Graft-through Synthesis and Assembly of Janus Bottlebrush Polymers from A-Branch-B Diblock Macromonomers

Abstract

We report the synthesis of Janus bottlebrush block copolymers by graft-through polymerization of branched diblock macromonomers. Self-assembly of the bottlebrushes was characterized by small-angle X-ray scattering, atomic force microscopy, and scanning electron microscopy. Phase separation and packing models of the bottlebrushes were computed, and their self-assembly behavior was corroborated experimentally in bulk and in thin films. Lamellar, hexagonal cylinder, and gyroid phases were observed and modeled. The A-branch-B Janus bottlebrush structure provides several unique advantages in the context of bottlebrush polymer assembly, including access to the first examples of gyroid phases.

Thermal Approaches to Perpendicular Block Copolymer Microdomains in Thin Films: A Review and Appraisal

“…Nonlinear polymers generally fall into one of the following categories: cyclic, star‐shaped (branched), hyperbranched, dendrimeric, and graft polymers. Since chain conformation is directly influenced by chain architecture, it is unsurprising that BCP bulk self‐assembly is also heavily influenced by the architecture of the BCP chain . Chain packing of nonlinear BCPs deviates from that of their linear counterparts, resulting in unorthodox morphologies, a shift in the phase diagram, and/or a change in the order‐to‐disorder transition (ODT) temperature .…”

“…By compiling a library of works on the self‐assembly of nonlinear BCPs we can tentatively postulate that BCP chains must be tethered together at the chain ends in order for the orientation‐determining entropic effect to come into play. Various cyclic, branched, miktoarm star, and bottlebrush BCPs do not fit this criterion and thus do not elicit the same self‐neutralizing behavior. Currently, the lone exception to this hypothesis is one pom‐pom‐shaped PS star ‐ b ‐PI linear ‐ b ‐PS star in a work by Wijayasekara et al., but only the surface morphology was characterized by AFM in this case.…”

Cationic Bottlebrush Polymers from Quaternary Ammonium Macromonomers by Grafting‐Through Ring‐Opening Metathesis Polymerization

“…ROMP also has demonstrated a wide functional group tolerance to produce well‐defined bottlebrush block copolymers with MMs carrying heteroatom functional groups through sequential ROMP 43–46. Well‐controlled MMs are needed for well‐defined bottlebrush polymers and they have been synthesized from a variety of techniques, which suppress side reactions of norbornene incorporation, such as reversible addition‐fragmentation chain transfer (RAFT) polymerization,47–49 atom transfer radical polymerization (ATRP),50–52 living anionic polymerization (LAP),53,54 ring‐opening polymerization (ROP),55 and other types of polymerizations 56,57. Thus, a wide library of potential MMs exist to create new bottlebrush block copolymers.…”

Influence of residual impurities on ring‐opening metathesis polymerization after copper(I)‐catalyzed alkyne‐azide cycloaddition click reaction

“…The compact and confined structures endow unique properties, which other polymers could not have . With a combination of recent tremendous progress in polymer synthesis techniques, BBPs synthesis of high structural intricacy is realized and simultaneously their applications such as lithography, drug delivery, and photonic crystals have been demonstrated.…”