Combining branched copolymers with additives generates stable thermoresponsive emulsions with in situ gelation upon exposure to body temperature

Branched copolymer surfactants (BCS) containing thermoresponsive polymer components, hydrophilic components, and hydrophobic termini allow the formation of emulsions which switch from liquid at room temperature to a gel state upon heating. These materials have great potential as in situ gel-forming dosage forms for administration to external and internal body sites, where the emulsion system also allows effective solubilisation of a range of drugs with different chemistries. These systems have been reported previously, however there are many challenges to translation into pharmaceutical excipients. To transition towards this application, this manuscript describes the evaluation of a range of pharmaceutically-relevant oils in the BCS system as well as evaluation of surfactants and polymeric/oligomeric additives to enhance stability. Key endpoints for this study are macroscopic stability of the emulsions and rheological response to temperature. The effect of an optimal additive (methylcellulose) on the nanoscale processes occurring in the BCS-stabilised emulsions is probed by small-angle neutron scattering (SANS) to better comprehend the system. Overall, the study reports an optimal BCS/methylcellulose system exhibiting sol–gel transition at a physiologically-relevant temperature without macroscopic evidence of instability as an in situ gelling dosage form

Crystal Chemistry of Cobalamins. Structural Characterization of the Co-S Bond in Cobalamins.

INORG. CHEM

Evolution of Structure in a Comb Copolymer-Surfactant Coacervate

The interaction between a double-hydrophilic comb copolymer with the polyanionic backbone poly[methacrylic acid-stat-poly(ethylene glycol) methyl ether methacrylate] (PMAA-PEGMA) and the cationic surfactant N-dodecylpyridinium chloride (DPCl) was studied in alkaline aqueous solutions by using a combination of light and X-ray scattering techniques, covering 5 orders of magnitude in space (the q vector range from 10-5 to 5 nm-1) and time (from milliseconds to several hours). The results showed that the polyelectrolyte-surfactant (PE-S) complex of PMAA-PEGMA and DPCl forms micrometer-sized coacervate particles containing collapsed PMAA-PEGMA chains with attached and densely packed DPCl micelles. Time-resolved SAXS measurements coupled with a stopped-flow apparatus revealed that the phase separation of the PE-S complex into a coacervate phase occurred in <25 ms after mixing the polyelectrolyte and the surfactant. Thus, microphase separation was faster than the self-assembly of DPCl into densely packed micelles. The terminal stages of polyelectrolyte-surfactant coacervation were dictated by the Ostwald ripening of the droplets in the time range of hours

Spinning, drawing and physical properties of polypropylene nanocomposite fibers with fumed nanosilica

Nanocomposite fibers of isotactic polypropylene – fumed silica AR805 were prepared by melt compounding using a two-step process: melt-spinning and hot drawing at various draw ratios up to 15. Transmission electron microscopy revealed uniform dispersion of the silica nanoparticles in polypropylene matrix, although at higher concentrations and lower draw ratios the nanoparticles showed increasing tendency to form small agglomerates. On the other hand, at low concentrations the uniform distribution of fumed silica improved mechanical properties of the composite fibers, especially at higher draw ratios. Crystallinity and melting temperature of fibers were found to significantly increase after drawing. Elastic modulus at draw ratio = 10 rose from 5.3 GPa for neat PP up to 6.2–8.1 GPa for compositions in the range 0.25–2 vol% of the filler. Moreover, higher tensile strength and creep resistance were achieved, while strain at break was rather insensitive to the filler fraction. Considering all experimental results, a failure model was proposed to explain the toughness improvement during the drawing process by the induced orientation of polymer chains and the formation of voids

Solution and solid state structure of a canted, side-to-face, bis-porphyrin adduct.

INORG. CHEM