[Show abstract][Hide abstract] ABSTRACT: 2,3-Thieno(bis)imide (N) ended oligomers are emerging as valuable molecular materials for application in organic electronics. Here, we report the synthesis and characterization of three new 2,3-thieno(bis)imide ended oligothiophenes (T) bearing unsaturated ethylene (E), azomethine (I) and ethinyl (A) inner bridges (NTE, NTI and NTA respectively). The effect of the unsaturated bridge on the π-conjugation extent, molecular conformation and overall aromaticity is related to the functional optoelectronic and morphology properties and compared to the properties of the linear analogue (NTT) with a bithiophene inner moiety. Optical spectroscopy and cyclovoltammetry analysis show a strong red shift of the absorption and a decreased energy band gap on going from NTI to NTE to NTA. The HOMO level decreases in the order NTE>NTI>NTA. Moreover, while the LUMO of NTE and NTA have almost the same energy, NTI has a LUMO energy about 0.1 eV lower, likely due to the electron withdrawing effect of the azomethine moiety. Morphologic investigation of solution cast thin deposits shows that the unsaturated bridges promote the formation of concomitant polymorphs with simultaneous presence of microcrystals with different morphology and fluorescence properties. Moreover, irreversible conversion of one polymorph to the other was achieved by thermal treatments for NTA and NTE and by exploiting this feature we realized a time temperature integrator (TTI) device based on NTE material. This device allowed to monitor temperature evolutions in the range between RT and 200°C by means of a red to yellow fluorescence switch that was detectable by optical microscopy.
[Show abstract][Hide abstract] ABSTRACT: In this contribution a new class of aliphatic poly(butylene succinate) (PBS)-based poly(ester urethane)s has been synthesized and characterized from the molecular, thermal and mechanical point of view. Hydrolytic degradation studies under physiological conditions have been conducted to assess their biodegradation rate. To obtain copolymers showing both thermoplastic and elastomeric properties, the chain-linking strategy has been considered. In particular, two hydroxyl-terminated oligomers have been synthesized by melt polycondensation: poly(butylene succinate) (PBS), as “hard segment”, and two poly(butylene adipate/diglycolate) (P(BAmBDGn) random copolymers as “soft segment”. The introduction of ether-linkages along the PBA chain permitted to depress its crystallinity degree and to enhance the wettability. Multiblock copolymers were finally obtained by chain extending with hexamethylene diisocyanate each P(BAmBDGn) copolymer with two different mass percentages of PBS: 30% and 50%. All copolymers maintained good thermal stability and were characterized by melting temperatures above 100°C. Elastic modulus (E) and stress at break (σb) varied with the chemical composition: the higher the PBS amount, the higher E and σb. No yield and very high elongations at break were observed. Hydrolytic degradation studies highlighted an increase of the degradation rate with the increase of the BDG content.
Polymer Degradation and Stability 10/2014; · 2.77 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: In this study, we propose a new class of multiblock copolyesters containing butylene 1,4-cyclohexanedicarboxylate (BCE) and diethylene glycol 1,4-cyclohexanedicarboxylate (DGCE) sequences. The two parent homopolymers were prepared by the usual two-stage melt polycondensation. On the other hand, the multiblock copolyesters, characterized by the same chemical composition but different block lengths, were synthesized by reactive blending. Physicochemical characterization (DSC, WAXS, tensile tests, WCA, hydrolysis experiments) demonstrated that the block length controls the polymer crystallinity, the thermal and mechanical properties, the wettability and the degradation rate. The copolymers displayed different stiffnesses, mainly depending on the crystallinity degree and macromolecular chain flexibility, a tunable range of degradation rates, and different surface hydrophilicity. Biocompatibility assays showed the absence of potentially cytotoxic products released into the culture medium by the investigated samples, and demonstrated that our substrates support a physical environment where cells can adhere and proliferate, confirming their potential for biomedical applications.
