Recent advances in supramolecular block copolymers for biomedical applications

Supramolecular block copolymers (SBCs) have received considerable interest in polymer chemistry, materials science, biomedical engineering and nanotechnology owing to their unique structural and functional advantages, such as low cytotoxicity, outstanding biodegradability, smart environmental responsiveness, and so forth. SBCs comprise two or more different homopolymer subunits linked by noncovalent bonds, and these polymers, in particular, combine the dynamically reversible nature of supramolecular polymers with the hierarchical microphase-separated structures of block polymers. A rapidly increasing number of publications on the synthesis and applications of SBCs have been reported in recent years; however, a systematic summary of the design, synthesis, properties and applications of SBCs has not been published. To this end, this review provides a brief overview of the recent advances in SBCs and describes the synthesis strategies, properties and functions, and their widespread applications in drug delivery, gene delivery, protein delivery, bioimaging and so on. In this review, we aim to elucidate the general concepts and structure-property relationships of SBCs, as well as their practical bioapplications, shedding further valuable insights into this emerging research field.

Tailored Polymer Particles with Ordered Network Structures in Emulsion Droplets

The structural control of block copolymer (BCP) particles, which determines their properties and utilities, is quite important. Understanding the structural relationship between solution-cast samples and polymer particles in a confined space is necessary to precisely regulate the internal structure of polymer particles. Therefore, a facile method by choosing an appropriate selective solvent is reported to prepare spherical polymer particles with ordered network structures. The rod-coil BCP, poly(dimethylsiloxane)-b-poly{2,5-bis[(4-methoxyphenyl)-oxycarbonyl]styrene} (PDMS-b-PMPCS), was chosen as a model polymer because of its strong phase segregation ability. First, the structures of the BCP with a thermodynamically stable lamellar structure cast from different selective solvents were systematically studied. Then, a polymer particle with the same internal structure as that of the solution-cast sample can be easily prepared by self-assembling in an emulsion confined space. The relatively large particle size is of importance in this process because the large value of the particle size to periodicity ratio can provide a weak confined environment. This method helps us understand the inherent self-assembling mechanism of polymer particles in an emulsion confined space and accurately control the internal structure of the polymer particle obtained.

Cooperative and Independent Effect of Modular Functionalization on Mesomorphic Performances and Microphase Separation of Well-Designed Liquid Crystalline Diblock Copolymers

Liquid crystalline block copolymers (LCBCPs) are promising for developing functional materials owing to an assembly of better functionalities. Taking advantage of differences in reactivity between alkynyl and vinyl over temperature during hydrosilylation, a series of LCBCPs with modular functionalization of the block copolymers (BCPs) are reported by independently and site-selectively attaching azobenzene moieties containing alkynyl (LC₁ ) and Si-H (LC₂ ) terminals into well-designed poly(styrene)-block-polybutadienes (PS-b-PBs) and poly(4-vinylphenyldimethylsilane)-block-polybutadienes (PVPDMS-b-PBs) produced from living anionic polymerization (LAP). By the principle of modular functionalization, it is demonstrated that mono-functionalized (PVPDMS-g-LC₁ )-b-PB and PS-b-(PB-g-LC₂ ) not only maintain independence but also have cooperative contributions to bi-functionalized (PVPDMS-g-LC₁ )-b-(PB-g-LC₂ ) in terms of mesomorphic performances and microphase separation, which is evident from differential scanning calorimetry (DSC) and polarized optical morphologies (POM) and identified by powder X-ray diffractions. With the application of the new principle of modular functionalization, local-crosslinked liquid crystalline networks (LCNs) with controlled functionality are successfully synthesized, which show well-controlled phase behaviors over molecular compositions.