Molar mass directly governs polymer properties, yet its routine measurement remains slow, offline, and largely confined to dilute solution conditions. This limitation restricts the rapid structure–property mapping needed for data-driven materials discovery and emerging self-driving laboratory workflows. Here we integrate semidilute polymer solution theory with practical in-line measurement to enable rapid determination of polymer weight-average molar mass (Mw) at concentrations typical of polymerization and processing (i.e., above the overlap concentration, c*). Building on modern scaling concepts that treat semidilute solutions as strings of correlation blobs, we establish a quantitative calibration linking solution specific viscosity to Mw for a concentration range c > c*. This framework allows Mw to be determined for unknown samples using a conventional rheometer in as little as 2 min. We implemented the same viscosity to Mw calibration under continuous flow by converting real-time pressure drop in a tubular module into solution viscosity and hence Mw. Together, the theory-grounded calibration and its flow-compatible implementation provide a practical route to rapid, Mw readout in a semidilute solution regime, enabling high-throughput synthesis and characterization workflows for materials development.
Rapp et al. (Tue,) studied this question.