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

Abstract

The molecular‐weight dependence of the glass‐transition temperature (Tg) 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 (Mv) 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 (CONH2) and/or carboxylic acids (COOH) groups by alkali, was found to occur. The typical molecular‐weight dependence of the Tg in free‐radically prepared PAN was discussed in connection with a chain‐transfer mechanism in an aqueous medium.Molecular‐weight dependence of the Tg for PAN (WA). An error bar is given by a short vertical arrow.magnified imageMolecular‐weight dependence of the Tg for PAN (WA). An error bar is given by a short vertical arrow.

Influence of side chain structure on the thermal and antimicrobial properties of cationic methacrylic polymers

“…It is clearly observed in P(AN-co-MTZ) copolymers that T g decreases with the incorporation of MTZ in the macromolecular chain up to intermediate compositions from where the T g remains constant or slightly increases. The value obtained for T g of PAN is 98.5 °C, which is consistent with data reported in the literature with similar molecular weight [23]. In the case of PMTZ, the lateral chain imparts flexibility and then, its T g reached values below room temperature, 16.0 °C.…”

Influence of spacer group on the structure and thermal properties of copolymers based on acrylonitrile and methacrylic 1,3-thiazole and 1,2,3-triazole derivatives

“…From these plots is clearly observed in all the series the shift on T g to lower temperatures as MTA is incorporated in the macromolecular chain. The value obtained for T g of PAN is 89°C, which is consistent with data reported in the literature with similar molecular weight [23]. The variation of T g as a function of AN copolymer composition for all the series are plotted in Fig.…”

Thermomechanical behaviour of poly[acrylonitrile‐co‐(methyl acrylate)] fibres oxidatively treated at temperatures up to 180 °C

“…The latter decomposed, creating carbonyl groups that exhibited a shift at 210 ppm in the 13 C NMR spectra. According to the literature, the shifts at 177 ppm and 185 ppm occur mainly in alkali‐treated PAN and they were attributed to the carbonyl‐containing groups of acrylamide and carboxyl, respectively 28–31. Both these groups were created from the lateral nitrile groups.…”