A new unsymmetrical and noncoplanar diamine containing trifluoromethyl and trimethyl groups, 1,4‐bis(4‐amino‐2‐trifluoromethylphenoxy)‐2,3,5‐trimethylbenzene ( 2 ), was synthesized using 2,3,5‐trimethylhydroquinone and 2‐chloro‐5‐nitrobenzotrifluoride as starting materials. A series of fluorinated poly(ether imide)s (PEIs) ( 4a–4d ) were prepared from diamine 2 with four aromatic dianhydrides via a one‐step high‐temperature polycondensation procedure. The obtained PEIs were readily soluble in most organic solvents and could be solution‐cast into flexible and strong films. The resulting thin films exhibited light color and good optical transparency with a cutoff wavelength of 356–376 nm. They also displayed good thermal stability with glass transition temperatures (Tg) above 281°C, 10% weight loss temperatures in the range of 482–486°C, and the weight residue more than 55% at 800°C in nitrogen. Moreover, they revealed low dielectric constants (2.77–2.93 at 1 MHz) and low moisture absorptions (0.41%–0.57%). 相似文献
A new aromatic diamine containing trifluoromethyl and methyl groups, namely α,α‐bis(4‐amino‐3‐methylphenyl)‐4‐(trifluoromethyl)phenylmethane ( 1 ), was synthesized from 2‐methylaniline and 4‐(trifluoromethyl)benzaldehyde. A series of fluorinated polyimides (PIs) were prepared from the diamine with four commercially available aromatic tetracarboxylic dianhydrides using a one‐step high‐temperature polycondensation procedure. These obtained PIs showed excellent solubility, with the dissolvability at a concentration of 10 wt% in most solvents, and they could afford flexible and strong films. Thin films of these PIs exhibited high optical transparency and light color, with the cutoff wavelength at 324–357 nm and transmittance higher than 74% at 450 nm. Moreover, these PIs possessed eminent thermal stability and good mechanical properties. 相似文献
In view of the increasing significance of technology‐driven devices such as microelectromechanical systems, energy‐harvesting devices, and organic field effect transistors, polymer electret materials with durable electret performance at elevated temperatures become more and more important. However, typical polymer electret materials lose their performance at elevated temperatures. To provide polymer materials with improved electret performance over a broad temperature range, a series of aromatic polyimides with different degree of fluorosubstitution is presented. Isothermal surface potential decay measurements at elevated temperatures reveal that minor differences in the chemical structure have a major influence on the electret behavior. The best performance is found for the polyimide containing a hexafluoroisopropylidene moiety in both the bisanhydride‐ and the diamine‐based unit. Excellent long‐term charge storage stability at 120 °C is observed. From the initial surface charge 94% remains after 24 h. This polyimide even tolerates short‐term exposure of 30 s at 300 °C with almost no loss of performance. These findings demonstrate that this particular polyimide is suitable for device applications at elevated temperatures during fabrication and use.
Abstract A series of novel polyimides was synthesized from alicyclic diamines and various aromatic dianhydrides by one-step polymerization in m-cresol without a catalyst. The polymerization was conducted for 4 hours with refluxing, which was enough to obtain the polymers with high molecular weight. The inherent viscosities of the resulting polyimides were in the range of 0.30 ~1.29 dL/g. The prepared polyimides showed excellent thermal stabilities and good solubility. All the polymers were readily soluble in common organic solvents such as chloroform, tetrachloroethane (TCE), dimethylacetamide (DMAc), etc and the glass transition temperatures were observed at 199 to 311°C. UV-visible spectra were obtained to measure the transparency of polymer films. All the polymers showed high transmission above 90% in the wavelength of 400 ~700 nm. 相似文献
Fully‐atomistic molecular dynamics (MD) simulations have been carried out to model helium transport through four different glassy polyimides. While the polymer matrices had been pre‐validated, specific parameters and combination rules were used here in order to describe helium‐helium and helium‐polymer interactions. Gas permeabilities are in very good agreement with experimental evidence. Two ways to decrease chain cohesion and improve gas transport were considered – the replacement of an ODPA by a bulky BCDA dianhydride, and the substitution of a site on an ODA diamine by a CF3. The fluorinated polyimide appears to be the most promising material with more heterogeneity in the void‐space distribution, the highest model permeability and fewer constraints from an experimental point of view.
Two kinds of soluble polyimides were synthesized from 4,4′‐diamino‐3,3′‐dimethyldiphenylmethane (DMMDA) and two dianhydrides (including BTDA, ODPA) via a two‐step method, low temperature solution polycondensation and next chemical imidization. All polyimides were readily soluble in common polar solvent, such as DMF, DMAc and NMP. The polyimides were characterized by FT‐IR, NMR, DSC, XRD and EA. The results showed that all of the polyimides revealed an amorphous nature and their inherent viscosities were 0.68–0.96 dlg?1. The glass transition and melt temperature of these polyimides were determined by DSC and ranged from 224–283°C and 372–384°C, respectively. Thermogravimetric analysis indicated that these polyimides remained fairly stable up to a temperature around or below 400°C. Moreover, 10% mass losses were recorded at approximately 525°C in nitrogen atmosphere. They had a tensile strength in the range 89–137 MPa, and elongations breaking at around 10%. The pervaporation properties of the prepared polyimide dense membranes for ethanol/water mixtures were investigated at a different temperature and the average value of the separation factor and total permeation flux were 46–108 and 660–1380 g/m2h, respectively. 相似文献
A variety of options exists for lithographically defining polyimides for microelectronics applications. The two investigated here, photosensitive polyimide and wet etching of low-stress polyimides, offer lower cost, higher throughput solutions compared with dry etch processes. Via sizes of less than 25 μm and film thicknesses of greater than 14 μm are difficult to process using these techniques: however, for applications such as interlayer dielectrics for high-density packaging or solder masks for flip chip die attachment, these limitations may not be insurmountable. Photosensitive polyimide can be patterned with fewer steps, but the overall quality of the film in terms of surface planarity and residual stress is not as good as wet etching of conventional polyimide. 相似文献
A new aromatic diamine monomer containing pyridine unit, 2,6-bis (4-aminophenoxy- 4'-benzoyl)pyridine(BABP), was synthesized in three steps, starting from 2,6-pyridinedicarboxyl chloride. A series of novel pyridine-containing polyimides were prepared v/a the polycondensation of BABP with various aromatic dianhydrides through poly(amic acid) precursors, and thermal or chemical imidization of the precursors. The polyimides exhibit desirable properties, e.g., good solubility in N-methyl-2-pyrrolidone and m-cresol, excellent thermal stability and film-forming capability, as well as high inherent viscosity, indicating high molecular weight. 相似文献
Summary: A new diamine monomer containing a crown ether was made to react with commercial diacid chlorides and dianhydrides to yield new aromatic polyamides and polyimides. The crown ether moiety was introduced as a pendant group so that the polymers showed enhanced solubility in organic solvents, good thermal properties (high transition temperatures and high thermal stability), and good film‐forming ability.
The new aromatic polyamides and polyimides bearing a benzo‐15‐crown‐5‐pendant group synthesized here. 相似文献