Synthesis and characterization of novel soluble pyridine‐containing polyimides based on 4‐phenyl‐2,6‐bis[4‐(4‐aminophenoxy)phenyl]‐pyridine and various aromatic dianhydrides

Abstract

A new kind of pyridine-containing aromatic diamine monomer, 4-phenyl-2,6-bis[4-(4-aminophenoxy)phenyl]-pyridine (PAPP), was successfully synthesized by a modified chichibabin reaction of benzaldehyde and a substituted acetophenone, 4-(4-nitrophenoxy)-acetophenone (NPAP), followed by a reduction of the resulting dinitro compound 4-phenyl-2,6-bis[4-(4-nitrophenoxy)phenyl]-pyridine (PNPP) with Pd/C and hydrazine monohydrate. The aromatic diamine was employed to synthesize a series of new pyridine-containing polyimides by polycondensation with various aromatic dianhydrides in Nmethy-2-pyrrolidone (NMP) via the conventional two-step method, i.e., ring-opening polycondensation forming the poly (amic acid)s and further thermal or chemical imidization forming polyimides. The inherent viscosities of the resulting polyimides were in the range of 0.79-1.13 dL/g, and most of them were soluble in common organic solvents such as N,N-dimethylacetamide (DMAc), NMP, and tetrahydrofuran (THF), etc. Meanwhile, strong and flexible polyimide films were obtained, which had good thermal stability, with the glass transition temperatures (T g ) of 268-3388C and the temperature at 5% weight loss of 521-5488C in air atmosphere, as well as outstanding mechanical properties with tensile strengths of 89.2-112.1 MPa and elongations at break of 9.5-15.4%. The polyimides also were found to possess low dielectric constants ranging from 2.53 to 3.11.

Soluble Polyimides Based on Long-chain Alkyl Groups via Amide Linkages

“…IR spectra were measured on a JASCO IR Report-100 spectrophotometer. The inherent viscosities of all polymers were measured using Cannon Fenske viscometers at a concentration of 0.5 g/dL in NMP at 30 C. Size exclusion chromatography (SEC) measurements were performed in NMP containing 10 mM LiBr at 40 C with a TOSOH HLC-8020 equipped with a TSK-GEL ALPHA-M. Number average molecular weight (M n ), weight average molecular weight (M w ) and polydispersity (M w =M n ) were determined by TOSOH Multi Station GPC-8020 calibrated with a series of polystyrenes as a standard.…”

“…However, owing to the instability of poly(amic acid)s and the liberation of water in the imidization process, problems can arise. Extensive research has been recently carried out to improve the solubility of polyimides and successful examples involve the incorporation of fluorine moieties, [2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17] bulky side groups, [18][19][20][21][22][23][24] alicyclic structure, 25 spiro structure, 26 cardo groups, 27,28 pyridine moiety, 29,30 porphyrin moiety, 31 acridine moiety, 32 and sulfonated structure, [33][34][35][36] and the applications include the functional materials such as low-k material, 3,14,15,25 colorless or light-colored polyimides, 9,10,12 gas transport membranes, 16,17,24 electrochromism materials, 22 pervaporation membranes, 7 materials for organic light-emitting diode (OLED), 27,…”

Soluble polyimides based on a novel pyridine-containing diamine m,p-PAPP and various aromatic dianhydrides

“…For the PI materials, synthesis of newly heteroaromatic monomers and corresponding PIs that have both good processability and maintained thermal stability would be very interesting, e.g., new kinds of heteroaromatic diamine or dianhydride monomers are always focused and employed in the synthesis of PIs; in other words, newly synthesized aromatic monomers would play very important roles in the synthesis of advanced PI materials [15,16]. It has been proven that introduction of rigid heteroaromatic pyridine ring to the polymer backbone could endow it with excellent thermal and thermo-oxidative stability, which should be useful to decrease the negative effects resulting from the introduction of flexible ether linkages in the poly(ether-imide)s backbone [17][18][19].…”

“…The obtained polyimides have better solubility than the analogous polyimides reported by Wang et al [17]. 0 ,4,4 0 -benzophenonetetracarboxylic dianhydride (BTDA or 2c) was purchased from Alfa Aesar (USA), and these aromatic tetracarboxylic dianhydrides were all recrystallized from acetic anhydride and then dried in vacuo at 150°C for 12 h before use.…”

Novel organosoluable aromatic polyimides derived from unsymmetrical 1,3-bis(4-aminophenoxy)naphthalene and aromatic dianhydrides

“…15,16 Unless carefully designed, however, polyimides have high softening temperatures and are often insoluble in most organic solvents in their imidized form, making them extremely difficult to fabricate. [17][18][19][20][21][22][23][24][25][26][27][28] To overcome this drawback, a large number of structural modifications have been attempted such as introduction of bulky lateral substituents, flexible alkyl side chains, unsymmetric, alicyclic or kinked structures in the polymers. [17][18][19][20] Generally, aromatic diamine with ether linkages and metaoriented phenylene groups led to an increase in polymer chain flexibility and solubility of polyimides, but has also lowered the effective upper use temperature of these polymers.…”