Polymer Characterization during Continuous Flow Synthesis

The ability to characterize polymers in solutions during synthesis will transform materials design and synthesis strategies. Here, we demonstrate how to use scaling of semidilute polymer solutions to determine evolution of the chain weight average degree of polymerization, N_w, undergoing the step-growth polymerization. The developed approach takes advantage of the scaling relationship between the solution correlation length ξ=lg^ν/B and number of monomers g per correlation volume for polymers with monomer projection length l. The B-parameter and scaling exponent ν defining chain statistics at different length scales assume values B_g, B_th and 0.588, 0.5, respectively. Specifically, the combination of these parameters and the relationship between viscosity, monomer concentration c and N_w provides mean for in-line determination of the time evolution of the weight-average molecular weight of the poly(urethane) during the continuous-flow polymerization in tetrahydrofuran. This approach reduces the time for obtaining the weight-average degree of polymerization for a given polymer/solvent pair to a matter of seconds, enabling the quality control and rapid optimization of the synthesis process.