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A sample of pure poly(β-hydroxybutyrate) (PHB) and a sample of poly(β-hydroxybutyrate-co-β-hydroxyvalerate) [P(HB-co-HV)] with a composition ratio HB/HV of 87: 13 were investigated by different degradation methods: (a) direct pyrolysis-mass spectrometry; (b) fast atom bombardment mass spectrometry (FABMS) analysis of the partial pyrolysis products; (c) FABMS analysis of the partial methanolysis products. The pyrolysis products originating from the two microbial polyesters are shown to be thermally labile, so that oligomers higher than the trimer cannot distil undecomposed and remain undetected by electron impact or chemical ionization MS. However, the pyrolysis products can be desorbed by FABMS up to the decamer level. With the partial pyrolysis method it is not possible to obtain reliable composition and sequence distribution data, which may, however, be obtained by the FABMS analysis of the partial methanolysis products of the two samples investigated.

The thermal fragmentation processes in poly-Schiff bases have been investigated by direct pyrolysis–mass spectrometry. The mass spectral data show that the thermal fragmentation occurring in the polymers under investigation is characterized by hydrogen transfer reactions. In the case of a totally aromatic poly-Schiff base (polymer I), the thermal fragmentation process involves hydrogen transfer irom the methyne group with formation of fragments bearing nitrile and/or phenyl end groups. In the case of aromatic-aliphatic poly-Schiff bases (polymers II–IV), the hydrogen transfer process occurs from the aliphatic methylene groups. The latter process involves a lower energy and therefore occurs at lower temperatures with respect to the totally aromatic polymer I, with formation of thermal fragments bearing olefin and/or imine end groups. Beside these fragments, several thermal fragmentation compounds are also evolved by multiple hydrogen transfer reactions.

The influence of ammonium polyphosphate (APP) on the smoke emission of poly(acrylonitrile) (PAN) has been examined, and its mechanism of action as a smoke suppressant agent has been investigated. Smoke density and corresponding residual char data, as a function of temperature, were obtained in order to characterize the smoke propensity of PAN. The amount of generated smoke, both in smoldering and flaming conditions, was considerably lowered by the presence of APP, and higher char yields were obtained. Beside the smoke suppression, flame inhibition effect of APP on PAN was evidenced. Thermogravimetry (TG), oxygen index (OI), and nitrous oxide index (NOI) experiments were also performed. On the basis of our data, APP appears to act as a char-forming agent in PAN combustion. Both smoke suppression and flame inhibition effects can be considered a consequence of this action.

The primary thermal decomposition mechanism of poly(ethylene oxalate) (PEO) has been investigated by pyrolysis-mass spectrometry. Several mass spectrometric techniques have been used in order to identify compounds present in the pyrolysis mixture: comparison of electron impact and chemical ionisation spectra, high resolution accurate mass measurements and tandem mass spectrometry (daughter and parent ion spectra). The results obtained indicate that intramolecular exchange reactions predominate in the primary thermal fragmentation processes yielding cyclic oligomers up to tetramer. No other pyrolysis products were detectable under our experimental conditions. PEO, prepared by condensation polymerisation, was shown by 1 H-NMR to contain up to 7% of diethyleneglycol (DEG) units along the polymer chain. A small amount of cyclic oligomers containing DEG units was detected among the pyrolysis products from PEO.

The thermal degradation mechanism of three aromatic polysulfonates and polythiosulfonates was investigated by direct pyrolysis in the ion source of a mass spectrometer. Thermal degradation reactions were followed directly by this method by detecting the thermal and electron impact induced fragments. The results obtained have provided evidence that sulfur dioxide extrusion from the polymer backbone takes place in these polymers above 300°C. The synthesis and molecular characterization of the polymers studied are reported in the text.

The low energy (13 eV) electron-impact and field desorption mass spectra of some photodimers of cinnamic acid and related compounds containing the cyclobutane ring are reported and the fragmentation patterns analysed in order to obtain stereochemical information on the substituent position on the cyclobutane ring. Both symmetrical and asymmetrical splittings of the cyclobutane ring were detected, allowing characterisation of the head-to-head and head-to-tail structures of the title compounds. A ring opening rearrangement of the McLafferty type was also found.

