Glass Transition Event Research Articles

Structural and thermodynamical investigation in triblock copolymers of polylactide and poly(ethylene glycol), PLA-b-PEG-b-PLA, envisaged for medical applications

A series of triblock copolymers based on poly(ethylene glycol) (PEG) and poly(lactic acid) (PLA), PLA-b-PEG-b-PLA, aimed for use in biomedicine, were synthesized and studied employing a combination of structure, thermal and dynamical techniques. The copolymers differ in the PLA/PEG molar ratios in the range from 640/1 down to 20/1 and, consequently, in the length of the built PLA side blocks. The copolymers exhibit high homogeneity, evidenced by their single glass transition, crystallization and melting events, which change systematically with the reduction of the PLA/PEG ratio. In the amorphous state, the glass transition temperatures decrease in the copolymers, from ∼50 to about 40 °C, whereas the chains’ cooperativity also drops. The recordings suggest the plasticizing role of PEG on PLA and the elevation of free volume within the copolymers. The crystal nucleation is hindered, whereas, in general, the degree of crystallinity is enhanced in the copolymers. The copolymers demonstrate a potential to tune the semicrystalline morphology to a wide extent. These properties are actually desirable, as they are strongly connected with the envisaged applications (drug carrier), the performance in general (mechanical, permeation, heat transport) as well as the facilitation of the renewability/compostability, aspects that are somewhat limited for bulk PLA.

Learning from hair moisture sorption and hysteresis.

The process of moisture sorption and desorption by human hair was analysed for extracting hints on the hair structure. The isotherms of moisture sorption and desorption by hair were recorded for untreated and chemically treated (permed and bleached) hair. Data of swelling were also considered. By examining the swelling and moisture sorption of keratin fibres, it is possible to conclude that hysteresis is quite improbably caused by capillary condensation. The mobility of the protein chains and the strength of the bonds binding water molecules to the active sites inside the matrix are proposed as causes instead. The concept of "breaking symmetry", derived from moisture sorption- desorption data, and the method of evaluating this parameter, is proposed as a way of characterizing the chemical treatment of hair. The results show that bleaching produces a larger breaking of symmetry than perming, and this is suggested to be due to new hydrogen bonds, created as a result of the chemical treatment, replacing the original disulphide bonds, which are of different strength compared to the bonds of untreated hair. The quantitative sorption data matched well to the model of grains of matrix enveloped in layers of water molecules at increasing relative humidity, up to 100%. The analysis suggested that, aside from the glass transition event occurring at around 60%-70% relative humidity, there is another, less examined, transition occurring at around 30% relative humidity, assigned to the opening of the hair inner structure, and accommodation of more water molecules. Both transitions are reflected by corresponding changes in the fibre mechanical behaviour. The moisture sorption-desorption by hair was shown to not only allow a quantitative differentiation among various cosmetic treatments of the hair but to also provide valuable information on the structure of the fibre.

Characterization of Drugs with Good Glass Formers in Loaded-Mesoporous Silica and Its Theoretical Value Relevance with Mesopores Surface and Pore-Filling Capacity

The incorporation of a drug into mesoporous silica (MPS) is a promising strategy to stabilize its amorphous form. However, the drug within MPS has shown incomplete release, despite a supersaturated solution being generated. This indicates the determination of maximum drug loading in MPS below what is experimentally necessary to maximize the drug doses in the system. Therefore, this study aimed to characterize the drugs with good glass former loaded-mesoporous silica, determine the maximum drug loading, and compare its theoretical value relevance to monolayer covering the mesoporous (MCM) surface, as well as pore-filling capacity (PFC). Solvent evaporation and melt methods were used to load each drug into MPS. In addition, the glass transition of ritonavir (RTV) and cyclosporine A (CYP), as well as the melting peak of indomethacin (IDM) and saccharin (SAC) in mesoporous silica, were not discovered in the modulated differential scanning calorimetry (MDSC) curve, demonstrating that each drug was successfully incorporated into the mesopores. The amorphization of RTV-loaded MPS (RTV/MPS), CYP-loaded MPS (CYP/MPS), and IDM-loaded MPS (IDM/MPS) were confirmed as a halo pattern in powder X-ray diffraction measurements and a single glass transition event in the MDSC curve. Additionally, the good glass formers, nanoconfinement effect of MPS and silica surface interaction contributed to the amorphization of RTV, CYP and IDM within MPS. Meanwhile, the crystallization of SAC was observed in SAC-loaded MPS (SAC/MPS) due to its weak silica surface interaction and high recrystallization tendency. The maximum loading amount of RTV/MPS was experimentally close to the theoretical amount of MCM, showing monomolecular adsorption of RTV on the silica surface. On the other hand, the maximum loading amount of CYP/MPS and IDM/MPS was experimentally lower than the theoretical amount of MCM due to the lack of surface interaction. However, neither CYP or IDM occupied the entire silica surface, even though some drugs were adsorbed on the MPS surface. Moreover, the maximum loading amount of SAC/MPS was experimentally close to the theoretical amount of PFC, suggesting the multilayers of SAC within the MPS. Therefore, this study demonstrates that the characterization of drugs within MPS, such as molecular size and interaction of drug-silica surface, affects the loading efficiency of drugs within MPS that influence its relevance with the theoretical value of drugs.

