Polyallylamine (PAH) was synthesized by bulk polymerization with allylamine hydrochloride (AH) as monomer and ammonium persulfate/sodium bisulfite as redox initiator system. The structure and properties of the polymer were studied by Fourier transform infrared spectrometer (FTIR), nuclear magnetic resonance spectrometer (NMR) and thermogravimetric analyzer (TGA). At the same time, the effects of initiator dosage on polymerization conversion and relative viscosity of polymer were investigated. The results show that the characteristic absorption peak of carbon-carbon double bond at 998cm- 1 in infrared spectrum disappears, and the peak shape, peak area and chemical shift of polymer and monomer are obviously different in NMR spectrum, which proves that AH polymerizes to form PAH. The decomposition of PAH is divided into two stages, which is completely decomposed at 650℃ and has high thermal stability. With the increase of initiator dosage, the monomer conversion rate increases and the relative viscosity of polymer decreases. When the amount of initiator is 20% of the monomer mass, the monomer conversion and the relative viscosity of the polymer are 42.65438 0% and 65438 0.0348, respectively. Polyallylamine hydrochloride; Bulk polymerization; Thermal stability; Polyallylamine (PAH) with a relative viscosity of 1 is a polymer electrolyte with primary amine groups. Due to the high reactivity of amino groups, polycyclic aromatic hydrocarbons can be easily modified to obtain functional polymer materials, which can be used in papermaking [1], water treatment and metal complexation. It is also widely used in self-assembly [2-3], catalysis [4], membrane separation [5], exchange resin [6], hydrogel [7], microcapsule [8] and composite material [9]. Because the chain transfer of allyl compounds is serious in the process of free radical polymerization [10], especially the chain transfer is aggravated by the existence of amino groups, the direct polymerization of allylamine (AH) can not obtain PAH[ 1 1]. There are two main methods to synthesize PAH: one is chemical modification of polymer materials [12]; The second is the free radical polymerization of inorganic acid salts in allylamine [14- 15]. In the 1940s, Parker et al. [12] studied the catalytic hydrogenation of polyacrylonitrile to synthesize PAH, but the product structure was complex, and it often contained cyano, amino and imino groups. Panzer et al. [13] used polymer quaternary ammonium salt obtained by the reaction of polychloropropylene with trimethylamine as flocculant. Due to the limitation of reaction conditions of polymer chemical modification, only products containing a certain amount of amino groups can be obtained. In view of this, 1976 kabanov et al. initiated PAH in phosphoric acid with 60Co, but the conversion rate was low. 1984 Harada[ 14] found that water-soluble azo initiators such as 2,2'-azo-di -(2- methylpropylenediamine) hydrochloride are very easy to initiate allylamine polymerization in water with high conversion rate, but these initiators are expensive and large in dosage, and have not been applied in industry at present. However, European patent [15] reported that PAH could be obtained by allylamine polymerization with metal hydrochloride /H2O2 as initiator system and sodium pyrophosphate as complexing agent, but the degree of polymerization was not high. Based on the advantages and disadvantages of these methods, this paper adopts the second method to prepare PAH, that is, free radical polymerization of inorganic acid salts in allylamine. Because the initiator and monomer are easily available, the price is low, the reaction conditions are simple, and the conversion rate is high, high molecular weight PAH can be obtained. 2.2. 1 reagents and instruments used in the experiment: allylamine (Shandong Lu Yue Chemical Co., Ltd., content ≥ 99.5%); Concentrated hydrochloric acid (Tianjin Huadong Reagent Factory, AR); Potassium persulfate (K2S2O8, Tianjin Huadong Reagent Factory, AR) is refined by recrystallization from distilled water. Ammonium persulfate ((NH4)2S2O8, Tianjin (Hong Kong) Xintong Fine Chemical Co., Ltd., AR), refined by recrystallization with distilled water; Sodium bisulfite (NaHSO3, Tianjin Tianda Purification Material Fine Chemical Factory, AR); Methanol (CH3OH, Tianjin Huadong Reagent Factory, AR); Sodium hydroxide (NaOH, Tianjin North Tianyi Chemical Reagent Factory, AR); Deionized water. Instruments used: Fourier transform infrared spectrometer (FT-IR, NICOLET380, Thermo electron Company, USA), superconducting nuclear magnetic resonance spectrometer (NMR, AVANCE400, BRUKER Company, Germany), thermogravimetric analyzer (TGA, Pyris 6, Perkin-Elmer Company, USA), Ubbelohde viscometer. 2.2 polymerization mechanism allylamine polymerization belongs to free radical chain homopolymerization reaction, and the chain transfer is serious during the polymerization process, so it is difficult to obtain high molecular weight PAH. In this experiment, allylamine was converted into hydrochloride, and amino group was changed into ammonium ion, which enhanced its electric absorption and was beneficial to polymerization. The thermal decomposition of redox initiator generates free radicals to initiate monomer polymerization, and the reaction formula is as follows: 2.3 Synthesis process: 26.5mL allylamine is added into a three-necked bottle, and 3 1ml concentrated hydrochloric acid is added dropwise at 0-4℃ to obtain allylamine solution [16] with pH of 5.0, and the solution is concentrated to the required concentration (70%) under reduced pressure. Then, 20mL of the above solution was added into a three-necked bottle, heated to 50℃ under magnetic stirring, deoxygenated with nitrogen for 0.5h, then added with K2S2O8 (or (NH4)2S2O8) and NaHSO3 (molar ratio of substances 1: 1), and polymerized at 50℃ for 24h to obtain a yellow viscous liquid. Dropping viscous liquid into 120mL methanol, stirring, separating out pale yellow powdery solid, and performing suction filtration to obtain the product. Add a small amount of water to dissolve it, adjust the pH to weak alkalinity with 1mol/L NaOH solution, then add 200mL of water for vacuum distillation, and stop distillation when yellow viscous liquid is obtained. The solution was precipitated with methanol, then dissolved once with a small amount of water-methanol and filtered to obtain pale yellow powder. Drying at 50℃ in vacuum (vacuum degree 0.65438±0 MPa) for 24 hours, weighing and calculating the conversion rate.

Supplement to Respondent 2009-06-08 16:04 2.4 Structural Characterization and Performance Testing 2.4. 1 Determination of Conversion Rate: Weigh the vacuum-dried product and calculate the conversion rate (c%) according to the following formula c %):c% = product quality/allylamine quality ×100. Allylamine solution was coated on KBr sheet for Fourier transform infrared spectrum analysis. 2.4.3 NMR spectrum analysis: monomers and polymers were analyzed by 1HNMR, and the solvent was D2O. 2.4.4 Thermal stability test of polymer: In the nitrogen atmosphere with the flow rate of 20mL/min, the dried sample was heated from 30℃ to 800℃ at the rate of 20℃/min, and the thermal weight loss behavior of the sample was recorded. 2.4.5 Determination of relative viscosity of polymer: determine the viscosity of polymer solution with Ubbelohde viscometer. 0.25g of polymer was dissolved in 12.5mL NaCl solution with a concentration of 2mol/L, and transferred to a 25mL volumetric flask, and the volume was determined with deionized water. Keep it at 30℃ for 20min, and measure the flow time. Repeat for three times, and find the average relative viscosity number hr, hr=t/t0, where t and t0 are the flow time of the sample to be tested and 1mol/L NaCl solution in Ubbelohde viscometer respectively.