Synthesis And Characterization Of Polyimide From 2,2'-bis (4-aminophenoxy Phenyl) Propane

Polyimides are a typical kind of high performance polymers with high strength and high modules, higher thermal stability, especially, resistance to radiation and dialectical property. Therefore, the polyimides are extensively utilized in the areas of films, fibers, plastics, composites, foams, membranes, etc.In this thesis, a diamine monomer 2, 2'-bis (4-aminophenoxy phenyl) propane (BAPP) was synthesized firstly. Then, two soluble polyimides were synthesized successfully by condensation polymerization between two dianhydride monomer ODPA (or BTDA) with diamine monomer BAPP via a two-step process including synthesis of polyamic acid and imidization.To prepare BAPP, the nucleophilic substitution reaction of p-chloronitrobenzene and bisphenol A in the presence of potassium carbonate was carried out, followed by catalytic reduction with hydrazine and Pd/C. FTIR, ~1H NMR, elemental analysis and DSC were employed to characterize the structures and the properties of the resulting BAPP. It was indicated that the above reaction produced our expected BAPP with a high purity and the melting point of 129.4 ℃ by DSC.Two soluble polyimides were synthesized successfully bycondensation polymerization between two dianhydride monomer ODPA (or BTDA) with diamine monomer BAPP via a two-step. FTIR was employed to study the structures of polyamic acid and polyimide. The effect of reaction time on the intrinsic viscosity of polyamic acid was discussed, and it was up tol.32 g/dL with reaction time of -15 hr. In situ FTIR was used to monitor the change of the polymer structure during imidization process at an elevated temperature. The spectra showed an initial dissociation of the amide bonds, producing anhydride and amine end groups, and the embrittlement of the film. Increasing temperature leaded to recombination above terminal functional groups, consequently, resulting in the toughness recovery of the film. The Tg of PI (L) and PI (S) DSC was 220°Cand 236°C, respectively. This is to say, the condition of imidization has an important influence on the properties of polyimides. Moreover, the thermo cyclization from poly(amic acid) to polyimide could be described by the first-order reaction.The thermal properties of polyimides (ODPA/BAPP and BTDA/BAPP) were characterized by DSC, TGA, DMA, etc. The results indicated that the polyimides possessed high glass transition temperatures (Tg) of 240 °C and high thermal stability of 502-578°C at a 10% loss in N2. The measurement of mechanical properties showed that the novel polyimides from BAPP exhibited a typical yield behavior of thermoplastic polymers, which was very different from other polyimides. Theelongation at break of ODPA/BAPP and BTDA/BAPP was 29% and 13%, respectively. The polyimides had a good solubility in some solvents, such as NMP, DMAc, DMF and m-cresol due to the chain containing -C(CH3)2, -O- and -C=O.Kong Cuili (Material Processing Engineering) Supervised by Prof.: Zhang Qinghua...