Calorimetric Scans Research Articles

DSC Derived (Ea & ΔG) Energetics and Aggregation Predictions for mAbs

The Arrhenius energy of activation of unfolding Ea unfolding and Gibbs free energy of unfolding ΔG unfolding have been calculated utilizing DSC differential scanning calorimetry for 4 mAbs (1 biosimilar) in 3 formulations. DSC derived ΔTm melting temperature changes for each mAb domain (CH2, Fab, CH3) at calorimetric scan rates at 60 °C, 90 °C, 150 °C and 200 °C / hr. were utilized to calculate the kinetic Eaunfolding. The DSC derived Ea trend with observed aggregate formation and can be used to predict%HMW formation post 9-month storage at 5 °C and 40 °C for all formulations analyzed. Additionally, thermodynamic ΔG unfolding energies were also derived (Tm, ΔCp and ΔH measurements) for each mAb at every scan rate to observe scan rate dependence of ΔG and for extrapolation to 0 °C/hr. (to report ΔG at true equilibrium conditions). Both derived thermodynamic ΔG and kinetic Ea energies were combined to build full energetic landscapes for mAb unfolding and aggregation. Statistical multivariate analysis of kinetic (Ea CH2, Ea Fab, Ea CH3) energies, thermodynamic (ΔG5 °C and ΔG40 °C) energies and in-silico modeled surface properties was also performed. Analysis revealed key significant parameters contributing to aggregation. These parameters were utilized to build predictive aggregation models for 25 mg/mL mAb formulations stored 9-months at 5 °C and 40 °C.

A new experimental setup for combined fast differential scanning calorimetry and X-ray photon correlation spectroscopy.

Synchrotron-radiation-based techniques are a powerful tool for the investigation of materials. In particular, the availability of highly brilliant sources has opened the possibility to develop techniques sensitive to dynamics at the atomic scale such as X-ray photon correlation spectroscopy (XPCS). XPCS is particularly relevant in the study of glasses, which have been often investigated at the macroscopic scale by, for example, differential scanning calorimetry. Here, we show how to adapt a Flash calorimeter to combine XPCS and calorimetric scans. This setup paves the way to novel experiments requiring dynamical and thermodynamic information, ranging from the study of the crystallization kinetics to the study of the glass transition in systems that can be vitrified thanks to the high cooling rates reachable with an ultrafast calorimeter.

The effect of silicon carbide addition on the transformation temperatures and wear resistance of Cu-based shape memory alloys

In this work, the effect of SiC addition was studied on the transformation temperature and wear resistance of Cu-Al-Ni shape memory alloys. SiC was added with three different ratios of 0.5, 1, and 3% to the base alloy, where a ratio above and below 1% was chosen to study the effects and 1% as an intermediate barrier followed by casting and homogenization at 900 °C. Some tests were carried out, such as Calorimetric Differential Scan (DSC), Optical Microscope test (OM), the scanning electron microscopy (SEM), energy dispersion spectrometer (EDS), and X-ray diffraction (XRD), Hardness and wear tests. The results show OM and SEM test reveals both phases of the martensite which is AlCu3 (β) and Al 7Cu23Ni (γ). Also, the addition of SiC shows a visible effect on phase formation and transformation temperature. Hardness and wear tests revealed that the addition of SiC particles to SMAs increases the hardness of the samples until it reaches 465 while showing a decrease in the wear rate with the increase in the percentage of reinforcements.

High throughput optimization procedure to characterize vitrification kinetics

We present VITRIFAST, a high throughput optimization procedure to characterize the vitrification kinetics based on calorimetric measurements. By analyzing the temperature dependence of specific heat capacity, the method determines the fictive temperature, Tf, and the enthalpy change during physical aging, ΔH, within only a few seconds. We tested VITRIFAST on the low molecular weight glass-former o−terphenyl (OTP) and on an archetypal glass forming polymer, polystyrene (PS), by analyzing the outcome of two classical sets of experiments. By means of fast scanning calorimetry (FSC), we characterized the vitrification kinetics in a wide range of cooling rates and the isothermal physical aging after vitrification at a given rate. In less than 3 minutes, our method could process 18 different calorimetric scans and provided values of Tf and ΔH in excellent agreement with those reported in the literature. VITRIFAST can be employed in the analysis of the temperature dependence of any type of second order derivative of free energy and represents a tremendous advance in the data analysis of calorimetric scans. The method is particularly helpful for fast scanning calorimetry users, considering the extremely large number of heat capacity scans recorded by this technique within a few minutes.

