External and Reversible CO₂ Regulation of Ring-Opening Polymerizations Based on a Primary Alcohol Propagating Species

We report the use of an organic catalyst system capable of switching between active and dormant propagating states during the ROP of cyclic monomers. While the ROP of both ε-caprolactone and trimethylene carbonate proceeds under nitrogen, the simple addition of CO₂ results in a dormant “off” state. Cycling between atmospheres provides the ability to regulate the molecular weights of the resulting polymers without appreciable loss of catalytic activity for several “on/off” cycles

Electroassisted Functionalization of Nitinol Surface, a Powerful Strategy for Polymer Coating through Controlled Radical Surface Initiation

Coating Nitinol (NiTi) surfaces with a polymer layer has become very appealing in the past few years owing to its increased attraction in the biomedical field. Although its intrinsic properties helped ensure its popularity, its extensive implementation is still hampered by its nickel inclusion, making it sensitive to pitting corrosion and therefore leading to the release of carcinogenic Ni²⁺ ions. Among all recent ways to modify NiTi surfaces, elaboration of self-assembled monolayers is of great interest as their high order confers a reinforcement of the metal surface corrosion resistance and brings new functionalities to the metal for postmodification processes. In this work, we compare the electroassisted and thermally assisted self-assembling of 11-(2-bromoisobutyrate)-undecyl-1-phosphonic acid (BUPA) to the classical immersion process on NiTi surfaces initially submitted to a hydrothermal treatment. Among all tested conditions, the electroassisted grafting of BUPA at room temperature appears to be the most promising alternative, as it allows grafting in very short times (5–10 min), thus preventing its degradation. The thus-formed layer has been proven to be sufficient to enable the surface-initiated atom transfer radical polymerization (SI-ATRP) of 2-(dimethylamino)­ethyl methacrylate

Biodegradable and High-Performance Poly(butylene adipate-<i>co</i>-terephthalate)–Lignin UV-Blocking Films

Renewable and biodegradable UV-blocking films are in high demand for the increasing need of sustainable environment. Lignin can offer significant UV absorption, but it deteriorates the mechanical properties of films at a high content. In this effort, biobased 10-undecenoic and oleic acids were successfully grafted on soda lignin via solvent- and catalyst-free processes, as confirmed by ³¹P and ¹H NMR and Fourier transform infrared (FTIR). The resulting lignin ester derivatives and neat lignin were then melt-blended with a biodegradable poly­(butylene adipate-<i>co</i>-terephthalate) (PBAT) to prepare UV-protective films. The incorporation of the modified lignins into the PBAT matrix exhibited good dispersion of lignin particles with almost unaffected tensile properties as well as good thermal stability for up to 20 wt % loading of lignin derivatives. The resulting films showed excellent UV-barrier property with 10 wt % lignin loading, having full protection in the whole UV-irradiation range (280–400 nm). The UV protection of prepared films proved persistent even after UV irradiation for 50 h, and their transparency was evidently enhanced. This work demonstrates a very promising procedure to produce high-performance and biodegradable PBAT–lignin UV-blocking films

Stable isotope ratios of Antarctic echinoids from the PS81 - ANTXXIX/3 Polarstern expedition

<p>This dataset contains carbon and nitrogen stable isotope composition of 120 Antarctic sea urchins belonging to 10 taxa (Abatus cavernosus, Amphipneustes rostratus, Amphipneustes similis, Aporocidaris eltaniana, Brachyternaster chesheri, Ctenocidaris gigantea, Notocidaris gaussiensis, Notocidaris mortenseni, Sterechinus antarcticus and Sterechinus neumayeri) and sampled in Drake Passage, Bransfield Strait and Weddell Sea during the ANTXXIX/3 (PS81) cruise of RV Polarstern in 2013. </p> <p>This data supports the article "Trophic Plasticity of Antarctic echinoids under contrasted environmental conditions" by L.N. Michel, B. David, P. Dubois, G. Lepoint & C. De Ridder, published in Polar Biology (doi: 10.1007/s00300-015-1873-y).</p> <p>Please refer to the article or contact Loïc Michel (loicmichel[at]gmail.com) for details.</p

Designing Multiple-Shape Memory Polymers with Miscible Polymer Blends: Evidence and Origins of a Triple-Shape Memory Effect for Miscible PLLA/PMMA Blends

Shape memory properties of polymers represent one of the most expanding fields in polymer science related to numerous smart applications. Recently, multiple-shape memory polymers (multiple-SMPs) have attracted significant attention and can be achieved with complex polymer architectures. Here, miscible PLLA/PMMA blends with broad glass transitions are investigated as an alternative platform to design multiple-SMPs. Dual-shape memory experiments were first conducted at different stretching temperatures to identify the so-called “temperature memory effect”. The switch temperature of the symmetric 50% PLLA/50% PMMA blend smoothly shifted from 70 to 90 °C for stretching temperatures increasing from 65 to 94 °C, attesting for a significant “temperature memory effect”. Asymmetric formulations with 30% and 80% PMMA also present a “temperature memory effect”, but the symmetric blend clearly appeared as the most efficient formulation for multiple-shape memory applications. A programming step designed with two successive stretchings within the broad glass transition consequently afforded high triple-shape memory performances with tunable intermediate shapes, demonstrating that the symmetric blend could represent an interesting candidate for future developments. Advanced shape recovery processes are consistent with a selective activation of specific “soft domains” or nanodomains arising from the broad glass transition and the large distribution of relaxation time observed by DSC and dielectric spectroscopy. Polarized IR measurements pointed out that the composition of activated/oriented “soft domains” could vary with stretching temperature, giving rise to the “temperature-memory effect”. Consequently, from a polymer physics standpoint, nanoscale compositional heterogeneities within the symmetric blend could be suspected and discussed on the basis of available models for miscible blends and for multiple-SMPs

