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The waste-to-wealth strategy is encouraging the design of a plethora of new value-added materials, by exploiting the chemical and biological richness of biowastes. Humic Acids (HA) are mostly intriguing because of their amphiphilic supramolecular associations which are responsible for several assets, such as adsorption ability towards small molecules, metal ion chelation, redox behavior, and antibacterial activity. The molecular combination of HA with semiconductor nanoparticles represents a valuable strategy to obtain nanostructured hybrid materials and interfaces with advanced features. Concurrently, it permits to overcome intrinsic limits of such organic fraction, including poor stability, fast conformational dynamics, or rapid reactivity in aqueous media. Herein, hybrid HA/ZnO nanoparticles are synthetized through a bottom-up strategy, exerting an improved pro-oxidant behavior by generating Reactive Oxygen Species, even without light irradiation, f avoring an enhanced photocatalytic and antimicrobial activity against different bacterial pathogens. Several techniques, including SEM/TEM, DLS, ζ-potential, XRD, FTIR, TGA/DSC, EPR and DRUV, allows to define the structure-property-function relationships, thus highlighting the crucial role of a fine conjugation amongst the metal oxide precursor and bioderived fraction to drive the pro-oxidant activity. This study provides strategic guidelines to easily produce low-cost organo-inorganic nanomaterials with redox and biocide properties, aimed at coping environmental and health issues. [Display omitted] • A bottom-up wet-chemical strategy leads to hybrid humic acid-ZnO nanomaterials. • A molecular combination of precursors drives the colloidal and functional features. • The supramolecular design of nanohybrids valorizes the biowaste-derived molecules. • Nanostructured hybrid interfaces show high pro-oxidant and antibacterial activity. • ROS generation in aqueous medium occurs even without light irradiation. [ABSTRACT FROM AUTHOR]

A method is developed for rapid preparation of titania substrates using a sol–gel preparation route in combination with an amphiphilic block copolymer (BCP) template, acting as structure directing agent. The method consists in performing the spin coating of an initial solutions of BCP and titania species in a controlled atmosphere using a flux of solvent vapors (Rapid-Flux-Solvent-Atmosphere, RFSA method). The method is demonstrated in the case of thin films of polystyrene- b -poly(oxyethylene) BCP (PS-PEO) with cylindrical morphology of PEO domains in the PS matrix, characterized by the selective inclusion of titanium species inside the PEO cylinders. Upon removal of the organic matrix by heat treatment at 600 °C, titania substrates of different morphology are obtained depending on the concentration of titania precursor and processing conditions. The method allows preventing the negative effect of hydrolysis and condensation reactions of Ti species and titania substrates with morphology reminiscent of that one achieved in the hybrid nanostructured thin films are obtained. The RFSA method is simple, direct, and it is of particular interest for systems that require a short processing time to eliminate the solvent and to obtain regular nanostructured thin-films over large area. Merit figures such as the degree of hexagonal order and the degree of coverage of the surface with titania motifs are identified to characterize the hybrid composites and titania substrates. [ABSTRACT FROM AUTHOR]

In this paper the morphologies and crystallization properties of crystalline block copolymers are reviewed. The equilibrium morphologies expected in crystalline-amorphous diblock copolymers and the different modes of crystallization, such as, breakout, templated crystallization, confined crystallization and pass through crystallization are described. The effects of confinement on crystallization mode and crystallization kinetics are also analyzed in detail. The paper is focused on the morphologies and nanostructures produced in crystalline block copolymers based on polyolefins. Early studies performed on block copolymers containing highly defective polyethylene block, synthesized by hydrogenation of block copolymers containing 1,4-polybutadiene blocks prepared by classic anionic living polymerization, are described in the first part of the paper. Then, the paper features recent advances in the synthesis and characterization of crystalline block copolymers containing stereoregular polyolefins, such as stereoregular polypropylene and linear polyethylene prepared using novel organometallic catalysts able to promote the living and stereoselective polymerization of α-olefins. Strategies for creating nanoscale patters exploiting the ability to induce desired orientations of the crystalline phase through epitaxial crystallization of the crystallizable blocks on crystalline substrates are described. According to this strategy, the desired orientations of the crystalline phase may be suitably designed and act as templates to create the desired final ordered nanostructure. Image 1 • Living-stereoselective catalysts synthesize crystalline polyolefin block copolymers. • Equilibrium morphologies in crystalline block copolymers are described. • The segregation strength affects the crystallization mode and kinetics. • Crystallization of one block may be confined in crystalline lamellae of another block. • The presence of crystallinity may be exploited to create ordered nanostructures. [ABSTRACT FROM AUTHOR]

