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ABSTRACT: This paper describes the synthesis, crystal
structure, and physicomechanical properties of a biobased
polyester prepared from 2,5-furandicarboxylic acid (FDCA) and
1,4-butanediol. Melt-polycondensation experiments were conducted
by a two-stage polymerization using titanium tetraisopropoxide
(Ti[OiPr]4) as a catalyst. Polymerization conditions
(catalyst concentration, reaction time and second stage reaction
temperature) were varied to optimize poly(butylene-FDCA),
PBF, and molecular weight. A series of PBFs with different Mw
were characterized by DSC, TGA, DMTA, X-ray diffraction and
tensile testing. Influence of molecular weight and melting/
crystallization enthalpy on PBF material tensile properties was
explored. Cold-drawing tensile tests at room temperature for PBF
with Mw 16K to 27K showed a brittle-to-ductile transition. When Mw reaches 38K, the Young modulus of PBF remains above
900 MPa, and the elongation at break increases to above 1000%. The mechanical properties, thermal properties and crystal
structures of PBF were similar to petroleum derived poly(butylenes-terephthalate), PBT. Fiber diagrams of uniaxially stretched
PBF films were collected, indexed, and the unit cell was determined as triclinic (a = 4.78(3) Å, b = 6.03(5) Å, c = 12.3(1) Å, α =
110.1(2)°, β = 121.1(3)°, γ = 100.6(2)°). A crystal structure was derived from this data and final atomic coordinates are reported.
We concluded that there is a close similarity of the PBF structure to PBT α- and β-forms.
Macromolecules 01/2013; 46:796. · 5.17 Impact Factor
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ABSTRACT: A novel semiconducting benzothiadiazole (BTZ)-thiophene (T) co-oligomer having an unprecedented BTZ-T alternated motif has been synthesized and self-assembled into micrometer sized fibers by simple solution processing. The electrical properties of these low-dimensional architectures have been characterized by integrating them in an organic field-effect transistor.
Chemical Communications 10/2012; · 6.17 Impact Factor
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ABSTRACT: Reproducible spatial control of a self-assembly process of fiber- forming oligothiophenes was achieved by using confinement effects. This strategy allowed the direct integration with a precise control over density, orientation, and size of supramolecular semiconducting fibers in OFET devices, demonstrating that well-aligned fibers exhibit a substantial enhancement of electrical performances.
Journal of Materials Chemistry 08/2012; 22:20852. · 5.97 Impact Factor
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ABSTRACT: This study demonstrates that octacalcium phosphate (OCP) is a suitable substrate for alendronate local action towards bone cells. The results of the structural, spectroscopic, and microscopic investigation show that soaking OCP into alendronate solutions provoked the deposition of long crystalline rod-shaped formations, most likely a calcium alendronate complex, onto the calcium phosphate. The amount of alendronate loaded onto OCP increased as a function of the bisphosphonate concentration in solution. Osteoblast and osteoclast response was tested in single and in co-cultures on OCP containing 6.4wt.% AL (OCP-AL), and for comparison on hydroxyapatite (HA) containing a similar amount (5.9wt.%) of AL (HA-AL), as well as on pure OCP and HA as reference materials. Alendronate loaded materials displayed a beneficial effect on osteoblast activity and differentiation, whereas they inhibited osteoclast proliferation and differentiation. Crosstalking between osteoblast-like MG63 cells and human osteoclasts enhanced their response to alendronate. Moreover, OCP displayed a greater stimulating effect than HA on osteoblast differentiation, and AL promotion of osteoblast differentiation and mineralization was enhanced in OCP-AL with respect to HA-AL.
