High conversion copolymerization, 1. Kinetics of the copolymerization of styrene and maleic anhydride |
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Authors: | Jaroslav Barto ,Viera Va kov ,Viera Jurani
ov ,M ria Mlyn rov |
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Affiliation: | Jaroslav Bartoň,Viera Vašková,Viera Juraničová,Mária Mlynárová |
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Abstract: | The copolymerization of styrene (S) with maleic anhydride (MAn) in 1,4-dioxane at 60, 70 and 80°C up to high conversion (≈ 98%) was followed by differential scanning calorimetry. The rate of copolymerization increases up to 20 – 40% conversion of both monomers and then gradually decreases to zero. The increase in the copolymerization rate is more pronounced for equimolar ratios [S]/[MAn] as compared to ratios with an excess of S. For a given mole ratio of S and MAn the copolymerization rate in 1,4-dioxane is higher at higher total monomer concentrations and/or at higher temperatures. The heat of copolymerization is 81,6 kj · mol?1 for the equimolar [S]/[MAn] mixture. For mixtures with [S]/[MAn] > 1 the heat of reaction is between 70 and 80 kj · mol?1. The limitingconversion of styrene for [S]/[MAn] = 1 is about 98%, and for [S]/[MAn] > 1 it is a function of the [S]/[MAn] ratio. Assuming exclusively the formation of an alternating S/MAn copolymer the following relation is derived. for the ratio of the apparent rate constants of propagation k?p, and termination k?t. |
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