The crystalline morphology of ethylene/1-octene (EO-BC) statistical multiblock copolymers is investigated by transmission electron microscopy (TEM). EO-BCs are an important class of thermoplastic elastomers characterized by alternating crystalline, octene-poor, hard blocks and amorphous, octene-rich, soft blocks and statistical distribution of block length (BL) and number of blocks/chain (NB). Adopting similar crystallization conditions, samples with only subtle differences in the chain microstructure, are shown to display different solid-state morphology as probed by TEM and different melt rheology. In particular, the homogeneous or heterogeneous lamellar morphology which develops in the solid state reflects the tendency of the samples to show homogeneous or heterogeneous melt-rheology, respectively. As EO-BCs are a reactor blend of non-uniform chains, it is argued that the solid state and melt phase behavior of EO-BCs is controlled by differences in the relative abundance of chains including a prevalence of hard blocks of short and/or high length. Image 1 • The morphology of ethylene/1-octene multiblock copolymers is investigated. • They show solid-state homogeneous or heterogeneous morphologies. • The solid-state morphology reflects the melt-rheology behavior. • A high fraction of chains with long hard blocks drives a heterogeneous morphology. • A high fraction of chains with short hard blocks prevents heterogeneities. [ABSTRACT FROM AUTHOR]

Biodegradable active packaging, i.e. materials able to promote food preservation while avoiding plastic waste accumulation are expecting to play a key role fsor the manufacture of new generation materials. Bioactive films composed of citrus pectin (CP) added with extracts from spent coffee grounds (SCGs) were herein developed. To address the limitations of pectin-based materials, i.e. hydrophilicity and poor water barrier properties, an active multilayer film was prepared by coating the functionalized pectin by a two-steps dipping into polyhydroxyalkanoates (PHA) solutions characterized by different monomeric compositions. The PHA coating affected the stiffness of the film and its opacity, while improving its hydrophobicity and water vapor permeability. The dipping procedure did not compromise the stability of the bioactive compounds, rather it allowed to preserve their antioxidant and antimicrobial activities for longer times in comparison with uncoated functionalized film. Further, the multilayer material functionalized with extracts was able to delay the carotenoid degradation in mashed carrots likely because of the increased film opacity conferred by both phenols (caffeoylquinic acid isomers including chlorogenic acid) found in SCGs and PHAs layer suggesting that the new material may be used to extend the food shelf-life and potentially to enhance product health credentials. [Display omitted] • Pectin films were functionalized with phenolic extracts from Spent Coffee Grounds. • The films were coated by dipping into polyhydroxyalkanoates (PHA) solutions. • The functionalized multilayer displayed improved water sensitivity features. • Light-shielding properties of the functionalized multilayer were demonstrated. • The PHA layer allowed to keep the antioxidant and antimicrobial activity over time. [ABSTRACT FROM AUTHOR]

Background MNEI and its variant Y65R-MNEI are sweet proteins with potential applications as sweeteners in food industry. Also, they are often used as model systems for folding and aggregation studies. Methods X-ray crystallography was used to structurally characterize Y65R-MNEI at five different pHs, while circular dichroism and fluorescence spectroscopy were used to study their thermal and chemical stability. ThT assay and AFM were used for studying the kinetics of aggregation and morphology of the aggregates. Results Crystal structures of Y65R-MNEI revealed the existence of a dimer in the asymmetric unit, which, depending on the pH, assumes either an open or a closed conformation. The pH dramatically affects kinetics of formation and morphology of the aggregates: both MNEI and Y65R-MNEI form fibrils at acidic pH while amorphous aggregates are observed at neutral pH. Conclusions The mutation Y65R induces structural modifications at the C-terminal region of the protein, which account for the decreased stability of the mutant when compared to MNEI. Furthermore, the pH-dependent conformation of the Y65R-MNEI dimer may explain the different type of aggregates formed as a function of pH. General significance The investigation of the structural bases of aggregation gets us closer to the possibility of controlling such process, either by tuning the physicochemical environmental parameters or by site directed mutagenesis. This knowledge is helpful to expand the range of stability of proteins with potential industrial applications, such as MNEI and its mutant Y65R-MNEI, which should ideally preserve their structure and soluble state through a wide array of conditions. [ABSTRACT FROM AUTHOR]

