Influence of associations on self-diffusion of styrene–methylmethacrylate random copolymers in semidilute acetone solution
✍ Scribed by Gerald Fleischer; Frank Rittig; Čestmír Koňák
- Publisher
- John Wiley and Sons
- Year
- 1998
- Tongue
- English
- Weight
- 184 KB
- Volume
- 36
- Category
- Article
- ISSN
- 0887-6266
No coin nor oath required. For personal study only.
✦ Synopsis
The self-diffusion of four styrene-methylmethacrylate random copolymers dissolved in acetone, a thermodynamically bad solvent for the styrene sequences in the copolymer, were investigated by pulsed-field gradient NMR. The echo attenuations S inc (q,t) are dominated by diffusion of clusters. At higher concentrations, physical gelation sets in (formation of a transient network), which is manifested in an anomalous, restricted diffusion at short observation times. The measured fluctuations of the positions of the chain segments in the transient network have an amplitude of about 100 nm. The free long-range diffusion attained at long observation times shows a much stronger concentration dependence than in the nonassociating solvent benzene. The results are in accord with light-scattering investigations.