IR laser ablative decomposition and depolymerisation/repolymerisation of poly(ethylene succinate)

Pulsed IR laser ablation of poly(ethylene succinate) results in the formation of volatile products (mainly carbon oxides, hydrogen, C₁-C₄ hydrocarbons) and affords deposition of polymeric films. Composition, structure and molecular weight distribution of the latter products were examined by EDX-SEM, FTIR, UV and NMR spectroscopy and gel permeation chromatography and revealed to be virtually identical to the initial poly(ethylene succinate). The deposited films and poly(ethylene succinate) decompose in the same way, as proved by TGA analysis. The formation of the volatile products is accounted for by random cleavages of the polymer backbone. The deposition of the polymeric products is judged to be due to molecular ester group interchange and/or a sequence of the C-C bond homolysis and recombination of the produced radicals.     

Influence of free and copolymerized triplet quenchers on the photolysis of poly(vinyl phenyl ketone) in solution

The influence of free, diffusion-control quenchers of triplets (naphthalene, biphenyl, 2,5-dimethyl-2,4-hexadiene) on the photolysis of poly(vinyl phenyl ketone) in benzene solution has been investigated. The Stern-Volmer plots for quenching of main-chain scission were linear, and the quenching constants were independent of the macroviscosity of the solutions. Copolymers of vinyl phenyl ketone with 1-vinylnaphthalene and 2-vinylnaphthalene containing as much as 10% (by weight) vinylnaphthalene were prepared. The photolysis of the copolymers was compared with the photolysis of poly(vinyl phenyl ketone) in the presence of free naphthalene. It was found that the quenching efficiency of found naphthalene units was about 21 times higher. The possibility of migration of the absorbed energy along the polymer chain is discussed. The relation between average-number molecular weight M _n and intrinsic viscosity [η] has been determined osmometrically. For unfractionated poly(vinyl phenyl ketone) in benzene at 30°C, the relation [η] = 2.82 × 10^?5 M _n^0.84 has been found.     

IR laser ablative decomposition of poly(vinyl acetate) loaded with Fe and Cu particles

Pulsed IR laser-induced decomposition of poly(vinyl acetate) (PVAC) loaded with nanometer-sized Cu and micrometer-sized Fe particles results in the formation of gaseous products and deposition of polar crosslinked polymer films which contain metal (Cu and Fe) particles. The main volatile products are hydrocarbons, carbon oxides (CO and CO₂), molecular hydrogen and acetic acid. The deposited polymer films were characterized by FTIR, UV and XP spectra and by electron microscopy and thermogravimetry. They contain reactive conjugated CC bonds and ca. 50% of the initially present acetate groups. Residual reactivity of the CC bonds results in polymer crosslinking and decrease in solubility. The deposited, crosslinked PVAC-based films containing metal particles are less thermally stable than similar films not containing these particles. The reported process reveals feasible ablation of metal particles when embedded in a polymer and makes it possible to fabricate films of metal/polymer composites in which metal particles are completely protected by the polymer.     

IR laser-induced decomposition of poly(vinyl chloride-co-vinyl acetate): Control of products by irradiation conditions

IR laser-induced, ablative decomposition of poly(vinyl chloride-co-vinyl acetate) was examined under different irradiation conditions and its volatile and solid products were characterized by mass spectroscopy, infrared spectroscopy, Raman spectroscopy and UV spectroscopy and EDX-measurements. The laser decomposition of the copolymer, compared with that of poly(vinyl acetate) and poly(vinyl chloride), is revealed to be a more efficient process leading to solid films with the proportion of Cl- and CH₃C(O)O-groups controlled by irradiation conditions.     

Poly(imino imino ether ether ketone ketone) as novel soluble heat-resistant polymer

In this paper, we introduce a novel high-performance polymer, poly(imino imino ether ether ketone ketone), which has been synthesized by the palladium-catalyzed C-N cross coupling reaction of 1,4-bis-(4-bromobenzoyl) benzene and 1,3-bis-(4-aminophenoxy) benzene. The structure of the polymer is characterized by means of ¹H NMR spectroscopy and elemental analysis, and the results show a good agreement with the proposed structure. Compared with traditional poly(ether ether ketone)s, the solubility of the synthesized polymer in common organic solvents was higher; it also exhibited high glass transition temperature (T _g = 176°C) and good thermal stability with high decomposition temperature (T ₅ = 400°C).     

