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

Add time:08/07/2019    Source:sciencedirect.com

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.

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