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Novel 4-methyl-1-pentene/1,5-hexadiene isotactic copolymers (iP4MPHD) incorporating methylene-1,3-cyclopentane (MCP) cyclic co-units with concentrations in the range 4.4–17.6 mol % have been synthesized by using the dimethylpyridylamidohafnium/organoboron catalyst. The influence of the MCP cyclic co-unit on the crystallization behavior and the mechanical properties of the isotactic poly(4-methyl-1-pentene) (iP4MP) homopolymer has been investigated in detail. iP4MPHD copolymers with comonomer content up to 11 mol % crystallize in form II of iP4MP from the polymerization solution and in the stable form I of iP4MP from the melt, whereas the sample with the highest concentration (17.6 mol %) of 1,5-hexadiene (1,5-HD) is amorphous and does not crystallize from either solution and melt. All crystalline samples exhibit high melting temperatures, always above 120 °C, and a controlled glass transition temperature close to the room temperature (28–30 °C). Incorporation of MCP units into iP4MP chains produces an improvement in flexibility and allows tailoring of deformability while retaining high mechanical resistance and transparency of the homopolymer. Interestingly, the high deformability is maintained at low temperature (50 °C below the glass transition temperature), suggesting a cooperative role of both amorphous and crystalline phases in the deformation mechanism that enhances ductility. All stress–strain curves of the different copolymers present an unusual second maximum at strains higher than the yielding point. Diffraction patterns recorded during deformation have revealed that this second maximum is associated with the crystallization under stretching of a highly disordered crystalline mesophase never described in the literature.

The crystallization from the melt in isothermal conditions of metallocene random propene–pentene isotactic copolymers (iPPC5) has been studied. All samples with pentene concentration between 0.5 and 10 mol % crystallize at any crystallization temperature in mixtures of α and γ forms of isotactic polypropylene (iPP) and the amount of γ form increases with increasing crystallization temperature up to a maximum (fγ(max)), which depends on pentene concentration. Pentene defects produce a shortening of the regular propene sequences that in turn induces crystallization of the γ form. At concentrations higher than 6–7 mol %, pentene units are incorporated to a high extent in the crystals of α and trigonal forms, which are stabilized over the γ form, and fγ(max) decreases. The maximum fraction of γ form is, therefore, related to the average length of regular propene sequences and the degree of incorporation of defects in the crystals of α and γ forms. The values of fγ(max) that develop in iPPC5 copolymers have been compared with those that develop in copolymers of iPP with ethylene (iPPC2), butene (iPPC4), and hexene (iPPC6) and in stereoirregular iPPs reported in the literature. Stereoirregular iPPs and iPPC2 copolymers give the same relationship between fγ(max) and the average length of regular propene sequences (LiPP), whereas iPPC4, iPPC5, and iPPC6 copolymers show different behaviors. In particular, iPPC5 copolymers exhibit a behavior intermediate between those of iPPC4 and iPPC6 copolymers. The relationship between fγ(max) and LiPPof iPPC5 copolymers fits perfectly between the relationships found for iPPC4 and iPPC6 copolymers, in agreement with the different types and sizes of comonomers and the different efficiencies of their interruption and inclusion effects. These data give evidence of the general view of the crystallization behavior of iPP, based on the definition of a double role exerted by defects, the interruption effect that shortens the regular propene sequences and favors crystallization of γ form, and the effect of incorporation of defects into the crystalline unit cells of α and γ forms, which favors crystallization of the form that better accommodates the defect into crystals. The relative efficiency of these two effects depends on the type and size of the defect. The different relationships between fγ(max) and LiPPare a result of the equilibrium between interruption and inclusion effects achieved by each defect and confirm that the crystallization of γ form is a perfect indicator of the length of the regular propene sequences and may provide very detailed information on the molecular structure of iPP.

