Reversible imine crosslinking in waterborne self-healing polymer coatings

Waterborne polymer coatings have the potential to address the environmental concerns associated with solvent based systems. To improve their performance without using volatile organic compounds, we propose a new approach based on reconfigurable covalent crosslinking that provides mechanical resistance and self-healing properties. The new waterborne polymer coatings are based on mixtures of aldehyde- and amine-functionalized polymer nanoparticles (PNPs) that take advantage of the reversibility of imine bonds in the presence of water. Different degrees of functional monomer incorporation (10 % to 40 %) allowed us to balance crosslinking and interdiffusion during film formation, to obtain mechanically robust and solvent resistant films. A clear structure-properties relation was assessed by following the formation of water resulting from amine-aldehyde condensation crosslinking, measured by differential scanning calorimetry. The resulting polymer coatings further show self-healing properties at room temperature, triggered with residual amounts of water and featuring high recovery rates of the mechanical properties. Our mechanically robust waterborne polymer coatings based in imine reversible crosslinking, featuring self-healing in mild conditions, offer excellent prospects for application in smart coating materials.publishe

Multifunctional platform based on electroactive polymers and silica nanoparticles for tissue engineering applications

Poly(vinylidene fluoride) nanocomposites processed with different morphologies, such as porous and non-porous films and fibres, have been prepared with silica nanoparticles (SiNPs) of varying diameter (17, 100, 160 and 300 nm), which in turn have encapsulated perylenediimide (PDI), a fluorescent molecule. The structural, morphological, optical, thermal, and mechanical properties of the nanocomposites, with SiNP filler concentration up to 16 wt %, were evaluated. Furthermore, cytotoxicity and cell proliferation studies were performed. All SiNPs are negatively charged independently of the pH and more stable from pH 5 upwards. The introduction of SiNPs within the polymer matrix increases the contact angle independently of the nanoparticle diameter. Moreover, the smallest ones (17 nm) also improve the PVDF Youngs modulus. The filler diameter, physico-chemical, thermal and mechanical properties of the polymer matrix were not significantly affected. Finally, the SiNPs inclusion does not induce cytotoxicity in murine myoblasts (C2C12) after 72 h of contact and proliferation studies reveal that the prepared composites represent a suitable platform for tissue engineering applications, as they allow us to combine the biocompatibility and piezoelectricity of the polymer with the possible functionalization and drug encapsulation and release of the SiNP.This work was supported by the Portuguese Foundation for Science and Technology (FCT) in the framework of the Strategic Funding UID/FIS/04650/2013 and UID/BIA/04050/2013 (POCI-01-0145-FEDER-007569) and project POCI-01-0145-FEDER-028237 funded by national funds through Fundação para a Ciência e a Tecnologia (FCT) and by the ERDF through the COMPETE2020-Programa Operacional Competitividade e Internacionalização (POCI); and also under the scope of the strategic funding of UID/BIO/04469 unit and COMPETE 2020 (POCI-01-0145-FEDER-006684) and BioTecNorte operation (NORTE-01-0145-FEDER-000004) funded by the European Regional Development Fund under the scope of Norte2020-Programa Operacional Regional do Norte. The authors also thank the FCT for the SFRH/BD/111478/2015 (S.R.), SFRH/BPD/96707/2013 (T.R.), SFRH/BPD/90870/2012 (C.R.) and SFRH/BPD/121526/2016 (D.C) grants. The authors acknowledge funding from the Spanish Ministry of Economy and Competitiveness (MINECO) through the project MAT2016-76039-C4-3-R (AEI/FEDER, UE) and from the Basque Government Industry and Education Departments under the ELKARTEK, HAZITEK and PIBA (PIBA-2018-06) programs, respectively.info:eu-repo/semantics/publishedVersio

Oxygen-proof fluorescence temperature sensing with pristine C 70 encapsulated in polymer nanoparticles †

We report the first successful encapsulation of pristine fullerene C 70 in polymer nanoparticles with very low size polydispersity. We obtained water-dispersed polystyrene (PS) nanoparticles with diameters from 60 nm to 190 nm using a miniemulsion polymerization technique. Contrarily to pristine fullerenes, which are insoluble in most solvents and materials, the nanoparticles containing fullerene C 70 (PS-C 70 ) are stable in water and can be easily incorporated in different materials. When blended with polyacrylonitrile (PAN), a virtually oxygen-impermeable polymer, the PS-C 70 nanoparticles show a strong temperature dependence of the thermally activated delayed fluorescence (TADF) intensity and lifetimes, even when exposed to air. This is the first fluorescence temperature sensor based on TADF that can operate in the presence of oxygen. Unlike other fluorescence temperature sensors, our sensor material is insensitive to oxygen, has emission lifetimes in the millisecond range, and shows a strong emission intensity increase when the temperature increases. This sensor exhibits a very broad sensitivity in a working range from À75 C to at least 105 C (based on fluorescence intensity), surpassing the performance of other temperature fluorescence sensors at high temperatures

Temperature-responsive copolymers without compositional drift by RAFT copolymerization of 2-(acryloyloxy)ethyl trimethylammonium chloride and 2-(diethylamino)ethyl acrylate

International audienceWe prepared novel temperature and pH responsive copolymers of [2-(acryloyloxy)ethyl] trimethylammonium chloride (AEtMACl) and 2-(diethylamino)ethyl acrylate (DEAEA) by RAFT polymerization. Such copolymers show a volume phase transition temperature that explains the excellent performance of hydrogels of the same monomers, selected among 600 different monomer combinations, to release cultured stem cells using only a mild temperature stimulus (R. Zhang, H. K. Mjoseng, M. A. Hoeve, N. G. Bauer, S. Pells, R. Besseling, S. Velugotla, G. Tourniaire, R. E. B. Kishen, Y. Tsenkin, C. Armit, C. R. E. Duffy, M. Helfen, F. Edenhofer, P. A. Sousa and M. Bradley, Nat. Commun., 2013, 1–10). We carried out a thorough investigation of the (co)polymerization kinetics of AEtMACl and protonated DEAEA in ethanol, and proposed convenient and reliable methods to follow the conversion of these two monomers by 1H NMR. Interestingly, for a very large range of feed compositions, the cumulative copolymer composition versus global conversion plots indicated that there was almost no compositional drift, corresponding to apparent reactivity ratios of about 1. Therefore, the copolymer has the same composition as the comonomer feed, regardless of both conversion and initial molar ratio. This rare situation enables the preparation of a variety of copolymer chains with highly homogeneous composition and microstructure, offering excellent prospects for the use of these materials as triggers in controlled release applications