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Biodegradable blends based on plasticized poly(lactic acid) PLA and thermoplastic starch (TPS) have been obtained. The influence of the PLA plasticizer as a compatibility agent has been studied by using two different plasticizers such as neat oligomeric lactic acid (OLA) and functionalized with maleic acid (mOLA). In particular, the morphological, thermal, and mechanical properties have been studied as well as the shape memory ability of the melt-processed materials. Therefore, the influence of the interaction between different plasticizers and the PLA matrix as well as the compatibility between the two polymeric phases on the thermally-activated shape memory properties have been studied. It is very interesting to use the same additive able to act as both plasticizer and compatibilizer, decreasing the glass transition temperature of PLA to a temperature close to the physiological one, obtaining a material suitable for potential biomedical applications. In particular, we obtain that OLA-plasticized blend (oPLA/TPS) show very good thermally-activated capability at 45 °C and 50% deformation, while the blend obtained by using maleic OLA (moPLA/TPS) did not show shape memory behavior at 45 °C and 50% deformation. This fact is due to their morphological changes and the loss of two well-distinguished phases, one acting as fixed phase and the other one acting as switching phase to typically obtain shape memory response. Therefore, the thermally-activated shape memory results show that it is very important to make a balance between plasticizer and compatibilizer, considering the need of two well-established phases to obtain shape memory response. [ABSTRACT FROM AUTHOR]

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, 1H 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 °C. These materials are promising for multi-responsive materials where bio-based and potentially recyclable polymers with excellent shape-memory properties are needed. [ABSTRACT FROM AUTHOR]

Highlights • Hydrogen bonds between acetate groups and −OH groups of SNCs surface are formed. • Good dispersion of SNCs into the EVA matrix thanks to the physical interactions. • Hydrogen bond interactions lead to improved mechanical and thermal properties. Abstract Starch nanocrystals (SNCs) were successfully synthesized by acid hydrolysis of waxy barley starch and were characterized by X-ray diffraction, scanning and transmission electron microscopy. Nanocomposites based on ethylene-co-vinyl acetate (EVA) and SNCs were produced by melt-processing using a microextruder. Interesting is to note that SNCs do not lose their crystalline nature during melt-processing. Moreover, the mechanical and thermal properties of the neat matrix were improved by the addition of SNCs thanks to the strong hydrogen bonding between the nanofillers surface and the acetate groups of the matrix. The introduction of 2 wt.% and 5 wt.% of SNCs into the matrix, lead to an increase of its elastic modulus of about 50% and 100%, respectively. Moreover, the addition of SNCs provoked an increase of the thermal stability of about 10 °C respect to the neat matrix. These results clearly revealed the possibility to introduce SNCs in a polymeric matrix by extrusion enabling to reach materials with enhanced mechanical and thermal properties due to beneficial hydrogen bonding between SNCs and EVA. [ABSTRACT FROM AUTHOR]

Abstract In this work, the thermal degradation and the disintegrability under composting conditions of melt-processed blends based on ethylene-vinyl acetate and thermoplastic starch, EVA/TPS, as well as their nanocomposites, reinforced with natural bentonite, were studied. A special emphasis was first put on the influence of starch on the morphology, thermomechanical properties and hydrophilicity of these blends before composting analysis. In fact, the materials were characterized in terms of morphological, mechanical, thermal and structural properties as well as wettability performance, obtaining information about the immiscibility of the blends and their compatibilization when natural bentonite is used. The thermal stability of starch was increased according with the EVA content in the blend, while the compatibility between both polymeric phases was increased by adding the nanoclays. Consequently, the disintegration under composting condition at laboratory scale level of the obtained materials was conducted and the thermal and chemical-structural properties as well as the surface microstructural changes of recovered samples at different stages of disintegration were studied. Disintegration tests showed that EVA/TPS blends and their nanocomposites presented positive interactions, which delay the disintegration of TPS matrix in compost, thus improving TPS stability. Moreover, blending biodegradable polymers such as TPS with non-biodegradable polymers like EVA leads to the increase of compostable polymer percentage in partially-degradable materials giving a possible solution for the end-life of these materials after their use. Highlights • The thermal, chemical-structural as well as surface microstructural changes of disintegrated sample were studied. • Natural bentonite increase the EVA/TPS compatibility delaying the disintegration of TPS matrix in compost. • Melt-blending TPS with EVA increase the stability of starch-based materials. [ABSTRACT FROM AUTHOR]

