Photochromic Dendrimers for Photoswitched Solid-To-Liquid Transitions and Solar Thermal Fuels.
Photochromic Dendrimers for Photoswitched Solid-To-Liquid Transitions and Solar Thermal Fuels.
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DOI：
10.1021/acsami.0c14160
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发表时间：
2020-10
影响因子：
9.5
通讯作者：
Xingtang Xu;Peng Zhang;Bo Wu;Youmei Xing;Ke Shi;Weihua Fang;Haifeng Yu;Guojie Wang
中科院分区：
文献类型：
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作者：
Xingtang Xu;Peng Zhang;Bo Wu;Youmei Xing;Ke Shi;Weihua Fang;Haifeng Yu;Guojie Wang
树枝状大分子是一类结构明确、高度支化的大分子，在催化、传感、生物医学等领域有着广泛的应用。在这里，我们提出了一种新的多功能光致变色树枝状大分子通过接枝偶氮苯单元到树枝状大分子，这不仅可以控制切换的粘合剂和涂层划痕的有效修复，但也实现了高性能的太阳能存储和按需热释放。含偶氮苯树枝状聚合物的可转换粘合剂和可修复涂层归因于可逆的固-液转变，因为反式异构体和顺式异构体具有不同的玻璃化转变温度。粘接强度随树枝状大分子代数的增加而显著增加，其中第五代光致变色树枝状大分子（G5-Azo）的粘接强度最高可达1.62 MPa，是原始偶氮苯的5倍。树枝状大分子太阳能热燃料的异构体具有不同的化学能，通过树枝状大分子上偶氮苯基团的扩增，可以显著提高其太阳能储存和放热性能。G5-Azo的储能密度可达59 W h kg-1，远高于原始偶氮苯的储能密度（36 W h kg-1）。G5-偶氮燃料在顺式异构体和反式异构体之间表现出5.2 °C的温差。这些发现为制备具有树枝状聚合物结构的光开关粘合剂和涂层以及太阳能热燃料提供了新的视角和非常有吸引力的途径。
Dendrimers are well-defined, highly branched macromolecules that have been widely applied in the fields of catalysis, sensing, and biomedicine. Here, we present a novel multifunctional photochromic dendrimer fabricated through grafting azobenzene units onto dendrimers, which not only enables controlled switching of adhesives and effective repair of coating scratches but also realizes high-performance solar energy storage and on-demand heat release. The switchable adhesives and healable coatings of azobenzene-containing dendrimers are attributed to the reversible solid-to-liquid transitions because trans-isomers and cis-isomers have different glass transition temperatures. The adhesion strengths increase significantly with the increase in dendrimer generations, wherein the adhesion strength of fifth-generation photochromic dendrimers (G5-Azo) can reach up to 1.62 MPa, five times higher than that of pristine azobenzenes. The solar energy storage and heat release of dendrimer solar thermal fuels, the isomers of which possess different chemical energies, can be also enhanced remarkably with the amplification of azobenzene groups on dendrimers. The storage energy density of G5-Azo can reach 59 W h kg-1, which is much higher than that of pristine azobenzenes (36 W h kg-1). The G5-Azo fuels exhibit a 5.2 °C temperature difference between cis-isomers and trans-isomers. These findings provide a new perspective and tremendously attractive avenue for the fabrication of photoswitchable adhesives and coatings and solar thermal fuels with dendrimer structures.