Bone 08/2012; 51(5):944-52. · 4.02 Impact Factor
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ABSTRACT: We describe the expedient synthesis of regioregular thiophene hexadecamers head-to-head (hh) substituted with hexyl and hexylthio grous. The synthesis was carried out by means of a sequence of ultrasound-assisted selective monobrominations and microwave-assisted Suzuki reactions using 4,4,5,5-tetramethyl-1,3,2-dioxaborolane in THF:water. The hexadecamers, which are very soluble in organic solvents, were investigated in solution and thin film by a variety of techniques (UV, PL, CV, X-ray diffraction, FET charge mobility, SKFM) with the aim of elucidating the effect of the sulfur spacer on morphology and functional properties. We show that the sulfur spacer compensates for the decrease in π−π conjugation caused by the hh regiochemistry and that the λ max value and redox potentials of the S-alkyl-substituted hexadecamer are similar to those of head-to-tail substituted poly(3-hexylthiophene). Measurements in field effect transistor devices showed that the alkylthio-substituted hexadecamer is a p-type semiconductor while the alkyl-substituted counterpart in the same conditions is not electroactive. Scanning Kelvin force microscopy measurements showed that a blend of the alkylthio-substituted hexadecamer with PCBM displays photovoltaic behavior under illumination. In agreement with this, a bulk heterojunction cell fabricated employing the same blend displayed near 1.5% conversion efficiency without addition of additives or device optimization. ■ INTRODUCTION Considerable research effort is currently being devoted to the improvement of organic photovoltaic devices for their advantages in terms of solution processing, lightweight, flexibility, and low costs. In the past few years impressive improvements have been made, in particular in bulk heterojunction (BHJ) cells whith power conversion efficiences now attaining over 8%. 1−9,10a,b These impressive advances have been promoted by improved electron donor or acceptor functional materials, processing conditions, device engineering, and understanding of the structure−property relationship. Thiophene derivatives play a key role in the field, as either polymers or short oligomers, reaching remarkable power conversion efficiencies in BHJ as donors in blend with soluble fullerenes as acceptors. 1−9,10a,b In this framework and based on our previous experience on the synthesis and application of thiophene derivatives, 11a,b we started the search for new structural paradigms for thiophene oligomers and polymers for photovoltaic applications. The electronic properties as well as the morphology of conjugated materials are determined by their structural features, in particular their size and type and position of substituents. Therefore, syntheses leading to regioregularly substituted derivatives are required. We focused on synthetically accessible large-size thiophene oligomers, made of more than 10 thiophene rings, as they are likely to have properties similar to those of polydisperse polymers but being monodisperse compounds are by far more soluble and easier to reprepare with exactly the same characteristics. It is worth noting that very few regioregular
Macromolecules 01/2012; · 5.17 Impact Factor
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ABSTRACT: This study demonstrates that zoledronate containing hydroxyapatite nanocrystals (HA-ZOL) can be synthesized as a single crystalline phase up to a zoledronate content of about 7 wt% by direct synthesis in aqueous solution, at variance with what previously found for alendronate-hydroxyapatite nanocrystals (HA-AL). On increasing zoledronate incorporation, the length of the coherent crystalline domains and the crystal dimensions of hydroxyapatite decrease, whereas the specific surface area increases. Full profile fitting of the powder X-ray diffraction patterns does not indicate major structural modifications, but an increase of the hydroxyapatite unit cell, on increasing zoledronate content. These data, together with a structural similarity between hydroxyapatite and calcium zoledronate, suggest a preferential interaction between zoledronate and the hydroxyapatite faces parallel to the c-axis direction. Osteoblast-like MG-63 cells and human osteoclasts were cultured on HA-ZOL nanocrystals and as a comparison on HA-AL nanocrystals containing almost the same (about 7 wt%) bisphosphonate amount. The beneficial influence of bisphosphonates on osteoblast proliferation and differentiation is enhanced when the tests are performed in co-cultures. Similarly, the reduction of osteoclast proliferation and the increase of Caspase 3 production are dramatically enhanced in co-cultures, which highlight an even greater influence of HA-ZOL than HA-AL on osteoclast apoptosis.
Biomaterials 01/2012; 33(2):722-30. · 7.40 Impact Factor
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ABSTRACT: The design, synthesis and structure-property investigation of a new thienopyrrolyl dione substituted oligothiophene material showing reduced band gap energy, low lying LUMO energy level and ambipolar semiconducting behaviour is described.
