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New polymeric photoinitiators bearing the side-chain camphorquinone moiety spaced from the backbone by a long and flexible connection have been prepared and tested in the photocuring of acrylic monomers upon irradation with visible light in the presence of tertiary amine coinitiator. The results indicate that the photoinitiating activity of the polymeric initiators may be comparable to the related combination of low molecular weight derivatives when the camphorquinone component has a polymeric structure, and depends on the chemical structure of both the components of the initiator/coinitiator pair. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 5879–5888, 2005

Chemical physical analysis, photo-oxidative stability and lipid oxidation of innovative polymeric films based on blends of nylon 6 and ethylene-co-vinyl alcohol for use in food packaging have been investigated. Thermal mechanical analysis showed that the presence of an interfacial agent in the blend stabilized the films towards the action of permeants. Synergistic effects of the interfacial agent are reported with respect to UV photostability. Peroxide value (PV) was used to follow the oxidation of the olive oil, and for this parameter also the influence of the interfacial agent was clearly detected. Copyright © 2001 John Wiley & Sons, Ltd.

A detailed re-examination of the photo-oxidation mechanism of poly(2,6-dimethyl-1,4-phenylene oxide) (PPO) at both long and short irradiation wavelengths under accelerated conditions is reported. The formation rate of polydimethylphenoxy (PDMP) radicals is observed both in the presence and in the absence of ultra-violet (u.v.) light by using electron spin resonance spectroscopy. In order to explain the great stability of PDMP radicals, the bimolecular decay observed in the dark is discussed. In addition, spin-trapping experiments using nitrosodurene reveal the existence of benzylic-type radicals under u.v. irradiation conditions. Under mild oxidative conditions, i.e. thermo-oxidation at 80°C, the changes in the Fourier-transform infra-red spectra after 1215 h show the formation of two main absorption bands at 1694 and 1658 cm −1 , assigned to aromatic aldehydes and quinonic groups, respectively. The poor photo-stability of these two primary oxidation products generates, by fast photolytic conversion to benzoic acids and esters. a broad band centred at 1734 cm −1 under accelerated photo-oxidative conditions. Furthermore, the cyclic voltammetry of PPO solution in the dark indicates both the existence of superoxide radical anions in the absence of u.v. light and the electro-catalytic effect possibly induced by quinonic groups. In this work direct formation of radical cations and superoxide anions by a photo-induced electron-transfer reaction is suggested under photo-oxidative conditions. The catalytic role of quinonic groups on the further generation of superoxide anions and PDMP radicals at long irradiation wavelengths and in the dark is also considered on the overall PPO photodegradation.

The physical and dynamic-mechanical behaviour during the photo-oxidation under accelerated conditons of three poly(ethylene-co-propene-co-5-ethylidene-2-norbornene) (EPDM) rubbers with different contents of 5-ethylidene-2-norbornene1 (ENB) are reported. These results show the dependence of the glass transition temperature both on the ENB content and on the photo-oxidation time in accordance with network formation in the rubber matrix under accelerated conditions. The tensile experiments also show an increase of the elastic modulus as function both of ENB content and of photo-oxidation time. The Murayama and Mooney-Rivlin equations are applied to estimate the average molecular weight between two crosslinking nodes occurring in the rubber matrix during photo-oxidation with tensile and dynamic-mechanical experiments, respectively. Some correlations of physical and dynamic-mechanical changes with the proposed mechanism of photo-oxidation, due to the formation and reactivity of unsaturated groups, show that the crosslinking processes prevail over chain scissions.

In this work the reexamination of the photo-oxidation mechanism of three poly(ethylene-co-propene-co-5-ethylidene-2-norbornene) (EPDM) terpolymers containing different amounts of 5-ethylidene-2-norbornene (ENB)1 (2-8 wt.-%) is discussed. The photo-oxidation depends on the initial content of ENB units in the chains. The formation of a band at 923 cm−1 is attributed to the CH out-of-plane deformation of a new double bond in terminal position in the ethylidene moieties. The presence of double bond migration suggests the formation of stable tertiary hydroperoxides which show a new band at 870 cm−1. The kinetic behaviour of a band with similar spectral pattern in the UV at 235 nm has been correlated with double bond migration. The identification of photoproducts both by 2,4-dinitrophenylhydrazin and SO2 confirms the proposed spectroscopic assignments. The gel measurements of the studied terpolymers, and some comparisons with a poly(ethylene-co-propene) (EPR) copolymer having a similar ethylene to propene ratio, suggest that the presence of ENB can strongly influence both the photo-oxidation and the crosslinking yields of these rubbers.

