Sunbul D.,I.T.U. Fen Edebiyat Fakultesi |
Paril A.,I.T.U. Fen Edebiyat Fakultesi |
Alb A.M.,I.T.U. Fen Edebiyat Fakultesi |
Alb A.M.,Tulane University |
And 2 more authors.
Journal of Applied Polymer Science | Year: 2011
Reaction kinetics and composition of 4-vinylbenzenesulfonic acid sodium salt (VB)-acrylamide (Aam) copolymerization in 0.1M NaCl solution are investigated. Data obtained by the automatic continuous monitoring of copolymerization system, up to 80% conversion, are analyzed by an "error-in-variables method" developed for obtaining the reactivity ratios by on-line monitoring. Monomer reactivity ratios are found as r Aam = 0.085 Â± 0.020, rVB = 2.0 Â± 0.33. Although the terminal model describes the composition data well, it is seen to be inconsistent with the reaction rates. This discrepancy is attributed to implicit penultimate effects and using the recently developed calculation method, effective radical reactivity ratios are found as s VB = 0.26 and sAam = 0.027, and both composition and rate data fit the implicit penultimate model extremely well. On-line monitored data showed that in the reactions where the VB was completely consumed, the subsequent Aam homopolymerization was very rapid; thus, the reaction showed definitely two rate regimes, before and after VB depletion. Acrylamide take up rate also showed these two rate regimes. We conclude that low conversion results can be misleading and reactions must be monitored up to a high conversion for a robust control of composition and reaction kinetics. © 2010 Wiley Periodicals, Inc.
Paril A.,ITU Fen Edebiyat Fakultesi |
Giz A.,ITU Fen Edebiyat Fakultesi |
Catalgil-Giz H.,ITU Fen Edebiyat Fakultesi
Journal of Applied Polymer Science | Year: 2013
The possibility of controlling the composition of acrylic acid/acrylamide copolymers by controlling the pH and the ionic strength of the reaction medium is investigated. The reactivity ratios of charged monomers depend on the pH of the medium, acrylic acid is the more reactive monomer below pH 3 and acrylamide above pH 4. The working pH was set at 3.6, a candidate for the crossover point, where no composition drift is expected. Copolymerization kinetics is investigated at this pH at various ionic strengths and a reaction without composition drift up to 80% conversion was achieved. All the chains produced in this reaction contain 30% ± 3% acrylic acid. Copolymer conversions, molecular weights, and composition distributions were measured through Automatic Continuous Online Monitoring of Polymerization (ACOMP) system. The copolymerization data were analyzed by a recent error in variables method (EVM) and reactivity ratios are calculated. The results show that in salt free conditions, the reactivity ratios depend on the ionic monomer concentration (ionic strength) in addition to the pH of the reaction medium. The effect of polyelectrolytic interactions on the reactivity ratios and the resulting composition drift during the reaction, sequence length distribution, and Stockmayer bivariate distribution are discussed in detail. Copyright © 2012 Wiley Periodicals, Inc.