Polymer Brushes: Efficient Synthesis and Applications.

Polymer brushes are special macromolecular structures with polymer chains densely tethered to another polymer chain (one-dimensional, 1D) or the surface of a planar (two-dimensional, 2D), spherical or cylindrical (three-dimensional, 3D) solid via a stable covalent or noncovalent bond linkage. In comparison with the corresponding linear counterpart with similar molecular composition, one-dimension polymer brushes have some fascinating properties including wormlike conformation, compact molecular dimension, and notable chain end effects due to their compact and confined densely grafted structure. The introduction of polymer chains onto the surface of planar and spherical or cylindrical matrix will not only significantly change the surface-related properties of the matrix but also endows the obtained hybrid polymer brushes with new functionalities. Thus, polymer brushes are of great interest in the fields of polymer and material science due to their broad applications, such as catalysis, nanolithography, biomineralization, drug delivery, medical diagnosis, optoelectronics, and so on. Although a variety of 1D, 2D, and 3D polymer brushes have been prepared with the advent of living/controlled polymerization, the development of more efficient and facile synthetic protocols that permit access to polymer brushes with precisely controlled composition, structure, and functionality still represents a key contemporary challenge. In this Account, we summarize our recent efforts on the development of efficient methods to prepare 1D, 2D, and 3D polymer brushes and exploration of their potential applications in drug delivery, antifouling coating, catalysis, and lithium-ion batteries and also highlight related achievements by other groups. First, we briefly introduce the precedent examples of efficient synthesis of polymer brushes with different structures and functionalities by the combination of monomer design with living/controlled polymerization. Given the excellent tolerance and use of the same catalytic system without any mutual interference of ATRP and Cu-catalyzed alkyne-azide cyclization (CuAAC) click reaction, a versatile and efficient platform for precise synthesis of complex asymmetric (Janus-type) 1D polymer brushes was developed on the basis of the "trifunctional monomer" strategy without polymeric functionality transformation. Subsequently, a noncovalent strategy based on crystallization-driven self assembly to prepare well-defined polymer brushes with precise control over their composition and dimensions is described. Notably, the crystallization-driven self assembly can be treated as a living/controlled polymerization of "polymeric monomer" with a special building segment for crystallization, which allows for preparing linear polymer brushes with length as high as tens of micrometers. Moreover, the properties and related applications of polymer brushes as interesting building blocks for constructing hierarchical nanostructures, efficient drug deliver carriers, antifouling films, and lithium-ion batteries are addressed by some typical examples. These advancements in this field will provide a new avenue for obtaining fascinating polymer-brush-based functional materials.