Background Specific apolipoprotein A-I variants are associated to severe hereditary amyloidoses. The organ distribution of AApoAI amyloidosis seems to depend on the position of the mutation, since mutations in residues from 1 to 75 are mainly associated to hepatic and renal amyloidosis, while mutations in residues from 173 to 178 are mostly responsible for cardiac, laryngeal, and cutaneous amyloidosis. Molecular bases of this tissue specificity are still poorly understood, but it is increasingly emerging that protein destabilization induced by amyloidogenic mutations is neither necessary nor sufficient for amyloidosis development. Methods By using a multidisciplinary approach, including circular dichroism, dynamic light scattering, spectrofluorometric and atomic force microscopy analyses, the effect of target cells on the conformation and fibrillogenic pathway of the two AApoAI amyloidogenic variants AApoAI L75P and AApoAI L174S has been monitored. Results Our data show that specific cell milieus selectively affect conformation, aggregation propensity and fibrillogenesis of the two AApoAI amyloidogenic variants. Conclusions An intriguing picture emerged indicating that defined cell contexts selectively induce fibrillogenesis of specific AApoAI variants. General significance An innovative methodological approach, based on the use of whole intact cells to monitor the effects of cell context on AApoAI variants fibrillogenic pathway, has been set up. [ABSTRACT FROM AUTHOR]

The crystallographic micromechanical model (CMM) for prediction of yield stress of semicrystalline polymers, based on the thermally activated nucleation of screw dislocations at the boundary of lamellar crystals, is employed to interpret the yield behavior by effect of uniaxial drawing of some isotactic copolymers of propylene with different comonomeric units such as ethylene, 1-butene, 1-pentene, 1-hexene, and 1-octadecene (iPPEt, iPPBu, iPPPe, iPPHe and iPPOc, respectively). The samples are characterized by a random distribution of the comonomeric units. The CMM predicts that the values of stress at yield depend on the thickness of the lamellar crystals and relies on two parameters, i.e. the critical value of the free energy needed for nucleation and activation of a screw dislocation in crystallographic planes parallel to the chain axes, and the shear modulus relative to the planes of slip for the dislocations, whereas the role of the interlamellar amorphous phase is neglected. The aim of this study is to analyze to which extend the thickness of the lamellar crystals influences the yield stress for a series of propylene-based copolymers having a well-defined chain microstructure and crystallized in the α and/or γ forms, but possessing different degree of crystallinity, thickness of the lamellar crystals, stability of the crystals and also intrinsic flexibility of the portions of chains belonging to the amorphous regions, in relation with the degree of inclusion (exclusion) of the co-monomers in (from) the crystals. It is shown that, in the case of copolymers with a comonomer concentration lower than a threshold, the yield stress increases with increasing the lamellar thickness regardless of type of comonomer, the relative amount of the two polymorphs (α and γ forms), and the degree of inclusion, in good agreement with the predictions of the CMM approach. For copolymers with comonomer concentration higher than a threshold and bulky side groups, which are excluded from the crystals, the thickness of the lamellar crystals becomes low and the role of the chains in the amorphous regions becomes not negligible. In the case of copolymers with high butene concentration, instead, the stress at yield decreases with increasing the thickness of the lamellar crystals, because the high degree of inclusion of butene units in the crystals induces not only an increase in the thickness of the lamellar crystals, but also a decrease in the stability of the crystals, and the role of the chains located in the interlamellar amorphous layers acting as tie-molecules may not be disregarded. [ABSTRACT FROM AUTHOR]

Flavobacterium strains exert a substantial influence on roots and leaves of plants. However, there is still limited understanding of how the specific interactions between Flavobacterium and their plant hosts are and how these bacteria thrive in this competitive environment. A crucial step in understanding Flavobacterium - plant interactions is to unravel the structure of bacterial envelope components and the molecular features that facilitate initial contact with the host environment. Here, we have revealed structure and properties of the exopolysaccharides (EPS) produced by Flavobacterium sp. Root935. Chemical analyses revealed a complex and interesting branched heptasaccharidic repeating unit, containing a variety of sugar moieties, including Rha, Fuc, GlcN, Fuc4N, Gal, Man and QuiN and an important and extended substitution pattern, including acetyl and lactyl groups. Additionally, conformational analysis using molecular dynamics simulation showed an extended hydrophobic interface and a distinctly elongated, left-handed helicoidal arrangement. Furthermore, properties of the saccharide chain, and likely the huge substitution pattern prevented interaction and recognition by host lectins and possessed a low immunogenic potential, highlighting a potential role of Flavobacterium sp. Root935 in plant-microbial crosstalk. [Display omitted] [ABSTRACT FROM AUTHOR]

