Novel branched nanostructures based on polyhedral oligomeric silsesquioxanes and azobenzene dyes containing different spacers and isolation groups†,Journal of Materials Chemistry C

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Novel branched nanostructures based on polyhedral oligomeric silsesquioxanes and azobenzene dyes containing different spacers and isolation groups†
Journal of Materials Chemistry C ( IF 5.7 ) Pub Date : 2018-03-15 00:00:00 , DOI: 10.1039/c8tc00223a
Ihor M. Tkachenko _{1,

2,

3,

4} , Yaroslav L. Kobzar _{1,

2,

3,

4} , Volodymyr F. Korolovych _{5,

6,

7,

8} , Alexandr V. Stryutsky _{1,

2,

3,

4} , Liubov K. Matkovska _{1,

2,

3,

4} , Valery V. Shevchenko _{1,

2,

3,

4} , Vladimir V. Tsukruk _{5,

6,

7,

8}

Affiliation

The great interest in smart light-responsive materials has led to the development of hybrid star-shaped nanostructures combining organic azobenzene dyes with polyhedral oligomeric silsesquioxanes (Azo-POSSs). Herein we present two approaches to fabricating azo-functionalized POSS compounds with the desired characteristics: (1) the synthesis of branched Azo-POSS structures based on azo dyes possessing flexible spacers of different chemical natures and lengths between the inorganic POSS core and the azobenzene branches, and (2) an approach that was first applied to Azo-POSS systems – the synthesis of Azo-POSS conjugates with isolation groups (they minimize undesired chromophore–chromophore interactions) in the azobenzene fragments and the constant short spacer between the azo dyes and the medium. The first one was synthesized from azo dyes containing hexenyloxy-, allyloxy-ethoxypropoxy- and tetramethyl-disiloxanyl-propoxy substituents, while the second one was prepared from allyl-functionalized azo-based chromophores with changeable isolation groups (hydroxymethylene-, trimethylsiloxymethylene- and pentafluorophenoxymethylene-groups). According to DSC analysis the Azo-POSS based on the hexenyloxy-substituted dye has crystalline domains whereas all other Azo-POSS compounds are amorphous. We found that robust and ultrathin films with a thicknesses of around 60 nm and low refractive indices (ca. 1.46) can be fabricated from all Azo-POSS branched conjugates. It was demonstrated that the surface roughness of the Azo-POSS films can be significantly minimized by the attachment of azo dyes having side isolation groups into the POSS core. Moreover, for Azo-POSS molecules with isolation groups in the azobenzene units, we observed a significant decrease in the trans–cis photoisomerization rate in solution compared to other obtained star-shaped Azo-POSS systems. At the same time, the photoisomerization rates of the synthesized Azo-POSS conjugates in films are almost the same. These results indicate that the presence of the isolation groups effectively prevents inter- and intramolecular aggregation of azobenzene chromophores attached to the POSS core in the solid state.

中文翻译：

基于多面体低聚倍半硅氧烷和偶氮苯染料的新型支化纳米结构，其中包含不同的间隔基和隔离基团†

对智能光响应材料的极大兴趣导致了将有机偶氮苯染料与多面体低聚倍半硅氧烷（Azo-POSS）相结合的混合星形纳米结构的开发。本文中，我们提出了两种具有所需特性的偶氮官能化POSS化合物的制备方法：（1）基于偶氮染料的支链偶氮-POSS结构的合成，该偶氮染料在无机POSS核和偶氮苯支链之间具有不同化学性质和长度的柔性间隔基，和（2），其首先被施加到一种方法偶氮POSS系统-的合成偶氮POSS偶氮苯片段中带有隔离基团（它们使不希望的生色团-生色团之间的相互作用最小化）的偶联物，以及偶氮染料和介质之间恒定的短间隔基。第一个是由含有己烯氧基，烯丙氧基-乙氧基丙氧基和四甲基-二硅氧烷基-丙氧基取代基的偶氮染料合成的，而第二个是由烯丙基官能化的偶氮基生色团制备的，该生色团具有可变的分离基团（羟基亚甲基，三甲基甲硅烷氧基亚甲基和五氟苯氧基亚甲基）组）。根据DSC分析，基于己烯氧基取代的染料的Azo-POSS具有晶体结构域，而所有其他Azo-POSS化合物是无定形的。我们发现，可以由所有Azo-POSS支链共轭物制造厚度约为60 nm且低折射率（约1.46）的坚固且超薄的薄膜。已经证明，通过将具有侧隔离基团的偶氮染料附着到POSS核中，可以显着最小化Azo-POSS膜的表面粗糙度。此外，对于偶氮苯单元中具有隔离基团的Azo-POSS分子，与其他获得的星形Azo-POSS相比，我们观察到溶液中反式-顺式光异构化速率显着降低系统。同时，膜中合成的偶氮-POSS共轭物的光异构化速率几乎相同。这些结果表明，隔离基团的存在有效地防止了固态时附着在POSS核上的偶氮苯生色团的分子间和分子内聚集。

更新日期：2018-03-15

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