Structure and Properties of Novel Asymmetric Biphenyl Type Polyimides. Homo- and Copolymers and Blends

Abstract

Asymmetric biphenyl type polyimides (PI) were prepared by thermal imidization of polyamic acids (PAA) derived from 2,3,3‘,4‘-biphenyltetracarboxylic dianhydride (a-BPDA) and p-phenylenediamine (PDA) or 4,4‘-oxydianiline (ODA). The dynamic mechanical properties of these PIs were compared with those of the isomeric PIs derived from symmetric 3,4,3‘,4‘-biphenyltetracarboxylic dianhydride (s-BPDA). a-BPDA/PDA polyimide has a considerably bent chain structure compared to semirigid s-BPDA/PDA. Nevertheless, the a-BPDA/PDA film annealed at 350 °C showed a higher T g than the s-BPDA/PDA film prepared under the same conditions. When these PIs were annealed at 400 °C, a-BPDA/PDA exhibited an abrupt E‘ decrease at the T g (=410 °C) as well as the counterpart annealed at 350 °C, whereas s-BPDA/PDA showed no distinct T g in the E‘ curve. Similar annealing effects were also observed for the ODA systems. The unexpectedly higher T g's of a-BPDA-based PIs could be explained in terms of the more restricted conformational change through the crank shaft-like motion. The difference between the extents of the E‘ decrease at the T g for a- and s-BPDA-based PIs is attributed to the difference of the intensity of intermolecular interactions. The blends of s-BPDA/PDA with a-BPDA-based PI (80/20) and the corresponding copolyimide improved the insufficient thermal processability of homo s-BPDA/PDA without causing a decrease in T g. The results revealed that, for semirigid s-BPDA/PDA, a-BPDA-based PIs are better matrix polymers than s-BPDA/ODA.

Characterizations of polybenzoxazine modified with isomeric biphenyltetracarboxylic dianhydrides

“…The obtained high T g, DMA value of PBA-a:isomeric biphenyltetracarboxylic dianhydride copolymers can be attributed to the improved crosslink structure via ester carbonyl linkage between phenolic hydroxyl group of PBA-a and anhydride group of isomeric biphenyltetracarboxylic dianhydride as seen in FT-IR spectra and their high aromatic content from the presence of the dianhydrides in the copolymers network as well as hydrogen bonding between ester carbonyl group (C=O) or OH groups in a carboxylic acid and phenolic hydroxyl group (-OH) of the PBA-a. Moreover, the T g values of PBA-a copolymers measured by DMA displayed descending order on basis of both molecular packing and chain conformation such as semirigid s-BPDA and bent chain a-BPDA structures of isomeric biphenyltetracarboxylic dianhydrides [37,38]. In our experiments, the order of T g 's PBA-a: s-BPDA (266°C)"> PBA-a:a-BPDA (247°C)">"PBA-a: i-BPDA (239°C) was observed as similarly investigated in [23].…”

Molecular dynamics simulation on glass transition temperature of isomeric polyimide

“…If this motion can be observed, the polymer chain should have sufficient space (more free volume) and can complete this motion in a short time period (less relaxation time, it mainly depends on rigidity of a polymer chain). Nevertheless, these two factors can not be well discussed in the gas state [5,7], so it is necessary to find an appropriate method to investigate them in the bulk state. Yet, molecular dynamics (MD) simulation method provides a proper means to study bulk polymer at molecular scale.…”

Novel phenylethynyl-terminated PMDA-type polyimides based on KAPTON backbone structures derived from 2-phenyl-4,4′-diaminodiphenyl ether

“…However, the cured resin must exhibit a high T g , which might appear to be in contradiction with the processability for heat-resistant polymeric matrix resins. 11,12 Yokota and co-workers [13][14][15] previously reported ground-breaking thermoplastic PIs derived from asymmetric and nonplanar 2,3,3 0 ,4 0 -biphenyltetracarboxylic dianhydride (a-BPDA) that exhibited high T g and a large drop of the storage modulus (E 0 ) above T g as observed in dynamic mechanical analysis (DMA) measurements. These phenomena were found to be quite different from the symmetric PI derived from 3,3 0 ,4,4 0 -biphenyltetracarboxylic anhydride (s-BPDA).…”