Influence of curing accelerators on the imidization of polyamic acids and properties of polyimide films

Abstract

In order to lower the imidization temperature of polyamic acids (PAA), the catalytic activities of the curing agents p-hydroxybenzoic acid (PHA), quinoline (QL), benzimidazole (BI), benzotriazole (BTA), triethylamine (Et₃N) and 1, 8-diazabicyclo [5.4.0]undec-7-ene (DBU) were investigated in the process of thermal imidization of PAA. In addition, the effect of these various curing agents on the thermal stabilities and mechanical properties of the resultant polyimide (PI) films was determined. Quinoline was found to be an effective curing accelerator in the use of two-step method for synthesizing PI. Due to its moderate base strength, low steric crowding effect and moderate boiling point, quinoline could not only accelerate PAA to achieve imidization completely at 180 °C, but also maintain the mechanical properties and thermal stability of the ordinary PI film. Any residual quinoline could be removed from PI films by heating at 250 °C for 4 h.

Keywords

polyimide film / curing accelerator / quinoline / low temperature imidization

References

[1] Sroog C E. Polyimides[J]. Prog. Polym. Sci., 1991, 16(4): 561-694.

[2] Liu H, Wen P, Kim J H, et al. Synthesis and Characterization of Photosensitive Poly(imide sulfonates) for Fuel Cell Application[J]. J. Wuhan. Univ. Technol., 2013, 28(4): 635-642.

[3] Ding M X. Polyimides: Chemistry, Relationship between Structure and Properties and Materials[M], 2006 Beijing: Chinese Science Press.

[4] Liaw D J, Wang K L, Huang Y C, et al. Advanced Polyimide Materials: Syntheses, Physical Properties and Applications[J]. Prog. Polym. Sci., 2012, 37(7): 907-974.

[5] Kuznetov A A, Tsegelskaya A Y, Belov M Y, et al. Acid-catalyzed Reactions in Polyimide Synthesis[J]. Macromol. Symp., 1998, 128(1): 203-219.

[6] Ali A A M, Ahmad Z. The Effect of Curing Conditions and Aging on the Thermo-mechanical Properties of Polyimide and Polyimide-silica Hybrids[J]. J. Mater. Sci., 2007, 42(19): 8363-8369.

[7] Oba M. Effect of Curing Accelerators on Thermal Imidization of Polyamic Acids at Low Temperature[J]. J. Polym. Sci. Polym. Chem., 1996, 34(4): 651-658.

[8] Jin Z X, Ishii H. A Novel Positive-Type Photosensitive Polyimide Based on Soluble Block Copolyimide Showing Low Dielectric Constant with a Low-Temperature Curing Process[J]. J. Appl. Polym. Sci., 2006, 100(5): 4240-4246.

[9] Nelson A, Guerra G, Williams D J, et al. Catalytic Activity of Benzimidazole in the Imidization of Polyamic Acids[J]. J. Appl. Polym. Sci., 1988, 36(1): 243-248.

[10] Ding Y, Bikson B, Nelson J K. Polyimide Membranes Derived from Poly(amic acid) Salt Precursor Polymers. 1. Synthesis and Characterization[J]. Macromolecules, 2002, 35(3): 905-911.

[11] Ahn T, Choi Y, Jung H M, et al. Fully Aromatic Polyimide Gate Insulators with Low Temperature Processability for Pentacene Organic Thin-film Transistors[J]. Org. Electron., 2009, 10(1): 12-17.

[12] Shirai Y, Tokiwa S, Kawauchi T, et al. Influence of Additives on the Imidization of Poly(amide acid)[J]. J. Photopolym. Sci. Technol., 2012, 25(3): 389-393.

[13] Rusanov A L, Komarova L G, Sheveleva T S, et al. New Aryloxy-Substituted Condensation Polymers[J]. React. Funct. Polym., 1996, 30(1-3): 279-292.

[14] Huang W, Yan D, Lu Q. Synthesis and Properties of Polyimides from 1, 3-bis (4-piperidino-l, S-naphthalic anhydride) Propane[J]. Polym. Bull., 2003, 49(6): 417-423.

[15] Wang K, Fan L, Liu J G, et al. Preparation and Properties of Meltprocessable Polyimides Based on Fluorinated Aromatic Diamines and Aromatic Dianhydrides[J]. Appl. Polym. Sci., 2008, 107(15): 2126-2135.

[16] Rangel E R, Maya E M, Sanchez F, et al. Gas Separation Properties of Mixed-matrix Membranes Containing Porous Polyimides Fillers[J]. J. Memb. Sci., 2013, 447(15): 403-412.

[17] Marek M, Schmidt P, Schneider B, et al. Imidization of Polypromellitamic Acid Based on 4, 4’–Methylenedianiline[J]. Macromol. Chem. Phys., 1990, 191(11): 2631-2637.

[18] Xu Y, Wang S, Li Z, et al. Polyimide Fibers Prepared by Dry-spinning Process: Imidization Degree and Mechanical Properties[J]. J. Mater. Sci., 2013, 48(22): 7863-7868.

[19] Kailani M H, Sung C S P. Chemical Imidization Study by Spectroscopic Techniques. 2. Polyamic Acids[J]. Macromolecules, 1998, 31(17): 5779-5784.

[20] Brandom D K, Wilkes G L. Influence of Thermal Imidization on the Crystallization and Melting Behavior of the Aromatic Polyimide, LaRC CPI-2[J]. Polymer, 1995, 36(21): 4083-4089.

[21] Yoon J Y, Jeong S, Lee S S, et al. Enhanced Performance of Solution-Processed Organic Thin-Film Transistors with a Low-Temperature-Annealed Alumina Interlayer between the Polyimide Gate Insulator and the Semiconductor[J]. ACS. Appl. Mater. Interfaces, 2013, 5(11): 5149-5155.