Highlighting the interdependence between volumetric contribution of fragility and cooperativity for polymeric segmental relaxation.

The blurring around the link between the isobaric fragility and the characteristic size of cooperative rearranging region for glass-forming liquids has been cleared up by considering volumetric and thermal contributions of the structural relaxation. The measurement of these contributions is carried out for three amorphous thermoplastic polymers using broadband dielectric spectroscopy under pressure, providing an understanding of the link between isobaric fragilities, glass transition temperatures, and microstructures. The cooperative rearranging region (CRR) volume is calculated as a function of pressure using the extended Donth's approach, and the values are compared with the activation volume at the glass transition under different isobaric conditions. By combining these different results, a link between the chemical structure and the influence of pressure/temperature on the molecular mobility can be established. Furthermore, this study shows also a strong correlation between the activation volume, leading to the volumetric contribution of the isobaric fragility, and the CRR volume. Finally, this work highlights the influence of inter- and intra-molecular interactions on thermal and volumetric contributions of the isobaric fragility as a function of pressure.

D-Sorbitol Physical Properties Effects on Filaments Used by 3D Printing Process for Personalized Medicine.

Fused filament fabrication (FFF) is a process used to manufacture oral forms adapted to the needs of patients. Polyethylene oxide (PEO) filaments were produced by hot melt extrusion (HME) to obtain a filament suitable for the production of amiodarone hydrochloride oral forms by FFF 3D printing. In order to produce personalized oral forms adapted to the patient characteristics, filaments used by FFF must be controlled in terms of mass homogeneity along filament. This work highlights the relation between filament mass homogeneity and its diameter. This is why the impact of filler excipients physical properties was studied. It has been showed that the particle's size distribution of the filler can modify the filament diameter variability which has had an impact on the mass of oral forms produced by FFF. Through this work it was shown that D-Sorbitol from Carlo Erba allows to obtain a diameter variability of less than 2% due to its unique particle's size distribution. Using the filament produced by HME and an innovating calibration method based on the filament length, it has been possible to carry out three dosages of 125 mg, 750 mg and 1000 mg by 3D printing with acceptable mass uniformity.

Investigation of Drug-Excipient Interactions in Biclotymol Amorphous Solid Dispersions.

The effect of low molecular weight excipients on drug-excipient interactions, molecular mobility, and propensity to recrystallization of an amorphous active pharmaceutical ingredient is investigated. Two structurally related excipients (α-pentaacetylglucose and ß-pentaacetylglucose), five different drug:excipient ratios (1:5, 1:2, 1:1, 2:1, and 5:1, w/w), and three different solid state characterization tools (differential scanning calorimetry, X-ray powder diffraction, and dielectric relaxation spectroscopy) were selected for the present research. Our investigation has shown that the excipient concentration and its molecular structure reveal quasi-identical molecular dynamic behavior of solid dispersions above and below the glass transition temperature. Across to complementary quantum mechanical simulations, we point out a clear indication of a strong interaction between biclotymol and the acetylated saccharides. Moreover, the thermodynamic study on these amorphous solid dispersions highlighted a stabilizing effect of α-pentaacetylglucose regardless of its quantity while an excessive concentration of ß-pentaacetylglucose revealed a poor crystallization inhibition. Finally, through long-term stability studies, we also showed the limiting excipient concentration needed to stabilize our amorphous API. Herewith, the developed procedure in this paper appears to be a promising tool for solid-state characterization of complex pharmaceutical formulations.

From monomers to self-assembled monolayers: the evolution of molecular mobility with structural confinements.

