Glass‐Transition Temperature ( T g ) of Free‐Radically Prepared Polyacrylonitrile by Inverse Gas Chromatography, 2 . Molecular‐Weight Dependence of T g of Two Different Types of Aqueous Polymers

The molecular‐weight dependence of the glass‐transition temperature ( T g ) of a series of atactic polyacrylonitriles (PAN)s was studied by inverse gas chromatographic (IGC) analysis. PANs having different molecular weights were prepared by either; (i) the addition of isopropyl alcohol as a chain‐transfer agent, or (ii) a scission reaction induced by the addition of alkali (NaOH) to a solution ( N , N ‐dimethylformamide solution, at 25 °C) of the resulting polymer. The intrinsic viscosity [ η ] was in the range of 10.9–0.1 (dl · g −1 ), which corresponds to a viscosity‐averaged molecular weight ( M v ) of 1 590 000–3 000. As part of the results, a side reaction, which saw the conversion of the nitrile (CN) groups of PAN into amide (CONH 2 ) and/or carboxylic acids (COOH) groups by alkali, was found to occur. The typical molecular‐weight dependence of the T g in free‐radically prepared PAN was discussed in connection with a chain‐transfer mechanism in an aqueous medium.Molecular‐weight dependence of the T g for PAN (WA). An error bar is given by a short vertical arrow.