Effect of drug-coformer interactions on drug dissolution from a coamorphous in mesoporous silica

In this study, the molecular state of ritonavir (RTN)-saccharin (SAC) coamorphous incorporated into mesoporous silica by solvent evaporation and the effect of SAC on the RTN dissolution from mesopores were investigated. The amorphization of RTN-SAC was confirmed as a halo pattern in powder X-ray diffraction measurements and a single glass transition event in the modulated differential scanning calorimetry (MDSC) curve. 13C solid-state NMR spectroscopy revealed a hydrogen bond between the thiazole nitrogen of RTN and the amine proton of SAC. The glass transition of the RTN-SAC coamorphous in mesoporous silica was not found in the MDSC curve, indicating that RTN and SAC were monomolecularly incorporated into the mesopores. Solid-state NMR measurements suggested that the co-incorporation of SAC into the mesopores decreased the local mobility of the thiazole group of RTN via hydrogen bond formation. The RTN-SAC 1:1 coamorphous in mesoporous silica retained the X-ray halo-patterns after 30 d of storage, even under high temperature and humidity conditions. In the dissolution test, the RTN-SAC 1:1 coamorphous in mesoporous silica maintained RTN supersaturation for a longer time than the RTN amorphous in mesoporous silica. This study demonstrated that the drug-coformer interaction within mesoporous silica can significantly improve drug dissolution.

Effect of Surface Chemistry on the Glass-Transition Dynamics of Poly(phenyl methyl siloxane) Confined in Alumina Nanopores.

Broadband dielectric spectroscopy (BDS) and differential scanning calorimetry (DSC) are combined to study the effect of changes in the surface chemistry on the segmental dynamics of glass-forming polymer, poly(methylphenylsiloxane) (PMPS), confined in anodized aluminum oxide (AAO) nanopores. Measurements were carried for native and silanized nanopores of the same pore sizes. Nanopore surfaces are modified with the use of two silanizing agents, chlorotrimethylsilane (ClTMS) and (3-aminopropyl)trimethoxysilane (APTMOS), of much different properties. The results of the dielectric studies have demonstrated that for the studied polymer located in 55 nm pores, changes in the surface chemistry and thermal treatment allows the confinement effect seen in temperature evolution of the segmental relaxation time, τα(T) to be removed. The bulk-like evolution of the segmental relaxation time can also be restored upon long-time annealing. Interestingly, the time scale of such equilibration process was found to be independent of the surface conditions. The calorimetric measurements reveal the presence of two glass-transition events in DSC thermograms of all considered systems, implying that the changes in the interfacial interactions introduced by silanization are not strong enough to inhibit the formation of the interfacial layer. Although DSC traces confirmed the two-glass-transition scenario, there is no clear evidence that vitrification of the interfacial layer affects τα(T) for nanopore-confined polymer.

Standardization of vitrification treatments for safe cryo-conservation of banana (Musa acuminata Colla) cultivars using differential scanning calorimetry

Cryo-conservation is the most promising approach and reliable method for long term conservation of banana and plantain genetic resources. Prior to the development of a safe cryo-conservation procedure for highly hydrated tissues of any vegetatively propagated crop species such as banana, suitable vitrification treatments involving loading solution in combination with Plant Vitrification Solution 2 (PVS2) solution have to be standardized. In the present study, Differential Scanning Calorimetry (DSC) technique was attempted to identify the best vitrification treatment using shoot apices as storage explants in two banana cultivars namely Grand Naine and Red banana. The results showed that DSC thermogram curves detected the formation of ice nucleation at a temperature of -18.67°C for Grand Naine and -19.16°C for Red banana in the control shoot apices. Among the sixteen vitrification treatment combinations tested, the treatments, LP6, LP7, LP10, LP11, LP14 and LP15 were judged as best treatments for cryo-conservation of both banana cultivars as revealed by the formation of glass transition events in the vitrified shoot apices. This information obtained through DSC experiments would further provide scope for designing safe cryo-conservation system for banana. This is the first report to demonstrate the application of DSC to optimize the vitrification treatments that would be adopted for developing cryo-conservation protocol for Musa germplasm.

