Evolution of structure in a graft copolymer-homopolymer blend under strain

• Published in: Ground water 1993-07, Vol.26 (14), p.3676-3680
• Main Authors: Rabeony, M, Peiffer, D. G, Dozier, W. D, Lin, M. Y
• Format: Article
• Language: English
• Subjects: 360602 - Other Materials- Structure & Phase Studies; Applied sciences; COPOLYMERS; DIGITAL SYSTEMS; Exact sciences and technology; GRAFT POLYMERS; IMAGE PROCESSING; LIGHT SCATTERING; MATERIALS SCIENCE; MOLECULAR STRUCTURE; ORGANIC COMPOUNDS; ORGANIC POLYMERS; Physicochemistry of polymers; POLYMERS; PROCESSING; Properties and characterization; SCATTERING; Structure, morphology and analysis
• ISSN: 0024-9297; 0017-467X; 1520-5835; 1745-6584
• DOI: 10.1021/ma00066a028

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.