The behaviour under electron impact of two series of isomeric cyclopentane- and cyclohexane-1, 2- and -1, 3-dicarboxylic acid dipiperidides was studied. Diagnostic fragmentation pathways were found to differentiate the isomeric diamides. Additional evidence was obtained from the metastable transitions.

The thermal behaviour of copolymers of acrylonitrile containing up to 15 wt.-% of methyl acrylate (MA), methyl methacrylate (MMA), vinyl acetate (VA), and vinyl bromide (VB) units, was investigated by gradually increasing the temperature of a polymer sample placed in the ion source of a mass spectrometer (MS). The resulting pyrolytic processes (time-temperature resolved) were analyzed by detecting the volatile decomposition products formed. Several decomposition processes were ascertained. Bromine derivatives evolution from the VB copolymer chain occurs already at 160–200°C. The thermal decomposition of the pendant ester groups in the MA and MMA copolymers occurs in the temperature range of 200–260 °C. Typical polyacrylonitrile (PAN) decomposition fragments were detected in the 240–300 °C range in all the copolymers investigated. Acetic acid units are evolved from the VA copolymer simultaneously to the PAN thermal fragments. Heterocyclic compounds originated from the ladder structures appear beyond 300°C.

Poly(ϵ-caprolactam) (PCL) with improved flame-retardant (FR) properties can be easily obtained by activated anionic polymerization of the monomer, ϵ-caprolactam (C), in the presence of adequate amounts of red phosphorus (red P). Analogous results with reduced P content can be achieved by coupling red P with a synergistic compound such as a chlorinated hydrocarbon or magnesium oxide (MgO). A peculiar advantage of this method is the possibility of obtaining a very fine and homogeneous dispersion of the FR additive in the polymer matrix, meanwhile avoiding the typical compounding techniques, which are expensive, often unsafe, and require melt mixing of the ingredients. Molecular, thermal, and mechanical characterization, as well as morphology of the resultant products, have been determined: No significant properties change have been found when FR agents are present, apart from the relevant improvement of the flame-resistance. Thus, by this novel procedure it is possible to prepare FR poly-(ϵ-caprolactam) without any appreciable deterioration of its typical properties.

Etude des polyesters macrocycliques obtenue par polycondensation du dibutyl-2,2 dioxastannolane-1,3,2 avec les chlorures des acides sebacique, adipique, glutarique et oxy- bis acetique. Les melanges obtenus sont des distributions d'oligomeres cycliques qui montrent l'absence de selectivite pouvant resulter d'un effet de matrice de l'etain

Carbon-13 n.m.r. chemical shifts are reported for diphenylmethane and nine methylated derivatives. Results are compared with those for related methylbenzenes. In the case of tri-ortho-substituted materials the predominance of a perpendicular conformation is suggested. Ring current calculations show that in contrast to the 1H chemical shift interpretations, the 13C shielding trends cannot originate primarily from anisotropic effects.

Collisionally activated decomposition (CAD) linked scan mass spectra have been used in the identification of pyrolysis products obtained by the direct pyrolysis of some polysulphides in a mass spectrometer. Structures were determined by comparing the CAD spectra of the pyrolysis products with those of authentic compounds. The results are of help in elucidating the thermal degradation mechanisms that occur in the pyrolysis of the polysulphides investigated.

The thermal fragmentation processes in L-Proline—Sarcosine and in L-Proline—L-Alanine copolymers have been investigated by direct pyrolysis—mass spectrometry. The mass spectral data show that proline—sarcosine copolymers decompose in three steps, yielding cyclic oligomers. The first step is characterized by the presence of the Sar—Sar, Sar—Pro, and Pro—Pro cyclic dimers. In the second step the formation of several series of cyclic oligomers up to nonamers—decamers can be observed, while the third step of thermal decomposition process leads to the almost exclusive formation of Pro—Pro cyclic dimer. The proline—alanine copolymers, instead, show a single-step thermal degradation process leading to the formation both of cyclic oligomers and compounds with olefin and nitrile end-groups. Our results show that the thermal decompostion of alanine units is affected by the neighboring units along the polymer chain. Sarcosine units act as thermally labile probes, causing the selective thermal cleavage of the Pro—Sar copolymer.

