Synthesis, physical properties and processing of multifunctional molecular materials

New multifunctional materials (MMMs) where conductivity and magnetism coexist or, in some cases, interact, have been prepared and fully characterized as quality crystals or thin films. [(BDH-TTP)6] [Fe(croc)3] ·CH2Cl2 (1), where paramagnetism is due to isolated Fe(III) metal ions with S = 5/2 ground state of the anionic [Fe(croc)3]3- complexes and conductivity originates from BDH-TTP organic donor in k-type packing, has been obtained. When applying a pressure higher than 7 kbar, (1) behaves as a metal down to low temperature (2 K). The isostructural [(BDH-TTP)6] [Ga(croc)3] ·CH2Cl2 (2) behaves as a metal down to ~ 100 K. [Mn(5-MeOsaltmen)(acetone)]2[Ni(dmit)2]6 (3), where single molecule magnet (SMM) behavior of the Mn(III) dimers coexists with the semiconducting behavior due to the d8 square planar complexes of [Ni(dmit)2]n- (n = 0 or 1), has been obtained. Deviations of the magnetic properties from that of isolated [Mn2]2+ SMMs based, have been found, may be due to interactions such as [Ni(dmit)2]n- ⋯ [Ni(dmit)2]n-, [Mn2]2+ ⋯ [Mn2]2+, [Ni(dmit)2]n- ⋯ [Mn2]2+, demonstrating the tunability of the SMM behavior by changing the combination of both SMMs and conducting building blocks. Processing of these materials has been performed by embedding different magnetic conducting carriers into polymer. the By poly(3,4 ethylenedioxythiophene) potentiostatic and (PEDOT), potentiodynamic electropolymerization, PEDOT films doped with magnetic polyoxometalate (POM) [Co4(H2O)2(PW9O34)2]10- have been obtained; the film obtained by using the potentiodynamic method is more stable than the analogous material obtained by applying a constant potential, when subjected to potential cycles in acetonitrile solutions of LiClO4 and TBAClO4. In situ chemically oxidized PEDOT thin films, doped with [FeIICrIII(ox)3]- anions, have been obtained. These materials show ferromagnetic coupling due to Fe(II)-Cr(III) ions and the presence of some disorder and a superparamagnetic behavior, while the conductivity depends of the EDOT : anion ratio. The PEDOT:PSS (PSS = polystyrenesulfonic acid) aqueous dispersion, has been used for coating negatively charged, Cs0.46Ni[Fe(CN)6]0.94, nanoparticles (NPs) and a high conducting thin film showing superparamagnetic properties due to the NPs has been obtained. Magnetoresistance measurements at low temperature reveal the existence of an interplay between the magnetic and conducting lattices

Bio-Based Polyether from Limonene Oxide Catalytic ROP as Green Polymeric Plasticizer for PLA

In this work, the polymerization of Limonene Oxide (LO) has been achieved using an Earth abundant metal-based catalyst developed in our group, that is very active in ring opening polymerization (ROP) processes. The bio-based polylimonene ether (PLO) obtained had low molecular weight and good thermal properties, thus being a potential green polymeric additive for other bio-based polymers such as PLA. Hence, we have explored its ability to influence PLA properties. The addition of only 10 wt %, led to the modification and improvement of PLA properties in terms of flexibility, thermal stability, and hydrophobicity. The results obtained are promising and open up the potential industrial application of polylimonene oxide (PLO) for the melt-processing of blends based on PLA/PLO. These new materials are totally based on renewable sources and may be interesting for many applications where biodegradability and reduced water adsorption is required, such as food packaging or agricultural mulch films

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

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

Insight into the melt processed Polylimonene oxide/Polylactic acid blends

In this work, the polymerization of limonene oxide (LO) has been optimized at room temperature with two different aluminium-based catalysts [AlMeX{2,6-(CHPh$_2$)$_2$-4-tBu-C$_6$H$_2$O}] (X = Me (1), Cl (2)). A fully bio-based ether, polylimonene oxide (PLO), has been synthesized with low molecular weight and good thermal stability, being a potential sustainable polymeric additive for other bio-based and biodegradable polymers such as polylactic acid (PLA). Hence, we have explored its ability to influence the thermal, mechanical and morphological properties of PLA by preparing their blends by melt processing. The addition of a low amount of PLO led to a nearly 10 $^\circ$C decrease in the PLA glass transition temperature. Moreover, a decrease in the PLA melting temperature and the degree of crystallinity was observed. Interestingly, a remarkable increase in the flexibility of PLA-based films was noticed. All the results point to the existence of strong interactions between the components, suggesting their partial miscibility.Comment: Polymer Chemistry (2023