The mechanical properties of copolymers of syndiotactic polypropylene (sPP) with 1-hexene and 1-octene have been studied and correlated with the structural transformations occurring during stretching and relaxation. These copolymers crystallize in disordered modifications of form I of sPP, with crystallinity, melting, and glass-transition temperatures that decrease with increasing comonomer content. All copolymers show remarkable mechanical properties and elastic behavior, with great improvement of flexibility and ductility with respect to the sPP homopolymer already at small comonomer concentrations. For low comonomer content up to 4–5 mol %, the elastic recovery is associated to a reversible conformational phase transition between the trans-planar form III or the trans-planar mesophase and the helical form II, which gives an enthalpic contribution to the elasticity. As the comonomer content increases, the trans-planar conformation is progressively destabilized and the observed elastic properties are not associated with any conformational transformation during stretching and relaxation. In these cases, copolymers behave as conventional thermoplastic elastomers where elasticity is purely entropic and crystals only act as topological constraints of the elastomeric network. These copolymers represent an exemplary case of the possibility to combine in the same materials desired and apparently incompatible physical properties of elasticity, crystallinity, and strength by controlling the crystallization behavior, achieved by tailoring the chemical structure in the synthetic process.

Samples of block copolymers (BCP) constituted by semicrystalline blocks of linear low-density polyethylene (LLDPE) and isotactic polypropylene (iPP) of different block lengths (iPP-b-LLDPE) have been prepared by living polymerization using the hafnium-based catalyst that provides high steric control and isotactic propagation of propene units. The LLDPE blocks are random ethylene/1-octene copolymers with 1-octene concentrations between 1 and 3 mol %. The crystallization behavior and the morphologies in the melt and after the crystallization of iPP-b-LLDPE are presented. The iPP block melts at 135 °C, according to the moderate isotacticty, whereas the LLDPE blocks melt at lower temperatures, between 101 and 113 °C, depending on the 1-octene concentration. Both blocks crystallize from the melt and wide-angle diffraction and small-angle scattering profiles acquired with synchrotron radiation during cooling have demonstrated that the iPP block crystallizes first upon cooling, except for the sample with the lowest iPP molecular mass, for which PE and iPP crystallize almost simultaneously. The small-angle scattering recorded during cooling and crystallization of iPP and LLDPE blocks shows the emergence of a single broad scattering peak ascribed to the formation of stacks of crystalline lamellae of indistinguishable iPP and LLDPE with values of the long period of 13–14 nm. Electron microscopy (TEM) analysis allowed us to image the microphase-separated microdomain structure present in the melt and frozen or preserved at room temperature after crystallization. The TEM analysis has demonstrated that phase-separation of the dissimilar blocks occurs in the melt. The formed microdomain structure is preserved after crystallization of both blocks, and pass-through crystallization occurs with iPP and PE lamellae crossing through the different microdomains without overwhelming the microphase-separated structure.

Chromium complexes bearing non-innocent iminopyridine ligands were investigated as precatalysts for the polymerization of ethylene using different aluminum cocatalysts and Lewis base NEt3as additive. Beyond confirming the key role of the chromium to ligand synergyin accessing the active complex, other factors that play a crucial role are (i) the nature of the aluminum activator that influences the ion pair generated, (ii) the presence of the additive that boosts the synthesis of UHMWPE with narrow and unimodal molecular weight distribution even at 40 °C, and (iii) the polymerization temperature that affects the polymerization catalysis and the polymer molecular weight. UV–vis–NIR and Fourier transform infrared (FT-IR) spectroscopic techniques have been applied to inspect the activation process and to understand the mode of action by which NEt3affects the catalytic conversion of ethylene. NEt3interacts with the aluminum cocatalyst (rather than with the chromium complex) to form an Et3N*AlRxadduct, thus affecting the catalytic ion pair.

