Reactivity ratio determination for the terpolymerization of poly(2-EHA-MMA-St)

The physical, chemical and mechanical properties of polymers depend on the micro-structural characteristics of the macromolecular chains. The reactivity ratio gives a clear idea about the mean composition of the polymer, the sequence distribution of monomers, and rate of polymerization. The reactivity ratio is a kind of kinetic parameter and is defined as the ratio of the propagation rate constant for one monomer to that of another. Traditionally, reactivity ratio estimation using linearization techniques were used instead of non-linear parameter estimation methods because of lack of computational power. The linear estimation of copolymerization reactivity ratio led to distorted error structure. Previously, only low conversion data could be used, along with the Error-in-Variables Method, which is a non-linear parameter estimation technique that considers the error present in all variables. To be able to handle medium or high conversion data in determination of reactivity ratio for terpolymerization, DNI-EVM approach has been used. The terpolymer DNI-EVM approach requires three compositions to be run to high conversion, each rich in one monomer. After assembling the apparatus and performing the degassing process in order to release oxygen gases dissolved in the solution, the polymerization process was performed in the range of 0-25% conversion level. Examining the peaks resulting from 1H-NMR spectroscopy became challenging due to the overlap between the peaks related to PEHA and PMMA with three residual monomers for the region of 1.70 - 1.95 and 3 - 4.35. It is suggested to carry out additional experiment such as the pure PMMA, PSt., PEHA runs to full conversion also, 33.3/33.3/33.3 composition fully converted polymer sample and the three 80mol% compositions to full conversion.