Fuente: Journal of applied polymer Lugar: RESEARCH ARTICLE The microphase structures of three poly(styrene-b-isoprene-b-styrene) thermoplastic elastomers were studied via time–temperature superposition; the terminal-region scaling differences in storage modulus master curves stem from morphologies as BCC (SIS1105, ratios 1:√2:√3:√7), HEX (SIS1209, ratios 1:√3:√7:√9), and LAM (SIS5562, ratios 1:2:3:4), establishing an intrinsic link between macroscopic rheology and microphase separation.

ABSTRACT
This study systematically investigates the correlation between microphase structures and rheological behavior in three poly(styrene-b-isoprene-b-styrene) (SIS) triblock copolymers with varying polystyrene contents, employing a multi-technique approach combining time–temperature superposition (TTS), small-angle X-ray scattering (SAXS), and transmission electron microscopy (TEM). The results demonstrate that the applicability of TTS in the terminal region is strongly influenced by polystyrene content. For the low-polystyrene-content sample (SIS1105, PSwt.
= 15%), TTS fails at low angular frequencies ω, with the terminal slope increasing markedly with temperature, indicating temperature-dependent disruption of its microstructure under dynamic shear. At lower temperatures (130°C–150°C), however, its average terminal slope stabilizes around 0.247 (≈0), consistent with a body-centered cubic (BCC) arrangement of spherical microdomains. In contrast, high-polystyrene-content samples (SIS1209, PSwt.
= 29% and SIS5562, PSwt.
= 45%) exhibit perfect TTS behavior, with nearly constant terminal slopes averaging 0.330 (≈1/3) and 0.470 (≈1/2), corresponding to hexagonally packed cylindrical (HEX) microdomains and alternating lamellar (LAM) microphase structures, respectively. These results are in excellent agreement with SAXS and TEM observations.