The mechanical properties and elastic behavior of Ziegler-Natta isotactic 1-butene-ethylene (BuEt-ZN) copolymers, having a broad composition from 1.7 to 45.5 mol% of ethylene units, are studied. The multi-site nature of the catalytic system determines a non-uniform distribution of the comonomers along the polymer chains; the copolymers present a blocky microstructure and composed of fractions of chains made of long and short butene sequences, which can be separated by solvent fractionation procedures. Incorporation of ethylene induces improving of drawability and decrease of rigidity with respect to homopolymer, associated with the lower crystallinity, and outstanding elastomeric behavior when the ethylene amount exceeds 5.5 mol%. In these copolymers the presence of irregular fractions of chains with short butene sequences, showing crystallization of the defective and low-melting temperature form I′ upon aging of the amorphous at room temperature, is responsible for the good elasticity of the materials. Image 1 • The mechanical behavior of BuEt-ZN blocky copolymers is studied. • The BuEt-ZN copolymers show remarkable elastomeric properties. • The formation of form I′ by crystallization of amorphous is the key for the elasticity. [ABSTRACT FROM AUTHOR]

The phase behavior of ethylene/propylene(/diene) (EP(D)M) co- (and ter-)polymers characterized by ethylene content in the range 64–78 wt%, and comparatively low level of crystallinity, in the range 1–15%, is analyzed during stretching, through collection of wide angle X-ray scattering data. All samples experience crystallization by effect of stretching, but whereas for the samples with ethylene content ≥71% crystallinity starts increasing already after yielding, the nearly amorphous sample, with 64 wt% ethylene content, experiences crystallization only at strain above a threshold (≈170%). In all cases, a high degree of orientation of the amorphous phase is achieved already at low deformations. It is shown that for the samples with high ethylene content, the pre-existing crystals undergo initial fragmentation and/or mechanical melting at low deformations, and successive oriented recrystallization at higher deformations. The role of oriented amorphous phase, along with the role of pre-existing crystals as nuclei able to foster further crystallization is highlighted. Image 1 [ABSTRACT FROM AUTHOR]

Abstract A method for assessing the puzzling molecular architecture of ethylene/1-octene multi-block copolymers, synthesized via chain-shuttling technology, is proposed. They are commercial elastomers characterized by alternating segments with low (hard blocks) and high (soft blocks) octene concentration. Our molecular assessment allows determining plausible value for the average length of blocks and number of blocks/chain, setting the basis for a definitive elucidation of structure-properties relationships of these elusive systems. Namely, the molecular basis which explains the similar crystallization properties, and the large difference in mechanical properties of this class of copolymers is unveiled thanks to our approach. We demonstrate that at 25 °C we have similar values of Young modulus and deformation at break higher than 1400%, but large strain hardening before breaking or flat mechanical behavior up to the break, depending on the short or long average block length of the multiblock copolymers, respectively, coupled with a high or low number of blocks/chain, respectively. At 60 °C these differences are amplified entailing no strain hardening but preservation of high ductility for copolymers with short average block length and high number of blocks/chain, remarkable decrease of strain at break of about two orders of magnitude (from ≈2000 to ≈90%) for copolymers with long average block length and lower number of blocks/chain. Graphical abstract Image 1 Highlights • Elastomers by chain shuttling technology have polydisperse multiblock structure. • The properties depend on the average length of blocks and number of blocks/chain. • A method is set up for the evaluation of these elusive parameters. • They verify the rules that govern the best efficiency of elastomeric networks. • Many short blocks show better mechanical properties than few long blocks. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • ZnEt 2 is evaluated as potential chain transfer agent in E- co -N copolymerization. • ZnEt 2 has different influence on E- co -N copolymerization, depending on metallocene. • ZnEt 2 causes a change of ductility, rigidity, and mechanical strength. • Segmented polymer chains are formed due to exchange between different metal centers. • Changes in mechanical properties are greater in copolymers with low N content. Abstract Ethylene (E)- co -norbornene (N) copolymerizations were conducted by using two ansa -metallocenes, isopropyliden(η5-cyclopentadienyl)(η5-indenyl)zirconium dichloride (1) and isopropyliden(η5-3-methylcyclopentadienyl)(η5-fluorenyl)zirconium dichloride (2), activated with dimethylanilinium tetrakis(pentafluorophenyl)borate, in presence of TIBA and variable amounts of Zn(Et) 2 as a potential chain transfer agent (CTA). The study evaluated the effect of CTA on microstructure, molecular weight, chain end group and structural, thermal and mechanical properties of poly(E- co -N)s. The analysis of the data revealed that in all copolymerization reactions with metallocenes 1 and 2 in presence of diethyl zinc chain transfer to zinc alkyl occurs along with the typical chain transfers of E- co -N polymerization. The chain transfer to zinc alkyl is more efficient at low N content in copolymers. The two catalysts show different behavior in copolymerization at high N content: molar masses of copolymers produced by 2 are more affected by CTA concentration, that is, the chain shortening with increasing CTA content is greater in copolymers obtained with catalyst 2. The analysis of mechanical properties revealed that CTA affects the polymer chain structure. An increase of CTA caused a change of ductility, rigidity, and mechanical strength; chains produced in presence of Zn(Et) 2 are, at least in part, characterized by segments produced as a result of exchange between different metal centers, possibly jointed through ethylene units. [ABSTRACT FROM AUTHOR]

