Browsing by Author "Mai, YW"

Now showing 1 - 2 of 2
  • No Thumbnail Available
    Item
    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.
  • No Thumbnail Available
    Item
    Reactive block copolymer modified thermosets: highly ordered nanostructures and improved properties
    (Royal Society of Chemistry, 2010-12-21) Hameed, N; Guo, Q; Xu, ZG; Hanley, TL; Mai, YW
    A highly ordered poly(dimethyl siloxane)-poly(glycidyl methacrylate) (PDMS-PGMA) reactive diblock copolymer was synthesized and used to modify bisphenol A-type epoxy resin (ER). The PDMS-PGMA block copolymer consisted of epoxy-miscible PGMA blocks and an epoxy-immiscible PDMS block. The PGMA reactive block of the block copolymer formed covalent bonds with cured epoxy and was involved in the network formation, and the PDMS block phase separated to give different ordered and disordered nanostructures at different blend compositions. The solvent cast PDMS-PGMA diblock copolymer showed ordered hexagonal cylindrical morphology. A highly ordered morphology consisting of hexagonal cylinders inside the lamellar morphology was observed in the cured PDMS-PGMA block copolymer. In the cured ER/PDMS-PGMA blends, a variety of morphologies including lamellar, cubic and worm-like and spherical nanostructures were detected depending on the blend composition. Moreover, the addition of this reactive diblock copolymer significantly increases the hydrophobicity and the glass transition temperature. It also improves the tensile strength and tensile ductility of the nanostructured thermosets at low diblock copolymer contents. © 2010, Royal Society of Chemistry