Structure, function, self-assembly, and applications of bottlebrush copolymers

Abstract

Bottlebrush polymers are a type of branched or graft polymer with polymeric side-chains attached to a linear backbone, and the unusual architecture of bottlebrushes provides a number of unique and potentially useful properties. These include a high entanglement molecular weight, enabling rapid self-assembly of bottlebrush block copolymers into large domain structures, the self-assembly of bottlebrush block copolymer micelles in a selective solvent even at very low dilutions, and the functionalization of bottlebrush side-chains for recognition, imaging, or drug 2 delivery in aqueous environments. This review article focuses on recent developments in the field of bottlebrush polymers with an emphasis on applications of bottlebrush copolymers.Bottlebrush copolymers contain two (or more) different types of polymeric side-chains. Recent work has explored the diverse properties and functions of bottlebrush polymers and copolymers in solutions, films, and melts, and applications explored include photonic materials, bottlebrush films for lithographic patterning, drug delivery, and tumor detection and imaging. We provide a brief introduction to bottlebrush synthesis and physical properties and then discuss work related to: i) bottlebrush self-assembly in melts and bulk thin films, ii) bottlebrushes for photonics and lithography, iii) bottlebrushes for small molecule encapsulation and delivery in solution, and iv) bottlebrush micelles and assemblies in solution. We briefly discuss three potential areas for future research, including developing a more quantitative model of bottlebrush self-assembly in the bulk, studying the properties of bottlebrushes at interfaces, and investigating the solution assembly of bottlebrush copolymers.

Architecture, Assembly, and Emerging Applications of Branched Functional Polyelectrolytes and Poly(ionic liquid)s

“…66 The unusual architecture of CPBs gives them some unique properties such as large dimensions of macromolecules, a low entanglement extent, and a lower critical micelle concentration (CMC). 67 It has been shown that CPBs with poly(L-lysine) side chains and sodium dodecylsulfate (SDS) can form complexes with intriguing structures. 80 An increasing amount of SDS initiates the complex transformation to a helical conformation with a local β-sheet structure on the side chains, followed by a spherically collapsed structure formation.…”

Effects of Grafting Density on Block Polymer Self-Assembly: From Linear to Bottlebrush

“…[13][14][15][16][17][18][19][20] However, bottlebrush block polymers display much larger scaling exponents ( = 0.8-0.9), [21][22][23][24] consistent with extended backbone conformations. Steric repulsion between the densely grafted side chains imparts a certain bending rigidity to the backbone, which can be modeled as a wormlike chain.…”

Thermomechanical Behavior and Local Dynamics of Dendronized Block Copolymers and Constituent Homopolymers

“…8 Congestion imparted by the repeat units enforces the polymer main-chain elongation with a low potential for chain entanglement. 9 Molecular brush copolymers can be synthesized by graftingfrom, grafting-to, and grafting-through strategies. 10 Using ruthenium mediated ring-opening metathesis polymerization (ROMP), we have been interested in the grafting-through approach, directly polymerizing norbornene-functionalized macromonomers, ensuring that every repeat unit consists of a polymeric repeat unit, to well-defined brush BCPs.…”