Study on single and binary catalytic systems of pyridine‐imine catalysts based on nickel and iron in synthesis of reactor blends and low‐density polyethylene nanocomposites

Abstract

In the presence of modified methylaluminoxane as cocatalyst, the behavior of a binary catalytic system based on pyridineimine nickel (N) and iron (F) catalysts was evaluated in order to reach a proper mixture of polyethylene (PE). A computational study along with kinetic profile suggested that the catalyst F with higher electron affinity (A) and electrophilicity (ω) in the methyl cationic active center and stronger interaction with the monomer led to high integrated monomer consumption and higher activity. In addition, the samples produced by the mixture of catalysts showed a higher value of M v [19.4 × 10 4 g (PE) mol (Fe+Ni) −1 h −1 )], melting point (127.8 C), and crystallinity extent (41.29%) than the samples produced by the single catalysts. The addition of multiwalled carbon nanotubes (MWCNT) into the polymerization media reduced the activity of catalysts [from 7.50 × 10 4 to 0.66 × 10 4 g (PE) mol (Fe+Ni) −1 h −1 ] and the thermal properties of the low-density polyethylene nanocomposite samples. However, the sample containing 2.33% MWCNT 20-30 improved the total thermal stability of the neat polyethylene blend up to 400 C. Scanning electron microscope images of the samples demonstrated irregular to virtually uniform morphologies were obtained through the in situ and solution-mixing techniques.

Synthesised spirobichroman‐based polyimide functionalized by pyridine: Effects of substituent position on gas separation and thermal properties

“…Furthermore, each atom of the pyridine ring existed in a p orbital vertical to the plane, which formed a closed π structure. Hence, the pyridine structure showed aromaticity and resisted thermal degradation, caused by the ether bonds or aliphatic structures in the polymers . PI‐3 showed the lowest 5% decomposition temperature in a N 2 atmosphere, probably because it contained the flexible ether bond, and the bond energy of the aliphatic structure was lower when the substituted methyl group was in the ortho ‐position of the amino group .…”

“…Hence, the pyridine structure showed aromaticity and resisted thermal degradation, caused by the ether bonds or aliphatic structures in the polymers. 35,36 PI-3 showed the lowest 5% decomposition temperature in a N 2 atmosphere, probably because it contained the flexible ether bond, and the bond energy of the aliphatic structure was lower when the substituted methyl group was in the ortho-position of the amino group. 34 On the contrary, the 5% thermal decomposition temperature of PI-2 was the highest.…”