The effect of structural constriction on molecular mobility is investigated by broadband dielectric spectroscopy (BDS) within three types of molecular arrangements: monomers, oligomers and self-assembled monolayers (SAMs). While disordered monomers exhibit a variety of cooperative and local relaxation processes, the constrained nanodomains of oligomers and highly ordered structure of monolayers exhibit much hindered local molecular fluctuations. Particularly, in SAMs, motions of the silane headgroups are totally prevented whereas the polar endgroups forming the monolayer canopy show only one cooperative relaxation process. This latter molecular fluctuation is, for the first time, observed independently from other overlapping dielectric signals. Numerous electrostatic interactions among those dipolar endgroups are responsible for the strong cooperativity and heterogeneity of the canopy relaxation process. Our data analyses also revealed that the bulkiness of dipolar endgroups can disrupt the organization of the monolayer canopy thus increasing their ability to fluctuate as temperature is increased.

Conception and validation of A 3d printed learning model of supra condylar fracture of children.

The supracondylar fracture of the child is a common fracture. Its physiology, physiopathology and treatment use periosteum. As far as we know, there is no 3D printed model of this typical fracture in children with periosteum. The purposes of the research are to present the concept of an educational 3D printed supra condylar model with periosteum of the child and its expert validation. Materials and methods: The basis for the paediatric elbow model was a 3D scan of a four-year-old girl. Once the data had been extracted, the models were constructed using 3D Slicer®, Autodesk fusion 360® and Ultimaker Cura® software's. The Creality 3D Ender 6 SE Printer® used PLA filaments to print bone and TPU for periosteum. Printing took place at the University Hospital and the steps were modelled by hand. 3D printed bones and 3D printed periosteum were manually assembled. Participants: Expert validation with twelve paediatric orthopaedic surgeons took place in three University hospitals of the North of France. Results: Four Lagrange and Rigault 3D printed models of supracondylar fractures with periosteum were obtained with 200 h of design, printing and manual assembly based on a four-year-old elbow. According to the paediatric orthopaedic surgery experts, the size of the model is very good, but the model itself is of little interest compared to the information provided by the reconstruction of a 3D scanner. In total, with 9 out of 12 questions scoring higher than 8/10, the model was considered to be a good model for informing parents and teaching students. Conclusions: This study details the design of the first 3D-printed supra condylar fracture model in children with a full-size physeal and periosteum. The model has been validated by paediatric orthopaedic surgery experts.

Molecular motions in functional self-assembled nanostructures.

The construction of "smart" materials able to perform specific functions at the molecular scale through the application of various stimuli is highly attractive but still challenging. The most recent applications indicate that the outstanding flexibility of self-assembled architectures can be employed as a powerful tool for the development of innovative molecular devices, functional surfaces and smart nanomaterials. Structural flexibility of these materials is known to be conferred by weak intermolecular forces involved in self-assembly strategies. However, some fundamental mechanisms responsible for conformational lability remain unexplored. Furthermore, the role played by stronger bonds, such as coordination, ionic and covalent bonding, is sometimes neglected while they can be employed readily to produce mechanically robust but also chemically reversible structures. In this review, recent applications of structural flexibility and molecular motions in self-assembled nanostructures are discussed. Special focus is given to advanced materials exhibiting significant performance changes after an external stimulus is applied, such as light exposure, pH variation, heat treatment or electromagnetic field. The crucial role played by strong intra- and weak intermolecular interactions on structural lability and responsiveness is highlighted.

Production of Reproducible Filament Batches for the Fabrication of 3D Printed Oral Forms.

Patients need medications at a dosage suited to their physiological characteristics. Three-dimensional printing (3DP) technology by fused-filament fabrication (FFF) is a solution for manufacturing medication on demand. The aim of this work was to identify important parameters for the production of reproducible filament batches used by 3DP for oral formulations. Amiodarone hydrochloride, an antiarrhythmic and insoluble drug, was chosen as a model drug because of dosage adaptation need in children. Polyethylene oxide (PEO) filaments containing amiodarone hydrochloride were produced by hot-melt extrusion (HME). Different formulation storage conditions were investigated. For all formulations, the physical form of the drug following HME and fused-deposition modeling (FDM) 3D-printing processes were assessed using thermal analysis and X-ray powder diffraction (XRPD). Filament mechanical properties, linear mass density and surface roughness, were investigated by, respectively, 3-point bending, weighing, and scanning electron microscopy (SEM). Analysis results showed that the formulation storage condition before HME-modified filament linear mass density and, therefore, the oral forms masses from a batch to another. To obtain constant filament apparent density, it has been shown that a constant and reproducible drying condition is required to produce oral forms with constant mass.