IR laser ablation of poly(vinyl chloride): Formation of monomer and deposition of nanofibres of chlorinated polyhydrocarbon

IR laser-induced ablation of poly(vinyl chloride) was examined under different irradiation conditions and its volatile and solid products were characterized by mass, infrared, UV and X-ray photoelectron spectroscopy, electron microscopy and thermogravimetry. It is demonstrated that the major component among the volatile products is monomeric vinyl chloride and that the process causes deposition of Cl-containing polymeric films. The proportion between the volatile and solid products as well as the nature of the deposited films at different laser fluences have been examined. We show that the deposited films incorporate less Cl atoms than poly(vinyl chloride) and that they initially contain conjugated CC bonds and incorporate nano-sized fibre and necklace features. The process represents the first example of thermal degradation of poly(vinyl chloride) into monomer and makes it possible to fabricate crosslinked Cl-containing intractable polymer films.     

Synthesis of Block Copolymers and Asymmetric Star-Branched Polymers Comprised of Polyacetylene and Polystyrene Segments via Ionic Bond Formation

Novel ion-bonded AB diblock copolymers and three-arm AB₂ asymmetric star-branched polymers comprised of polyacetylene (A) and polystyrene (B) segments have been synthesized by the stoichiometric reaction of tert-amine-chain-end-functionalized poly(phenyl vinyl sulfoxide)s with either chain-end- or in-chain-carboxylated polystyrenes to link the two polymer segments via ionic bond, followed by thermal treatment to convert their poly(phenyl vinyl sulfoxide)s to polyacetylene segments. Periodic lamellar morphologies were observed in the cast films of such polymers by TEM measurement. The isolation of the nano-size sheet consisting of polyacetylene lamellar layers was attempted.     

IR laser ablative degradation of poly(phenylene ether-sulfone): Deposition of films containing ether, sulfone, sulfoxide and sulfide groups

Pulsed infrared laser-induced ablation of poly(1,4-phenylene ether-sulfone) (PES) results in the extrusion of SO₂, CO and hydrocarbon molecules and allows deposition of dark solid paramagnetic carbonaceous films that were analysed by FTIR, UV, XP, Raman and EPR spectroscopy and by electron microscopy and revealed as poor in S and containing CO, SO₂, -SO- and C-S-C units. The films show pronounced conjugation of sp²-C atoms and their EPR spectra are sensitive function of the presence of molecular oxygen. The laser process differs from the conventional pyrolysis of PES which yields SO₂ and phenol as major volatile products and a carbonaceous char.     

Synthetic transformations of higher terpenoids: XXXII. Synthesis of 16-alkenyl-substituted labdatrienes by oxidative coupling of methyl phlomisoate with alkenes

Reactions of methyl phlomisoate with methyl acrylate, phenyl acrylate, methyl vinyl ketone, phenyl vinyl ketone, or N-substituted acrylamides catalyzed by Pd(OAc)₂ in the presence of Cu(OAc)₂, p-benzoquinone in the mixture of propionic acid and acetonitrile proceed regio- and stereoselectively with the formation of (E)-16-vinyl labdatrienoates. The oxidative coupling under these conditions of the methyl phlomisoate with styrene results in a mixture of 15,16-distyryl-, 16-styryl-, and 16-(1-phenylvinyl)-derivatives of furanolabdanoid.     

Synthesis of Block Copolymers and Asymmetric Star-Branched Polymers Comprised of Polyacetylene and Polystyrene Segments via Ionic Bond Formation

Summary. Novel ion-bonded AB diblock copolymers and three-arm AB₂ asymmetric star-branched polymers comprised of polyacetylene (A) and polystyrene (B) segments have been synthesized by the stoichiometric reaction of tert-amine-chain-end-functionalized poly(phenyl vinyl sulfoxide)s with either chain-end- or in-chain-carboxylated polystyrenes to link the two polymer segments via ionic bond, followed by thermal treatment to convert their poly(phenyl vinyl sulfoxide)s to polyacetylene segments. Periodic lamellar morphologies were observed in the cast films of such polymers by TEM measurement. The isolation of the nano-size sheet consisting of polyacetylene lamellar layers was attempted.     

