Dissolution kinetics of poly(styrene-co-acrylonitrile) below and above its glass transition temperature
article
The dissolution behaviour of poly(styrene-co-acrylonitrile) (SAN) was examined across a broad temperature range to identify the governing thermodynamic and kinetic factors. Two high-boiling solvents with contrasting affinities for SAN, namely diethyl succinate (DS, RED = 0.69) and triethyl citrate (TC, RED = 1.37), were selected to study dissolution below and above the SAN glass transition temperature (Tg ≈ 105 ◦C). Isothermal mixing calorimetry (30–150 ◦C) showed complete SAN dissolution in DS above 45 ◦C, with exothermic dissolution enthalpies decreasing from 20 J g⁻¹ at 45 ◦C to 6 J g⁻¹ at 120 ◦C, the latter reflecting polymer–solvent interactions once the glassy-rubbery transition no longer contributes. In TC, SAN did not dissolve at 30 ◦C and was only partially dissolved up to 80 ◦C; complete dissolution occurred only above Tg, with an enthalpy of ~6 J g⁻¹ at 120 ◦C. ATR-FTIR monitoring revealed strong effects of solvent quality and temperature on induction time. SAN chains appeared in solution after 480 s in DS but after ~5000 s in TC at 45 ◦C, evidencing significant segmental relaxation limitation in TC. Above Tg, induction times sharply decreased to 120 s in DS and 360 s in TC at 120 ◦C. Isoconversional kinetic analysis showed that dissolution in DS above Tg is diffusion-controlled, with low acti vation energies (6–15 kJ mol⁻¹). Below Tg, SAN dissolution transitions from segmental-relaxation-controlled (increasing to 41 kJ mol⁻¹) to diffusion-controlled at higher conversion. Dissolution in TC below Tg exhibited even stronger relaxation control, with Ea reaching 116 kJ mol⁻¹ .
TNO Identifier
1023867
Source
Materials Today Communications(50), pp. 1-11.
Pages
1-11