The correlations between the thermal behavior and the crystal morphology of isotactic propene-pentene copolymers were studied through wide-angle (WAXS) and small-angle (SAXS) X-ray diffraction. Copolymers with pentene concentration lower than 11 mol% crystallize in the α form of isotactic polypropylene (iPP) and a concomitant decrease of melting temperature and of the thickness of crystalline lamellae with increasing pentene concentration has been observed. At higher pentene concentrations the trigonal form of iPP crystallizes and a neat increase crystalline lamellar thickness and of the long period, with a slower decrease of melting temperature and crystallinity have been observed. These results have been treated in the general framework of copolymer crystallization theories, using a method proposed by Crist and correlated with the different level of inclusion of pentene co-units in the crystals of α and trigonal forms. For copolymers with pentene concentration lower than 11 mol% pentene co-units are in part incorporated in the crystals of α form. For higher pentene concentrations the decrease of melting temperature coupled with the increase of lamellae thickness with increasing comonomer content is the hallmark of the almost total inclusion of pentene co-units in the crystals of the trigonal form. [ABSTRACT FROM AUTHOR]

Binary blends of samples of syndiotactic polypropylene of different stereoregularity have been prepared by mixing a more stereoregular and crystalline sample sPP1 having [ rrrr ] = 78%, with low stereoregular and poorly crystalline samples sam PP1 and sam PP2 having [ rrrr ] = 54.6 and 45.8%, respectively, and a nearly atactic fully amorphous sample am PP1 with [ rrrr ] = 26.5%. The blends show separate melting of the two components with the more stereoregular component sPP1 melting at high temperature and the poorly syndiotactic component melting at lower temperature. Crystals of sPP1 are formed by cooling from the melt whereas more defective crystals of sam PP1 and sam PP2 are formed by cold crystallization during aging at room temperature. The presence of the strereoirregular component disturbs the melt crystallization of the stereoregular component sPP1 and depression of the crystallization and melting temperatures of sPP1 in the blends is observed. On the other hand, the cold crystallization at room temperature of the irregular component is accelerated and favored by the presence of the more stereoregular component sPP1, whose crystals act as crystallization nuclei. All data indicate interactions between the components in the melt and amorphous state, compatible with a good degree of mixing. [ABSTRACT FROM AUTHOR]

When in contact with water, poly(lactic acid), PLA, undergoes severe physical changes. Hydrolysis is obviously the most expected and studied one, and it is followed by weight loss. However, other phenomena occur such as opacification and crystallization. Although these phenomena are sometimes reported in the literature, apart from hydrolysis which has been thoroughly studied at several temperatures, the other ones have not been deeply analyzed and their timescales have not been so far determined. This work aims at studying the physical changes induced by water sorption to PLA, by analyzing the modifications taking place in solid samples immersed in water for different times (starting from a few hours) and at temperatures close to the glass transition. The obtained results allow determining the timescales of the different phenomena and thus the possible cause-effect relationship among them. In particular, it is shown that opacity is the first phenomenon to become evident, on a timescale consistent with water sorption, and seems to be due to crazes induced by water. The second phenomenon to become evident is the crystallinity evolution, which is shown to be consistent with a heterogeneous nucleation on the crazes. These two phenomena take place before hydrolysis becomes significant, thus raising doubts about the fact that hydrolysis can be their cause. [ABSTRACT FROM AUTHOR]

Lipases are enzymes used for catalyzing reactions of acylglycerides in biodiesel production from lipids, where enzyme immobilization on a substrate is required. Silica nanoparticles in different morphologies and configurations are currently used in conjunction with biological molecules for drug delivery and catalysis applications, but up to date their use for triglycerides has been limited by the large size of long-chain lipid molecules. Matrix assisted pulsed laser evaporation (MAPLE), a laser deposition technique using a frozen solution/suspension as a target, is widely used for deposition of biomaterials and other delicate molecules. We have carried out a MAPLE deposition starting from a frozen mixture containing fumed silica and lipase in water. Deposition parameters were chosen in order to increase surface roughness and to promote the formation of complex structures. Both the target (a frozen thickened mixture of nanoparticles/catalyst in water) and the deposition configuration (a small target to substrate distance) are unusual and have been adopted in order to increase surface contact of catalyst and to facilitate access to long-chain molecules. The resulting innovative film morphology (fumed silica/lipase cluster level aggregation) and the lipase functionality (for catalytic biodiesel production) have been studied by FESEM, FTIR and transesterification tests. [ABSTRACT FROM AUTHOR]

