JACS publishes the research results of Professor Sun Xiaolong, Xi'an Jiaotong University: a new functional polymer for topological structure transformation and chemical degradation

How to realize the controllable function and chemical degradation of polymer is an important subject in materials, chemistry, environment and other sciences The main factors affecting the physical properties of polymers are molecular weight distribution, viscosity, topological structure, chemical function and crosslinking density For most polymers, it is difficult to change the properties of the polymer by changing the bonding mode of the main chain structure and the function of the cross-linking group, because the chemical bonding mode and the topological structure are static Stimulus responsive polymer functional materials have attracted more and more attention in many fields, such as chemical materials, biomedicine and manufacturing, because they can respond to external signals by adjusting their structures when they are stimulated by specific external stimuli However, at present, their modification is limited to a single exchange of chemical functional groups, which results in very limited changes in their topological structure and morphology In order to better solve the above problems, Professor Sun Xiaolong of Xi'an Jiaotong University, together with Professor Eric Anslyn and assistant professor Nathaniel Lynd of University of Texas Austin, developed a new type of soft material functional material through "click chemistry" and "click chemistry" reactions, using reversible chemical covalent bonding and mercapto group- The conversion of disulfide bonds realizes the regulation of macromolecular structure and properties, the remolding of topological structure and chemical degradation The overall regulation of the structure and function of the macromolecular materials developed and synthesized is realized by the chemical reaction of the small molecular link group, and the chemical reversible covalent bonding / coupling is respectively realized by the substitution reaction of amine / sulfhydryl group on the conjugated molecular acceptor; oxidation-reduction promotes the dynamic exchange of disulfide bond; the cyclization reaction of conjugated acceptor initiated by the small molecular reagent realizes the degradation (Fig 1) At the same time, different types of reversible dynamic covalent bonds exist in hydrogel materials, which can regulate the morphology and mechanical properties of polymers by different chemical initiation With the help of "click-declick" chemical reaction, polymer materials with biodegradability have been successfully prepared Figure 1 Reaction diagram of "click chemistry" and "click chemistry" of small molecules (source: J Am Chem Soc.) the authors successfully prepared hydrophilic / hydrophobic linear polymers, mild crosslinked polymers and network structure hydrogels by copper catalyzed alkyne azide click chemistry reaction (Fig 2) Followed by amino mercapto substitution, mercapto- By simply controlling the addition sequence of monomers, crosslinkers or polymers, and by chemical reaction at room temperature, the main chain structure and crosslinkers can be transformed into new linear amphiphilic, light crosslinked, network crosslinked polymers and different mechanical properties of the polymers Glue The process of chemical reaction and structural transformation were tested and tracked by UV VIS spectrophotometer, nuclear magnetic resonance spectrometer, gel permeation chromatography, dynamic light scattering instrument and rheometer Figure 2 Schematic diagram of polymer synthesis and topological change (source: J am Chem SOC.) before and after the topological structure transformation, the polymer materials developed and synthesized above can be degraded and release small molecular compounds by adding DTT under the neutral buffer condition with simple declick reaction For the double network soft material, by adding different chemical reagents, it can realize the function regulation and step-by-step degradation Figure 3 Schematic diagram of polymer degradation initiated by DTT molecule (source: J am Chem SOC.) All the polymers and hydrogel matrix involved in the project are carried out by adding new monomers, crosslinking agents, polymers or oxidants at normal temperature and neutral conditions The products are all adjustable and degradable, especially in physiological conditions, and the properties of dynamic crosslinking bonds can be predicted The above materials will be predicted in the drug delivery system, cell encapsulation and cell migration It has a wide application prospect in the field of migration and biological tissue engineering The above cooperation achievements were published by Journal of the American Chemical Society (DOI: 10.1021 / JACS 9b12122), an authoritative journal in the field of international chemistry and materials, under the title of "chemical triggered synthesis, removing, and graduation of soft materials" Professor Sun Xiaolong is the first author of the paper, and the school of life science and technology of Xi'an Jiaotong University is the first unit This is also the fifth high-level journal paper published by the research group since its establishment This work was supported by the National Natural Science Foundation youth program (21907080), Xi'an Jiaotong University Youth top talent class a program (2019kfyrcpy089), team and talent support - Youth tracking class B basic business fee (xtr042019010) Introduction of the research group: the research group of Professor Sun Xiaolong, School of life, Xi'an Jiaotong University is committed to the research of molecular recognition and fluorescence sensing and the development and application of soft material functional materials In recent years, some experience has been accumulated in the development and application of fluorescence sensing technology based on molecular recognition to recognize glucose and reactive oxygen species; the development and application of fluorescence signal cascade amplification system; the development and application of soft material functional materials based on dynamic covalent bond The research results were published in Chem Rev., NAT Chem., J am Chem SOC (3), angel Chem Int ed, ACS center SCI., chem SCI (3) and other academic journals.