In this paper we report the light-induced grafting copolymerization of N , N ′-dimethylacrylamide onto four poly(organophosphazene) films i.e. poly[bis(4-isopropylphenoxy)phosphazene], poly[bis(4-s-butylphenoxy)phosphazene], poly[bis(4-benzylphenoxy)phosphazene] and poly[bis(2,2′,2″-trifluoroethoxy)phosphazene]. The process was carried out in N , N ′-dimethylacrylamide/methanol mixtures in presence of benzophenone as sensitizer. The yield of the grafting process was evaluated as a function of the phosphazene structure, of the relative amounts of N , N ′-dimethylacrylamide and methanol in the reaction mixtures, and of the swelling capability of the polymer films. The obtained polyphosphazene-g-poly- N , N ′-dimethylacrylamide copolymers were characterized by i.r. spectroscopy, both ATR and transmission, and by contact angle measurements.

The photochemical behaviour of [C 5 (CH 3 ) 5 Rh(CO) 2 ] has been examined in a polystyrene matrix and in a hexane solution. Photodissociation of CO yields the coordinatively unsaturated [C 5 (CH 3 ) 5 RhCO] fragment as the primary photoproduct. Photodissociation of the C 5 (CH 3 ) 5 Rh bond is observed in solution upon long wavelength irradiation of the [C 5 (CH 3 ) 5 Rh(CO) 2 ] giving ·Rh(CO)2 and C 5 (CH 3 ) 5 · radicals as primary photoproducts. The identity of the radicals has been demonstrated by spin trapping ESR spectroscopy experiments. After prolonged photolysis in a polystyrene matrix, the CH activation product [C 5 (CH 3 ) 5 Rh(CO)(H)(polystyrene)l is formed via [C 5 (CH 3 ) 5 RhCO]. The role of the [C 5 (CH 3 ) 5 RhCO] intermediate in solution reactions is discussed.

We present the first type of tetraazide-functionalized calix[4]arene TiO(2) nanoparticles and their coupling to propargyl glycosides under Cu(I)-catalysis (click reaction), resulting in the immobilization of calix[4]arene-based glycoclusters on the TiO(2) surface.

This paper presents results on the photo-induced grafting of poly(methyl methacrylate) onto poly[bis(4-isopropylphenoxy)phosphazene], using benzophenone as photoinitiator. The formation of polyphosphazene-g-poly(methyl methacrylate) copolymers was followed by FTIR-ATR spectroscopy, and the products were characterized by contact angle and DSC measurements. Among the parameters affecting the photografting, irradiation time and the ratio methanol/unsaturated monomer used in the grafting experiments are of particular importance.

The thermal and photochemical reactions of [(C 5 Me 5 )Fe(CO) 2 ] 2 with 2,3-dichloro-5,6-dicyanobenzoquinone (DDQ) yield the binuclear complex {[(C 5 Me 5 )Fe(CO) 2 ] 2 ·(DDQ) 2 }. EPR studies using nitroso spin traps support the conclusion that the primary products are [(C 5 Me 5 Fe(CO) 2 ] + radicals. The metal-centered radical transfers an electron to DDQ acceptor to yield {[(C 5 Me 5 )Fe(CO) 2 ] 2 ·(DDQ) 2 } as the only Fe-containing product. Spectroscopic evidence for dimerization of DDQ − to form diamagnetic [DDQ] 2− 2 in the solid is discussed.

Four different types of montmorillonites have been dispersed by sonication at 50 °C into a propoxylated aromatic epoxy diacrylate oligomer to achieve interlayered or exfoliated nanocomposites. A thermally-induced crosslinking 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 °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.

Copolyethers and polyurethanes containing lower and upper rim calix[4]arene units in the fixed cone conformation were prepared in good yield by polycondensation reactions of distal calix[4]arene diols with bisphenol-A/dibromomethane and 2,4-tolylendiisocyanate (TDI), respectively. In a similar way were prepared calix[4]arene-crown-5 and -crown-6 polyurethanes in the fixed 1,3-alternate conformation by condensation of TDI with lower rim calixcrown-5 and calixcrown-6 diols. However, the poor solubility in common organic solvents of the copolyether derivatives (M w ¼ 11; 100 - 11; 600 g/mol) hampered further studies on their ionophoric properties. Aiming to obtain model compounds for the investigation of both extraction abilities and ionophoric properties of the polyurethane materials, several bis-urethanes were also synthesized by reaction of the calix[4]arene diols with p-tolylisocyanate (TI). The extraction ability measurements of monomeric and polymeric calix[4]arene urethanes (M w ¼ 12,300 - 83,500 g/mol) towards alkali metal cations (Li þ ,Naþ ,K þ ,Rbþ ,Cs þ ) and Ag þ showed a remarkable efficiency and selectivity of calixcrown-6 polyurethane toward Rbþ ,Csþ and Agþ .