Water-Induced Breaking of Interfacial Cohesiveness in a Poly(lactic acid)/Miscanthus Fibers Biocomposite.

The impact of the immersion in water on the morphology and the thermomechanical properties of a biocomposite made of a matrix of poly (lactic acid) (PLA) modified with an ethylene acrylate toughening agent, and reinforced with miscanthus fibers, has been investigated. Whereas no evidence of hydrolytic degradation has been found, the mechanical properties of the biocomposite have been weakened by the immersion. Scanning electron microscopy (SEM) pictures reveal that the water-induced degradation is mainly driven by the cracking of the fiber/matrix interface, suggesting that the cohesiveness is a preponderant factor to consider for the control of the biocomposite decomposition in aqueous environments. Interestingly, it is observed that the loss of mechanical properties is aggravated when the stereoregularity of PLA is the highest, and when increasing the degree of crystallinity. To investigate the influence of the annealing on the matrix behavior, crystallization at various temperatures has been performed on tensile bars of PLA made by additive manufacturing with an incomplete filling to enhance the contact area between water and polymer. While a clear fragilization occurs in the material crystallized at high temperature, PLA crystallized at low temperature better maintains its properties and even shows high elongation at break likely due to the low size of the spherulites in these annealing conditions. These results show that the tailoring of the mesoscale organization in biopolymers and biocomposites can help control their property evolution and possibly their degradation in water.

Quantifying Polymer Chain Orientation in Strong and Tough Nanofibers with Low Crystallinity: Toward Next Generation Nanostructured Superfibers.

Advanced fibers revolutionized structural materials in the second half of the 20th century. However, all high-strength fibers developed to date are brittle. Recently, pioneering simultaneous ultrahigh strength and toughness were discovered in fine (<250 nm) individual electrospun polymer nanofibers (NFs). This highly desirable combination of properties was attributed to high macromolecular chain alignment coupled with low crystallinity. Quantitative analysis of the degree of preferred chain orientation will be crucial for control of NF mechanical properties. However, quantification of supramolecular nanoarchitecture in NFs with low crystallinity in the ultrafine diameter range is highly challenging. Here, we discuss the applicability of traditional as well as emerging methods for quantification of polymer chain orientation in nanoscale one-dimensional samples. Advantages and limitations of different techniques are critically evaluated on experimental examples. It is shown that straightforward application of some of the techniques to sub-wavelength-diameter NFs can lead to severe quantitative and even qualitative artifacts. Sources of such size-related artifacts, stemming from instrumental, materials, and geometric phenomena at the nanoscale, are analyzed on the example of polarized Raman method but are relevant to other spectroscopic techniques. A proposed modified, artifact-free method is demonstrated. Outstanding issues and their proposed solutions are discussed. The results provide guidance for accurate nanofiber characterization to improve fundamental understanding and accelerate development of nanofibers and related nanostructured materials produced by electrospinning or other methods. We expect that the discussion in this review will also be useful to studies of many biological systems that exhibit nanofilamentary architectures and combinations of high strength and toughness.

Reducing the Gap between the Activation Energy Measured in the Liquid and the Glassy States by Adding a Plasticizer to Polylactide.

