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Lemercier A.,CNRS Separative Sciences and Methods | Viel Q.,CNRS Separative Sciences and Methods | Viel Q.,CNRS Laboratory for the Characterization of Amorphous Polymers | Brandel C.,CNRS Separative Sciences and Methods | And 4 more authors.
Journal of Crystal Growth | Year: 2017

Since more and more pharmaceutical substances are developed as amorphous forms, it is nowadays of major relevance to get insights into the nucleation and growth mechanisms from supercooled melts (SCM). A step-by-step approach of recrystallization from a SCM is presented here, designed to elucidate the impact of various experimental parameters. Using the bronchodilator agent Diprophylline (DPL) as a model compound, it is shown that optimal conditions for informative observations of the crystallization behaviour from supercooled racemic DPL require to place samples between two cover slides with a maximum sample thickness of 20. μm, and to monitor recrystallization during an annealing step of 30. min at 70. °C, i.e. about 33. °C above the temperature of glass transition. In these optimized conditions, it could be established that DPL crystallization proceeds in two steps: spontaneous nucleation and growth of large and well-faceted particles of a new crystal form (primary crystals: PC) and subsequent crystallization of a previously known form (RII) that develops from specific surfaces of PC. The formation of PC particles therefore constitutes the key-step of the crystallization events and is shown to be favoured by at least 2.33. wt% of the major chemical impurity, Theophylline. © 2017.


Bouthegourd E.,CNRS Laboratory for the Characterization of Amorphous Polymers | Esposito A.,CNRS Laboratory for the Characterization of Amorphous Polymers | Lourdin D.,French National Institute for Agricultural Research | Saiter A.,CNRS Laboratory for the Characterization of Amorphous Polymers | Saiter J.M.,CNRS Laboratory for the Characterization of Amorphous Polymers
Physica B: Condensed Matter | Year: 2013

By using Donth's model, the size of the Cooperative Rearranging Regions (CRR) at the glass transition was determined from TM-DSC measurements on two glassy biopolymers with different molecular structures (amylose and amylopectin) as well as on starch, which is the mixture of amylose and amylopectin as it is obtained during its biosynthesis. For these materials, the δACp values at Tg and the values of the fragility index (m) were determined by conventional DSC. The fragility concept was then analyzed by taking into account the existence of two contributions: m10 (the so-called isochoric fragility, which is a pure thermal contribution) and (which incorporates the effects due to volume and density fluctuations). Whenever the molecular structure of a glass-forming liquid involves non-linear sequences of rigid and sterically hindered repeating units with high densities of hydrogen bonds, the fragility is found to be governed only by the temperature; the contribution of the volume (density and pressure contribution) has a quasi-nil effect. © 2013 Elsevier BY. All rights reserved.


PubMed | Lille University of Science and Technology, Pharmasynthese Inabata Group, CNRS Laboratory for the Characterization of Amorphous Polymers and University of Rouen
Type: Journal Article | Journal: International journal of pharmaceutics | Year: 2016

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.


Delpouve N.,CNRS Laboratory for the Characterization of Amorphous Polymers | Stoclet G.,University of Lille Nord de France | Saiter A.,CNRS Laboratory for the Characterization of Amorphous Polymers | Dargent E.,CNRS Laboratory for the Characterization of Amorphous Polymers | Marais S.,CNRS Polymers, Biopolymer and Surfaces Laboratory
Journal of Physical Chemistry B | Year: 2012

Crystallization is among the easiest ways to improve polymer barrier properties because of the tortuosity increase within the material and the strong coupling between amorphous and crystalline phases. In this work, poly(lactic acid) (PLA) films have undergone α∼ thermal crystallization or different drawing processes. Although no effect of α∼ thermal crystallization on water permeability is observed, the drawing processes lead to an enhancement of the PLA barrier properties. This work clearly shows that, in the case of PLA, the crystallinity degree is not the main parameter governing the barrier properties contrary to the crystalline and amorphous phase organizations which play a key role. X-ray analyses confirm that the macromolecular chain orientation in the amorphous phase is the main cause of the improvement of the drawn PLA water barrier property. This improvement is due to the orthotropic structure formation for sufficient draw ratios, particularly when using the Simultaneous Biaxial drawing mode. Moreover, independently of the draw conditions, the drawing process tends to reduce the plasticization coefficient. Consequently, the drawn material barrier properties are not much affected by the water passage. © 2012 American Chemical Society.


