We describe the preparation of porous polymeric scaffolds via polymerization of the oil phase in high internal phase water-in-oil-emulsions using amphiphilic block copolymers polystyrene-b-poly(ethylene oxide), polystyrene-b-poly(acrylic acid), poly(1,4-butadiene)-b-poly(ethylene oxide), and poly(1,4-butadiene)-b-poly(acrylic acid) as surfactants. We show that the block copolymers anchor to the polymerized oil phase via the lipophilic block, which can occur by chemical and/or physical entanglement and consequent presentation of the hydrophilic block on the pore surfaces. The in situ polymerization enables the full surface functionalization of the porous materials with the final surface chemistry dictated by the hydrophilic block. Furthermore, the foam physical architecture may be tailored through controlling emulsion parameters such as the initiator, shear rate, and aqueous phase volume fraction.

Friction force microscopy measurements have been carried out on free-standing films of poly(ethylene terephthalate) in a variety of different media. In ethanol, the adhesion force was small, and the friction-load relationship was linear. In perfluorodecalin, nonlinearity was observed in the friction-load relationship, and the data have been found to fit the Johnson-Kendall-Roberts model of contact mechanics. The behavior in hexadecane was also characterized by a single-asperity contact model, but in this case, the data were found to fit the Derjaguin-Müller-Toporov model. It is suggested that these differences are due to the different strengths of tip-sample adhesion, which arise from the differences in the dielectric constants of the media: in ethanol, which has a high dielectric constant, the friction force varies linearly with the load, whereas in media of low dielectric constant, adhesion-limited behavior is observed.

Studies of the UV-induced photodegradation of poly(ethylene terephthalate) (PET) have been carried out using contact-angle goniometry, X-ray photoelectron spectroscopy (XPS), and friction force microscopy (FFM). The advancing contact angle of water, theta, decreased following exposure of free-standing PET films to UV light. Measurements of surface friction by FFM showed that the coefficient of friction mu increased as the degradation proceeded, reaching a limiting value after ca 200 min, in agreement with the contact angle data. Using a modified form of the Cassie equation, a quantitative analysis of the extent of modification could be carried out. There was a very close correlation between the coefficient of friction determined by FFM and the value of cos theta. XPS provided more detailed information on surface bonding that also correlated closely with the FFM data. Although FFM provides quantitative data on surface modification with nanometer-scale spatial resolution, it does not provide detailed structural information such as is provided by XPS. The oxygen content at the surface was found to increase as photo-generated radicals within the PET reacted with atmospheric oxygen. Increases in both ester and carbonyl contributions within XPS data accompanied this increase. It was concluded that the photodegradation process follows mainly Norrish type I reaction pathways, following previous work by Fechine et al and Grosstete et al.

BackgroundThe surface properties of probiotic bacteria influence to a large extent their interactions within the gut ecosystem. There is limited amount of information on the effect of the production process on the surface properties of probiotic lactobacilli in relation to the mechanisms of their adhesion to the gastrointestinal mucosa. The aim of this work was to investigate the effect of the fermentation pH and temperature on the surface properties and adhesion ability to Caco-2 cells of the probiotic strain Lactobacillus rhamnosus GG.ResultsThe cells were grown at pH 5, 5.5, 6 (temperature 37°C) and at pH 6.5 (temperature 25°C, 30°C and 37°C), and their surfaces analysed by X-ray photoelectron spectrometry (XPS), Fourier transform infrared spectroscopy (FT-IR) and gel-based proteomics. The results indicated that for all the fermentation conditions, with the exception of pH 5, a higher nitrogen to carbon ratio and a lower phosphate content was observed at the surface of the bacteria, which resulted in a lower surface hydrophobicity and reduced adhesion levels to Caco-2 cells as compared to the control fermentation (pH 6.5, 37°C). A number of adhesive proteins, which have been suggested in previous published works to take part in the adhesion of bacteria to the human gastrointestinal tract, were identified by proteomic analysis, with no significant differences between samples however.ConclusionsThe temperature and the pH of the fermentation influenced the surface composition, hydrophobicity and the levels of adhesion of L. rhamnosus GG to Caco-2 cells. It was deduced from the data that a protein rich surface reduced the adhesion ability of the cells.

Binary polymer brush patterns were fabricated using aminosilanes with photo-cleavable protecting groups.