For the first time, we combined orthogonal maleimide and thiol deprotections together with thiol-maleimide coupling to synthesize discrete oligomers/macromolecules on gram scale with molecular weight up to 27.4 kDa (128mer, 7.9 g) via iterative exponential growth strategy with degree of polymerization (DP) at 2^n-1. By using the same chemistry, a "readable" sequence-defined oligomer and a discrete cyclic topology were also created. Furthermore, uniform dendrons were fabricated via either sequential growth (DP =〖 2〗^n-1) or double exponential dendrimer growth approach (DP =2^(2^n )-1) with significantly accelerated growth rate. This work offered a versatile, efficient and metal-free platform for construction of discrete oligomers with vast designability and high growth rate, which would greatly facilitate sophisticated structure-property research as well as applications of precise polymer-based materials.

Combining Orthogonal Chain-End Deprotections and Thiol–Maleimide Michael Coupling: Engineering Discrete Oligomers by an Iterative Growth Strategy

Azobenzene derivatives due to their photo- and electroactive properties are an important group of compounds finding applications in diverse fields. Due to the possibility of controlling the trans–cis isomerization, azo-bearing structures are ideal building blocks for development of e.g. nanomaterials, smart polymers, molecular containers, photoswitches, and sensors. Important role play also macrocyclic compounds well known for their interesting binding properties. In this article selected macrocyclic compounds bearing azo group(s) are comprehensively described. Here, the relationship between compounds’ structure and their properties (as e.g. ability to guest complexation, supramolecular structure formation, switching and motion) is reviewed.

/pdf/azo-group-s-in-selected-macrocyclic-compounds-3zor8v9joa.pdf

Azo group(s) in selected macrocyclic compounds

The generally small Gibbs free energy difference between the Z and E isomers of hydrazone photoswitches has so far precluded their use in photon energy storing applications. Here, we report on a series of cyclic and acyclic hydrazones, which possess varied degrees of ring strain and, hence, stability of E isomers. The photoinduced isomerization and concurrent phase transition of the cyclic hydrazones from a crystalline to a liquid phase result in the storage of a large quantity of energy, comparable to that of azobenzene derivatives. We demonstrate that the macrocyclic photochrome design in combination with phase transition is a promising strategy for molecular solar thermal energy storage applications.

Photon Energy Storage in Strained Cyclic Hydrazones: Emerging Molecular Solar Thermal Energy Storage Compounds.

Macrocyclic compounds play an important role in supramolecular chemistry accounting for their unique recognition and self-assembly properties and potential applications in biomedicine and material science. Azo compounds display promising capability in fields of molecular switches, polymers, smart materials and molecular machines because of their photoactive and electroactive properties. Introducing azo groups into macrocycles gives them signal moieties, additional recognition sites, photo-responsive properties, and so on. Herein, we comprehensively review the structures of azo-containing macrocyclic compounds reported up to now. Then we describe representative works on azo macrocycles with their molecular recognition, self-assembly and application emphasized.

Macrocycles containing azo groups: recognition, assembly and application

Novel linear (AB-type), Y-shaped (AB 2 -type), and H-shaped (B 2 AB 2 -type) amphiphilic block copolymers of poly(ethylene glycol) (PEG) with polymer containing azobenzene chromophores (PAzo) were successfully synthesized by the head-to-tail acyclic diene metathesis (ADMET) polymerization. Three types of acrylate functional ADMET chain stoppers were first prepared through the Michael addition reaction and esterification. Then, a series of amphiphilic copolymers were obtained via through ADMET polymerization of azobenzene-functionalized asymmetric α,ω -diene monomer using the as-prepared PEGs with acrylate end groups as macromolecular chain stoppers. Finally, the amphiphilic copolymers could spontaneously self-assemble into spherical nanoparticles in an aqueous medium. In view of the photoresponsive blocks of PAzo, the solution photochemical properties of the solution and the sizes of these spherical aggregates can be manipulated by changing the parameters such as UV and visible lights. The differences in structure of the copolymers induced profound effects on photoresponsive performance.

Linear, Y-shaped, and H-shaped amphiphilic azobenzene copolymers: Facile synthesis and topological effect on self-assembly and photoresponsive property

Molecularly-defined macrocycles containing azobenzene main-chain oligomers: modular stepwise synthesis, chain-length and topology-dependent properties

The invention discloses a monodisperse annular azobenzene-tetraglycol copolymer A preparation method of the monodisperse annular azobenzene-tetraglycol copolymer comprises the following steps: preparing a chain extender, preparing a bromine-containing intermediate in each generation, preparing a linear copolymer intermediate and preparing an annular copolymer Compared with a polydisperse polymer obtained by adopting a traditional method, the monodisperse annular copolymer disclosed by the invention has superior optical properties and processability Besides, the copolymer disclosed by the invention has amphipathy, a photo-responsive nano material can be obtained through polymer self-assembly and can be applied to the fields of biological detection and drug controlled release, and the copolymer disclosed by the invention has broad and important potential application value

Monodisperse annular azobenzene-tetraglycol copolymer

The invention discloses a monodispersity annular azobenzene and tetraglycol copolymer and a preparation method and application thereof. The monodispersity annular azobenzene and tetraglycol copolymer has the structural formula shown as follows (please see the formula in the specification), wherein n is 1, 2, 3, 4, 5 or 6. The preparation method includes the steps of preparing a chain extender, preparing various generations of bromine-containing intermediates, preparing a linear copolymer intermediate, preparing an annular copolymer and the like. Compared with a multi-dispersity copolymer obtained through a traditional method, monodispersity annular azobenzene has outstanding optical properties and machining performance. In addition, the copolymer has amphipathy, a photosensitive nanometer material can be obtained through polymer self-assembling and is used for the field of biological detection and medicine control release, and wide and important potential application value is achieved.

Monodispersity annular azobenzene and tetraglycol copolymer and preparation method and application thereof

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Molecularly-defined macrocycles containing azobenzene main-chain oligomers: modular stepwise synthesis, chain-length and topology-dependent properties

Monodisperse annular azobenzene-tetraglycol copolymer

Monodispersity annular azobenzene and tetraglycol copolymer and preparation method and application thereof