Lixon Buquet C.,CNRS Laboratory for the Characterization of Amorphous Polymers | Lixon Buquet C.,CNRS Polymers, Biopolymer and Surfaces Laboratory | Hamonic F.,CNRS Laboratory for the Characterization of Amorphous Polymers | Saiter A.,CNRS Laboratory for the Characterization of Amorphous Polymers | And 3 more authors.
Thermochimica Acta | Year: 2010

The thermal behaviour, the physical ageing and the amorphous phase dynamics of polysulfone (PSU) and sulfonated polysulfone (SPSU) are characterized by thermogravimetric analysis and temperature modulated differential scanning calorimetry. The sulfonic group introduction (the sulfonation degree is 70%) in the polymer implies a drastic decrease of the thermal decomposition temperature (220 and 517 °C for SPSU and PSU respectively) and a modification of calorimetric parameters (for SPSU, the heat capacity in the glassy state is lower and the glass transition temperature Tg is higher than for PSU). In terms of molecular dynamics, the amorphous phase heterogeneities are greater and the cooperative rearranging region size at the glass transition temperature is smaller for SPSU than for PSU. Moreover, after a physical ageing process, the enthalpy recovery kinetic has slowed down by sulfonation. These results can be explained from the existence of sulfonic domains confining the amorphous phase domains. © 2010 Elsevier B.V.


Tenn N.,CNRS Polymers, Biopolymer and Surfaces Laboratory | Follain N.,CNRS Polymers, Biopolymer and Surfaces Laboratory | Fatyeyeva K.,CNRS Polymers, Biopolymer and Surfaces Laboratory | Valleton J.-M.,CNRS Polymers, Biopolymer and Surfaces Laboratory | And 3 more authors.
Journal of Physical Chemistry C | Year: 2012

Poly(ethylene-co-vinyl alcohol) (EVOH) films with two different ethylene contents (29 and 44 mol %) have been treated by hydrophobic plasma (CF 4, tetramethylsilane (TMS), CF 4/H 2, and CF 4/C 2H 2). Conditions of the cold plasma treatment were optimized by the water contact angle measurements as a function of the different plasma parameters (plasma power, gas flow, and treatment time). Chemical changes of the film surface were characterized by X-ray photoelectron spectroscopy. The obtained results revealed the presence of fluorine containing functional groups such as CF, CF 2, and CF 3 in the case of CF 4, CF 4/H 2, and CF 4/C 2H 2 plasma treatment and the presence of SiO xC y compounds after TMS treatment. The morphology of the plasma treated EVOH films was examined by atomic force microscopy, which indicated an increase of the film roughness after treatment. Negligible changes of thermal properties of the modified EVOH films were observed by means of the temperature modulated differential scanning calorimetry. The barrier properties of films were characterized by water permeability measurements. It was found that the hydrophobicity was significantly improved after plasma treatment and for some treated films the water permeability was decreased up to 28%. © 2012 American Chemical Society.


Delpouve N.,CNRS Laboratory for the Characterization of Amorphous Polymers | Saiter A.,CNRS Laboratory for the Characterization of Amorphous Polymers | Dargent E.,CNRS Laboratory for the Characterization of Amorphous Polymers
European Polymer Journal | Year: 2011

Effects of stereoregularity and crystallization mode on the amorphous phase dynamics are investigated for poly(lactic acid) PLA. An isothermal crystallization from the melt and a cold crystallization are imposed. For each PLA, the cold crystallization leads to the appearance of a less perfect crystalline phase and to an important rigid amorphous fraction RAF content (35%), although only 10% of RAF is generated after crystallization from the melt. Temperature Modulated Differential Scanning Calorimetry is used to determine the Cooperative Rearranging Regions (CRR) size at the glass transition temperature in the mobile amorphous phase MAP. It is shown that the CRR size in the MAP is not modified by the appearance and the spherulite growth. For the intra-spherulite MAP, a confining effect is evidenced, causing an amorphous phase thickness decrease during crystallization, and inducing a drastic CRR size reduction. © 2011 Elsevier Ltd. All rights reserved.


