Nanostructured morphology of a random P(DLLA-co-CL) copolymer

The random architecture of a commercial copolymer of poly(DL-lactic acid) and poly(ε-caprolactone), poly(DL-lactide-co-caprolactone), has been characterized by chemical structure analysis from hydrogen-1 nuclear magnetic resonance results. Moreover, spherical nanodomains have been detected in the thin films of this copolymer obtained after solvent evaporation. These nanodomains studied by atomic force microscopy and transmission elecron microscopy grow progressively under annealing until they collapse and form a homogenous disordered structure. This is the first time that the nanostructure of random poly(DL-lactic acid)/poly-(ε-caprolactone) copolymers is revealed, representing one of few experimental evidences on the possible nanostructuration of random copolymers

Electrospinning of biodegradable polylactide/hydroxyapatite nanofibers: Study on the morphology, crystallinity structure and thermal stability

[EN] Aligned mats of poly(lactic acid) (PLA) nanofibers containing nanosized hydroxyapatite filler have been obtained via electrospinning onto a rotating mandrel. Their structure and morphology have been characterized as a function of the production parameters, by SEM, DSC, DMA and WAXS, with emphasis in the effects of the take-up velocity. SEM, DSC and X-ray diffraction studies confirmed a reduction in fiber diameter, an increase of fiber orientation and a highly crystalline structure of the mats collected at higher speed due to the stretching produced during the process. Double melting behavior was observed, suggesting the presence of two crystalline forms. Moreover the higher storage modulus (E¿ modulus), and glass transition temperatures of the higher speed collected mats were correlated with an enhancement in the thermal stability and nanofiller distribution. © 2012 Elsevier Ltd. All rights reserved.This project has been supported by Project MAT2010/21494-C03 of Spanish Ministry for Science and Innovation (MICINN). AS acknowledges the support of FPU grant from MED (MED-FPU; AP2009-2482).Sonseca Olalla, A.; Peponi, L.; Sahuquillo, O.; Kenny, J.; Giménez Torres, E. (2012). Electrospinning of biodegradable polylactide/hydroxyapatite nanofibers: Study on the morphology, crystallinity structure and thermal stability. Polymer Degradation and Stability. 97(10):2052-2059. https://doi.org/10.1016/j.polymdegradstab.2012.05.009S20522059971

Thermally-activated shape memory effect on biodegradable nanocomposites based on PLA/PCL blend reinforced with hydroxyapatite

[EN] In this work, the effect of the addition of different amount of nanosized hydroxyapatite (nHA) on the shape memory behavior of blends based on poly (lactic acid) (PLA) and poly (epsilon-caprolactone) (PCL) has been studied. In particular PLA/PCL blend with 70 wt % PLA has been reinforced with 0.5, 1 and 3 wt % nHA. Moreover, the relationship between the morphology and the final properties of the nanocomposites has been investigated by field emission scanning electron microscopy, confocal Raman spectroscopy and atomic force microscopy. In particular, PeakForce has been used to study quantitative nanomechanical properties of the multifunctional materials leading to conclusion that nHA increase the phase separation between PLA and PCL as well as act as reinforcements for the PCL-rich phase of the nanocomposites. Furthermore, excellent thermally-activated shape memory response has been obtained for all the nanocomposites at 55 degrees C. Finally, the disintegration under composting conditions at laboratory scale level was studied in order to confirm the biodegradable character of these nanocomposites. Indeed, these materials are able to be used for biomedical issues as well as for packaging applications where both thermally-activated shape memory effect and biodegradability are requested.Authors thank the Spanish Ministry of Economy, Industry and Competitiveness, MINEICO, (MAT2017-88123-P) and the Regional Government of Madrid (S2013/MIT-2862) for the economic support. M.P.A. and L.P. acknowledge the Juan de la Cierva (FJCI-2014-20630) and Ramon y Cajal (RYC-2014-15595) contracts from the MINEICO, respectively. The authors also thanks CSIC for the I-Link project (I-Link1149).Peponi, L.; Sessini, V.; Arrieta, MP.; Navarro-Baena, I.; Sonseca Olalla, Á.; Dominici, F.; Giménez Torres, E.... (2018). Thermally-activated shape memory effect on biodegradable nanocomposites based on PLA/PCL blend reinforced with hydroxyapatite. Polymer Degradation and Stability. 151:36-51. https://doi.org/10.1016/j.polymdegradstab.2018.02.019S365115

Morphology-properties relationship on nanocomposite films based on poly(styrene-block-diene-block-styrene) copolymers and silver nanoparticles

