The Order-to-Disorder Transition of A Symmetric Polystyrene-block-Poly(2-vinyl pyridine) Copolymers with various amounts of Cadnium Chloride

The order-to-disorder transition [ODT] of a symmetric polystyrene-block-poly(2-vinyl pyridine) [PS-P2VP] copolymer with various amounts of cadmium chloride [CdCl$_{2}$] was investigated by rheometry, synchrotron small angle X-ray scattering (SAXS), and transmission electron microscopy. PS-P2VP was synthesized by the sequential anionic polymerization. The CdCl$_{2}$ can coordinate with the nitrogen in P2VP. Even though the amount of CdCl$_{2}$ was very small (less than 0.01 vol {\%}), the T$_{ODT}$ of PS-P2VP coordinated with CdCl$_{2}$ increased drastically. When the volume fraction of CdCl$_{2}$ is just 0.0023 (thus the molar ratio of [CdCl$_{2}$]/[P2VP] = 0.01), the T$_{ODT}$ was increased as large as about 10 $^{o}$C compared with that of neat PS-P2VP. This is because the chain motion of P2VP block is severely restricted by coordination of CdCl$_{2}$ with P2VP. The order-to-disorder transition temperatures for [CdCl$_{2}$] / [2VP] = 0, 0.01, 0.02, 0.03 and 0.04 are 199.2, 209.9, 234.6, 260.2 and 279.8 $^{o}$C, respectively. In addition to the large increase of domain spacing of microstructure was also found in this study even though the amount of CdCl$_{2}$ was very small.