A study of the structure and properties of binary blends of syndiotactic polypropylene (sPP) having different degrees of stereoregularity and synthesized by different metallocene catalysts, is reported. The blends have been prepared by mixing a stereoregular and crystalline sample with [ rrrr ] = 78% with low stereoregular and poorly crystalline samples having [ rrrr ] = 54.6 and 45.8%, and a nearly atactic fully amorphous sample with [ rrrr ] = 26.5%. All blends show outstanding elastomeric properties with rigidity and tensile strength that can be tailored by changing the stereoregularity of the components and blend composition. A continuous change of properties with composition is observed, from those of high-modulus thermoplastic elastomers for blends having high concentration of the most syndiotactic sample sPP1, to those of low-strength elastomers for blends with high content of the less syndiotactic component. The addition of the stereoirregular component to the more stereoregular sample produces an effect on the crystallization behavior and mechanical properties analogous to that produced by incorporation of defects of stereoregularity. Blends behave as a single sPP component having an average degree of stereoregularity intermediate between those of the two components. All data indicates a good miscibility of the sPP chains of different stereoregularity in the melt and in the amorphous state. [ABSTRACT FROM AUTHOR]

The crystallization behavior and the mechanical properties of random isotactic butene–octene copolymers (iPBC8) prepared with a metallocene catalyst are presented. Samples with low octene concentrations, up to nearly 6 mol%, crystallize from the melt in form II. In these samples octene units stabilize the tetragonal form II, decelerating or even preventing the transformation of form II into the trigonal form I. Octene concentrations higher than 7 mol% prevent crystallization of the samples from the melt and the obtained amorphous samples crystallize by aging at room temperature in mixtures of form II and form I'. The sample with the highest octene concentration of 11.5 mol% crystallizes surprisingly from the amorphous phase directly in the pure form I'. In these samples, form I' crystallized from the amorphous phase transforms into form II by stretching. Form II transforms back into form I' upon releasing the tension. Therefore, in samples where form I' is favored in powder samples, form II is favored in stretched fibers. The transformation of form I into form II by stretching and the back transformation of form II into form I after releasing the tension is unusual for isotactic polybutene (iPB) and rather unexpected. The presence of octene comonomer units also affects the mechanical behavior of iPB and produces increase of flexibility and ductility with increasing comonomer content, and samples with octene concentration higher than 6–7 mol% show unexpected remarkable elastomeric properties. The formation of crystals of form II or form I' during aging allows development of elastomeric properties and enhancement of mechanical strength. The elastic properties are associated to the reversible crystal–crystal phase transition between form II and form I occurring during stretching and when the tension is removed. [ABSTRACT FROM AUTHOR]

Highlights: [•] The mesomorphic form of iPP crystallizes also in stereoirregular samples. [•] The mesophase of stereoirregular samples transforms into α form at 25°C. [•] The mesophase always transforms into α form by annealing at T >60–70°C. [•] The transformation into α form occurs even in samples that crystallize into γ form. [•] Evidences supporting the structure model of the mesophase of iPP are given. [ABSTRACT FROM AUTHOR]

Abstract: A study of the crystallization of the mesomorphic form of isotactic polypropylene (iPP) in samples of different stereoregularity prepared with metallocene catalysts is presented. Contrary to what claimed in the literature, we have found that the mesomorphic form can be obtained by quenching of the melt at 0 °C also in the case of low stereoregular samples, provided that the samples are kept at 0 °C for long time. The key is the formation of mesomorphic bundles with chains in ordered 3/1 helical conformation of size large enough to be stable and inhibit the crystallization of the α form at room temperature. For stereoirregular samples the concentration of long ordered helical stretches is low and this requires long residence time at 0 °C for the formation of mesomorphic aggregates of size larger than the critical size. This result provides evidence that the mesomorphic aggregates are not formed as a result of a cooperative process driven by entropy, as in the case of liquid crystals, but rather they form via a nucleation and growth mechanism, as in the normal crystallization processes, according to the idea that the mesophase of iPP is a highly defective crystalline form. [Copyright &y& Elsevier]

Abstract: The structure and properties of blends of poly(ethylene terephthalate) (PET) with poly(trimethylene terephthalate) (PTT) at PTT concentration ≤30 wt.%, obtained with three different methods: from solution, melt extrusion, and direct spinning, are investigated. Relationships between the method of preparation and properties of blends are established. All blends show glass transition temperature at values determined by composition, and crystallization properties also dependent on the preparation method. Blends obtained from solution show separated melting of components. For blends obtained from the melt only PET crystallizes. The melting temperature decreases with the residence time of the melt at high temperatures, due to occurrence of ester exchange reactions. It is shown that reactive blending of PET/PTT mixtures occurring during preparation is a versatile route for obtainment of engineering materials with good mechanical properties, high crystallinity, glass transition temperature lower than that of PET, and melting temperature that may be controlled by the processing conditions. [Copyright &y& Elsevier]