[Show abstract][Hide abstract] ABSTRACT: Herein is described a multidisciplinary approach to understand the performance limitations of small molecule organic light emitting transistors (OLETs) based on a layered architecture, an innovative architecture potentially competitive with the state of the art and more flexible for spectral emission control. The processes of charge injection and field-effect transport at metal/organic and organic/organic interfaces are analysed using microscopic and spectroscopic techniques in coordination. Atomic force microscopy and ultrasonic force microscopy are employed to characterize the interface morphology and the initial growth stages of organic films where charge transport actually occurs. X-ray diffraction and near edge X-ray dichroic absorption with linearly polarised light allow to determine the unit cell packing and the molecular orientation at the active organic interfaces, as well as the amount of non-ordered domains. Moreover, chemical reactivity at the interfaces are measured by X-ray photoelectron spectroscopy. It is found that a strong reaction occurs at the metal-organic interfaces, with molecular fragmentation. Additionally, the transport properties strongly depend on the nature of the materials forming the organic stack. Specifically, amorphous conjugated films as bottom layers can promote an increased molecular disorder in the upper active layer, with a concomitant deterioration of the conduction properties.
[Show abstract][Hide abstract] ABSTRACT: The formation of gold nanoparticles (GNPs) within mesoporous silica matrices by means of irradiation
techniques is reported. The xerogels were impregnated with solutions of two different gold precursors:
(Ph3P)AuCl for Au(I) and [nBu4N]AuCl4 for Au(III). The irradiations were performed with two continuous
wave laser sources (266 and 532 nm), with a femtosecond pulsed laser (800 nm), and with a mercury
vapour lamp emitting in the UV region. It has been shown that no reducing agent was ever required to
obtain GNP formation. XRD data exhibited the typical patterns of fcc gold, except for two cases involving
the Au(I)-doped matrices, where a preferential crystallographic orientation was observed. Excluding the
case of the UV irradiations performed on Au(III)-doped samples, we always obtained the formation of
roughly spherical and well dispersed GNPs of relatively small size (6–60 nm). The gold-reduction
mechanisms proposed depend on the chosen irradiation technique. Moreover, when laser sources are
employed, GNP formation can be selectively limited to the irradiated areas, thus making it possible to
obtain reproducible patterns of GNPs.
[Show abstract][Hide abstract] ABSTRACT: Polymorphic crystalline microfibers from an achiral octithiophene with one S-hexyl substituent per ring are separately and reproducibly grown with the same characteristics on various solid surfaces, including the interdigitated electrodes/SiO2 surface of a bottomcontact field-effect transistor. The arrangement of the same molecule in two diverse supramolecular structures leads to markedly different electronic, optical, and charge mobility properties. The microfibers—straight and yellow emitting or helical and red emitting—exhibit p-type charge transport characteristics, with the yellow ones showing a charge mobility and on/off current ratio of one and three orders of magnitude, respectively, greater than the red ones. Both forms show circular dichroism signals with significant differences from one form to the other. DFT calculations show that the octithiophene exists in two different quasi-equienergetic conformations aggregating with diverse orientations of the substituents. This result suggests that the observed polymorphism is conformational in nature. The self-assembly, driven by sulfur–sulfur non-bonding interactions, amplifies the small property differences between conformers, leading to quite different bulk properties.
[Show abstract][Hide abstract] ABSTRACT: The variation of the drift mobility of positive and negative charge carriers in fi lms of anthracene-
containing poly( p -phenylene-ethynylene)- alt- poly( p -phenylene-vinylene)s ( AnE-PVs ),
differently substituted, is investigated as a function of the
applied electric fi eld. Branched 2-ethylhexyl and linear alkoxy
side chains of different lengths are considered, as well as
well-defi ned and random distributions of lateral substituents.
The same conditions are used both for the deposition of the
polymer fi lms and for their characterization, which allows for
the establishment of a clear relationship between the chemical
structure and the charge carrier mobility.
Macromolecular Chemistry and Physics 02/2014; · 2.39 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: The influence of the simultaneous presence of the two inhibitors of bone degradation, strontium and zoledronate, on the direct synthesis of hydroxyapatite was explored in the range of Sr concentration up to 50 atom% at two different bisphosphonate concentrations (ZOL7 and ZOL14). The results of structural analysis indicated that HA can be obtained as a single crystalline phase up to a Sr concentration in solution of 20 and 10 atom% within the ZOL7 and ZOL14 series respectively. Both Sr substitution and ZOL incorporation affect the length of the coherently scattering crystalline domains and the dimensions of HA nanocrystals. At greater Sr content, XRD full profile fitting data indicate that zoledronate provokes the segregation of Sr in two crystalline apatitic phases, at different strontium content. Co-cultures of osteoblast-like MG63 cells and human osteoclast show that ZOL displays a greater inhibitory influence than Sr on osteoclast proliferation and activity. On the other hand, the results obtained on osteoblast surnatant and on gene expression indicate that Sr exerts a greater promotion on osteoblast proliferation and differentiation. The co-presence of Sr and ZOL has a combined effect on the differentiation markers, so that HA containing about 4 wt% ZOL and 4 Sr atom%, and even more HA containing about 4 wt% ZOL and 8 Sr atom%, result the best compromise for osteoblast promotion and osteoclast inhibition.
