Synthesis And Application Of Star Polymer-Based Catalyst

Enzymes play an important role in life.It is of great significance to use a macromolecular backbones or protein backbones to protect the metal catalytic center,forming a macromolecular enzyme-like structure or artificial metalloenzyme.Common macromolecules that can be used to load functional groups,mimic biological enzymes including proteins,single-chain nanoparticles,star polymers,dendrimers,helical polymers,micelles,vesicles,and macrocyclic compounds.Based on the previous work,a dense-shell nanoparticle(DSNP)was synthesized.The scaffold can load metal ions,and the formed metal-catalyzed nanoparticles can not only carry out efficient catalytic reactions in vitro,but also catalysis of spatial positioning in a cellular environment.This article describes a polymerization-crosslinking method to conveniently synthesize a DSNP macromolecular framework with a dense shell structure.The periphery dense shell and the inner star-shaped polymer scaffold with hydrophobic core can be easily synthesized by the tri-triazole ligand mediated polymerization crosslinking process.First,the ring-opening metathesis polymerization(ROMP)method is used to synthesize a chain polymer with an active center at the end,and then the synthetic trimeric triazole ligand cross-linking agent(TBTA derivative)was added to go further ROMP crosslinking and form a star.The star-shaped polymer DSNP is finally quaternized with n-butylimidazole to form a spherical DSNP structure with a diameter of about 100 nm.These DSNP frameworks have a narrow dispersity,a uniform structure,and good water solubility.The DSNP obtained by the above method have a dense polymer shell,which can protect the metal catalytic centers in the core.These catalytic centers are formed by the chelation of the trimeric triazole ligand and the metal ions.Introducing different metal ions into the DSNP scaffold to obtain metal nanoparticles which can catalyze different reactions.Taking copper and palladium catalysts as examples,the formed nanoparticle catalyst can catalyze the click reaction and the deprotection reaction of propargyl carbamate,respectively.The catalytic alkyne and azide click reaction has a very good catalytic efficiency and high conversion number,showing the characteristics of enzyme catalysis.The catalytic deprotection of propargyl carbamate also has a good catalytic efficiency.A series of studies have shown that DSNP can stabilize the metal ions therein,making them less prone to reactions other than catalysis,thereby increasing the conversion number of the catalyst and reducing the loss of metal ions.The DSNP scaffolds not only protect and stabilize the catalytic center,more importantly,they can locate the chemical reaction.When the substrate is incubated for a short time,the reaction products are mainly concentrated on the cell membrane,while the intracellular are less products.If the reaction time for a prolonged time,the product gradually penetrates into the cytoplasm,which can show the targeting effect according to the characteristics of the product.The final positioning of the product depends on the structural characteristics of the catalyst and substrate,as well as the incubation time and diffusion rate.This process is essentially a " space-time " control of the catalytic reaction,and it is possible for cell membrane targeted catalysis without anchoring the substrate in advance.