In this work the thermally-activated shape memory response of biodegradable nanocomposites based on PLA/PCL blend reinforced with different type of cellulose nanocrystals has been reported, and compared with those of the neat matrix, at the same transition temperature of 55 °C and at the same different deformations, 50%, 100% and 150%. In particular, cellulose nanocrystals have been synthesized and then functionalized by “grafting from” reaction by ring opening polymerization of both PLLA and PCL using the OH groups onto the cellulose nanocrystals surface as initiators for the reaction. The morphology, thermal and mechanical analysis have been performed in order to obtain the parameters for the thermo-mechanical shape memory cycles. Moreover, the addition of the CNC-based nanofillers on the compatibility of PLA-PCL blends in 70:30 proportion has been evaluated. All the biodegradable nanocomposite formulations showed excellent shape memory response, similar to those of the neat matrix, with strain recovery ratio and strain fixity ratio higher than 80% and 90%, respectively. This fact indicates that in this case, the shape memory response of the nanocomposites is mainly controlled by the response of the neat blend and they are slightly influenced by the increase of compatibility between the components of the blend. In addition, all nanocomposite films were fully disintegrated under composting conditions confirming their biodegradable nature, obtaining that the presence of CNC-based nanofillers speeds up the disintegration rate of the nanocomposites in comparison with the pure matrix. [ABSTRACT FROM AUTHOR]

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 (ε-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 °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. [ABSTRACT FROM AUTHOR]

Humidity-activated shape memory behavior of plasticized starch-based films reinforced with the innovative combination of starch nanocrystals (SNCs) and catechin as antioxidant were studied. In a previous work, we reported the processing of gelatinized starch-based films filled with SNCs and catechin as antioxidant agent, and we observed that this novel combination leads to starch-based film with enhanced thermal and mechanical performance. In this work, the humidity-activated shape memory behavior of the previous developed starch-based films was characterized. The moisture loss as well as the moisture absorption were studied since they are essential parameters in humidity-activated shape memory polymers to fix the temporary shape and to recover the original shape, respectively. Therefore, the effect of the incorporation of SNCs and catechin on the humidity-activated shape memory properties of plasticized starch was also studied. Moreover, the effectiveness of catechin to increase the polymer stability under oxidative atmosphere and the thermo-mechanical relaxation of all the starch-based materials were studied. The combination of plasticized starch matrix loaded with both, SNCs and catechin, leads to a multifunctional starch-based films with increased hydrophilicity and with excellent humidity-activated shape memory behavior with interest for potential biomedical applications. [ABSTRACT FROM AUTHOR]

In this work, a systematic study on the humidity-activated shape memory properties of dual-responsive shape memory bionanocomposites with both humidity- and thermally-activated shape memory effects is reported. The study is performed through humidity-mechanical cycles in an Instron machine with a temperature chamber equipped with an ultrasonic humidity generator. In particular, the bionanocomposites studied are based on blends of ethylene-vinyl acetate (EVA) and thermoplastic starch reinforced with natural bentonite. In our previous work, thermomechanical cycles are performed by using EVA-induced crystallization and a preliminary humidity-activated shape memory test is designed. Herein, the shape memory results of both blends and their nanocomposites reflect the very good ability to humidity-activated recover of the initial shape with values higher than 80%. Moreover, the ability to fix the temporary shape of this systems is very good, especially when nanofillers are added. The compatibilizer effect of natural bentonite is demonstrated by means of different techniques such as scanning emission microscopy and mapping by confocal Raman spectroscopy. [ABSTRACT FROM AUTHOR]

Fully biobased edible films were prepared using native potato starch plasticized with glycerol and further reinforced with catechin (Cat) and starch nanocrystals (SNC) obtained by acidic hydrolysis from waxy maize starch granules. The thermal stability of starch nanocrystals obtained at different pH was studied, resulting on a decreasing in thermal stability at higher pH values. The X-ray diffraction patterns of the plasticized reinforced materials display complete destructuration of starch by solvent casting process. Plasticized films showed lower onset degradation temperatures than non-plasticized starch film. The reduction of the inter- and intra-molecular bonds interaction within the polymer matrix due to glycerol presence leads to a decrease of the thermal stability of the whole system. On the other hand, Cat and SNC produced an increase on the thermal stability of the bionanocomposites delaying the beginning of the thermal decomposition of starch/glycerol systems of about 20 °C. The mechanical performance was also improved in the ternary bionanocomposite edible films. All the edible films were fully disintegrated in compost conditions suggesting their possible applications as biodegradable edible films for packaging. [ABSTRACT FROM AUTHOR]