Polycondensation between bis(2-hydroxymethylenephenyl)adipate, bis(3-hydroxypropylene)terephthalate and bis(2-hydroxyethylene)terephthalate with α-truxilloyl chloride were performed to obtain exactly alternating copolyesters containing photoreactive cyclobutane units in the main chain. The resulting copolyesters were characterized by fast-atom bombardment (f.a.b.) mass spectrometry, and the structure of the oligomers detected in the f.a.b.(+) and f.a.b.(−) mass spectra allowed confirmation of the alternating sequence present in the copolymers.

Cas du polyethyleneterephtalate et d'un copolyester statistique contenant 20 mol% d'unites α-truxillique et 80 mol% d'unites terephtalique le long de la chaine principale

The LPTD-MS method, used to determine kinetic parameters in the thermal degradation of polymers by means of volatilization curves, was applied to TG data and the results were compared with those obtained by the methods of Flynn & Wall, Friedman, Freeman & Carroll, and Coast & Redfern.

The thermal degradation of three aliphatic polythiocarbonates was investigated by direct pyrolysis in the ion source of a mass spectrometer operating both in electron and chemical ionization modes. The overall evidence indicates that these polymers start decomposing at about 250–280°C by an end-biting process initiating from the SH end-groups, which produces a mixture of cyclic sulfides, disulfides, and dithiocarbonates. Another decomposition step is observed at higher temperature (ca. 350–370°C), producing essentially the same compounds evolved in the first stage, but with significant differences in their relative abundances. An intramolecular exchange (back-biting) process is believed to be responsible for the second thermal decomposition stage

Thermal stability and flammability properties of six structurally related vinyl and vinylidene polymers fail to show correlation. Instead, it is found that the combustion of these polymers is dominated by their char-forming ability. A remarkable intumescent effect is observed in PVC2, PVF2, and PVC which accounts for the high flame extinguence of these polymers.

Der thermische Abbau von Poly(oxy-1,4-phenylen), Poly(thio-1,4-phenylen) und Poly(dithio-1,4-phenylen) wurde durch direkte Pyrolyse in der Ionenquelle des Massenspektrometers untersucht. Bei verringerter Elektronenenergie (15 eV) konnten die elektronenstosinduzierten Fragmentierungen der Pyrolysebruchstucke weitgehend zuruckgedrangt und die thermischen Abbaumechanismen ermittelt werden. In Abhangigkeit von den Bruckenatomen werden charakteristische Unterschiede im Abbauverhalten und in der Art der gebildeten Bruchstucke gefunden. Am Beispiel des Poly(dithio-1,4-phenylen)s kann gezeigt werden, das temperaturprogrammierte Pyrolyse und Verwendung eines Datensystems zur Ermittlung von thermischen Massenfragmentogrammen geeignet sind, mehrere Abbaureaktionen am Polymeren direkt zu verfolgen. The thermal degradation reactions of poly(oxy-1,4-phenylene), poly(thio-1,4-phenylene), and were studied by direct pyrolysis in the ion source of the mass spectrometer. The use of a reduced ionization energy (15eV) allows to suppress the electron impact induced fragmentation reactions of the pyrolytic fragments and, thus, to ascertain the thermal degradation mechanisms. Characteristic differences in the thermal degradation behaviour and the fragment species formed in pyrolysis were found, in dependence on the bridging groups. By the example of Poly(dithio-1,4-phenylene), it could be shown that a temperature-programmed pyrolysis and the use of a data system for the acquisition of thermal ion chromatograms are appropriate to identify directly different polymer degradation reactions.

The primary thermal decomposition processes of a series of aliphatic polyamides were investigated by Direct Chemical Ionization (DCI) and Tandem mass spectrometry. Results show that an intramolecular exchange process is the preferred thermal decomposition mechanism for many of the polyamides. Decomposition through a C-H hydrogen transfer reaction appears to occur as a secondary thermal process, except in the case of nylon 3 because of its particular structure. A quite different decomposition pathway is followed by nylons from adipic acid (nylons 6.6 and 11.6), where specific structural factors make the formation of cyclopentanone preferred. These polymers decompose via a C-H hydrogen transfer to nitrogen with the formation of compounds having amine and/or ketoamide end groups. These primary products further decompose or react with the formation of cyclopentanone and compounds bearing amine and/or Schiff base groups.

