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Mechanotransduction is a molecular process by which cells translate physical stimuli exerted by the external environment into biochemical pathways to orchestrate the cellular shape and function. Even with the advancements in the field, the molecular events leading to the signal cascade are still unclear. The current biotechnology of tissue engineering offers the opportunity to study in vitro the effect of the physical stimuli exerted by biomaterial on stem cells and the mechanotransduction pathway involved in the process. Here, we cultured multipotent human mesenchymal/stromal cells (hMSCs) isolated from bone marrow (hBM-MSCs) and adipose tissue (hASCs) on films of poly(butylene 1,4-cyclohexane dicarboxylate) (PBCE) and a PBCE-based copolymer containing 50 mol% of butylene diglycolate co-units (BDG50), to intentionally tune the surface hydrophilicity and the stiffness (PBCE = 560 Mpa; BDG50 = 94 MPa). We demonstrated the activated distinctive mechanotransduction pathways, resulting in the acquisition of an elongated shape in hBM-MSCs on the BDG50 film and in maintaining the canonical morphology on the PBCE film. Notably, hASCs acquired a new, elongated morphology on both the PBCE and BDG50 films. We found that these events were mainly due to the differences in the expression of Cofilin1, Vimentin, Filamin A, and Talin, which established highly sensitive machinery by which, rather than hASCs, hBM-MSCs distinguished PBCE from BDG50 films.

Poly(butylene succinate) (PBS) and poly(butylene/2-butyl,2-ethyl-propylene succinate) (PBSBEPS) membranes are prepared by electrospinning technique. In recent years, interest in biodegradable aliphatic polyesters, including PBS and its copolymers, is increasing as they have potential applications in various sectors such as mulching films, food packaging, tissue engineering, and drug delivery. In this work, the synthesized polymers are dissolved in different solvents, namely acetone, chloroform (CHCl3), methanol, dichloromethane (DCM), and dimethylformamide in order to obtain the best solvent system. These solutions are then electrospun at room temperature to produce micron-sized fibers. The variables examined in determining the optimal solution and electrospinning conditions are the solvent system used, the concentration of PBS and PBS-based random copolymer, applied voltage, flow rate, humidity, and the distance between the needle tip and the collector, all of which have a meaningful effect on the fiber morphology. Among the various solvents used, the DCM and the less toxic CHCl3 result in fewer bead defects among fibers. Besides, an increase in PBS and PBS-based random copolymer concentration determines the reduction of bead defects, which from 12 to 14wt% results in bead-free uniform fibers, when suitable processing parameters are set. Promising results, which can pave the way for the production of membranes loaded with appropriate anticancer molecules for targeted biomedical applications, are obtained.

High-molecular-weight poly(butylene 2,4-furanoate) (2,4-PBF), an isomer of well-known poly(butylene 2,5-furanoate) (2,5-PBF), was synthesized through an eco-friendly solvent-free polycondensation process and processed in the form of an amorphous film by compression molding. Molecular characterization was carried out by NMR spectroscopy and GPC analysis, confirming the chemical structure and high polymerization degree. Thermal analyses evidenced a reduction of both glass-to-rubber transition and melting temperatures, as well as a detriment of crystallization capability, for 2,4-PBF with respect to 2,5-PBF. Nevertheless, it was possible to induce crystal phase formation by annealing treatment. Wide-angle X-ray scattering revealed that the crystal lattices developed in the two isomers are distinct from each other. The different isomerism affects also the thermal stability, being 2,4-PBF more thermally inert than 2,5-PBF. Functional properties, such as wettability, mechanical response, and gas barrier capability, were tested on both amorphous and semicrystalline 2,4-PBF films and compared with those of 2,5-PBF. Reduced hydrophilicity was determined for 2,4-isomer, in line with its lower average dipole moment, suggesting better chemical resistance to hydrolysis. Stress–strain tests have evidenced the higher flexibility and toughness of 2,4-PBF with respect to those of 2,5-PBF and the possibility of improving its mechanical resistance by annealing. Finally, the different isomerism deeply affects the gas barrier performance, being the O2- and CO2-transmission rates of 2,4-PBF 50 and 110 times lower, respectively, than those of 2,5-PBF. The gas barrier properties turned out to be outstanding under a dry atmosphere as well as in humid conditions, suggesting the presence of interchain hydrogen bonds. The gas blocking capability decreases after annealing because of the presence of disclination associated with the formation of crystals., Poly(butylene 2,4-furanoate) was obtained from 2,4-isomer of biobased furandicarboxylic acid, and isomerism further improved the key properties for sustainable packaging applications.

