Study On Synthesis, Property And Layer-by-layer Self-assembly Of Polyvinylamine

Polyacrylamide (PAM), poly(N-vinylformamide) (PNVF) and polyvinylamine (PVAm) are water-soluble polyelectrolyte. With a large number of side functional amido groups, amino groups and high reactivity, they have many special features. So they are significance in the technology as well as practical applications. The main contents of the thesis are as follows:1. Synthesis of PAM. PAM was synthesized by aqueous solution polymerization using acrylamide (AM) as monomer, ammonium persulfate and sodium bisulfite as redox initiators. The structure, properties and weight-average molecular weight (Mw) of the polymers were studied by Fourier transform infrared spectrometer (FT-IR), X-ray diffraction (XRD), multi-detector gel permeation chromatography (GPC), differential scanning calorimeter (DSC) and thermogravimetric analyzer (TGA), respectively. The effects of mass fraction of monomer, initiator and chain-transfer agent as well as polymerization temperature on monomer conversion and Mw of PAM were researched. The synthesis of PAM was confirmed by disappearance of the absorption peak of carbon-carbon double bond at 998 cm^-1 in the FTIR spectrum. The thermal decomposition of PAM proceeded in three stages. Glass transition temperature (Tg) of PAM increased with increasing of Mw of PAM. Monomer conversion increased with increasing polymerization temperature and mass fraction of monomer or initiator. Mw of PAM decreased with increasing polymerization temperature or mass fraction of initiator and chain-transfer agent, and with decreasing the mass fraction of monomer.2. Synthesis of PVAm. PVAm and polyvinylamine hydrochloride (PVAm·HCl) were synthesized by Hofmann degradation of PAM. Meanwhile, PNVF was synthesized by aqueous solution polymerization with N-vinylformamide (NVF) as monomer and 2,2'-azobis(2-methylpropionamidine) dihydrochloride (AIBA) as initiator. Then PVAm and PVAm·HCl were synthesized by alkaline or acidic hydrolysis of PNVF. In the experiment of Hofmann degradation, the chemical structures and thermal properties of the polymers were studied by FT-IR, nuclear magnetic resonance spectrometer (NMR), XRD, DSC and TGA. Synthesis of PVAm·HCl was confirmed by the intensities of the characteristic peak at 1530 cm^-1 (due to N-H bond of -NH3+) and intensities of the characteristic peak at 1665 cm^-1(due to C=O bond of -CONH2) were weak than those of the characteristic peak of PAM in the FT-IR spectrum. The characteristic absorption peaks of carbon atoms were appeared atδ35.46 ppm (-CH₂-),δ48.63 ppm (-CH-),δ178.33 ppm (-CONH2) in the 13C-NMR spectrum. The chemical shifts of proton were appeared atδ1.87 ppm (-CH₂-),δ3.54 ppm (-CH-) in 1H-NMR spectrum, respectively. PVAm·HCl had two decomposing stages. TG curves of PAM and PVAm·HCl showed the initial decomposition temperature were 190 oC and 140 oC, respectively. The thermal stability of PVAm·HCl was poorer than that of PAM. The degradation rate (a) decreased with increasing Mw of PAM and decreasing amount of NaOH, and a was the better value when the concentration of PAM was 5 % and the amount of NaClO was 10 mL. DSC curves showed that Tg of PVAm·HCl increased with increasing Mw of PAM, concentration of NaClO and decreasing concentration of NaOH. Tg of PVAm·HCl appeared the minimum value when the concentration of PAM was 5.0 %. In the experiment of hydrolysis reaction of PNVF, the chemical structures of PNVF and PVAm·HCl and the Mw of PNVF were studied by FT-IR, NMR and GPC. The reaction of PNVF by the alkaline hydrolysis was more completely than that of by the acid hydrolysis according to the NMR spectrum. The degradation rate increased with increasing the mass fraction of initiator, while the Mw of PNVF decreased with increasing the mass fraction of initiator.3. Study on layer-by-layer (LbL) self-assembly of PVAm and polyacrylic acid (PAA). A stable and covalent bond-linked multilayer film was formed using the LbL self-assembly of PVAm and PAA. The reaction process could be conveniently monitored by testing of ultraviolet and visible (UV-Vis) absorption spectroscopy. The absorbance of amido group of the LbL film increased with increasing the number of layers, assembly time, molar concentration of PAA and PVAm. A good linear relationship between absorbance and the layer number was observed, which was an indication of a progressive alternate reaction of PVAm and PAA. In PVAm-PAA system, the reaction between PVAm and PAA was confirmed by FTIR spectroscopy. FTIR spectra of multilayer assembly films showed the characteristic peak of amido bond. The result clearly manifested the amido group between the reaction of amino group and carboxyl group during the alternate reaction process. From atomic force microscopy measurement, the polymer film structure of multilayer films on silicon wafer was observed.