A morphological study of three I5S six-arm miktoarm star block copolymers is presented. These miktoarm stars are comprised of five arms of polyisoprene (PI) and one arm of polystyrene (PS) joined together at a single junction point. The strong segregation limit theory for the morphological behavior of miktoarm stars predicts that these materials should form spherical morphologies, but only lamellar and cylindrical morphologies were observed by TEM and SAXS. These results are similar to previously reported discrepancies between experimentally observed morphological behaviors of miktoarm stars and the predictions of the theory. Previous work has attributed the discrepancies to the neglect of the effect of the multifunctional junction points on calculated free energies. The current results suggest that, in addition to this, geometrical packing constraints prevent the formation of morphologies such as spheres and cylinders in highly asymmetric miktoarm stars in which the minor volume fraction component would need to occupy the matrix phase. Finally, unusual broken chevron tilt grain boundary morphologies were observed in a lamellar I 5S material. We attribute these new structures to the asymmetric energy penalties for interfacial bending which result from the molecular asymmetry of the miktoarm stars.

The bulk morphology of a crystalline/amorphous diblock copolymer under different thermal conditions was studied. The diblock copolymer, poly((ethylene oxide)-b-1,4-polybutadiene), forms a microphase-separated lamellar morphology in the molten state. For samples crystallized within the range of 20−50 °C, TEM coupled with electron diffraction revealed a microphase-separated, alternating lamellar morphology with the PEO crystalline chains oriented perpendicular to the interface between the PEO and PBD domains. A significant increase in the microphase-separated, lamellar domain spacing was observed upon crystallization. On the length scale of tens of microns, as probed by polarizing optical microscopy, a nonspherultic crystalline texture (with the absence of the Maltese cross), corresponding to the microphase-separated lamellar grain morphology, was observed. In contrast to the integral chain folding observed in PEO homopolymer, the increase in PEO lamellar thickness with decreasing undercooling is continuous in the block copolymer. In addition, the equilibrium melting temperature and lamellar spacing were determined.

This work is part of an extensive study of model nonlinear block copolymer/homopolymer blends. Effects of graft molecular architecture on the morphology of block copolymer/homopolymer blends have been examined. The single graft Y-shaped block copolymers used in the study are I 2S block copolymers, which have two low polydispersity (PDI) polyisoprene arms and one low PDI polystyrene arm joint at a single junction point. Previously reported linear diblock copolymer/homopolymer blend systems showed that the order-order transitions (OOTs) occur at about the same volume fractions as in pure linear diblock copolymers. The OOT occurs at the same volume fraction regardless of the direction from which it is approached, i.e., blending homopolymer A with a diblock which forms A cylinders in a B matrix to push it toward lamella or blending B homopolymer with a lamellar diblock to push it back toward cylinders. This study shows that when a homopolymer is blended with an I 2S block copolymer, the OOTs split so that they occur at different volume fractions depending up whether they are approached by blending homopolymer into the two-arm or the one-arm side of the block copolymer interface. A perforated lamellar morphology is obtained in a blend of homopolystyrene (hPS) and a lamella forming single graft block copolymer, and it is found to be stable to thermal annealing.

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Morphology development was investigated during blending of linear low density polyethylene (LLDPE) and polystyrene (PS) (the minor phase) in a tangential counter-rotating twin screw extruder, with and without the use of 5 wt.-% Kraton styrene-ethylene/butylene-styrene (SEBS) triblock copolymers as compatibilizing agents. Dispersive mixing in the Non-Intermeshing Twin Screw Extruder (NITSE) is improved with an increase of percent drag flow up to 50 %; the screws configuration includes reverse flight elements and/or cylinders. Experiments have indicated that the combined effect of the reverse flight elements and cylinders increases the reduction rate of droplets due to a longer time in the feed screw where the most significant changes of phase morphology occur. Screw stagger has been shown to have a minor effect on the phase scale of the final dispersion. The more significant reduction of the phase scale is achieved by increasing screw speed under constant flow conditions.

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Via surface aldolisation or semi-aldolisation, the surface of poly(vinyl alcohol) (PVA) microspheres was uniformly doped with sliver nanoparticles (AgNPs). Scanning electron microscope (SEM) revealed the spherical shape of the AgNPs@PVA microspheres. Fourier transform infrared spectra and X-ray photoelectron spectra (XPS) provided information on the surface interactions between AgNPs and PVA microspheres. The AgNPs@PVA microspheres offered simple and rapid qualitative detection of Hg 2+ ions and pH values through a colour change in aqueous solution. The AgNPs@PVA microspheres also showed off-on behaviour.