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Effect of Stretching on the Structure of Cylinder- and Sphere-Forming Styrene-Isoprene-Styrene Block Copolymers

DOI: 10.1021/ma8026639 DOI Help

Authors: Joanna Stasiak (University of Cambridge) , Adam Squires (University of Reading) , Valeria Castelletto (University of Reading) , Ian Hamley (Diamond Light Source) , Geoff D. Moggridge (University of Cambridge)
Co-authored by industrial partner: No

Type: Journal Paper
Journal: Macromolecules , VOL 42 (14) , PAGES 5252-5265

State: Published (Approved)
Published: June 2009

Abstract: Two styrene-isoprene-styrene block copolymers Vector 4111 and 4113, exhibiting cylindrical (18 wt % PS) and spherical (16 wt % PS) morphology, respectively, have been examined under uniaxial elongation up to 200% strain. On the basis of stress-strain data, mechanical properties are compared for isotropic and oriented polystyrene domains. The structure at various stages of deformation has been determined from SAXS patterns in three planes and two principal deformation directions with respect to orientation. Samples showed a very high degree of hexagonal packing, resulting in an X-ray pattern taken parallel to the cylinder alignment approaching single crystal ordering. Cylinders were aligned with the closest packed planes parallel to film surface. Particular attention has been paid to a lattice deformation process occurring during the first stretching and relaxation cycle. For a copolymer with oriented cylindrical morphology the deformation was affine up to 120% strain. The microdomain spacing was calculated parallel and perpendicular to the stretching direction. The cylindrical microstructure orientation, quantified by Hermans' orientation factor reduced during elongation of oriented polymer, while the elongation of isotropic sample caused an increase of orientation. Deformation of all studied morphologies was reversible.

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Added On: 18/06/2010 10:13

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