Schlieren Imaging of Chemically-Induced Flow Instabilities During Step-Growth Polymerization

Schlieren imaging was used to observe the dependence on degree of reactivity on flow instabilities during step-growth polymerization. For example a solution of a 2,2'-(ethylenedioxy)- diethanethiol containing varying concentrations of Octylamine as initiator was used to displace a trimethylolpropane triacrylate monomer. The concentration of initiator was used to control the degree of reactivity of the solutions and therefore the Damkohler Number which is the ratio of the chemical to the hydrodynamic timescale. By varying the concentration of initiator and/or the functionality of the monomers, one can tune the reaction product from a viscous liquid, to gel, or even a solid. Resulting flow patterns were found to depend on degree of reactivity and effects were observed regardless of the direction of flow. Also observed was evidence of three-dimensional effects on the resultant flow patterns.