Evolution of structure in graft copolymer-homopolymer blend under strain
- Exxon Research and Engineering Co., Annandale, NJ (United States). Corporate Research Science Lab.
- Argonne National Lab., IL (United States)
- National Institute of Standards and Technology, Gaithersburg, MD (United States)
Two-dimensional light scattering and digital imaging studies of the structural evolution in a graft copolymer-homopolymer blend under quasi-static elongation are reported. The graft copolymer consists of a polydisperse elastomeric poly(ethyl acrylate)(PEA) backbone onto which monodisperse thermoplastic polystyrene (PS) chains are grafted. The homopolymer poly(ethyl acrylate) is produced in situ since grafts are not incorporated into every chain. The quasi-equilibrium structure of the graft copolymer blend cast from a good solvent exhibits isotropic scattering with an inverse characteristic length q[sub m][approx]4[mu]m[sup [minus]1]. When the blend is subject to a quasi-static elongation ratio [gamma] (=final length/initial length), three regimes are observed: (1) A transition regime at very low elongation ratios where the system behaves reversibly. (2) A hyperelastic regime where the spinodal ring deforms in an anisotropic manner. The intensity I[sub [parallel]] (q[sub z]) parallel to the elongation increases in an exponential manner due to cooperative alignment of the hard PS-rich phase, and its peak position shifts in an affine manner to smaller values (i.e., q[sub zm][approximately][gamma][sup [minus]1]). Moreover, the scattered light perpendicular to the elongation, I[sub [perpendicular]](q[sub y]), decreases in intensity as its peak position q[sub ym] diverges to infinity. (3) A plastic regime where I[sub [parallel]](q[sub z]) remains nearly constant as its position q[sub zm] converges to a finite value at q[sub zm][approx]0.9[mu]m[sup [minus]1]. In the three regimes, the structure factor parallel to the elongation, S[sub [parallel]](q[sub z]), remains self-similar. The underlying mechanism of the deformation will be discussed within the framework of concentration fluctuations in soft elastic two-component solids.
- OSTI ID:
- 6469005
- Journal Information:
- Ground Water; (United States), Vol. 31:4; ISSN 0017-467X
- Country of Publication:
- United States
- Language:
- English
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