Dimerization of sub-nanoscale molecular clusters affords broadly tuneable viscoelasticity above the glass transition temperature.
Dimerization of sub-nanoscale molecular clusters affords broadly tuneable viscoelasticity above the glass transition temperature.
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亚纳米级分子簇的二聚化在玻璃化转变温度以上提供了广泛可调的粘弹性
DOI：
10.1039/d2sc03651g
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发表时间：
2022-10-12
期刊：
影响因子：
8.4
通讯作者：
中科院分区：
文献类型：
--
作者：
具有良好机械性能的材料通常表现出对其关键构建单元的临界尺寸的要求，例如纠缠和晶粒。在此，仅通过范德华相互作用，就可以在低于临界尺寸限制的情况下轻松实现具有广泛可调性的粘弹性：〜1 nm多面体低聚倍半硅氧烷（POSS）的二聚体，其Mw < 4 kD且尺寸< 5 nm，与POSS的聚合物纳米复合材料相比，其表现出独特的材料物理特性。通过散射和量热测量证实二聚 POSS 是玻璃化转变温度 (Tgs) 低于室温的本征玻璃态材料。根据流变学研究，它们的粘弹性可以通过简单调整高于其 Tg 的二聚体连接体结构来调节。在二聚体块体中，每个 POSS 簇在空间上受到来自其他二聚体的 POSS 的限制，因此，两个连接的 POSS 簇的动力学相关性（如动力学分析所示，由连接体的长度和灵活性调节）有助于 POSS 受其邻居限制的笼动动力学以及由此产生的独特粘弹性。我们的发现更新了对粘弹性结构起源的理解，并开辟了从亚纳米级构建块的设计中制造结构材料的途径。一般结构材料设计的临界尺寸限制在亚纳米分子簇二聚体中受到挑战，这些二聚体具有小尺寸（<5 nm）和广泛可调的粘弹性。
Materials with promising mechanical performance generally demonstrate requirements for the critical sizes of their key building units, e.g. entanglements and crystal grains. Herein, only with van der Waals interaction, viscoelasticity with broad tunability has been facilely achieved below the critical size limits: the dimers of ∼1 nm polyhedral oligomeric silsesquioxane (POSS) with Mw < 4 kD and size < 5 nm, which demonstrate distinct material physics compared to that of polymer nanocomposites of POSS. The dimeric POSSs are confirmed by scattering and calorimetrical measurements to be intrinsic glassy materials with glass transition temperatures (Tgs) lower than room temperature. From rheological studies, their viscoelasticity can be broadly tuned through the simple tailoring of the dimer linker structures above their Tg. In dimer bulks, each POSS cluster is spatially confined by the POSSs from other dimers and therefore, the correlation of the dynamics of the two linked POSS clusters, which, as indicated by dynamics analysis, is regulated by the length and flexibilities of linkers, contributes to the caging dynamics of POSS confined by their neighbours and the resulting unique viscoelasticity. Our discoveries update the understanding of the structural origin of viscoelasticity and open avenues to fabricate structural materials from the design of sub-nanoscale building blocks. The critical size limit for general structural material design is challenged in the dimers of sub-nm molecular clusters that possess small sizes (<5 nm) and broadly tunable viscoelasticity.
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影响因子：
41.2
作者：
Mueggenburg, Klara E.;Lin, Xiao-Min;Jaeger, Heinrich M.
通讯作者：
Jaeger, Heinrich M.
影响因子：
56.9
作者：
Klajn, Rafal;Bishop, Kyle J. M.;Grzybowski, Bartosz A.
通讯作者：
Grzybowski, Bartosz A.
影响因子：
56.9
作者：
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通讯作者：
Russell, Thomas P.
影响因子：
5.5
作者：
ANTONIETTI, M;PAKULA, T;BREMSER, W
通讯作者：
BREMSER, W
影响因子：
8.6
作者：
Bishko, G;McLeish, TCB;Larson, RG
通讯作者：
Larson, RG