Mechano-morphological studies of polyamide 6 based single polymer laminate composites prepared by different reactive processing techniques

Single polymer laminate composites based on polyamide 6 (PA6) were prepared by two methods: (i) reactive injection molding and (ii) powder coating/compression molding, both carried out in the presence of PA6 woven textile plies. The effect of the textile volume fraction Vf on the tensile properties of all composites was investigated. The laminates obtained by powder coating/compression molding displayed best mechanical performance, whereby in the composites with Vf = 15%, the improvement of the elastic modulus reached 98% in respect to commercial hydrolytic PA6 reference, or 50–86% as compared to neat anionic PA6 samples. Polarizing light microscopy with image processing was used for morphological characterization. A transcrystalline layer at the fiber-matrix interface was detected in all laminates with thicknesses between 0.5 and 3.0 μm, depending on the preparation technique applied. The thermal stability was studied in the temperature range of 30°C-550 °C. The laminates obtained by reactive injection molding displayed the lowest initial decomposition temperature due to the presence of oligomers. Selected laminate composites were reprocessed by grinding and injection molding. The recycled composites obtained by powder coating displayed a 38% increase of the elastic modulus in respect to commercial hydrolytic PA6 thus confirming the sustainability and recyclability of PA6-based single polymer composites.This work was partially financed by FEDER funds through the COMPETE program and by national funds through FCT – Foundation for Science and Technology within the project .POCI-01-0145-FEDER 007136 SDT thanks FCT for his PhD Grant SFRH/BD/94759/2013. ZZD and NVD thank the National Funds through FCT-Portuguese Foundation for Science and Technology, project reference UID/CTM/50025/2019. All authors gratefully acknowledge the support of the project TSSiPRO NORTE-01-0145-FEDER-000015 funded by the regional operational program NORTE 2020, under the PORTUGAL 2020 Partnership Agreement, through the European Regional Development Fund

Bovine serum albumin-imprinted magnetic poly(2-pyrrolidone) microparticles for protein recognition

This study reports on the synthesis and adsorption properties of molecularly imprinted porous magnetic microparticles (MIP) based on the biodegradable and sustainable poly(2-pyrrolidone) (PPD or PA4). These new PPD MIP materials were obtained via activated anionic ring-opening polymerization of 2-pyrroldone carried out at 40 °C, in the presence of iron fillers and bovine serum albumin (BSA) as a template. Neither solvent, nor additional crosslinking or porogen agents were used in the PPD MIP synthesis. Analogously, PPD particles without BSA imprinting (NIP) were also produced. Depending on the microparticles composition, their yields were in the 55–70 wt% range, the average size varying between 8 and 25 μm. After characterization of the surface topography of all samples, their adsorption capacity toward the BSA target was assessed as a function of the adsorption time, protein concentration and pH of the medium. All three PPD MIP samples displayed adsorption capacity toward BSA being up to one order of magnitude higher as compared to other BSA-imprinted polymer systems. It was found that the rebinding of BSA on MIP is best described by the Langmuir isotherm, whereas for rebinding on NIP the Freundlich isotherm was the more adequate model. On this basis, the nature of the adsorption on MIP and NIP was discussed. The adsorption toward two other proteins, namely Ovalbumin and Cytochrome C was also tested. The newly synthesized BSA-imprinted PPD MIP displayed selective adsorption for the BSA target being dependent on the pH values of the medium. The easy recovery of the Fe-containing MIP and the capacity of all MIP samples for multiple sorption/desorption cycles was demonstrated.The authors gratefully acknowledge the financial support of the project TSSiPRO NORTE-01-0145-FEDER-000015, supported by the regional operation program NORTE2020, under the Portugal 2020 Partnership Agreement, through the European Regional Development Fund, as well as the support by National Funds through Fundação para a Ciência e Tecnologia (FCT), project UID/CTM/50025/2019. N. Dencheva is also grateful for the financial support of FCT in the frames of the strategic project UID/CTM/50025/2013 and the personal pro gram-contract CTTI-51/18-IP

Synthesis of Novel Polymer-Assisted Organic-Inorganic Hybrid Nanoflowers and Their Application in Cascade Biocatalysis

This study reports on the synthesis of novel bienzyme polymer-assisted nanoflower complexes (PANF), their morphological and structural characterization, and their effectiveness as cascade biocatalysts. First, highly porous polyamide 6 microparticles (PA6 MP) are synthesized by activated anionic polymerization in solution. Second, the PA6 MP are used as carriers for hybrid bienzyme assemblies comprising glucose oxidase (GOx) and horseradish peroxidase (HRP). Thus, four PANF complexes with different co-localization and compartmentalization of the two enzymes are prepared. In samples NF GH/PA and NF GH@PA, both enzymes are localized within the same hybrid flowerlike organic-inorganic nanostructures (NF), the difference being in the way the PA6 MP are assembled with NF. In samples NF G/PAiH and NF G@PAiH, only GOx is located in the NF, while HRP is preliminary immobilized on PA6 MP. The morphology and the structure of the four PANF complexes have been studied by microscopy, spectroscopy, and synchrotron X-ray techniques. The catalytic activity of the four PANF was assessed by a two-step cascade reaction of glucose oxidation. The PANF complexes are up to 2–3 times more active than the free GOx/HRP dyad. They also display enhanced kinetic parameters, superior thermal stability in the 40–60 °C range, optimum performance at pH 4–6, and excellent storage stability. All PANF complexes are active for up to 6 consecutive operational cycles

Preparation and properties of metal-containing polyamide hybrid composites via reactive microencapsulation

Polyamide 6 microcapsules (PAMC) loaded with 2-8 wt% of Cu, Zn or Fe and up to 30 wt% of Al particles are synthesized via activated anionic polymerization (AAP) of ε-caprolactam in suspension performed in the presence of the respective micro- or nanosized loads. The high-molecular weight porous PAMC are with typical diameters of 10-90 μm depending on the size of the metal filler particles. The latter are entrapped in the core of PAMC as proven by microscopy methods. The melt processing of the loaded microcapsules produced PA6/metal hybrid thermoplastic composites with homogeneous distribution of the loads without any functionalization. The crystalline structure of all PAMC and molded composites are studied by thermal and microfocus X-ray diffraction methods suggesting polymorph changes during the transition from PAMC to molded plates. Mechanical tests in tension showed that transforming Al-loaded PAMC into composites produces polyamide hybrids with higher modulus and strength at break. Measuring the conductivity and dielectric properties of the composites in linear and cyclic modes showed that 30 wt% of Al can change significantly the permittivity of the hybrid composites without increasing the conductivity of the PA6 matrix.The authors gratefully acknowledge the financial support of the Portuguese Foundation for Science and Technology (FCT) in the frames of the Strategic Project LA25/2013-2014, projects PTDC/EEI-SII/5582/2014 and PTDC/CTMENE/ 5387/2014 and post-doctoral grant SFRH/BPD/45252 co-financed by QREN-POPH program of the EU and of MiNaXS beamline of DESY – Hamburg, Germany. Financial support from the Basque Government Industry Department under the ELKARTEK Program is also acknowledged. SLM thanks the Diputación Foral de Bizkaia for financial support under the Bizkaia Talent program; European Union’s Seventh Framework Programme; Marie Curie Actions – People; Grant agreement nº 267230