Conversion Factors for Polystyrene Molecular Weight into Molecular Weights of Polymethacrylates in Size Exclusion Chromatography

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Abstract
Relationships of molecular weights between polystyrene (PS) and several polymethacrylates, poly(methyl methacrylate) (PMMA), poly(ethyl methacrylate) (PEMA), poly(butyl methacrylate) (PBMA), poly(isobutyl methacrylate) (PIBMA), and poly(lauryl methacrylate) (PIMA), were examined. A conversion equation, was first defined, where s and t are constants, and Mps and Mpolymethacrylate are molecular weights of these polymers at the same retention volume. Conversion factors s and t for these polymethacrylates were estimated by using a PS calibration curve and corresponding polymethacrylates having broad molecular weight distributions. Pairs of s and t are as follows: 0.362 and 1.107 for PMMA; 0.2078 and 1.153 for PEMA; 0.01859 and 1.348 for PBMA; 1.727 and 0.978 for PIBMA; 21.64 and 0.746 for PLMA. These conversion factors are effective in the mobile phase of tetrahydrofuran at room temperature. By knowing these conversion factors and a PS calibration curve, molecular weight averages for these polymethacrylates can be calculated. Calibration curves for these polymers are demonstrated.