DNA from E. coli to a cyclic polymer ring! Cyclic polymer synthesis, properties and application prospects
Cyclic polymers based polymer material having a cyclic structure and no end groups. Because of its unique topology, as compared with a common linear or branched polymers, cyclic polymers exhibit unique properties, for example, a smaller hydrodynamic volume, a slower degradation rate, stability, and better than high glass transition temperature and the like. The last two decades, people to develop a high purity cyclic polymer synthesis, and reveal the relationship between the topology and physical properties of the cyclic polymer. By using the \”click\” of the new and efficient reaction between the catalyst or terminal groups bond to form a cyclic method is to adjust the physical properties of the polymer provides a new way. For example, the Food and Drug Administration approved a polyester having good pharmacokinetics, biocompatible and biodegradable, and cyclic analogs corresponding thereto while maintaining the original characteristics, which can be adjusted solubility, crystallinity and degradation.
Recently, Tulane University Professor Scott M. Grayson in \” Nature Chemistry \” published an article entitled \”The synthesis, properties and potential applications of cyclic polymers \”(DOI: 10.1038 / s41557-020-0440-5) promising future review paper, the primary system to review the preparation of cyclic polymers and basic physical properties, and cyclic polymer the key prospected. 
1 found and cyclic polymer synthesis
In 1958, Jacob and Wollman first proposed the concept cyclic polymer, and E. coli was confirmed by electron microscopy DNA is a cyclic structure. Subsequently, it was discovered that a wide variety of cyclic biological macromolecules, including peptides and cyclic macrolide like, and note that these unique molecules annular ring structure gives good stability and its strong intramolecular interaction. Inspired, in order to prepare cyclic polymers and study its physical properties, scientists have for the first time throughThe method of byproducts of the polycondensation reaction through the first cyclic oligomeric polymers prepared. In the past 60 years, a clear and controllable size of the polymer preparation process ring topology has made great progress, including bimolecular closed loop method, a single molecule and closed-loop method to expand the Tour de France. Bimolecular loop method is based on coupling reaction bifunctional polymer with a difunctional coupling occurs, commonly used in the anionic polymerization of vinyl monomers. Loop method is a single molecule in a dilute solution under conditions to achieve linear polymers to each other by the coupling ends of the polymer chain cyclization. Ring expansion method is a catalyst or agent continuously generated in a manner cyclic monomer insertion cyclic polymer, commonly used in cyclic olefins, lactones, lactides and heterocyclic anhydrides cyclic monomer to initiator.
2. The physical properties of the polymer and the cyclic potential industrial applications
Numerous studies have shown that cyclic polymers exhibit unique physical properties of the main from its own ring topology. Kricheldorf et al found that, compared to the linear analogue, due to the conformation of the cyclic polymer is constrained so as to exhibit a lower hydrodynamic radius and a longer retention time. This feature not only be used to distinguish the ring and linear polymers, even product was purified by preparative gel permeation chromatography (GPC). On the other hand, due to the lack of end group affects the flowability of the polymer segment and interactions, cyclic polymers exhibit high glass transition temperature, therefore, the glass transition temperature by controlling cyclic polymer, can the polymer film which is used in industry. In addition, the rheological properties of the ring are quite different linear polymers, useful as viscosity modifiers composite. It found that small amounts of low molecular weight polymer doped ring of high molecular weight polymers, can be adjusted and thermal properties of the viscoelastic synthetic homopolymer mixture. Moreover, cyclic polymers dopant while improving the overall physical properties and processing properties of commercial materials, but also to avoid the small molecular additive often suffer from leaching doped shortened product life and cause environmental pollution problems.
3. Biological properties and biomedical applications cyclic polymer
cyclic block copolymer can be assembled to form a moreSmall, high stability micelles, having long residence high osmotic effect in the transmission based micelles entrapped pharmaceutical process provides a good carrier material for drug delivery. In addition, studies have shown that biological macromolecular topology for gene transfer plays an important role. These preliminary findings indicate a cyclic polymers range of potential biomedical applications.
4. Cyclic polymer future research priorities
In a review of the progress of the study, the authors future research priorities cyclic polymer and challenges a comprehensive exposition. From an industrial point of view, to find an effective way to obtain high purity of the sample and the development of mass production of cyclic polymer synthesis process is further developed into a key commercial research materials. We must address three critical problems in the evaluation and optimization of purity cyclic polymer: A quantitative cyclic product, post-processing structure and qualitatively valid acyclic acyclic byproducts byproducts. In this review, the authors of the cyclic polymer synthesis of theoretical research related to the physical and biological properties of the system were introduced, pointing out that the basis for future cyclic polymer to further improve performance and achieve commercialization. The review has a certain significance for in-depth study of application development and diversification of the industrial potential of the biomedical field cyclic polymer functional materials and so on.
