Synthesis And Properties Studies On The Alicyclic-functionalized Polyimides Derived From Cyclopentanone And Norbornene Anhydride

With the rise of the flat panel display industry and Photovotaic industry, driven the development and needs of high-performance polyimide materials. While conventional wholly aromatic polyimides have excellent thermal properties and mechanical properties, but the requirements of its performance in these emerging areas are not limited to these properties. For instance the chip industry requires polyimide material with low dielectric constant; flat panel display industry needs transparent properties of polyimide. In order to expand application areas of aromatic polyimides, many measures have been adopted to modify the structure of polyimide. Studies have shown that the introduction of an alicyclic structure on PIs main chain can destroy conjugated π bond, weaken chain to chain cohesive force, disturbed its planarity, reduce its crystallinity, and lead to improve the processability of polyimide. At the same time, the incorporation of fluorine-containing groups such as trifluoromethyl increasing distance of intermolecular and the free volume of polymer, decreasing the degree of stacking, reducing the number of polarization particles in unit volume weaken the charge transfer complex effect, all these effects effectively improving the integreated properties of PIs. So that preparing polyimide film with low dielectric constant and transparent properties. In view of this, in this article, we decided introducing alicyclic structure, trifluoromethyl, and the pyridine ring structure on the backbone of polyimide to its modification. Our study focus on following three aspects:Firstly,the diphenol compound 1,1-bis(4-hydroxyphenyl) cyclopentane(BHCP) was systhesised from the nucleophilic addition reaction of cyclopentanon with excessive amount of phenol. Then BHCP react with trimellitic anhydride chloride(TMAC) getting anhydride compound 1,1-bis(4-(3,4-dicarboxylicanhydridebenzoyloxy)phenyl)cyclopentane(BDAPCP). Two types of polyimide films, Cardo-type series(CPI-x) and aromatic series(PI-x) were prepared from condensation of BDAPCP and aromatic dianhydride 3, 3’, 4, 4’-oxydiphthalic anhydride(ODPA) with four aromatic diamines 2, 2’-dimethyl-(1, 1’-diphenyl)-4, 4’-diamine(DMB), 1, 4-bis(4-aminophenoxy) benzene(1, 4, 4-APB), 1, 3-bis(4-aminophenoxy) benzene(1, 3, 4-APB) 4,4-Oxydianiline(ODA), respectively. CPI-x series exhibited considerable mechanical properties with tensile strengths ranging in 87.6-102.9 MPa, elongations at break 6.8-9.5%, and possessing fairly good thermal properties with the glass transition temperature(Tg) in the range of 216-271.4 °C and Td5 in N2 of 431-441 °C. Transmittance in 500 nm(T500) of CPI-x was higher than the corresponding PI-x. Moreover, Cardo-type series displayed better solubility than Aromatic series, which was further confirmed by larger d-spacing values of the former than those the latter calculated from the Wide-angle X-ray Diffraction spectra. Comparative dynamic dielectric measurement revealed that Cardo-type dianhydride endows CPI-4 with lower dielectric constant(εˊ)(3.21 at 1 MHz and 25 °C) and dielectric loss(εˊˊ)(0.0071 at 1 Hz and 25 °C).Secondly, we use norbornene anhydride as a starting material, was prepared saturated and unsaturated diol compound bicyclo[2.2.1] hept-5-ene-2,3-dimethanol(BHED) and bicyclo[2.2.1] heptane-2,3-dimethanol(BHDO), then they are reacted with 2-chloro-5-nitro-trifluoromethylphenyl to get saturated and unsaturated fluorinated alicyclic functional dinitro 2,3-bis(4-nitro-2-(trifluoromethyl) phenoxymethylene)bicyclo[2.2.1] heptane(BNFCH), 2,3-bis(4-nitro-2-(trifluoromethyl)phenoxymethylene)bicyclo[2.2.1]heptane-5-ene(BNFCHE). Finally, the Pd /C and hydrazine hydrate to its reduction reaction to get the desired product, alicyclic and trifluoromethyl functionalized diamine monomer 2,3-bis(4-amino-2-(trifluoromethyl)phenoxymethylene)bicyclo[2.2.1]heptane(BAFCH), 2,3-bis(4-amino-2(trifluoromethyl)phenoxymethylene)bicyclo[2.2.1] hept-5-ene(BAFCHE). Then BAFCH, BAFCHE respectively polymerize with four dianhydride monomer: 4, 4’-oxydiphthalic anhydride(ODPA), benzophenonetetracarboxylic dianhydride(BTDA) biphenyltetracarboxylic dianhydride(BPDA), pyromellitic dianhydride(PMDA) getting polyimide film code as PI-x. We test comprehensive properties of polyimide films, including solubility, optical properties, dielectric properties, and found that compared with wholly aromatic polyimide film, properties of alicyclic and trifluoromethyl functionalized PIs have improved significantly.Thirdly, we have based on our previous experiments accumulatied bis phenol compound: 1,1-bis(4-hydroxyphenyl)cyclopentane and 1,1-bis(4-hydroxyphenyl) cyclohexane, reacted with 2-chloro-5-nitropyridine prepared the corresponding dinitro compound 1,1-bis [4-(4-nitro-pyridyloxy)phenyl]cyclopentane(BNPBP) and 1,1-bis[4-(4-nitro-pyridyloxy)phenyl]cyclohexane(BNPBH), palladium carbon and hydrazine hydrate to its reduction reaction to get the diamine monomer 1,1-bis [4-(4-pyridyloxy) phenyl] cyclopentane(BAPBP) and 1,1-bis [4-(4-pyridyloxy) phenyl] cyclohexane(BAPBH). The corresponding products were characterized by IR and NMR, and the results of the test comforming to our designed structure.