Investigation of thermal, antibacterial and heavy metal ion removal behavior of polyamide/polyimide iron oxide nanocomposites

In this study, a newly-designed diamine (DA) containing pyridine and carbazole groups was synthesized and the relevant polyamides (PAs) and polyimides (PIs) were prepared by polymerization reaction between the DA monomer and terephthalic acid, adipic acid, and pyromellitic dianhydride. In addition, polymer nanocomposites were prepared through a combination of the synthesized polymers with modified magnetite iron oxide nanoparticles. The synthesized compounds were fully characterized by hydrogen nuclear magnetic resonance (1HNMR), fourier-transform infrared (FTIR), field emitting scanning electron microscopy (FESEM), energy dispersive X-Ray (EDX), Transmission electron microscopy (TEM), Differential scanning calorimetry (DSC) and Thermogravimetric analysis (TGA) analyses. All of the synthesized properties of compounds such as thermal stability, viscosity, elimination capability of heavy metals ions adsorption, and antibacterial activity were investigated. Polyamides and PI showed good solubility in aprotic solvents and the viscosity was in the range of 0.72–0.89 dL/g. Also, the glass-transition temperature (Tg) of synthetic polymers was in the range of 214–273°C and 10% weight loss temperatures (T10%) for the synthesized compounds were in the temperature range of 280–492°C in N2, and the percentage of residual ash between 61 and 74%. The adsorption rate of Hg2+, Co2+, Pb2+, Cr2+, and Cd2+ metal ions by PA containing terephthalic acid (PAT) and its nanocomposite (NCPAT) showed that nanocomposite has a better performance compared to PAT. The highest and lowest removal efficiency was related to Hg2+ and Pb2+ ion, respectively. Finally, antibacterial test results against Gram-positive and Gram-negative bacteria showed favorable inhibitory effects of all the synthesized polymers.

New fluorinated poly(pyridine amide)s derived from 2,6-bis(4-iodophenyl)-4-(4-trifluoromethylphenyl)pyridine by C–N coupling reaction

2,6-Bis(4-iodophenyl)-4-(4-trifluoromethylphenyl)pyridine, as a new aromatic diiodide compound, was synthesized through a one-pot protocol by the sequential diazotization-iodination of 2,6-bis(4-aminophenyl)-4-(4-trifluoromethylphenyl)pyridine with KI/NaNO2/ p-TsOH in acetonitrile at room temperature. A number of new aromatic fluorinated poly(pyridine amide)s containing 2,6-diphenyl-4-(4-trifluoromethylphenyl)pyridine units were prepared via a Pd(PPh3)2Cl2 catalyzed carbonylation polymerization of this diiodide, diamines and carbon monoxide in DMAc in the presence of PPh3 and 1,8-diazabicyclo[5,4,0]-7-undecene. These new polyamides with inherent viscosities of 0.63–0.72 dL/g were amorphous and easily soluble in amide type aprotic solvents such as NMP, DMAc, DMF and dimethyl sulfoxide at room temperature. Thermal analysis data up to 800°C in nitrogen showed their high thermal behavior with 5% weight loss temperature of 428–498°C and char yield of 62–69%. Their limiting oxygen index of 42.3–45.1 showed that the resulting poly(pyridine amide)s could be classified as “self-extinguishing polymers”. Also, their thin films exhibited high optical transparency with a cut-off wavelength of 324–373 nm.

Synthesis and characterization of new aromatic copoly(ether amide)s bearing 4-trifluoromethylphenyl-2,6-diphenylpyridyl moieties in the main chain

A series of new aromatic fluorinated copoly(ether amide)s containing 4-(4-trifluoromethylphenyl)-2,6-diphenylpyridyl moiety with high molecular weight were prepared by a low-temperature solution polycondensation of terephthaloyl chloride with 4-(4-trifluoromethylphenyl)-2,6-bis(4-aminophenyl)pyridine and 1,4-bis(4-amino-2-trifluoromethylphenoxy)benzene with various mole ratios of the two monomers ranged from 20/80 to 80/20. All polymers were amorphous and soluble in common organic solvents such as N-methyl-2-pyrrolidone, N,N-dimethylacetamide and tetrahydrofuran at room temperature or upon heating at 70oC, and could be solution cast into transparent, tough, and flexible films with tensile strengths of 66.9–80.2 MPa, tensile moduli of 1.84–2.03 GPa, and elongations at break of 11.8–20.7%. These new polyamides displayed good thermal stability with gradually increasing of glass temperatures of 259–285oC as an increase of the 4-(4-trifluoromethylphenyl)-2,6-diphenylpyridyl component, the temperature at 10% weight loss of 476–505oC, and the residue of 55–61% at 750oC in nitrogen. They also exhibited low dielectric constants of 3.11–3.38 (1 MHz), low moisture absorption in the range of 1.43–1.75%, and high transparency with an UV–vis absorption cut-off wavelength in the 350–368 nm range.