The kinetic fragility of a glass-forming liquid is an important parameter to describe its molecular mobility. In most polymers, the kinetic fragility index obtained from the glassy state by thermally stimulated depolarization current is lower than the one determined in the liquid-like state by dielectric relaxation spectroscopy, as shown in this work for neat polylactide (PLA). When PLA is plasticized to different extents, the fragility calculated in the liquid-like state progressively decreases, until approaching the value of fragility calculated from the glass, which on the other hand remains constant with plasticization. Using the cooperative rearranging region (CRR) concept, it is shown that the decrease of the fragility in the liquid-like state is concomitant with a decrease of the cooperativity length. By splitting the fragility calculated in the liquid, in two contributions: volume and energetic, respectively, dependent and independent on cooperativity, we observed that the slope of the fragility plot in the glass is equivalent to the energetic contribution of the fragility in the liquid. It is then deduced that the difference between the slopes of the relaxation time dependence calculated in both glass and liquid is an indicator of the cooperative character of the segmental relaxation when transiting from liquid to glass. As the main structural consequence of plasticization lies in the decrease of interchain weak bonds, it is assumed that these bonds drive the size of the CRR. In contrast, the dynamics in the glass are independent on plasticization structural effects.

Vitrification of two active pharmaceutical ingredients by fast scanning calorimetry: From structural relaxation to nucleation phenomena.

Cinchonidine and Theophylline vitrification abilities have been investigated by differential and fast scanning calorimetry. These active pharmaceutical compounds are known in the literature to have a very high tendency to crystallize which has been confirmed by classical differential scanning calorimetry. Due to the growing interest in amorphous pharmaceutical compounds, their possible vitrifications have been investigated by fast scanning calorimetry. This work shows the high potential of this advanced thermal analysis technique to investigate the vitrification of active pharmaceutical compounds by melt-quenching protocol. For the first time, glass transitions of Cinchonidine and Theophylline were measured. From Cinchonidine, it has been shown that complete glassy state can be obtained by cooling from the melt at 2000K/s. Crystallization has also been suppressed by cooling down from the melt at 2K/s. However, such rate does not avoid the formation of nuclei. Theophylline crystallization process has been suppressed by a melt-quenching protocol carried out with a cooling rate of 4000K/s. However, the phenomenon of nuclei formation upon cooling seems unavoidable at this cooling rate. For both active pharmaceutical compounds, physical aging has been observed to play a role on the nuclei formation below the glass transition leading to modify the subsequent crystallization.

Molecular Mobility of an Amorphous Chiral Pharmaceutical Compound: Impact of Chirality and Chemical Purity.

A dielectric relaxation spectroscopy (DRS) study was performed to investigate the molecular mobility of amorphous chiral diprophylline (DPL). For this purpose, both racemic DPL and a single enantiomer of DPL were considered. After fast cooling from the melt at very low temperature (-140 °C), progressive heating below and above the glass transition (Tg ≈ 37 °C) induces two secondary relaxations (γ- and δ-) and primary relaxations (α-) for both enantiomeric compositions. After chemical purification of our samples by means of cooling recrystallization, no γ-process could be detected by DRS. Hence, it was highlighted that the molecular mobility in the glassy state is influenced by the presence of theophylline (TPH), the main impurity in DPL samples. We also proved that the dynamic behavior of a single enantiomer and the racemic mixture of the same purified compound are quasi-identical. This study demonstrates that the relative stability and the molecular mobility of chiral amorphous drugs are strongly sensitive to chemical purity.

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.

Correlated and cooperative motions in segmental relaxation: Influence of constitutive unit weight and intermolecular interactions.

This work clarifies the notion of correlated and cooperative motions appearing during the α-relaxation process through the role of the molecular weight of the constitutive units and of the interchain dipolar interactions. By studying amorphous copolymers of poly(ethylene-co-vinyl acetate) with different vinyl acetate contents, we show that the correlated motions are not sensitive to the interchain dipolar interactions, in contrast to the cooperative motions, which increase with a strengthening of the intermolecular interactions for this sample family. Concerning the influence of the molecular weight m_{0}, the notion of "correlated motions" seems to be equivalent to the notion of "cooperative motions" only for low m_{0} systems.

Transformation of an active pharmaceutical ingredient upon high-energy milling: A process-induced disorder in Biclotymol.

