Synthesis and characterization of phosphorus- and sulfur-containing aromatic polyimides for high refractive index

• Published in: Polymer (Guilford) 2018-01, Vol.136, p.143-148
• Main Authors: Kim, Hyeonil, Ku, Bon-Cheol, Goh, Munju, Yeo, Hyeonuk, Ko, Heung Cho, You, Nam-Ho
• Format: Article
• Language: English
• Subjects: Anhydrides; Aromatic polyimide; Birefringence; Chemical synthesis; Decomposition; Dianhydrides; Glass transition temperature; High refractive index; Optical polymer; Optical properties; Phosphine; Phosphine oxide; Phosphorus; Polyimide resins; Polymers; Refractivity; Studies; Substitution reactions; Sulfur; Thermal decomposition; Thermal properties; Thermal resistance; Thermodynamic properties; Transition temperatures; Transparency; Transparent polyimide
• ISSN: 0032-3861; 1873-2291
• DOI: 10.1016/j.polymer.2017.12.052

A new diamine, bis(4-((4-aminophenyl)thio)phenyl)(phenyl)phosphine oxide (BATPO), containing phosphine oxide and thioether bonds was prepared via the Grignard reaction to dichlorophenylphosphine oxide with 4-fluorophenylmagnesium bromide, followed by an aromatic substitution reaction with 4-aminothiophenol. The polyimides (PIs) were synthesized by the conventional two-step polycondensation from several aromatic dianhydrides, such as 4,4’-[p-thiobis(phenylenesulfanyl)]diphthalic anhydride (3SDEA), 4,4’-(hexafluoroisopropylidene)diphthalic anhydride (6FDA), 4,4′-oxydiphthalic anhydride (ODPA) and pyromellitic dianhydride (PMDA) with the BATPO. The synthesized PIs exhibited outstanding thermal properties including high thermal decomposition temperatures (>500 °C) and glass transition temperature (Tg) in the range of 212–295 °C, and optical transparency at 450 nm of over 80% for films of ca. 10 μm thickness. In particular, 3SDEA-BATPO exhibited a high refractive index (1.725) with low birefringence (0.0087) due to the heavy atom effect of the high sulfur and phosphorous contents in the polymer main-chain. This paper represent synthesis and characterization of highly refractive polyimides containing phosphine oxide and thioether unit in the polymer chains. The polyimides (PIs) were synthesized by the conventional two-step polycondensation from several aromatic dianhydrides, such as 4,4’-[p-thiobis(phenylenesulfanyl)]diphthalic anhydride (3SDEA), 4,4’-(hexafluoroisopropylidene)diphthalic anhydride (6FDA), 4,4′-oxydiphthalic anhydride (ODPA) and pyromellitic dianhydride (PMDA) with the BATPO. The polymers exhibited high thermal properties such as glass transition temperature (>212 °C), and 5% weight loss temperature at >502 °C under nitrogen. The polymers also showed good optical properties, including high optical transparency in the visible region, a low birefringence and high refractive indices at 637 nm. [Display omitted] •A new diamine for high performance polyimde containing phosphine oxide and thioether bonds was prepared.•PIs exhibited high refractive index due to the heavy atom effect of the high sulfur and phosphorous contents.•Particularly, 3SDEA-BATPO exhibited the highest refractive index (1.725) with low birefringence (0.0087).