Fabrication Of TEMPO-Supported Nanoreactor Based On Temperature-sensitive Polymer And Its Catalytic Application

TEMPO is often used in the selective oxidation of alcohols due to its high stability,low toxicity,high catalytic efficiency and high selectivity.However,due to its high cost,in order to reduce its cost of use,TEMPO is often loaded on some heterogeneous carriers so that TEMPO can be recycled to reduce costs.Heterogeneous carriers are very convenient and quick to recycle,which is why they are widely used for recycling.However,these types of heterogeneous supports affect the dispersibility of the catalyst in the system,so that the effective collision probability of the reaction is lowered,which causes the catalytic efficiency of TEMPO to be greatly reduced.The use of the corresponding soluble carrier can solve this problem to a large extent,but the recovery of the soluble carrier has no small problem.And most of the TEMPO-catalyzed reaction systems axe water and DCM dual-phase systems,which have a greater environmental pollution.Thermosensitive polymers are a class of polymers whose properties can be abruptly changed with temperature.They are mainly classified into LCST type and UCST type.Among them,the LCST type shows that when the external temperature is lower than its transition temperature LCST,the polymer behaves as a hydrophilicity,and a homogeneous system can be formed in water,and when the external temperature rises above its transition temperature LCST,the polymer exhibits Hydrophobic,forming a heterogeneous system in water;The UCST type is just the opposite.This allows the catalyst based on the temperature-sensitive polymer to combine the high efficiency of the homogeneous catalyst and the easy recovery of the heterogeneous catalyst.In this paper,the temperature-sensitive polymer carrier with narrow molecular weight distribution was obtained by RAFT polymerization.The polymer carrier with ideal LCST was obtained by adjusting the ratio of different monomers in the polymer,and then the TEMPO was loaded by "click" chemistry.The selective oxidation performance of the prepared catalyst to alochol was investigated,and the catalyst,its catalytic effect and recovery effect were characterized by NMR,GPC,EPR,UV-Vis,GC-MS.It was found that the prepared catalyst has excellent catalytic performance regardless of whether the substrate is an aromatic alcohol or a fatty alcohol,and maintains high selectivity(about 99%);it has a very good catalytic effect(Tof:80 h-1).And it is reused six times,no effect on the catalytic effect,the catalyst loss is only 3.07%per recycling.In order to make the reaction more efficient and green,we prepared micellar nanoreactors with the prepared amphiphilic temperature-sensitive polymer as a surfactant,and found that its particle size is about 530 nm.After the study of water relative to its catalytic properties.It was found to have excellent catalytic properties,and the alcohols with more complex structure and higher steric hindrance could be completely selectively oxidized within 20 min.At the same time,its catalytic rate Tof increased to 960 h-1,while the amount of catalyst decreased by 50%.These catalysts were slightly reduced until the seventh effect(from 99%to 92%),and each reuse loss was only 4.3%.In addition,in order to further improve the utilization of TEMPO and the stability of the nanoreactor,a kind of self-assembled nanoreactor and single-molecule nanoreactor were prepared based on temperature-sensitive polymers.It was found that the self-assembled nanoreactor has a more excellent effect on the reaction in the aqueous phase,which shortens the reaction time to about 5 min,increases the Tof value to 9600 h-1,reduces the catalyst amount to the initial 10%,and has a ratio Micellar type more uniform particle size distribution;The single-molecule nanoreactor has a very rapid catalytic rate in the aqueous phase,the reaction time is shortened to 1 min,and the Tof value rises to 1.92 ×105 h-1,which is 300 to tens of thousands times higher than that of the heterogeneous catalyst.The catalyst usage was only an initial 2.5%.And it has better stability,and its particle size does not change greatly when the concentration changes by 60 times.At the same time,both types of catalysts also have excellent recyclability.