Chemical Communications 09/2011; 47(43):11840-2. · 6.17 Impact Factor
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ABSTRACT: Functional supramolecular architectures for bottom-up organic nano- and microtechnology are a high priority research topic. We discovered a new recognition algorithm, resulting from the combination of thioalkyl substituents and head-to-head regiochemistry of substitution, to induce the spontaneous self-assembly of sulfur overrich octathiophenes into supramolecular crystalline fibers combining high charge mobility and intense fluorescence. The fibers were grown on various types of surfaces either as superhelices or straight rods depending on molecular structure. Helical fibers directly grown on a field effect transistor displayed efficient charge mobility and intrinsic 'memory effect'. Despite the fact that the oligomers did not have chirality centers, one type of hand-helicity was always predominant in helical fibers, due to the interplay of molecular atropisomerism and supramolecular helicity induced by terminal substituents. Finally, we found that the new sulfur overrich oligothiophenes can easily be prepared in high yields through ultrasound and microwave assistance in green conditions.
Journal of the American Chemical Society 06/2011; 133(22):8654-61. · 9.91 Impact Factor
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ABSTRACT: We present a novel approach for detecting and visualizing graphene oxide (GO) with high contrast on different substrates, including glass, quartz, and silicon. Visualization of GO sheets is accomplished through quenching the fluorescence of a thiophene dye, giving high optical contrast without the need to use interference methods. A comparison of fluorescence, AFM, and XRD measurements confirmed that even a single GO sheet can completely quench the fluorescence and thus be quickly visualized.
Journal of the American Chemical Society 10/2009; 131(43):15576-7. · 9.91 Impact Factor
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ABSTRACT: The shed epidermis (molt) of snakes comprises four distinct layers. The upper two layers, here considered as beta-layer, contain essentially beta-keratin. The following layer, known as mesos-layer, is similar to the human stratum corneum, and is formed by thin cells surrounded by intercellular lipids. The latter layer mainly contains alpha-keratin. In this study, the molecular assemblies of proteins and lipids contained in these layers have been analyzed in the scale of two species of snakes, the elapid Tiger snake (TS, Notechis scutatus) and the viperid Gabon viper (GV, Bitis gabonica). Scanning X-ray micro-diffraction, FTIR and Raman spectroscopies, thermal analysis, and scanning electron microscopy experiments confirm the presence of the three layers in the GV skin scale. Conversely, in the TS molt a typical alpha-keratin layer appears to be absent. In the latter, experimental data suggest the presence of two domains similar to those found in the lipid intercellular matrix of stratum corneum. X-ray diffraction data also allow to determine the relative orientation of keratins and lipids. The keratin fibrils are randomly oriented inside the layers parallel to the surface of scales while the lipids are organized in lamellar structures having aliphatic chains normal to the scale surface. The high ordered lipid organization in the mature mesos layer probably increases its effectiveness in limiting water-loss.
Biopolymers 04/2009; 91(12):1172-81. · 2.87 Impact Factor
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ABSTRACT: Cadmium substituted strontium hydroxy- and fluoro-apatites, Sr(10−x)Cdx(PO4)6Y2 (Y = OH and F), have been prepared as single phases in the 0 ≤ x ≤ 4 interval for the former and 0 ≤ x ≤ 6 for the latter compound, respectively. The refinements of the X-ray full powder patterns allowed the structure determination of nine samples, and showed a preference of cadmium atoms for the M(1) site in fluoroapatite samples. IR investigation gave information about the nature of the metal oxygen interactions. The obtained results are used for a comparative discussion about the factors which drive the mutual substitution of Ca, Sr, Cd and Pb in apatites. The important role of electronegativity and polarisability, as well as of ionic radii, is evidenced.
Materials Research Bulletin. 03/2009; 44(3):522-530.
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ABSTRACT: DPY and DPE alkylenesulfanyl-bridged bithienyls were prepared by a highly effective ring-closing reaction via arylalkylsulfonium intermediate and used as inner cores in oligothiophenes. HOMO-LUMO energy levels, conformational flexibility, and intrinsic asymmetry of the cores are reflected in the electronic, film-forming, and thermal properties of the corresponding oligomers.
