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Poly(ester imide)s possessing low coefficients of thermal expansion and low water absorption (IV): Effects of ester‐linked tetracarboxylic dianhydrides with longitudinally extended structures
Author(s) -
Hasegawa Masatoshi,
Saito Takayuki,
Tsujimura Yumi
Publication year - 2020
Publication title -
polymers for advanced technologies
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.61
H-Index - 90
eISSN - 1099-1581
pISSN - 1042-7147
DOI - 10.1002/pat.4756
Subject(s) - substituent , materials science , imide , crystallinity , thermal stability , alkyl , dielectric , elongation , absorption of water , absorption (acoustics) , polymer chemistry , analytical chemistry (journal) , medicinal chemistry , organic chemistry , ultimate tensile strength , composite material , chemistry , optoelectronics
A series of poly(ester imide)s (PEsIs) were prepared using longitudinally extended structures of ester‐linked tetracarboxylic dianhydrides with different numbers of aromatic rings ( N Ar = 4‐6). In the PEsIs obtained using p ‐phenylenediamine ( p ‐PDA), a clear trend was observed: the water absorption ( W A ) decreased with increasing N Ar . In contrast, no clear decrease in the T g with increasing N Ar was observed for the PEsIs obtained using 4,4′‐oxydianiline (4,4′‐ODA). The PEsIs obtained using a methyl‐substituted tetracarboxylic dianhydride ( N Ar = 5) showed more suppressed W A and higher elongation at break ( ε b ) values than those of the nonsubstituted counterparts. The former result is probably closely related to the enhanced crystallinity. However, methyl substitution caused an appreciable reduction in the thermal stability. Thus, the methyl‐substituted PEsIs did not meet the V‐0 standard in the UL‐94V test, unlike the substituent‐free counterparts. The PEsI copolymer obtained using the substituent‐free tetracarboxylic dianhydride ( N Ar = 6) with p ‐PDA (75 mol%) and 4,4′‐ODA (25 mol%) had excellent combined properties, ie, a very high T g (361°C), an ultralow coefficient of thermal expansion (2.2 ppm K −1 ), an extremely low coefficient of hygroscopic expansion (3.3 ppm/RH%), moderate film ductility ( ε b max = 23%), a moderate dielectric constant (3.22), and a low tan δ (2.76 × 10 −3 ) at 10 GHz in 50% relative humidity. Thus, this PEsI is a promising novel dielectric substrate material for use in the next generation of high‐performance flexible printed circuit boards.