Study on the Effect of Uniaxial Elongational Flow on Polyamide Based Nanocomposites

This work focuses on the study of uniaxial elongational flow and its effects on morphology and stiffness of polyamide-6 based nanocomposites prepared by melt compounding. The elongational flow characterization was realized by converging flow method and fiber spinning technique. During the haul-off tests, fibers of the neat polyamide-6 and the hybrids (at 3 and 6 wt% of silicate) were collected at different draw ratios. Mechanical properties of the produced fibers were investigated and correlated to their nanostructure through analytical techniques sensitive to different aspects of morphology, such as DSC and TEM analysis. Rheological results, obtained with a capillary rheometer, indicate that the shear viscosity decreases with the silicate loading, while the extentional viscosity increases. Moreover, the presence of the silicate in polymer matrix leads to enhancements of draw-down force and reduction of the breaking draw ratio. In hybrid fibers an enhanced degree of exfoliation of the filler was observed upon drawing. Moreover, DSC analyses suggest that the crystalline structure of the fibers is the result of two opposite effects: the presence of the silicate which stabilizes the γ form and the drawing which promotes the α crystal phase. The degree of silicate exfoliation and the amount of the different crystal phases strongly affect the tensile properties of the fibers.     

In situ gel forming graft copolymers of a polyaspartamide and polylactic acid: Preparation and characterization

In situ gel forming systems have been prepared by linking polylactic acid (PLA) to a water soluble and polyfunctional polymer, such as α,β-poly(N-2-hydroxyethyl)-d,l-aspartamide (PHEA). Three graft copolymers PHEA-PLA with a different derivatization degree in PLA, have been synthesized and characterized. PHEA-PLA graft copolymer with the highest amount in PLA has been used to prepare solutions in organic solvents able to give rise to gel-like matrices when injected into phosphate buffered saline solution. The chemical degradation of these gels has been evaluated and in vitro tests have been performed to evaluate the cell compatibility of the hydrolysis products. The possibility to use these gels for drug release has been investigated by incorporating leuprolide as a peptide model drug and by evaluating its in vitro release. To improve the drug release profile, PHEA-PLA graft copolymer has been derivatized with pendant carboxylic groups that are able to form an ion pair with the leuprolide thus reducing the burst effect and prolonging its release.     

Uncatalyzed conversion of linear α-nitro ketones into amides by reaction with primary amines under solventless conditions

The reaction of linear α-nitro ketones with primary amines allows the formation of amides through the cleavage of the carbon-carbon bond between the carbonyl group and the carbon-nitro group moiety, promoted by the nucleophilic effect of the amine. The reaction is performed at room temperature, without any catalyst and/or solvent.     

Thiosteroids in sewage sludge and its post-treatment products

Different sulphur compound derivatives from steroids were detected and quantified in the analysis of the lipidic fraction of sewage sludge and its post-treatment products, including thermally dried sludge and compost. Some steroid thiols: 5α-cholestane-3β-thiol, 24-methyl-5α-cholestane-3β-thiol and 24-ethyl-5α-cholestane-3β-thiol were detected in the gas chromatography with mass spectrometry detector (GC-MS) analysis. These three compounds, related to the thiostanol family, have only been encountered in previous studies in sea sediments. Gas chromatography with sulphur-selective flame photometric detector (GC-FPD) was used with the objective of detecting other related compounds in sludge. It allowed the detection of other compounds, whose mass spectra could correspond with the one of the steroid enethiols. The research focused on detecting the formation point of these sulphur compounds in the sludge treatment process, as well as their biodegradation resistance in the post-treatment processes. The amount of these products in the sludge was quantified using gas chromatography with flame ionization detector (GC-FID). The result of this study confirms that the identified compounds are not easily biodegradable.     

Polyvinyl‐Locked versus Free Quaterthiophene: Effect of Spatial Constraints on the Electronic Properties of n‐Hexylquaterthiophene

A soluble, low‐weight fraction of poly(α‐vinyl,ω‐n‐hexyl‐quaterthiophene), PT4Hex, having n‐hexylquaterthiophenes as side‐chain groups, is prepared by free‐radical polymerization of α‐vinyl,ω‐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 π–π orbitals to overlap (～4 Å). 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.     

