On the Precise Determination of Molar Mass and Dispersity in Controlled Chain-Growth Polymerization: A Distribution Function-Based Strategy

Abstract

Accurate information for the molar mass of polymers is a critical item in polymerization kinetic investigation and precision polymer synthesis. Size exclusion chromatography (SEC) is an irreplaceable technique to determine molar mass averages based on conventional calibration, which may nonetheless lead to inaccurate results due to the dissimilarity between the sample and the standard polymer. Herein, a facile distribution function-based strategy was proposed for the precise determination of molar mass average properties, aiming at rectifying the deviation of the standard-equivalent results from the true values. The number-average molar mass (Mn) can be recalculated involving the contribution of each molar mass component beyond the fundamental Mark–Houwink–Sakurada relation. In addition, the as-developed strategy is capable of converting the dispersity from the apparent to the true value, thereby re-estimating the uniformity of the rectified molar mass distribution. The strategy was successfully applied to the linear polymers with medium and low dispersities obtained by two well-controlled chain-growth polymerizations: reversible addition-fragmentation chain transfer polymerization and ring-opening metathesis polymerization, respectively. The rectified Mn closely match the benchmarks (i.e., absolute/theoretical Mn), showing a much higher accuracy than those conventionally calibrated SEC results. Attributing to the consideration of dispersity, the errors of the rectified results can be as low as zero. This work reduces the risk of experimental bias caused by conventionally calibrated SEC analysis to acquire precise mechanism insight and realistic polymerization process details.