Curing kinetics and thermal properties of imide containing phthalonitrile resin using aromatic amines

Due to their outstanding properties, phthalonitrile based polymers plays an important role in high performance advanced materials evaluated depending upon their curing process and mechanism. Henceforth it is necessary to understand the curing kinetics of bisphthalonitrile monomer having imide linkage using 4, 4’-diaminodiphenylsulfone (DDS) as curing agent for further investigations. Thus, curing kinetics was investigated by recording non-isothermal differential scanning calorimetric (DSC) scans at heating rates of 5 °C, 10 °C, 15 °C and 20 °C/min. Activation energy for bisphthalonitrile/4, 4’-diaminodiphenylsulfone (DDS) system was calculated using Starink method and results give a substantial evidence that Arrhenius activation energy (Ea) are certainly dependent on the structure of monomer and curing agent. The cured FIPN/DDS, ODPA-PN/ DDS systems show comparable high thermal stability and elevated glass transition temperature as compared to Bis-ADPN/ DDS composition. Subsequently, this composition exhibits comparative heat resistance and improved moisture resistance.

Reentrant glass transition leading to ultrastable metallic glass

Abstract Polyamorphs are often observed in amorphous matters, and a representative example is the reentrant glass transition in colloid systems. For metallic amorphous alloys, however, the cases reported so far are limited to metallic glasses (MGs) that undergo electronic transitions under gigapascal applied pressure, or the presence of two liquids at the same composition. Here we report the first observation of a reentrant glass transition in MGs. This unusual reentrant glass transition transforms an MG from its as-quenched state (Glass I) to an ultrastable state (Glass II), mediated by the supercooled liquid of Glass I. Specifically, upon heating to above its glass transition temperature under ambient pressure, Glass I first transitions into its supercooled liquid, which then transforms into a new Glass II, accompanied by an exothermic peak in calorimetric scan, together with a precipitous drop in volume, electrical resistance and specific heat, as well as clear evidence of local structural ordering on the short-to-medium-range scale revealed via in-situ synchrotron X-ray scattering. Atomistic simulations indicate enhanced ordering of locally favored motifs to establish correlations in the medium range that resemble those in equilibrium crystalline compounds. The resulting lower-energy Glass II has its own glass transition temperature higher than that of Glass I by as much as 50 degrees. This route thus delivers a thermodynamically and kinetically ultrastable MG that can be easily retained to ambient conditions.

Physico-Chemical Characterization of Two Epoxy Systems Using Porphyrins as Curing Agents

Chlorophyllin and meso-tetra(4-carboxifenyl)porphyrin have been used as crosslinking agents for curing the epoxy resin of bisphenol A diglycidyl ether. Monitoring reaction by DSC revealed two peaks on calorimetric scans show. FTIR corroborates that the first signal corresponds to an esterification reaction while the second one is due to an etherification one. Thermodegradation temperatures show that the signals obtained by calorimetry do not correspond to decomposition processes.

Dehydration/Rehydration Cycles for Mixing Phospholipids without the Use of Organic Solvents.

An environmentally friendly and straightforward dehydration/rehydration method for glycerophospholipid mixing that avoids the use of organic solvents, cosolvents, or additives was developed. We prepared binary mixtures of zwitterionic and anionic glycerophospholipids using only deionized water in the entire mixing process. The resulting lipid films were subsequently reconstituted in vesicular form and compared to controls using differential scanning calorimetry. The calorimetric scans revealed no significant differences between mixing methods for any of the studied cases. These findings suggest that the developed dehydration/rehydration procedure creates a sample with equivalent compositional uniformity than the conventional solvent evaporation technique.

Investigation of poly[oligo(ethylene glycol)diacrylates] as potential stationary phases in GC.

Poly[oligo(ethylene glycol)diacrylate]s were investigated as potential candidates for application as stationary phases in capillary gas chromatography. Depending on the molar mass of the monomer, up to three different phase transitions were observed in calorimetric scans of the polymers. Two transitions have been identified as the glass transition and melting of crystallites while the nature of the third effect remains unknown. The new stationary phases demonstrate a good separating ability and selectivity in the viscous-elastic state, i.e. at temperatures above the glass transition and melting points. The new polymeric stationary phases possess selectivity similar to conventional PEG columns but provide better thermal stability than conventional PEG stationary phases.