Synthesis and luminescent properties of novel lanthanide(III) beta-diketone complexes with nitrogen p,p'-disubstituted aromatic ligands

Tris-beta-diketonate lanthanide(III) complexes (Ln = Eu, Er, Yb, Tb), of general formula [Ln(acac)3 L(m)], with chelating ligands such as 4,7-disubstituted-1,10-phenanthrolines and 4,4'-disubstituted-2,2'-bipyridines, have been synthesized and fully characterized. The inductive effects of the para-substituents on the aromatic N-donor ligands have been investigated both in the solid and in the solution states. Single-crystal X-ray structures have been determined for the diethyl 1,10-phenanthroline-4,7-dicarboxylate europium and 4,4'-dimethoxy-2,2'-bipyridine erbium derivatives, revealing a distorted square antiprismatic geometry around the lanthanide atom in both cases. The influence exerted by the p,p'-substituents with respect to the nitrogen coordinating atoms on the Ln-N bond distances is discussed comparing the geometrical parameters with those found for the crystal structures containing the fragments [Ln(III)(phen)] and [Ln(III)(bipy)] obtained from the Cambridge Structural Database. The influence exerted by the electron-attracting groups on the coordination ability of the ligands, that in some cases becomes lack of coordination of the lanthanide ions, has been also detected in solution where the loss of the ligand has been followed by UV-vis spectroscopy. Moreover, the use of relatively long alkoxy chains as substituents on the 1,10-phenanthroline ligand led to the formation of a promesogenic lanthanide complex, whose thermal behavior is encouraging for the synthesis of new lanthanide liquid-crystalline species.     

Theoretical and electrochemical analysis of dissociative electron transfers proceeding through formation of loose radical anion species: reduction of symmetrical and unsymmetrical disulfides

The dissociative reduction of a series of symmetrical (RSSR, R = H, Me, t-Bu, Ph) and unsymmetrical disulfides (RSSR', R = H, R' = Me and R = Ph, R' = Me, t-Bu) was studied theoretically, by MO ab initio calculations and, for five of them, also experimentally, by convolution voltammetry in N,N-dimethylformamide. The reduction is dissociative but proceeds by a stepwise mechanism entailing the formation of the radical anion species. The electrochemical data led to estimated large intrinsic barriers, in agreement with an unusually large structural modification undergone by the disulfide molecules upon electron transfer. The theoretical results refer to MP2/3-21G*//MP2/3-21G*, MP2/3-21*G*//MP2/3-21G*, CBS-4M, and G2(MP2), the latter approach being used only for the molecules of small molecular complexity. A loose radical-anion intermediate was localized and the dissociation pattern for the relevant bonds analyzed. For all compounds, the best fragmentation pathway in solution is cleavage of the S-S bond. In addition, S-S bond elongation is the major structural modification undergone by the disulfide molecule on its way to the radical anion and eventually to the fragmentation products. The calculated energy of activation for the initial electron transfer was estimated from the crossing of the energy profiles of the neutral molecule and its radical anion (in the form of Morse-like potentials) as a function of the S-S bond length coordinate. The inner intrinsic barrier obtained in this way is in good agreement with that determined by convolution voltammetry, once the solvent effect is taken into account.     

Production of Enzymes by Plant Cells Immobilized by Sol-Gel Silica

Ajuga reptans cells are cultivated and used for production of invertase. These plant cells are immobilized by a sol-gel SiO₂ membrane, which is built up directly on the cell surface by exposure to a gaseous flow of silicon alcoxide precursors. The immobilization modifies the metabolic activity of cells, resulting in a 40-fold increase in invertase production with respect of free cells. Results concerning total release of proteins, cell growth and produced invertase activity are discussed, considering the absence of breeding, induced by SiO₂ immobilization, the prominent factor promoting the observed exceptional increase in invertase productivity.     

UV-photocrosslinking of inulin derivatives to produce hydrogels for drug delivery application

In this work, INU, a natural polysaccharide, has been chemically modified in order to obtain new photocrosslinkable derivatives. To reach this goal, INU has been derivatized with MA thus obtaining four samples (INU-MA derivatives) as a function of the temperature and time of reaction. An aqueous solution of the derivative INU-MA1 was irradiated by using a UV lamp with an emission range from 250 to 364 nm and without using photoinitiators. The obtained hydrogel showed a remarkable water affinity but it underwent a partial degradation in simulated gastric fluid. To overcome this drawback, INU-MA1 was derivatized with SA thus obtaining the INU-MA1-SA derivative designed to produce a hydrogel showing a low swelling and an increased chemical stability in acidic medium. Ibuprofen, as a model drug, was loaded by soaking into INU-MA1 and INU-MA1-SA hydrogels and its release from these matrices was evaluated in simulated gastrointestinal fluids. INU-MA1 hydrogel showed the ability to quickly release the entrapped drug thus indicating its potential as a matrix for an oral formulation. INU-MA1-SA hydrogel showed a pH-responsive drug delivery. Therefore it is a promising candidate for controlled drug release in the intestinal tract.