Synthesis And Properties Of Soluble Copolyimides Containing Phthalazinone Moieties

It is well known that conventional polyimides are useful high performancematerials for their excellent comprehensive properties such as outstanding thermal stability, high flame retardance good mechanical properties and electronic properties. As a result, they have been widely used in the microelectronics as films, especially in flexible copper clad laminates (FCCLs) for flexible printed circuit board. However, the widespread applications of polyimides are generally limited by processing difficulties because of their poor solubility and high processing temperature, which are caused by their strong interchain forces, inherent macromolecular rigidity, or semicrystallinity. As a result, the development of soluble polyimides in imidized form without influence of their own excellent properties has attracted major interest.In this work, our efforts had been focused on synthesis of polyimides by introduction of twisted, noncoplanar phthalazinone moieties into the polymer backbone via one-pot imidization technique in the solution. The effect of molecular chain structure of polyimides on the properties of the polymers, such as thermal properties, solubility and dielectric constant was investigated systematically.In this thesis, the polyimides containing phthalazinone moieties were prepared from 1,2-Dihydro-2-(4-aminophenyl)-4-[4-(4-(aminophenoxyl)phenyl)](2H)phthalazin-1-one (DHPZDA) and 2,2-bis [4-(3,4dicarboxyphenoxy) phenyl] propane dianhydride (BPADA) by one-pot imidization technique in the solution firstly. The synthesis process was optimized with respect to reaction solvents, solid content, time, temperature, and molar ratio of the monomers. The best process was as follows:the polymerization was conducted at room time for 2 h and at 210℃for another 16 h in sulfolane, and the content was 20% and molar ratio of the monomers was 1.01. The inherent viscosity of this polymer could reach 1.12 dL/g in NMP at 25℃. The polyimide showed amorphous nature as determined by wide angle X-ray diffraction (WAXD) and was soluble in a variety of aprotic polar solvents, such as N-methyl-2-pyrrolidinone (NMP), N,N-dimethylacetamide (DMAc), chloroform etc. The polyimide exhibited good thermal properties with glass transition temperature (Tg) of 262℃and 5% loss temperature (T5%) of 486℃in nitrogen atmosphere. The polyimide film was subjected to tensile tests. And the tensile strength, elongation to break, and tensile modulus was 76.8 MPa,18%and 1.3 GPa, respectively. In order to analysis the effect of polymer chain flexibilty on the comprehensive performance of polyimides, two series of copolyimides were designed and synthesized by two diamines, DHPZDA and 4,4'-diaminodiphenyl ether (ODA), with two dianhydrides 3,3',4,4'-benzophenonetetracarboxylic dianhydride (BTDA) and BPADA, or by DHPZDA ODA, and 4,4'-oxydiphthalic anhydride (ODPA) and BPADA, respectively. The copolyimides were named as series of PIA and series of PIB, respectively. The obtained polymers exhibited excellent thermal stabilities (series of PIA:Tgs:252～272℃, T5%:489～510℃；series of PIB:Tgs:248～267℃, T5%:485～516℃), good solubility in polar organic solvents. The Tg values of the series PIA were higher than the series PIB with the same ratio. The copolyimides exhibited good electrical properties with surface and volume resistances on the order of magnitude of 1015Ωand 1015Ω·m, respectively. The polymer thin films exhibited good mechanical properties (PIA11:the tensile strength:79.6 MPa, tensile modulus:1.5 GPa, elongation to break:26%; PIB11:the tensile strength:82.8 MPa, the tensile strength:1.7 GPa, the tensile strength:28%), low dielectric constant (series of PIA:2.6～3.3; series of PIB: 2.5～3.1), and low water absorption (series of PIA:0.90%～0.99%; series of PIB:0.81%～0.88%), indicating that the copolyimides series of PIB exhibited better performance in mechanical properties, dielectric constant and water absorption than series of PIA.In order to further reduced the dielectric constant, two series of novel fluorinated copolyimides containing phthalazinone moieties were prepared with BTDA, 4,4'-(hexafluoroisopropylidene) diphthalic anhydride (6FDA), DHPZDA and ODA, or ODPA, 6FDA, DHPZDA and ODA as reactive monomers, respectively. The copolyimides were named as series of PIA and series of PIB, respectively. The obtained polymers exhibited excellent thermal stabilities (series of PIC:Tgs:248～262℃,T5%:504～513℃; series of PID:Tgs:243～257℃, T5%:496～505℃) and good solubility in polar organic solvents. The copolyimides exhibited good electrical properties with surface and volume resistances on the order of magnitude of 1015Ωand 1015Ω·m, respectively. The obtained polyimides films exhibited good mechanical properties (series of PIC:tensile strength:69.5～79.3 MPa, elongation to break:16%～23%, tensile modulus:1.5～1.7 GPa; series of PIC:tensile strength:81.0～85.9 MPa, elongation to break:28～34%, tensile modulus:1.7～1.8 GPa GPa), low dielectric constant (series of PIC:2.2～3.1; series of PID:2.1～2.9) and low water absorption (series of PIC:0.62%～0.88%; series of PID:0.59%～0.84%).From the molecular design, a novel kind of diamine containing bicarbazole structure was synthesized and then reacted with some dianhydrides to prepare a series of soluble polyimides. Herein, the synthesis methods of diamine monomer containing carbazole moieties were studied, and the reduction process was optimized. The carbazole-based dinitro compound has been synthesized in high yield (>92%). Catalytic reduction was used to reduce the dinitro compound, which employed the Pd/C and as catalyst, with the hydrazine hydrate (80%) as reductant. The effect of reaction temperature, the amount of catalyst and solvent of the reaction were investigated in order to increase the production yield. The results showed that the Pd/C was a reasonable catalyst for the synthesis of diamine containing carbazole moieties, when the reduction was conduct after 6 hours at 90℃with Pd/C of lOg/mol, the yield of bis(N-4-amine-phenyl)-3,3'-bicarbazole (BCZDA) could reach more than 71%. The results of IR, NMR, MS showed it had the same structure as designed. A series of copolyimides were synthesized from BCZDA, BPADA, DHPZDA and BTDA. The structures of the polyimides were confirmed by IR and'H-NMR. The molecular weight and distributing of the copolymers obtained were tested by GPC. The thermal behavior data were obtained by DSC and TGA. The results showed all of the polyimides have excellent thermal stability (Tgs: 295～305℃,T5%:505～526℃) and could be soluble in some polar organic solvents such as NMP and DMAc etc. The obtained polyimides films had tensile strength, elongation to break, and tensile modulus in the ranges of 69.5-79.3 MPa,16%～23% and 1.2～1.5 GPa, respectively. Dielectric constant values of the polyimide films were in the range of 3.1～3.3.The flexible copper clad laminates were prepared by coating method with the polyimide solutions cast on the copper foil laminate directly. The obtained FCCL with good appearance surface and uniform dimension exhibited better comprehensive properties (dielectric constant: 2.3～3.1, water absorption:0.76%～0.94%, coefficient of thermal expansion:25×10-6～34×10-6/℃, peel strength:1.66～3.08 kN/m) than national standard GB13555-92.