The thermal decomposition processes of some aromatic-aliphatic polymides, derived from terephthalic acid and aliphatic diamines, were studied by flash Pyrolysis-GCMS and by direct Pyrolysis-Mass Spectrometry, using both Chemical lonization and Electron Impact modes. The results indicate that the primary thermal decomposition proceeds via a β-CH hydrogen transfer process, with formation of pyrolysis products containing amide and olefin end-groups. Nitrile end-groups are also formed by dehydration of the amide groups formed in the primary decompostion process.

The incorporation of a poly[ferrocene-1, 2 (1, 3: 1, 1′)diylmethylene] fraction with Mn=2100 as a smoke suppressant additive into both unplasticized and di(2-ethylhexyl)phthalate-plasticized, calcium carbonate-filled poly(vinyl chloride) (PVC) compositions entails appreciable reductions in smoke evolution during combustion tests relative to unmodified formulations. Best results, with smoke density reductions in the range 25-80%, are obtained at the 3% loading level, with higher additive concentrations causing no further improvements. The findings of this study may have implications on the design of other polymeric engineering materials exposed to potential fire hazards.

A comparative approach to the determination of smoke emission from burning polymers has been attempted, and a number of combustion conditions and detection devices have been tried to choose a test method for measuring the smoke proiduction of materials. The combustion apparatus adopted is a hot-air quartz furnace that permits the measured by dynamic method from combustion of PAN, PVC and PVC mixed with some metal oxiders, have been compared with those obtained by an accumulation mode. For PVC the intensity of the light scattered from the evolving smoke has been measured as an alternative to smoke density.

Surface-enhanced Raman scattering (SERS) was used to characterize thin films of poly(α-methylstyrene) (PMS) spin-coated onto silver island films supported by glass substrates. At laser powers of a few tens of milliwatts, SERS spectra of thin films of PMS (about 100 A) were weak, and only the bands near 1010 and 1040 cm−1 were observed. At laser powers of about 100 mW, additional bands characteristic of PMS were observed near 720 and 1610 cm−1. However, oxidative degradation of the PMS films to form graphite-like substances was also observed at the higher laser powers. When the thickness of the PMS films was increased to several hundred angstroms, degradation of the films was inhibited, but the intensity of the Raman scattering remained constant, indicating that the observed SERS was an interfacial rather than bulk effect. Degradation during SERS experiments was also inhibited by overcoating PMS films with much thicker films of poly(4-styrene sulfonate) (PSS). Scattering from the PSS overlayers was not observed as long as the thickness of the PMS films was greater than several tens of angstroms, again showing that the SERS was an interfacial effect. Oxidative degradation of the PMS films was also inhibited by adding a few percent of the antioxidant 2,6-di-tert-butyl-4-methylphenol to the polymer. Bands related to sulfite contaminants adsorbed onto the silver island films were observed near 640 and 940 cm−1. These bands disappeared when PSS, but not PMS, was spin-coated onto the SERS substrates, indicating a strong interaction between PSS and silver.

This work is concerned with the mass spectrometric characterization of polyaryloxy- and polyaminophosphazenes 1a–e. The mass spectral data show that the pyrolytic breakdown of poly(di-β-naphthoxyphosphazene) (1a) leads to the formation of cyclic oligomers. The poly(di-arylaminophosphazenes) 1b–d decompose at low temperatures by a two-stage process involving amine evolution. Finally, in the case of poly(dipiperidinophosphazene) (1e) the thermal decomposition leads to the complete destruction of the polymer backbone, with formation of ammonia and elemental phosphorus. The wide range of thermal decomposition pathways observed are peculiar of the phosphazene structure and represent a remarkable difference between this class of inorganic polymers and the organic ones.

