光聚合物/液晶/上转换纳米晶复合材料的全息图像存储与加密

The development of optical composites with multiple anti-counterfeiting functions which are able to be easily identified while covertly encrypted, is of essential significance to accelerate the advance of high-end anti-counterfeiting techniques, to efficiently defeat the forgery, and to secure the national economy. In this proposal, novel polymer nanocomposites are designed with concurrent functions of colored 3D holographic images identifiable to the naked-eye and multicolor upconversion encryption. First, lanthanide ion doped upconversion nanocrystals (UCNC), with tunable crystal phases, crystal sizes and luminescence colors, will be synthesized via the hydrothermal technique. Subsequently, these UCNC are going to be surface treated via silanization and thiol-ene click reaction, offering three types of surface-functionalized UCNC, i.e., thiol, mesogenic unit and poly(ethylene glycol) methyl ether functionalized UCNC, respectively. Following, uniform dispersions will be formed by adding the surface-functionalized UCNC into the homogeneous mixtures composed of thiol-allyl ether-acrylate hybrid monomers and liquid crystals. Upon exposure of these dispersions to laser interference patterns, photopolymer/liquid crystal/UCNC holographic composites in ordered structure will be formed. During this process, simultaneous holographic image storage and upconversion encryption are going to be implemented. In addition, the decryption is able to be easily implemented by taking advantage of the specific upconversion luminescence when exposed to near-infrared light. Based on above research, the influence of UCNC on the recorded image quality and the dependence of upconversion encryption resolution on the composite segregation degree are also expected to be depicted. This novel paradigm proposed herein is envisioned to afford basic theories to the development of advanced anti-counterfeiting protocols and the construction of ordered polymer nanocomposites.

发展识别便捷、加密隐蔽且具有多重防伪功能的光学复合材料对推动高端防伪技术进步、有效打击假冒伪造和保障国家经济安全具有重要意义。本项目设计了兼具彩色3D全息图像裸眼识别和多颜色上转换加密功能的新型聚合物纳米复合材料。采用水热法合成晶型结构、晶体尺寸及发光颜色可调的镧系离子掺杂上转换纳米晶，通过硅烷化和硫醇-烯烃点击反应在其表面分别引入硫醇、液晶基元和聚乙二醇甲醚。然后将修饰过的上转换纳米晶与硫醇-烯丙基醚-丙烯酸酯复合单体及液晶混合得到均匀分散液。在相干激光下，分散液通过光聚合诱导相分离，制得结构有序的光聚合物/液晶/上转换纳米晶全息复合材料，实现全息图像存储及上转换加密。进一步采用近红外光辐照以产生特定波长发光实现解密。通过上述研究，揭示上转换纳米晶对全息图像存储质量的影响规律，阐明多颜色上转换加密的分辨率对复合材料相分离程度的依赖关系，为发展先进防伪技术和建立有序复合新方法提供基础理论。

发展识别便捷、加密隐蔽且具有多重防伪功能的光学复合材料对于推动高端防伪技术进步、有效打击假冒伪造和保障国家经济安全具有重要意义。本项目通过单体/液晶/上转换纳米晶均匀复合体系在相干激光辐照下的聚合诱导相分离过程构筑亚微米尺度结构有序的新型聚合物纳米复合材料，集成全息图像的显性防伪功能和上转换发光的隐蔽加密功能，为发展先进防伪技术和建立有序复合新方法提供理论基础。其中的关键科学问题是：(I)单体/液晶/上转换纳米晶多相多组分复合体系在亚微米尺度上的有序相分离行为调控；(II)同步增强复合材料全息功能和上转换发光功能的多相多组分协同策略。针对上述科学问题，本项目基于课题组在前期工作中提出的“光引发阻聚剂”概念，取得了如下重要进展：①明确了光敏剂香豆素酮分别发生光氧化和光还原反应时的产物结构，阐明了反应产物对光聚合反应动力学和光流变行为的影响规律；②通过与外源阻聚剂对照，证实了“光引发阻聚剂”在优化全息光聚合物复合材料有序相分离结构和光学性能方面的独特作用；③建立了通过将上转换纳米晶富集在聚合物相，与液晶相产生协同效应，实现全息光学性能和上转换发光性能同步提升的结构有序复合材料构筑新方法，制得了兼具彩色全息图像裸眼识别和红、绿、蓝等多颜色上转换加密/解密功能的新型光学防伪材料；④发现当上转换纳米晶表面的油酸/水配体质量比介于2.41-7.65时，核-壳结构上转换纳米晶与单体/液晶复合体系的相容性显著改善，进一步提升了全息光聚合物复合材料的上转换发光性能；⑤在核-壳-壳结构上转换纳米晶的最外壳层中负载有机染料，利用染料与纳米晶内核的能量转移效应以及染料的光漂白反应在全息光聚合物复合材料中存储和显示了上转换发光图像，创制了全息、上转换发光双重图像正交存储与无串扰显示的新材料。