Interaction of poly(ethylene oxide) with fumed silica

• Published in: Journal of colloid and interface science 2004-11, Vol.279 (2), p.326-340
• Main Authors: Voronin, E.F., Gun'ko, V.M., Guzenko, N.V., Pakhlov, E.M., Nosach, L.V., Leboda, R., Skubiszewska-Zięba, J., Malysheva, M.L., Borysenko, M.V., Chuiko, A.A.
• Format: Article
• Language: English
• Subjects: Ab initio quantum chemical calculations; Adsorption; AFM; Chemistry; Colloidal state and disperse state; ENVIRONMENTAL MOLECULAR SCIENCES LABORATORY; Exact sciences and technology; Fumed silica; General and physical chemistry; Infrared spectroscopy; INORGANIC, ORGANIC, PHYSICAL AND ANALYTICAL CHEMISTRY; INTERACTIONS; Models, Molecular; Nitrogen adsorption; PEO carbonization; Poly(ethylene oxide) adsorption; POLYETHYLENE GLYCOLS; Polyethylene Glycols - chemistry; Pore-size distribution; Porous materials; SILICA; Silicon Dioxide - chemistry; Surface physical chemistry; Surface Properties; Temperature; TG-DTA
• ISSN: 0021-9797; 1095-7103
• DOI: 10.1016/j.jcis.2004.06.073

Interaction of poly(ethylene oxide) (PEO, 600 kDa) with fumed silica A-300 ( S BET = 316   m 2 / 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 C PEO ≈ 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 C PEO . Quantum chemical calculations of a complex of a PEO fragment with a 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.