Ring-Opening Polymerization of L-Lactide Catalyzed by Potassium-Based Complexes: Mechanistic Studies

Two non-toxic potassium compounds, 1 and 2, with a commercial oximate ligand have been prepared and fully spectroscopically characterized. Their activity as catalysts for the ring-opening polymerization (ROP) process of LLA has been studied, showing that they are extremely active and able to polymerize the monomer in a few minutes. For derivative 2, the presence of a crown ether in the potassium coordination sphere affects the nuclearity of the compound and consequently its solubility, with both aspects having an influence in the polymerization process. Detailed studies of the polymerization mechanism have been performed, and an unusual anionic mechanism was observed in absence of a co-initiator. Indeed, the monomer deprotonation generates a lactide enolate, which initiates the polymerization propagation. On the contrary, when a 1:1 ratio of cat:BnOH is used, a mixture of mechanisms is observed, the anionic mechanism and the activated monomer one, while from a cat:BnOH ratio of 1:2 and over, only the activated monomer mechanism is observed

Ring-Opening Polymerization of L-Lactide Catalyzed by Potassium-Based Complexes: Mechanistic Studies

Two non-toxic potassium compounds, 1 and 2, with a commercial oximate ligand have been prepared and fully spectroscopically characterized. Their activity as catalysts for the ring-opening polymerization (ROP) process of LLA has been studied, showing that they are extremely active and able to polymerize the monomer in a few minutes. For derivative 2, the presence of a crown ether in the potassium coordination sphere affects the nuclearity of the compound and consequently its solubility, with both aspects having an influence in the polymerization process. Detailed studies of the polymerization mechanism have been performed, and an unusual anionic mechanism was observed in absence of a co-initiator. Indeed, the monomer deprotonation generates a lactide enolate, which initiates the polymerization propagation. On the contrary, when a 1:1 ratio of cat:BnOH is used, a mixture of mechanisms is observed, the anionic mechanism and the activated monomer one, while from a cat:BnOH ratio of 1:2 and over, only the activated monomer mechanism is observed

Titanium-catalyzed synthesis of polymyrcene and polyanethol and application as sustainable additives for poly(lactic acid)

The replacement of fossil-derived plastics with those obtained from bio-based resources, which present suitable performance to be employed as commodity plastics is currently an important field of research, given the urgent need to transition from a fossil-based to a more sustainable economy. In this context, this work is focused on the application of a catalytic system based on silsesquioxane-cyclopentadienyl titanium complexes for the preparation of bio-based polymers, which can be used as additives to improve the poor material properties of a biodegradable polymer such as poly(lactic acid) (PLA). These titanium complexes, when activated with methylaluminoxane or with triflate salts, are shown to be capable of the polymerization of two bio-based monomers: myrcene and anethole. It is notable that polymerizations with these two distinct monomers take place through different mechanisms. The resulting polymyrcene (PMy) and polyanethol (PAN) have been applied as modifiers for PLA. Binary blends of PMy and PLA exhibited a considerable decrease in Tg and the promotion of PLA crystallization for a PMy content below 15 wt%. The mechanical properties of the PLA/PMy blends also displayed plasticization, with a decrease in the elastic modulus and enhanced plasticity, which resulted in less fragile systems compared to pure PLA. Morphological analysis has indicated a partially miscible, phase-separated system with micron-sized domains. In contrast, PAN completely inhibited PLA crystallization and the PLA/PAN blends were immiscible, but well-dispersed, a phase-separated system was obtained in solvent-casting film preparation with very small PAN domains. The blends showed higher tensile modulus than pure PLA and an absence of plastic behaviour, resulting in more fragile systems upon the addition of PAN to PLA

El limoneno: uno de los terpenos más usados y su papel en la industria de los bioplásticos

La mayoría de los materiales poliméricos usados diariamente se obtienen a partir de fuentes fósiles. Debido a los recursos limitados de petróleo y a los problemas generados por la contaminación de los plásticos, es necesario encontrar nuevas fuentes renovables para la obtención de materiales de uso cotidiano. Los bioplásticos obtenidos a partir de la biomasa constituyen la principal alternativa a los materiales poliméricos tradicionales obtenidos del petróleo. Dentro de la biomasa, el limoneno se revela como una plataforma química prometedora. Así pues, durante la última década el uso de limoneno se ha investigado con intensidad y actualmente se han evidenciado nuevos procesos catalíticos capaces de proporcionar excelentes productos químicos y polímeros a partir de él. En este artículo se analizarán las diferentes aplicaciones del limoneno en la industria de polímeros como precursor orgánico para la síntesis o el procesado de bioplásticos avanzados y multifuncionales