Physical Aging Behavior of a Glassy Polyether

Abstract

The present work aims to provide insights on recent findings indicating the presence of multiple equilibration mechanisms in physical aging of glasses. To this aim, we have investigated a glass forming polyether, poly(1-4 cyclohexane di-methanol) (PCDM), by following the evolution of the enthalpic state during physical aging by fast scanning calorimetry (FSC). The main results of our study indicate that physical aging persists at temperatures way below the glass transition temperature and, in a narrow temperature range, is characterized by a two steps evolution of the enthalpic state. Altogether, our results indicate that the simple old-standing view of physical aging as triggered by the α relaxation does not hold true when aging is carried out deep in the glassy state.

Physical aging of selenium glass: Assessing the double mechanism of equilibration and the crystallization process

“…when the gap between T g and T a is more and more important. This behavior has been already observed in literature [27][28][29] . We may note that the rejuvenated curve is perfectly superimposed to the others in both glass and liquid states, which is the expected calorimetric response when only physical aging occurs.…”

Maximum Possible Cooling Rate in Ultrafast Chip Nanocalorimetry: Fundamental Limitations Due to Thermal Resistance at the Membrane/Gas Interface

“…Thus, the cooling rate R of the hot zone of the membrane depends on the heat transfer parameter α = λ/r 0 at L t r 0 l m f p . Typically, nitrogen gas or helium gas is used to cool the membrane [10][11][12][13][14][15][16][17][18][19][20][21][22][23][24][25][26]. In differential scanning calorimetry, the calorimetric cell loaded with the sample and the reference unloaded cell are maintained at the same temperature T(t) in the central hot zone; this temperature is controlled at the desired scanning rate R(t).…”

“…Ultrafast membrane-based nanocalorimetry opens up exciting opportunities for materials science [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15]. This calorimetry makes it possible to measure the size-dependent properties of nanosized samples [1,5,9] and films as thin as about 0.1 nm [2,3], as well as measure the melting and synthesis characteristics of a single-layer lamella [7,8], and directly measure the desorption of polymer chains [12].…”

“…For several sensors of different size and geometry, it was shown that the maximum possible controlled cooling rate is proportional to the ratio λ/r 0 , where λ is the thermal conductivity of the surrounding gas and r 0 is the radius of the central hot zone of the membrane [23][24][25][26]. The possibility of increasing the maximum cooling rate with decreasing r 0 has been successfully used in many experiments [10][11][12][13][14][15][16][17][18][19][20][21][22][23][24][25][26]. The goal of this article is to answer the question: what is the maximum possible cooling rate in such experiments if r 0 tends to zero?…”

Maximum Possible Colling Rate in Ultrafast Chip Nanocalorimetry: Fundamental Limitations Due to Thermal Resistance at the Membrane/Gas Interface

“…Ultrafast membrane-based nanocalorimetry opens up exciting opportunities for materials science [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15]. Indeed, ultrafast calorimetry allows nano-and microsamples to be heated or quenched at extremely high, controlled rates, creating non-equilibrium states under well-defined conditions, and to study the kinetics of phase transitions on a submillisecond time scale.…”