Non-Isothermal Crystallization Kinetics of a Rapidly Solidified as-Cast TiZrHfNiCu High Entropy Bulk Metallic Glass

This paper aims to investigate the thermal behavior and crystallization kinetics of TiZrHfNiCu high entropy bulk metallic glass (HE-BMG) alloy using the standard procedure of Differential Scanning Calorimetric (DSC) annealing technique. The alloy was produced using an arc melting machine with a critical diameter of 1.5 mm. The crystallization kinetics and phase transformation mechanism of TiZrHfNiCu HE-BMG was investigated under the isochronal condition at a single heating run based on the Johnson-Mehl- Avrami (JMA) theory. In isochronal heating, the apparent activation energy for glass transition and crystallization events was analyzed by Kissinger and Ozawa methods. The average activation energy value for crystallization of TiZrHfNiCu amorphous alloys in isochronal modes was 226.41 kJ/mol for the first crystallization and 297.72 kJ/mol for second crystallization stages. The crystallization mechanism of the first step was dominated by two- and three-dimensional growth with increasing nucleation rate, while the crystallization mechanism in the second stage was dominated by two-dimensional crystallization growth with a constant nucleation rate. The diffusion mechanism result proved the theory of sluggish atomic diffusion of HEA at elevated temperature.

Physical events occurring during the cryopreservation of immortalized human T cells.

Cryopreservation is key for delivery of cellular therapies, however the key physical and biological events during cryopreservation are poorly understood. This study explored the entire cooling range, from membrane phase transitions above 0°C to the extracellular glass transition at -123°C, including an endothermic event occurring at -47°C that we attributed to the glass transition of the intracellular compartment. An immortalised, human suspension cell line (Jurkat) was studied, using the cryoprotectant dimethyl sulfoxide. Fourier transform infrared spectroscopy was used to determine membrane phase transitions and differential scanning calorimetry to analyse glass transition events. Jurkat cells were exposed to controlled cooling followed by rapid, uncontrolled cooling to examine biological implications of the events, with post-thaw viable cell number and functionality assessed up to 72 h post-thaw. The intracellular glass transition observed at -47°C corresponded to a sharp discontinuity in biological recovery following rapid cooling. No other physical events were seen which could be related to post-thaw viability or performance significantly. Controlled cooling to at least -47°C during the cryopreservation of Jurkat cells, in the presence of dimethyl sulfoxide, will ensure an optimal post-thaw viability. Below -47°C, rapid cooling can be used. This provides an enhanced physical and biological understanding of the key events during cryopreservation and should accelerate the development of optimised cryobiological cooling protocols.

Impact of binder as a formulation variable on the material and tableting properties of developed co-processed excipients

The functionality of a co-processed excipient is usually derived from its composition and the proportion of each excipient that is incorporated to yield a composite excipient. The aim of this study was to assess the impact of binder as a formulation variable on the material and tableting properties of developed co-processed excipients containing gelatin (SGS) and microcrystalline cellulose (SMS) as binders respectively in the same proportion. Two co-processed excipients, SGS and SMS were generated by combining tapioca starch (90%), gelatin or microcrystalline cellulose (7.5%) and colloidal silicon dioxide (2.5%) using the co-fusion method. Particle size analysis and morphological assessment were carried out by light microscopy and scanning electron microscopy (SEM) respectively. DSC analysis was performed to evaluate the thermal behaviour of both materials and flow properties were assessed by measuring parameters like angle of repose, bulk and tapped densities, Carr’s index and Hausner’s ratio. Compaction behaviour of both materials was determined using Heckel and Walker equations and the compressibility–tabletability–compactibility (CTC) profile for each material was obtained. Particulate and bulk-level properties of SGS and SMS revealed spherical-shaped, free-flowing powders characterized by a glass transition event typical of amorphous polymers. Compaction analysis demonstrated greater degree of plastic deformation with SMS resulting in better tableting properties with respect to tensile strength and disintegration time.The outcome of the study shows that the choice of binder used in the formulation of a co-processed excipient plays a crucial role in defining the material and tableting properties of the co-processed excipient.

