Some natural bers like ax, hemp and others show excellent mechanical properties that make them a promising choice for the reinforcement of polymers. The increasing research on natural ber reinforced composites has still left important questions open, mainly concerning the ber-matrix interface. Compared to the well optimized glass bers, cellulose bers show very different interaction with matrix polymers and adhesion promoters. The hydrophilic cellulose structure allows for the penetration of a considerable amount of water into the amorphous regions of the bers, eventually exceeding 20% by mass, depending on ber type, preparation and environmental humidity. Even embedded in totally apolar polymers the cellulose partly retains its ability for water sorption, which results in unfavorable effects, such as dimensional changes, decrease in strength, roughening of the surface, etc.The interaction of differently prepared bers with water vapor and the effect of surface treatment is investigated by measuring the dynamics of water vapor sorption. An exponential model is used for the numerical evaluation of the sorption and desorption kinetics. The model not only allows for an excellent t of the experimental isotherms, but without any further assumptions it immediately gives evidence of the existence of two distinct mechanisms for the exchange of water vapor, related to different sorption sites. These speci c mechanisms are represented by individual sorption-desorption isotherms as components of the total isotherms. The model provides a clearer differentiation of the effects of ber preparation and modi cation with respect to interfacial interactions.

Oligomerization of lipidated peptides is of general scientific interest and is important in biomedical and pharmaceutical applications. We investigated the solution properties of a lipidated peptide, Liraglutide, which is one of the glucagon-like peptide-1 (GLP-1) agonists used for the treatment of type II diabetes. Liraglutide can serve as a model system for studying biophysical and biochemical properties of micelle-like self-assemblies of the lipidated peptides. Here, we report a transformation induced in Liraglutide oligomers by changing pH in the vicinity of pH 7. This fully reversible transformation is characterized by changes in the size and aggregation number of the oligomer and an associated change in the secondary structure of the constituent peptides. This transformation has quite slow kinetics: the equilibrium is reached in a course of several days. Interestingly, while the transformation is induced by changing pH, its kinetics is essentially independent of the final pH. We interpreted these findings using a model in which desorption of the monomer from the oligomer is the rate-limiting step in the transformation, and we determined the rate constant of the monomer desorption.

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Pseudoephedrine HCl, a highly water-soluble drug, was entrapped within poly (methyl methacrylate) microspheres by a water/oil/water emulsification-solvent evaporation method. An aqueous drug solution was emulsified into a solution of the polymer in methylene chloride, followed by emulsification of this primary emulsion into an external aqueous phase to form a water/oil/water emulsion. The middle organic phase separated the internal drug-containing aqueous phase from the continuous phase. Microspheres were formed after solvent evaporation and polymer precipitation. The drug content of the microspheres increased with increasing theoretical drug loading, increasing amounts of organic solvent, polymer and polymeric stabilizer, and decreased with increasing stirring time, increasing pH of the continuous phase and increased volume of the internal and external aqueous phase.

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