Synthesis and thermal analysis of poly(methyl methacrylate) oligomer functionalized polyethylene block copolymer

Abstract

Living oligomers of methyl methacrylate (MMA) were synthesized photochemically with iron(III) tris(oxalato) ferrate(III) tetrahydrate (Fe[Fe(C2O4)3]·4H2O) as photoinitiator under UV irradiation of 254 nm at 40 °C in dimethyl sulfoxide in the presence of triethylamine as coinitiator. The synthesized oligomers were incorporated in the ethylene chain by reverse atom transfer radical polymerization in N,N′-dimethylformamide using 2,2′-azobisisobutyronitrile as initiator with FeCl3/2,2′-bipyridine (bpy) catalyst system. FT-IR and 1H NMR analysis confirms the incorporation of pre-synthesized poly(MMA) in the ethylene chain. Thermogravimetric analysis of the copolymer shows a three step decomposition process with the major decomposition at approximately 380 °C. Apparent activation energy (E a) of each step was calculated using non-isothermal methods of Kissinger, Friedeman, Flynn–Wall–Ozawa (FWO) and modified Coats-Redfern (MCR). The E a value obtained from FWO and MCR methods shows good agreement and the value for the final step of decomposition was calculated to be 235 kJ mol−1. The conversion dependency of decompositions on the process rate can be best explained by Sestak-Berggren model which can be established as $$\begin{aligned} f(\alpha ) = 3.67 \times 10^{2} \exp \left( {\frac{-199.28}{RT}} \right)(1 - \alpha )^{2.03} \alpha^{3.03} \hfill \\ \hfill \\ \end{aligned}$$ with pre-exponential factor (A) = 3.67 × 102 min−1.