Marie-Claude Heuzey

Polylactide (PLA) is one of the most widely studied biodegradable polymers. However, poly(meso-lactide) (PMLA), an amorphous PLA, remains poorly characterized. This study investigates the thermal, rheological behavior, and morphology of poly(l-lactide) (PLLA) and PMLA blends across a wide composition range. Characterizations were performed using differential scanning calorimetry (DSC), small amplitude oscillatory shear (SAOS) rheology, and atomic force microscopy (AFM). Nanoscale heterogeneity is suspected for the 10% and 90% w/w% HMW PLLA/HMW PMLA compositions, while 30 w% HMW PLLA, 50 w% HMW PLLA, and 70 w% HMW PLLA compositions exhibited immiscibility. DSC revealed two glass transition temperatures for 30 w% HMW PLLA, 50 w% HMW PLLA, and 70 w% HMW PLLA blends, corresponding to those of the neat phases, 48.2 ± 0.1 °C for HMW PMLA and 61.8 ± 0.4 °C for HMW PLLA, and a single Tg for the 10% and 90% w/w% HMW PLLA/HMW PMLA composition blends. AFM revealed an emulsion-type morphology at 30 and 70 wt. % HMW PLLA compositions and a co-continuous structure at 50 wt. % HMW PLLA. SAOS results presented a shoulder in the low frequency storage modulus for all blends. The Palierne model was used to fit the dynamic data of the blends and estimated the dispersed phase relaxation time, reinforcing the immiscibility conclusions. Relaxation spectra were obtained for all blends, showing two distinct relaxation modes associated with PLA nature and the interfacial tension of the blend. These results suggest that PMLA and PLLA are largely immiscible.

This work aims to investigate the effects of the melt electrospinning process on the properties of ternary blend poly(ε-caprolactone)/poly(ethylene oxide)/poly(ethylene glycol) (PCL/PEO/PEG) fibers. The utterly different morphology of the specimens before and after melt electrospinning acknowledges the significant effect of melt electrospinning on the sample’s properties. However, it does not chemically alter the samples. The Scanning Electron Microscope (SEM) images showed that PEO and PEG behave differently in the PCL matrix, producing distinctly different morphologies in the respective binary blend fibers. Differences in morphology also lead to differences in the crystallization behavior of the specimen. Wide-angle X-ray diffraction (XRD) and differential scanning calorimetry (DSC) also reveal that although PEO and PEG are fundamentally the same polymer with different molecular weights, their behaviors in the PCL matrix are entirely different; PEG mostly remains in the amorphous state, while PEO can form its crystalline structure. Hence, the final morphology of the ternary melt electrospun fiber is a combination of the morphology of PCL/PEO and PCL/PEG binary blends. Preliminary biological tests showed that the porosity created by the removal of the PEO and PEG hydrophilic phases improved fibroblast metabolic activity, highlighting the potential of this system for further investigation in bone tissue engineering applications.

Materials based on polymer microfibers, displaying a high surface-to-volume ratio and porosity, are used in applications including filtration membranes, wound dressing materials, textiles, etc., and controlling both their internal morphology and assembly can enhance the resulting properties. However, the full range of accessible morphological states within multiphase polymer microfibers, displaying highly confined lateral dimensions and subjected to significant elongational deformation, remains only partially explored and understood. In this work, the addition of a polystyrene-block-poly(ε-caprolactone) (PS-b-PCL) diblock copolymer to a model system of melt electrospun PS/PCL immiscible binary system, yields rich arrays of complex morphologies and assemblies, including a novel type of self-supporting PS fibrillar microfibers reminiscent of multistrand yarn, microfibers with dense arrays of highly oriented sub-μm channels, and mats composed of sub-μm polymer fibrils. Indeed, compatibilized systems initially displaying a matrix-dispersed phase morphology (PS/PCL 20/80 vol %) show gradually finer PS fibrils dispersed in a PCL sheath with increasing copolymer content. Selectively dissolving the PCL sheath resulted in the formation of mats composed of well separated, very fine sub-μm (down to 60 nm) PS fibrils. In contrast, compatibilized blends initially displaying a cocontinuous morphology (PS/PCL 50/50 vol %) yielded fibrillar/multistrand PS microfibers displaying self-supporting properties once the PCL was extracted. The block copolymer plays a critical role: it significantly suppresses coalescence, yielding a finer morphology; at the same time, its significant dilution at the interface during the stretching process may allow limited coalescence of neighboring PS fibrils due to reduced steric hindrance, creating new junctions, as copolymer areal density calculations support. The resulting PS fibrillar microfibers exhibit dramatically increased specific surface areas compared to the original microfibers—up to over 2 orders of magnitude greater, consistent with geometrical predictions.

