Design Of UCST-type Thermosensitive Polymer Catalyst And Its Catalytic Performance In Aqueous Solution

Water has been attached extensive attention as a green and environmentally friendly reaction medium in recent years.However,traditional catalysts and substrate could not dissolve in water,resulting in low catalytic efficiency and poor transfer effect.The catalysts could be difficultly separated and recovered.Based on the temperature-sensitive properties of UCST-type polymers,a series of UCST-type temperature-sensitive polymer catalysts were designed and synthesized in this dissertation.The catalyst dissolves in water and manifests as amphiphilic at high temperature?T>UCST?.The supramolecular self-assembly with a hydrophilic surface and a hydrophobic catalytic cavity can be self-assembled in water via intermolecular hydrophobic interaction,which solve limited mass transfer associated with aqueous organic reaction.After the reaction is completed,the catalyst could be precipitated from water by cooling below their UCST,and could be separated and recovered.?1?A series of thermosensitive polymer functionalized alkaline ionic liquid catalysts of P[?AAm-co-AN?_x-?N?CH₃?₂/IL?_y]were synthesized by polymerization of temperature-sensitive material poly?acrylamide-acrylonitrile??P?AAm-co-AN??with hydrophobic alkaline ionic liquid(?N?CH₃?₂/IL?using reversible addition-fragmentation chain-transfer?RAFT?polymerization.All of them exhibited upper critical solution temperature?UCST?in aqueous solution.At high temperature?T>UCST?,the catalysts dissolved in water,formed a supramolecular assembly with hydrophilic surface and hydrophobic core via intermolecular hydrophobic interaction,accelerating Knoevenagel condensation reaction in water.Quantitative conversion?98%?of 2-nitrobenzaldehyde can be basically achieved over2 mol%of the catalyst within 6 h.After the reaction was completed,the catalysts could be easily separated and recovered by reduced the temperature of water to below UCST.They were reused 5 times without significant decrease in reactivity.?2?A series of temperature-sensitive polymer functionalized Schiff base iron?III?complexes of P[?AAm-co-AN?_x-(Schiff/Fe^III)_y],which displayed UCST phase transition in water,were synthesized by coupling temperature sensitive monomer acrylamide?AAm?and acrylonitrile?AN?with hydrophobic Schiff base iron complex(Schiff/Fe^III).At high temperature?T>UCST?,the catalysts dissolved in water and formed hydrophobic cavity inside via the hydrophobic self-assembly of molecules to promote efficient sulfa-Michael addition reaction.Almost complete conversion of chalcone was achieved in 36 h over 4.5 mol%of catalyst.In addition,the catalysts could be easily recovered upon cooling to room temperature and remained catalytic activity after reused for five times.?3?Temperature-sensitive polymer functionalized Schiff base zinc?II?complexes of P[?AAm-co-AN?_x-(Schiff/Zn^II)_y],which contained P?AAm-co-AN?as hydrophilic unit and Schiff base zinc?II?complex(Schiff/Zn^II)as hydrophobic unit,were synthesized using reversible addition-fragmentation chain-transfer?RAFT?polymerization.The catalyst dissolved in water at high temperature,forming a supramolecular self-assembly with hydrophilic surface and inner cavity of hydrophobic Schiff/Zn^III complex,which accelerated the Friedel-Crafts alkylation reaction.The high conversion of?-nitrosytrene?80%?was achieved over3 mol%of the catalyst within 24 h.After the reaction,the catalysts could be recovered from aqueous systems for stable reuse by cooling to room temperature.