Henry's law coefficients and partial molar volumes of 34 penetrants (5 inert gases, 6 inorganic gases, 17 hydrocarbon gases, 5 fluorinated gases, and CCl4 vapor) dissolved in poly(dimethylsiloxane) and low-density polyethylene were determined at 25 °C by measuring sorption of the gases and the concomitant dilation of the polymers. From the Henry's law coefficients and the partial molar volumes, Flory−Huggins parameters for polymer/gas interactions were estimated. The partial molar volumes were correlated with critical molar volumes of gases, and the interaction parameters were found to depend on the partial molar volumes. These relationships for the fluorinated gases were clearly different from those of all other gases. For CO2 and CH4 in poly(dimethylsiloxane), partial molar volumes and interaction parameters were obtained as a function of temperature over a range −30 to 95 °C. Thermal expansivities of these dissolved molecules were estimated to be 2 × 10-3 °C-1 from the temperature dependence of partial molar volumes.

Sorption of CO2 in poly(methyl methacrylate) at 35−200 °C and concurrent dilation of the polymer at 35−85 °C over a pressure range up to 50 atm were studied. Dissolution and Flory−Huggins interaction parameters for the gas in the polymer, not only in the rubbery state but also in the glassy state, were estimated by analyzing the sorption data above the glass transition temperature (T g0, 105 °C). Isothermal glass transition of the polymer/gas system was observed on isotherms of sorption and dilation below T g0. Partial molar volumes of sorbed CO2 determined from the sorption and dilation isotherms increased with increasing concentration to the glass transition concentration. These isotherms were also analyzed on the basis of extended dual-mode models of sorption and dilation. From obtained parameters of the dual-mode models, nonequilibrium properties such as mean size and number of microvoids for the pure polymer and the CO2-sorbed polymer in the glassy state were evaluated. The mean size, dependent upon CO2 exposure history of the polymer, was in the range of 20−100 A3, and the number of microvoid ((1−18) × 1020 voids/cm3) was dependent upon both temperature and the exposure history.

Since the discovery of mesoporous silica, [1][2][3] new organicinorganic nanocomposites based on mesoporous silica materials have been extensively investigated in the development of functional materials in various fields.[4] The grafting of organic groups onto the pore walls of the silica [5] has provided novel materials for catalysis, [6] heavy-metal ion adsorption, [7] photocontrollable molecular storage, [8] gas separation, [9] and molecular recognition. [10][11][12] Since the chemical functionalities of these materials have been ascribed mainly to the organic moiety, a promising strategy toward new functions is to design an inorganic-organic cooperative mechanism in nanostructured materials. [11,12] Solid acid catalysts have served as important functional materials in about 180 industrial processes in the petroleum refinery industry and in the production of chemicals.[13] In contrast, a significant number of acid-catalyzed reactions, such as Friedel-Crafts reactions, esterification, and hydrations, are still carried out by using conventional acids, such as H 2 SO 4 and AlCl 3 . In particular, for the reactions in which water participates as a reactant or product, such as hydrolysis, hydration, and esterification, only a few solid acids show acceptable performances. [14][15][16] The development of new water-tolerant solid acids is expected to have a major impact in industrial applications as well as in scientific aspects. One of the major difficulties concerned with the use of solid acids is the severe deactivation of the acid sites by water, and in fact, most solid acids lose their catalytic activity in aqueous solutions.We have overcome this difficulty by designing acid catalysts comprising polyoxometalate (hetero-polyacid) molecules and organografted mesoporous silica. We found that the acidic protons in the hydrophobic environment of organomodified mesoporous silica show extremely high catalytic activity for ester hydrolysis in water. Figure 1 illustrates the concept of the nanostructured catalyst. Two kinds of organic groups, n-octyl and 3-aminopropyl, were grafted onto the pore walls of mesoporous silica SBA-15. [3] The aminopropyl groups immobilize the H 3 PW 12 O 40 polyoxometalate anions on the pore walls, while the octyl groups (ca. 1 nm in length) form hydrophobic regions around the polyanions. It was found that water and reactant molecules can penetrate into the nanospaces through the remaining spaces at the centers of the SBA-15 pores. In the preparation of the catalyst, first alkyl groups and then 3-aminopropyl groups (AP groups) were grafted on SBA-15 (pore diameter 7.5 nm, BET surface area 458 m 2 g À1 ) to obtain organomodified materials, denoted by C n -AP-SBA, where n is the number of carbon atoms of the alkyl group. After neutralization of the amino groups with hydrochloric acid, Figure 1. Schematic illustration outlining the preparation and structure of the catalysts. Octyl and 3-aminopropyl groups were subsequently grafted on the pore walls of mesoporous silica SBA-15, followed by immobil...

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Sorption and dilation in the system poly(ethyl methacrylate) (PEMA) and carbon dioxide are reported for pressures up to 50 atm over the temperature range 15–85°C. The sorption isotherms were obtained gravimetrically. The dilation accompanying sorption was measured directly with a cathetometer. At low temperatures the sorption and dilation isotherms were concave toward the pressure axis in the low‐pressure region and turned to convex with increasing pressure. As the experimental temperature approached and exceeded the glass transition temperature of 61°C, both isotherms became convex or linear over the whole range of pressure. Partial molar volumes of CO2 in PEMA were obtained from sorption and dilation data, which were described well by the extended dual‐mode sorption and dilation models developed recently. The temperature dependence of the dual‐mode parameters and the isothermal glass transition are discussed.