This works aims to investigate the effect of the molecular groups found in polyester backbones (type of ring in the acidic subunit and length of the glycolic subunit) on the molecular dynamics. The investigation is done on three furan-based polyesters (PEF, PPF and PBF) as compared to their terephthalic counterparts (PET, PTT, and PBT) after full quenching from the molten state. The segmental molecular dynamics is investigated with MT-DSC, FSC and DRS. It is shown that the cooperativity decreases as the length of the glycolic subunit increases in both furan-based and terephthalic polyesters. No direct correlation between the fragility index and the cooperativity is observed in furan-based polyesters containing glycolic subunits of different lengths. The differences in the isochoric fragilities obtained for the furan-based polyesters and their terephthalic counterparts has been assumed to result from the combination of backbone flexibility and packing efficiency of the macromolecular chains in the amorphous phase.

Highly promising fully biobased random copolyesters, poly(trimethylene 2,5-furandicarboxylate-co-trimethylene sebacate) (PTFcoPTSeb), were synthesized by using bio derived 1,3-propanediol, dimethyl ester of 2,5- furandicarboxylic acid, and sebacic acid, through eco-friendly polycondensation in the melt. Copolymers with high molecular weight containing 5, 15, 25 mol % of PTSeb were obtained, and their chemical structure confirmed by 1H NMR and FTIR spectroscopy. The thermal, tensile and gas barrier properties and composability were studied in relation to the copolymer supramolecular structure. As expected, introduction of PTSeb co-units results in lowering of glass transition temperature of copolymers and improves their flexibility. Besides, all copolymers showed outstanding gas barrier properties to O2 and CO2, with copolymer containing 15 mol % of PTSeb showing exceptional gas barrier properties, better than those of PTF and comparable to those of EVOH, currently used in multilayer packaging films. The same copolymer exhibited temperature induced shape memory behaviour. It was found that low amounts (15-25 mol %) of PTSeb in copolymer significantly modifies PTF thermal, mechanical and barrier properties and renders the final material compostable. Copolyesters containing 15 and 25 mol % of PTSeb can compete in some applications with commercially available compostable Ecoflex® polymer, but with markedly improved barrier properties.

Considering the current context of research aiming at proposing new bioplastics with low costs and properties similar to fossil-based commodities currently on the market, in the present work, a hybrid blend containing a prevalent amount of cheap inedible cereal flour (70 wt %) and poly(butylene succinate) (PBS) (30 wt %) has been prepared by a simple, eco-friendly, and low-cost processing methodology. In order to improve the interfacial tension and enhance the adhesion between the different phases at the solid state, with consequent improvement in microstructure uniformity and in material mechanical and adhesive performance, the PBS fraction in the blend was replaced with variable amounts (0-25 wt %) of PBS-based green copolymer, which exerted the function of a compatibilizer. The copolymer is characterized by an ad hoc chemical structure, containing six-carbon aliphatic rings, also present in the flour starch structure. The two synthetic polyesters obtained through two-stage melt polycondensation have been deeply characterized from the molecular, thermal, and mechanical points of view. Copolymerization deeply impacts the polymer final properties, the crystallizing ability, and stiffness of the PBS homopolymer being reduced. Also, the prepared ternary blends were deeply investigated in terms of microstructure, thermal, and mechanical properties. Lastly, both pure blend components and ternary blends were subjected to disintegration experiments under composting conditions. The results obtained proved how effective was the compatibilizer action of the copolymer, as evidenced by the investigation conducted on morphology and mechanical properties. Specifically, the mixtures with 15 and 20 wt % Co appeared to be characterized by the best mechanical performance, showing a progressive increase of deformation while preserving good values of elastic modulus and stress. The disintegration rate in compost was found to be higher for the lower amount of copolymer in the ternary blend. However, after 90 days of incubation, the blend richest in copolymer content lost 62% of weight.