A comparative study on the self-assembled nanostructured morphology and the rheological and mechanical prop- erties of four different triblock copolymers, based on poly(styrene-block-butadiene-block-styrene) and poly(styrene-block- isoprene-block-styrene) matrices, and of their respective nanocomposites with 1 wt% silver nanoparticles, is reported in this work. In order to obtain well-dispersed nanoparticles in the block copolymer matrix, dodecanethiol was used as surfac- tant, showing good affinity with both nanoparticles and the polystyrene phase of the matrices as predicted by the solubility parameters calculated based on Hoftyzer and Van Krevelen theory. The block copolymer with the highest PS content shows the highest tensile modulus and tensile strength, but also the smallest elongation at break. When silver nanoparticles treated with surfactant were added to the block copolymer matrices, each system studied shows higher mechanical properties due to the good dispersion and the good interface of Ag nanoparticles in the matrices. Furthermore, it has been shown that semi- empirical models such as Guth and Gold equation and Halpin-Tsai model can be used to predict the tensile modulus of the analyzed nanocomposites

Supramolecular Polycaprolactone-Based Polyurethanes with Thermally Activated Shape-Memory Behavior

In this work, using supramolecular polyurethanes theories, two polycaprolactone-based polyurethanes with 2-ureido-4-[1H]-pyrimidinone (UPy) motifs capable of forming quadruple hydrogen bonds were synthetized and characterized, focusing our attention on their capability to show thermally activated shape-memory response. In particular, H-1 NMR analyses confirmed the chemical structure of the supramolecular polyurethanes, while DSC showed their totally amorphous morphology. DMTA in tensile mode was used to study their thermally activated shape-memory properties. In our case, the UPy units are the switching domains while the network formed by the segregated hard segments is the permanent domain obtained materials with excellent shape-memory response at both 100 and 85 degrees C. These materials are promising for multi-responsive materials where bio-based and potentially recyclable polymers with excellent shape-memory properties are needed

Mechanical and Shape-Memory Properties of Poly(mannitol sebacate)/Cellulose Nanocrystal Nanocomposites

"This is the peer reviewed version of the following article: Sonseca, Á., Camarero‐Espinosa, S., Peponi, L., Weder, C., Foster, E. J., Kenny, J. M., & Giménez, E. (2014). Mechanical and shape‐memory properties of poly (mannitol sebacate)/cellulose nanocrystal nanocomposites. Journal of Polymer Science Part A: Polymer Chemistry, 52(21), 3123-3133., which has been published in final form at https://doi.org/10.1002/pola.27367. This article may be used for non-commercial purposes in accordance with Wiley Terms and Conditions for Self-Archiving."[EN] Polyesters based on polyols and sebacic acid, known as poly(polyol sebacate)s (PPS), are attracting considerable attention, as their properties are potentially useful in the context of soft-tissue engineering applications. To overcome the drawback that PPSs generally display rather low strength and stiffness, we have pursued the preparation of nano composites based poly(mannitol sebacate) (PMS), a prominent example of this materials family, with cellulose nanocrystals (CNCs). Nanocomposites were achieved in a two-step process. A soluble, low-molecular-weight PMS pre-polymer was formed via the polycondensation reaction between sebacic acid and D-mannitol. Nanocomposites with different CNC content were prepared by solution-casting and curing under vacuum using two different profiles designed to prepare materials with low and high degree of crosslinking. The as-prepared nano composites have higher stiffness and toughness than the neat PMS matrix while maintaining a high elongation at break. A highly crosslinked nanocomposite with a CNC content of 5 wt % displays a sixfold increase in Young s modulus and a fivefold improvement in toughness. Nanocomposites also exhibit a shape memory effect with a switch temperature in the range of 15 to 45 C; in particular the materials with a thermal transition in the upper part of this range are potentially useful for biomedical applicationsThe authors gratefully acknowledge financial support received from Spanish Ministry of Economy and Competitiveness (Project MAT2010/21494-C03), as well as the support of FPU grant from MED (MED-FPU; AP2009-2482), JAE-Doc grant (CSIC co-financed by FSE), Swiss National Science foundation (National Research Programme 64, Project #406440_131264/1) and the Adolphe Merkle Foundation.Sonseca, A.; Camarero-Espinosa, S.; Peponi, L.; Weder, C.; Foster, E.; Kenny, JM.; Giménez Torres, E. (2014). Mechanical and Shape-Memory Properties of Poly(mannitol sebacate)/Cellulose Nanocrystal Nanocomposites. Journal of Polymer Science Part A Polymer Chemistry. 52(21):3123-3133. https://doi.org/10.1002/pola.27367S312331335221Bruggeman, J. 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Fabrication and assessment of bifunctional electrospun poly(L-lactic acid) scaffolds with bioglass and zinc oxide nanoparticles for bone tissue engineering