The effects of spermidine (SPD) on the properties of both secalin (SCL)-based film-forming solutions (FFSs) and their resultant films were studied in the absence or presence of glycerol (GLY) used as primary plasticizer. The average size of SCL particles significantly increased with the increase of SPD concentration, mainly in the presence of GLY, while the negative zeta potential values parallely decreased suggesting a greater stability of the FFSs containing SPD concentrations lower than 1.0 mM. In addition, the decreased contact angle value, compared to water and ethanol solution, indicated that SCL FFSs were highly hydrophobic and that it might be spreaded easily on hydrophobic biological surfaces. SPD could replace GLY in obtaining handleable, homogeneous and performing SCL-based films. The film tensile strength and the Young's module strongly increased in the absence of GLY, reaching values higher than 5 times with respect to controls, whereas elongation at break value of GLY-plasticized films containing 5.0 mM SPD was twice of that of the films prepared without SPD. Conversely, the film moisture content, water solubility and swelling ratio progressively decreased, both in the presence and absence of GLY, up to a SPD concentration of 1.0 mM, whereas the film contact angle increased, confirming the enhancement of its hydrophobicity determined by SPD incorporation. SPD also increased the film barrier properties to gases and water vapor, while the presence of GLY hindered these effects. Finally, SEM analysis of the cross-sections of the SPD containing films showed heterogeneous microstructures, whereas their surfaces appeared rougher than those of the control films. Preliminary experiments carried out by Rosa chinensis Jacq. leaf coating suggest the potential use of SCL-based FFSs spraying in plant disease control. High spreading of the SCL-based FFSs on the entire leaf surfaces, both in the presence and absence of Bordeaux mixture tested as agrochemical, was observed, and the SEM images showed the formation of an evident coating of the leaves. Therefore, these findings suggest the possibility to coat the leaf surface also in vivo with different SCL-based FFSs, giving rise to films possessing tailored functional properties and able to carry and release different agrochemicals. [Display omitted] [ABSTRACT FROM AUTHOR]

With the aim to create new food ingredients and packaging, cross-linked secalin (SCL) was synthesized by papain-catalyzed disulfide bond formation in the presence of N-acetyl- dl -homocysteine thiolactone (AHTL). The effects of SCL structural modification on the protein functional properties, as well as of the derived films, were investigated at several concentrations of AHTL and compared to those produced by the iso-peptide bonds formed in the presence of different concentrations of transglutaminase (TG). Cross-linked SCL exhibited improved emulsifying and foaming properties, whereas the derived films showed increased mechanical, barrier and water resistance properties. In particular, AHTL/papain mediated cross-linking was more effective in increasing the elongation at break (200%), Young's modulus (200 MPa), surface hydrophobicity and barrier properties of SCL-based films (water permeability halved, that to oxygen one tenth and that to carbon dioxide one twentieth), while films obtained with TG cross-linked SCL showed higher tensile strength (4 MPa) and lower swelling index (83%). SEM analyses showed a more compact structure in the films obtained with AHTL/papain-cross-linked SCL, whereas thicker films (50% more) with porous surface fractures were observed when SCL was formerly modified by TG. The different behavior of the two groups of films prepared with SCL differently cross-linked was probably due to the different microstructure of the derived films dependent on the shorter distance of iso-peptide bonds obtained by TG with respect to the disulfide bonds resulting from AHTL/papain reaction. These findings indicate that the two different enzymatic cross-linking methods can be used to prepare SCL with improved functional properties to be utilized as food ingredient or for potential packaging applications. [Display omitted] • Secalin (SCL) was cross-linked by either papain and N-acetylhomocysteine or transglutaminase. • Cross-linked SCL showed improved emulsifying and foaming properties. • The two cross-linking enzymes led to SCL-based films with different microstructures. • The films obtained had improved mechanical, barrier and water resistance features. • New food ingredients and packaging materials might be manufactured with cross-linked SCL. [ABSTRACT FROM AUTHOR]

