Study for Two-Photon Photoresponsive Materials Based on π conjugated molecules and polymers

双光子激发引起的各种光化学反应，可以潜在地用于光阻和光图案形成过程。由于双光子诱导反应的可能性取决于光强度的平方，因此3D选择性光诱导反应和光图案形成是可能的，利用聚焦激光束作为光源，开发了新型的光响应聚合物和光致变色分子，并研究了它们的双光子诱导光响应性。响应性导电聚合物，其电导率可以通过光致变色反应来调节。由于光致变色二芳基乙烯化合物的对位共轭途径在其为闭环异构体时是通过分子间的连接实现的，而在开环异构体中则不是。因此，在主链上具有光致变色二芳基乙烯单元的导电聚合物的导电性预期通过光致变色反应可逆。事实上，我们的光致变色导电聚合物显示出电导率随光致变色反应的可逆变化。聚合物在飞秒超短脉冲聚焦激光照射下发生了可逆的双光子光致变色反应，由于双光子光致变色反应的可能性取决于分子的双光子截面，因此需要具有较大双光子吸收截面的双光子活性分子才能用于光响应分子和聚合物的实际应用。制备了具有增强的双光子吸收截面的新型光致变色分子，并首次用Z-扫描方法测量了它们的双光子吸收截面。它们的TPA横截面在6 GM和90 GM之间变化，这取决于分子结构和照射光的波长。

Two-photon excitation induces various photochemical reactions which can be potentially used for photo-resistive and photo-pattern formation processes. Since possibility of two photon induced reaction depends on square of light intensity, the 3D-selective photo-induced reactions and photo-pattern formations are possible, when focused laser beam is used as a light source.Novel photo-responsive polymers and photochromic molecules are developed and their two photon-induced photo-responsibility was studied.First issue is to develop novel photo-responsive conducting polymer whose electrical conductivity can be modulated with the photochromic reactions. Since pai-conjugation pathway of photochromic diarylethenes connects over the molecules when it is in the closed ring-isomer, but not in the open ring isomer. Therefore, electrical conductivity of a conducting polymer, which possesses photochromic diarylethene units on the main chain, is expected reversibly by the photochromic reactions. Indeed, our photochromic conducting polymer showed reversible changes in the electrical conductivity with the photochromic reactions. The polymer showed two-photon induced photochromic reactions reversibly when focused femto-sec ultra-short pulse laser beam was irradiated.Since possibility of the two photon induced photochemical reactions depends on the two photon cross-section of the molecules, two-photon active molecules with larger TPA cross-section is indeed required for practical use of the photo-responsive molecules and polymers. Novel photochromic molecules having enhanced TPA cross-section an prepared and their TPA cross-section are measured by the Z-scan method for the first time. Their TPA cross-section varies between 6GM and 90GM depending on the molecular structure and wavelength of the irradiated light.