Study On Synthesis, Property And Layer-by-layer Self-assembly Of Poly(allylamine Hydrochloride)

Layer-by-layer (LbL) self-assembly is a technique of preparing supermolecular structure, which is based on ions interaction between positive and negative charge of polyelectrolyte. Polyallylamine and poly(p-aminostyrene) (PPAS) are water-soluble polyelectrolyte containing amino group in the side chain. The amido bond was formed between the reaction of amino group of polyallylamine or PPAS and carboxyl group of poly(acrylic acid) (PAA). LbL self-assembly was carried out between polyallylamine, PPAS and PAA by the formation of amido bond using as driving force. The main contents of this thesis were as follows:1. The synthesis of poly(allylamine hydrochloride) (PAH). PAH was synthesized by two methods. The first method, PAH was synthesized by solution polymerization with allylamine hydrochloride (AH) as monomer, NH₄S₂O₈/NaHSO₃ as redox initiators; the second one, poly(allylamine phosphate) (PAP) was synthesized by solution polymerization using allylamine phosphate (AP) as monomer, 2,2'-azo-bis-2-amidinopropane dihydrochloride (AAP·2HCl) as initiator. PAP was reacted with concentrated hydrochloric acid and converted into PAH. The chemical structure and thermal property of PAH were studied by Fourier transform infrared (FTIR) spectrometer, nuclear magnetic resonance (NMR) spectrometer, thermogravimetric analyzer (TGA), differential scanning calorimeter (DSC), X-ray diffractmeter (XRD), respectively. The effects of varying the concentrations of initiator and monomer on the polymerization conversion were also investigated. Preparation of PAH was confirmed by the disappearance of deformation vibration absorption peak at 997 cm^-1 (due to C=C bonds) in the FTIR spectrum. The three peak areas and their chemical shifts in 1H-NMR spectrum were consistent with the three kinds of hydrogen atoms of PAH formula, which also proved that PAH was synthesized. PAH had two decomposing stages. The glass transition temperature (Tg) of PAH increased with decreasing concentration of initiator. The conversion of monomer increased with increasing concentration of initiator and monomer.2. Study on LbL self-assembly between PAH and PAA. The self-assembly between PAH and PAA was carried out by LbL self-assembly method. The carboxyl groups of PAA were activated by 1-ethyl-3-(3-dimethyllaminopropyl) carbodiimide hydrochloride (EDC·HCl) and N-hydroxysulfosuccinimide sodium salt (Sulfo-NHS) for the reaction with the amion groups of PAH to yield the amido link. The self-assembly films were characterized with FTIR, ultraviolet-visible (UV-Vis) spectrophotometer and atomic force microscope (AFM), respectively. The presence of stretching vibration absorption peaks of C=O bond in amido at about 1650 cm^-1 in FTIR spectra indicated that amido bond generated under the reaction of PAH and PAA in the LbL self-assembly process. UV-Vis absorption spectra showed the absorbance at 196 nm increased with increasing self-assembly time. The absorbance of LbL film increased with increasing molar concentration of PAH and PAA. AFM showed that polymer film structure was formed on silicon wafer surface.3. The preparation of PPAS and LbL self-assembly study on PPAS and PAA. Polystyrene (PS) was synthesized by solution polymerization. Poly(p-nitrostyrene) (PPNS) was prepared by nitration of PS using the mixture of concentrated nitric acid and sulfuric acid as nitrating agent. PPAS was synthesized by reduction reaction of PPNS using stannous chloride and concentrated hydrochloric acid as the reducing agent. A stable, covalent bond-linked multilayer LbL self-assembly film was prepared by self-assembly of PPAS and PAA. The assembly process was monitored by UV-Vis. A good linear relationship between absorbance and the layer number was observed and was an indication of a progressive alternate reaction of PPAS and PAA. The absorbance at 240 nm increased with increasing self-assembly time. The absorbance of LbL film increased with increasing molar concentration of PPAS and PAA. The presence of stretching vibration absorption peaks of C=O bond in amido at about 1650 cm^-1 in FTIR spectra indicated that amido bond generated under the reaction of PPAS and PAA in the LbL self-assembly process. AFM showed that polymer film structure was formed on silicon wafer surface.