Fragment Parameters for the Calibration of Molecular Weights of Rodlike Oligomers/Polymers by Gel Permeation Chromatography

Molecular weights for rodlike polymers determined by the gel permeation chromatography (GPC) method are in general inflated when polystyrene references are used. In this paper, we have established a set of new empirical parameters, χi, of commonly used fragments including a range of different substituted thiophenes, benzenes, pyridines, ethylenes, ethynylenes as well as butadienes for the calibration of the inflated Mn data obtained by GPC measurements for rodlike oligomers/polymers. The χi parameters are accessed by adjusting the slopes of the plots of Mn relative to the real molecular weights, Mr, for a series of oligomers/polymers of different structural varieties to approximately 1. The calibrated molecular weights, Mc, are calculated based on the equation, Mc = [Σ χiFi]Mn, where Fi stands for the percent of the total number of fragment Φi in an oligomer/polymer, which matches nicely with the Mr of oligomers/polymers. More than 84% of the calibrated Mc values are within 12% deviation from the real mol...