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PNIPAM hydrogels functionalized with gold nanoparticles were prepared by making use of catechol redox chemistry. For this purpose catechol groups were introduced in the PNIPAM network during the cross-linking polymerization process (PNIPAM–catecholx hydrogel). These groups act as reducing agents of HAuCl4, which enables the functionalization of the PNIPAM with gold nanoparticles (PNIPAM–catecholx@Au hydrogel). The rheological study shows that catechol groups reinforce the hydrogel structure. A stronger effect was observed after the functionalization of the hydrogel with gold nanoparticles. This influence could be easily observed since the variation of G′ with the MBA mole fraction was fitted to a power-law expression G′ ∼ x MBA a , with a = 1.6 for PNIPAMx hydrogels, a = 2.3 for PNIMPAM–catecholx hydrogels and a = 3.2 for PNIMPAM–catecholx@Au hydrogels. The capability of the PNIPAM–catecholx@Au hydrogel to act as a tunable catalyst was demonstrated with a model reduction reaction. The half-lifetime at 25 °C was 10.5 min; however, at 38 °C the half-lifetime was 133 min.

This work describes the preparation of mixed matrix membranes by casting from poly(1,4-phenylene ether−ether−sulfone) chloroform solutions containing dispersed zeolitic imidazolate frameworks. Diffusive studies of CO2 in the pristine poly(1,4-phenylene ether−ether−sulfone) membrane and composite membranes were performed at 6 bar and 298 K, using pulsed field gradient NMR techniques. The evolution of the heterogeneity of the diffusion environments as seen by NMR was monitored in terms of the diffusion time and a stretching parameter. The values of the self-diffusion coefficient increase with filler content, from 2.1 × 10−8 cm2 s−1 for pristine membranes to 9.3 × 10−8 cm2 s−1 for membranes with 30 wt % of filler. Sorption and permeation experiments carried out at different pressures were used to determine the dual-mode model parameters that describe the transport processes. Apparent diffusion coefficients of CO2 in the membranes were obtained from the time lag method, from parameters of the dual-mode model, and directly from the derivatives of the steady flux, expressed in terms of concentration and pressure, with respect to pressure. In general, the values of the apparent diffusion coefficients obtained by the three methods for pristine membranes are in rather good agreement with the self-diffusion coefficient obtained by the NMR technique. In composite membranes, the values of the self-diffusion coefficients are nearly 2 times those obtained using permeation and sorption experiments. The discrepancies between the values of the self-diffusion coefficients and the results obtained for the diffusion coefficient by other techniques are discussed. The filler contributes greatly to gas permeation by increasing the gas solubility in the composite membranes.

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The synthesis and polymerization of the new monomers N-(1-adamantyl)-exo-norbornene-5,6-dicarboximide (AdNDI), N-cyclohexyl-exo-norbornene-5,6-dicarboximide (ChNDI), and N-phenyl-exo-norbornene-5,6-dicarboximide (PhNDI) are reported. Copolymers of N-(1-adamantyl)-exo-norbornene-5,6-dicarboximide/norbornene, with molar compositions 50/50, 70/30, and 30/70, were also obtained. The transport of hydrogen, oxygen, nitrogen, carbon monoxide, carbon dioxide, methane, ethylene, and ethane across membranes prepared from these homopolymers and copolymers was determined at 30 °C using permeation techniques. Diffusion coefficients correlate rather well with the diameter of diffusant molecules except in the case of carbon dioxide. The values of the permselectivity coefficient for different gases depend on the type of membranes. For example, the permselectivity of oxygen with respect to nitrogen, α(O2/N2), is ca. 5.50 for membranes prepared from N-(1-adamantyl)-exo-norbornene-5,6-dicarboximide/norbornene (50/50) copolymers, which compares favorably with the values reported for this parameter in membranes with imide groups located in the backbone. The values of α(H2/C2H6) in membranes of poly(N-(1-adamantyl-exo-norbornene-5,6-dicarboximide), poly(N-cyclohexyl-exo-norbornene-5,6-dicarboximide), and poly(N-phenyl-exo-norbornene-5,6-dicarboximide) are 183, 124, and 122, respectively, whereas the values of α(C2H4/C2H6) amount to 6.9, 7.6, and 6.4, respectively. For most membranes used in this study, diffusion rather than solubility is responsible for the discrimination of gas transport. However, solubility is mainly responsible for the high permselectivity of ethylene with respect to ethane displayed by the membranes.