Linearity limits of dynamic calorimetric response at the glass transition of polystyrene

Schawe, J.E.K.; Theobald, S.

doi:10.1016/s0022-3093(98)00660-7

Cited by 15 publications

(1 citation statement)

References 18 publications

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“…The curves have been shifted to join at low temperature and the T g 's determined are uncertain by ±0.2 K. Recognizing the heat flow step ∆H at T g as the material's caloric response, it is of interest to see its dependence on the applied excitation viz., the heating ramp q. Certainly the heat capacity C p (= −H/q) as the intrinsic coupling parameter (in terms of a generalized susceptibility 17,18) is meaningful only for the linear response case. For this purpose the heat-flow shift is plotted vs. the heating ramp in Fig.…”

Section: Resultsmentioning

confidence: 99%

Thermo-Kinetic Anomalies across Rigidity Threshold in GexSe1-x

Awasthi

Sampath

2002

Mater. Trans.

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We have investigated the glass-transition kinetics of nine Ge x Se 1−x glasses by differential scanning calorimetry. Relation between the drive (heating-rate q) and response (heatflow shift ∆H at T g ) is seen to be strictly linear only for GeSe 4 , known to signify the bulk-rigidity threshold for this series. From an Arrhenius analysis the activation energies for glassy relaxation are estimated, and point to the existence of different thermokinetic phases below and above the threshold composition. Series behaviour of the kinetic activation is conciled to a concurring one seen in the size of cooperatively diffusing regions. The anomalies are attributed to structural crossovers with Ge doping; first from the parent uniform Se-chains to that of backbones out-branching at corner-shared Ge(Se 1/2 ) 4 tetrahedral clusters, and subsequently interconnecting by edge-shared configurations to realize a random pearl-necklace 3-D covalent network.

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Section: Resultsmentioning

confidence: 99%