Study On Ring-Plymerization Kinetics Of Hexachlorocyclotriphosphazene And Fundamental Research On Some Application Of Polyphosphazenes

Chapter 1 After summarizing history, actuality and development of phosphazene compounds, their synthetic procedures, structure, performance and application in the field of flame-resistant materials and biomaterials were introduced in detail. Some questions on debate about synthesis and mechanism were described. On the base of above questions, the research content of thesis was presented.Chapter 2 Some present research outcome, involving some process, mechanism and equation on reaction kinetics about ring-opening polymerization of hexachlorocyclotriphosphazene, was described. Then, Van Krevelen' method about calculating various properties of polymer according to their structures was introduced, especially the relationships between molar structure in elastomer, the limiting oxygen index or the char yield data of molar constitutional unit and molecular structure were described in detail. In addition, combustion process, combustion property and fiame-retardant mechanism were presented simply.Chapter 3 Hexachlorocyclotriphosphazene and octachlorocyclotetra- phosphazene with high purity were synthesized in s-tetrachloroethane from phosphorus pentachloride and ammonium chloride. The yield of two cyclophosphazenes depended on many factors, such as grain size of NH4Cl, the type and volume of the solvent, reaction temperature and post treatment, which were also discussed in detail. At last, some attempts have been made to synthesize N₃P₃Cl₆ and N₄P₄Cl₈ using monochlorobenzene as solvent and anhydrous magnesium chloride with pyridine as catalyst.Thermal ring-opening polymerization, of two cyclophosphazenes (N₃P₃Cl₆ and N₄P₄Cl₈) has been investigated. A complex of factors, including monomer purity, catalyst and temperature fluctuations, are considered as important factors, which affectthe polymerization significantly. In the course of N3P3CI6 polymerization, N4P4CI8 did not participate in the reaction, and only acted as a polymerization inhibitor or increased the possibility of crosslinking, which would slow down the polymerization rate and decrease the molecular weight or the yield of soluble product. At the same time, tetramer was not a suitable monomer to produce poly(dichlorophosphazene) because it could only be polymerized with a favorable rate at temperature as high as 300°C, however, drastic depolymerization was also detected at this temperature. On the other hand, introduction of some water could increase the polymerization rate significantly. The amount of water should be accurately controlled, otherwise, yield of cross-linked product increased and molecular weight of the final polymer decreased. At last, the kinetics of the N3P3CI6 were investigated at 260 °C. The reaction was found to be second-order with an activation energy of 54.97kcal>mol"1. Polymerization catalyzed by CaS04?2H2O was first-order at 260°C. To clear above phenomena, a new mechanism and equation on reaction kinetics were proposed.Chapter 4 Attempts have been made to synthesize poly(diethoxyphosphanzene) via thermal ring-opening polymerization of octachlorocyclotetraphosphazene. The structures of the monomer and polymer were investigated by means of IR and 'H-NMR. Dynamic mechanical behavior and some physical properties of the poly(diethoxyphosphanzene), such as glass transition temperature, density and intrinsic viscosity number, were discussed. The calculated molar volume of constitutional unit (-P=N⁾ was 34.06cm3/mol via experimental data by semi-empirical method. In addition, the analyzed backbone conformation of polymer was twisted [TC']n rather than planar [TC]n, and the calculated torsional angle was 56.3° by the extension percentage of polymer. A primary goal of the present study is to extend our understanding of molecular structure and conformational properties of polyphosphazene by performing theoretical calculations.Chapter 5 Novel phosphazene cyclomatrix network polymers have been synthesized via nucleophilic displacement of activated nitro groups of tri (4-nitrophenoxy)tri (phenoxy) cyclotriphosphazene and hexa(p^nitrophenoxy) cyclotriphosphazene with the hydroxyls of bisphenol A. Both the monomers and polymers were characterized by FT-IR and 'H-NMR measurement and their structures were identified. Thermal andflame-retardant properties of the polymers were investigated using dynamic thermogravimetric analysis (TGA) in air, pyrolysis and combustion experiments. Both solid and gaseous degradation products were collected in pyrolysis process and analyzed by using FT-IR, gas chromatography mass spectrometry and SEM. The results demonstrated that the cyclomatrix phosphazene polymer would have excellent thermal stability and flame-retardant property if it can form a crosslinked phosphorous oxynitride structure during pyrolysis or combustion. A flame-retardant mechanism of 'intumescent' was proposed to elucidate the pyrolysis and combustion process. In addition, the limiting oxygen index (LOI) was calculated as 34.3% via the char yield data by semi-empirical method, then the char yield data of molar constitutional unit (-P=N-)3 was obtained as 15.54, which provided theoretical base for designing the highly thermal and flame-retardant properties of the cyclomatrix phosphazene polymer.Chapter 6 Five different polyphosphazenes with glycino ethyl ester, alanino ethyl ester and phenyl alanino ethyl ester substituents were synthesized by the interaction of poly(dichlorophosphazene) with the same or different amino acid ester. Total halogen replacement was achieved only with glycine ethyl ester, but replacement of the remaining chlorine could be eggected by the subsequent introduction of methylamino groups as cosubstituents. By varying the reaction conditions, the influence of reaction conditions on the amino acid ethyl ester's degree of substitution was investigated, and polymers with higher degree of substitution were obtained under optimized reaction condition. Moreover, it was found that the addition sequence of two amino acid ethyl esters was an important factor in deciding the structure of resultant polymer. At last, their physical properties, degradability in the solution or solid states and release behavior of BSA were studied.Chapter 7 The nucleophilic substitution reaction of poly(dichlorophosphazene) with sodium 2-methoxyethoxide and glycine ethyl ester has been studied in detail. Polymers prepared by different methods have been characterized by 'H NMR, and the results reveal that addition sequence of the two nucleophilic reagents is an important factor in deciding the structure of resultant polymer. If alkyl ether was added first, subsequently introduced amino acid ester would not only react with residual P-Cl, but also attack the alkyl ether side units present, either by replacing the whole group or just -OCH3. As a...