Simulated glass-forming polymer melts: Glass transition temperature and elastic constants of the glassy state

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.

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Stochastic theory for the glassy state. 1. Influence of formation history on the glass transition temperature and equation of state

Macromolecules ◽

10.1021/ma00051a031 ◽

1992 ◽

Vol 25 (25) ◽

pp. 6921-6928 ◽

Cited By ~ 6

Author(s):

S. Vleeshouwers ◽

E. Nies

Keyword(s):

Glass Transition ◽

Transition Temperature ◽

Glass Transition Temperature ◽

Equation Of State ◽

Glassy State ◽

Stochastic Theory ◽

Formation History ◽

State 1

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Long-Term Physical (In)Stability of Spray-Dried Amorphous Drugs: Relationship with Glass-Forming Ability and Physicochemical Properties

Pharmaceutics ◽

10.3390/pharmaceutics11090425 ◽

2019 ◽

Vol 11 (9) ◽

pp. 425 ◽

Cited By ~ 4

Author(s):

Edueng ◽

Bergström ◽

Gråsjö ◽

Mahlin

Keyword(s):

Glass Transition ◽

Transition Temperature ◽

Glass Transition Temperature ◽

Physicochemical Properties ◽

Physical Stability ◽

Glass Forming Ability ◽

Melt Quenching ◽

Glass Forming ◽

Spray Dried

This study shows the importance of the chosen method for assessing the glass-forming ability (GFA) and glass stability (GS) of a drug compound. Traditionally, GFA and GS are established using in situ melt-quenching in a differential scanning calorimeter. In this study, we included 26 structurally diverse glass-forming drugs (i) to compare the GFA class when the model drugs were produced by spray-drying with that when melt-quenching was used, (ii) to investigate the long-term physical stability of the resulting amorphous solids, and (iii) to investigate the relationship between physicochemical properties and the GFA of spray-dried solids and their long-term physical stability. The spray-dried solids were exposed to dry (<5% RH) and humid (75% RH) conditions for six months at 25 °C. The crystallization of the spray-dried solids under these conditions was monitored using a combination of solid-state characterization techniques including differential scanning calorimetry, Raman spectroscopy, and powder X-ray diffraction. The GFA/GS class assignment for 85% of the model compounds was method-dependent, with significant differences between spray-drying and melt-quenching methods. The long-term physical stability under dry condition of the compounds was predictable from GFA/GS classification and glass transition and crystallization temperatures. However, the stability upon storage at 75% RH could not be predicted from the same data. There was no strong correlation between the physicochemical properties explored and the GFA class or long-term physical stability. However, there was a slight tendency for compounds with a relatively larger molecular weight, higher glass transition temperature, higher crystallization temperature, higher melting point and higher reduced glass transition temperature to have better GFA and better physical stability. In contrast, a high heat of fusion and entropy of fusion seemed to have a negative impact on the GFA and physical stability of our dataset.

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Conformational analysis and molecular dynamics of glass-forming aromatic thiacrown ethers

Physical Chemistry Chemical Physics ◽

10.1039/d0cp02585b ◽

2020 ◽

Vol 22 (32) ◽

pp. 17948-17959

Author(s):

Hubert Hellwig ◽

Andrzej Nowok ◽

Jan Grzegorz Małecki ◽

Piotr Kuś ◽

Agnieszka Jędrzejowska ◽

...

Keyword(s):

Molecular Dynamics ◽

Glass Transition ◽

Transition Temperature ◽

Dielectric Properties ◽

Glass Transition Temperature ◽

Conformational Analysis ◽

Ring Type ◽

Glass Forming ◽

Thiacrown Ethers

The dielectric properties, glass transition temperature and molecular dynamics of thiacrown ethers are strongly dependent on the thiacrown ring type.

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Glass-forming ability of Pr–(Cu,Ni)–Al alloys in eutectic system

Journal of Materials Research ◽

10.1557/jmr.2003.0088 ◽

2003 ◽

Vol 18 (3) ◽

pp. 664-671 ◽

Cited By ~ 19

Author(s):

Y. Zhang ◽

H. Tan ◽

H. Z. Kong ◽

B. Yao ◽

Y. Li

Keyword(s):

Glass Transition ◽

Transition Temperature ◽

Glass Transition Temperature ◽

Eutectic Composition ◽

Solidus Temperature ◽

Eutectic Point ◽

Glass Forming Ability ◽

Al Alloys ◽

Eutectic System ◽

Glass Forming

A eutectic point in Pr-rich Pr-(Cu,Ni)-Al alloys was experimentally determined by measuring the solidus temperature (Tm) and liquidus temperature (T1). It was found that Pr68(Cu0.5Ni0.5)25Al7 (at.%) is at the eutectic composition in the pseudoternary Pr–(Cu0.5Ni0.5)–Al alloys. The alloy Pr68(Cu0.5Ni0.5)25Al7 exhibits better glass-forming ability (GFA) than the ternary eutectic alloy Pr68Cu25Al7. However, the best GFA was obtained at an off-eutectic composition (Pr54[Cu0.5Ni0.5]30Al16) in the Pr–(Cu0.5Ni0.5)–Al alloys, which can be formed in fully amorphous rods with diameter of 1.5 mm by copper mold casting. Moreover, the glass-transition temperature Tg increases quickly (from 367 to 522 K) with the increasing of the Al content (from 3 to 27 at.%). The deviation of the best GFA composition from the eutectic point [Pr68(Cu0.5Ni0.5)25Al7] was explained in terms of the asymmetric coupled eutectic zone, the competition between growth of crystalline phase and formation of amorphous, and the higher glass-transition temperature Tg on the hypereutectic side.

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Tilted Microlens Fabrication Using Nano-Magnetic Particles

Advanced Materials Research ◽

10.4028/www.scientific.net/amr.1105.259 ◽

2015 ◽

Vol 1105 ◽

pp. 259-263

Author(s):

Shih Yu Hung ◽

Yu Ting Hung ◽

Ming Ho Shen

Keyword(s):

Magnetic Field ◽

Glass Transition ◽

Transition Temperature ◽

Glass Transition Temperature ◽

Magnetic Particles ◽

Lower Layer ◽

Glassy State ◽

Reflow Process ◽

Photoresist Layer ◽

Thermal Reflow

Double-layer heterogeneous photoresist method will be used firstly to obtain the round photoresist column with two layers of different photoresists. Since both photoresists are the positive-type, the exposure is only required once. During the thermal reflow processing, the upper photoresist layer (AZ-4620 and nanomagnetic powder mixture) reaches the glass transition temperature, which is transformed from a glassy state into a rubbery state. Since the glass transition temperature of the lower photoresist layer (AZ-5214E) is higher than the temperature of thermal reflow, the lower photoresist layer is still able to maintain its solid state. The lower layer creates a round base during the thermal reflow process, and then subjected to an appropriate magnetic field. The base can not only restrict the bottom shape of the liquid photoresist to a round shape but also prevent the sliding of liquid photoresist during the thermal reflow process, so the tilted microlens array can be obtained. We can vary the strength of magnetic field to control the oblique angle of the tilted microlens.

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