Organic Letters 10/2008; 10(17):3665-8. · 5.86 Impact Factor
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ABSTRACT: Structural complexity inherited from a microbial synthesis of glycolipids was translated into unique poly(sophorolipid) biomaterials. ROMP polymerization of natural diacetylated lactonic sophorolipids gave a high molecular weight polymer with asymmetric bola-amphiphilic repeating units. The poly(sophorolipid) chain alternates C18 oleic-like aliphatic segments (90% cis-configured double bonds) with bulky diacetylated disaccharide moieties. The solid-state properties were investigated by means of TGA, DSC, TMDSC, and variable-temperature X-ray diffraction. The poly(sophorolipid) is a solid at room temperature that undergoes the glass transition at 61 °C and melts at 123 °C. The crystal phase is associated with ordered packing of the aliphatic chain segments. The semicrystalline poly(sophorolipid) also displays a long-range order (d = 2.44 nm) involving sophorose groups that is found to persist after crystal phase melting (in high-T diffractograms) with a slightly shortened distance (2.27 nm). Upon annealing at 80 °C the poly(sophorolipid) recrystallizes and concomitantly the disaccharide units space out again at 2.44 nm. An exothermal phenomenon that immediately follows melting and is revealed by TMDSC might be associated with the observed adjustment of sophorose units spacing in the melt. The peculiar structural organization of this novel biomaterial is discussed.
09/2008;
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ABSTRACT: The direct synthesis of hydroxyapatite in the presence of bisphosphonates is quite difficult due to the great affinity for calcium of these compounds, which are widely used in the treatment of pathologies related to bone loss. We recently developed a new method which allowed to synthesize alendronate-hydroxyapatite composite nanocrystals with a bisphosphonate content up to about 7 wt%. Herein we report the results of an in vitro study aimed to investigate the effects of alendronate incorporation into hydroxyapatite on bone cells response. Osteoblast-like MG63 cells and human osteoclasts were cultured on nanocrystals at different alendronate content (3.9, 6.2, 7.1 wt%). MG63 cells cultured on the composite nanocrystals display normal morphology, good proliferation and increased values of the differentiation parameters. In particular, when cultured on composites at relatively high alendronate contents, osteoblasts display increased values of alkaline phosphatase activity (ALP), collagen type I, and osteocalcin production, as well as significant decrease of matrix metalloproteinases (MMP-1 and MMP-13) production, with respect both to the control and to pure hydroxyapatite nanocrystals. It follows that the presence of alendronate enhances osteoblast activation and extracellular matrix mineralization processes, without any abnormal collagen degradation. The osteoclast number on the composite nanocrystals decrease indicating that the bisphosphonate exerts its inhibitory effect on osteoclast proliferation even when incorporated into hydroxyapatite.
Biomaterials 04/2008; 29(7):790-6. · 7.40 Impact Factor
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ABSTRACT: A soluble, low-weight fraction of poly(alpha-vinyl,omega-n-hexyl-quaterthiophene), PT4Hex, having n-hexylquaterthiophenes as side-chain groups, is prepared by free-radical polymerization of alpha-vinyl,omega-n-hexyl-quaterthiophene and the corresponding properties compared to those of free di-n-hexylquaterthiophene (T4Hex). Optical analysis (absorption and emission) and X-ray diffraction data indicate that in the polyvinyl-locked architecture the quaterthiophene pendants adopt a cofacial arrangement with a mutual distance close enough for pi-pi orbitals to overlap ( approximately 4 A). As a consequence of the close chain packing, a shift of the reduction potential of about 0.5 V toward less negative values with respect to free T4Hex, is found for PT4Hex films. Due to its enhanced electron affinity, PT4Hex displays an electron-acceptor behavior when blended with alkylated and silylated quaterthiophenes acting as donors.
ChemPhysChem 01/2008; 8(18):2621-6. · 3.41 Impact Factor
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ABSTRACT: The design, synthesis and properties of liquid-crystalline semiconducting oligothiophenes containing dithienothiophene (DTT), benzothiadiazole (BTZ) and carbazole (CBZ) rigid cores are described. The effect of molecular structure (shape, size and substitution) on their thermal behaviour and electrical properties has been investigated. Polarised optical microscopy (POM) and differential scanning calorimetry (DSC) analyses have revealed highly ordered smectic mesophases for most of the newly synthesised compounds. X-ray diffraction (XRD) studies performed at various temperatures have shown that the smectic order is retained in the crystalline state upon cooling across the transition temperature, affording cast films with a more favourable morphology for FET applications.
