Soluble Polyimides Bearing (cis, trans)-Hydrogenated Bisphenol A and (trans, trans)-Hydrogenated Bisphenol A Moieties: Synthesis, Properties and the Conformational Effect

Abstract

In this work, hydrogenated bisphenol A (HBPA) based dinitro mixed isomers (1a′ and 1a) were synthesized and separated via vacuum distillation under the monitor of DSC and 1H NMR. Corresponding diamines (2a′ and 2a) were separately polycondensed with five commercial dianhydrides via a two-step thermal imidization to obtain PI-(1′-5′) and PI-(1-5). All the polyimides could afford flexible, tough, and transparent films, and most of them were readily soluble not only in common polar solvents like DMAc, but also in low boiling point solvents such as chloroform. 1H NMR spectra of the polyimides demonstrated that HBPA moiety showed no conformation changes during the preparation of polymers. For a given dianhydride, PI-(1-5) exhibited better thermal stability than that of PI-(1′-5′), this can be attributed that the equatorial, equatorial C–O in PI-(1-5) promoted denser and more regular molecular chain stacking, as can be evidenced by the WAXD and geometric optimization results. Additionally, when the dianhydride was ODPA, BPADA or 6FDA, no apparent difference was found in either the transmittance or solubility between two series of polyimides, which could be attributed that twisted and flexible ether linkages, as well as bulky substituents, led to the “already weakened” inter- and intramolecular CT interaction and cohesive force. However, when it came to rigid and stiff dianhydride, e.g., BPDA, PI-3′ took an obvious advantage over PI-3 in transmittance and solubility, which was possibly owed to the larger molecular chain d-spacing imparted by equatorial, axial C–O. An overall investigation of PI-(1′-5′) and PI-(1-5) on aspects of thermal, mechanical, morphological, soluble and optical performance values was carried out, and the conformation effects of HBPA isomers on the properties of two series of polyimides were discussed in detail.

The spirobichroman-based polyimides with different side groups: from structure–property relationships to chain packing and gas transport performance

“…To understand the contribution of gas diffusivity ( D ) and solubility ( S ) to CO 2 and CH 4 transport behaviour in polymer membranes, the diffusivity and solubility of CO 2 and CH 4 were calculated by the time-lag method. 34 As displayed in Table 5 , the diffusivity of gas in different polymer membranes decreases in the order 6FDA-FH > 6FDA-MH > 6FDA-DH, which is consistent with the trends for FFV and d -spacing of the polymers ( Table 3 ). Compared with the CO 2 solubility and diffusivity of 6FDA-FH and 6FDA-DH, the CO 2 diffusivity of 6FDA-FH is significantly higher than that of the 6FDA-DH.…”

“…According to Flory's theory, the factors influencing the T g of polymers are the rigidity of the polymer molecular chains and the interactions. 34 In this regard, 6FDA-MH has a bulky substituent in the form of the –CH 3 group, which increases the flexibility of the polymer chain. Hence, the T g of 6FDA-MH is the lowest among the three polymers, whereas 6FDA-DH had the highest T g , which is attributed to the strongest interactions between the molecular chains in all synthesised polymers.…”

Synthetic strategies for highly transparent and colorless polyimide film

“…The H″BPDA‐PI's transmittance is higher than that of H'BPDA‐PI when the dianhydride with planar aromatic structure, such as BTDA and BPDA, is polymerized with H'BPDA and H″BPDA, respectively. The reason for that is axial bond can increase the chains distance and thus weaken the formation of CTCs 108 …”

Soluble Biobased Polyimides from Diaminotruxinic Acid with Unique Bending Angles

“…As such, numerous studies have been conducted to design soluble and processable polyimides. One of the strategies to improve the solubility of polyimides is the introduction of bulky side chains, , flexible linkages, , and bending structures into their main chain for better flexibility of the polymer chains. , However, modifications to the chemical structures decrease the heat resistance of these materials. The introduction of isomeric bending structures to polymer chains is considered an effective approach to improve the solubility and processability of polymers.…”