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Polyhedral oligomeric silsesquioxane (POSS) surfactants

机译：多面体低聚倍半硅氧烷（POSS）表面活性剂

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There has been recent interest in using polyhedral oligomeric silsesquioxanes. (POSS) as the smallest particles of silica for reinforcement of polymers. These materials are monodisperse, have tailored functionality (including a hydrophobic coating), and should thus act as model nanoparticulate filler. Feher et. al. have shown that sol-gel condensation into cage compounds can yield two thermodynamically stable main isolates: a fully condensed R_8T_8 cube (Figure la) and an incompletely condensed R_7T_4D_3(OH)_3 trisilanol (Figure lb). (T refers to a SiO_(3/2) and D is a SiO_(2/2) moiety in a silicate framework) There are large differences in the solubility of POSS in common organic solvents based on the substitution of the cages. For example, a fully condensed iBu_8T_8 cube (Figure la) is more soluble than a similar cyclohexyl Cy_8T_8 cube which in turn is more soluble than a cyclopentyl Cp_8T_8 substituted cube. Furthermore, the breaking of symmetry in the incompletely condensed cubes (Figure lb) could also be expected to enhance solubility/compatibility. The dispersion of POSS will likely determine how well the material can act as a "nanofiller." Farmer et. al. have recently performed molecular dynamics simulations which suggest that POSS molecules have no tendency for aggregation in a polymeric matrix if they are originally well dispersed.
机译：最近对使用多面体低聚倍半硅氧烷有兴趣。 （POSS）作为用于增强聚合物的二氧化硅的最小颗粒。这些材料是单分散的，具有定制的功能（包括疏水涂层），因此应充当模型纳米颗粒填料。 Feher等。等已经表明，溶胶-凝胶缩合为笼状化合物可以产生两个热力学稳定的主要分离物：完全缩合的R_8T_8立方体（图1a）和不完全缩合的R_7T_4D_3（OH）_3三硅烷醇（图1b）。 （T是指在硅酸盐骨架中的SiO_（3/2），D是SiO_（2/2）部分）基于笼的取代，POSS在常见有机溶剂中的溶解度存在很大差异。例如，完全缩合的iBu_8T_8立方体（图1a）比类似的环己基Cy_8T_8立方体更易溶，而环己基Cy_8T_8立方体又比环戊基Cp_8T_8取代的立方体更易溶。此外，还可以预期，在不完全冷凝的立方体中破坏对称性（图1b）会提高溶解度/相容性。 POSS的分散性可能会决定该材料作为“纳米填料”的性能。农夫等等最近，我们进行了分子动力学模拟，这表明，如果POSS分子本来分散良好，就不会在聚合物基质中聚集。

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