Symmetric and asymmetric spiro-type colorless poly(ester imide)s with low coefficients of thermal expansion, high glass transition temperatures, and excellent solution-processability

• Published in: Polymer (Guilford) Vol. 169; pp. 167 - 184
• Main Authors: Hasegawa, Masatoshi, Takahashi, Shinya, Tsukuda, Soichi, Hirai, Tomoki, Ishii, Junichi, Yamashina, Yukari, Kawamura, Yoshinori
• Format: Journal Article
• Language: English
• Published: Kidlington Elsevier Ltd 15.04.2019; Elsevier BV
• Subjects: Bisphenols; Cardo structure; Coefficient of thermal expansion (CTE); Diamines; Dianhydrides; Display devices; Ductility; Glass transition temperature; Heat resistance; Heat-resistant plastic substrates; Optical transparency; Organic chemistry; Poly(ester imide)s; Properties (attributes); Solution processability; Solvents; Spiro structure; Substrates; Temperature; Thermal expansion; Thermal resistance; Transition temperatures; Xanthene; Spiro structure; Poly(ester imide)s; Solution processability; Coefficient of thermal expansion (CTE); Heat-resistant plastic substrates; Cardo structure; Optical transparency
• ISSN: 0032-3861; 1873-2291
• DOI: 10.1016/j.polymer.2019.02.020

In this work, we present several new poly(ester imide)s (PEsIs) with low coefficients of thermal expansion (CTE), excellent optical transparency, very high heat resistance (Tg), film ductility, and solution-processability. Symmetric and asymmetric spiro-type tetracarboxylic dianhydrides containing ester linkages (TA-s-Spiro and TA-a-Spiro) and diamines (AB-s-Spiro and AB-a-Spiro) were synthesized using xanthene-based isomeric bisphenols with a fluorenyl side group. The chemically imidized PEsIs were highly soluble in various common solvents including less polar non-amide solvents, and yielded stable solutions with high solid contents. The properties of the spiro-type PEsIs were systematically investigated and compared with those of the cardo-type counterparts. A PEsI derived from 1,2,3,4-cyclobutanetetracarboxylic dianhydride (CBDA), AB-a-Spiro, and 2,2′-bis(trifluoromethyl)benzidine (TFMB) achieved outstanding combined properties, i.e., a very low CTE (10.5 ppm K−1), excellent optical transparency (YI = 3.4, T400 = 80.8%), a very high Tg (351 °C) and solution-processability. Thus, the PEsIs are promising candidates as novel plastic substrates for use in image display devices. The isomer effects on the properties were also investigated and a possible mechanism for these effects is proposed. Solution casting of the material shown in the figure led to a colorless film with a low yellowness index (3.4), a considerably low coefficient of thermal expansion (10.5 ppm K−1), a very high Tg (351 °C), and a high tensile modulus (6.12 GPa). [Display omitted] •This work proposes novel symmetric and asymmetric spiro-type poly(ester imide)s (PEsIs).•The chemically imidized PEsIs were highly soluble even in less hygroscopic solvents.•Solution casting provided colorless films with a very low CTE and a very high Tg.•The PEsIs obtained are useful as novel high-temperature plastic substrates in display devices.