Polymerization Catalyzed By Phosphazene

In this PhD. thesis, we have used (1-tert-butyl-4,4,4-tris(dimethylamino)-2,2-bis[tris(dimethylamino) phophoranylidenamino]-2A5,A5-catenadi(phosphazene)(t-BuP4), a phosphazene base, to catalyst the homo-or co-polymerization of β-lactam (2-azetidinone),1,3-dioxolan-2-one (EC), s-caprolactone (CL), glycidyl methacrylate (GMA) and methyl methacrylate (MMA). The results and conclusions are as follows.1. We have synthesized nylon3via ring opening polymerization of β-lactam in a mixture of dimethylacetamide (DMAc) and LiCl. The polymers have been characterized by nuclear magnetic resonance spectroscopy (NMR), Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), laser light scattering (LLS) and viscometry. Such synthesized nylon3is a linear and crystalline polymer with a molecular weight as high as105g/mol. The intrinsic viscosity ([η]) relates to the weight average molecular weight (Mw) as [η]=1.02MW0.91. The effects of solvent, temperature and catalyst concentration on the polymerization have been examined. The molecular weight and yield increases with the amount of LiCl in the polymerization mixture, but both of them decrease with temperature at a temperature above50℃. As the catalyst concentration increases, the yield and the molecular weight of nylon3decrease. The possible mechanism for the initiation of polymerization is discussed.2. Poly(ethylene carbonate-co-ethylene oxide)(EC-co-EO) has been synthesized by ring opening polymerization of EC. Nuclear magnetic resonance spectroscopy shows that the copolymer chain consists of EO-EC-EO-EO sequences. Gel permeation chromatography (GPC) measurements indicate the molecular weight distribution is1.43-1.66, and the molecular weight increases with monomer conversion. Thermal analysis measurements demonstrate that the copolymer is amorphous with a glass transition temperature (Tg) of about-42℃and an onset decomposition temperature at about200℃.3. Copolymerization of CL and MMA has been studied. Nuclear magnetic resonance (NMR) and differential scanning calorimetry (DSC) measurements indicate that the cyclic ester and vinyl monomer form a random copolymer. Thermogravimetric analysis (TGA) measurements demonstrate that such a random copolymer exhibits a decomposition temperature higher than those of the corresponding homopolymers. The present study reveals a "hybrid copolymerization" i.e., a combination of vinyl polymerization and ring-opening polymerization, which makes the incorporation of cyclic and vinyl monomers into the same polymer chain possible. Hybrid copolymerization is expected to produce a number of new interesting polymers.4. Hyperbranched poly(s-caprolactone)(h-PCL) is synthesized via copolymerization of CL with GMA as the branching agent in one pot. Size exclusion chromatography measurements with light scattering and viscosity detection clearly demonstrate that the resultant polymer has a hyperbranched structure. The approach presented here can be used to synthesize other hyperbranched polymers.