Thermo-Processable Polyimides with HighTg and High Thermo-Oxidative Stability as Derived from 2,3,3′,4′-biphenyltetracarboxylic dianhydride

Abstract

Aromatic copolyimides were prepared using 2,3,3′,4′-biphenyltetracarboxylic dianhydride (asymmetric BPDA or a-BPDA) and several aromatic diamines with flexible ether linkages to obtain melt-processable polyimides (PIs) with balanced properties, i.e. high Tg, high thermo-oxidative stability, low melt viscosity, and sufficient toughness. The use of a-BPDA for the present purpose is based on our previous results which showed that a-BPDA-based PIs always show both higher Tg and much higher thermoplasticity than the corresponding symmetric BPDA-derived PIs. On the basis of the structure–property relationship, a copolyimide system was focused upon as a promising candidate. The molecular weight of the selected copolyimide was controlled using an end-capping reagent to balance between Tg, the melt viscosity, and toughness. The effect of the polymerization route (one-pot and two-step) on the properties was also discussed. An a-BPDA-based copolyimide accomplished a high Tg at 249 °C, a low melt viscosity of 8200 Poise at 400 °C, and high thermo-oxidative stability concurrently with considerably high film toughness (elongation at break = 66%).

Low-CTE Polyimides Derived from 2,3,6,7-Naphthalenetetracarboxylic Dianhydride

“…C for 24 h, W denotes the weight of PI films which were immersed in water at 25 C for 24 h and wiped with a tissue paper.…”

“…Because of its poor PAA polymerizability under the common conditions, 1,4,5,8-NTDA-based polyimides are usually prepared by the one-pot polymerization technique, 19 which is conducted at elevated temperatures in the presence of bases such as picoline as a catalyst for imidization and toluene or xylene to azeotropically remove water coming from imidization. 25 However, even if a homogeneous solution consisting of a 1,4,5,8-NTDA-based PI soluble in common organic solvents is available via the one-pot technique, it is not applicable to the present purpose since the in-plane orientation of PI chains as a primary factor for low CTE characteristics can be induced by thermal imidization of PAA films. 13 Thus, the difficulty of PAA polymerization using 1,4,5,8-NTDA prevents the applications to adhesive-free (two-layered) FCCL, again emphasizing considerably high polymerizability of 2,3,6,7-NTDA.…”

“…Thus, s-BPDA/PDA and TPDA/PDA containing these stiff units are also known as low-CTE PIs in contrast to sterically distorted 2,3,3 0 ,4 0 -BPDA (a-BPDA)-derived PIs. [25][26][27] Figure 2 illustrates the backbone structures of typical low-CTE polyimide systems.…”

Synthesis of phthalic end-capped copolyimides and their adhesive properties

“…Since the 1980s, polyimides based on asymmetric a-BPDA have been developed to produce polyimides with relatively lower melt viscosities and higher glass transition temperatures (T g ) that surpass the corresponding polyimides derived from the symmetric BPDA. [33][34][35] This behavior is presumably due to the non-flexible structure and the significantly distorted and bent chain structure in a-BPDA. This provides a promising way to prepare the polyimides with high thermal stability without detracting from the processing characteristics.…”

Novel High Temperature Polypyrrolones with Asymmetric Biphenyl Moieties in the Main Chain: Synthesis and Characterization

“…For example, polyimides derived from a unique asymmetric dianhydride, 2,3,3 0 ,4 0 -biphenyl tetracarboxylic dianhydride (a-BPDA), exhibited high solubility in organic solvents, low melting viscosity at elevated temperatures, and, at the same time, high thermal stability. Thus, a-BPDA-based polyimides have been widely used as high temperature composites, [11][12][13] coatings, [14] and other functional materials in many high-tech fields. As part of our continuous work in developing high performance PPys materials for electronics, two new asymmetric PPys derived from a-BPDA and aromatic tetraamines were developed in the present work.…”