[Show abstract][Hide abstract] ABSTRACT: A series of novel random copolymers of poly(butylene 1,4-cyclohexanedicarboxylate) (PBCE) containing triethylene glycol sub-unit (P(BCEmTECEn)) were synthesized and characterized in terms of molecular and solid-state properties, among these barrier properties to different gases (oxygen and carbon dioxide). In addition, biodegradability studies both in soil and in compost and ecotoxicological analysis, by means of the Lepidium sativum test, have been conducted.
The copolymers displayed a high and similar thermal stability with respect to PBCE. At room temperature, all the copolymers appeared as semicrystalline materials: the main effect of copolymerization was a lowering of crystallinity degree (χc) and a decrease of the melting temperature compared to the parent homopolymer. The Baur’s equation well described the Tm-composition data. Final properties and biodegradation rate of the materials under study were strictly dependent on copolymer composition and χc. As a matter of fact, hydrophilicity regularly increased with the increasing of TECE mol%, due to the PEG-like portion. The elastic modulus and the elongation to break decreased and increased, respectively, as TECE unit content was increased. As to the barrier properties, the selectivity ratios for the examined samples increased with the increasing of TECE mol%, confirming the correlation between the permeability and the chemical composition. The copolymers with lower TECE unit content (up to 30 mol%) showed improved barrier properties with respect to polylactide films tested under the same conditions.
Lastly, the biodegradation rate of P(BCEmTECEn) copolymers increased with the increasing of TECE mol%, while PBCE remained almost undegraded in the explored conditions.
Polymer Degradation and Stability 01/2014; · 2.77 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: The relationships between the molecular structure, packing modalities, charge mobility and light emission in organic thin films is a highly debated and controversial issue, with both fundamental and technological implications in the field of organic optoelectronics. Thieno(bis)imide (TBI) based molecular semiconductors provide an interesting combination of good processability, tunable self-assembly, ambipolar charge transport and electroluminescence, and are therefore an ideal test base for fundamental studies on the structure-property correlation in multifunctional molecular systems. Herein, we introduce a new class of thieno(bis)imide quaterthiophenes having alkyl side chains of different shapes (linear, cyclic, branched) and lengths (C1-C8). We found that contrarily to what is generally observed in most molecular semiconductors, the length of the alkyl substituent does not affect the optical, self-assembly and charge transport properties of TBI materials. However, different electroluminescence powers are observed by increasing the alkyl side, this suggesting a potential tool for the selective modulation of TBI functionalities. A deep experimental and theoretical investigation on this new family of TBI materials is provided.
Journal of Materials Chemistry 01/2014; 2(17):3448-3456. · 5.97 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: The role of lipids in controlling water exchange is fundamentally a matter of molecular organization. In the present study we have observed that in snake molt the water permeability drastically varies among species living in different climates and habitats. The analysis of molts from four snake species: tiger snake, Notechis scutatus, gabon viper, Bitis gabonica, rattle snake, Crotalus atrox, and grass snake, Natrix natrix, revealed correlations between the molecular composition and the structural organization of the lipid-rich mesos layer with control in water exchange as a function of temperature. It was discovered, merging data from micro-diffraction and micro-spectroscopy with those from thermal, NMR and chromatographic analyses, that this control is generated from a sophisticated structural organization that changes size and phase distribution of crystalline domains of specific lipid molecules as a function of temperature. Thus, the results of this research on four snake species suggest that in snake skins different structured lipid layers have evolved and adapted to different climates. Moreover, these lipid structures can protect, "safety", the snakes from water lost even at temperatures higher than those of their usual habitat.
Journal of Structural Biology 10/2013; · 3.36 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Despite the variety of functional properties of molecular materials, which make them of interest for a number of technologies, their tendency to form inhomogeneous aggregates in thin films and to self-organize in polymorphs are considered drawbacks for practical applications. Here, we report on the use of polymorphic molecular fluorescent thin films as time temperature integrators, a class of devices that monitor the thermal history of a product. The device is fabricated by patterning the fluorescent model compound thieno(bis)imide-oligothiophene. The fluorescence colour of the pattern changes as a consequence of an irreversible phase variation driven by temperature, and reveals the temperature at which the pattern was exposed. The experimental results are quantitatively analysed in the range 20-200°C and interpreted considering a polymorph recrystallization in the thin film. Noteworthy, the reported method is of general validity and can be extended to every compound featuring irreversible temperature-dependent change of fluorescence.
