LIGHT-SCATTERING STUDY OF SEMIFLEXIBLE POLYMER-SOLUTIONS .1. DILUTE THROUGH SEMIDILUTE SOLUTIONS OF POLY(N-HEXYL ISOCYANATE) DISSOLVED IN DICHLOROMETHANE

Dilute through semidilute solutions of a semiflexible polymer, poly(n- hexylisocyanate) (PHIC), dissolved in a good solvent, dichloromethane (DCM), were studied by static light scattering as well as by sedimenta tion equilibrium. The solutions showed the following characteristic fe atures, which were distinct from those of flexible polymer-good solven t systems. (1) The second virial coefficient was independent of the mo lecular weight. (2) The reduced third virial coefficient was much smal ler than that for a flexible polymer in a good solvent. (3) The concen tration dependences of the osmotic compressibility (partial derivative c/partial derivative II), and correlation length xi did not obey the scaling law nor the prediction of the renormalization group theory tha t was successful for flexible polymer-good solvent systems. Except for the correlation length results, the above features were favorably com pared with a scaled particle theory including a weak attractive intera ction. The present study is an advance on a previous work (Sate, T.; T eramoto, A. Mol. Cryst. Liq. Cryst. 1990, 178, 143) in that thermodyna mic properties of semiflexible polymer solutions are understood on a m ore realistic molecular basis taking an attractive potential into acco unt.