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This work aimed at studying the influence of a post drawing process on the morphology and the gas permeability of a PBSA (Polybutylene succinate-co-adipate) film. Two films were studied, one of neat PBSA and one filled with 1%wt of silica. The influence of silica was also studied. Reference films of PBSA and PBSA + Si presented a spherulitic morphology despite a difference of spherulites sizes and long period. After stretching, this isotropic morphology changed to an oriented one, as shown by WAXS measurements. SAXS analysis revealed that stretching led to a lamellae organization in the stretching direction, with lamellae oriented perpendicular to the stretching direction. Thermal characterizations have shown that stretching did not modified the degree of crystallinity for both systems. The helium, carbon dioxide and oxygen permeability increased with stretching, mainly due to the orientation of crystalline lamellae, decreasing the diffusion path. Moreover, for PBSA + Si stretched films, small non-percolating voids were evidenced around the silica particles which could also make gas transport easier. Thus, for both systems, this increase in gas permeability happened in a different way. [Display omitted] • Uniaxial drawing was carried out on films of PBSA and PBSA with low amount of silica. • The impact of drawing on PBSA crystalline morphology and orientation was investigated. • Gas permeability was studied for the reference and drawn films. • Relationships between the gas permeability and the morphology were established. [ABSTRACT FROM AUTHOR]

The present works describes the Passerini modification of carboxymethyl cellulose (CMC) by using a library of nine α-substituted ketones derivatives, differing in their hydrophobicity and reactivity, conjointly with cyclohexyl isocyanide. The Passerini ligation, achieved in aqueous and mild conditions, was shown to be successful, leading to a large panel of dually functionalized CMC derivatives, in an eco-friendly manner. A particular attention was dedicated to the influence of the experimental parameters such as the stoichiometry, the nature of a co-solvent or the temperature, which allowed to tune the extent of modification. The reactivity of the ketone was proven to be governed by its i) compatibility with water, ii) sterical accessibility, and by iii) the presence of neighboring electron-withdrawing group. The resulting Passerini CMC products modified by methacrylate moieties (CMC-MA) were used as reactive macromonomer under a "grafting through" approach. The copolymerization of CMC-MA with oligoethylene glycol methacrylate (OEGMA) and diethylene glycol methacrylate (DEGMA) upon thermal radical reaction conditions enabled to generate tightly cross-linked chemical hydrogels, with a thermo-sensitive and thermo-reversible behavior, reflected by a macroscopical shrinkage/swelling response, and confirmed by SAXS analysis. Such chemical strategy paves the way toward multifunctional polysaccharide-based networks with potential utilizations as drug delivery devices, dye removals or actuators. [Display omitted] [ABSTRACT FROM AUTHOR]

In this study, we report on the simple and straightforward preparation of ionogels arising from the addition of guar gum (a plant-based polysaccharide) in a solution of precisely-defined poly(ionic liquid) chains (PIL) in imidazolium-based ionic liquid (IL). The development of intermolecular polar interactions (mainly hydrogen bonds) and topologic chain entanglements induces the formation of physical biohybrid ionogels, whose elastic properties can be easily tuned by varying the composition (up to 30 000 Pa). The combined presence of guar gum and PIL confers excellent dimensional stability to the ionogels with no IL exudation combined with high thermal properties (up to 310 °C). The resulting materials are shown to exhibit gel scattering profiles and high conductivities (> 10 −4 S/cm at 30 °C). The benefit linked to the formation of guar/PIL associations in IL medium enables to find a good compromise between the mechanical cohesion and the mobility ensuring the ionic transport. [ABSTRACT FROM AUTHOR]

