Light-Scattering Study of Semiflexible Polymer Solutions. 4. n-Hexane Solutions of Poly(n-hexyl isocyanate)

Static light-scattering behavior was investigated for semidilute n-hexane solutions of poly(n-hexyl isocyanate) (PHIC). At 25 °C, the monomer-unit structure factor Ŝ(k) of the solutions was favorably compared with the generalized Ornstein−Zernike integral equation theory, and the strength of the attractive interaction between PHIC chains in n-hexane was estimated to be very weak. On the other hand, after the solutions were quenched at 15 °C, theoretically unexpected enhanced low-angle scattering was observed. While Ŝ(k) gradually increased with the quenching time, the anomaly disappeared by heating or diluting the solutions. The normal Ŝ(k) was also recovered by subtracting the anomalous component from Ŝ(k) of quenched solutions using dynamic light-scattering results. The anomaly in Ŝ(k) indicates the formation of aggregates or clusters of PHIC chains in quenched solutions. A strong interchain attractive interaction expected in aggregates is in a contrast with the weak interaction among molecularly dispersed PHIC chains.