SCFT Studies on the Phase Transitions and Domain Spacing of the Bottlebrush Copolymers

Using the self-consistent mean filed theories, the order-disorder transitions (ODT) values $(N\chi )_{\mbox{ODT}} $ are calculated for AB bottlebrush copolymers with different lengths of the backbone and grafted chains, or with different chain-length-ratio between the grafted A and B chains. Increasing the fractions of the grafted chains gives a disordering effect on the microphases and causes the $(N\chi )_{\mbox{ODT}} $ values to increase. Contrarily, increasing the backbone fraction yields an ordering effect and causes the $(N\chi )_{\mbox{ODT}} $ values to decrease. For copolymers with the branches of the same sizes, the domain spacing $D$ depends on the backbone length. Its scaling exponent firstly increases and then decreases with the increase of the graft chain length. The domain spacing $D$ increases with the length of the grafted chains $r_{\mbox{G}} $ for bottlebrush copolymers with the same backbone. In weak segregation level, the SCFT calculations indicate that $D\propto r_{\mbox{G}}^{0.30}$, which reveals the smaller exponent than that predicted recently by the strong segregation analysis (0.35).