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We investigated the occurrence of plastic contamination in sediments collected in the area of Pianosa Island (Adriatic Sea). In November 2015, 20 sediment samples were collected at depth varying between 119 and 142 m. At the laboratory, plastic debris in samples were weighted, measured and classified into dimensional groups, and categorized according to shape. Polymer types were identified using FT-IR analysis. All sediment samples contained plastics. In terms of numerical abundance, microplastics accounted for 64.4% of the total amount found. Filaments (66%) were the most common shape category. Identification through FT-IR spectroscopy evidenced the presence of 6 polymer types. Considering abundance, the majority of plastic debris were nylon (53.2%), followed by polyethylene (18%). By weight, polyethylene (61.4%) was the most represented polymer type, followed by polypropylene (19.6%). Because the distance from the coast, we hypothesize that plastics could be originated from marine-based sources including fishing vessels, merchant vessels and recreational boats.

We investigated the concentration and composition of plastics in 7 Special Areas of Conservation (SACs) from the Gulf of Venice (northern Adriatic Sea). A total of 42 sediment samples were analyzed from 21 sites from 2017 to 2018. All sites except one were found to be polluted by plastics, with density ranging between 2250 and 28.4 items kg−1. Microplastics ranged from 100 to 61.6% of the collected plastics. Fragments were more represented than filaments. The greatest plastic concentrations were generally recorded in western SACs. Identification through FT-IR spectroscopy evidenced the presence of 8 polymer types: in western SACS, the majority were low-density polymers (PE, PP, PS, and TPU), while in eastern SACs they were high-density polymers (PET, nylon, and PVC). In addition to the role of large rivers (all on the western side of the Gulf) in conveying plastics into the sea, a possible role of the cyclonic water circulation of the northern Adriatic Sea on distribution and composition of plastics along the Gulf coasts is likely.

We investigated the temporal concentration of floatable plastic particles in the Po river, the largest contributor of freshwater to the Adriatic Sea. Surface waters were sampled in 2019 with a Manta trawl, with almost bimonthly frequency. In total, 5063 plastic particles were collected, 80.6% of which were microplastics (5 mm). Characterization through FT-IR spectroscopy evidenced 7 polymers, of which polyethylene, polypropylene and polystyrene accounted for 40.5%, 25.7%, and 14.9%, respectively. The highest plastic concentration was recorded in December (3.47 particles m

This is the first survey to investigate the occurrence and extent of microplastic contamination in sediments collected along a coast-open sea 140 km-long transect in the Central Adriatic Sea. Plastic debris extracted from 64 samples of sediments were counted, weighted and identified by Fourier-transform infrared spectroscopy (FT-IR). Several types of plastic particles were observed in 100% of the stations. Plastic particles ranged from 1 to 30 mm in length. The primary shape types by number were filaments (69.3%), followed by fragments (16.4%), and film (14.3%). Microplastics (1–5 mm) accounted for 65.1% of debris, mesoplastics (5–20 mm) made up 30.3% of total amount, while macro debris (> 20 mm) accounted for 4.6% of total plastics collected. Identification through FT-IR spectroscopy evidenced the presence of 6 polymer types: the majority of plastic debris were nylon, polyethylene and ethylene vinyl alcohol copolymer. Our data are a baseline for microplastic research in the Adriatic Sea.

Small 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 (13.491g) were recorded, with a mean density of 12.1 items kg-1 d.w. and 0.12gkg-1 d.w. Fragments were the most frequent type of small plastics debris detected. In terms of abundance, microplastics (

In this investigation, two novel multifunctional initiators for ring-opening polymerization were synthesized in three steps starting from cholic acid. Thus, cholic acid (1a) and its methyl ester (1b) were quantitatively transformed, via solvent-free reaction with succinic anhydride, to the corresponding 3, 7, 12-tri-hemisuccinate derivatives (3a-b). The polyacidic compounds (3a-b) were treated with thionyl chloride affording the corresponding acyl chlorides 4a-b which, in turn, were reacted with ethylene glycol to give the derivatives 2a-b having three and four primary alcohol end groups. These compounds, fully characterized by H, C NMR and mass spectrometry, have been assessed as initiators in the ring-opening polymerization of L-lactide using stannous octanoate as catalyst. The resulting three- and four-armed star-shaped poly(L-lactide)s, which were characterized by H NMR, SEC, DSC and TGA analysis, were amorphous, and their glass transition temperatures ranged from 13.7 to 36.5 °C. Additionally, some cholic acid-based star-shaped polylactic structures recently published have been critically reconsidered showing that these molecules, described as star polymers, were actually linear polymers.

