Segregation and conformational transition in triblock copolymers: Part 2. Light-scattering studies

✍ Scribed by A. Dondos; P. Rempp; H.C. Benoit

• Book ID: 104164279
• Publisher: Elsevier Science
• Year: 1972
• Tongue: English
• Weight: 464 KB
• Volume: 13
• Category: Article
• ISSN: 0032-3861
• DOI: 10.1016/s0032-3861(72)80002-8

✦ Synopsis

From light-scattering experiments carried out on a polystyrene (PS) sample, a poly(methyl methacrylate) (PMMA) sample, on a random copolymer of styrene and MMA and on an anionically prepared triblock copolymer PMMA-PS-PMMA, all of the same molecular weight, in various solvents over a range of temperature (18-65~ it was shown that a conformational transition occurs for the triblock copolymer. At lower temperatures seg~egation occurs and the second virial coefficient A2 is the weighted average between the A2A and Azt~ values for the corresponding homopolymers (PS and PMMA). At higher temperatures contacts between chemically unlike parts of the molecule become possible, and the additivity rules are no more valid for Az, as well as for the expansion coefficient. This change from a segregated to a 'pseudo-gaussian' conformation involves a change in specific volume of the molecule, and it therefore brings with it an. abnormal variation of the refractive index increment, which has been investigated on the same light-scattering diagrams.