Voronin E F, Gun'ko V M, Guzenko N V, Pakhlov E M, Nosach L V, Leboda R, Skubiszewska-Zieba J, Malysheva M L, Borysenko M V, Chuiko A A
Institute of Surface Chemistry, 17 General Naumov Street, 03164 Kiev, Ukraine.
J Colloid Interface Sci. 2004 Nov 15;279(2):326-40. doi: 10.1016/j.jcis.2004.06.073.
Interaction of poly(ethylene oxide) (PEO, 600 kDa) with fumed silica A-300 (SBET = 316 m2/g) was investigated under different conditions using adsorption, infrared (IR), thermal analysis (TG-DTA), AFM, and quantum chemical methods. The studied dried silica/PEO samples were also carbonized in a flow reactor at 773 K. The structural characteristics of fumed silica, PEO/silica, and pyrocarbon/fumed silica were investigated using nitrogen adsorption-desorption at 77.4 K. PEO adsorption isotherm depicts a high affinity of PEO to the fumed silica surface in aqueous medium. PEO adsorbed in the amount of 50 mg per gram of silica (PEO monolayer corresponds to CPEO approximately 190 mg/g) can disturb approximately 70% of isolated surface silanols. However, at the monolayer coverage, only 20% of oxygen atoms of PEO molecules take part in the hydrogen bonding with the surface silanols. An increase in the PEO amount adsorbed on fumed silica leads to a diminution of the specific surface area and contributions of micro- (pore radius R < 1 nm) and mesopores (1 < R < 25 nm) to the pore volume but contribution of macropores (R > 25 nm) increases with CPEO. Quantum chemical calculations of a complex of a PEO fragment with a tripple bond SiOH group of a silica cluster in the gas phase and with consideration for the solvent (water) effect show a reduction of interaction energy in the aqueous medium. However, the complex remains strong enough to provide durability of the PEO adsorption complexes on fumed silica; i.e., PEO/fumed silica nanocomposites could be stable in both gaseous and liquid media.
采用吸附、红外（IR）、热分析（TG-DTA）、原子力显微镜（AFM）和量子化学方法，在不同条件下研究了聚环氧乙烷（PEO，600 kDa）与气相二氧化硅A-300（SBET = 316 m2/g）的相互作用。所研究的干燥二氧化硅/PEO样品也在流动反应器中于773 K下碳化。使用77.4 K下的氮气吸附-脱附研究了气相二氧化硅、PEO/二氧化硅和热解碳/气相二氧化硅的结构特征。PEO吸附等温线表明在水介质中PEO对气相二氧化硅表面具有高亲和力。每克二氧化硅吸附50 mg的PEO（PEO单层对应CPEO约190 mg/g）可干扰约70%的孤立表面硅醇。然而，在单层覆盖时，只有20%的PEO分子氧原子参与与表面硅醇的氢键形成。气相二氧化硅上吸附的PEO量增加会导致比表面积减小，微孔（孔径半径R < 1 nm）和中孔（1 < R < 25 nm）对孔体积的贡献减小，但大孔（R > 25 nm）的贡献随CPEO增加。对气相中PEO片段与二氧化硅簇的三键SiOH基团形成的配合物进行量子化学计算，并考虑溶剂（水）效应，结果表明在水介质中相互作用能降低。然而，该配合物仍足够强，以确保PEO在气相二氧化硅上吸附配合物的耐久性；即，PEO/气相二氧化硅纳米复合材料在气态和液态介质中都可能是稳定的。
