Preparation and thermal properties of polyquinazolones: Effect of the chemical structure of bisbenzoxazinones on the thermal properties

Four kinds of polyquinazolones were synthesized from 4,4′-diaminodiphenylether and bisbenzoxazinones having different central aromatic nuclei (benzene, biphenyl, benzophenone, diphenylmethane). All the polymers were prepared by solution polycondensation at 190°C at a concentration of 15% solid in m-cresol, and were obtained with intrinsic viscosities in the range of 0.3–0.8 dL/g in 97–98% yield. Their thermal properties were studied by using dynamic thermogravimetry and isothermal weight loss. All the polymers were found to produce high char yields (55–75%) in nitrogen. Oxidative thermal stability of the polymers was dependent on the chemical structure of bisbenzoxazinone and was governed by the stability of the bonds in the quinazolone units. The following order of oxidative thermal stability of the quinazolone units was determined from this study: diphenylmethane < benzophenone < biphenyl < benzene.     

Chemical modification of polymers. XI. Photoreactive polymers from poly(vinylbenzyl chloride)

Photocrosslinking has been observed in a number of polymers derived by chemical modification of poly(vinylbenzyl chloride). Included are polymers bearing pendant benzophenone, stilbazolium, fluorenone, carbazole, and sulfonylazido moieties. The synthesis and properties of these polymers are described.     

Designing systems for a multiple use of light signals.

The photochemical and photophysical behavior of two dendrimers consisting of a benzophenone core and branches that contain dimethoxybenzene units has been investigated. Such dendrimers can undergo a variety of photochemical and photophysical processes, namely: 1) quenching of the fluorescence and phosphorescence of the dimethoxybenzene units by energy transfer to the benzophenone core (antenna effect), 2) direct and sensitized phosphorescence (and delayed fluorescence) of the benzophenone core, 3) hydrogen abstraction by the triplet excited state of the benzophenone core from solvent molecules, 4) intramolecular hydrogen abstraction by the triplet excited state of the benzophenone core from the dendrimer branches, 5) quenching of the phosphorescence and hydrogen abstraction reaction of the benzophenone core by energy transfer to terbium ions and dioxygen; 6) conversion of the UV light absorbed by the dendrimer branches into visible (Tb3+) or near infrared (O2) emission via the sequence of processes 1) and 5). The results obtained emphasize the great potential of suitably designed dendrimers for a multiple use of light signals.     

Novel luminescent liquid crystalline polyazomethines. Synthesis and study of thermotropic and photoluminescent properties

Novel semiflexible polyazomethines containing chromophoric units into azomethine mesogenic core have been synthesised by condensation of a flexible dialdehyde with mesogenic diamines containing fluorene, antraquinone, pyrimidine, azobenzene and benzophenone. The thermotropic behaviour of the resulting polyazomethines was assessed by differential scanning calorimetry, polarised light microscopy and investigations of the miscibility relations. While the pure polyazomethines showed a birefringent viscous texture difficult to be ascribed, by mixing with a liquid crystal dimer, clear Schlieren or marbled textures were observed, indicating a nematic mesophase. The polymers exhibited violet, blue or yellow light emission.     

Phthalocyanine polymers. IV. Novel type of thermally stable polyimides derived from metal phthalocyanine tetramines and benzophenone tetracarboxylic dianhydride

Poly(metal phthalocyanine)imides of copper, cobalt, nickel, and zinc were synthesized by the reaction of metal phthalocyanino tetramines with benzophenone tetracarboxylic dianhydride. These polymers were characterized by elemental analyses and IR, TGA, and inherent viscosity studies. Noteworthy features of these phthalocyanine polymers are their remarkable thermal and thermooxidative stabilities with char yields at 800°C that range from 78 to 83% in a nitrogen atmosphere. The relative thermal stabilities of these polymers have been evaluated by activation energy measurements.     