Chemistry 02/2007; 13(36):10046-54. · 5.93 Impact Factor
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ABSTRACT: Novel model block copolymers of (R,S)--butyrolactone with pivalolactone (PVL) are prepared in order to define the effect of crystalline domains provided by poly(pivalolactone) on the biodegradability of atactic poly(-butyrolactone), a-PHB. The “living” a-PHB is synthesized from racemic â-butyrolactone, in the presence of potassium alkoxide/18-crown-6 complex, and such a living polymer is applied for polymerization of PVL, yielding block copolymers, a-PHB-b-PPVL, of tailored molecular weight and composition. The copolymers contain an amorphous phase with Tg ) 5 °C, associated with the a-PHB block, and a high melting crystalline phase, whose amount increases with PPVL content. Films of copolymers containing 9 (PVL9), 17 (PVL17), and 23 mol % of PPVL (PVL23) are exposed to PHB-depolymerase A from Pseudomonas lemoignei (37 °C, Tris-HCl buffer pH = 8). While plain a-PHB does not biodegrade, the biodegradation rate of a-PHB-b-PPVL copolymers increases (PVL9 , PVL17 <PVL23) along with the increase of crystalline PPVL domains. The biodegradation rate of PVL23 is similar to that of natural (crystalline) PHB. On the basis of a comparison of a-PHB-b-PPVL composition changes (by 1H NMR) with weight loss during biodegradation experiments, it is concluded that in the copolymers studied only the a-PHB block is attacked by the enzyme and that the crystalline block of nonbiodegradable PPVL efficiently promotes enzymatic attack to a-PHB, by providing a binding support to the enzyme.
Macromolecules 01/2007; 30(25):7743-7748. · 5.17 Impact Factor
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Berichte der deutschen chemischen Gesellschaft 10/2006; 2006(23):4821 - 4826. · 2.94 Impact Factor
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ABSTRACT: The direct synthesis of hydroxyapatite (HA)-aspartic acid (ASP) and HA-glutamic acid (GLU) nanocrystals was carried out in presence of different amounts of the amino acids in solution. ASP and GLU incorporation into HA crystals reduces the coherent length of the perfect crystalline domains along the long dimension (002) and, even more, along the cross section (310) of the apatite crystals, suggesting a specific interaction of the amino acids with the HA structure. FTIR analysis indicates that the carboxylic groups of the acidic amino acids interact with the calcium ions of HA. The relative amount of ASP incorporation into HA nanocrystals is greater than that of GLU, suggesting a greater affinity of ASP for HA. Osteoblast-like, MG63, cells cultured on the composite nanocrystals display good proliferation and increased values of ALP activity, collagen type I, TGF-betaI and osteocalcin production, indicating that the presence of the acidic amino acids enhances osteoblast activation and extra-cellular matrix mineralization processes.
Biomaterials 10/2006; 27(25):4428-33. · 7.40 Impact Factor
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Manuela Melucci,
Giovanna Barbarella, Massimo Gazzano,
Massimiliano Cavallini,
Fabio Biscarini,
Alessandro Bongini,
Fabio Piccinelli,
Magda Monari,
Marco Bandini,
Achille Umani-Ronchi,
Paolo Biscarini
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ABSTRACT: A new class of chiral oligothiophenes is described. Mono-, bi-, ter-, and quarterthiophenes have been linked to enantiopure trans-1,2-cyclohexanediamine (DACH) via diamino or diimino moieties. The stereochemistry of DACH, the type of linker, and oligothiophene size determine the conformational flexibility of these molecules and consequently their molecular and supramolecular helicity in solution and in the solid state. The case of diaminobis(bithiophene), which inverts helicity and shows chiral amplification in the transition from solution to film, is described in detail. Based on the combined use of circular dichroism in solution and in the solid state, single-crystal/thin-film X-ray diffraction, and polarized optical microscopy, a working mechanism has been proposed to explain this unexpected behavior.
Chemistry 10/2006; 12(28):7305-12. · 5.93 Impact Factor