Delpouve N.,CNRS Laboratory for the Characterization of Amorphous Polymers | Vuillequez A.,CNRS Laboratory for the Characterization of Amorphous Polymers | Saiter A.,CNRS Laboratory for the Characterization of Amorphous Polymers | Youssef B.,CNRS Laboratory for the Characterization of Amorphous Polymers | Saiter J.M.,CNRS Laboratory for the Characterization of Amorphous Polymers
Physica B: Condensed Matter | Year: 2012

Molecular dynamics at the glass transition of three lactose/oil glassy systems have been investigated according to the cooperativity and fragility approaches. From Donths approach, the cooperativity length is estimated by modulated temperature calorimetric measurements. Results reveal that modification of the disaccharide by oil leads to increase the disorder degree in the lactose, the size of the cooperative domains and the fragility index. These particular hydrogen-bonded organic glasses follow the general tendency observed on organic and inorganic polymers: the higher the cooperativity length, the higher the value of the fragility index at T g. © 2012 Elsevier B.V. All rights reserved.


Couderc H.,CNRS Laboratory for the Characterization of Amorphous Polymers | Saiter A.,CNRS Laboratory for the Characterization of Amorphous Polymers | Grenet J.,CNRS Laboratory for the Characterization of Amorphous Polymers | Saiter J.M.,CNRS Laboratory for the Characterization of Amorphous Polymers
Physica B: Condensed Matter | Year: 2011

Temperature Modulated Differential Scanning Calorimetry (TMDSC) is used to estimate Cooperative Rearranging Region (CRR) average sizes for polymer/clay nanocomposites, obtained by mixing polyethylene 1,4-cyclohexylenedimethylene terephthalate glycol (PETg) filled and organically modified nanoclay (C15A) following a master-batch process. Two different basal distances are obtained. It is shown that the greater the basal distance and the nanofiller content, the lower the heat capacity step at the glass transition temperature ΔCp(Tg), and the lower the CRR volume. It is also shown that the evolution of the CRR volume is consistent with the evolution of the fragility index obtained by DSC and Broadband Dielectric Spectroscopy (BDS) when the nanofiller content changes. The fragility index and the CRR size decreases can be correlated to nanofiller presence, hindering the molecular movements. From the Vollenberg and Heikens [34] approach, this behaviour can also be interpreted through the existence of an interfacial bilayer. This interfacial bilayer is composed by a zone, which is next to the nanofiller, with a density higher than the matrix one, followed by a more expanded zone with a density lower than the matrix one. © 2011 Elsevier B.V. All rights reserved.


Hamonic F.,CNRS Laboratory for the Characterization of Amorphous Polymers | Saiter A.,CNRS Laboratory for the Characterization of Amorphous Polymers | Prevosto D.,CNR Institute of Neuroscience | Dargent E.,CNRS Laboratory for the Characterization of Amorphous Polymers | Saiter J.M.,CNRS Laboratory for the Characterization of Amorphous Polymers
AIP Conference Proceedings | Year: 2012

The temperature dependence of structural relaxation time in drawn polyethylene terephthalate glycol and polyethylene terephthalate has been studied. A transition from fragile to strong behaviour is observed in drawn polyethylene terephthalate, which can be related to the decrease of Cooperative Rearranging Regions in such systems. The decrease is mainly due to the crystallization of the sample. Drawing the amorphous polyethylene terephthalate glycol poduces only small effects on its relaxation dynamics. © 2012 American Institute of Physics.

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