In the present study, 100% bio-based polyesters of 2,5-thiophenedicarboxylic acid were synthesized via two-stage melt polycondensation using glycols containing 3 to 6 methylene groups. The so-prepared samples were characterised from the molecular point of view and processed into free-standing thin films. Afterward, both the purified powders and the films were subjected to structural and thermal characterisation. In the case of thin films, mechanical response and barrier properties to O2 and CO2 were also evaluated. From the results obtained, it emerged that the length of glycolic sub-units is an effective tool to modulate the chain mobility and, in turn, the kind and amount of ordered phases developed in the samples. In addition to the usual amorphous and 3D crystalline phases, in all the samples investigated it was possible to evidence a further phase characterised by a lower degree of order (mesophase) than the crystalline one, whose amount is strictly related to the glycol sub-unit length. The relative fraction of all these phases is responsible for the different mechanical and barrier performances. Last, but not least, a comparison between thiophene-based homopolymers and their furan-based homologues was carried out.

Among the several actions contributing to the development of a sustainable society, there is the eco-design of new plastic materials with zero environmental impact but that are possibly characterized by properties comparable to those of the traditional fossil-based plastics. This action is particularly urgent for food packaging sector, which involves large volumes of plastic products that quickly become waste. This work aims to contribute to the achievement of this important goal, proposing new bio-based cycloaliphatic polymers based on trans-1,4-cyclohexanedicarboxylic acid and containing different amount of camphoric acid (from 0 to 15 mol %), a cheap and bio-based building block. Such chemical modification was conducted in the melt by avoiding the use of solvents. The so-obtained polymers were processed in the form of films by compression molding. Afterwards, the new and successfully synthesized random copolymers were characterized by molecular (NMR spectroscopy and GPC analysis), thermal (DSC and TGA analyses), diffractometric (wide angle X-ray scattering), mechanical (through tensile tests), and O2 and CO2 barrier point of view together with the parent homopolymer. The article aims to relate the results obtained with the amount of camphoric moiety introduced and to present, the different microstructure in the copolymers in more detail, indeed, in these samples, a different crystalline form developed (the so-called β-PBCE). This latter form was the kinetically favored and less packed one, as proven by the lower equilibrium melting temperature determined for the first time by Baur’s equation.

Sarcopenia caused by ageing and muscle loss is mostly found in the elderly people. Since a number of older people have been increased, a device which assists with grasping can play an important role in an ageing society. The purpose of this research is to select the material which is potentially a part of soft robotic actuator. Natural rubber (NR) latex produced locally in Thailand is intentionally chosen and chemically vulcanized by using a conventional vulcanization system into a molded fingered foam. The research focuses on varying the amount of foaming agent (Benzene sulfonyl hydrazide, BSH). Effect of foaming agent quantity on morphology and dynamic properties of the prepared natural rubber foam was elucidated. The suitable foam formula is selected and molded as the human fingers in the structure of a potential soft robotic actuator which were tested for the movement.

Here, solution-cast blends of polylactic acid (PLA) and a novel bioderived poly(pentamethylene 2,5-furanoate) (PPeF) in variable concentrations (1-50 wt %) are prepared and investigated. The characterization of the thin films (thickness 50 mu m) highlights that PPeF strongly improves the UV-shielding properties of PLA, with a decrease in transmittance at 275 nm from 47.3% of neat PLA to 0.77% with only 1 wt % of PPeF, while the transmittance decrease in the visible region at these PPeF fractions is marginal, allowing the production of optically transparent films. Despite the complete immiscibility of PLA/PPeF blends, PPeF effectively enhances the ductility of PLA as the tensile strain at break increases from 7% of neat PLA to 200% of the blend with 30 wt % of PPeF. This composition is the most promising also from the gas-barrier point of view as the gas transmission rates of CO2 and O-2 drop to one-fourth of those of neat PLA, comparable to those of poly(ethylene terephthalate). These results highlight that PLA/PPeF blends with PPeF fractions of 30 wt % are very promising for food packaging applications, and their properties could be further enhanced by applying suitable compatibilizers.