[Show abstract][Hide abstract] ABSTRACT: Poly(butylene cyclohexanedicarboxylate/diglycolate) random copolymers (P(BCEmBDGn)) of various compositions were synthesized and characterized from the molecular, thermal, structural, and mechanical point of view. Barrier properties to different gases (oxygen and carbon dioxide) were also evaluated. All the polymers showed good thermal stability and appeared as semicrystalline materials at room temperature. The main effect of copolymerization was a lowering in the crystallinity and a decrease of Tm with respect to homopolymers. The dependence of Tm on composition for copolymers with high butylene cyclohexanedicarboxylate unit content was well described by Baur’s equation. X-ray diffraction (XRD) measurements indicated that two different crystalline phases are present, depending on composition: copolymers with high BCE unit content were characterized by PBCE crystal phase, whereas those rich in BDG counits crystallized in PBDG lattice. The samples displayed different surface hydrophilicity: the water contact angle regularly decreased with the increasing mol % of BDG. The mechanical properties were found strictly related to crystallinity degree (χc); the copolymers containing 60–75 mol % of BDG showed the lowest elastic modulus and the highest elongation at break. Lastly, the chemical composition of the copolymer strongly influenced permeability to CO2 and O2. Moreover, the selectivity ratios for the examined samples increased with the increasing of BDG mol %, confirming the existence of a correlation between the permeability and the chemical composition. Almost all copolymers showed improved barrier properties with respect to polylactide films tested under the same conditions.
[Show abstract][Hide abstract] ABSTRACT: Octacalcium phosphate (OCP) interaction with alendronate (AL) solution results in the complete digestion of OCP: calcium ion is recruited by the bisphosphonate to yield quantitative precipitation of crystalline calcium alendronate monohydrate. This compound improves osteoblast differentiation and inhibits osteoclast proliferation and activity, both alone and, even more, in combination with OCP.
[Show abstract][Hide abstract] ABSTRACT: The effects of a moderate variation of the molecular weight on the optical, structural, morphological and transport properties of an anthracene-containing PPE-PPV copolymer are investigated, as well as their overall implication on the photovoltaic parameters of bulk-heterojunction solar cells. Just a two-fold variation in the molecular weight is enough to induce appreciable changes in the properties of the investigated polymer films, indicating that a fine tuning of the macromolecular parameters is required for the optimization of the properties of polydispersed molecular systems. A remarkable role of the polydispersity index in the organization of polymer chains, thus reflecting in the electronic properties of the polymer films, is observed.
[Show abstract][Hide abstract] ABSTRACT: Organic molecular semiconductors are key components for a new generation of low cost, flexible, and large area electronic devices. In particular, ambipolar semiconductors endowed with electroluminescent properties have the potential to enable a photonic field-effect technology platform, whose key building blocks are the emerging organic light-emitting transistor (OLET) devices. To this aim, the design of innovative molecular configurations combining effective electrical and optical properties in the solid state is highly desirable. Here, we investigate the effect of the insertion of a thieno(bis)imide (TBI) moiety as end group in highly performing unipolar oligothiophene semiconductors on the packing, electrical, and optoelectronic properties of the resulting materials. We show that, regardless of the HOMO–LUMO energy, orbital distribution, and molecular packing pattern, a TBI end moiety switches unipolar and nonemissive oligothiophene semiconductors to ambipolar and electroluminescent materials. Remarkably, the newly developed materials enabled the fabrication of single layer molecular ambipolar OLETs with optical power comparable to that of the equivalent polymeric single layer devices.
[Show abstract][Hide abstract] 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.
[Show abstract][Hide abstract] ABSTRACT: Export Date: 24 June 2013, Source: Scopus, CODEN: CGDEF, :doi 10.1021/cg3012712, Language of Original Document: English, Correspondence Address: Monari, M.; Dipartimento di Chimica G. Ciamician, University of Bologna, Via Selmi, 2, I-40126 Bologna, Italy; email: firstname.lastname@example.org, References: Uemura, T., Yanai, N., Kitagawa, S., (2009) Chem. Soc. Rev., 38, pp. 1228-1236;