Effect of Surface Modification on the Glass Transition Dynamics of Highly Polar Molecular Liquid S-Methoxy-PC Confined in Anodic Aluminum Oxide Nanopores

In the presence of nanoscale confinement, the role of surface effects come to the fore in determining the glass-transition dynamics of the molecular liquids and polymers. Therefore, by playing with the surface chemistry it is possible to understand better the mechanism which governs the behavior of glass-forming systems at the nanoscale. In this work, we have combined dielectric and calorimetric data to study surface and confinement effects for highly polar glass-forming liquid S-Methoxy-PC constrained within anodic aluminum oxide membranes of different pore sizes. The inner surface of the pores was modified either by silanization or atomic layer deposition (ALD) coatings. For the tested substance in native nanopores, we have observed two glass transition events in the calorimetric response accompanied by a characteristic deviation of the temperature dependence of the α-relaxation time from the Vogel–Fulcher–Tamman law. We found that depending on the hydrophobicity of the ALD layer the glass transition temperature of the interfacial layer tends to decrease, the α-relaxation peak broadens, and the molecular mobility slows down compared to the native pores. These changes are more visible with increasing hydrophobicity of the surface. Silanization was also found to eliminate at least partially the effects caused by nanopore confinement. However, in this study the most pronounced effects were observed only for pores with large diameters.

Influence of Preparation Methods on Physicochemical and Pharmacokinetic Properties of Co-amorphous Formulations: The Case of Co-amorphous Atorvastatin: Naringin

The goal of the study was to investigate the influence of processing methods on the physicochemical and pharmacokinetic properties of co-amorphous materials. Co-amorphous formulations of atorvastatin (ATV) and naringin (NRG) in the molar ratio 1:1 were prepared by quench cooling (ANQC), solvent evaporation (ANSE), and ball milling (ANBM) and characterized by differential scanning calorimetry (DSC), powder X-ray diffractometry (XRPD), and Fourier transform infrared spectroscopy (FTIR). Further, the performance of prepared co-amorphous formulations was evaluated in vitro and in vivo. All processing methods yielded homogeneous co-amorphous formulation, which was confirmed by single glass transition (Tg) event and diffuse halo in DSC and XRPD, respectively. Irrespective of processing method employed, all co-amorphous formulations were found stable at 30 °C for 90 days in dry conditions (under vacuum). Significant improvement in the solubility of ATV was observed in ANQC and ANSE co-amorphous formulations, highest being 56-fold for the later. ATV from ANSE formulation showed highest drug release (97%), while surprisingly ANQC showed significantly lower ATV release as compared to the physical mixture. Amongst three preparation methods, solubility advantage of ANSE could translate into efficacious pharmacokinetic parameters, where the improvement in ATV exposure (AUC 0-t) and plasma concentration (Cmax) were found 4.5-fold and 7-fold, respectively, as compared to the physical mixture. It was concluded that the preparation methods of co-amorphous formulations have a profound effect on physical properties like stability, physicochemical properties like solubility, dissolution rate, and pharmacokinetic properties like AUC and Cmax.

Miscibility studies of plastic-mimetic polypeptide with hydroxypropylmethylcellulose blends and generation of non-woven fabrics

In the current investigation, the results of viscometric measurements, thermal property, SEM, XRD and FTIR of the polymer blends containing synthetic plastic-based polypeptide (PLP) with hydroxypropylmethylcellulose (HPMC) on miscibility is discussed. Various interaction parameters; KH, Δ[η]m, ΔB, μ, α, β and ΔK indicated the miscibility of polypeptide/HPMC up to 40% of the PLP in the blend at room temperature. The calorimetric results a single glass transition event for miscible systems. Further, the results were aligned with the scanning electron microscope and XRD analysis. Details concerning the nature of interactions in these systems and how they are influenced by the peptide proportion in the blends are discussed. The thermo gravimetric analysis manifested the improved thermal stability of the blends than their individual polymers. Additionally, the blend solutions were fabricated into non-woven fabrics with electrospinning technique, which may be a good candidate for pharmaceutical and biomedical applications.