In the field of artificial prostheses for damaged vessel replacement, polymeric scaffolds showing the right combination of mechanical performance, biocompatibility, and biodegradability are still demanded. In the present work, poly(butylene-co-triethylene trans-1,4-cyclohexanedicarboxylate), a biodegradable random aliphatic copolyester, has been synthesized and electrospun in form of aligned and random fibers properly designed for vascular applications. The obtained materials were analyzed through tensile and dynamic-mechanical tests, the latter performed under conditions simulating the mechanical contraction of vascular tissue. Furthermore, the in vitro biological characterization, in terms of hemocompatibility and cytocompatibility in static and dynamic conditions, was also carried out. The mechanical properties of the investigated scaffolds fit within the range of physiological properties for medium- and small-caliber blood vessels, and the aligned scaffolds displayed a strain-stiffening behavior typical of the blood vessels. Furthermore, all the produced scaffolds showed constant storage and loss moduli in the investigated timeframe (24 h), demonstrating the stability of the scaffolds under the applied conditions of mechanical deformation. The biological characterization highlighted that the mats showed high hemocompatibility and low probability of thrombus formation, finally, the cytocompatibility tests demonstrated that cyclic stretch of electrospun fibers increased endothelial cell activity and proliferation, in particular on aligned scaffolds.

We report on the molecular origin of poly(pentamethylene 2,5-furanoate) particular physical properties. From the structural point of view we found this polymer can develop crystallinity when stored at room conditions for months. On the other hand, we used broadband dielectric spectroscopy (BDS) measurements, to analyze in very detail the local and segmental molecular dynamics of the material subjected to several thermal treatments. In this way we evidenced that the molecular dynamics are sensitive to thermal history over a broad temperature range. This behavior has been attributed to possible inter-chain interactions detected via infrared spectroscopy and rheology measurements in the non-crystallized polymer.

In the present work, the effect of ether oxygen atom introduction in a furan ring-containing polymer has been evaluated. Solvent-free polycondensation process permitted the preparation of high molecular weight poly(diethylene 2,5-furandicarboxylate) (PDEF), by reacting the dimethyl ester of 2,5-furandicarboxylic acid with diethylene glycol. After molecular and thermal characterization, PDEF mechanical response and gas barrier properties to O2 and CO2, measured at different temperatures and humidity, were studied and compared with those of poly(butylene 2,5-furandicarboxylate) (PBF) and poly(pentamethylene 2,5-furanoate) (PPeF) previously determined. Both PDEF and PPeF films were amorphous, differently from PBF one. Glass transition temperature of PDEF (24 °C) is between those of PBF (39 °C) and PPeF (13 °C). As concerns mechanical response, PDEF is more flexible (elastic modulus [E] = 673 MPa) than PBF (E = 1290 MPa) but stiffer than PPeF (E = 9 MPa). Moreover, PDEF is the most thermally stable (temperature of maximum degradation rate being 418 for PDEF, 407 for PBF and 414 °C for PPeF) and hydrophilic (water contact angle being 74° for PDEF, 90° for PBF and 93° for PPeF), with gas barrier performances very similar to those of PPeF (O2 and CO2 transmission rate being 0.0022 and 0.0018 for PDEF and, 0.0016 and 0.0014 cm3 cm/m2 d atm for PPeF). Lab scale composting experiments indicated that PDEF and PPeF were compostable, the former degrading faster, in just one day. The results obtained are explained on the basis of the high electronegativity of ether oxygen atom with respect to the carbon one, and the consequent increase of dipoles along the macromolecule.