A study of the morphology of diblock copolymers composed of two crystalline blocks of isotactic polypropylene (iPP) and polyethylene (PE) is shown. The samples form phase-separated structures in the melt because of the incompatibility between iPP and PE blocks. Cylindrical PE microdomains are visible at room temperature in the sample with a PE volume fraction of 26%, rapidly quenched from the melt in liquid nitrogen. In the quenched sample, PE crystallizes inside the PE cylindrical microdomains, whereas crystals of iPP are not visible in the iPP domains because the quenching prevents crystallization of the lamellar α form. Less rapid cooling of the melt produces, instead, breakout crystallization, where the phase-separated structure of the melt is destroyed by the slow crystallization of the α form of iPP and of PE. The succession of crystallization of iPP and PE and the resulting final morphology have been analyzed by inducing selective and different orientations of iPP and PE crystals through epitaxial crystallization onto the benzoic acid (BA) crystal substrate. Epitaxy produces oriented crystallization of iPP and PE, with a unique alignment of PE lamellar crystals and a double orientation of iPP crystals on to the (001) exposed face of BA. Epitaxy destroys the phase-separated structure of the melt and induces the formation of ordered lamellar nanostructures with alternated layers of iPP and PE, whose orientation is defined by the alignment of PE or iPP crystals, which, in turn, is determined by epitaxy. The results indicate that crystalline block copolymers offer the opportunity to create nanoscale patterns on thin films and improve the possibility of controlling the microstructure of block copolymers and the alignment of microdomains by controlling the crystallization process.

Highly accurate high-throughput experimentation (HTE) data for a set of 21 silicon-bridged C2-symmetric ansa-zirconocenes in propene homopolymerization were collected and were used to develop quantitative structure – activity relationship (QSAR) models for several performance indicators at high polymerization temperature (Tp= 100 °C) by using chemically meaningful descriptors. Most notably, stereoselectivity is well described by a two-descriptor model linking the quadrant model for stereoselectivity (sterics) with the chain epimerization model (electronics). The catalysts show widely varying temperature responses, most notably on stereoselectivity and molar mass capability, while the regioselectivity response is uniformly weak. Soft conformational locks lose their performance rapidly while hard conformational locks offer enhanced performance even at high temperatures. The quest for high-temperature stable, well-performing ansa-zirconocenes will unquestionably lead to systems with enhanced rigidity.

Thermoplastic elastomers (TPEs) are materials combining the processability of thermoplastics and the elasticity of rubbers. The global value and demand of TPEs are expected to grow in the coming years, and advancement in synthetic chemistry is the key driving force. This contribution provides a simple synthesis of high-ethylene EPDMs with high molecular weight, narrow molecular weight distribution (1.9 < Mw/Mn< 2.3), and properties which can be adjusted from soft thermoplastic to elastomer. EPDMs are prepared through the terpolymerization of ethylene with propylene and 5-ethylidene-2-norbornene (ENB), where ethylene is continuously supplied to the reaction bath, while propylene and ENB are added only at the beginning. Polymerizations are catalyzed by three known imido vanadium(IV) complexes, differing in the imido substituent and coligand, in combination with Et2AlCl and Cl3CCO2Et. The obtained EPDMs are a mixture of macromolecules, each of them featuring a nonrandom comonomer distribution and nonuniform composition. Each chain likely contains multiblockswhere the comonomers are segmented, i.e., blocks with high ethylene content that may crystallize and blocks with high propylene and ENB content that may not crystallize. This broad chemical composition distribution is due to time drift that occurs during the polymerization, which in turn depends on the experimental conditions and ligand set. Composition drift causes variation in the instantaneous feed comonomer ratio and hence in the chemical composition of the terpolymer over the period of conversion. In proper experimental conditions, EPDMs behave as TPEs without the need of vulcanization, polymer blending, and reinforcement through the addition of fillers. They exhibit high elongation at break, strain hardening at large deformation, remarkable shape retention properties (up to 76% recovery after 10 cycles at 300% and about 90% at 410% strain), and remelting processability with no fall in properties for recycle and reuse.

