Highly Transparent Aromatic Polyamides from Unsymmetrical Diamine with Trifluoromethyl Groups.

Seong Jong Kim,Taejoon Byun,Jongho So,Inah Kang,Sang Youl Kim

doi:10.3390/polym14030501

Seong Jong Kim, Taejoon Byun + Show 3 more

Open Access

https://doi.org/10.3390/polym14030501

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Journal: Polymers	Publication Date: Jan 27, 2022
Citations: 3	License type: CC BY 4.0

Affiliation: Korea Advanced Institute of Science and Technology

Abstract

Soluble and transparent wholly aromatic polyamides (PAs) were synthesized from an unsymmetrical diamine monomer having trifluoromethyl (CF3) groups, 4-(4′-aminophenoxy)-3,5-bis(trifluoromethyl)aniline. The monomer was polymerized with several dicarboxylic acid monomers via the Yamazaki–Higashi polycondensation method. All of the synthesized polyamides have an amorphous morphology, and they are soluble in many polar organic solvents at room temperature. Flexible and transparent films of the polyamides were prepared by solution casting and these polymer films show good optical transparencies with cut-off wavelengths of 337–367 nm and transparencies of 88%–90% at 550 nm. In addition, all the polymers were thermally stable over 400 °C and exhibited glass transition temperatures (Tg) higher than 300 °C. Unsymmetrically inserted trifluoromethyl groups on polyamides improves the solubility as well as the transparency of the polymers while maintaining good thermal properties. They also showed low refractive indices around 1.5333~1.5833 at 633 nm owing to the existence of low polarizable trifluoromethyl groups.

Highlights

The strong demand for portable/wearable electronic devices with various form factors requires the development of unprecedented display devices as a key element for the realization of the next-generation devices, and transparent polymeric materials are receiving great attention because they can replace rigid glass substrate for transparent and flexible display [1,2]
Commonly used transparent polymeric materials, including poly(ethylene terephthalate) (PET), poly(ethylene naphthalate) (PEN) and polycarbonate (PC), are found to be inappropriate to use as substrate materials for flexible organic light-emitting diode (OLED) displays mainly because it cannot withstand the fabrication conditions currently employed for thin film transistor (TFT) manufacturing [3,4]
Fluorinated polyamides were synthesized from the unsymmetrical diamine monomer having CF3 groups

Summary

Introduction

The strong demand for portable/wearable electronic devices with various form factors requires the development of unprecedented display devices as a key element for the realization of the next-generation devices, and transparent polymeric materials are receiving great attention because they can replace rigid glass substrate for transparent and flexible display [1,2]. The glass transition and melting temperatures (Tg , and Tm ) of the aforementioned polymer films are not high enough for TFT fabrication process [8]. PI films often show an intense color because of their rigid, highly conjugated aromatic structure and inherent capability to form a so-called intermolecular charge-transfer (CT) complex between electron-deficient dianhydride and electron-rich diamine units [11,12]. To overcome these problems, various structural modifications have been attempted on PIs [10,13,14,15,16,17,18]

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