Electrospun scaffolds based on poly(L-lactic acid) (PLLA) with bioglass (n-BG) and zinc oxide (n-ZnO), and mixture of both, were developed to design bifunctional biomaterials with enhanced bioactive and biocidal properties. The presence of n-BG increased the fiber diameter of the pure PLA from 1.5 ± 0.3 μm to 3.0 ± 0.8 μm for 20 wt%. ZnO and the mixed nanoparticles did not significantly affect the morphology. The mechanical properties decreased with the presence of nanoparticles. Scaffolds based on PLA/n-BG promoted hydroxyapatite (HA) formation in simulated body fluid (SBF) that was inhibited with the presence of ZnO. Notably, mixed particles produced bioactivity although at longer times. The incorporation of n-ZnO produced a biocidal capacity against S. aureus in the polymeric scaffold, reaching a viability reduction of 60 % after 6 h of exposure. When both types of nanoparticles were combined, the bacterial viability reduction was 30 %. Pure PLA scaffolds and the composites with n-BG showed good ST-2 bone marrow-derived cell line viability, scaffolds with n-BG (pure or mixture) presented lower viability. Results validated the use of both n-BG and n-ZnO fillers for the development of novel bifunctional PLA-based scaffolds with both bioactive and biocidal properties for bone tissue engineering applications.P.A. Zapata acknowledge the financial support of Direccion de Investigacion Científica y Tecnologica, Universidad de Santiago de Chile (DICYT) project: 052241ZR_DAS. D. Canales thanks the financial support of FONDECYT under postdoctoral project No. 3210810. Finally, D. Canales is immensely grateful to Katharina Schuhladen, Sonja Kuth, Lena Vogt, Irem Unalam, and Florian Ruther, members of Institute of Biomaterials of University of Erlangen-Nuremberg, for their support in the mechanical and biological analysis

In Vitro Degradation of Plasticized PLA Electrospun Fiber Mats: Morphological, Thermal and Crystalline Evolution

In the present work, fiber mats of poly(lactic acid), PLA, plasticized by different amounts of oligomer lactic acid, OLA, were obtained by electrospinning in order to investigate their long term hydrolytic degradation. This was performed in a simulated body fluid for up to 352 days, until the complete degradation of the samples is reached. The evolution of the plasticized electrospun mats was followed in terms of morphological, thermal, chemical and crystalline changes. Mass variation and water uptake of PLA-based electrospun mats, together with pH stability of the immersion media, were also studied during the in vitro test. The results showed that the addition of OLA increases the hydrolytic degradation rate of PLA electrospun fiber mats. Moreover, by adding different amounts of OLA, the time of degradation of the electrospun fiber mats can be modulated over the course of a year. Effectively, by increasing the amount of OLA, the diameter of the electrospun fibers decreases more rapidly during degradation. On the other hand, the degree of crystallinity and the dimension of the α crystals of the electrospun fiber mats are highly affected not only by the presence but also by the amount of OLA during the whole process.PCIN-2017-036: MAT2017-88123-P; PID2019-104351GB-C21.Peer reviewe

Polyurethane based on PLA and PCL incorporated with catechin: Structural, thermal and mechanical characterization

Catechin (Cat) was added into polyurethane (PU) based on a tri-block copolymer of poly(L-lactic acid) and poly(ε-caprolactone) (PLLA-b-PCL-b-PLLA) to improve the thermal stability of the final PU composite materials. The morphological, structural, mechanical and thermal properties of PU-Cat composites loaded with 1 wt%, 3 wt% and 5 wt% of Cat were investigated and designed as PU-Cat1, PU-Cat3 and PU-Cat5, respectively. Homogeneous films were obtained after the solvent casting process, but the higher amount of 5 wt% used in this work could not be successfully dispersed and produced some structural defects as were observed by scanning electron microscopy. Well dispersed Cat in PU-Cat1 and PU-Cat3 not only substantially improved the thermal stability due to the Cat antioxidant effect, but also allowed the crystallization of PCL and PLLA blocks in the final PU-Cat composites. Additionally, PU-Cat composite materials showed excellent stretchability for film production.Authors thank Spanish Ministry of Economy and Competitiveness, MINECO, (MAT2013-48059-C2-1-R and MAT2014-55778- REDT) and Regional Government of Madrid (S2013/MIT-2862) for the financial support. M.P.A. and L.P. acknowledge the Juan de la Cierva (FJCI-2014-20630) and Ramon y Cajal (RYC-2014-15595) contracts from the MINECO, respectivelyPeer Reviewe