Hasegawa, Masatoshi;Hori, Atsushi;Hosaka, Chisato;Ishii, Junichi published 《Poly(ester imide)s with low coefficients of thermal expansion ( CTEs ) and low water absorption ( VI ): an attempt to reduce the modulus while maintaining low CTEs and other desired properties》 in . The article was appeared in 《Polymer International》. They have made some progress in their research.SDS of cas: 2657-87-6 The article mentions the following:
Here, a challenging target in the development of high-temperature dielec. substrates was established: to significantly reduce the modulus of dielec. substrates while maintaining their low coefficients of thermal expansion (CTEs) and other desired properties, to suppress the spring-back force, which is generated in folded flexible printed circuit boards. An ester-linked tetracarboxylic dianhydride with an asym. and longitudinally extended structure (TA-HPBAHQ) exhibited good polymerizability with various aromatic diamines and led to the formation of poly(ester imide) (PEsI) precursors with sufficiently high mol. weights The thermally imidized TA-HPBAHQ-based PEsI films obtained using rigid diamines exhibited a very high glass transition temperature (Tg), ultralow CTE, suppressed water uptake and an extremely low coefficient of humidity (hygroscopic) expansion. In particular, the combination of TA-HPBAHQ and m-tolidine significantly lowered the modulus and improved the film ductility while maintaining a low CTE close to that of copper foil with other desired properties. In addition, a TA-HPBAHQ analog, TA-HNAHQ, containing a 2,6-naphthalene unit, was used. TA-HNAHQ-based PEsIs exhibited a further decreased modulus and other excellent properties similar to those of the TA-HPBAHQ-based systems except for the appearance of a β-transition in certain cases, depending on the diamines used. Certain selected PEsIs exhibited an extremely low tan δ at 10 GHz and a relatively good or the highest rank of flame retardancy. Thus, certain PEsIs examined in this study are promising candidates as new dielec. substrates required to exhibit a low CTE, suppressed modulus and other target properties for use in next-generation flexible printed circuit boards. 2022 Society of Industrial Chem. To complete the study, the researchers used 3-(4-Aminophenoxy)aniline (cas: 2657-87-6) .
3-(4-Aminophenoxy)aniline is one of ethers-buliding-blocks. Ethers feature bent C–O–C linkages. In dimethyl ether, the bond angle is 111° and C–O distances are 141 pm. The barrier to rotation about the C–O bonds is low. SDS of cas: 2657-87-6 The bonding of oxygen in ethers, alcohols, and water is similar. In the language of valence bond theory, the hybridization at oxygen is sp3.
Reference:
Ether – Wikipedia,
Ether | (C2H5)2O – PubChem