Browsing by Author "Guo, QP"

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    Hydrogen bonding interactions, crystallization, and surface hydrophobicity in nanostructured epoxy/block copolymer blends
    (Wiley-Blackwell, 2010-04-01) Hameed, N; Guo, QP; Hanley, TL; Mai, YW
    Hydrogen bonding interactions, phase behavior, crystallization, and surface hydrophobicity in nanostructured blend of bisphenol A-type epoxy resin (ER), for example, diglycidyl ether of bisphenol A (DGEBA) and poly(-caprolactone)-block-poly(dimethyl siloxane)-block-poly(-caprolactone) (PCL-PDMS-PCL) triblock copolymer were investigated by Fourier transform infrared (FTIR) spectroscopy, differential scanning calorimetry, transmission electron microscopy, small-angle X-ray scattering, and contact angle measurements. The PCL-PDMS-PCL triblock copolymer consisted of two epoxy-miscible PCL blocks and an epoxy-immiscible PDMS block. The cured ER/PCL-PDMS-PCL blends showed composition-dependent nanostructures from spherical and worm-like microdomains to lamellar morphology. FTIR study revealed the existence of hydrogen bonding interactions between the PCL blocks and the cured epoxy, which was responsible for their miscibility. The overall crystallization rate of the PCL blocks in the blend decreased remarkably with increasing ER content, whereas the melting point was slightly depressed in the blends. The surface hydrophobicity of the cured ER increased upon addition of the block copolymer, whereas the surface free energy (γs) values decreased with increasing block copolymer concentration. The hydrophilicity of the epoxy could be reduced through blending with the PCL-PDMS-PCL block copolymer that contained a hydrophobic PDMS block. © 2010, Wiley-Blackwell.
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    Microphase separation induced by competitive hydrogen bonding interactions in semicrystalline triblock copolymer/homopolymer complexes
    (Royal Society of Chemistry, 2013-01-01) Salim, NV; Hameed, N; Hanley, TL; Guo, QP
    Microphase separation through competitive hydrogen bonding interactions in ABC/D triblock copolymer/homopolymer complexes is studied for the first time. This study investigated self-assembled nanostructures that are obtained in the bulk, by the complexation of a semicrystalline polystyrene-block-poly(4-vinylpyridine)-block-poly(ethylene oxide) (SVPEO) triblock copolymer with a poly(4-vinyl phenol) (PVPh) homopolymer in tetrahydrofuran (THF). In these complexes, microphase separation takes place due to the disparity in intermolecular interactions among PVPh/P4VP and PVPh/PEO pairs. At low PVPh concentrations, PEO interacts relatively weakly with PVPh, whereas in the complexes containing more than 30 wt% PVPh, the PEO block interacts considerably with PVPh, leading to the formation of composition-dependent nanostructures. SAXS and TEM results indicate that the cylindrical morphology of a neat SVPEO triblock copolymer changes into lamellae structures at 20 wt% of PVPh then to disordered lamellae with 40 wt% PVPh. Wormlike structures are obtained in the complex with 50 wt% PVPh, followed by disordered spherical microdomains with size in the order of 40-50 nm in the complexes with 60-80 wt% PVPh. Moreover, when the content of PVPh increases to 80 wt%, the complexes show a completely homogenous phase of PVPh/P4VP and PVPh/PEO with phase separated spherical PS domains. The fractional crystallization behavior in SVPEO and complexes at lower PVPh content was also examined. A structural model was proposed to explain the microphase separation and self-assembled morphologies of these complexes based on the experimental results obtained. The formation of nanostructures and changes in morphologies depend on the relative strength of hydrogen bonding interactions between each component block of the copolymer and the homopolymer. © 2013, Royal Society of Chemistry