IR laser ablative degradation of poly(ethylene terephthalate): Formation of insoluble films with differently bonded CO groups

IR laser-induced degradation of poly(ethylene terephthalate) (PET) was studied under different irradiation conditions and the ablated volatile and solid products were characterized by mass and infrared spectroscopy, gel-permeation chromatography, thermogravimetry and electron microscopy. The observed volatile products (carbon oxides, H₂, C_1-2 hydrocarbons, acetaldehyde, benzene and toluene) and less-volatile aromatic compounds are typical products of thermal degradation of PET. The ablatively deposited solid materials are a blend of soluble, structurally similar oligomers and of an insoluble polymer containing carbonyl groups bonded in a -C(O)OH arrangement. Thermal degradation of these deposited solids is controlled by decomposition of sublimed fractions and is easier than that of PET.     

Network formation of a phenyl vinyl ketone copolymer with 4-vinylbenzil and its photodecrosslinking in films

The irradiation (λ > 400 nm) in air of a copolymer of phenyl vinyl ketone with 4-vinylbenzil (VBZ) containing 1.5 wt % VBZ structural units in film, followed by the thermal decomposition of the resulting pendant benzoyl peroxide groups, leads to crosslinking. The subsequent irradiation of the crosslinked polymer at 366 nm results in the cleavage of the poly(phenyl vinyl ketone) chain between the junction points of the polymer network through a Norrish type II reaction. Therefore, poly(phenyl vinyl ketone-co-4-vinylbenzil) represents a novel type of photoresist based on polymer network decrosslinking. The process involves three steps: photogeneration of peroxide, crosslinking by its thermal decomposition, and subsequent photodecrosslinking of the polymer network. This material provides positive-tone images after UV exposure (λ > 330 nm) and development in an organic medium such as isopropyl methyl ketone. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 765–771, 2004     

N-(Substituted phenyl) itaconimides as organic stabilizers for plasticized poly(vinyl chloride) against photo-degradation

Several N-(substituted phenyl)itaconimide derivatives, N-(RPh)II (R: -NO₂, -COOH, -H, -OH, -OMe, -Me, -Cl, or -Br), have been investigated as organic photo-stabilizers for poly(vinyl chloride) (PVC) plasticized with dioctyl phthalate (DOP). Their stabilizing efficiencies are evaluated by measuring the length of the induction period (Ts), the period during which no detectable amounts of hydrogen chloride gas could be observed, and also from the rate of dehydrochlorination as measured by continuous potentiometric determination, and the extent of discolouration of the degraded polymer. The efficiencies are also evaluated by determining the amount of gel formation as well as the intrinsic viscosity of the insoluble and the soluble fractions of the degraded polymer, respectively. The results have proved the greater stabilizing efficiency of the N-(RPh)II derivatives relative to that of the phenyl salicylate UV absorber which is a commonly used industrial stabilizer. A radical mechanism is proposed to account for the stabilizing action of the investigated products.     

X‐ray photoelectron spectroscopy study of oxygen‐containing polymer [poly(vinyl methyl ether), poly(vinyl methyl ketone), and poly(methyl methacrylate)] surfaces metalized by vacuum‐deposited nickel

Surfaces of poly(vinyl methyl ether) (PVME), poly(vinyl methyl ketone) (PVMK), and poly(methyl methacrylate) (PMMA) were covered with different thicknesses of nickel with a metal‐vapor‐condensation method, and the metal–polymer interfaces were analyzed by X‐ray photoelectron spectroscopy. In the very first steps of the metalization, it was found that a systematic degradation of the polymer surface occurs through CO or CO₂ losses, depending on the polymer functionalities. Then, at the interface with the polymer, the condensed metal reacts by oxidization with the oxygen atoms that are still available after the surface degradation. Nickel oxide is then formed at the interface, whatever the nature of the initial polymer functional group. These new oxide species are not chemically bonded to the polymer structure, and their formation is not affected by the type of bond existing between oxygen and carbon atoms in the original polymer. Finally, the accumulation of metal on the substrate induces an amorphization of the polymer carbon structure because thermal energy is transferred from the metal coating to the polymer. © 2001 John Wiley & Sons, Inc. J Polym Sci Part B: Polym Phys 40: 82–94, 2002     

Rhodium-catalyzed 1,4-addition of terminal alkynes to vinyl ketones

The metal complex Rh(acac)(CO)₂ in the presence of an eqimolar amount of tris(o-methoxyphenyl)phosphine provides a useful catalyst system for the 1,4-addition of alkynes to unsubstituted vinyl ketones. Best yields are obtained when the transformation is performed in benzene at reflux with an excess of vinyl ketone. Both aryl and alkyl substituted alkynes participate in the reaction. Primary alcohols and alkyl chlorides are well tolerated under these reaction conditions. The reaction also proceeds in aqueous solvent mixtures, unlike most organometallic addition reactions.     

