Synthesis, Characterization And Self-Assembly Behavior Of Novel Fluorinated Amphiphilic Random Copolymers

There are three parts included in this thesis research:(1) synthesis of a series of amphiphilic cationic random copolymers,measurement of reactivity ratios between the two monomers and research the self-assembly behavior in water and water-ethanol mixtures;(2) synthesis of a series of amphiphilic fluorinated random copolymers with pH/temperature response and research the self-assembly behavior in aqueous solution of various pH values;(3) synthesis of a series of pH-responsive cationic microgels and research the pH-responsive behavior.(1) Synthesis of Amphiphilic Cationic Copolymers and Their Self-Assembly Behavior in Water and Water-Ethanol MixturesIn this part,a series of amphiphilic cationic random copolymers,namely poly[2-(methacryloyloxy)ethyl trimethylammonium chloride-co-stearyl methacrylate] or poly(MADQUAT-co-SMA),have been synthesized via conventional flee-radical copolymerization using 2,2'-azobisisobutyronitrile(AIBN) as initiator and n-dodecanethiol as chain transfer agent.The resultant products were then characterized by FT-IR,¹H NMR,MALDI-TOF MS measurements.The reactivity ratios(r_MADQUAT= 0.83,r_SMA=0.25) between the hydrophilic monomer MADQUAT and the hydrophobic monomer SMA were calculated by the Finemann and Ross method,which was based on the results of ¹H NMR analysis.The surface activity of the random copolymers was studied by the combination of surface tension and contact angle measurement.The critical aggregation concentrations(cac) of the copolymers in aqueous solution were determined by fluorescence probe method,electrical conductivity and surface tension measurement.Furthermore,using transmission electron microscopy(TEM),we could observe the self-assembly morphology of these random copolymer.All the results show that amphiphilic cationic random copolymers have a good self-assembly behavior in water and water-ethanol mixtures,even if they are ill-defined copolymers.(2) Study on Novel Amphiphilic Fluorinated Random Copolymers with pH/Temperature Response and Their Self-Assembly Behavior A series of studies on amphiphilic fluorinated random copolymers with pH/temperature response were herein described,wherein the copolymers,poly[1H,1H, 7H-dodecafluoroheptyl methacrylate-co-2-(N,N-dimethylamino)ethyl methacrylate]or poly(DFMA-co-DMAEMA),were synthesized via conventional free radical polymerization using 2,2'-azobisisobutyronitrile(AIBN) as initiator,and then characterized by FT-IR,¹H NMR,¹⁹F NMR,and gel permeation chromatography(GPC) technique.The thermal stability of the copolymers was examined by thermogravimetric analysis(TGA).The aqueous solution behaviour of the copolymers was investigated by the combination of surface tension,electrical conductivity,fluorescence probe,cloud point and contact-angle measurement.The results indicate that the copolymers exhibit distinct pH/temperature-response properties and possess high surface activity.The critical aggregate concentration(cac) of the copolymers in aqueous solution decreases with the increase of hydrophobic DFMA segments.The self-assembly behaviour was studied by TEM analysis and ¹H NMR spectroscopy.A very interesting phenomenon was found that the aggregate morphologies changed as a function of the pH values of the aqueous solution.The mechanism of the self-assembly behavior was discussed.(3) Synthesis and Properties of pH-Responsive Cationic MicrogelsA series of pH-responsive cationic microgels have been synthesized via semi-continuous emulsion polymerization with 2-(N,N-dimethylamino)ethyl methacrylate(DMAEMA) and ethyl acrylate(EA) as comonomers,and ethylene glycol dimethacrylate as cross-linker.The effects of various conditions on the emulsion polymerization and the stability of microgels were studied in detail.The resultant microgels were characterized by transmission electron microscopy(TEM),dynamic light scattering(DLS) and rheometry.The pH-responsive behavior of the microgels was investigated by the measurements of Z-average diameter,zeta potentials,and the solution transmittance of the microgels at different pH values.Furthermore,the influence of NaCl solution on the stability of the microgels in aqueous solution was also studied.All the results show that the cationic mircrogels possess well pH-responsive property,and the phase variation happens at pH 7.0.Furthermore,the addition of NaCl solution can influence the stability of the microgels and the critical flocculent concention is about 1.3 g L^-1.