The mechanism of action of aromatic sulfonates as flame retardant (FR) agents on poly(bisphenol-A carbonate) (PC) has been investigated. These compounds are capable of inducing a self-extinguence in PC even when present in very low amounts (0.2–1%). Thermogravimetric and flash pyrolysis–GC–MS data show the thermal degradation rate of PC enhanced, and the distribution of the volatile pyrolysis products was modified by these additives. Oxygen Index (OI) and Nitrous Oxide Index (NOI) measurements indicate a FR condensed-phase mechanism of these additives. Traces of polymer surface temperature against time, measured under forced flame conditions, show that the expanded carbon layer formed in the combustion of polycarbonate–aromatic sulfonate blends produces a heat insulating effect toward the undecomposed bulk. The overall evidence leads us to conclude that aromatic sulfonates cause the flame extinguishment in polycarbonate by an intumescent phenomenon.

Carbon-13 n.m.r. chemical shifts for 8 anisoles and 15 diphenyl ethers are reported. para-Carbon shieldings are found to be sensitive to the degree of steric interference to conjugative electron release by the ethereal oxygen atom. An empirical correlation between the para-carbon shifts and the average twist angle of the phenyl rings from a reference plane has been developed. Satisfactory agreement has been found between the angles of twist derived from carbon chemical shifts and those based on other physical measurements.

The analysis of polymers by direct mass spectrometry is reviewed, and the principles of the method and some experimental aspects are discussed. Both pyrolysis and desorption methods are described. The mass spectrometric method provides the characterisation of intractable materials and their detection at the submicrogram level; the simultaneous identification and detection of additives or oligomers contained in polymer samples; the identification of components of polymer mixtures, the sequential analysis of copolymers; the identification of the primary thermal fragmentation products of polymers. Direct mass spectrometry has been widely applied to the structural analysis of synthetic and natural polymers. Published work covers nearly all classes of polymers.

The thermal degradation mechanism of three aromatic polymers containing double bridged phenylether units was investigated by direct pyrolysis in the ion source of a mass spectrometer. Thermal degradation reactions were followed directly by this method detecting the thermal and electron impact induced fragments. The results obtained have provided evidence that the double bridge between the aromatic rings is the preferred fragmentation site in these polymers. Furthermore in the double sulfur bridged polymer III, extrusion of S2 from the polymer backbone takes place above 400°C. The synthesis of polymers studied is reported in the text. Der Mechanismus des thermischen Abbaus von drei aromatischen Polymeren aus Phenylather-Einheiten, die uber zwei hintereinanderliegende Gruppen verbunden sind, wurde durch direkte Pyrolyse in der Ionenquelle eines Massenspektrometers untersucht. Die erhaltenen Ergebnisse machen deutlich, das die aus zwei Gruppen bestehende Brucke zwischen den aromatischen Ringen die bevorzugte Spaltungsstelle in diesen Polymeren ist. Beim S–S-uberbruckten Polymeren III wird oberhalb 400°C S2 aus der Polymerkette abgespalten. Die Synthese der untersuchten Polymeren wird beschrieben.

Identification des oligomeres cycliques formes dans la polycondensation conduisant aux polysulfures aromatiques, aliphatiques et aliphatiques-aromatiques. Formation de complexes entre les sulfures cycliques extraits et les sels des metaux lourds (Ag, Hg et Cu)

Direct pyrolysis in the mass spectrometer yielded evidence on the mechanisms of thermal decomposition of N-monosubstituted and N-disubstituted polyurethanes. Our results indicate that N-monosubstituted polyurethanes undergo quantitatively a depolycondensation process, producing diisocyanate and diol. In contrast, disubstituted polyurethanes decompose to give selectively secondary amine, olefine and CO2.

