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Silica–polyimide hybrid composites were prepared via a sol–gel process and thermal imidization. Two different types of soluble precursors, poly(amic acid) (PAA) and poly(amic diethyl ester) (ES), chemically convertible to poly(p‐phenylene biphenyltetracarboximide), were used as organic polymer matrix component, and tetraethoxysilane (TEOS), convertible to silica, as the inorganic component. The structure of composites prepared as thin films was investigated by means of small‐angle X‐ray scattering, scanning electron microscopy and atomic force microscopy. Nanometre‐scale composites were successfully obtained for ≤30wt% TEOS‐loaded mixtures with ES and PAA. It was considered from the microstructural investigation that the composite films based on ES were not significantly affected by the inorganic particles generated, maintaining the structure of the homopolyimide, while those based on PAA did not preserve the structure due to the nanoparticles grown in situ during the sol–gel process. © 1997 SCI.

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Synbiotics, a combination of prebiotics and probiotics, produce synergistic effects to promote gastrointestinal health. Herein, we investigated the synbiotic interaction between the Lactobacillus rhamnosus strain GG (LGG; a probiotic strain) and tagatose (a prebiotic) in a dextran sulfate sodium (DSS)-induced colitis murine model. Initially, body weight, food intake, and clinical features were dramatically decreased after treatment with DSS, and the addition of LGG, tagatose, or both ameliorated these effects. In our pyrosequencing analysis of fecal microbiota, DSS treatment increased the abundance of Proteobacteria and decreased that of Firmicutes. When LGG and tagatose were administered as synbiotics, the gut microbiota composition recovered from the dysbiosis caused by DSS treatment. In particular, the abundance of Bacteroides, Lactobacillus, and Akkermansia was significantly associated with probiotic, prebiotic, and synbiotic treatments. Taken together, our results suggest that LGG and tagatose as synbiotics can alleviate colitis, and synbiotics could be applied as dietary supplements in dairy foods such as yogurt and cheese.

Homogeneous precursor/precursor solutions with various compositions were obtained with appreciably high solid contents in N‐methyl‐2‐pyrrolidone from soluble poly(amic diethyl ester) precursors of rodlike poly(p‐phenylene biphenyltetracarboximide) (BPDA‐PDA) and flexible poly(4,4′‐oxydiphenylene biphenyltetracarboximide) (BPDA‐ODA), which are hydrolytically more stable as well as more soluble than the corresponding poly(amic acid)s being equilibrated with the constituent monomers. Both optical microscopic and light scattering measurements showed that the dried precursor blend films and resultant polyimide composite films were optically transparent, regardless of compositions and process conditions. The composite films showed a single Tg behavior. However, for the composite of 30 wt % BPDA‐PDA dispersed in the matrix of 70 wt % BPDA‐ODA, a smectic crystalline‐like aggregation of the BPDA‐PDA component was detected on wide‐angle x‐ray diffraction patterns, indicative of microscopic phase separation between the two components. This phase separation was not detected on the optical microscopy, light scattering, and dynamic mechanical thermal analysis because of their resolution limits: Optical microscopy has a resolution of submicrometers, whereas dynamic mechanical thermal analysis and light scattering have a resolution of ca. 50 Å. Therefore, it is speculated that in the composite films BPDA‐PDA and BPDA‐ODA polyimide molecules have demixed on the scale of a few nanometers. The mean long periodicity, which was estimated from the small‐angle x‐ray scattering pattern, varied from 134 to 170 Å as the content of BPDA‐ODA component increased. In addition, mechanical properties of the composite films were characterized. ©1995 John Wiley & Sons, Inc.