1,720,981 research outputs found
Photopolymerization kinetics of UV curable systems for polymer dispersed liquid crystal
No full textThe preparation methods and the materials used
for the production of polymer dispersed liquid crystals
(PDLC) are reported. The photopolymerization
induced phase separation (PIPS) method is also
discussed in terms of the kinetic behaviour observed
for these materials. In addition, the thermodynamic
aspects of the phase separation have been briefly
included in the text describing the thermal properties
of the mixture before and after UV curing. The
determination of the experimental kinetic parameters
and the techniques to study photopolymerization
reactions are also discussed for UV curable
formulations containing mono(meth)acrylate and
diacrylate monomers and reactive oligomers. Finally,
an example of the photopolymerization kinetic behaviou
Composizione sigillante per per l’isolamento di dispositivi sensibili alla permeazione di umidità dall’ambiente esterno
No full textThe present invention relates to a sealant composition for the isolation of devices that are sensitive to permeation of moisture from the external environment.
It is well known that the insulating structures for moisture-sensitive devices are made with the aid of sealants compositions having a low rate of water vapor transmission
Interpenetrated polymer network formed by UV curable modified epoxyacrylates using dual curing polymerization
No full textThe materials and methods used for the preparation of interpenetrated
polymer network (IPN) by UV curing processes are reported. In particular,
recent developments on the formation and characterization of some sequential
IPN based on mixtures of commercially available diglycidyl ether of bisphenol-A
(DGEBA) epoxy resins and UV curable epoxy-dimethacrylate resins are
discussed. Finally, the photopolymerization kinetic behavior and thermal
properties of some UV curable mixtures based on the modified epoxydimethacrylate
resins for the preparation and characterization of a grafted
sequential IPN are described
Crystal Structure and Spectroscopic Analyses of Guanylurea Hydrochloride. Evidence of the influence of Hydrogen Bonding on the pi-Electron Delocalization
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Polymerization Kinetics and Characterization of Dual Cured Polyurethane‐Acrylate Nanocomposites for Laminates
No full textFour different types of montmorillonites have been dispersed by sonication at 50 degrees C into a propoxylated aromatic epoxy diacrylate oligomer to achieve interlayered or exfoliated nanocomposites. A thermally-induced cross-linking reaction, forming a polyurethane network in the presence of 7 wt.-% of a montmorillonite, has been promoted by addition of an allophanate modified polyisocyanurate based on hexamethylene diisocyanate. The kinetic behavior of the network formation has been studied at 25, 40 and 60 degrees C by following the disappearance of the isocyanate vibrational band found at 2 270 cm(-1). A tight crosslinked polyurethane acrylate network has been achieved by a subsequent dual UV curing promoted by a photoinitiator mixture (0.6 wt,-%) added to the reactive mixture because of further reactions occur to the acrylate double bonds. The photopolymerization kinetic has been investigated on the different thermally treated polyurethane nanocomposite networks by Real Time FTIR spectroscopy monitoring the changes of the IR band at 810 cm(-1) assigned to the acrylate double bond vibrations. The influence of the different montmorillonite clays on the final nanocomposite morphology has been investigated by using XRD and SEM. Finally, the use of these mixtures as internal layer between two modified surface PET films has been also studied for the laminate production. The based-PET laminate films have been characterized by determining the bending resistance and optical properties as a function of different nanofillers
Further EPR-spin trapping studies of the photoinitiating activity of Irgacure 369
No full textThe radicals formed upon visible light irradiation of the photoinitiator 2-benzyl-2-dimethylamino-
40-morpholinobutyrophenone (Irgacure 369), 1, were investigated by means of
EPR spectroscopy coupled with the spin trapping technique both in the absence and in
the presence of a monomer. The results suggest a dual behavior of 1 that may act both
as a Type I and a Type II photoinitiator. From experiments carried out in the presence of
2-ethoxythioxanthone (Pila 124), 2, an additive commonly used in combination with 1
as sensitizer, it is inferred that 2 mainly acts via hydrogen abstraction from 1.
