【作者】 王毅；

【导师】 张晓安；

【作者基本信息】 吉林大学 ， 有机化学， 2016， 博士

【摘要】 力致变色材料,顾名思义是指光学行为(如吸收、反射、荧光、磷光等)在外界力刺激作用下能够发生可逆改变的一类功能材料。因其在力传感、记忆芯片和防伪墨水等领域有着重要的应用前景,力致变色材料在近年来受到越来越多的关注。但是由于力致变色材料的发展相对较晚,到目前为止,力致变色材料的种类仍然有限,且其实际应用也只停留在一些概念产品的展示上,远不能满足实际应用的要求。因此,发展新型力致变色材料和拓展实际应用范围是目前力致变色材料领域的研究重点。从不同的作用机制出发,本论文设计合成了基于分子内构象改变、分子内弱共价键异裂和分子间质子转移的三类新型力致变色材料,同时开发了它们在防伪﹑无墨书写和压力传感方面的应用。在第二章中,通过对分子几何构象的分析,我们发现四苯基乙烯(TPE)化合物的力惰性是来自于其高度对称的几何构象。因此,我们提出单臂延长降低四苯基乙烯高度对称性的方法去构筑新型力致荧光变色材料。基于这个方法,我们成功发展了一类新的全色可调(~450 nm到~740 nm)的力致荧光变色材料。这些材料具有较高的固态荧光量子效率(Φf>10%)和力致荧光变色对比度(最大荧光发射峰位移动在50 nm到100 nm之间)。更重要的是,我们发现了一个新的激发波长依赖的荧光发射现象,并提出把该现象作为一个新的、更加全面的关于荧光材料力响应性能的评价标准。最后,由于四苯基乙烯及其衍生物能够通过改变激发光来实现多重的荧光发射,它们被用在双通道的荧光防伪中。在第三章中,我们首次观察到了苯并[1,3]噁嗪分子开关OX-1即使在禁锢的晶体环境中也存在一个动态的开关互变异构平衡(常压下大约有8%的开环异构体)。有趣的是,该动态的开关互变异构平衡能够定量的被各向同性的静水压进行调控。当压力从常压升高到10 GPa时,OX-1开环异构体的比例能够从常压下的8%提高到大约83%,同时伴随着OX-1晶体连续并且大范围的吸收光谱变化(从~430 nm到~700 nm),这几乎覆盖了整个可见光区。对于小分子晶体而言,如此大范围的﹑连续的吸收光谱调节是首次被报道。通过详细的研究,我们认为OX-1在晶体中具有压力可调的开关互变异构平衡是来自于它两种异构体之间相对较小的互变异构能垒和两种异构体本身具有的不同压缩性;大范围光谱变化主要来自于其互变异构平衡的移动。最后,由于OX-1在压力条件下具有一系列肉眼可辨的颜色变化,它在可视化压力传感方面有着重要的应用前景。在第四章中,我们设计合成了一类新型的扭曲共轭酸碱两性分子,该类分子具有动态的分子间质子转移行为,不过它们在常温常压下发生质子转移的比例很少,一般在千分之一的数量级。然而,当受到外部力作用时,它们的分子间质子转移过程能够被显著加速;在各向异性力(即机械研磨)和各向同性力(即静水压)作用下,分子间质子转移比例分别提高到10%左右和60%以上。由于扭曲共轭酸碱两性分子在质子转移前后具有明显的颜色变化,因此它们是一类理想的力致变色材料,在无墨书写和力传感方面有着广泛的应用前景。总之,基于不同的作用机制,我们设计合成了三类新型的力致变色材料,在丰富力致变色材料种类的同时也对新型力致变色材料的设计合成提供了一些参考。更多还原

【Abstract】 Mechanochromic materials are a unique family of smart materials, whose optical behavior(such as absorption, reflection, fluorescence and phosphorescence) can undergo reversible changes under external force stimuli. Because mechanochromic materials have wide potential applications in mechanosensors, memory chips and security ink, they have attracted more and more attention in recent years. However, up to now, the families of mechanochromic materials are still limited and the applications of mechanochromic materials are mostly conceptual demonstrations, which cannot satisfy the requirement of practical applications. Therefore, present studies on mechanochromic materials are mostly focused on developing new mechanochromic materials and extending their practical applications. Starting from different mechanochromic mechanisms, we have developed three kinds of new mechanochromic materials based on intramolecular conformation changes, the heterolytic cleavage of intramolecular weak bond and intermolecular proton transfer, respectively. In addition, we have demonstrated their potential applications in anti-counterfeiting, ink-free writing and pressure-sensor.In the second chapter, we find that the inertness of tetraphenylethylene(TPE) to mechanical force comes from its high symmetrical molecular conformation by analyzing its molecular geometrical conformation. Thus, we have proposed a single-arm extended strategy to fabricate tetraphenylethylene-based mechanochromic materials. Based on this strategy, we have successfully developed a new series of full-color(from ~450 nm to ~740 nm) tunable mechanofluorochromic materials. These materials exhibit efficient solid-state emission(quantum yield Φf >10 %) and high mechanofluorochromic contrast(wavelength shift from ~50 nm to ~100 nm). More importantly, we have discovered an unexpected excitation-dependent emission phenomenon of mechanofluorochromic materials and proposed to utilize this new excitation-dependent emission behavior of materials to evaluate their mechanical-responsive performances more comprehensively. Finally, the unique feature of abundant emissions of mechanofluorochromic materials by changing the excitation lights has shown the application potentials in dual channel anti-counterfeiting.In the third chapter, we are the first to observe the dynamic tautomerization equilibrium(around 8 % ring-open isomers under ambient pressure) of benzo[1,3]oxazine OX-1 in constraint crystal environment. Interestingly, the dynamic tautomerization equilibrium can be quantitatively controlled by hydrostatic pressure. When pressure is increased to 10 GPa from ambient pressure, the proportion of ring-open isomers of OX-1 can reach around 83 % from 8 % under ambient pressure. In the meanwhile, the absorption spectra of OX-1 are red-shift to around 700 nm from around 450 nm, which almost cover the whole visible light region. For a small organic crystal, such a continuous and large-scale absorption modulation is the first to be reported. After detailed studies, we think that the pressure-controllable molecular tautomerization should come from the low tautomeric energy barrier of tautomerization and the different compressibility of two isomers. The large-scale absorption modulation of OX-1 crystal mainly comes from the tautomerization equilibrium shifting. Finally, OX-1 has been used as a visual pressure-sensor due to the continuous and naked-eye distinguished color changes under pressure.In the fourth chapter, we have designed and synthesized a new family of twisted and conjugated acid-base amphoteric molecules. This kind of molecules have dynamic intermolecular proton transfer behavior with quite small amount(around 1 ‰) under ambient condition. However, when exerted on external forces, their intermolecular proton transfer processes can be significantly accelerated; anisotropic force(namely mechanical grinding) and isotropic force(namely hydrostatic pressure) can increase the proportions of intermolecular proton transfer to around 10 % and more than 60 %, respectively. Because there are obvious color changes involved in the intermolecular proton transfer processes of twisted and conjugated acid-base amphoteric molecules, they are good candidates for mechanochromic materials with the potential applications in ink-free writing and pressure-sensor.In conclusion, we have developed three kinds of new mechanochromic materials based on different mechanochromic mechanisms, which not only enriches mechanochromic materials, but also provides some references for designing new mechanochromic materials.更多还原