Study On The Polymerization Of Diazoacetates And Their Cycloaddition Products

With the development of society, more resources are needed increasingly. But non-renewable resources, like oil and coal, which are used mostly in modern society, have suffered severe problems of exhaustion and environmental pollution, so exploring alternative renewable and green energy resources becomes a major trend for the modern society development, which is also much of importance for the development of new functional polymers. This thesis mainly introduces the synthesis of 2-pyrazoline and fluorescent poly(2-pyrazoline)s from diazoesters, the copolymerization of diazoacetates with alkenes under the radiation of microwave and sunlight, as well as the polymerization of styrene with sunlight as the driven energy.In chapter 1, the classification, synthetic methods and reactivity of diazocompounds are expressed. The polymerization of diazocompounds, the 1,3-dipolar cycloaddition reaction with alkenes and the nucleophilic attack on C=O bond are described in detail. The introduction of fluorescent polymers, pyrazoline derivatives and upconversion fluorescent materials is also included.In chapter 2,3,4,5-triethoxycarbonyl-2-pyrazoline with high yield of 78.29% was obtained with a reaction time of 800 min from unique ethyl diazoacetate (EDA), at ambient temperature and high pressure with palladium chloride as catalyst. Compared with the reaction catalyzed by ruthenium and rhodium complex, this reaction increases the yield and shortens reaction time efficiently. The reaction kinetics and reaction mechanism were explored via NMR and on-line FT-IR, which indicates that the reaction is a first order reaction with a rate constant of 2.50x10-3 min-1. What’s more, in the reaction process, diethyl maleate (DEM) and diethyl fumarate (DEF) were produced with priority and then the 1,3-dipolar cycloaddition of EDA with them occurred, resulting in 3,4,5-triethoxycarbonyl-2-pyrazoline. Herein, the reaction rate of EDA with DEF is much higher than that with DEM.In chapter 3,3,4,5-triethoxycarbonyl-2-pyrazoline obtained in chapter 2 went through cyclo-polycondensation with the release of one molecule of ethanol, leading to the formation of cyclic oligo(2-pyrazoline) with different catalysts under reduced pressure of 500 Pa at a temperature of 180℃. The composition and properties of the obtained oligo(2-pyrazoline) are characterized with a series of methods, which proves that the repeating unit is formed from 3,4,5-triethoxycarbonyl-2-pyrazoline by the release of ethanol and connected with amide bond (i.e. peptide bond). The obtained oligomer possesses good fluorescent property with the relative quantum yield of 13%-26%, which is a kind of fluorescent pseudopeptide macromolecules. The application of the obtained oligomer in bioimaging was investigated by the cell culture experiment.In chapter 4, a new kind of polypyrazolines was synthesized from diazoacetates and maleic anhydride (MA). This reaction proceeded under simple conditions without the addition of catalyst at ambient temperature. Without the addition of solvent, the reaction was furious and completed instantaneously, and upon adding solvent, the reaction became mild in control. The molecular weight of the obtained oligopyrazoline is around 2000 g/mol. The composition of the oligomer was classified by matrix assisted laser desorption/ionization-time of flight mass spectrometry (MALDI-TOF-MS). A polymerization mechanism was proposed, that is, the polymerization proceeded via 1,3-dipolar cycloaddition and a cascade ring-opening insertion reaction. The obtained oligopyrazoline possesses a fascinating down-and upconversion fluorescent property. With the excitation wavelengths of 355 and 692 nm, the oligomer exhibits the same maximum emission at 445 nm. The quantum yield with the excitation wavelength of 350 nm is in the range of 12%-19%. The cell experiment of the obtained oligomer proves that it still shows good fluorescence in cells and exhibits no visible toxic effects on cells, which is potential in the application of bioimaging.In chapter 5, the poly(pyrazoline-ester)s with the molecular weight of 2100-6300 g/mol were synthesized by the intermolecular 1,3-dipolar cycloaddition of bisdiazo carbonyl compounds and dialkenes. Various characterization methods, such as NMR, FT-IR, UV-vis absorption spectrometry, fluorescent spectrometry, differential scanning calorimetry (DSC), thermogravity analysis (TG), gel permeation chromatography (GPC), were utilized to investigate the structure and property of poly(pyrazoline-ester)s. The pyrazoline group on the backbone of polymers contains several reactive centers, which could be modified to get new functional polymers.In chapter 6, diazoacetates and alkenes went through copolymerization under the radiation of new green energy resource, i.e. microwave, leading to copolymers with molecular weight of 800-14600 g/mol. The structure and properties of the obtained copolymers were characterized by NMR, FT-IR, UV-vis absorption spectrometry, differential scanning calorimetry (DSC), gel permeation chromatography (GPC). Moreover, the copolymerization of ethyl diazoacetate and styrene as well as the homopolymerization of styrene under sunlight were also investigated.