Preparation of Polymethylacrylic Acid Standard Samples for GPC Applications via a Precipitation Fractionation-Separated Step Hydrolysis Method

A series of polymethylacrylic acid (PMAA) standard samples were prepared from fractionated PMMA samples followed by a two-step hydrolysis. The six PMMA standard samples with narrow molecular weight distributions were produced by free radical polymerization and fractionated with toluene-petroleum ether. Their average molecular weights ranged from 3.1 × 103 to 4.3 × 104, dispersion coefficients were less than 1.5, and their gel permeation chromatography (GPC) peak shapes were symmetrical. The PMMA standard samples were dissolved in dioxane, and then hydrolyzed in a saturated NaOH-methanol solution for 24 h, the methanol then evaporated, and after that the PMMA samples were hydrolyzed in a 2 mol ·L −1 NaOH aqueous solution for 24 h. The 1H-NMR results showed that the two-step hydrolysis degree was higher than 98.70%. The PMAA standard samples were obtained after acidifying the hydrolysates, namely polymethacrylic acid sodium salt, and their molecular weights were constant during the separation process. The a...