Abstract: The formation of interpolymer complexes (IPC) between poly(acrylic acid) (PAA) and poly(acrylamide) (PAM), poly(N,N-dimethylacrylamide) (PDMA), and statistical copolymers of acrylamide (AM) and N,N-dimethylacrylamide (DMA) has been studied as a function of pH, salt concentration and temperature (0–70 °C). The cloud points of dilute solutions were measured by turbidimetry and phase diagrams were determined as a function of temperature and pH in pure water and as a function of pH and salt concentration at room temperature. For each temperature and salt concentration a critical pH (pHcrit) below which IPC are observed was defined. In the case of PAA/PAM, pHcrit continuously decreased with increasing temperature, from pH 3.5 at 0 °C to pH 1.9 at 60 °C (UCST-type). In the case of PAA/PDMA, pHcrit, increased with temperature. The LCST-type behavior of the hydrogen-bonding complex formed between PAA and PDMA was attributed to the dimethyl substitution of amide groups that puts in hydrophobic interactions at high temperature. PAA and statistical copolymers P(AM-co-DMA) showed an intermediate behavior between PAA/PAM and PAA/PDMA with a continuous shift from UCST-type to LCST-type with increasing amount of DMA. This behavior can be attributed to changes in configurational entropy due to the IPC formation and (for PDMA) to the release of water molecules initially confined in hydrophobic hydration cages around DMA units. While at low salt concentration, the stability of PAA/PAM and PAA/PDMA complexes only slightly increases with the screening of ionized acrylic units, there is a sharp increase of pHcrit at high salt concentration in relation with the weakening of the solvent quality. In this regime, the complex formation of PAA/PDMA is greatly enhanced compared to PAA/PAM due to the interference of hydrophobic interactions. [Copyright &y& Elsevier]

RAFT-made poly(ionic liquid) chains (PIL), poly(1-[2-acryloylethyl]-3-methylimidazolium bromide) (Poly [AEmim][Br]), have been mixed with a ionic liquid (IL), namely butylmethylimidazolium chloride ([C4mim][Cl].) The similarities in terms of structure and polarity of these molecular and macromolecular imidazolium derivatives led to homogeneous and transparent solutions. The influence of the chain molar mass and the concentration was examined through rheology investigation. It was established that the steady-shear viscosity of the solutions, and the viscoelastic properties can be finely tuned by these two parameters and by temperature. The thermal-dependence of the rheological features allowed for determining high activation energies (E a) (around 80 kJ/mol), compared to analogous PIL aqueous solutions. Such E a values reflect high cohesion in PIL/IL solutions, related to the formation of multiple strong interactions, such as hydrogen bonds, van der Waals forces and Coulomb interactions between ionic species. Wide-angle and small-angle X-ray scattering experiments as well as scanning electron microscopy analysis evidenced a multi-scale local homogeneity of the PIL/IL solutions, which additionally exhibit high ionic conductivity (ca. 10−3 S/cm at 30 °C), as measured by broadband dielectric spectroscopy. [Display omitted] • Never described mixtures composed of poly([AEmim][Br]) and [C4mim][Cl] were investigated and characterized. • The rheological properties were tuned both by the molar mass and the concentration of poly(ionic liquid). • A reinforced cohesion, due to H-bonds and electrostatic interactions, was obtained within the mixtures. • High ionic conductivity can be reached, offering applicative potential notably in the field of energy devices. [ABSTRACT FROM AUTHOR]

In this work, we propose the formation of stretchable hydrogels at neutral pH from the physical crosslinking of chitosan (CS) and hyaluronic acid (HA) by polyelectrolyte complexation. A mixture of CS (M w ≈ 600 kg/mol, degree of acetylation ≈ 50 %) solution and HA (M w ≈ 77 kg/mol) solution was prepared with an excess of salts screening the electrostatic interactions CS/HA. In a controlled manner, the polyelectrolyte complexation was induced through the progressive dialysis of the salted polymer mixture against a sodium acetate solution (AcONa, 0.01 M) for 7 days. Depending on [HA], various materials were obtained: viscous solutions at [HA] = 0.75 % (w/v); hydrogels at [HA] = 1.50–2.24 % (w/v) with Young modulus of 14 kPa and stretchable to 200 %. The small angle X-ray scattering characterization of the hydrogels revealed a multiscale organization related to the conformation of the polymers induced by the physical interactions. The dialysis process with AcONa was optimized by adding a dialysis step against a zinc acetate solution containing Zn2+. The combination of polyelectrolyte complexation between CS/HA and metal complexation between Zn2+ and the polymers led to an enhancement of the hydrogel stretchability up to 400 %. [Display omitted] [ABSTRACT FROM AUTHOR]

