运用插层法增强聚二炔的近红外吸收以改善其光声成像性能

Photoacoustic imaging is a noninvasive biomedical imaging technology developed recently. And the research on organic conjugated polymer as contrast agent becomes one of the hot topics in the field of photoacoustic imaging. Polydiacetylene is a biocompatible conjugated polymeric layered crystal. At the meantime, the fluorescence of blue-phase polydiacetylene was sufficiently forbidden, providing it an excellent photo-thermal conversion performance. However, it has the poor stability and relatively short wavelength. The proposed work will develop the novel blue-phase polydiacetylene composites with high stability and long wavelength by intercalating metal ions or molecules and optimizing the composite structures via the non-covalently connected micelle fabrication method and annealing method which have been developed by our group. The resultant composite has the strong near-infrared absorption and the excellent photoacoustic imaging performance. Moreover, the functional metal ions or molecules can also be intercalated into the polydiacetylene composites and achieve the multifunctional photoacoustic imaging. It can be considered as the ideal photoacoustic imaging contrast agent. Our preliminary results indicate that the metal ions intercalated polydiacetylene acid composites have effectively improved the stability of blue-phase polydiacetylene and increased the light absorption wavelength, which lays a solid foundation for the proposed work.

光声成像是近年来发展起来的一种无损生物医学成像技术。开发有机共轭高分子光声成像造影剂是光声成像研究的热点之一。聚二炔是具有良好生物相容性的共轭高分子层状晶体。同时，蓝相聚二炔荧光禁阻，赋予其优良的光热转换能力。但是蓝相聚二炔不稳定且吸收波长较短。本项目拟开发金属离子或小分子插层的聚二炔复合材料，并使用我组发展的制备非共价键连接胶束的方法和退火法优化复合物的结构，制备出高稳定性且长吸收波长的新型蓝相聚二炔复合材料，并使其具有较强近红外吸收和优良光声成像效果。此外，聚二炔插层复合材料中可负载功能化金属离子或分子，实现多功能光声成像，可称为理想的光声成像造影剂。目前，我们初步的研究结果表明金属离子插层的聚二炔酸体系能够有效地提高蓝相聚二炔稳定性并增加吸收波长，为本项目的开展打下良好的基础。

共轭高分子的性能与其有效共轭长度密切相关。由于其共轭主链通常由单键和共轭单元交替排列组成，主链会受到巨大的熵扰动，很难获得具有较长的有效共轭长度的共轭聚合物。仅通过调整共轭主链的构象来避免巨大的熵扰动是一个重要但又十分挑战的工作。本项目首次提出并实现了通过预组织完美的单体晶体结构抑制其聚合时共轭主链的熵扰动的新方法。该方法成功提升其有效共轭长度，实现在近红外区的吸收。并且该方法具有一定的普适性，不仅首次获得了长有效共轭长度的聚(10, 12-二十五二炔酸)还实现了多个具有较长有效共轭长度的金属离子和小分子/金属离子多组分插层的蓝绿相聚二炔酸复合材料体系。上述长有效共轭长度的聚二炔酸及其复合材料均具有显著的光声信号和相较于蓝相聚二炔酸更强的非线性光学响应。利用对聚二炔结晶侧链作用力的调控，实现对其聚二炔共轭主链构象调控的方法，首次成功地对聚二炔非线性光学模式进行调控。

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