Anthony Ryan

... is shown to modulate release of the encapsulated cargo through the generation of more permeable unilamellar vesicles, on application of mild osmotic shock. ... Consequently, the diffusion of amphiphile into water occurs via the collective diffusion of non-ergodic assemblies. ...

... At high shear rates the parallel alignment of the lamellae were reasoned to grow from a transientbimodal texture, whilst at lower shear rates larger scale relaxations caused rearrangements out of the shear plane, which resulted in perpendicular alignment of the lamellae [11]. ...

... A well-characterized series of copolyurethanes have been studied by Koberstein and co-workers.16-20 The thermal properties of these materials (ie, hard segment melting point) depend strongly on their processing temperature.17 Simultaneous FTIR/DSC18 and synchrotron ...

ABSTRACT Polymerization-induced self-assembly (PISA) of poly(glycerol monomethacrylate)–poly(2-hydroxypropyl methacrylate) (PGMA–PHPMA) diblocks is conducted using a RAFT aqueous dispersion polymerization formulation at 70 °C. Several PGMA macromolecular chain transfer agents (macro-CTAs) are chain-extended using a water-miscible monomer (HPMA): the growing PHPMA block becomes increasingly hydrophobic and hence drives in situ self-assembly. The final copolymer morphology in such PISA syntheses depends on just three parameters: the mean degree of polymerization (DP) of the PGMA stabilizer block, the mean DP of the PHPMA core-forming block, and the total solids concentration. Transmission electron microscopy is used to construct detailed diblock copolymer phase diagrams for PGMA DPs of 47, 78, and 112. For the shortest stabilizer block, there is essentially no concentration dependence: spheres, worms, or vesicles can be obtained even at 10% w/w solids simply by selecting the DP of the PHPMA block that gives the appropriate molecular curvature. For a PGMA DP of 78, the phase diagram is rich: and the copolymer morphology depends strongly on the total solids concentration. There is also a narrow region where spheres, worms, and vesicles coexist, which may be due to the effect of polydispersity. For a PGMA112 macro-CTA, the phase diagram is dominated by spherical morphologies. This is probably because the longer core-forming block DPs required to reduce the molecular curvature are significantly more dehydrated and hence less mobile, which prevents the in situ evolution of morphology from spheres to higher order morphologies. This hypothesis is supported by the observation that addition of ethanol to aqueous PISA syntheses conducted using the longer macro-CTAs allows access to diblock copolymer worms or vesicles, since this cosolvent solvates the core-forming PHPMA chains and hence increases their mobility at 70 °C. Elucidation of such phase diagrams is vital to ensure reproducible targeting of pure phases, rather than mixed phases.

ABSTRACT This paper describes the construction of a phase diagram for the as-cast state in the organic photovoltaic system P3HT:PCBM. Evidence for a transition to a phase-separated state at PCBM concentrations greater than 70 wt % is seen both by DMTA and GIWAXS, and the glass transition temperatures of blends in the single phase state below 70 wt % PCBM are observed to be raised compared to the pure polymer. Pure PCBM is observed to exhibit a thermal transition at 155 °C, an observation unreported to date—offering insight into crystallites commonly seen in device films. The liquid-crystal phase of P3HT is shown to persist in the presence of up to 41 wt % PCBM. In addition, pure PCBM is shown to be significantly hygroscopic, with important implications for the processing of high-performance devices.

... Auteur(s) / Author(s). MYKHAYLYK Oleksandr O. (1) ; CHAMBON Pierre (1) ; GRAHAM Richard S. (2 3) ; FAIRCLOUGH J. Patrick A. (1) ; OLMSTED Peter D. (2) ; RYAN Anthony J. (1) ; Affiliation(s) du ou des auteurs / Author(s) Affiliation(s). ...

Reversible addition-fragmentation chain transfer polymerization has been utilized to polymerize 2-hydroxypropyl methacrylate (HPMA) using a water-soluble macromolecular chain transfer agent based on poly(2-(methacryloyloxy)ethylphosphorylcholine) (PMPC). A detailed phase diagram has been elucidated for this aqueous dispersion polymerization formulation that reliably predicts the precise block compositions associated with well-defined particle morphologies (i.e., pure phases). Unlike the ad hoc approaches described in the literature, this strategy enables the facile, efficient, and reproducible preparation of diblock copolymer spheres, worms, or vesicles directly in concentrated aqueous solution. Chain extension of the highly hydrated zwitterionic PMPC block with HPMA in water at 70 °C produces a hydrophobic poly(2-hydroxypropyl methacrylate) (PHPMA) block, which drives in situ self-assembly to form well-defined diblock copolymer spheres, worms, or vesicles. The final particle morphology obtained at full monomer conversion is dictated by (i) the target degree of polymerization of the PHPMA block and (ii) the total solids concentration at which the HPMA polymerization is conducted. Moreover, if the targeted diblock copolymer composition corresponds to vesicle phase space at full monomer conversion, the in situ particle morphology evolves from spheres to worms to vesicles during the in situ polymerization of HPMA. In the case of PMPC(25)-PHPMA(400) particles, this systematic approach allows the direct, reproducible, and highly efficient preparation of either block copolymer vesicles at up to 25% solids or well-defined worms at 16-25% solids in aqueous solution.

... Based on the dimensions of the micelles and their changes with temperature and chain length, we can give a qualitative explanation to the morphological difference of these three E m B n blockcopolymers ... The free energy of a semi-crystalline block copolymer mainly consists ...

Polyvinylidene fluoride hollow fibers were prepared by melt-spinning technique under three spinning temperatures. The effects of annealing treatment on the structure and properties of hollow fiber were studied by differential scanning calorimetry (DSC), wide-angle X-ray diffraction (WAXD), tensile test, and scanning electron microscopy (SEM) measurements. DSC and WAXD results indicated that the annealing not only produced secondary crystallization but also perfected primary crystallization, and spinning and annealing temperature influenced the crystallinity of hollow fiber: the crystallinity decreased with the increase of spinning temperature; 140°C annealing increased the crystallinity, and hardly influenced the orientation of hollow fiber; above 150°C annealing increased the crystallinity as well, and furthermore had a comparative effect on the orientation. The tensile tests showed that the annealed samples, which did not present the obvious yield point, exhibited characteristics of hard elasticity, and all the hollow fiber had no neck phenomenon. Compared with the annealed sample, the precursor presented a clear yield point. In addition, the annealed samples had a higher break strength and initial modulus by contrast with the precursor, and the 140°C annealed sample showed the smallest break elongation. SEM demonstrated the micro-fiber structure appeared in surface of drawn sample. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 103: 935–941, 2007

... In pictures 1 and 2 of Figure 4 b the cores and starting point of the myelins are shown. Some of them display pearl instabilities at the myelin root, while others seem to grow very smoothly from the root on. ... Chem. Int. Ed. 2004, 43, 5004. 6 G. Battaglia, AJ Ryan, J. Am. Chem. Soc. ...