Polymer nanostructures were developed on fully bio-based poly(trimethylene furanoate) (PTF) films, by using the technique of Laser Induced Periodic Surface Structures (LIPSS). We found that irradiation times between 1 and 8 min allowed the formation of periodic and nanometric ripples, when using an UV pulsed laser source at a fluence of 8 mJ/cm2. The wrinkled surfaces were studied by a combined macro- and nanoscale approach. We evaluated possible physicochemical changes taking place on the polymer surface after irradiation by infrared spectroscopy, contact angle measurements and atomic force microscopy. The macroscopic properties of PTF showed almost no changes after nanostructure formation, differently from the results previously found for the terephthalic counterparts, as poly(ethylene terephthalate), PET, and poly(trimethylene terephthalate), PTT. At the nanoscale, the surface mechanical properties of the nanostructured PTF were found to be improved, as evidenced by force spectroscopy measurements. In particular, stiffer surfaces characterized by an increased Young's modulus were measured for the nanostructured sample., This work has been supported by Ministry of Science, Innovation and Universities (MCIU, Spain) under the project CTQ2016-75880-P. D.E.M. acknowledges the financial support obtained through the Post-Doctoral fellowship “Juan de la Cierva – Incorporación” (IJCI-2017-31600, MCIU, Spain). E.R. thanks MCIU for the tenure of a Ramón y Cajal contract (No. RYC-2011-08069).

Dye-sensitized photooxygenation reaction of bio-based double bond-containing substrates is proposed as sustainable functionalization of terpenes and terpenoids to transform them into polyoxygenated compounds to be employed for the synthesis of new bio-based polyesters. As proof of concept, citronellol 1 has been regioselectively converted into diol 4 using singlet oxygen (O-1(2)), a traceless reagent that can be generated from air, visible light and zeolite supported-photosensitizer (Thionine-NaY). With our synthetic approach, diol 4 has been obtained in two-steps, with good regioselectivity, using green reagents such as light and air, and finally a solvent-free oxidation step. From this compound, a citronellol-based copolyester of poly(butylene succinate) (PBS) has been synthesized and fully characterized. The results obtained evidence that the proposed copolymerization of PBS with the citronellol-based building blocks allows to obtain a more flexible and functionalizable material, by exploiting a largely available natural molecule modified through a green synthetic path.

In the recent years Broadband Dielectric Spectroscopy (BDS) has been shown to be a powerful technique to investigate crystallization in complex fluids including liquids and polymers. Particularly attractive is when scattering and diffraction experiments are combined with dielectric spectroscopy during crystallization in real-time. In this chapter we will review the application of BDS to the study of polymer crystallization emphasizing those aspects related to the combination of X-ray scattering techniques, rendering information about the crystalline phase, with BDS providing information about the amorphous phase dynamics. In addition, we will show as well that both the α-relaxation and the β-relaxation can be used for probing polymer crystallization especially when they appear simultaneously and well resolved in the experimental frequency window. Although most of the applications of BDS to polymer crystallization involve thermal treatments we will show that BDS can be also used when other magnitudes like pressure, shear or strain are involved in the crystallization process.

Thanks to the continuous progress of tissue engineering, the opportunity to overcome the main limits of traditional medicine is becoming more and more concrete. By a targeted study of biomaterials and their properties, it is possible to find ad hoc solutions for the fabrication of tissue engineered scaffolds. More in details, poly(butylene succinate) PBS is a biocompatible synthetic polymer already investigated for biomedical applications, but characterized by a high degree of crystallinity, which leads to long degradation times and mechanical properties often not suitable in the field of soft tissue engineering. In the present study, a PBS-based copolymer containing 30 mol% of dithiodipropionic co-units, P(BSBDTDP), was synthesized by two-step melt polycondensation. The comonomeric unit is characterized by the presence of -S-S- bond, potentially capable of improving both biocompatibility and biodegradability with respect to the homopolymer. After synthesis, 3D-mats and films were obtained by electrospinning and compression moulding, respectively, and then subjected to molecular, thermal and mechanical characterization. In addition, in view of a possible application in soft tissue engineering, enzymatic biodegradation studies and in vitro biocompatibility tests, using NIH-3T3 cell line, were also carried out. The results obtained show that through copolymerization solid-state properties could be nicely tailored. More in details, compared to PBS, P(BSBDTDP) is characterized by a lower crystallinity degree and mechanical properties typical of soft tissues, maintaining at the same time the good thermal stability of the parent homopolymer. In addition, copolymeric scaffold better supports cell adhesion and proliferation, undergoing degradation in biological environment slightly faster than its PBS homologous. (C) 2020 Elsevier Ltd. All rights reserved.

