Synthesis And Characterization Of Fluoroacrylate/Acrylate Copolymer Latex In Dispersed Phase Systems

Many important properties of solid material are dependent on the surface chemical structure and atomic composition. Polymers containing perfluorinated alkyl side chains have attracted much attention due to their unique properties, such as high chemical and thermal stability, outstanding antiadhesive and oil-repellent properties, low refractive index and low dielectric constant. Therefore, fluoropolymers are used prevalently in the textile, coatings and carpet industries. Further applications include nonstick cookware, car finishes, aviation field, disk drives and waveguide devices. Low surface energy is a key property of these polymers which prevents sticking/adhesion, polymer blending and degradation. Perfluoroalkyl substituted acrylates copolymer have emerged as the most widely used low surface energy polymer coatings of substrates such as textiles, paper, leather and wood, due to the fact that their presence may introduce a number of unique surface physical and chemical properties. Based on the reinforcing of people's resource and environmental awareness, how to synthesize fluorinated copolymer emulsion with anticipated macromolecular structure and properties in dispersed phase systems has become a challenge to chemical prosess and product engineering. But the relatively high market prices of the fluorinated monomers limit their use, researchers always hope to exploit possible polymerization strategy, by doing so, it is anticipated that excellent properties can be preserved while the amount of fluorinated compounds required in the polymer is reduced considerably.Base on the design of molecule constructure and nanolatices morphology, the synthesis, properties and characterization of fluorinated acrylate copolymers were studied in detail, from the macromolecular chain composition, submicro morphology of latices and self-assemble structure of copolymer aggregation. Stable fluorocopolymer emulsion with anticipated macromolecular composition and nanoparticle structure were prepared via miniemulsion polymerization, core-shell emulsion polymerization and living/controlled radical polymerization in dispersed phase system. A complete characterization methods were set up to investigate the structure and the properties of fluorocopolymer emulsion. Nuclear magnetic resonance spectroscopy(H-NMR), fourier transform infrared spectroscopy(FT-IR), dynamic light scattering(DLS), transmission electron microscopy(TEM), gel permeation chromatography(GPC), x-ray photoelectron spectroscopy(XPS),differential scanning calorimetry(DSC) and contact angle measurer were used to characterizate the structure and properties of the prepared copolymer emulsion containing fluorine, and the reaction kinetics of these three kinds of heterogenerous polymerization in aqueous media were studied.Fluoroacrylate copolymer stable emulsion in the size range of 110-150nm were made by miniemulsion polymerization under employment of low dose of emulsifiers, with fluoroacrylate (FA), butyl methylacrylate (BMA), methyl methylacrylate (MMA) as monomers, the molecular weight and composition of copolymer had been demonstrated by GPC, FT-IR and H-NMR, the change of latex partical sizer in polymerization process was determined, and the surface property of films was studied by Wilhelmy method, It is show that mixed monomer species allows efficient copolymerization, products with high conversion of fiuoromonomer (95% ), copolymer particles were found to be one-to-one copy of the monomer droplets and drop nucleation was the dominant mechanism in polymerization process. The average composition of the copolymer prepared by miniemulsion was found to be in good agreement with the feed ratio using ¹H-NMR from the integration ratios corresponding to typical protons of individual monomers. The effects of various reaction parameters on the miniemulsion polymerization were also investigated. These parameters mainly include the temperature, concentration of emulsifier, 2,2'-azobisisobutyronitrile ([AIBN]) and fluorinated monomer. The polymerization rate and conversion increases with increasing emulsifiers ([NP-40], [C₁₆TAB]) and initiator [AIBN].The surface composition and properties of copolymer miniemulsion containing fluoroacrylate were studied by means of X-ray photoelectron spectroscopy(XPS) and contact angle measurement, and the surface energies of those copolymer films were evaluated by the harmonic mean equation, It was shown that the surfaces of the copolymers were very hydrophobic (even with a small amount of FA) because of the concentration of FA segments at the surface. The surface free energies of copolymer