Thermo-responsive alternating conetworks by the Diels-Alder reaction of furan-terminated 4-armed star-shaped ɛ-caprolactone oligomers and maleimide-terminated 4-armed star-shaped l-lactide oligomers

Hydroxy-terminated 4-armed star-shaped ɛ-caprolactone and l-lactide oligomers (H4CLOn and H4LAOn) with a degree of polymerization per arm (n = 5, 10 or 15) were reacted with furfuryl isocyanate and (4-maleimidophenyl)isocyanate to produce furan- and maleimide-functionalized 4-armed star-shaped ɛ-caprolactone and l-lactide oligomers (F4CLOn and M4LAOn), respectively. The Diels-Alder (DA) reaction of F4CLOn and M4LAOn from room temperature to 40 °C in 1,2-dichloroethane produced conetworks (F4CLOn-M4LAOn) in which the two star-shaped oligomer units are alternatingly arranged. The conversion of DA reaction for F4CLOn-M4LAOn decreased with increasing n value. F4CLO10-M4LAO10 exhibited a higher degree of swelling in chloroform than F4CLO5-M4LAO5 in agreement with the difference in crosslinking density. F4CLO15-M4LAO15 dissolved in chloroform because of the insufficient crosslinking reaction. All the F4CLOn-M4LAOns exhibited endothermic peaks due to retro-DA reactions on the first heating differential scanning calorimetric scans, whereas the corresponding peaks considerably weakened on the second heating scans due to phase separation. The cut films of F4CLOn-M4LAOn (n = 5 and 10) were self-repaired by heating the partially superposed pieces at 70 °C.

Thermal memory fading by heating to a lower temperature: Experimental data on polycrystalline NiFeGa ribbons and 2D statistical model predictions

Shape memory alloys are known to memorise one -or several- temperatures at which the martensite-austenite transformation was stopped before completion in the past, the memory manifesting as specific dips in subsequent calorimetric scans. Previous studies have shown that this memory can be erased by heating to higher temperatures than the ones previously recorded. In this paper, we study a distinct memory fading effect which takes place by heating to a lower temperature. This effect is reported in NiFeGa as polycrystalline ribbons, the alloy being initially studied as bulk for which the thermal memory effect was not found. If, after an initial incomplete heating up to T1 one performs a second incomplete heating up to T2<T1, a new calorimetric dip appears at T2, as expected, while less expected was that the dip corresponding to T1 reduces in amplitude or even vanishes (if the arrest at T2 is repeated). The memory fading effect is more clear for small differences T1−T2 and less obvious or absent for large ones. The second part of the paper employs a statistical 2D model, which associates the memorized temperatures with a depletion of certain martensite plates sizes, and also supports the memory fading effect.

A new approach for investigating neurodegenerative disorders in mice based on DSC

In this work, we develop a new approach based on differential scanning calorimetry (DSC) for diagnostics and characterization of the changes in the brain at molecular and supramolecular level associated with drug-induced neurodegenerative disorders. In order to test the DSC potential, we used an experimental animal model of scopolamine-induced dementia of Alzheimer’s disease (AD) type. The DSC measurements taken on supernatants of brain tissue homogenates isolated from healthy animals and animals with scopolamine-induced dementia showed that heat capacity curves for animals with scopolamine-induced dementia strongly differ from the respective curves for healthy animals. The effects of preventive treatments with various substances and their combinations expected to have protective effect and hinder the development of AD (myrtenal, ellagic acid, lipoic acid, ascorbic acid) are also clearly displayed in the calorimetric scans. These measurements show that DSC is an appropriate method for detection and characterization of the compositional changes taking place in affected by dementia brain tissues.

Anomalous Enthalpy Relaxation in Vitreous Silica

It is a challenge to calorimetrically determine the glass transition temperature (Tg) of vitreous silica. Here we demonstrate that this challenge mainly arises from the extreme sensitivity of the Tg to the hydroxyl content in vitreous silica, but also from the irreversibility of its glass transition when repeating the calorimetric scans. It is known that the liquid fragility (i.e., the speed of the viscous slow-down of a supercooled liquid at its Tg during cooling) has impact on enthalpy relaxation in glass. Here we find that vitreous silica (as a strong system) exhibits striking anomalies in both glass transition and enthalpy relaxation compared to fragile oxide systems. The anomalous enthalpy relaxation of vitreous silica is discovered by performing the hperquenching-annealing-calorimetry experiments. We argue that the strong systems like vitreous silica and vitreous Germania relax in a structurally cooperative manner, whereas the fragile ones do in a structurally independent fashion. We discuss the origin of the anomalous enthalpy relaxation in the HQ vitreous silica.