The presence of cellulose in wastewater can hinder the detection of microplastics (MPs) or lead to their misidentification as MPs. Existing digestion protocols, such as H2O2, are often ineffective for removing cellulosic components of organic matter. This study examined the isolation of cellulose from microplastics in wastewater using cupriethylenediamine (CED). Cellulosic materials, including cotton balls, hygienic paper, and paper rolls, were used to simulate wastewater cellulose matrices and treated with CED (0.1, 0.3, and 0.5 M) at 22 °C over varying contact times. The optimal CED condition was evaluated for its impact on microplastics (PET, PS, and PA) and applied to influent wastewater. The optimal CED (0.3 M) removed up to 100% of the cellulosic products and preserved microplastic integrity, as confirmed by 100% weight recovery, unchanged morphology from scanning electron microscopy (SEM) validated with ImageJ, and a stable carbonyl index from Fourier-transform infrared spectroscopy. Further, 0.3 M CED at 30 min isolated MPs from wastewater samples masked by cellulose, achieving 98% cellulose removal and enabling the detection of several microplastics ranging in size from 71 to 3176 μm, with PET as the predominant MPs. This work presents a rapid approach for removing cellulose, facilitating microplastics detection in wastewater.

Bone defects that are beyond the body's natural repair capacity remain a significant challenge in bone tissue engineering. In recent years, various synthetic materials have been introduced as potential alternatives for repairing these defects, but most of them have limitations. In particular, calcium phosphate cements (CPCs) possess desirable bioactivity but poor mechanical strength. Polymethyl methacrylate (PMMA) exhibits high structural stability but lacks adequate degradability and bioactivity. These obstacles highlight the need to develop materials that balance structural integrity with biological function. In this study, poly-ε-caprolactone/polyethylene oxide/polyethylene glycol (PCL/PEO/PEG) nanocomposite scaffolds containing hydroxyapatite nanoparticles (nHA) were fabricated using solvent-free melt electrospinning and assessed for their physical, chemical, and biological properties. Three masterbatch systems (nHA@PCL, nHA@PEO, and nHA@PEG) and varying percentages of nanoparticles (1, 5, 10, and 20%) were investigated. The results showed that the nHA@PCL system resulted in better stability of nanoparticles after immersion, and ternary blend (PCL/PEO/PEG) scaffolds, especially Ternary-nHA10@PCL (PCL/PEO/PEG-nHA10@PCL), provided the highest hydrophilicity, cell adhesion, cellular metabolic activity, cell proliferation by DNA counting, and calcification deposition. Overall, blending nHA with PCL as the main component, along with the presence of hydrophilic polymers such as PEO and PEG, is an effective strategy for simultaneously promoting human osteoblast and vascular endothelial cell growth and activity, and Ternary-nHA10@PCL is introduced as the optimal option.

Multiwalled carbon nanotubes (MWCNTs) were dispersed and distributed via a co‐rotating twin‐screw extruder (TSE) in high (h)‐ and low (l)‐molecular‐weight amorphous and semicrystalline polylactides (PLAs) (aPLA and scPLA, respectively). Effects of PLA molecular weight and D‐lactic acid equivalents content (D‐content), as well as processing parameters, were examined on the MWCNT dispersion quality in PLA. The effectiveness of the MWCNT dispersion in various PLA matrices was investigated using scanning electron microscopy (SEM) and small‐amplitude oscillatory and transient shear flow rheometry in the molten state. The results showed a better dispersion of MWCNTs in the low‐molecular‐weight PLA grades (aPLAl and scPLAl). In addition, better MWCNT dispersion was observed in aPLA grades when processed at a higher temperature of 190°C than at 150°C. At 150°C, while MWCNT bundles in aPLAl could be broken down, a good dispersion could not be achieved in aPLAh due to the lower molecular mobility at such a temperature. The electrical conductivity of the samples was also shown to increase as the MWCNT dispersion was improved. The existence of crystallites in scPLA‐based nanocomposites, however, disrupted the connectivity of the MWCNTs and decreased the final electrical conductivity. The lower molecular weight aPLAl prepared at 190°C showed the highest electrical conductivity (~10⁻⁵ S/m) at a low loading of 0.5 wt.% MWCNTs.