Phase Structure of the Exact Graft Copolymer Synthesized by Iterative Methodology Based on Living Anionic Polymerization

Abstract

Exact graft copolymer (EGC) is a type of copolymer with precisely defined molecular para meters, including the number of grafts per molecule (n), the length of the grafts (l g ), and the separation distance between the junction points (ε) in the backbone. In the present study, the phase structure of the EGC composed of poly(2vinyl pyridine) backbone and polysty rene graft with n = 2 and n = 3 under fixed ε and l g is systematically investigated to seek a general understanding on the effect of the graft architecture on the domain spacing of the microphaseseparated structure and the order-disorder tran sition temperature (T ODT ). It is found that the T ODT associ ated with the fluctuationinduced ODT of the EGC increases with increasing n due to the increase of the total molecular weight. Nevertheless, the domain spacing does not exhibit a monotonic change with n, as the EGC with n = 2 shows the largest domain spacing compared with that of EGC with n = 3 and the corresponding linear diblock copolymer. The experi mental observation on the domain spacing is explained by a thermodynamic model considering the packing mode of the constituting chains under the junction constraint.