Chromatic transition of pi-conjugated polydiacetylene and the subsequent aggregation phenomena

Static and dynamic light scattering from pi-conjugated poly(4BCMU) in tolue ne solutions were measured at 353 K (yellow phase) and 323 K (red phase) to evaluate the hydrodynamic radius R-h and the fractal dimension D. It was s uggested that poly(4BCMU) may exist not as an isolated worm-like chain but as a weakly interacted cluster-like domain in the yellow phase. The domain was considered to be elaborated by inter-molecular hydrogen bondings formed newly through a thermal break of intra-molecular hydrogen bondings between side chains along a main chain. On the other hand, the increases in R-h an d D have revealed that poly(4BCMU) chains aggregated gradually in the red p hase, after taking a single extended rod-like conformation. The subsequent aggregation seemed to be promoted not only by lowering a solvent quality bu t also by increasing the effective concentration, accompanied by the confor mational transition. (C) 1999 Elsevier Science Ltd. All rights reserved.