Dynamic light scattering from semidilute solutions of a styrene-acrylonitrile random copolymer

Haifeng Zheng, Iwao Teraoka

Research output: Contribution to journalArticlepeer-review


Dynamics of a random copolymer, poly(styrene-co-acrylonitrile), in dilute and semidilute solutions was studied by using dynamic light scattering. The solvent used was a mixture of dioxane and acetonitrile (ACN). The mixing ratio and the temperature were changed to provide the copolymer with various solvent conditions that range from a good to a ⊖ solvent. At low ACN contents, the autocorrelation function of the light scattering intensity had a single relaxation mode. Its diffusion changed from the mutual diffusion to the cooperative diffusion of entangled chains in the good solvent as the concentration c increased. At high ACN contents (near ⊖), the diffusion coefficient decreased to 1/3 of the dilute solution value and the scattering intensity increased almost linearly with c, before the diffusion coefficient turned to increase as ∼c and the scattering intensity to decrease as ∼c-1, indicating the cooperative diffusion of entangled ⊖ chains. In this high concentration range, the autocorrelation function exhibited a slow diffusion mode as well. A high friction coefficient and an extended near-linear range in the scattering intensity, especially at low temperatures, suggest dynamic clustering of chains upon increasing the concentration.

Original languageEnglish (US)
Pages (from-to)6074-6082
Number of pages9
Issue number17
StatePublished - Aug 14 2001

ASJC Scopus subject areas

  • Organic Chemistry
  • Polymers and Plastics
  • Inorganic Chemistry
  • Materials Chemistry


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