Abstract
In order to obtain highly optical transparency polyimides, two novel aromatic diamine monomers containing pyridine and kinky structures, 1,1-bis[4-(5-amino-2-pyridinoxy)phenyl]diphenylmethane (BAPDBP) and 1,1-bis[4-(5-amino-2-pyridinoxy)phenyl]-1-phenylethane (BAPDAP), were designed and synthesized. Polyimides based on BAPDBP, BAPDAP, 2,2-bis[4-(5-amino-2-pyridinoxy)phenyl]propane (BAPDP) with various commercial dianhydrides were prepared for comparison and structure-property relationships study. The structures of the polyimides were characterized by Fourier transform infrared (FT-IR) spectrometer, wide-angle X-ray diffractograms (XRD) and elemental analysis. Film properties including solubility, optical transparency, water uptake, thermal and mechanical properties were also evaluated. The introduction of pyridine and kinky structure into the backbones that polyimides presented good optical properties with 91–97% transparent at 500 nm and a low cut-off wavelength at 353–398 nm. Moreover, phenyl pendant groups of the polyimides showed high glass transition temperatures (Tg) in the range of 257–281 °C. These results suggest that the incorporating pyridine, kinky and bulky substituents to polymer backbone can improve the optical transparency effectively without sacrificing the thermal properties.
Highlights
Polyimides are well known for their excellent thermal stability, mechanical properties, chemical resistance, and electrical properties and have been used in the fields of adhesives, composites, fibres, films, and electronics [1,2,3,4,5,6,7]
Polyimides based on BAPDBP, BAPDAP, 2,2-bis[4-(5-amino-2-pyridinoxy)phenyl] propane (BAPDP) with various commercial dianhydrides were prepared for comparison and structure-property relationships study
Phenyl pendant groups of the polyimides showed high glass transition temperatures (Tg) in the range of 257–281 °C. These results suggest that the incorporating pyridine, kinky and bulky substituents to polymer backbone can improve the optical transparency effectively without sacrificing the thermal properties
Summary
Polyimides are well known for their excellent thermal stability, mechanical properties, chemical resistance, and electrical properties and have been used in the fields of adhesives, composites, fibres, films, and electronics [1,2,3,4,5,6,7]. The introduction of these groups often leads to the loss of thermal stability to some extent To overcome these problems, we designed and synthesized a series of novel polyimides based on pyridine. We have studied on the structure-property relationships of pyridine-polyimides containing –(CF3)2, –O–, –SO2–, –S–, –CO–, cyclohexane and biphenyl groups. These polyimides showed highly optical transparency, low dielectric constants, good thermal stability, excellent mechanical properties, respectively [25,26,27,28,29]. We prepared the polyimides using different diamines (BAPDBP, BAPDAP, BAPDP and 6FDA) as substituents in the backbone to investigate their effect on thermal stability, optical transparency, solubility, water uptake and mechanical properties. A series of polyimides were prepared from BAPDBP and three commercially available dianhydrides, and their properties were investigated for promising potential application
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