Reactive polypeptides. II. Photochemistry of poly(γ-cinnamyl L-glutamate)

Poly(γ-cinnamyl L -glutamate) was irradiated in the presence and absence of benzophenone in dichloroethane. The irradiated polymers were analyzed by gas chromatography after hydrolysis. It was possible to assign the transformation in the presence of benzophenone to trans-cis photoisomerization by comparing the effects with those observed for a model compound cinnamyl acetate. The equilibrium composition of cis and trans isomers in the photostationary state was similar for the model compound and the polypeptide. Photoisomerization was found to be accompanied by marked side reactions for the direct irradiation. Circular dichroism spectra were empolyed to study the structure, and no changes in the structure were found for the irradiated polymers.     

双吡啶盐及其聚合物的研究Ⅱ.4,4’-(-1,4-苯撑-)-双-[N-烷(芳)基-2,6-二苯基]-吡啶盐及其聚合物对某些芳香酮还原反应的催化作用

在4,4’-(1,4-苯撑)-双-IN-烷(芳)基-2,6-二苯基I吡啶盐及其聚合物的催化下,二苯甲酮和苯乙烯基苯甲酮与中性条件下的锌粉发生双分子还原反应,生成相应的邻二叔醇;而结构类似的环状酮却主要发生单分子还原反应.双吡啶盐及其聚合物的结构和反应介质的极性对还原反应的速度有很大影响。本文对催化反应的机理也进行了讨论。     

Gas sorption and transport in UV-irradiated polyarylate copolymers based on tetramethyl bisphenol-A and dihydroxybenzophenone

Gas sorption and transport properties at 35°C are reported for a series of ultraviolet irradiated polyarylates prepared from tetramethyl bisphenol-A (TMBPA), 4,4′-dihydroxybenzophenone (DHB), and 5-tertiary-butyl isophthalic acid dichloride (tBIA). UV irradiation induces crosslinking and photo-Fries rearrangements in these polymers. The gas permeability of the polyarylates decreases with UV irradiation due to reductions in the diffusion coefficient; however, the ideal selectivity for all gas pairs increases with UV irradiation. The effect of UV irradiation on the gas transport properties of the polyarylates is compared with that reported in the literature for similar polyimide materials. The polyimides show much greater improvement in selectivity than do the current polyarylate materials. The photo-Fries rearrangements limit the amount of crosslinking achievable in these polyarylate materials in spite of the fact that additional benzophenone units are formed.     

Synthesis of self‐photosensitizing polyesters containing donor–acceptor norbornadiene moieties and benzophenone groups and their photochemical reactions

The ring‐opening copolymerization of a glycidyl ester derivative having a benzophenone group and the donor–acceptor norbornadiene (D‐A NBD) dicarboxylic acid, 5‐(4‐methoxyphenyl)‐1,4,6,7,7‐pentamethyl‐2,5‐norbornadiene‐2,3‐dicarboxylic acid, monoglycidyl ester derivatives with D‐A NBD dicarboxylic anhydride using tetraphenylphosphonium bromide as a catalyst proceeded smoothly to give novel self‐photosensitizing NBD polymers in good yields. The molecular weight of these polyesters was about 4,000, and lower than that of analogous NBD polymers having no benzophenone group. All the synthesized NBD polymers isomerized smoothly to the corresponding quadricyclane (QC) polymers upon UV irradiation in tetrahydrofuran (THF) solution and in the film state. The rate of the photoisomerization of the D‐A NBD moieties in these polymers was higher than that of the D‐A NBD moieties in the polymer having no photosensitizing group. Furthermore, the rate of the photoisomerization of the D‐A NBD moieties in these polymers was also higher than that of the NBD polymer with low molecular weight photosensitizer in dilute solution. The photo‐irradiated polymers having QC moieties released thermal energies of 146–180 J/g. The D‐A NBD moieties contained in these NBD polymers possessed fair to good fatigue resistance. The degradation of the NBD moieties in these polymers was 15–30% after 50 repeated cycles of interconversion. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 2978–2988, 2007     

