Activation Energy and Thermodynamic Parameters of Cyclization in Purified Natural Rubber Latex Using a Trimethyl Silyl Triflate

Abstract

The property of natural rubber (NR) is more interesting, except for some properties which need to improve. The cyclization reaction is an interesting reaction for modified NR to thermoplastic elastomer. The kinetic cyclization of deproteinized natural rubber (DPNR) or purified NR latex effectively performed in latex phase by using trimethylsilyl-trifluoromethane sulphonate or trimethyl silyl triflate (TMSOTF) is studied at various temperatures and times. The cyclized products are confirmed by NMR spectroscopies including one and 2D NMR. The kinetic of cyclization is investigated. It is found that the degree of cyclization in DPNR is a function of cyclization conditions. The rate constant (k) is 200 (s-1) at 100°C based on 95% of regression and the activation energy of cyclization in DPNR latex is 147.66kJ/mol. Some thermodynamic parameters: enthalpy, entropy, and free energy activation of 144.6kJ/mole, -269.11J/mole, and 246.9kJ/mole, respectively, are obtained for the cyclization of DPNR. The kinetic and thermodynamic parameters of cyclization obtained from this study indicate that an increase in the process temperature would increase the rate of cyclization formation.