Isomeric Biphenyl Polyimides. (I) Chemical Structure-property Relationships

Abstract

A series of polyimides (PIs) were prepared from three biphenyltetracarboxylic dianhydrides (BPDA) isomers, i.e., 3,3′,4,4′-BPDA (s-BPDA), 2,3,3′,4′-BPDA (a-BPDA), and 2,2′',3,3′'-BPDA (iBPDA) with various diamines through the conventional two step process. Polymerization reactivity, solubility, and dynamic mechanical properties (T g, softening behavior, and storage modulus at glassy state) were compared between PIs derived from these BPDA isomers and para/meta diamine isomers. The solubility in NMP increased as follows: i-BPDA-PI > a-BPDA-PI > s-BPDA-PI. The order is attributed to semi-crystalline and fully amorphous morphologies of s-BPDA-PI and other isomeric BPDA-PIs, respectively. The use of meta-diamines lowered the T g whereas the use of bent/distorted BPDA isomers enhanced the T g (s-BPDA-PI < a-BPDA-PI < i-BPDA-PI). The BPDA isomer effect on T g is based on the difficulty of obtaining internal rotation around the biphenyl linkages. The width of the DMA rubbery plateau region decreased in the order of i-BPDA < a-BPDA-PI < s-BPDA-PI, depending on the crystallinity and the extent of chain entanglement. In a-BPDA and i-BPDA-PI systems, PIs from metadiamines led to higher modulus than the corresponding PIs from para-diamines.

Melt processable homo- and copolyimides with high thermo-oxidative stability as derived from mixed thioetherdiphthalic anhydride isomers

“…The a-BPDA/ meta-diamine-based PIs showed a higher storage modulus measured by DMA as well as a higher tensile modulus. This phenomenon may be explained by a mechanism that a segment containing the meta-linkages can take a more extended conformation form than that containing the para-linkages [7][8]. However, this tendency is hard to distinguish in copolyimides based on mixed-TDPA, which may be attributed to that additional monomers disrupt the conformational consistency resulting in the loss of tensile modulus.…”

“…It was reasoned that introduction of the monomers containing asymmetric or noncoplanar structure to replace the linear symmetrical dianhydride in polymer chain could weaken the interchain interaction thus enhancing the solubility and melt flowability [6]. As of result of that, it has been further demonstrated that replacement of the symmetrical dianhydride in PIs with asymmetric ones decreases the melt viscosity but increases the T g relative to the corresponding symmetrical PIs [4,[7][8][9]. Thioetherdiphthalic anhydride (TDPA) is an aromatic bridged dianhydride which has three isomers as shown in Figure 1.…”

Novel Asymmetric Aromatic Polyimide Having Excellent Space Environmental Stability and Application for Solar Sail “IKAROS” Membrane

“…Moreover, a large drop was clearly apparent in the E' curve of PI(a-ODPA/4,4'-ODA) above Tg with a short rubbery plateau. As in the BPDA based PI systems [4], these observed behaviors are attributed to the rotational inflexibility and irregular geometry of asymmetric ODPA, which means that this asymmetric polyimide can be heat-sealable in the temperature region > 340℃.…”

“…In addition, the asymmetric PIs indicate higher thermoplasticity than that of the corresponding symmetric PIs based on their nonplanar biphenylimide structures inhibiting intermolecular interaction (no ordered structure formation). Consequently, the sterically bent/distorted but rotation-restricted structural unit induced by asymmetric aromatic monomers was strongly anticipated for development of new high-performance polyimides [3,4]. We have also invented asymmetric aromatic addition-type imide oligomers (TriA-PI: a-BPDA/4.4'-ODA/PEPA) having high Tg and good processability [5].…”

Preparation of Nanopatterned Polyimide by Imprinting and Curing Phenylethynyl- terminated Imide Oligomer

“…The mold patterns could not be imprinted sufficiently due to the low mobility. Upilex-R polyimide shows high modulus of 10 7 Pa even at 370 ℃, which is much higher than the Tg [11]. Figure 1.…”