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Molecular-level design of excellent reversible thermochromic polydiacetylene materials with the simultaneous enhancement of multiple performances
No full textRecently, colorimetrically reversible materials have been paid significant attention not only to gain a better understanding of the fundamentals of their chromism but also to create ways to overcome the limitations associated with their colorimetrically irreversible counterparts. Generally, the properties of polydiacetylene (PDA)-based supramolecular materials strongly depend on their molecular packing structures, and the blue-colored PDAs undergo a color change to red when they are exposed to various stimuli. To achieve the reversible structural transition, we rationally designed a new L-Glu (L-glutamic acid)-derivatized diacetylene (DA–Glu) monomer to enhance the hydrogen-bonding interactions. Then, we developed a method to fabricate PDA–Glu/PDMS films, which could be readily obtained by mixing the PDMS precursor with the DA–Glu monomers, curing at an optimal temperature, and subjecting to UV irradiation. The prepared PDA–Glu/PDMS film showed excellent reversible thermochromism property when the temperature changed from 20 to 80 °C. Deep investigations revealed that the reversible thermochromism behavior could be attributed to the enhanced hydrogen-bonding interactions and the formation of a network structure in the PDA–Glu/PDMS film, which provided sufficient recovery force and free space for the PDA–Glu structures to reversibly vary with temperature. Further studies demonstrated that the formation of unique network structures did not only endow the PDA–Glu/PDMS film with excellent reversible thermochromism property, but also with good thermal stability and mechanical property. We believe that combining the waterproof property and other advanced properties of PDMS, the prepared PDA–Glu/PDMS films would present very promising applications in many fields. Our research opens a new way to improve the performance of materials and bestow them with novel properties by modifying the monomers at the molecular level.</p
Evolution of historical sediment yield using check-dam systems as carriers: A case study in a restored agricultural catchment on the Loess Plateau, China
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科技期刊数字学术服务概念、内容与现状
No full text【目的】阐述并构建数据驱动和开放科学环境下科技期刊数字学术服务的概念、服务内容及服务组成框架，为科技 期刊更好地开展数字学术服务提供借鉴。【方法】首先采用文献调研法对数字学术服务及相关研究进行分析，总结归纳科 技期刊数字学术服务的概念，并对数字学术服务内容的过程和层次进行分析; 其次，运用案例调研法，对科技期刊数字学术 服务实现情况进行调研与分析; 最后，提出科技期刊开展数字学术服务的建议。【结果】科技期刊数字学术服务的概念包含 服务主体等 5 个方面，服务内容则包括数字出版与知识服务、科研数据服务等 7 个方面; 科技期刊开展的数字学术服务分别 是期刊综合数据库层面、专业期刊集群层面和单刊层面; 所开展的数字学术服务内容与服务深度、与科研的融合程度、辅助 科研的程度各异。【结论】我国科技期刊在数字学术服务方面还存在很大的发展空间，与国外科技期刊数字学术服务相比 还有较大差距。我国科技期刊出版者还需要更加深入了解数字学术服务，不断提升数字学术服务能力。</p