Thermal and microstructural analysis for methyl methacrylate homo‐ and copolymer with 1‐hexene made by dinuclear cobalt catalyst

Abstract

A dinuclear cobalt (II) (BC), was synthesized via a one‐step condensation reaction of isatin and 1,4‐phenylenediamine, followed by complexation with CoCl ₂ . The as‐prepared complex was used as catalyst in homo‐ and copolymerization of methyl methacrylate with 1‐hexene in presence of a modified methylaluminoxane (MMAO) as a cocatalyst. Effects of key polymerization parameters, including the cocatalyst to catalyst molar ratio, polymerization temperature, and reaction time, on catalytic activity were evaluated. The BC catalyst exhibited the highest activity 27.84 × 10 ³  g PMMA/mol Co. h at an [Al]/[Co] ratio of 1000:1 and 80°C, demonstrating excellent thermal stability and efficiency at relatively low cocatalyst loadings. ¹ H NMR analysis revealed that the PMMA sample prepared at 25°C showed the highest branching density (BD, 235 branches per 1000 C atoms), which decreased to 189 branches per 1000 C atoms with increasing temperature (from 25 to 90°C). Furthermore, gel permeation chromatography (GPC) results indicated a narrow molecular weight distribution (2.04), confirming the controlled nature of the polymerization. Moreover, differential scanning calorimetry (DSC) analysis revealed that increasing the polymerization temperature (from 25 to 90°C) resulted in a decrease in the glass transition temperature (from 131 to 114°C). In addition, scanning electron microscopy (SEM) images revealed that the best morphology control of the resulting PMMA was achieved at 90°C, with almost a spherical shape for PMMA. The results reveal that the BC catalyst offers high thermal stability, good control over polymer architecture, and great catalytic activity in the MMA polymerization.