In-situ coupled mechanical/electrical investigations on EPDM-based composite materials prepared using CB fillers of different (low and high) structure and at different concentrations have been carried-out by cyclic and continuous loading, with simultaneous measurements of stress, strain and electrical conductivity. By investigations in dependence on the strain amplitude and unloading rate, the relationship linking the evolution of the electrical conductivity during mechanical deformation to the mechanical Mullins effect is demonstrated. A characteristic electrical signature accompanying the mechanical Mullins effect is revealed, originating from a kinetic reorganisation of the CB fillers by competing mechanisms of de-percolation and re-percolation. Notable differences between the electrical and the mechanical Mullins effect are also found, in particular, in relation to the kinetics of the stabilization of properties after the first mechanical deformation cycle. Our study brings new light into understanding the coupled evolution of mechanical and electrical properties of elastomeric composite materials, with possible applications in monitoring the material properties under mechanical deformation by in-situ electrical measurements. [Display omitted] [ABSTRACT FROM AUTHOR]

• Plasticization of CA is carried out with octanoic acid, ethyl and butyl lactate. • OA, EL, BL decrease the mechanical relaxation of the CA. • BL supresses totally the crystalline region of the CA. • A representation of the behavior of CA with the increasing plasticizer is proposed. • Two relaxations appear explained by the concept of CA and plasticizer rich phases. This work brings together thermo-mechanical and structural information for plasticized cellulose acetate (CA) by lactates and octanoic acid. CA are processed with plasticizer due to their high Tg and their strong H-bonding network. We prepared CA / plasticizer blends by corotative twin screw extruder and by solvent casting methods. The study of the different relaxations and of the glassy zone modulus was performed by dynamic mechanical analysis (DMA). The miscibility range of cellulose acetate blends were identified by the analysis of the tan δ. Depending on the composition of the system, one or two transitions are noted, this last result indicates the presence of a phase rich in CA and another in plasticizer. To connect this information to crystallinity and molecular organization, X-ray diffraction analyses were carried out. The disappearance of crystallinity allows the plasticization of previously inaccessible zones, causing a glassy modulus drop of more than 1000 MPa. [ABSTRACT FROM AUTHOR]

In-situ coupled mechanical/electrical investigations on TPU-based nanocomposite materials filled with carbon black have been carried-out under continuous and cyclic mechanical loading, with simultaneous measurements of stress, strain and electrical conductivity as function of the strain rate and amplitude. The impact of mechanical deformation and thermal treatment on the structure/properties relationship has been investigated by employing SAXS/WAXS, DSC and TEM measurements. Higher conduction properties were through dynamic percolation induced by TPU soft domains crystallization. The TPU hard domains were found to be more sensitive to thermal treatment: annealing at high temperature led to microcrystalline hard domains that strongly influenced the conductivity evolution upon mechanical deformation. Structural and morphological reorganizations induced by mechanical deformation and thermal treatment can be thus efficiently used to adjust the coupled electro-mechanical behavior of TPU-based composite materials. [Display omitted] • Strain induced crystallization of TPU soft domains enhanced the electrical conductivity. • The stress and strain at failure of conductive CB/TPU composite increase with the loading rate. • Thermo-mechanical treatment can be used to guide the electrical properties of conductive CB/TPU composite. [ABSTRACT FROM AUTHOR]

In situ coupled mechanical/electrical/WAXS/SAXS investigations on EPDM-based composite materials filled with carbon black (CB) have been performed under uniaxial tensile stretching. The time-resolved correlation between the electrical conductivity and the microstructural state of the composite reveals the mechanisms governing the structure/properties relationships with increasing deformation: orientation of the EPDM chains with reorganization of the CB network and ultimately, nano-cavitation. This involvement of different microstructural phenomena offers a comprehensive picture of the mechanisms underlying the non-monotonic evolution of the electrical conductivity with strain. At large deformations, the formation of nanovoids preceding the material fracture induces by a significant decrease in conductivity. Our study thus brings new light on the conductivity/strain relationships of carbon black filled elastomers. We envision potential applications in developing smart rubber materials where microstructural changes preceding material rupture can be monitored in situ by coupled electrical measurements. [Display omitted] • SAXS/WAXS/Conductivity measurements were performed during deformation up to rupture. • The evolution of conductivity in EPDM-CB nanocomposites displays a maximum with extension ratio • Orientation of polymer chains and transverse interpenetration/contacting of CB occur first. • Then, cavitation limits and decrease conductivity at high extension ratios. • Conductivity measurements can be performed to detect cavitation in CB-filled elastomers. [ABSTRACT FROM AUTHOR]