We describe herein the state of the art following the last 8 years of research into aromatic polyamides, wholly aromatic polyamides or aramids. These polymers belong to the family of high performance materials because of their exceptional thermal and mechanical behavior. Commercially, they have been transformed into fibers mainly for production of advanced composites, paper, and cut and fire protective garments. Huge research efforts have been carried out to take advantage of the mentioned characteristics in advanced fields related to transport applications, optically active materials, electroactive materials, smart materials, or materials with even better mechanical and thermal behavior.

Functional Aromatic Polyamides

Two diimide-diacid monomers 4,4′-bis[4″-(trimellitimido)phenyl isopropylidene-4″′-phenoxy]diphenyl sulfone and 4,4′-bis[4″-(trimellitimido)phenylisopropylidene-4″′-phenoxy] were synthesized. The structures of the monomers were characterized by FT-IR and 1H-NMR spectroscopy. A series of novel poly(amide-imide)s were prepared from this two diacids and aromatic diamines through phosphorylation reaction. The PAIs were characterized by FT-IR, 1H-NMR, XRD, TGA, and DSC, solution viscosity, solubility test and electrical properties. Poly(amide-imide)s showed excellent solubility due to the presence of flexible groups and isopropylidene unit in the polymer backbone. They also exhibited good thermal stability and the temperatures at which 10% weight loss occurred in the range 385–465 °C. These PAIs found to have a dielectric constant in the range 3.25–4.20 at 10 kHz and have excellent electrical insulation character and can be used as insulation materials for electrical items operating at elevated temperatures.

Synthesis of new diacid monomers and poly(amide-imide)s: study of structure–property relationship and applications

Synthesis and properties of multi-block semi-alicyclic polyimides for thermally stable transparent and low CTE film

New triptycene-containing polyamides were prepared from 1,4-bis(4-carboxyphenoxy)triptycene with aromatic diamines or from 1,4-bis(4-aminophenoxy)triptycene with aromatic dicarboxylic acids via the phosphorylation polyamidation reaction. These polyamides were essentially amorphous and showed a significantly increased solubility as compared with their analogs without the triptycene units. All the polyamides could be solution-cast into flexible and tough films. They also showed good thermal stability with glass transition temperatures of 252–295 °C and 10 % weight loss temperatures higher than 540 °C. These polyamides are considered to be promising processable high-temperature polymeric materials.

Synthesis and characterization of novel organosoluble and thermally stable polyamides bearing triptycene in their backbones

A novel unsymmetrical diamine monomer 4-(2-(4-(4-aminophenoxy)phenyl)propan-2-yl)benzenamine (APPBA) containing –O– and –C(CH3)– groups was synthesized from 2-(4-aminophenyl)-2-(4-hydroxyphenyl)propane and 4-nitrofluorobenzene by the nucleophilic substitution reaction followed by catalytic reduction. Polycondensation of this diamine with aromatic dianhydrides through thermal solution imidization techniques afford a series of novel processable polyimides (PI). The structure of the monomer and polyimides were confirmed by FT-IR and 1H-NMR. The polyimides were characterized by XRD, TGA, DSC, electrical property, solution viscosity and solubility test. These polyimides had inherent viscosities in the range 0.48–0.61 dL/g. The X-ray diffraction measurements indicated that all these polyimides were amorphous. The polyimides exhibited excellent solubility in most of the organic solvents. The glass transition temperature (Tg) was observed in the range 242–282 °C. The polyimides displayed good thermal stability and the temperatures at which 10 % weight loss occurred in the range 475–504 °C. The dielectric constant of PIs was in the range of 2.82–3.55.

Synthesis of new unsymmetrical diamine and polyimides: structure–property relationship and applications of polyimides

Three aromatic diamines, 2,2′-diiodo-4,4′-oxydianiline (DI-ODA 2), 2,2′-bis[p-(trifluoromethyl)phenyl]-4,4′-oxydianiline (BTFP-ODA 3) and 2,8-diaminodibenzofuran (DADBF 5) were synthesized by using 4,4-oxydianiline (4,4′-ODA) as the starting material. New aromatic polyamides 6, 7 and 8 were prepared from these three diamines and six commercially available aromatic diacids by direct polycondensation, respectively. Polyamides 6 and 7 contained bulky iodide and p-trifluoromethylphenyl substitutents that would hinder the chain packing and increase the free volume. They exhibited good optical transparency in visible light region and showed excellent solubility in organic solvents such as DMSO, DMAc, DMF and NMP. Polyamides 8 containing planar dibenzofuran moieties had the highest glass transition temperatures and decomposition temperatures among these polyamides. Polyamides 6 had the lowest decomposition temperatures due to the presence of weak carbon–iodine bond. All of these polyamides showed amorphous nature evidenced by wide angle X-ray diffraction. No endothermic peaks were observed from DSC thermograms up to their decomposition temperatures. High optical transparency and excellent solubility combined with good thermal stability make these polyamides attractive for potential soft electronics applications.

Synthesis and characterization of aromatic polyamides derived from various derivatives of 4,4’-oxydianiline

To improve the optical transparency and organosolubility of aromatic polyimides derived from 4,4′-oxydianiline (4,4′-ODA), two new aromatic diamines, 2,2′-diiodo-4,4′-oxydianiline (DI-ODA) and 2,2′-bis[(p-trifluoromethyl)phenyl]-4,4′-oxydianiline (BTFP-ODA) were synthesized by using 4,4′-ODA as a starting material. Novel polyimides were prepared from these two diamines with various commercially available aromatic dianhydrides via a one-step high-temperature polycondensation procedure. Most of these polyimides showed enhanced solubility in common organic solvents compared with those corresponding polyimides derived from 4,4′-ODA. Especially, polyimide derived from BTFP-ODA and rigid pyromellitic dianhydride (PMDA) was also soluble in DMF, DMAc, DMSO, NMP, and m-cresol at room temperature. These polyimides had inherent viscosities from 0.41 to 1.26 dLg−1 in NMP or m-cresol at 30°C. Transparent, flexible, and tough films can be obtained by casting from their DMAc or m-cresol solutions. These films had the UV onset wavelengths in the range of 347–391 nm and the wavelengths at 80% transmission of 445–544 nm, indicating high optical transparency. They also exhibited good thermal stability with glass transition temperatures in the range of 260–327°C. The decomposition temperatures of these polyimides at 5% weight loss under nitrogen were 429–609°C. Because of the weak carbon-iodine bond, polyimides derived from DI-ODA decomposed at lower temperatures than polyimides derived from BTFP-ODA. The effects of the substituents at the 2 and 2′ positions of 4,4′-ODA on the properties of polyimides are also discussed. High optical transparency and good solubility combined with high thermal stability make these polyimides potential candidates for soft electronics applications. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011

Sheng-Wen Huang

Papers

Synthesis and characterization of aromatic polyamides derived from various derivatives of 4,4’-oxydianiline

Highly transparent and organosoluble polyimides derived from 2,2′-disubstituted-4,4′-oxydianilines

Vacancy-enhanced Mo-N2 interaction in MoSe2 nanosheets enables efficient electrocatalytic NH3 synthesis