Preparation and Thermo-Mechanical Characterization of Novel Epoxy Resins Using Renewable Resource Materials

The present paper reports the preparation and thermo-mechanical characterization of epoxy resin from renewable resource materials viz. cardanol and furfural. The cardanol furfural based epoxy resin was prepared by reacting cardanol furfural based novolac resin with molar excess of epichlorohydrin, in basic medium, at 120 °C. The cardanol furfural based novolac resin was synthesized by reacting cardanol and furfural in the molar ratios viz. 1.0:0.5, 1.0:0.6, 1.0:0.7 and 1.0:0.8, respectively, using succinic acid as catalyst. The prepared resin samples were characterized by Fourier-transform infrared and nuclear magnetic resonance spectroscopic analysis. The prepared epoxy resin samples were cured by using diaminodiphenylmethane. The samples were cured at 160 °C, in an air oven, which was determined by peak temperatures from the dynamic differential scanning calorimetric (DSC) scans. DSC technique was used to investigate the curing behavior. Thermal stability, as assesed by dynamic thermogravimetric traces of the epoxy resin sample with molar ratio 1:0.8, was found to be the highest among all other samples. The castings of the cured samples were used for the determination of mechanical properties such as tensile strength, impact strength etc. whereas cured film samples were used to observe the effect of various chemicals and solvents on the surface of the film. The epoxy resin sample prepared from high molar ratio i.e. 1:0.8 was found to exhibit better mechanical and chemical properties than other samples.

Degradation of a Polycaprolactone/Eggshell Biocomposite in a Bioreactor

The biodegradation process of a polycaprolactone (PCL)/eggshell (ES) biocomposite (50/50 w/w) was studied for 8 weeks, using a bioreactor, which allowed to control: temperature, moisture, soil pH, light and anaerobic condition during composting. Scanning electron microscopy showed that the degradation process occurred mainly on the sample surface, attributable to the microbial attack and the weight loss showed a higher degradation for the PCL/ES samples than for pure PCL. Viscometric tests showed that the viscosity of the PCL phase in the biocomposite decreased more than when PCL was used alone, due to the higher depolymerization in the biocomposites. Differential scanning calorimetric thermal scans showed that the crystallization temperature changed for 8 weeks. In conclusion, it was noted that soil pH, heat and an aerobic environment accelerate the degradation process, while a photo-controlled, anaerobic and moisture-saturated environment delays this process, as compared with the composting system used as control.

Evolution of the properties of a poly(l‐lactic acid) scaffold with double porosity during in vitro degradation in a phosphate‐buffered saline solution

ABSTRACTA poly(l‐lactic acid) scaffold prepared by a combination of freeze‐extraction and porogen‐leaching methods was submitted to static degradation in a phosphate‐buffered saline solution at pH 7.4 and 37°C for up to 12 months. After 6 months of degradation, the scaffold maintained its integrity, although noticeable changes in its permeability and pore size were recorded. After 12 months, scanning electron microscopy pictures showed that most of the trabeculae were broken, and the sample disaggregated under minimum loading. Neither weight loss nor crystallinity changes in the first heating calorimetric scan were observed during the degradation experiment. However, after 12 months, a rise in the crystallinity from 13 to 38% and a drop in the glass‐transition temperature from 58 to 54°C were measured in the second heating scan. The onset of thermal degradation moved from 300 to 210°C after 12 months. Although the elastic modulus suffered only a very slight reduction with degradation time, the aggregate modulus decreased 44% after 6 months. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014, 131, 40956.

Simulated Isothermal Crystallization Kinetics from Non-Isothermal Experimental Data

In the present work, a new simple and robust approach, named ‘simulated isothermal’ technique, is proposed for getting isothermal transformation behavior of crystallization of glassy alloys at temperatures well above the normal crystallization temperatures (Tx) from a set of non-isothermal differential scanning calorimetric (DSC) scans performed at different heating rates. The isothermal and simulated isothermal kinetic data for the crystallization of glassy alloys compare well. The problem of finding small heat change on crystallization during isothermal DSC scans below Tx is avoided in the present approach, since it uses non-isothermal DSC scans, which is associated with large heat change on crystallization. It also enables to get complete understanding of the mechanism of crystallization of glassy alloys.

