳定性较差，限制了它进一步的应用与发展。交联是提高材料长期稳定性的一种有效手段，但由于交联反应难于控制致使大β值生色团易于分解或使生色团充分取向受限，往往导致材料的电光活性的下降。本课题拟通过初步筛选，将化学选择性高、反应条件温和且反应速率较快的可控交联基团引入二阶非线性光学聚合物体系，以确保大β值生色团不分解为前提，利用可控交联反应实现生色团充分取向后的原位交联固化；通过对交联基团在非线性光学薄膜中反应进程的监测以及材料电光系数和长期稳定性的研究，确立可控交联基团结构、含量与生色团稳定性的关系及其在聚合物薄膜中反应活性的关系，从而制备出电光系数高且长期稳定性佳的有机二阶非线性光学材料，为推动高性能有机非线性材料的应用和发展提供一定的科学依据。

有机非线性光学材料因其具有高响应、高集成及分子设计方面的高灵活性等优势而受到广泛关注，但是它的长期稳定性较差，限制了它进一步的应用与发展。交联是提高材料长期稳定性的一种有效手段，但由于交联反应难于控制致使生色团易于分解或使生色团充分取向受限，导致材料的电光活性的下降。.本课题通过初步筛选，确定光引发蒽基团[4+4]环加成反应选择性高、反应条件温和且反应速率较快。进而将其引入二阶非线性光学聚合物体系，设计合成系列蒽基团含量不同的聚芳醚酮（P1-P5）以及二、四功能化的生色团（C2、C4），制备聚合物掺杂薄膜，在确保生色团不分解的前提下，进行热辅助极化之后的光交联，实现极化生色团充分取向后的原位交联固化。采用DSC和TGA研究聚芳醚酮交联前后热稳定性，结果表明在交联后的聚芳醚酮热稳定性显著提高，其中聚芳醚酮P5热分解温度提高91℃。通过紫外吸收光谱、监测蒽基团的交联情况及交联反应同时生色团的稳定性，结果表明低功率手提紫外灯（4W）辐照即可引发交联反应，30 min即可完成交联反应。P5C4样品由于蒽基团的引入大大增加了生色团与聚合物的相容性，其电光系数最大可达28.5 pm/V，通过热释电流法（TSD）表征薄膜材料的取向稳定性，P5C4样品稳定性最佳，峰值温度可达130℃，较交联前最大提高了17℃。.以上研究结果表明，可控交联蒽基团的引入，有效的分离了交联与极化取向过程，提高了材料的稳定性的同时增大生色团与主体的相容性，从而提高材料电光系数。本项目研究为制备高性能有机非线性材料的提供了行之有效的设计思路，有利于推动有机材料在电光调制器的应用和发展。