Isotactic propylene–butene copolymers [i(P-co-B)] with precise and controlled molecular structures were synthesized with various organometallic catalysts having different stereoselectivities. Stereoregular and stereodefective samples of i(P-co-B) with 1-butene (B) content variable in the whole range of composition were synthesized. All samples crystallize regardless of composition, indicating cocrystallization of propene and 1-butene units, which are incorporated in the unit cells of polymorphic forms of isotactic poly(propylene) (iPP) and isotactic poly(1-butene) (iPB). The copolymers show a continuum change of crystal morphology with the composition, transforming from big spherulites to bundle-like and needle-like crystals, to granular crystals. The cocrystallization allows maintaining high crystallinity of copolymers for any composition and provides an opportunity to develop outstanding mechanical properties that can be tailored by changing the isotacticity and composition. This allows, ideally, combining in the same material the different properties of stiffness of iPP and flexibility of iPB. These copolymers show, indeed, mechanical properties intermediate between iPP and iPB, ranging from stiffness/brittleness and ductility/flexibility depending on the composition and isotacticity, with high strength and Young’s modulus that may be regulated by the stereoregularity of the iPP and iPB sequences, which is, in turn, dictated by the catalyst structure.

An example of breaking “Ewen’s symmetry rule” for olefin catalysis polymerization is proposed by DFT calculations. Catalyst precursors with Cssymmetry are suggested to promote the isotactic propene polymerization by a modification of the active site geometry obtained via coordination with AlH–alkyl species in solution. The origin of stereocontrol in olefin polymerization is due to a dual mechanism dictated by the chiral catalyst. These findings may expand the toolbox for promoting stereoselective olefin polymerization by transition metal catalysts.

The crystallization and thermal properties of copolymers of isotactic poly(1-butene) (iPB) with ethylene (iPBEt) synthesized with a Ziegler–Natta catalyst and ethylene (E) content between 7 and 45 mol % are presented. The crystallization properties provide evidence of a multiblock molecular structure of these copolymers. The samples have been separated in two or three fractions by standard fractionation in boiling solvents. Samples with ethylene concentration lower than 16 mol % surprisingly crystallize in form II of iPB, and crystallization of polyethylene also occurs for the maximum ethylene content of 45 mol %. Even more surprising is the result that the melting temperature of crystals of any polymorphic form of iPB that crystallize in these samples do not depend on the ethylene concentration. This suggests that long crystallizable butene sequences are present even at high ethylene concentration. In all fractions, the chains are composed of multiblocks where the comonomers are segregated, with blocks characterized by long crystallizable butene sequences and blocks with shorter butene sequences. In the different fractions, the average length of butene sequences is nearly the same. The different fractions are featured by different amounts of the constituting blocks.

The mechanical properties and the structural transformations occurring during deformation of some commercial grades of ethylene/1-octene multiblock copolymers (OBCs) obtained from chain shuttling technology are analyzed. The samples are characterized by a statistical multiblock architecture, where soft and amorphous blocks with high octene concentration (≈18.9 mol %) alternate with hard and crystalline blocks with low octene concentration (≈0.5 mol %). The length of blocks (BL) and the number of blocks/chain (NB) change from chain to chain according to a statistical distribution. The selected samples have molecular mass in the range 85–130 kg/mol, percentage of hard segments in the range 15–27%, and a melting temperature of ≈120 °C. The average molecular masses of the hard blocks MHand soft blocks MSare in the ranges 2–3 kg/mol and 6–15 kg/mol, respectively, whereas the number of blocks/chain is in between 2 and 17. Even though the samples are characterized by similar octene concentration, small difference in molecular mass, and fractional content of hard blocks, they show remarkable differences of mechanical properties, depending on the average BL and NB values, encompassing from those of strong elastomers, in the case of samples with low block length and high number of blocks/chain, to those of soft elastomers, in the case of samples with high block length and low number of blocks/chain. The differences in the mechanical properties of OBC samples are amplified by stretching at high temperatures. Not previously stretched films obtained by compression molding show only partial recovery of the initial dimensions in mechanical cycles of stretching and releasing the tension, with values of recovered strain higher than 50% at 25 °C. However, the resultant specimens obtained by release of the tension show good elastomeric properties in a wide deformation range at 25 °C and, in the case of the samples with high strength, also at 60 °C. Fiber diffraction analysis reveals that by stretching at high deformation the orientation of the crystals is accomplished by mechanical melting and formation of an oriented amorphous phase, namely, involving the hard segments extracted from the crystals. Upon releasing the tension recrystallization occurs, and the high degree of orientation achieved by the crystals and amorphous phase is lost.

