Protsak Iryna, Pakhlov Evgeniy, Tertykh Valentyn, Le Zi-Chun, Dong Wen
College of Science, Zhejiang University of Technology, Hangzhou 310023, China.
Chuiko Institute of Surface Chemistry of National Academy of Sciences of Ukraine, 03164 Kyiv, Ukraine.
Polymers (Basel). 2018 Jan 26;10(2):116. doi: 10.3390/polym10020116.
Organosilicon layers chemically anchored on silica surfaces show high carbon content, good thermal and chemical stability and find numerous applications as fillers in polymer systems, thickeners in dispersing media, and as the stationary phases and carriers in chromatography. Methyl-terminated poly(dimethylsiloxanes) (PDMSs) are typically considered to be inert and not suitable for surface modification because of the absence of readily hydrolyzable groups. Therefore, in this paper, we report a new approach for surface modification of silica (SiO₂) nanoparticles with poly(dimethylsiloxanes) with different lengths of polymer chains (PDMS-20, PDMS-50, PDMS-100) in the presence of diethyl carbonate (DEC) as initiator of siloxane bond splitting. Infrared spectroscopy (IR), elemental analysis (CHN), transmission electron microscopy (TEM), atomic force microscopy (AFM), rotational viscosity and contact angle of wetting were employed for the characterization of the raw fumed silica and modified silica nanoparticles. Elemental analysis data revealed that the carbon content in the grafted layer is higher than 8 wt % for all modified silicas, but it decreases significantly after sample treatment in polar media for silicas which were modified using neat PDMS. The IR spectroscopy data indicated full involvement of free silanol groups in the chemisorption process at a relatively low temperature (220 °C) for all resulting samples. The contact angle studies confirmed hydrophobic surface properties of the obtained materials. The rheology results illustrated that fumed silica modified with mixtures of PDMS-x/DEC exhibited thixotropic behavior in industrial oil (I-40A), and exhibited a fully reversible nanostructure and shorter structure recovery time than nanosilicas modified with neat PDMS. The obtained results from AFM and TEM analysis revealed that the modification of fumed silica with mixtures of PDMS-20/DEC allows obtaining narrow particle size distribution with uniform dispersity and an average particle size of 15⁻17 nm. The fumed silica nanoparticles chemically modified with mixtures of PDMS-x/DEC have potential applications such as nanofillers of various polymeric systems, thickeners in dispersing media, and additives in coatings.
化学锚定在二氧化硅表面的有机硅层具有高碳含量、良好的热稳定性和化学稳定性，并在聚合物体系中作为填料、分散介质中的增稠剂以及色谱中的固定相和载体有众多应用。甲基封端的聚二甲基硅氧烷（PDMS）通常被认为是惰性的，由于缺乏易于水解的基团而不适合用于表面改性。因此，在本文中，我们报道了一种在碳酸二乙酯（DEC）作为硅氧烷键断裂引发剂的情况下，用不同聚合物链长度的聚二甲基硅氧烷（PDMS-20、PDMS-50、PDMS-100）对二氧化硅（SiO₂）纳米颗粒进行表面改性的新方法。采用红外光谱（IR）、元素分析（CHN）、透射电子显微镜（TEM）、原子力显微镜（AFM）、旋转粘度和润湿性接触角对原始气相二氧化硅和改性二氧化硅纳米颗粒进行表征。元素分析数据表明，所有改性二氧化硅接枝层中的碳含量均高于8 wt%，但对于使用纯PDMS改性的二氧化硅，在极性介质中进行样品处理后，碳含量显著降低。红外光谱数据表明，在相对较低温度（220℃）下，所有所得样品中的游离硅醇基团都完全参与了化学吸附过程。接触角研究证实了所得材料的疏水表面性质。流变学结果表明，用PDMS-x/DEC混合物改性的气相二氧化硅在工业油（I-40A）中表现出触变行为，并且与用纯PDMS改性的纳米二氧化硅相比，具有完全可逆的纳米结构和更短的结构恢复时间。AFM和TEM分析所得结果表明，用PDMS-20/DEC混合物对气相二氧化硅进行改性可获得粒径分布窄、分散均匀且平均粒径为15⁻17 nm的颗粒。用PDMS-x/DEC混合物进行化学改性的气相二氧化硅纳米颗粒具有作为各种聚合物体系的纳米填料、分散介质中的增稠剂以及涂料中的添加剂等潜在应用。