Macrocyclic P3HT Obtained by Intramolecular McMurry Coupling of Linear Bis-Aldehyde Polymer: A Direct Comparison with Linear Homologue

Different P3HT chain lengths have been synthesized, functionalized at both chain ends with aldehyde moieties and finally cyclized following the McMurry reaction in a pseudo high dilution process. The confirmation of the high yielded intramolecular coupling came from the decrease of the hydrodynamic radius observed by SEC, correlated to the conservation of the mass distribution by MALDI-ToF and by the very low content of residual linear precursor estimated by NMR. Different aggregation behaviors between linear and cyclic and between short and long systems have been pointed out by DSC and UV–vis absorption spectroscopy. We estimate that long cyclic structures present similar aggregation behavior than long linear ones mainly due to the folding of those chains

Engineered polylactide (PLA)–polyamide (PA) blends for durable applications: 1. PLA with high crystallization ability to tune up the properties of PLA/PA12 blends

Polylactide (PLA), a biodegradable polyester produced from renewable resources, has a key position in the very promising market for bioplastics. Unfortunately, for utilization in durable/engineering applications, PLA suffers from some shortcomings such as low rate of crystallization, brittleness, and small ductility. The study proposes the use of PLA having high crystallization ability to tune up the properties of partly bio-based PLA/polyamide 12 (PA12) blends in presence of key additives. First, phenylphosphonic acid zinc salt (PPA-Zn) was selected as one of the most adapted nucleating agents (NAs) for PLA, whereas larger quantities of PLA(NA) have been produced for blending with PA12. The characterizations of PLA(NA) confirm dramatic improvements of PLA crystallization kinetics and an impressive degree of crystallinity (>40%). Blends having different PLA(NA)/PA12 ratios were prepared by melt-mixing with a laboratory micro-­compounder and characterized in terms of morphology, thermal stability, and with focus on the evidence of advanced crystallization properties. All differential scanning calorimetry measurements of PLA(NA)/PA12 blends suggest powerful nucleation and crystallization ability. Furthermore, addition of epoxy-functional styrene-acrylic compatibilizers into selected compositions by reactive extrusion (REX) was found to significantly change their morphology, preserving the properties of crystallization of PLA, with enhancements of mechanical properties (strength, ductility, impact resistance) confirmed by current prospects.</p

Copper-Catalyzed Dehydrogenative Polycondensation of a Bis-Aniline Hexylthiophene-Based Monomer: A Kinetically Controlled Air-Tolerant Process

Copper-Catalyzed Dehydrogenative Polycondensation of a Bis-Aniline Hexylthiophene-Based Monomer: A Kinetically Controlled Air-Tolerant Proces

Stereocomplexation of Polylactide Enhanced by Poly(methyl methacrylate): Improved Processability and Thermomechanical Properties of Stereocomplexable Polylactide-Based Materials

Stereocomplexable polylactides (PLAs) with improved processability and thermomechanical properties have been prepared by one-step melt blending of high-molecular-weight poly­(l-lactide) (PLLA), poly­(d-lactide) (PDLA), and poly­(methyl methacrylate) (PMMA). Crystallization of PLA stereocomplexes occurred during cooling from the melt, and, surprisingly, PMMA enhanced the amount of stereocomplex formation, especially with the addition of 30–40 % PMMA. The prepared ternary blends were found to be miscible, and such miscibility is likely a key factor to the role of PMMA in enhancing stereocomplexation. In addition, the incorporation of PMMA during compounding substantially raised the melt viscosity at 230 °C. Therefore, to some extent, the use of PMMA could also overcome processing difficulties associated with low viscosities of stereocomplexable PLA-based materials. Semicrystalline miscible blends with good transparency were recovered after injection molding, and in a first approach, the thermomechanical properties could be tuned by the PMMA content. Superior storage modulus and thermal resistance to deformation were thereby found for semicrystalline ternary blends compared to binary PLLA/PMMA blends. The amount of PLA stereocomplexes could be significantly increased with an additional thermal treatment, without compromising transparency. This could result in a remarkable thermal resistance to deformation at much higher temperatures than with conventional PLA. Consequently, stereocomplex crystallization into miscible PLLA/PDLA/PMMA blends represents a relevant approach to developing transparent, heat-resistant, and partly biobased polymers using conventional injection-molding processes

Toward “Green” Hybrid Materials: Core–Shell Particles with Enhanced Impact Energy Absorbing Ability

Restrained properties of “green” degradable products drive the creation of materials with innovative structures and retained eco-attributes. Herein, we introduce the creation of impact modifiers in the form of core–shell (CS) particles toward the creation of “green” composite materials. Particles with CS structure constituted of PLA stereocomplex (PLASC) and a rubbery phase of poly­(ε-caprolactone-<i>co</i>-d,l-lactide) (P­[CL-<i>co</i>-LA]) were successfully achieved by spray droplet atomization. A synergistic association of the soft P­[CL-<i>co</i>-LA] and hard PLASC domains in the core–shell structure induced unique thermo-mechanical effects on the PLA-based composites. The core–shell particles enhanced the crystallization of PLA matrices by acting as nucleating agents. The core–shell particles functioned efficiently as impact modifiers with minimal effect on the composites stiffness and strength. These findings provide a new platform for scalable design of polymeric-based structures to be used in the creation of advanced degradable materials