Etude par thermogravimetrie et pyrolyse directe dans un spectrographe de masse. L'addition de polyphosphate diminue la stabilite thermique de polyurethannes N-substitues, il se produit un clivage de la chaine polymere et des amines tertiaires peuvent se former

The thermal decomposition of structurally related N–H and N,N′-disubstituted polyureas (Table I) and their mixtures with ammonium polyphosphate (APP) was investigated by thermogravimetry (TG) and direct pyrolysis in a mass spectrometer (MS). The N–H polyureas (IV–VI) undergo a quantitative depolymerization process with the formation of oligomers with amine and isocyanate end groups. In contrast, the thermal degradation of the N,N′-disubstituted polyureas (I–III) proceeds by a different mechanism as a function of their chemical structure. The addition of APP lowers the thermal stability of the N,N′-disubstituted polyureas, whereas that of the N–H polyureas is unaltered. However, our data show that APP does not change the nature of the pyrolytic products. The destabilizing effect of the additive can be attributed to the catalytic action of the acid species formed by its thermal decomposition.

A topological approach to the LIS simulation process of compounds bearing the carbonyl functional group is reported. The Lanthanide was always found to complex in the less hindered position, along the sp 2 lone-pair orbital of the O atom. The relevance to chemistry of such an approach is that only chemical significant positions are considered as feasible sites of complexation of the Lanthanide with the substrate, disregarding all other positions. More important, the results obtained have thrown some light on the factors that may influence the equilibria of conformationally mobile systems, in the presence of LSR. The reliability of the method employed has been tested in several disparate carbonyl derivatives.

Computer simulation of the lanthanide induced shifts has been applied to study of the conformational preferences in the 2-formyl and 2-acetyl derivatives of furan, thiophene, selenophene and tellurophene. The results assign a nearly equipopulated mixture of s-cis and s-trans conformers to the furan, and a preponderance of the s-trans form to the thiophene, selenophene and tellurophene derivatives. This difference is interpreted as due to the interaction between the heteroatom and carbonyl oxygen lone pairs. The 2-N,N-dimethylcarboxyamide derivatives of furan, thiophene and selenophene are found to exist mainly in a quasi-planar s-cis form. The barriers to the rotation about the amide bond in these amides have been measured and related to the electronegativity of the heteroatom.

Fast atom bombardment (FAB) mass spectrometry was applied to the analysis of two polyesters, poly(ethylene adipate) and poly(epsilon-caprolactone), and two polyamides, Nylon 6.6 and Nylon 6. The peaks present in the spectra of the crude polymers were identified as corresponding to protonated molecular ions of preformed cyclic oligomers and of low molecular weight compounds contained in the polymer samples; these species were desorbed intact from the glycerol matrix under FAB conditions. When the polymers investigated were accurately purified from low molecular weight compounds, no significant peaks were observed in their FAB mass spectra. Instead, the FAB mass spectra of the mixtures extracted from the polymers were found to be very similar to those obtained for crude polymers.

Elemental red phosphorus was found to be an efficient flame retardant for poly(acrylonitrile) homopolymer (PAN) and, to a lesser extent, also for a modified acrylic resin containing 36 wt.-% of vinylidene chloride (VC2) as comonomer. The data collected show that condensedphase and gas-phase mechanisms are both responsible for the flame inhibition effect of red phosphorus on PAN. On the contrary, a gas-phase mechanism seems to be responsible for the flame inhibition effect of red phosphorus on the AN-VC2 copolymer. Flash-pyrolysis GC data, with pyrolysis products MS identification, are reported for both polymers studied.

The thermal decomposition processes of two polyamides, derived from succinic acid and two aromatic diamines, were studied by direct pyrolysis mass spectrometry. Fast atom bombardment (FAB) mass spectrometry has been also used in order to provide additional information for the elucidation of the thermal degradation mechanism of the polymers investigated. FAB mass spectra, obtained by introducing in the FAB ion source the solid residues from polymer pyrolysis performed in thermogravimetric experiments, allowed the detection of diagnostic compounds up to about 1600 amu. Our results indicate that the thermal stability of the N-methyl-substituted polyamide is higher than that of the unsubstituted polyamide. The difference in the thermal degradation mechanism accounts for the difference in the thermal stability of the two polyamides. In fact, the unsubstituted polyamide decomposes via an intramolecular exchange and a concomitant NH hydrogen transfer process with formation of compounds with amine and/or succinimide end groups. Instead, the N-methyl-substituted polyamide decomposes via an α CH hydrogen transfer process from the methyl group to the nitrogen atom with formation of compounds with amine and/or 2,5-piperidinedione end groups.