Effect of feed rate of end-capping molecules on structure of hyperbranched polymers formed from monomers A2 and B4 in semibatch process

Abstract

Hyperbranched polymers that were prepared by the polymerization of monomers A2 and B4 with the gradual addition of the end-capping molecules AR to the reactor were studied using a kinetic model. The degree of polymerization (DP) and fraction of branch points (FB) under various compositions and feed rate parameters (ϕ) were calculated using a generating function method. The growing profile of the reduced weight-average DP (DPw∗) dependent on the conversion of group B, α(B), in a semibatch process was different from that in a batch reactor. At the same composition of the reactants, the DPw∗ of HBPs prepared under a lower addition rate of AR was higher than that at a quicker feed rate or in the batch process. Either a lower ratio of AR (λ1) or a higher ratio of A2 (λ2) could increase the DPw∗. According to the proposed model, the HBPs without the gel fraction could be obtained at high conversion via the continuous addition of AR to the reactor. For example, the HBPs with a high weight-average DP approximately 478, could be obtained with ϕ=0.1; λ1=2.68; and λ2=0.66 at α(B)=α(A)=0.95 in the semi-batch process, and the DB and FB of the HBP were 0.987 and 0.238, respectively. On the contrary, the DPw∗ was only 45 in a batch system at the same composition of reactants.