films decrease drastically with increasing the concentration of FA, and can reach 11.6mN/m when the molar concentration of FA used in copolymerization increases to 17.54 wt%. The atomic compositions and surface segregation of the fluorinated component as a function of depth of fluorocopolymer thick films were investigate by angle-dependent XPS. It was found that the content of fluorine on the surface of copolymers is higher than the value calculated according to the feeds. Our investigation verified that groups containing fluorine tend to enrich at the copolymerair interface. This surface segregation is enhanced when the samples are thermally annealed, which resulted in further decrease of surface free energies. The results indicated that the surface properties of fluorocopolymer synthesized by miniemulsion were excellent under employment of low dose of emulsifiers and no coemulsifiers.Core-shell latex with acrylate copolymer rich in core and fluoroacrylate copolymer rich in shell was prepared by seeded semi-continuous emulsion polymerization in the presence of mixed emulsifiers, with a redox initiator ((NH₄)₂S₂O₈/NaHSO₃) at lower temperature. The functional reactive monomer glycidyl methacrylate (GMA) and 2-hydroxyethyl acrylate(HEA)/acrylic acid(AA) were respectively localized in the core layer and shell layer of the core-shell latex particles, which containing carboxyl groups on the shell layer and epoxy group on the core performed self-crosslinking at ambient temperature. The latex particles exhibited narrow polydispersity with number-average diameter of 100 nm with nonioc and ionic composite emulsifiers. The polymerization conditions for the latex were discussed. The stability of semi-continuous polymerization is the best when the polymerization temperature was at 40℃. The structure and morphology of latex particles was characterized by transmission electron microscopy and FTIR. The surface properties of the latex films produced from the core-shell particles were investigated by the contact angle method. Compared with random copolymers, the core-shell particles were the most effective to reduce the surface energy of the latex films, as a result, the physical and chemical performance of latex films are improved.Reversible addition fragmentation chain transfer(RAFT) miniemulsion polymerization of butyl methacrylate(BMA) and dodecafluoroheptyl methacrylate (DFMA) was carried out in this study with 2-cyanoprop-2-yl dithiobenzoate(CPDB) as chain transfer agent(CTA). Concentration effects of RAFT agent and initiator on kinetics and Mn were investigated, when the surfactant(mass ratio: SDS/OP-10=2/1) concentration used in this work was 3 wt % of monomer, and costabilizer (HD) was 4 wt%, no obvious red oil layer (phases separation) and coagulation was observed in the homopolymerization of BMA with the molar ratio of monomers/CTA between 63 to 200. The polymer molecular weights increased linearly with the monomer conversion with polydispersities lower than 1.2. At 75℃, the monomer conversion could get above 96% in 3 hours with [M]:[RAFT]:[KPS]=620:4:1. The results showed excellent controlled/living polymerization characteristics and a very fast polymerization rate. But if the ratio of [M]/[RAFT] lower than 50/1, super-swelling, along with the subsequent destabilization and phase separation, which would lead to formation of ared layer, will happen. This phenomenon(super-swelling) can be weakened, or be prevent from occurring, with high surfactant concentrations and high levels of hexadecane. Furthermore, the synthesis of high molecular weight PBMA with a regular structure(PDI<1.35, PMMA calibration) were performed by adding BMA monomer at the end of the RAFT miniemulsion polymerization.RAFT miniemulsion copolymerization of butyl methacrylate(BMA) and dodecafluoroheptyl methacrylate (DFMA) was carried out in this study with 2-cyanoprop-2-yl dithiobenzoate(CPDB) as chain transfer agent(CTA). CPDB appears to be a good candidate in the RAFT copolymerization of DFMA and BMA, and the results showed excellent living/controlled polymerization characteristics. Synthesis of P(BMA-b-DFMA) diblock copolymers with a regular structure(PDI<1.30, PMMA calibration) were performed by adding DFMA monomer at the end of the RAFT miniemulsion polymerization of BMA, and the PBMA macro CTA was confirmed to be a good mediate function in block polymerization. The molecular weight of copolymer increased compared with that of the first block, and the GPC profiles of copolymer remained single modal molecular weight distribution. The polymers exhibited a phase-separated morphology and exhibited distinct glass transition temperatures associated with fluoropolymer PDFMA and PBMA domains.