Synthesis and characterization of copolymers of limonene with styrene initiated by azobisisobutyronitrile

The radical copolymerization of limonene with styrene by azobisisobutyronitrile in xylene at 80 ± 0.1 °C for 2 h, under inert atmosphere of N2, yields alternating copolymers. The kinetic expression is Rp∝[I]0.5[Sty]1.0[Lim]−1.0. The overall activation energy is calculated as 41 kJ/mol. The FTIR and 1H-NMR spectra of copolymers show bands at 3000 and 1715 cm−1 and peaks at 6.8 δ and 5.3 δ due to phenyl protons of styrene and trisubstituted olefinic protons of limonene, respectively. The values of reactivity ratios r1(Sty)=0.0625 and r2(Lim)=0.014, calculated by Kelen–Tüdos method. The Alfrey–Price Q–e parameters for limonene are 0.438 and −0.748, respectively. The penultimate unit effect is favoured in the present system and the value of φ is 38.49.