2008 Elsevier Ltd. All right
CHARGE-TRANSFER COMPLEXES - PHOTOINDUCED ELECTRON-TRANSFER OF 1,2-DITHIOLENE COMPLEXES OF NICKEL AND PLATINUM
No full textTreatment of the complex [(C6H6)(2)Cr]I with [(n-C4H9)(4)N](2)[MS(4)C(4)(CN)4] (M = Ni, Pt) affords the new compounds {[(C6H6)(2)Cr](2)[MS(4)C(4)(CN)(4)]} (1, M = Ni. 2, M = Pt). Compounds 1 and 2 are identified as charge-transfer (CT) complexes by their absorption and diffuse reflectance spectra. The new CT absorption in the visible region, in the solid state and in non polar solvents is consistent with the formation of contact ion pairs (CIP) in 1 and 2. Accordingly, photoexcitation of the charge-transfer absorption band of the CIPs leads to (C6H6)(2)Cr and [(C6H6)(2)Cr][MS(4)C(4)(CN)(4)] (4, M = Ni; 5, M = Pt) The UV-visible, IR and ESR data for the new complexes are reported and discussed in relation to the charge-transfer photochemistry of contact ion pairs
Plastic debris in the Mediterranean Sea: Types, occurrence and distribution along Adriatic shorelines
No full textSmall plastic debris in sediments from five beaches were investigated to evaluate their occurrence and abundance in the Northern Adriatic coast for the first time. Plastic debris extracted from sediments were counted, weighted and identified by Fourier-transform infrared spectroscopy (FT-IR). A total of 1345 items of debris (13.491 g) were recorded, with a mean density of 12.1 items kg1 d.w. and 0.12 g kg1 d.w. Fragments were the most frequent type of small plastics debris detected. In terms of abundance, microplastics (<5 mm) accounted for 61% of debris, showing their wide distribution on Adriatic coasts, even far-away from densely populated areas. The majority of the polymers found were polyolefins: there were greater quantities of polyethylene and polypropylene compared to other types of plastic. Primary microplastics accounted for only 5.6% of the total plastic debris. There were greater quantities of microplastics at sites subjected to stronger riverine runoff. The results will provide useful background information for further investigations to understand the sink and sources of this emergent and priority contaminant
Near-field optical addressing of luminescent photoswitchable supramolecular systems embedded in inert polymer matrices
No full textOptical recording and luminescence readout of novel covalently linked photochrome/luminophore supramolecular complexes has been demonstrated by near-field scanning optical microscopy (NSOM). Localized UV irradiation of these complexes dispersed in polymeric matrices resulted in photoinduced state switching and a concomitant increase in emission intensity. Subsequent luminescence imaging showed well-resolved luminescent data bit arrays with good signal-to-noise ratios. Spatially resolved emission spectra of the luminescent data bits confirmed the switching mechanism
Rheological, thermal and spectroscopical properties of the macromolecular complex between sodium hyaluronate and cisplatin for anticancer chemotherapy
Full text linkHyaluronic acid and its sodium salt (sodium hyaluronate; hyaluronan; NaHA) are widely used for drug delivery. Here, a thin film of high molecular weight NaHA with the anticancer agent cisplatin (cisPt) was prepared to deliver the drug loco-regionally on the pleura after tumor resection. For preparing films, NaHA, cisPt, and excipients were dissolved in water; the resulting viscous film-forming mixture (FFM) was cast into wet films and dried. It was discovered that a cisPt/NaHA complexation in films was responsible for the observed higher drug efficacy from films. Here, we investigated the rheological, thermal and spectroscopical properties of the cisPt/NaHA complex. The size exclusion chromatography (SEC) showed a unimodal molecular weight distribution of NaHA in aqueous solution. The viscosity of FFM increased with increasing cisPt concentration, indicating cross-linking due to cisPt/NaHA complexation. In DSC analysis, the water evaporation temperature of both FFM and film decreased due to cisPt/NaHA complexation, suggesting that the complexation with Pt2+ displaced water molecules originally bound to NaHA. FTIR-ATR spectral changes in cisPt-loaded vs. placebo films suggested that complexation involved the carboxylate groups of the polysaccharide. Finally, energy dispersive spectroscopy coupled with SEM demonstrated that the cisPt/NaHA complex in films appeared to be a network of aggregates
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