Blending commercial homopolymers represents a low cost and an easy scalable process to extend the use of the pristine homopolymers to an industrial level. Actually, the processing of blends by extrusion is the usual solution followed in the industry. However, commonly polymer blends are immiscible, provoking phase separation, which can be in the macro, micro or nano scale, depending on the polymers as well as on the processing conditions, affecting the final properties of the blends. Therefore, this paper aims to study the shape memory behavior in biodegradable blends based on poly(lactic acid) (PLA) and poly(ε-caprolactone) (PCL) in different concentrations. A completely thermal and mechanical characterization of the blends was performed, correlating the results with the observed morphology. In addition, two different biodegradation studies were performed in order to correlate the effect of each homopolymer with the degradation behavior of the biodegradable blends. [ABSTRACT FROM AUTHOR]

Within bioplastics, natural poly(3‐hydroxybutyrate) (PHB) stands out as fully biocompatible and biodegradable, even in marine environments; however, its high isotacticity and crystallinity limits its mechanical properties and hence its applications. PHB can also be synthesized with different tacticities via a catalytic ring‐opening polymerization (ROP) of rac‐β‐butyrolactone (BBL), paving the way to PHB with better thermomechanical and processability properties. In this work, the catalyst family is extended based on aluminum phenoxy‐imine methyl catalyst [AlMeL2], that reveals efficient in the ROP of BBL, to the halogeno analogous complex [AlClL2]. As well, the impact on the ROP mechanism of different initiators is further explored with a particular focus in dimethylaminopyridine (DMAP), a hardly studied initiator for the ROP of BBL. A thorough mechanistic study is performed that evidences the presence of two concomitant DMAP‐mediated mechanisms, that lead to either a DMAP or a crotonate end‐capping group. Besides, in order to increase the possibilities of PHB post‐polymerization functionalization, the introduction of a side‐chain functionality is explored, establishing the copolymerization of BBL with β‐allyloxymethylene propiolactone (BPLOAll), resulting in well‐defined P(BBL‐co‐BPLOAll) copolymers. [ABSTRACT FROM AUTHOR]

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 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. Image 1 • Polymerization of Limonene Oxide was achieved with an aluminium catalyst. • PLO is an efficient green additive for PLA able to modify its properties. • PLO increase the flexibility, the thermal stability and the surface hydrophobicity of PLA. • PLO is a promising industrial plasticizer totally derived from renewable sources. • PLA/PLO blends can be used for potential agricultural applications. [ABSTRACT FROM AUTHOR]

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 T g 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. [Display omitted] • Polymerization of bio-based monomers (myrcene and anethol) using titanium catalysts is presented. • The bio-based polymyrcene and polyanethol obtained, were used as modifiers for poly(lactic acid) (PLA). • It was found that polymyrcene acts as a plasticizer, reducing the fragility of pure PLA. • However, polyanethol completely inhibits PLA crystallization. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

Functional packaging represents a new frontier for research on food packaging materials. In this context, adding antioxidant properties to packaging films is of interest. In this study, poly(butylene adipate- co -terephthalate) (PBAT) and olive leaf extract (OLE) have been melt-compounded to obtain novel biomaterials suitable for applications which would benefit from the antioxidant activity. The effect of cellulose nanocrystals (CNC) on the PBAT/OLE system was investigated, considering the interface interactions between PBAT/OLE and OLE/CNC. The biomaterials' physical and antioxidant properties were characterized. Morphological analysis corroborates the full miscibility between OLE and PBAT and that OLE favours CNC dispersion into the polymer matrix. Tensile tests show a stable plasticizer effect of OLE for a month in line with good interface PBAT/OLE interactions. Simulant food tests indicate a delay of OLE release from the 20 wt% OLE-based materials. Antioxidant activity tests prove the antioxidant effect of OLE depending on the released polyphenols, prolonged in the system at 20 wt% of OLE. Fluorescence spectroscopy demonstrates the nature of the non-covalent PBAT/OLE interphase interactions in π-π stacking bonds. The presence of CNC in the biomaterials leads to strong hydrogen bonding interactions between CNC and OLE, accelerating OLE released from the PBAT matrix. [ABSTRACT FROM AUTHOR]