The self-assembling of fluorescent guest molecules, with the δ nanoporous host crystalline phase of syndiotactic polystyrene (s-PS) films, reduces chromophore diffusivity. Moreover, the chromophore...

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.

The diffusion of a thermal stabiliser, Irganox 1010, has been studied both in a commercially available polypropylene homopolymer (HomoQ) and in a poly(propylene-co-ethylene) copolymer (RacoS). The diffusion experiments were carried out by using the Roe method formed by a stack of several polymer films having 60–70 μm as thickness under nitrogen atmosphere. The concentration profile of stabiliser in every film has been monitored by the absorbance at 282 nm in UV spectra recorded for every film forming the stack assembly. Under our experimental conditions, the diffusion of Irganox 1010 in each film stack for both polymer materials can be correctly interpreted by using the Fick's second law. The best fit of the experimental data with this equation allows calculation of the diffusion coefficients, D, for these polymer materials at 40, 70 and 80 °C. By applying an Arrhenius equation to the calculated D coefficients, an estimation of activation energies of the diffusion process has been also achieved.

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 photooxidation of poly[bis(4-isopropylphenoxy)phosphazene] under accelerated conditions has been followed by FTIR and UV visible spectroscopic techniques. The main photooxidation products are acetophenone and phenol groups. In addition, acetone vapors have been detected by GC MS combined techniques concomitant with the IR spectral changes in the CH stretching region, suggesting a significant decrease in the isopropyl moieties. The presence of polymeric sequences having phenol groups under our conditions gives origin to further oxidation reactions due to electron transfer or radical recombination or to hydrogen abstraction reactions promoted by unhindered phenoxyl radicals. In addition, the absence of UV visible light, i.e., under thermooxidation reaction at 60° C has demonstrated that phenol groups are the main responsible of secondary oxidation products. The complexity of the photooxidation mechanism in the solid state for this polymer makes it difficult to determine a definitive degradation mechanism under both thermo- and photooxidative conditions.

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.

Photodegradable polyolefins based on ketone carbonyl and carbon monoxide copolymers are discussed. The proposed photo-oxidation mechanisms for these copolymers show efficient chain scission processes photoinduced by Norrish I and II reaction in polymer matrix. Other polyolefins copolymers containing unsaturation have been suggested as new innovative and photodegradable materials. In the photo-oxidative conditions, the formation of α,β-unsaturated ketone impart high yields of chains scissions leading to a rapid embrittlement and fragmentation of these copolymers.

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.

In this paper we present results on the photolysis of poly[bis(4-benzylphenoxy)-phosphazene] in solution and in film, both in the presence and in the absence of molecular oxygen. Light irradiation of the polymer in oxygen-saturated CH2Cl2 solutions results in a remarkable degradation of the polyphosphazene, while in argon-purged solutions no appreciable variations of the polymer structure could be detected. The photolysis of poly[bis(4-benzylphenoxy)phosphazene] in films induces the cross-linking of the polymer regardless of the presence or the absence of molecular oxygen. The main process observed during the photochemistry both in solution and in the solid state of the polymer is the oxidation of the 4-benzylphenoxy group on the polyphosphazene, without involvement of the inorganic -P=N- backbone. The effect of temperature on the photolysis of the polyphosphazene substrate in film is also reported.

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.

The aim of this study was to evaluate polyurethane percutaneous endoscopic gastrostomy (PEG) tube degradation and the role played by fungi. The inner surfaces of 20 used polyurethane tubes were brushed, and the brushing end was incubated for 7 days in Saburaud broth and cultured if fungal growth occurred. Three tubes used for 12 (sample 12w), 17 (sample 17w), and 96 (sample 96w) weeks and two new tubes were cut to produce several 4-cm-long equal halves. Six samples from the new tubes were considered control samples (Co sample), seven were incubated in Saburaud broth (Co sample + Sa.), and seven in the broth supplemented with Candida albicans (Co sample + Sa. + Ca). All samples underwent morphological examination by electron microscopy and differential scanning calorimetry measurements (DSC). All tubes had fungal colonization. DSC showed deterioration in all tubes including the new ones; adding Candida albicans had no additional effects. Morphological examination by electron microscopy showed a regular pattern in the Co sample, and thick biofilm, holes, and crevices in samples 12w, 17w, and 96w. The more the tubes had been used, the more severe were the changes. The Co sample + Sa and the Co sample + Sa + Ca showed no changes in the inner surface, but cryogenically fractured surfaces had holes and crevices. Yeasts constantly colonize PEG tubes and are likely to contribute to polyurethane deterioration. The impairment of new PEG tubes incubated in Saburaud broth suggests that other factors also play a role in polyurethane deterioration.