Highly ordered lamellar nanostructures with high orientation of lamellar microdomains have been obtained by epitaxial crystallization of crystalline diblock copolymers constituted by crystalline polyethylene (PE) linked to an amorphous block of a propene-ethene random copolymer (EP). The epitaxial crystallization onto crystals of p-chlorobenzoic acid induces formation of crystalline PE lamellae highly aligned along one direction, resulting in ordered lamellar nanostructures with perfectly aligned layers of crystalline PE alternating to amorphous layers of EP block. The periodicity of the lamellar structure can be modulated by modifying the molecular mass of the amorphous EP block. Epitaxy has been coupled with the technique of gold decoration so that the ordered nanostructures produced by epitaxy act as template for the formation of long, straight, and parallel rows of gold nanoparticles.

We set up a facile approach for fabrication of supports with tailored nanoporosity for immobilization of enzymes. To this aim block copolymers (BCPs) self-assembly has been used to prepare nanostructured thin films with well-defined architecture containing pores of tailorable size delimited by walls with tailorable degree of hydrophilicity. In particular, we employed a mixture of polystyrene-block-poly(l-lactide) (PS-PLLA) and polystyrene-block-poly(ethylene oxide) (PS-PEO) diblock copolymers to generate thin films with a lamellar morphology consisting of PS lamellar domains alternating with mixed PEO/PLLA blocks lamellar domains. Selective basic hydrolysis of the PLLA blocks generates thin films, patterned with nanometric channels containing hydrophilic PEO chains pending from PS walls. The shape and size of the channels and the degree of hydrophilicity of the pores depend on the relative length of the blocks, the molecular mass of the BCPs, and the composition of the mixture. The strength of our approach is demonstrated in the case of physical adsorption of the hemoprotein peroxidase from horseradish (HRP) using 2,2′-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS) with H2O2as substrate. The large surface area, the tailored pore sizes, and the functionalization with hydrophilic PEO blocks make the designed nanostructured materials suitable supports for the nanoconfinement of HRP biomolecules endowed with high catalytic performance, no mass-transfer limitations, and long-term stability.

The morphology and the electrical properties of hybrid nanocomposites characterized by the dispersion of ZnO nanoparticles (NPs), a n-type semiconductor, within an organic nanostructured matrix of polystyrene-b-poly(methyl methacrylate) (PS-b-PMMA) block copolymer are presented. A selective inclusion of NPs only into the lamellar PS nanodomains of the block copolymer matrix has been achieved by synthetizing ZnO NPs coated with n-hexadecylamine (HDA) and tert-butylphosphonic acid (TBPA) molecules and subsequent thermal annealing of the nanocomposites ZnO NPs/PS-b-PMMA. Thermal treatments have allowed obtaining in one step the vertical orientation of the lamellar BCP nanodomains and the migration of the NPs to the PS domains, resulting in the formation of nanocomposites characterized by a precise control of the position of n-semiconductor ZnO NPs. Current–voltage measurements on the nanocomposites have indicated the presence of continuous path of charge carriers in the BCP films when the ZnO NPs content is above a threshold concentration. The experimental results have allowed the setup and validation of a theoretical protocol to study heterogeneous interfaces. In particular, the interaction of ZnO most stable nonpolar surface with prototypical capping agents has been analyzed by using density functional theory (DFT) calculations.