A study on the energy transfer and migration in the molecules of polymeric triplet sensitizers: (2) A study on delay fluorescence and polarization spectra

The triplet energy migration of polymers and copolymers of vinyl benzophenone (VBP) and vinyl naphthalene (VN) has been studied by measuring delayed fluorescence and polarization spectra in glassy dilute solution at 77 K. Strong delayed fluorescence of PVN proves the existence of triplet energy migration and T-T annihilation in the polymer chain. Efficient intersystem crossing of “BP” and efficient energy migration and transfer between chromophores along the polymer chain result in the absence of delayed fluorescence for copolymer P (VN-VBP) studied in this work. The order of benzophenone phosphorescence intensity: BP>Co (VBP-St)>PVBP indicates the T-T annihilation decreasing the phosphorescence of PVBP. Fluorescence and phosphorescence polarization data of polymers are smaller than that of their model compounds. It is evident that energy migration exists in the polymer chain.     

Preparation of phosphorus-containing polymers—XVI. Synthesis of phosphorus-containing polyanhydride-imides

Phosphorus-containing polyanhydride-imides were synthesized from N,N-bis(4-carboxyphthalimido)-3,3′-diphenylalkylphosphine oxide, 3,3′-[N,N′-bis(4-carboxyphthalimido)]benzophenone and their mixtures in two steps via the diacetyl derivatives of the bisimide-carboxylic acids. The resulting polymers have reduced viscosities of 0.06–0.14 dl/g and are soluble in polar aprotic solvents such as DMA, DMF and DMSO, and conc. H₂SO₄ etc. They have good hydrolytic stability for moisture and water. Phosphorus-containing polymers have little heat-resistance and poor flame-retardance. The benefit of incorporating phosphorus in the polymers is small.     

Laser flash photolysis of benzophenone in polymer films

With a nanosecond laser we studied flash photolysis of benzophenone (BP) dissolved in four different polymer films. We measured kinetics of decay of a triplet state of benzophenone (3)BP as well as kinetics of decay of benzophenone ketyl free radicals BPH(?). Polymer matrices have plenty of reactive C-H bonds, and the hydrogen abstraction by (3)BP leads to a formation of geminate pair which either recombines into molecular products or dissociates. Decay kinetics of (3)BP is well described by dispersive kinetics and in particular by the kinetic law suggested in Albery, W. J.; et al. J. Am. Chem. Soc. 1985, 107, 1854. We observed a broader distribution of rate constants in hard films. It was observed that the decay kinetics of transients radicals in the "hard" polymers is quite satisfactory described by the same law for dispersive kinetics. Kinetics of radicals decay in "soft" polymers is satisfactorily described as a diffusion-enhanced reaction. Effect of a hardness of polymer matrix on the measured kinetic parameters is discussed.     

Preparation and Properties of Polyallenes III. Polymerization of Allenes Induced by Al-i-Bu3-VOCl3 Catalyst

The polymerization activity of several allenes under the influence of Al-i-Bu₃-VOCl₃, and structure and properties of the solid polymers obtained, have been studied. Allene; butadiene-1, 2; hexadiene-1, 2; 3-methylbutadiene-1, 2; 3-methylpentadiene-1, 2; and pentadiene 2, 3 could be converted into soluble, solid polymers. 2-Methylpentadiene-2, 3; tetramethylallene; and tetraphenylallene did not react under the polymerization conditions applied. The following order of polymerization activity seems to be valid: CH₂?C?CH₂ > R₁CH?C?CH₂ > R₁R₂C?C?CH₂ ≥ R₁CH?C?CHR₂, > R₁R₂C?C?CHR₃ ≥ R₁R₂C?C-CR₃R₄. The polymers of the homologues of allene were obtained as amorphous solids with the exception of poly(3-methyl-butadiene-1, 2), which was fairly crystalline.     

