Synthesis And Properties Of Pyridine-containing Polyimides And Novel Hyperbranched Polyimides

Linear aromatic polyimides (PIs) have been studied extensively as high performance materials due to their outstanding thermal and thermo oxidative stabilities, chemical resistance, excellent mechanical and electrical properties. They have been widely utilized in the traditional field of gas separation, adhesives, microelectronics, aerospace devices, integrated electronic circuits and so on. The pyridine-containing PIs can increase electron affinity to improve electron-transporting properties and offer the possibility of protonation of the lone pair electrons as a way of modifying their luminescence properties, for the development of polymeric photoelectricity and organic photoluminescence materials. However, the pyridine-containing PIs products still exhibit some drawbacks, such as insoluble nature limit their applications. Therefore, to improve the solubility of these new polymer is particularly urgent. Systematic exposition of the first of PI, structure, properties, synthesis methods and applications, and then a detailed introduction of containing a pyridine ring polyimide as well as the synthesis of hyperbranched polyimide (HBPI) and modified.In this article the PIs was systematically described for the development, structure, properties, synthesis methods, and applications and so on, then a detailed description of the synthesis and modification of containing a pyridine ring polyimide, as well as hyperbranched polyimide (HBPI).First, a novel pyridine-containing aromatic diamine monomer4-phenyl-2,6-bis[3-(4-amino-2-trifluoromethyphenoxy)phenyl]pyridine (m,p-6FPAPP) was synthesized by modified Chichibabin reaction, Wilianms reaction and hydrogenation deoxidize reaction. Whereafter, soluble fluorinated polyimides were synthesized via the conventional two-step method by using the aromatic diamine as the diamine monomer,2,2-bis[4-(3,4-dicarboxyphenoxy)phenyl]propane dianhydride (BPADA) and3,3’,4,4’-biphenyltetracarboxylic dianhydride (BTDA) as the dianhydride monomers in dimethylformamide (DMF). The structure and performance of polymer were characterized by FT-IR,1H NMR, water uptake testing, solubility testing, DSC, TGA and UV-vis. The results showed that there were characteristic peaks of polyimides around1780cm-1,1720cm-1and 1380cm-1in the FTIR spectra. The polyimides were soluble in common organic solvents such as m-Cresol, DMF, dimethylacetamide (DMAc), dimethyl sulfoxide (DMSO)(1-methyl-2-pyrrolidone) NMP, tetrahydrofuran (THF). They had good thermal stability, with the glass transition temperature (Tg) of202.1-219.7℃. Besides, their temperature at10%weight loss were in the range of537.0-572.8℃, while the weight maintenance rate of samples in800℃were60.7%-63.1%in nitrogen atmosphere. The PI films were also found to possess the cut-off wavelengths of375-380nm and water uptake of0.55%-0.63%.Afterward, a novel pyridine-containing aromatic diamine monomer,4-[4-hydroxyphenyl]-2,6-bis[4-(2-aminophenoxy)phenyl]pyridine (p, o-HAPP), was synthesized by a modified Chichibabin reaction of p-Hydroxybenzaldehyde and a substituted acetophenone,4-(2-nitrophenoxy)acetophenone (p,o-NPAP), followed by a reduction of the resulting dinitro compound4-[4-hydroxyphenyl]-2,6-bis[4-(2-nitrophenoxy)phenyl]pyridine (p,o-HNPP) with Pd/C and hydrazine monohydrate. The aromatic diamine was employed to prepare a series of pyridine-containing polyimides by polycondensation with various aromatic dianhydrides in N,N-dimethylformamide (DMF) via the conventional two-step method. The inherent viscosities of the resulting poly(amic acid)s (PAAs) and polyimides (PIs) were in range of0.62-0.76and0.52-0.64dL/g, respectively. The obtained novel PIs exhibited high solubility in common organic solvents, such as m-Cresol, DMF, N,N-dimethylacetamide (DMAc), dimethylsulfoxide (DMSO), N-methylpyrrolidone (NMP), tetrahydrofuran (THF) and chloroform (CHCl3). Meanwhile, flexible PI films were obtained, which had excellent thermal stability, with the glass transition temperature (Tg) of259.8-323.4℃and the temperature at10%weight loss of485.5-576.4℃in nitrogen atmosphere. The protonated polymer showed UV-Vis absorption in the region200-400nm and displayed strong fluorescence intensity (470nm) in NMP solution.Finally, a novel pyridine-containing BB’2-type triamine,2,4,6-tris [4-(2-aminophenoxy)phenyl]pyridine (p,o-TAPP), was synthesized by a modified Chichibabin reaction, Wilianms reaction and hydrogenation deoxidize reaction. Whereafter, the triamine employed to prepare a series of amine-terminated and anhydride-terminated pyridine-containing hyperbranched polyimides (HBPI) by polycondensation with four commercially available A2-type dianhydrides via a A2+BB’2method. The inherent viscosities of the resulting AM-HBPI and AD-HBPI were in range of0.54dL/g～0.67dL/g and0.55dL/g～0.69dL/g, respectively. The obtained novel AM-HBPI and AD-HBPI exhibited high solubility in common organic solvents, such as m-Cresol, DMF, DMF, DMAc, DMSO, NMP, THF, CHCl3,CH2Cl2, respectively. Meanwhile, in nitrogen atmosphere, AM-HBPI and AD-HBPI were obtained, which had excellent thermal stability, with the glass transition temperature (Tg) in range of273.8℃～298.0℃and270.7℃～307.31℃, the temperature at10%weight loss of543.6℃～558.9～and551.2℃～568.6～, respectively. The protonated polymer showed UV-Vis absorption in the region200-400nm and displayed strong fluorescence intensity (465nm) in NMP solution.