Herein, we present poly(butylene 1,4-cyclohexanedicarboxylate) (PBCE) films characterized by an unpatterned microstructure and a specific hydrophobicity, capable of boosting a drastic cytoskeleton architecture remodeling, culminating with the neuronal-like differentiation of human bone marrow-mesenchymal stem cells (hBM-MSCs). We have used two different filming procedures to prepare the films, solvent casting (PBCE) and compression-moulding (PBCE*). PBCE film had a rough and porous surface with spherulite-like aggregations (&Oslash, = 10&ndash, 20 &mu, m) and was characterized by a water contact angle = 100&deg, PBCE* showed a smooth and continuous surface without voids and visible spherulite-like aggregations and was more hydrophobic (WCA = 110&deg, ). Both surface characteristics were modulated through the copolymerization of different amounts of ether-oxygen-containing co-units into PBCE chemical structure. We showed that only the surface characteristics of PBCE-solvent-casted films steered hBM-MSCs toward a neuronal-like differentiation. hBM-MSCs lost their canonical mesenchymal morphology, acquired a neuronal polarized shape with a long cell protrusion (&ge, 150 &mu, m), expressed neuron-specific class III &beta, tubulin and microtubule-associated protein 2 neuronal markers, while nestin, a marker of uncommitted stem cells, was drastically silenced. These events were observed as early as 2-days after cell seeding. Of note, the phenomenon was totally absent on PBCE* film, as hBM-MSCs maintained the mesenchymal shape and behavior and did not express neuronal/glial markers.

11 pags., 7 figs., 4 tabs., In the present paper, four fully biobased homopolyesters of 2,5-furandicarboxylic acid (2,5-FDCA) with a high molecular weight have been successfully synthesized by two-stage melt polycondensation, starting from the dimethyl ester of 2,5-FDCA and glycols of different lengths (the number of methylene groups ranged from 3 to 6). The synthesized polyesters have been first subjected to an accurate molecular characterization by NMR and gel-permeation chromatography. Afterward, the samples have been successfully processed into free-standing thin films (thickness comprised between 150 to 180 μm) by compression molding. Such films have been characterized from the structural (by wide-angle X-ray scattering and small-angle X-ray scattering), thermal (by differential scanning calorimetry and thermogravimetric analysis), mechanical (by tensile test), and gas barrier (by permeability measurements) point of view. The glycol subunit length was revealed to be the key parameter in determining the kind and fraction of ordered phases developed by the sample during compression molding and subsequent cooling. After storage at room temperature for one month, only the homopolymers containing the glycol subunit with an even number of-CH2-groups (poly(butylene 2,5-furanoate) (PBF) and poly(hexamethylene 2,5-furanoate) (PHF)) were able to develop a three-dimensional ordered crystalline phase in addition to the amorphous one, the other two appearing completely amorphous (poly(propylene 2,5-furanoate (PPF) and poly(pentamethylene 2,5-furanoate) (PPeF)). From X-ray scattering experiments using synchrotron radiation, it was possible to evidence a third phase characterized by a lower degree of order (one-or two-dimensional), called a mesophase, in all the samples under study, its fraction being strictly related to the glycol subunit length: PPeF was found to be the sample with the highest fraction of mesophase followed by PHF. Such a mesophase, together with the amorphous and the eventually present crystalline phase, significantly impacted the mechanical and barrier properties, these last being particularly outstanding for PPeF, the polyester with the highest fraction of mesophase among those synthesized in the present work., G.G., M.S., N.L., and A.M. acknowledge the Italian Ministry of University and Research. This publication is based upon work from COST Action FUR4Sustain, CA18220, supported by COST (European Cooperation in Science and Technology).

Novel A-B-A triblock copolymers based on poly(L-lactic acid) (PLLA) were designed with an ad hoc chemical structure to prepare micro- and nanoparticles for controlled drug delivery. A block is formed by PLLA, while central B block is a copolymeric system based on poly(butylene succinate) and poly(triethylene succinate): more specifically, two copolymers with fix composition (50:50 mol:mol) and different molecular architecture were synthesized. One of them is characterized by a block architecture, i.e. long butylene succinate and triethylene succinate sequences form the macromolecular chains, the other being on the contrary a random copolymer with short sequences. The so-obtained materials were characterized from the molecular and thermal point of view. Moreover, to investigate the effect of both chemical structure and molecular architecture of the polymers synthesized on drug release kinetics, Dexamethasone-encapsulated micro- and nanoparticles were prepared by oil-in-water miniemulsion technique. These particles were subjected to thermal and morphological characterization. After that, drug release studies were carried out, and the effect of chemical composition, sequence distribution and particle size on release profile was evaluated. (C) 2020 Elsevier Ltd. All rights reserved.