Thermal & Dielectric Spectroscopic Investigation on Orientationaly Disordered Crystal- Cyclobutanol

Abstract Orientationallydisordered crystals (plastic crystals) maintain translational order along their crystallographic axis while continue to have orientational degrees of freedom. Since freezing of orientational motion of molecule leads to glass transition, these rotationally disordered systems form glassy crystals below their glass transition temperature. Because of the presence of translational order, these kind of materials can easily treated in both mathematical and simulation approaches and are considered as the ideal or model system for studying glass transition phenomena. Here by using differential scanning calorimetry (DSC) and broadband dielectric spectroscopy (BDS), thermal and dielectric behaviour of the orientation ally disordered phases of an organic plastic crystal cyclobutanol have been studied. During quench cooling of the sample below the melting point, three solid-solid phase transitions, one at 180K called phase I, other at 170K called phase II, and another one at 158 K and glass transition (133K) events were observed using the DSC. The dielectric spectra of the cyclobutanol were recorded in a wide frequency range of 10-2 Hz to 107Hz for different temperatures. The dielectric spectra revealed the presence of the three phases, of which phase I was observed below the melting point up to nearly 180 K, the phase II was observed up to nearly 170 K and phase III was observed further up to 158K. In these phases signatures of two structural α relaxations were observed. The secondary relaxation below the glass transition event was also seen, whose strength was found to be very small compared to those observed in other plastic crystals. The α relaxation showed non-Arrhenius temperature dependence depicted by Vogel-Fulcher-Tammann equation,while secondary relaxation mimicked Arrhenius temperature dependence.

Testing the paradigm of an ideal glass transition: Dynamics of an ultrastable polymeric glass.

A major challenge to understanding glass-forming materials is obtaining equilibrium data far below the laboratory glass transition temperature T g. The challenge arises because it takes geologic aging times to achieve the equilibrium glassy state when temperatures are well below T g. Here, we finesse this problem through measurements on an ultrastable amorphous Teflon with fictive temperature T f near to its Kauzmann temperature T K. In the window between T f and T g, the material has a lower molecular mobility than the equilibrium state because of its low specific volume and enthalpy. Our measurements show that the determined scaled relaxation times deviate strongly from the classical expectation of divergence of time scales at a finite temperature. The results challenge the view of an ideal glass transition at or near to T K.

Correlation between Properties and Conductivity Mechanism in Poly(vinyl alcohol)-based Lithium Solid Electrolytes

In this study, a new family of poly(vinyl alcohol)-based solid membrane electrolytes is proposed. The single ion conducting polyelectrolytes are obtained by direct lithiation of partially hydrolyzed poly(vinyl alcohol), forming a lithium-poly(vinyl alkoxide) macromolecular salt. Furthermore, in order to improve the ionic conductivity, the obtained polymer is plasticized with 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide (EMImTFSI) ionic liquid. Thermogravimetric analysis demonstrates a thermal stability higher than 215 °C. Differential Scanning Calorimetry studies show a polymer associated glass transition event and a melting transition related to the ionic liquid domains at ca. +80 and −40 °C respectively. Fourier-transform infrared spectroscopy proves that: a) lithiation of the membrane results in an increase to the amorphic character of the polymer backbone; and b) after ionic liquid addition to the lithiated membrane, the effective coordination of lithium cations by the TFSI-anions of the ionic liquid augments the ionic conductivity of the proposed materials. Broadband electrical spectroscopy (BES) investigations reveal that this system is characterized by several polarization phenomena and dielectric relaxation events. Analysis of the BES results, using suitable models, allows for the conductivity mechanism in the proposed polymer electrolytes to be hypothesized. Finally, the ionic conductivity values of 1.29 · 10−5 S cm−1 and 1.92 · 10−3 S cm−1 at 30 and 80 °C render these materials very promising for application in electrochemical devices.

Insights on the Physical State Reached by an Active Pharmaceutical Ingredient upon High-Energy Milling.

We study the physicochemical transformations of crystalline quinidine upon high-energy milling. The investigations have been achieved by classical, high performance, and fast scanning calorimetry combined with broadband dielectric spectroscopy and X-ray powder diffraction. As evolution of crystalline quinidine with time of milling revealed a prominent sub-Tg cold-crystallization phenomenon, independent and complementary analytical techniques were implemented. Fast scanning calorimetry was performed for the first time on a milled pharmaceutical compound to postpone the crystallization event to higher temperatures. These fast thermal analyses allowed one to spotlight a genuine glass transition event. In addition, an aging experiment on the milled powder revealed a clear structural relaxation testifying to the presence of a glassy fraction in the milled sample. Last, dielectric analysis of milled quinidine disclosed the presence of localized and delocalized molecular mobility characteristics of glasses. Results for samples obtained by two distinct amorphization routes, vitrification and high-energy milling, indicate that amorphous fraction in milled quinidine behaves the same way as melt-quenched quinidine. These above-mentioned techniques proved their relevancy and efficiency to characterize milled quinidine, and fast scanning calorimetry in particular appears a promising screening tool for disordered systems.

