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

Exact graft copolymer (EGC) is a type of copolymer with precisely defined molecular parameters, 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(2-vinyl pyridine) backbone and polystyrene 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 microphase-separated structure and the order–disorder transition temperature (T_ODT). It is found that the T_ODT associated with the fluctuation-induced 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 experimental observation on the domain spacing is explained by a thermodynamic model considering the packing mode of the constituting chains under the junction constraint. (Figure presented.).