IR laser ablative modification of poly(ethylene-co-acrylic acid) zinc salt

IR laser-induced ablative degradation of poly(ethylene-co-acrylic acid) zinc salt (PEAZn) leads to cleavage of both polyethylene backbone and CO₂H group. It yields carbon oxides and volatile hydrocarbons (ethene as a major product) and affords ablative deposition of solid ionomeric films in which the initial ratio -CO₂H/-CO₂Zn is decreased due to higher thermal stability of the -CO₂Zn group. The laser-induced process differs remarkably from conventional degradation of similar polyethylene chain-based metal methacrylate ionomers that are known to yield cold ring fraction containing only -CO₂H group. The cleavage of the polyethylene backbone in the laser-induced degradation becomes more important at higher fluences. The presence of sodium metasilicate is shown to accelerate the decomposition of the CO₂H group.     

Photochemistry of 5-aryl-2(3H)-furanones. : A new route to the synthesis of chromones

The photochemistry of 5-phenyl-, 5-(2',5'-dimethoxyphenyl)-, 5-(2'-acetoxy-5'-methoxyphenyl)- and 5- (2',5'-diacetoxyphenyl)- 2(3H)-furanone (1a-d) has been investigated. Compound 1a yields phenyl vinyl ketone as expected. Similarly, 1b affords the corresponding aryl vinyl ketone but, in this case, photodimerization also occurs. Irradiation of the two o-acetoxyaryl furanones 1c and 1d gives rise to the formation of chromones as the main products. This interesting result can be accounted for in terms of a photochemical opening of the lactonic ring followed by radical addition to the acetoxy group.     

Benzil Photoperoxidations in Polymer Films and Crosslinking by the Resultant Benzoyl Peroxides in Polystyrene and Other Polymers

Benzil (BZ) can be converted almost quantitatively to benzoyl peroxide (BP) in aerated polymer films upon irradiation at >400 nm (i.e., the long-wavelength edge of the n→π* absorption band of BZ, where BP does not absorb). Here, we summarize results for the photoperoxidation of BZ structures with molecular oxygen, principally in glassy polymer matrices. Some of the polymers are doped directly with BZ or its derivatives, and others, contain covalently attached BZ pendant groups from which BP groups are derived. While the decomposition of low-molecular-weight BP doped into polymer films (such as those of polystyrene (PS)) results in a net decrease in polymer molecular weight, thermal decomposition of pendant BP groups is an efficient method for chain crosslinking. Crosslinking of PS films doped with a molecule containing two covalently linked BZ or BP groups proceeds in a similar fashion. Free radicals from the covalently attached BP allow grafting of new monomers, as well. Additionally, the use of radiation filtered through masks has been used to create patterns of polymers on solid surfaces. Crosslinking of photodegradable poly(phenyl vinyl ketone) with BP structures obtained by photoperoxidation of BZ structures for the preparation of photodegradable polymer networks is described as well. In sum, the use of BZ and BP and their derivatives offers simple and convenient routes for modifying polymer chains and, especially, for crosslinking them. Specific applications of each use and process are provided. Although applications with PS are featured here, the methodologies described are amenable to a wide variety of other polymers.     

Stereoselective synthesis of tri- and tetrasubstituted oxepanes via n-Bu3SnH mediated 7-endo-trig vinyl radical cyclisation

A stereoselective 7-endo-trig cyclisation of homopropargyl and phenyl homopropargyl derivatives of Baylis-Hillman adducts using n-Bu₃SnH/AIBN mediated vinyl radical cyclisation affords tri- and tetrasubstituted oxepanes, respectively, in good yields.     

The mass spectra of some phenyl pyridyl ketones

The mass spectra of phenyl 2-pyridyl, phenyl 3-methoxy-2-pyridyl, phenyl 4-methoxy-2-pyridyl, phenyl 5-methoxy-2-pyridyl, phenyl 6-methoxy-2-pyridyl ketones, phenyl 3-pyridyl and phenyl 6-methoxy-3-pyridyl ketones, and phenyl 4-pyridyl ketone were studied. The major fragmentation pathway of all the ketones results in the formation of[C₆H₅CO]⁺ and [C₅H₄NCO]⁺ type ions. Another fragmentation path is the loss of carbon monoxide with formation of an [M ? CO]⁺ ion after skeletal rearrangement.