Design of Thermoplastic Elastomers with Self-Consistent Mean Field Theory: Radial (ABA)$_n$ and A(BA)$_n$ Miktoarm Architectures

Two thermoplastic elastomer designs were evaluated using self-consistent mean field theory. The phase diagram of a radial (A$_1$BA$_2$)$_n$ block copolymer was calculated at $ \chi N$ = 40 per arm as a function of composition ($\emph{f}_A$) and asymmetry between the A end-blocks ($\tau = N_{A1}/(N_{A1}+N_{A2})$). Significant deflection of the phase boundaries towards larger $\emph{f}_A$ occurred for asymmetric triblock copolymers ($\tau\approx 0.15$ and $ \tau\approx 0.90$) due to the interplay between bidispersity and chain-pullout of the A-blocks. The phase diagram of an A$_1$(BA$_2$)$_n$ miktoarm star triblock copolymer was also investigated as a function of $\emph{f}_A$ and $\tau$ at $\chi N$ = 40 per A$_1$BA$_2$ unit. Similar deflections in phase boundaries towards higher $\emph{f}_A$ resulted.