摘要：The dependence of the glass transition in mixtures on mixing thermodynamics is examined by focusing on enthalpy of mixing, Δ Hmix with the change in sign (positive vs. negative) and magnitude (small vs. large). The effects of positive and negative Δ Hmix are demonstrated based on two isomeric systems of o - vs. m - methoxymethylbenzene (MMB) and o - vs. m - dibromobenzene (DBB) with comparably small absolute Δ Hmix . Two opposite composition dependences of the glass transition temperature, Tg , are observed with the MMB mixtures showing a distinct negative deviation from the ideal mixing rule and the DBB mixtures having a marginally positive deviation. The system of 1, 2- propanediamine (12PDA) vs. propylene glycol (PG) with large and negative Δ Hmix is compared with the systems of small Δ Hmix , and a considerably positive Tg shift is seen. Models involving the properties of pure components such as Tg , glass transition heat capacity increment, Δ Cp , and density, ρ , do not interpret the observed Tg shifts in the systems. In contrast, a linear correlation is revealed between Δ Hmix and maximum Tg shifts.
