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The size and shape of free volume (FV) holes available in membrane materials control the rate of gas diffusion and its permeability. Based on this principle, a segmented, thermo-sensitive polyurethane (TSPU) membrane with functional gate, i.e., the ability to sense and respond to external thermo-stimuli, was synthesized. This smart membrane exhibited close-open characteristics to the size of the FV hole and water vapor permeation and thus can be used as smart food packaging materials. Differential scanning calorimetry (DSC), dynamic mechanical analysis (DMA), positron annihilation lifetimes (PAL) and water vapor permeability (WVP) were used to evaluate how the morphological structure of TSPU and the temperature influence the FV holes size. In DSC and DMA studies, TSPU with a crystalline transition reversible phase showed an obvious phase-separated structure and a phase transition temperature at 53 o C (defined as the switch temperature and used as a functional gate). Moreover, the switch temperature (T s ) and the thermal-sensitivity of TSPU remained available after two or three thermal cyclic processes. The PAL study indicated that the FV hole size of TSPU is closely related to the T ·d, which produced an "increase-decrease" response to the thermo-stimuli. This phase transition accompanying significant changes in the FV hole size and WVP can be used to develop "smart materials" with functional gates and controllable water vapor permeation, which support the possible applications of TSPU for food packaging.

In the title compound, poly[[aqua(1,10-phenanthroline)cobalt(II)]-mu4-dihydrogen benzene-1,2,4,5-tetracarboxylato], [Co(C10H4O8)(C12H8N2)(H2O)]n, each cobalt(II) cation has an octahedral geometry completed by one aqua O atom, three carboxy O atoms belonging to three H2TCB2- anions (H2TCB2- is dihydrogen benzene-1,2,4,5-tetracarboxylate) and two N atoms from a 1,10-phenanthroline molecule. In the asymmetric unit, there are two half H2TCB2- anions lying about independent inversion centres. The bridging H2TCB2- anions have two coordination modes, viz. mu2-H2TCB2- and mu4-H2TCB2-, resulting in a two-dimensional coordination polymer. Furthermore, a three-dimensional network is formed by O(carboxy)...O(carboxy) hydrogen-bond interactions, with H...A distances in the range 1.69-1.82 A, and O(carboxy)...O(water) interactions, with H...A distances in the range 1.91-1.94 A.

A novel method was used to synthesis nanosilica/waterborne polyurethane (WPU) hybrids by in situ hydrolysis and condensation of tetraethyl orthosilicate (TEOS) and/or 3-aminopropyltriethoxylsilane bonding at the end of the WPU molecular chain. The hybrid was characterized by scanning electron microscopy, energy dispersive spectroscopy (EDS), transmission electron microscopy, Fourier transform infrared spectroscopy (FTIR), and X-ray photoelectron spectroscopy (XPS). The results showed that the nanosilica/WPU hybrids with well-dispersed nanosilica particles were synthesized, in which the particles had typical diameters of about 50 nm. In addition, XPS and FTIR analyses demonstrated that chemical interaction occurred between WPU and silica. The effects of TEOS on surface wettability, water resistance, mechanical strength, and thermal properties of the hybrid were also evaluated by contact angle measurements, water absorption tests, mechanical tests, and differential scanning calorimetry, respectively. An increase in advancing contact angles, water resistance, and tensile strength, as well as decrease in elongation at break and glass transition temperature, were obtained with the addition of TEOS. Water absorption decreased from 17.3 to 5.5%. The tensile strength increased to a maximum of 29.7 MPa, an increase of about 34%. Elongations at break of the hybrids decreased 191%. These results were attributed to the effects of the nanosilica and the chemical interaction between WPU and silica.

A new dipeptide compound, (R)-2,4-dioxo-5-fluoro-1- [1-(methoxycarbonyl)