Smart and functional properties of coumarin and PCL-based polyurethane (PU) nanocomposites reinforced with both pristine silica nanoparticles and silica nanoparticles modified with coumarin, have been studied. Coumarin is a photo-responsive derivative, which induces photo-crosslinking when it is incorporated in the PU moieties. Swelling measurements were performed to study the photo-crosslinking fraction and the results are in concordance with the degree of crosslinking (DC) calculated by UV measurements. Shape memory behavior was studied by thermo-mechanical cycles, by measuring the strain recovery and shape fixity ratios of the photo-crosslinked films. The modification of silica nanoparticles allows an improvement in the dispersion of the reinforcements into the PU matrix, which leads to an enhancement of the shape memory properties. Finally, the materials were disintegrated under composting conditions at laboratory scale level to confirm their biodisintegrable behavior. Image 1 • Functional polyurethanes based on poly-e-caprolactone and coumarin have been evaluated as coatings. • Photo-crosslinking degree was measured by swelling and the results are in concordance with UV measurements. • The incorporation of coumarin-functionalized silica nanoparticles leads to a enhancement of the shape memory performance. • The nanocomposites were completely disintegrated after 14 days under composting conditions. [ABSTRACT FROM AUTHOR]

[Display omitted] • Raw lignin was modified through a green and scalable reactive extrusion design. • Lignin/poly(butylene adipate-co-terephthalate) biomaterials were melt processed up to 90 wt% bio-content. • Tough biomaterials were film blown and shopping bags were produced. • Mechanical recycling and composting were verified as end-of-life options. • Reactive design was industrially scaled-up in conventional twin screw extruder. [ABSTRACT FROM AUTHOR]

For soft robotics and programmable metamaterials, novel approaches are required enabling the design of highly integrated thermoresponsive actuating systems. In the concept presented here, the necessary functional component was obtained by polymer syntheses. First, poly(1,10-decylene adipate) diol (PDA) with a number average molecular weight Mn of 3290 g·mol−1 was synthesized from 1,10-decanediol and adipic acid. Afterward, the PDA was brought to reaction with 4,4′-diphenylmethane diisocyanate and 1,4-butanediol. The resulting polyester urethane (PEU) was processed to the filament, and samples were additively manufactured by fused-filament fabrication. After thermomechanical treatment, the PEU reliably actuated under stress-free conditions by expanding on cooling and shrinking on heating with a maximum thermoreversible strain of 16.1%. Actuation stabilized at 12.2%, as verified in a measurement comprising 100 heating-cooling cycles. By adding an actuator element to a gripper system, a hen's egg could be picked up, safely transported and deposited. Finally, one actuator element each was built into two types of unit cells for programmable materials, thus enabling the design of temperature-dependent behavior. The approaches are expected to open up new opportunities, e.g., in the fields of soft robotics and shape morphing. [ABSTRACT FROM AUTHOR]

Epoxy/Polycaprolactone (PCL) blends cured with a conventional diamine (4,4′-diaminodiphenylmethane, DDM) and with different amounts of a disulfide containing diamine (4, 4´-dithioaniline, DSS) were prepared through melting. The curing process was studied by FTIR and differential scanning calorimetry (DSC) and the mechanical behavior of the networks was studied by DMA. The shape memory properties and the recyclability of the materials were also analyzed. All blends showed a very high curing degree and temperature activated shape memory effect, related to the glass transition of the epoxy resin. The PCL plasticized the mixture, allowing tailoring of the epoxy glass transition. In addition, in the blends cured with DSS, as a consequence of the disulfide exchange reaction, the permanent shape could be erased and a new shape could be reprogrammed. Using this strategy, reprogrammable permanent shape memory materials were obtained. [ABSTRACT FROM AUTHOR]

Liquid crystal polymers have attracted massive attention as stimuli-responsive shape memory materials due to their unique reversible large-scale and high-speed actuations. These materials can be utilized to fabricate artificial muscles, sensors, and actuators driven by thermal order–disorder phase transition or trans–cis photoisomerization. This review collects most commonly used liquid crystal monomers and techniques to macroscopically order and align liquid crystal materials (monodomain), highlighting the unique materials on the thermal and photo responsive reversible shape memory effects. Challenges and potential future applications are also discussed. [ABSTRACT FROM AUTHOR]