Temperature-sensitivity Property Of Fluorinated Gradient Copolymer Micelles

Amphiphilic gradient copolymers vary their monomer composition from hydrophilic units to hydrophobic units gradually along molecular chains.This‘doping property’makes gradient copolymers different from block copolymers,especially in self-assembly behavior.Amphiphilic gradient copolymer assemblies show special and more sensitive response to solution conditions.In this thesis,two amphiphilic gradient copolymers and one block copolymer were prepared by reversible addition-fragmentation chain transfer（RAFT）polymerization.Acrylic acid（AA）and 2,2,2-trifluoroethyl methacrylate（TFEMA）were used as hydrophilic monomer and hydrophobic monomer respectively.The conversion and ¹H NMR results of tracking samples showed that three copolymers had a similar monomer composition and molecular weight but different monomer distributions along molecular chains.The self-assembly of three amphiphilic copolymers were implemented by selective solvent intruding method and deionized water was used as selective solvent.DLS and TEM studies showed that aggregates of two gradient copolymers presented a temperature-sensitive property in different pH values of solutions.When temperature rose,the size of those aggregates reduced.This temperature-sensitive property had obvious pH dependence,and enhanced with an increasing pH.Block copolymer did not presented such temperature-sensitive property.At last,the prepared aggregates of three amphiphilic copolymer were used as templates to prepare amphiphilic copolymer/nano-Ag compound micelles by in situ reduction method.AgNO₃ and NaBH₄ were used as silver source and reducing agent.Compound micelles before reduction and after reduction were respectively studied in three pH conditions by DLS technology to investigate their temperature-sensitivity.The results showed that compound micelles before reduction and after reduction presented temperature-sensitive property in different pH conditions.When temperature increased,the average size of those compound micelles decreased.The temperature-sensitive property of those compound micelles had not obvious pH dependence.The pH had scarce effects on temperature-sensitive property of compound micelles,when the high concentration of Ag irons was used during preparing compound micelles.