Ferrari C, Tombari E, Salvetti G, Johari G P
Istituto per i Processi Chimico-Fisici del CNR, via G. Moruzzi 1, 56124 Pisa, Italy.
J Chem Phys. 2007 Jul 14;127(2):024903. doi: 10.1063/1.2752169.
The real and imaginary components of the complex heat capacity, C(p) (') and C(p) ("), and C(p,app) have been measured in real time during the linear chain polymerization on 12 K/h heating of six different (partially) polymerized states of a stoichiometric mixture of cyclohexylamine and diglycidyl ether of bisphenol A. Their C(p,app) shows a sigmoid shape rise with different onset temperatures T(onset), which is followed by a deep exotherm as the viscosity decreases and further polymerization occurs at different rates. The rates of their enthalpy decrease on polymerization determined by subtracting C(p) (') from C(p,app) differ but C(p) (') and C(p,app) of their final states are the same. The relaxation time increases with polymerization and decreases with an increase in T. C(p) (') rises in a sigmoid shape manner, and C(p) (") shows a peak when the relaxation time of the polymerized state is equal to the inverse of the temperature modulation frequency, whether polymerization occurs or not. The unrelaxed or vibrational heat capacity C(p,vib) of the polymers at T>T(onset) is close to C(p) of their glassy state at T<T(onset), showing that C(p) difference between the equilibrium liquid and its glass is mostly configurational. This contradicts a calculation showing that C(p,vib) change of a polymer at T(g) is generally approximately 20% of the total C(p) change.
在对环己胺与双酚A二缩水甘油醚化学计量混合物的六种不同（部分）聚合状态以12 K/h的升温速率进行线性链聚合过程中，实时测量了复热容的实部和虚部C(p)(')和C(p)'')以及表观热容C(p,app)。它们的C(p,app)呈现出具有不同起始温度T(onset)的S形上升，随后随着粘度降低和进一步以不同速率发生聚合而出现深度放热。通过从C(p,app)中减去C(p)(')确定的它们在聚合时的焓降低速率不同，但它们最终状态的C(p)(')和C(p,app)是相同的。弛豫时间随聚合增加而增加，随温度升高而降低。C(p)(')以S形方式上升，并且无论是否发生聚合，当聚合状态的弛豫时间等于温度调制频率的倒数时，C(p)'')会出现一个峰值。在T>T(onset)时聚合物的未弛豫或振动热容C(p,vib)接近于其在T<T(onset)时玻璃态的C(p)，这表明平衡液体与其玻璃态之间的C(p)差异主要是构型上的。这与一项计算结果相矛盾，该计算表明聚合物在T(g)时的C(p,vib)变化通常约为总C(p)变化的20%。
