Light-controlled shape-changing azomacrocycles exhibiting reversible modulation of pyrene fluorescence emission

We report the design, synthesis, and study of light-induced shape-changing azomacrocycles. These systems have been incorporated with azobenzene photoswitches using alkoxy tethers and triazole units to afford flexibility and binding. We envision that such azomacrocycles are capable of reversibly binding with the guest molecule. Remarkably, we have demonstrated fully light-controlled fluorescence quenching and enhancement in the monomeric emission of pyrene (guest). Such modulations have been achieved by the photoisomerization of the azomacrocycle and, in turn, host-guest interactions. Also, the azomacrocycles tend to aggregate and can also be controlled by light or heat. We uncovered such phenomena using spectroscopic, microscopic, and isothermal titration calorimetry (ITC) studies and computations.

Facile synthesis of monocyclic, dumbbell-shaped and jellyfish-like copolymers using a telechelic multisite hexablock copolymer

A heterofunctional hexablock copolymer comprising alternating reactive and non-reactive blocks is designed to generate cyclic, dumbbell-shaped and jellyfish-like copolymers.

Topology-directed multi-tunable self-assembly of linear and tadpole-shaped amorphous-responsive-crystalline terpolymers

Rational design of ABC linear terpolymer and (c-AB)C tadpole-shaped terpolymer allows the construction of a topology-directed crystallization/thermo/pH-tunable hierarchical self-assembly platform.

Precision Aliphatic Polyesters via Cross-Metathesis Polymerization

Cross-metathesis (CM), a carbon-carbon bond transformation that features exceptional selectivity, reactivity and tolerance to functionalities, has been extensively investigated in organic chemistry. On the other hand, the use of CM in polymer synthesis is also growing in both scope and breadth, thus offering a wealth of opportunities for introducing a vast range of functionalities into polymer backbone so as to manipulate properties and expand applications. In this review, we propose the concept of "cross-metathesis polymerization" (CMP) referring to polymer synthesis via repetitive CM reaction and summarize emerging strategies for the precision synthesis of aliphatic polyesters via CMP based on the high CM tendency between acrylates and α- olefins. Due to the carbon-carbon bond-forming step-growth polymerization nature, CMP brings a new concept to polyester synthesis. This remarkable polymerization method possesses unique advantages such as mild condition, full conversion, fast kinetics, almost quantitative yield and extraordinary tolerance to functionalities. In particular, CMP provides the ability to regulate macromolecular architectures including linear, block, cyclic, star, graft, dendron, hyperbranched and dendrimer topologies. Ultimately, advanced polymeric materials with outstanding performances can be facially constructed based on these sophisticated macromolecular architectures.

Hyperbranched Aliphatic Polyester via Cross-Metathesis Polymerization: Synthesis and Postpolymerization Modification

A novel postpolymerization modification methodology is demonstrated to achieve selective functionalization of hyperbranched polymer (HBP). Terminal and internal acrylates of HBP derived from cross-metathesis polymerization (CMP) are functionalized in a chemoselective fashion using the thiol-Michael chemistries. Model reactions between different thiols (benzyl mercaptan and methyl thioglycolate) and acrylates (n-hexyl acrylate and ethyl trans-2-decenoate) by using dimethylphenylphosphine or amylamine as the catalyst are investigated to optimize the modification protocol for HBP. High-molecular-weight HBP P0 is generated through CMP of AB₂ monomer 2, a compound containing one α-olefin and two acrylate metathetically polymerizable groups. CMP kinetics is monitored by NMR and gel permeation chromatography (GPC). Accordingly, microstructural analysis is conducted in detail, and CMP procedure is optimized. Postpolymerization modification of HBP P0 is performed via two distinguished strategies, namely one-step complete modification and sequential modification, to generate terminally and/or internally functionalized HBPs P1-P3 in a chemoselective fashion by using phosphine-initiated and/or base-catalyzed thiol-Michael chemistries. Finally, thermal stability and glass transition behaviors of HBPs P0-P3 are studied by thermal gravimetric analysis (TGA) and differential scanning calorimetry (DSC), respectively.