Order-to-Disorder Transitions in Lamellar Melt Self-Assembled Core-Shell Bottlebrush Polymers.

We report the synthesis and melt self-assembly behaviors of densely grafted, core-shell bottlebrush (csBB) polymers derived from covalently linking narrow dispersity, symmetric composition ABA-type triblock polymers through their chain midpoints. Derived from sequential ring-opening polymerizations of ε-decalactone and rac -lactide initiated from 5-norbornene-2- exo ,3- exo -dimethanol, poly(lactide- block -ε-decalactone- block -lactide) macromonomers ( M n = 9.2-17.8 kg/mol; Đ = 1.19-1.25) were enchained by living ring-opening metathesis polymerization (ROMP) into csBBs with backbone degrees of polymerization N bb = 8-43. Temperature-dependent small-angle X-ray scattering (SAXS) studies indicate that the critical triblock arm degree of polymerization ( N arm ) required for melt segregation decreases with increasing N bb , leading to reductions in the accessible ordered lamellar microdomain ( d ) spacings. We derive a phenomenological relationship between the critical triblock arm segregation strength at the order-disorder transition (χ N arm ) ODT and N bb to enable the future design of microphase separated core-shell bottlebrushes, which self-assemble at sub-10 nm length scales for nanolithography and nanotemplating applications.