The crystallization behavior of fully biobased poly(butylene isophthalate) (PBI) has been investigated using calorimetric and microscopic techniques. PBI is an extremely slow crystallizing polymer that leads, after melt-crystallization, to the formation of lamellar crystals and rather large spherulites, due to the low nuclei density. Based upon quantitative analysis of the crystal-nucleation behavior at low temperatures near the glass transition, using Tammann&rsquo, s two-stage nuclei development method, a nucleation pathway for an acceleration of the crystallization process and for tailoring the semicrystalline morphology is provided. Low-temperature annealing close to the glass transition temperature (Tg) leads to the formation of crystal nuclei, which grow to crystals at higher temperatures, and yield a much finer spherulitic superstructure, as obtained after direct melt-crystallization. Similarly to other slowly crystallizing polymers like poly(ethylene terephthalate) or poly(l-lactic acid), low-temperature crystal-nuclei formation at a timescale of hours/days is still too slow to allow non-spherulitic crystallization. The interplay between glass relaxation and crystal nucleation at temperatures slightly below Tg is discussed.

Poly(butylene 2,6-naphthalate) (PBN) is a crystallizable linear polyester containing a rigid naphthalene unit and flexible methylene spacer in the chemical repeat unit. Polymeric materials made of PBN exhibit excellent anti-abrasion and low friction properties, superior chemical resistance, and outstanding gas barrier characteristics. Many of the properties rely on the presence of crystals and the formation of a semicrystalline morphology. To develop specific crystal structures and morphologies during cooling the melt, precise information about the melt-crystallization process is required. This review article summarizes the current knowledge about the temperature-controlled crystal polymorphism of PBN. At rather low supercooling of the melt, with decreasing crystallization temperature, β’- and α-crystals grow directly from the melt and organize in largely different spherulitic superstructures. Formation of α-crystals at high supercooling may also proceed via intermediate formation of a transient monotropic liquid crystalline structure, then yielding a non-spherulitic semicrystalline morphology. Crystallization of PBN is rather fast since its suppression requires cooling the melt at a rate higher than 6000 K·s−1. For this reason, investigation of the two-step crystallization process at low temperatures requires application of sophisticated experimental tools. These include temperature-resolved X-ray scattering techniques using fast detectors and synchrotron-based X-rays and fast scanning chip calorimetry. Fast scanning chip calorimetry allows freezing the transient liquid-crystalline structure before its conversion into α-crystals, by fast cooling to below its glass transition temperature. Subsequent analysis using polarized-light optical microscopy reveals its texture and X-ray scattering confirms the smectic arrangement of the mesogens. The combination of a large variety of experimental techniques allows obtaining a complete picture about crystallization of PBN in the entire range of melt-supercoolings down to the glass transition, including quantitative data about the crystallization kinetics, semicrystalline morphologies at the micrometer length scale, as well as nanoscale X-ray structure information.

The peculiar reactivity of catechol carbonate (CC) with amines and polyamines in both solvent and catalyst free conditions is herein described. In all the tests performed at room temperature, CC conversion reached 100% in few seconds leading to the selective formation of the corresponding 2-hydroxyphenylcarbamate. This compound is furtherly rapidly converted to the di-substituted urea by the consecutive nucleophilic attack of another amine. Noteworthy, the application of this approach can be successfully extended to the one-pot bio-amine based synthesis of polyurea as herein proposed for the first time in literature. The reaction is of general purpose for primary amines and catechol can be easily recovered by sublimation as pure crystals ready to be recycled for the synthesis of new CC. An exception is related to the reactivity of secondary amine, which leads anyway to the selective formation of substituted phenolic carbamates (e.g. 2-hydroxyphenyl diethylcarbamate), suitable as intermediates in medicinal chemistry.