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, favoring 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.

Copolymers of isotactic polypropylene (iPP) with 4-methyl-1-pentene (iPP4MP) were prepared with a highly isoselective homogeneous organometallic catalyst in a range of 4-methyl-1-pentene (4MP) concentrations between about 1.7 and 14 mol %. Crystallization from the melt at different crystallizations temperatures have been performed to study the effect of 4MP comonomeric units excluded from the crystals on the crystallization of α and γ forms. All samples crystallize in mixtures of α and γ forms, and for each sample, the fraction of γ form increases with increasing crystallization temperature to achieve a maximum value fγ(max), which depends on the 4MP concentration. Compared to the homopolymer, the maximum fractional amount of γ form fγ(max) rapidly increases with increasing 4MP content achieving the highest value of 92% at low 4MP concentration of 2.2 mol %, and decreases with a further increase of 4MP concentration. These data are compared with analogous data of the maximum amount of γ form that develops in copolymers of iPP with ethylene and butene. This allows comparing the different effects of rejection of defects from the crystals, which produces interruption of the regular propene sequences and shortening of the length of the crystallizable sequences, the inclusion of defects into crystals of α and γ forms, and the effect of the crystallization kinetics. Since 4MP comonomeric units are excluded from the crystals, the behavior of iPP4MP copolymers provides the sole interruption effect, which is highly efficient and produces the highest amount of γ form of 92% at low 4MP concentration of nearly 2 mol %. The observed decrease of fγ(max) at higher 4MP concentrations is due to the too slow crystallization rate of the γ form at these 4MP contents that induces the crystallization of the kinetically favored α form. In fact, crystals of γ forms that develop in these copolymers are highly defective and show melting temperatures lower than those of the α form and, therefore, experience low undercooling at high crystallization temperatures. These results demonstrate that in metallocene iPP copolymers containing a significant amount of constitutional defects, the crystallization of the γ form is favored because of the short regular propene sequences, whereas the crystallization of the α form is always kinetically favored.

Encrypted peptides have been recently found in the human proteome and represent a potential class of antibiotics. Here we report three peptides derived from the human apolipoprotein B (residues 887–922) that exhibited potent antimicrobial activity against drug-resistant Klebsiella pneumoniae, Acinetobacter baumannii, and Staphylococciboth in vitroand in an animal model. The peptides had excellent cytotoxicity profiles, targeted bacteria by depolarizing and permeabilizing their cytoplasmic membrane, inhibited biofilms, and displayed anti-inflammatory properties. Importantly, the peptides, when used in combination, potentiated the activity of conventional antibiotics against bacteria and did not select for bacterial resistance. To ensure translatability of these molecules, a protease resistant retro-inverso variant of the lead encrypted peptide was synthesized and demonstrated anti-infective activity in a preclinical mouse model. Our results provide a link between human plasma and innate immunity and point to the blood as a source of much-needed antimicrobials.

The structure and morphology of samples of syndiotactic polypropylene (sPP) having different stereoregularity with concentration of rrrrpentads from 78 to 95.8%, crystallized by quenching the melt to 0 °C, is analyzed by wide-angle X-ray scattering and atomic force microscopy. The fast cooling from the melt induces the formation of nanocrystals of the trans-planar mesomorphic form of sPP resulting in a morphology characterized by the presence of globular entities (nodules) and absence of higher-order superstructures. It is shown that the nodule sizes depend on the stereoregularity of the sPP samples and the permanence time at 0 °C. The observed nodular morphology is completely different from the lamellar morphology typically obtained in sPP samples melt-crystallized at a lower cooling rate. This result indicates that crystals of different shape, size, and higher-order organization can be generated by changing the crystallization pathway.