Characterization of Polyurethane Coated Aerospace Aluminium Alloy (7075) By DSC, XRD and Adhesion Test

The research is envisaging characterizing the Polyurethane (PU) coating on AA 7075 so as to predict the aircraft coating life. Differential Scanning Calorimetry (DSC) and X-ray Diffractometry have been employed to investigate the differences in thermal behavior and crystalline structure of the polyurethane (GB BOND 141). DSC can be used to examine the material from a subambient starting temperature to the glass transition event and finally through the crystalline melting region. X-ray diffraction (XRD) provides important structural information about the polyurethane in the structure of semi-crystalline polymer substance consisting of two phases, viz., amorphous and crystalline as well as their fine texture which has a strong effect on physical and mechanical properties of polyurethane. After analyzing the characteristics, the extent of coating loss is examining visually in order to evaluate the adhesion property before carrying out the peel-off test.

Dielectric Spectroscopy in Ibuprofen-Dioxane Mixture

In recent years, the dielectric study of amorphous pharmaceuticals has made a considerable effort towards correlating the molecular mobility with their physical and chemical stability. The molecular mobility of amorphous materials is affected by temperature, additives (such as water) and specific interactions (such as Hydrogen bond). Therefore, to understand the physicochemical instability of amorphous materials, nature of their molecular mobility needs to comprehend. In this order, the Dielectric and Calorimetric measurements were performed on a mixture of ibuprofen and 1,4-dioxane. The dielectric spectroscopy reveals two relaxation processes, (designated as αD, and α) in the supercooled region. The spectral shape of αD and α process can be explained satisfactorily throughout the frequency range using Havriliak-Negami (HN) shape function. The αD process is found to be Debye-like (i.e., αHN=0 and βHN=1) in nature and α process kinetically freezes at Tg-onset (DSC) implies that α- process indeed corresponds to the glass transition event. Both processes are found to be non-Arrhenius in nature. In addition, two secondary relaxation processes (designated as βJG and β) are observed and are comparable with the literature. The activation energy of β process indicates that it‟s originating from the fluctuations of the side group larger than -OH group. Also, the calculated fragility index demonstrates that ibuprofen is a fragile glass former.

Formation and phase evolution of liquid phase-separated metallic glasses with double glass transition, crystallization and melting

Zr57Co27Al16 and La57Co27Al16 alloys with excellent glass-forming ability (GFA) were adopted to synthesize new phase-separated bulk metallic glasses (BMGs) upon rapid solidification. (ZrxLa1−x)57Co27Al16 (x=0.2, 0.4, 0.6, and 0.8) melts separate into ZrCo-rich and La-rich liquids upon cooling due to the existence of a miscibility gap in Zr-La liquids. The intrinsic and extrinsic mechanisms for the formation of phase-separated alloys under different casting conditions were analyzed in detail. The GFA of the studied alloys changes in the following order: Zr57Co27Al16>La57Co27Al16>Zr11.4La45.6Co27Al16>Zr22.8La34.2Co27Al16>Zr34.2La22.8Co27Al16>Zr45.6La11.4Co27Al16. The quaternary Zr-La-Co-Al phase-separated metallic glasses (MGs) are shown to experience double glass transition, crystallization and melting events, which could be regarded as possible model materials to study the glassy transition and structural relaxation behavior of BMGs.

Amorphous–amorphous phase separation in hydrophobically-modified starch–sucrose blends I. Phase behavior and thermodynamic characterization

The glass transition of amorphous powders consisting of blends of octenyl-succinic anhydride (OSA) modified starch, and sucrose was studied as a function of blend composition and water content. Polarized light microscopy, differential scanning calorimetry (DSC) and water vapor sorption analysis were performed on four blends varying in their modified starch to sucrose ratio. The thermograms of the blends exhibit either a single glass transition event, characterized by a quite broad temperature range, or two glass transitions. This hints at a limited degree of phase separation into two amorphous phases within the blend matrix, most likely at the microscale. The results from dynamic water vapor sorption studies indicate that, in the phase-separated blends, the sucrose-rich phase constitutes the dispersed phase, while the continuous phase is formed by the phase rich in OSA starch. Our findings open up new ways to engineer glass encapsulation systems with composite structure, which can provide for a high level of protection of encapsulated bioactive compounds as well as defined release properties.