The tensile properties and the structural transformations occurring by effect of deformation of un-vulcanized ethylene/propylene(/diene) elastomers with ethylene contents ranging from 57 to 83 mol% are analyzed and interpreted in terms of the chain microstructure. It is shown that the samples with ethylene contents larger than or equal to 73 mol% experience a slight but significant increase of crystallinity upon stretching and partial melting of the new oriented crystals formed by stretching after releasing the tension. The degree of crystallinity, the tensile properties, the incremental crystallinity achieved upon stretching and the residual crystallinity left upon release of the tension all show well-defined correlations with the average ethylene content and the ethylene sequence length distribution. The tensile properties and the strain hardening behavior are correlated with the incremental crystallinity achieved upon stretching at high strain. [Display omitted] • The structure & properties of ethylene/propylene(/diene) rubbers are investigated. • The chain microstructure controls the strain induced crystallization (SIC). • For ethylene content >80 mol%: moderate SIC entails moderate strain hardening (SH). • For ethylene content <80 mol% and >70 mol%: high SIC entails high SH. • For ethylene content <70 mol%: low SIC entails low SH. [ABSTRACT FROM AUTHOR]

The melting/crystallization properties of blends obtained by mixing two isotactic polypropylene (iPP) samples synthesized using single-site metallocene catalyst systems and containing a high and low concentration of rr triads as stereo-defects, are studied. The changes occurring at lamellar length scale during a heating/cooling cycle at constant scanning rate are followed in situ by performing time-resolved small angle X-ray scattering (SAXS) measurements. Data analysis demonstrates that the evolution of the SAXS intensity with increase/decrease of the temperature is controlled by the separate melting/crystallization of the two components, the differences in the thermal expansion (contraction) coefficient of the amorphous and crystalline phases and the role of thermal fluctuations in electron density. The two components give rise to different populations of intermixed lamellar stacks in the blends which originate from the good miscibility of the low and high stereoregular samples in the melt. • Blends of a high and a low stereoregular isotactic polypropylene are analyzed. • SAXS probes the separate melting/crystallization of the components. • The good miscibility in the melt induce formation of intermixed lamellar stacks. • SAXS also probes thermal fluctuations in electron density. • The high temperature SAXS analysis provides information about the melt strength. [ABSTRACT FROM AUTHOR]

This work succeeded in the preparation of a nano-biocomposite material based on the use of poly-3-hydroxybutyrate-co-hydroxyhexanoate nanoparticles (PHBHHx-NPs) within a scaffold of whey protein (WP) based films. The experimental conditions for PHBHHx-NPs preparation by solvent-evaporation technique were set up, and the obtained NPs characterized. Dynamic light scattering analyses showed that PHBHHx-NPs are stable, exhibiting a zeta-potential value close to −40 mV and a Z-average size of 80 nm. Morphological characterization by transmission and scanning electron microscopy confirmed nanoparticle average dimensions. The addition of PHBHHx-NPs to WP-based films improved the mechanical properties of the derived bioplastics, producing more extensible materials preserving their mechanical resistance. The grafting of PHBHHx-NPs as material fillers also enhanced the film barrier properties towards O 2, the permeability to both water vapor and CO 2 remaining unaffected. Image 1 • Design of poly (3-hydroxybutyrate-co-hydroxyhexanoate) nanoparticles (PHBHHx-NPs). • Evaluation of PHBHHx-NPs as nanofillers in whey-protein based films. • Derived biocomposites with improved flexibility and reduced O 2 permeability. [ABSTRACT FROM AUTHOR]

A study of the crystallization behavior and kinetics of form II-form I transition in isotactic butene-ethylene copolymers (iPBEt) prepared with Ziegler-Natta catalyst with ethylene concentration in the range 9–44 mol% is presented. The samples have been separated with boiling solvents in different fractions containing chains with different ethylene concentration. Crystallization of form II from the melt is observed in each fraction even at high ethylene concentration, up to nearly 16 mol%. For higher ethylene content the samples do not crystallize from the melt but still crystallize during aging at room temperature in form I′. The comparison with the crystallization behavior of iPBEt copolymers prepared with homogeneous metallocene catalysts, characterized by a random distribution of ethylene units, has shown that the form II-form I transformation in Ziegler-Natta copolymers is much slower than in metallocene copolymers having the same ethylene concentrations and for the metallocene copolymers a low concentration of ethylene units of nearly 6 mol% is sufficient to prevent crystallization from the melt of form II. This indicates that in the chains of Ziegler-Natta iPBEt copolymers the regular butene sequences interrupted by the ethylene units are much longer than those of the chains of copolymers prepared with metallocene catalysts of the same ethylene concentration, giving further evidence of the multiblock structure of Ziegler-Natta iPBEt copolymers. Image 1 • The crystallization behavior of iPBEt-ZN block copolymers is studied. • The comparison with metallocene iPBEt-Met random copolymers is presented. • Form II-Form I transition in iPBEt-ZN is slower than in iPBEt-Met copolymers. • The crystallization of Form I′ and Form II is driven by the average length of butene sequences. [ABSTRACT FROM AUTHOR]