Enzymatic catalysis in a whey protein matrix at temperatures in the vicinity of the glass transition

The current study evaluates the effect of temperature on α-glucosidase activity, following incorporation of the enzyme into a whey protein matrix through spray drying. Thermomechanical characterization of the matrix was achieved using the techniques of modulated temperature differential scanning calorimetry and small-deformation dynamic mechanical analysis. As the concentration was raised from 75 to 94% (w/w), denaturation of the protein occurred at increasing temperatures. In contrast, denaturation was not observed in calorimetric scans after spray drying. The glass transition temperature (Tg) measured in the dried particles using dynamic mechanical analysis was approximately 40°C. An optimized procedure was developed whereby α-glucosidase and its substrate p-nitrophenyl α-d-glucopyranoside were incorporated into the whey matrix. The effect of temperature on enzymatic catalysis was investigated and, below 40°C, activity was low and relatively independent of temperature. However, the rates of product formation markedly accelerated as temperatures were increased beyond Tg. These novel observations strongly emphasize the pronounced effect of mechanical Tg of the protein matrix on enzymatic activity.

Studies of nanocomposites of carbon nanotubes and a negative dielectric anisotropy liquid crystal

It has been widely recognized that the combination of carbon nanotube (CNT) and liquid crystals (LCs) not only provides a useful way to align CNTs, but also dramatically enhances the order in the LC phases, which is especially useful in liquid crystal display (LCD) technology. As the measure of this phase behavior, the complex specific heat is presented over a wide temperature range for a negative dielectric anisotropy alkoxyphenylbenzoate liquid crystal (9OO4) and CNT composites as a function of CNT concentration. The calorimetric scans were performed under near-equilibrium conditions between 25 and 95 °C, first cooling and then followed by heating for CNT weight percent ranging from ϕ(w) = 0 to 0.2. All 9OO4/CNT mesophases have transition temperatures ~1 K higher and a crystallization temperature 4 K higher than that of the pure 9OO4. The crystal phase superheats until a strongly first-order specific heat feature is observed, 0.5 K higher than in the pure 9OO4. The transition enthalpy for the nanocomposite mesophases is 10% lower than that observed in the pure 9OO4. The strongly first-order crystallization and melting transition enthalpies are essentially constant over this range of ϕ(w). Complementary electroclinic measurement on a 0.05 wt. % sample, cooling towards the smectic-C phase from the smectic-A, indicates that the SmA-SmC transition remains mean-field-like in the presence of the CNTs. Given the homogeneous and random distribution of CNTs in these nanocomposites, we interpret these results as arising from the LC-CNT surface interaction pinning the orientational order uniformly along the CNT, without pinning the position of the 9OO4 molecule, leading to a net ordering effect for all phases. These effects of incorporating CNTs into LCs are likely due to "anisotropic orientational" coupling between CNT and LC, the change in the elastic properties of composites and thermal anisotropic properties of the CNTs.

Hydration dependence of myoglobin dynamics studied with elastic neutron scattering, differential scanning calorimetry and broadband dielectric spectroscopy

In this work we present a thorough investigation of the hydration dependence of myoglobin dynamics. The study is performed on D2O-hydrated protein powders in the hydration range 0<h<0.5 (h≡gr[D2O]/gr[protein]) and in the temperature range 20–300K. The protein equilibrium fluctuations are investigated with Elastic Neutron Scattering using the spectrometer IN13 at ILL (Grenoble), while the relaxations of the protein+hydration water system are investigated with Broadband Dielectric Spectroscopy; finally, Differential Scanning Calorimetry is used to obtain a thermodynamic description of the system. The effect of increasing hydration is to speed up the relaxations of the myoglobin+hydration water system and, thermodynamically, to decrease the glass transition temperature; these effects tend to saturate at h values greater than ~0.3. Moreover, the calorimetric scans put in evidence the occurrence of an endothermic peak whose onset temperature is located at ~230K independent of hydration. From the point of view of the protein equilibrium fluctuations, while the amplitude of anharmonic mean square displacements is found to increase with hydration, their onset temperature (i.e. the onset temperature of the well known “protein dynamical transition”) is hydration independent. On the basis of the above results, the relevance of protein+hydration water relaxations and of the thermodynamic state of hydration water to the onset of the protein dynamical transition is discussed.