Preparation and characterization of novel polyimide-silica hybrids: PREPARATION AND CHARACTERIZATION OF NOVEL POLYIMIDE-SILICA HYBRIDS

Poly(4,4′-oxydiphenylene-pyromellitimide) loaded by NH2-functionalized silica

In this research, silica nanopowder is surface modified via a facile urethanation reaction to obtain silicon dioxide (SiO2) nanoparticles possessing amine (NH2)-functionalized organic moieties. Poly(4,4′-oxydiphenylene-pyromellitimide) as one of the most widely used polyimides (PIs) is then uniformly loaded by these organically modified nanoparticles (approximately 5% by weight) during its synthesis process at the thermal cyclodehydration stage of the corresponding poly(amic acid) precursor. Amine-functionalized SiO2 nanoparticles (SiO2∼NH2) and the resulting PI-based nanocomposites (PI/SiO2 and PI/SiO2∼NH2) are thoroughly characterized by Fourier transform infrared spectroscopy, diffuse reflectance ultraviolet–visible, X-ray diffraction, and scanning electron microscopy. Thermogravimetric analyses/derivative thermogravimetry thermograms obviously show that about 22% (by weight) of the nano-SiO2 particles is formed by organic moieties. Moreover, the thermostability order is found to be PI/SiO2 > PI/SiO2∼NH2 > neat PI. The nanocomposite PI/SiO2∼NH2 shows a two-step thermal decomposition pattern; the first step is due to the scission of the organic part from the nanoparticles loaded. According to the slope changes of the differential thermal analyses curves, the first-order phase transition could be found at the thermal range of 300–400°C. This transition, however, is not so clear for PI/SiO2 and PI/SiO2∼NH2 nanocomposites due to the interaction of nano-SiO2 particles with PI matrix.

An investigation of physico-chemical properties of a new polyimide–silica composites

In the present study, a novel diamine 1,4-bis[4-(hydrazonomethyl)phenoxy]butane (4-BHPB) has been successfully synthesized by a facile method.

Synthesis and characterization of novel fluorosilicone polyimides with high optical transparency

To overcome insoluble and low transmittance of the traditional polyimides (PIs), two kinds of novel fluorosilicone PIs were prepared. First, 1,4-bis (4-amino-2-trifluoromethylphenoxy) benzene, compound 3a, and 4,4′-bis(4-amino-2-trifluoromethylphenoxy)diphenyl ether, compound (3b), with 2-chloro-5-nitrobenzotrifluoride and p-hydroquinone or 4,4′-dihydroxydiphenyl ether were prepared. Second, hydrosilylation of nadic anhydride (NA) with 1,1,3,3-tetramethyldisiloxane (TMDS) yielded 5,5′-(1,1,3,3-tetramethyl-1,3-disiloxanediyl) bisnorbornane-2,3-dicarboxylic anhydride, compound (4). Initially, the conditions of the synthesis reaction such as reaction temperature, catalyst dosage, molar ratio of TMDS/NA, and reaction time on yield of compound 4 by the single factor approach were studied. The optimal reaction conditions were reaction temperature: 90°C, catalyst dosage: 1 ml (Pt% = 0.37%), molar ratio of TMDS/NA: 1/1.8, and reaction time: 3 h. The yield was 74.6%. Finally, two kinds of new organosoluble, light-colored, and good thermal stable fluorosilicone PI compounds (5a-5b) were synthesized from compounds 3a-3b and 4 and 4,4′-hexafluoroisopropylidenediphthalic anhydride), prepared through a typical two-step polymerization method. The solubility of the novel fluorosilicone PI films of compounds 5a-5b and the traditional PI film (4,4′-diaminodiphenyl ether (ODA)-biphenyltetracarboxylic dianhydride, DIY) were contrasted. The result showed that the fluorosilicone PI films have good solubility. These PIs were soluble in amide polar solvents and even in less polar solvents. The glass transition temperatures of compounds 5a-5b were 229.1 and 186.7°C and the 5% and 10% weight-loss temperatures were 519.8°C and 539°C, respectively. These films had cutoff wavelengths of 331.8 and 318.6 nm. Due to these properties, these PIs could be used as aerospace, photoelectric, and microelectronic materials.