Supramolecular Four-Armed Star A2B2 Copolymer (Miktoarm Star) via Host–Guest Complexation and Nitroxide-Mediated Radical Polymerization

Supramolecular Synthesis of Star Polymers

Supramolecular polymers, in which monomers are assembled via intermolecular interactions, have been extensively studied. The fusion of supramolecular polymers with conventional polymers has attracted the attention of many researchers. In this review article, the recent progress in the construction of supramolecular star polymers, including regular star polymers and miktoarm star polymers, is discussed. The initial sections briefly provide an overview of the conventional classification and synthesis methods for star polymers. Coordination-driven self-assembly was investigated for the supramolecular synthesis of star polymers. Star polymers with multiple polymer chains radiating from metal-organic polyhedra (MOPs) have also been described. Particular focus has been placed on the synthesis of star polymers featuring supramolecular cores formed through hydrogen-bonding-directed self-assembly. After describing the synthesis of star polymers based on host-guest complexes, the construction of miktoarm star polymers based on the molecular recognition of coordination capsules is detailed.

Preparation of Supramolecular Miktoarm Star Copolymers with a Zinc Phthalocyanine Core through ATRP and RAFT Polymerization

Topological polymers have attracted considerable attention owing to their unique chemical and physical properties. This study demonstrates the formation of novel supramolecular miktoarm star copolymers with a zinc phthalocyanine (ZnPc) core using metal-ligand coordination interactions. Various linear polymers with pyridyl end groups, poly(methyl methacrylate), poly(vinyl acetate) and poly(N-vinyl carbazole), are prepared via reversible addition-fragmentation chain transfer (RAFT) polymerization. This facilitates coordination to the ZnPc core of 4-armed star-shaped polystyrene prepared via atom-transfer radical polymerization (ATRP). Furthermore, the formation of a 1:1 complex of a ZnPc molecule and pyridyl group of the chain-transfer agent for RAFT is confirmed by absorption spectral studies and ¹ H NMR spectroscopic analyses. The concept of supramolecular complexation can be extended to the preparation of AB₄ -type supramolecular miktoarm star-shaped copolymers with functional cores.

Crown Ether-Based Supramolecular Polymers: From Synthesis to Self-Assembly

Supramolecular polymers not only possess many advantages of traditional polymers, but also have many unique characteristics. Supramolecular polymers can be constructed by self-assembly of various noncovalent interactions. Host-guest interaction, as one important type of noncovalent interactions, has been widely applied to construct supramolecular polymers. From the perspective of classification of the recognition system motifs, host-guest recognition motifs mainly include crown ether, cyclodextrin, calixarene, cucurbituril, and pillararene-based host-guest recognition pairs. Crown ethers, as the first-generation macrocyclic hosts, have played a very important part in the development of supramolecular chemistry. Due to the easy modification of crown ethers, various crown ether derivatives have been prepared by attaching some functional groups to the edges of crown ethers, which endowed them with some interesting properties and made them ideal candidates for the fabrication of supramolecular polymers. This review gives a review of the preparation of crown ether-based supramolecular polymers (CSPs) and summarizes crown ether-based recognition pairs, organization methods, topological structures, stimuli-responsiveness, and functional characteristics.

On-Site Supramolecular Adhesion to Wet and Soft Surfaces via Solvent Exchange

A series of poly(thioctic acid-catechol)s was prepared by supramolecular copolymerization of two low-molecular-weight monomers, thioctic acid (TA) and catechol (CA). The addition of a small amount of CA molecules significantly improved the adhesion ability of poly(TA) and transformed it into an applicable supramolecular polymer adhesive material. The robust adhesion of poly(TA-CA)s to soft surfaces was achieved by employing a hot-melt method. However, the supramolecular adhesion via the hot-melt method failed to perform in the presence of water. On-site supramolecular adhesion to wet and soft substrates was successfully realized through the solvent exchange behavior between water and the poly(TA-CA)s ethanol solution. Compared to the hot-melt method, the solvent exchange method displays various fascinating advantages and is suitable for adhesion conditions normally under the presence of water.

Facile Synthesis of Unimodal Polymethacrylates with Narrow Dispersity via NIR LED Light-Controlled Bromine-Iodine Transformation Reversible-Deactivation Radical Polymerization

A facile and clean strategy for synthesizing unimodal polymethacrylates with narrow dispersity (Đ < 1.10) is successfully developed by a near-infrared (NIR) light-emitting diode (LED) light (λ_max = 740 nm)-controlled in situ bromine-iodine transformation reversible-deactivation radical polymerization system without the use of NIR dyes and expensive catalysts. In this system, alkyl iodide ethyl α-iodophenylacetate (EIPA) initiator is generated in situ by the nucleophilic substitution reaction between an alkyl bromide compound ethyl α-bromophenylacetate and sodium iodide (NaI). At the same time, excessive NaI is also acted as a highly active catalyst by forming halogen bonds with terminal iodine of the polymer chains in this system to make it capable of precisely synthesizing polymethacrylates with narrow dispersities (Đ = 1.03-1.10). In addition, the strong penetration ability of NIR LED light is illustrated by the successful polymerization even through 11 pieces of A4 paper.