Syntheses and characterizations of high refractive index and low birefringence polyimides containing spirobifluorene in the side chain. (19th May 2017)

• Record Type: Journal Article
• Authors: Wen, Pushan; He, Rui; Li, Xiang-Dan; Lee, Myong-Hoon
• Is Part Of: Polymer. Volume 117(2017)
• Page Start: 76
• Page End: 83
• Publication Date: 2017-05-19
• Subjects: Spirobifluorene -- Thermal stability -- Transparency -- Refractive index -- Birefringence; Polymers -- Periodicals; Polymerization -- Periodicals; Polymères -- Périodiques; Polymérisation -- Périodiques; 547.7
• DOI: 10.1016/j.polymer.2017.04.020
• Languages: English
• ISSNs: 0032-3861

Abstract

Abstract: Two new diamine monomers having a spirobifluorene structure were synthesized through four steps, and polymerized with three different dianhydrides (PMDA, CBDA and 6FDA) to obtain six polyimides with spirobifluorene structure in the side chain. All the resulting polyimides displayed excellent thermal stability and high glass transition temperature. These polyimides synthesized from CBDA and 6FDA showed good solubility in typical organic solvents such as NMP, DMF and DMSO. Transparent and flexible cast films can be obtained from soluble polyimides or poly(amic acid) solution. The transmittance of polyimide films was higher than 90% in the visible wavelength range (higher than 80% in case of polyimide containing PMDA). The refractive indices of the result polyimides were found to be in the range from 1.6343 to 1.7007, which is higher than that of normal polymers. In addition, the optical birefringences of these polyimides were extremely low (0.0005–0.0014). The high refractive index and low birefringence of these polyimides as well as other descent physical and thermal properties would offer them possible applications in high performance optical materials such as flexible substrates. Graphical abstract: Novel polyimides containing 9, 9′-spirobifluorene unit in the side chain, which exhibit high transparency, high refractive index and low birefringence, have been developed as promising candidates for advanced optical applications. Highlights: Novel polyimides containing 9, 9'-spirobifluorene unit in the side chain were synthesized. The polyimides exhibit high thermal stability (T5 > 420 °C) with excellent optical properties such as high transparency (>90% at 400 nm), high refractive index (1.6342–1.7007) and low birefringence (0.0005–0.0014). The resulting polymer materials could be promising candidates for advanced optical applications.