Determination of monomer reactivity ratios and thermal properties of poly(GMA-co-MMA) copolymers

In this study, the free radical copolymerization of glycidyl methacrylate (GMA) and methyl methacrylate (MMA) was investigated for the first time by solution free radical copolymerization in toluene at 80 °C using azobisisobutyronitrile as an initiator. The ¹H-NMR spectroscopy has been used for determining the copolymer composition. Monomer reactivity ratios (r values) were calculated by various linear least-square methods. According to the results, using the Kelen–Tüdös (KT) and extended Kelen–Tüdös (Ex KT) methods the r values were obtained as \( r_{\text{G}} = 1.528 \pm 0.168 \), \( r_{\text{M}} = 0.789 \pm 0.121 \), and \( r_{\text{G}} = 1.577 \pm 0.186 \), \( r_{\text{M}} = 0.783 \pm 0.129 \), respectively. The calculated monomer reactivity ratios showed the higher reactivity for GMA (r_G) compared to MMA (r_M). Furthermore, the findings demonstrated random or ideal behavior (\( r_{\text{G}} \cdot r_{\text{M}} \simeq 1 \)) for these copolymers. The monomers sequence distribution as probability of finding the multiple sequence distribution of the GMA and MMA units in copolymers was calculated and showed higher probabilities for GMA sequences. Thermogravimetric analysis of the copolymers had three degradation stages, and the main degradation occurred at third stage (340–456 °C) with 56% weight loss. Also, with regard to initial temperature of degradation and T₅₀, the thermal stability was improved 62% and 2.3%, respectively, by increasing MMA content in copolymer. These studies could uncover the underlying GMA–MMA composition in copolymer, shedding light on the future design of top-performing applications such as UV printing ink and resin industry.