| 초록 |
We have shown that the temperature-induced changes in micellar characteristics of a symmetric styrene-isoprene (SI) diblock copolymer in a styrene-selective solvent. The mean aggregation number, can be quantified in dilute solution, and that this information provides a good guideline to interpret the observed transitions from spheres to cylinders in block copolymer solutions for high concentration. In order to understand morphological changes in more detail, one of the blocks is deuterated, i.e., PS-dPI and dPS-PI, and the contrast matching technique, in which scattering length density (SLD) of solvent used is identical to the SLD of corona chains was applied. The scattered intensity for these solutions was measured as a function of temperature on the 30 m NG7 spectrometer at NIST. The experimental results obtained demonstrate that for block copolymer solutions, the softening of inter-micelle potential with decrease in aggregation number would be the key feature for the various phase transitions upon heating. We also examined nondilute block copolymer solutions in the vicinity of order-disorder transition (ODT) from cylinders to disorder. Notably, the change in G’ and G” as a function of frequency clearly represents the solid-like transient behavior immediately after ODT from cylindrical microdomain. The temperature range of the transient phase is found to be quite dependent on the solvent-selectivity, which is confirmed by three kinds of solvents. |
