Thermo-analytical study on transitions in styrene–maleic anhydride copolymers with low- and high-molecular weights

• TGA, DSC and M-DSC data.
• Influences molecular weight and amount maleic anhydride.
• Complex molecular structure and thermal data for high-molecular weight SMA.
• Linear Fox theory for copolymers with polymer chain segments of different compositions.

The thermal behaviour near the glass transition temperature Tg was studied for poly(styrene-co-maleic anhydride) or (SMA) copolymers with a broad range of molecular weight (Mw = 5500–180,000 g/mol) and amount of maleic anhydride (22–50 mol%). The influences of molecular structure for low- and high-molecular weight copolymers were detailed by using thermogravimetric analysis (TGA), differential scanning calorimetry (DSC) and temperature modulated differential scanning calorimetry (TMDSC). Data from TGA provide evidence for variations in thermal stability, mainly over the first degradation step up to 350 °C. Most interesting data results from TMDSC for high-molecular weight SMA, where the transition in reversible heat flow and Δcp remains almost constant, while the transition in non-reversible heat flow and Δcp gradually increases with amount MA. Comparing low- and high-molecular weight SMA, a linear model for Tg cannot be applied for the global amount of maleic anhydride, while it can be successfully implemented if a more detailed molecular structure with two constituents is considered. As such, further evidence is provided for the intrinsic heterogeneous molecular structure of high-molecular weight SMA with “styrene-rich” and “maleic-anhydride-rich” polymer segments.

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