This study investigates for the first time the thermodynamic changes of Biclotymol upon high-energy milling at various levels of temperature above and below its glass transition temperature (Tg). Investigations have been carried out by temperature modulated differential scanning calorimetry (TM-DSC) and X-ray powder diffraction (XRPD). Results indicate that Biclotymol undergoes a solid-state amorphization upon milling at Tg-45 °C. It is shown that recrystallization of amorphous milled Biclotymol occurs below the glass transition temperature of Biclotymol (Tg=20 °C). This displays molecular mobility differences between milled Biclotymol and quenched liquid. A systematic study at several milling temperatures is performed and the implication of Tg in the solid-state transformations generally observed upon milling is discussed. Influence of analysis temperature with respect to interpretation of results was investigated. Finally, it is shown that co-milling Biclotymol with only 20 wt% of amorphous PVP allows a stable amorphous dispersion during at least 5 months of storage.

Molecular Relaxations in Supercooled Liquid and Glassy States of Amorphous Quinidine: Dielectric Spectroscopy and Density Functional Theory Approaches.

In this article, we conduct a comprehensive molecular relaxation study of amorphous Quinidine above and below the glass-transition temperature (Tg) through broadband dielectric relaxation spectroscopy (BDS) experiments and theoretical density functional theory (DFT) calculations, as one major issue with the amorphous state of pharmaceuticals is life expectancy. These techniques enabled us to determine what kind of molecular motions are responsible, or not, for the devitrification of Quinidine. Parameters describing the complex molecular dynamics of amorphous Quinidine, such as Tg, the width of the α relaxation (ßKWW), the temperature dependence of α-relaxation times (τα), the fragility index (m), and the apparent activation energy of secondary γ relaxation (Ea-γ), were characterized. Above Tg (> 60 °C), a medium degree of nonexponentiality (ßKWW = 0.5) was evidenced. An intermediate value of the fragility index (m = 86) enabled us to consider Quinidine as a glass former of medium fragility. Below Tg (< 60 °C), one well-defined secondary γ relaxation, with an apparent activation energy of Ea-γ = 53.8 kJ/mol, was reported. From theoretical DFT calculations, we identified the most reactive part of Quinidine moieties through exploration of the potential energy surface. We evidenced that the clearly visible γ process has an intramolecular origin coming from the rotation of the CH(OH)C9H14N end group. An excess wing observed in amorphous Quinidine was found to be an unresolved Johari-Goldstein relaxation. These studies were supplemented by sub-Tg experimental evaluations of the life expectancy of amorphous Quinidine by X-ray powder diffraction and differential scanning calorimetry. We show that the difference between Tg and the onset temperature for crystallization, Tc, which is 30 K, is sufficiently large to avoid recrystallization of amorphous Quinidine during 16 months of storage under ambient conditions.

Crystallization kinetics and molecular mobility of an amorphous active pharmaceutical ingredient: A case study with Biclotymol.

The present case study focuses on the crystallization kinetics and molecular mobility of an amorphous mouth and throat drug namely Biclotymol, through differential scanning calorimetry (DSC), temperature resolved X-ray powder diffraction (TR-XRPD) and hot stage microscopy (HSM). Kinetics of crystallization above the glass transition through isothermal and non-isothermal cold crystallization were considered. Avrami model was used for isothermal crystallization process. Non-isothermal cold crystallization was investigated through Augis and Bennett model. Differences between crystallization processes have been ascribed to a site-saturated nucleation mechanism of the metastable form, confirmed by optical microscopy images. Regarding molecular mobility, a feature of molecular dynamics in glass-forming liquids as thermodynamic fragility index m was determined through calorimetric measurements. It turned out to be around m=100, describing Biclotymol as a fragile glass-former for Angell's classification. Relatively long-term stability of amorphous Biclotymol above Tg was analyzed indirectly by calorimetric monitoring to evaluate thermodynamic parameters and crystallization behavior of glassy Biclotymol. Within eight months of storage above Tg (T=Tg+2°C), amorphous Biclotymol does not show a strong inclination to crystallize and forms a relatively stable glass. This case study, involving a multidisciplinary approach, points out the importance of continuing looking for stability predictors.