The polymerization of (+)-catechin with various aldehydes has been performed in the presence of an acid catalyst to produce catechin-aldehyde polycondensates in high yields. NMR analysis of the product showed that the polymerization regioselectively proceeded to form the polymer linked by an ethyl bridge through C-6 and C-8 positions of catechin A ring. Specific rotation and CD measurements of the polymer showed the change of chemical bonding and confromation at near chiral center. The direction of specific rotation was changes from dextrorotatory (+) to levorotatory (-) and a new chiral center was formed on the bridge moiety between the catechin units. Computer simulation suggests the coiled interactions in the polymer by hydrogen bonds between hydroxyl groups and pyranic oxygens.

The syntheses of methacrylate- and styrene-based monomers containing substituted pyridine ligands are reported. The preparation of the corresponding homopolymers has been performed by free radical polymerization by using 2,2'-azoisobutyronitrile (AIBN) at 60°C. The high molecular weights, up to 119 000 g. mol -1 , and low glass transition (T g ) values (< -43°C) have been obtained by the copolymerization reaction with butyl acrylate. The free metal homopolymer and copolymer were subsequently metalated by reaction with Re[phen(CO) 3 (acetone)]+. All polymer materials have been characterized by conventional experimental techniques, such as gel permeation chromatography (GPC), differential scanning calorimetry (DSC), and thermogravimetric analysis (TGA). UV-Vis and fluorescence spectroscopy have been used to investigate the optical and photophysical properties of the polymers in solid-state films and in solution. 1H NMR spectra confirmed the structure of the synthesized polymers and contributed to the estimate of the monomer sequences in the copolymer chains. Time-resolved and emission-quenching experiments in diluted solutions and on the solid films suggest application of the polymeric materials as oxygen sensors. The morphological aspects of some polymers containing a low amount of rhenium metal complexes have been investigated by scanning electron microscopy (SEM).

A modified interfacial polycondensation between bisphenol-A and 1,3-dimethoxy lower-rim substituted calix[4]arene derivatives with dibromomethane in the presence of tetrabutylammonium hydrogen sulfate as phase transfer catalyst (PTC) leads to copolyethers with variable M w values depending on the reaction temperature and the amount of PTC. The calix[4]arene content in the polymer chains depends on the phenolic monomer ratios. The polycondensation reaction of the same comonomers with terephthaloyl chloride but in the absence of the above PTC affords the corresponding copolyester. The soluble fraction of this polymeric material in CHCl 3 showed M w of ca. 21000 and a variable calix[4]arene content depending on the phenolic monomer ratio as well. The binding properties of the copolyethers toward silver ions are ten-fold higher than those of a model tetraalkoxy calix[4]arene derivative. It is suggested that this increased receptor ability is due to the change of the original cone conformation of the macrocyclic monomer into the partial-cone conformation by incorporation in the polymer.

The synthesis of 1,3-dimethyl calix[4]arene–bisphenol-A copolyethers and copolyesters with variable amounts of the macrocycle in the chain is described; the receptor ability of the copolyethers 4 toward silver(I) ions was one hundred-fold that of calix[4]arene tetrapropyl ether 3.

Spectroscopic methods, ultraviolet (UV) and Fourier transform infrared (FTIR) were used to determine the concentrations of the two components of hindered amine light stabilisers (HALS) in low density polyethylene (LDPE) films exposed to natural weathering up to 650 days. The used HALS is a Ciba-Geigy commercial mixture of Chimassorb 944 and Tinuvin 622 with same percentage in weight (50/50% (wt/wt)). The spectroscopic measurements were carried out on the LDPE films having some different HALS contents of 0.1, 0.2, 0.4, and 0.6% (wt/wt). The Chimassorb 944 concentration was determined by means of the absorption band area centred at 225 nm in UV spectra for the absorption of 1,3,5-triazine group, while Tinuvin 622 concentration was measured by the absorption band area at 1734 cm−1 in FTIR spectra corresponding to the ester group absorption. The plots describing the loss of the concentration of each component versus time exhibited similar profiles. The results suggest that the two HALS components are involved at the same time in the polymer stabilisation processes. The effect of the HALS concentration on LDPE stabilisation was interpreted applying the well-known operative mechanisms involving piperidinoxyl radicals for natural and accelerated photo-oxidative conditions. Finally electron spin resonance spectroscopy performed on 0.6 and 0.2% under natural exposure formulations are in good agreement with the spectroscopic determination of the HALS contents in the different formulations.