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.

Four different types of montmorillonites have been dispersed by sonication at 50 8C 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 8C by following the disappearance of the isocyanate vibrational band found at 2 270 cm1. 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 cm1 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.

Optical 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.

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 .

Innovative polymeric films based on blends of nylon 6 and ethylene-co-vinyl alcohol, previously tested by contact with the simulating fat-containing foods, were further tested as packaging for fresh minced meat. As quality attributes for the shelf-life evaluation, the microbiological parameters and some chemical–physical parameters were chosen. The changes that occurred during the evaluation period of 6 days were monitored by several means on both the polymer films and the fresh meat. The results suggest that the barrier properties of the polymeric films were shown to play a determinant role in the lipid oxidation, thus confirming the previous evaluation of the simulating foods. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 93: 23–29, 2004

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.

The Raman and i.r. spectra of 1,1′-diphenylethene and the low-frequency spectra of benzophenone, diphenylketimine, diphenylmethane and diphenylether have been reinvestigated in order to attain a consistent attribution of the characteristic vibrations of geminal diphenyl substitution. Most of the internal vibrations of the benzene rings were seen in pairs of bands with very close frequencies, corresponding to symmetric (in-phase) and asymmetric (out-of-phase) modes. Of those monosubstituted-benzene vibrations usually considered to be sensitive to substitution, ν 13 , ν 6a and ν 16b were found to span a narrow frequency interval, with a separation of 10–20 cm −1 between the respective symmetric and asymmetric modes. On the contrary, quite far apart frequencies were attributed to the symmetric and asymmetric modes of the vibrations ν 1 , ν 9b and ν 10b ; for these, frequency separations ranging from about 50 to 140 cm −1 were found, with a pronounced dependence of the covered spectral interval on the nature of the central group. The presence of a very strong Raman band at 90—80 cm −1 was the most striking spectral characteristic for all of the molecules under consideration: it was attributed to the PhXPh angle bending vibration, although considerable mixing of it with other low-frequency vibrations was considered likely. Based on internal potential energy functions computed by a semi-empirical method (C-INDO), an approximate calculation of the frequencies for the conrotatory torsion of Ph 2 CCH 2 , PH 2 CO and Ph 2 O and both torsions of Ph 2 CH 2 was performed, so as to predict their relative magnitude and to assist the interpretation of the spectra in the lowest region. I.r. bands observed at 55 and 70 cm −1 for Ph 2 O and Ph 2 CO, respectively, might be considered for assignment to torsional vibrations.

Rotational isomerism in styrylnaphthalenes has been investigated by Raman vibrational spectroscopy. Evidence was found for the existence of two rotational, s-trans and s-cis, isomers in solutions of trans-2-styrylnaphthalene, and by analysis of the temperature dependence of relative band intensities an enthalpy difference of 0.71 ± 0.07 kcal mol–1 was derived for the equilibration reaction. Only one form was found for trans-1-styrylnaphthalene, where one of the two corresponding isomers is hindered by strong steric interactions. The results of this work greatly increase the evidence for conformational equilibria in trans-1,2-diarylethylenes previously obtained by fluorescence studies as well as predicted by molecular-orbital calculations.

The crystal structure and vibrational analyses of melamine hydrobromide by FTIR and FT-Raman spectra, are presented. The crystallographic data show π-electron delocalization towards the amino substituents with ring nitrogen protonation in the solid state. Additionally, the presence of intermolecular hydrogen bonding interactions occurring between amino substituents and ring nitrogen lone-pairs gives rise to charge–transfer complexes, as demonstrated by UV–VIS reflectance in the solid state. FTIR and FT-Raman spectra allow the assignments of the vibrational modes in melamine hydrobromide by comparison with the corresponding deuteriated molecules, and show the existence of iso-melamine cations in the solid state.

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.