Synthesis of new dimeric-PEG-supported cinchona ammonium salts as chiral phase transfer catalysts for the alkylation of Schiff bases with water as the solvent

The water-soluble PEG-supported cinchona ammonium salts were successfully synthesized and used as chiral phase transfer catalysts for the asymmetric alkylation of tert-butyl benzophenone Schiff base derivatives with high chemical yields (up to 98%) and enantioselectivities (up to 97%) in aqueous media. The recycling results showed that the polymers were stable and rarely lost activities.     

A well-defined hydrocarbon-soluble calcium hydroxide: synthesis, structure, and reactivity

Controlled hydrolysis of a (beta-diketiminate)calcium-amide gave a heteroleptic (beta-diketiminate)calcium-hydroxide complex that is remarkably stable against ligand exchange and formation of Ca(OH)2. The structure of this dimeric complex shows OH- units that symmetrically bridge the Ca2+ ions. This hydrocarbon-soluble calcium hydroxide reacted rapidly with CO2 to produce a gel from which amorphous CaCO3 slowly separated. This reaction behavior allows for sol-gel coating with CaCO3 from an organic solvent. Reaction with benzophenone did not lead to nucleophilic attack of OH- to the carbonyl but gave a red benzophenone adduct instead.     

Crystallization kinetics of polymer–diluent mixtures. Influence of benzophenone on the spherulitic growth rate of isotactic polystyrene

As an extension of earlier work on the crystallization kinetics of isotactic polystyrene, the spherulite growth rate in mixtures of isotactic polystyrene and benzophenone has been measured over a concentration range extending from pure polymer to a mixture containing about 30% benzophenone. The glass transition temperature has been measured over the entire range from pure polymer to pure benzophenone. For the mixtures the dependence of the growth rate on temperature is similar to that of the undiluted polymer. The addition of benzophenone causes a shift of the crystallization range to lower temperatures. For mixtures containing up to about 20% benzophenone, the maximum in the growth rate increases with increasing content of benzophenone. On addition of more benzophenone, the maximum rate is depressed. Taking into account the glass transition temperature of the mixtures, the influence of benzophenone on the melting point of isotactic polystyrene, and the volume fraction of polymer, we can describe the influence of benzophenone on the growth rate in a semiquantitative way.     

High temperature polymers. III. Diphenyl sulfone-based polyamide-imides

High temperature thermoplastic polyamide-imides were prepared from a new series of aromatic diamines containing the diphenylsulfone unit and alternatively, oxydiphenyl and diphenylisopropylidene units. The polymers were prepared in their completely imidized form by using a facile in situ chemical imidization reaction which offers several advantages over the conventional thermal imidization process. The sulfone-based polyamide-imides exhibited an excellent combination of moldability, thermal stability, mechanical properties and solvent resistance. Analysis of the properties of these polymers in terms of structural variations permits a useful correlation of the effect of various structural units on performance. The polar diphenyl sulfone and amide-imide units increase the glass transition temperature and improve solvent resistance while the oxydiphenyl and diphenylisopropylidene units improve thermoplasticity. Sulfone ether diamine polyamide-imide (VI) offers the best combination of high temperature performance and moldability.     

Head-to-head vinyl polymers. XI. Preparation and characterization of poly(methyl acrylate) and poly(methyl methacrylate) consisting of head-to-head and head-to-tail units through cyclopolymerization of acrylic and methacrylic anhydrides

Acrylic anhydride (AAn) and methacrylic anhydride (MAAn) were polymerized with radical initiator in polar solvents at high temperatures. The polymers obtained were found to consist of five-and six-membered ring structures by comparing IR spectra of the polymers with those of model compounds, succinic anhydride, and glutaric anhydride. Hydrolysis and methylation of the polymers gave new polymers composed of head-to-head (HH) and head-to-tail (HT) methyl acrylate (MA) or methyl methacrylate (MMA) units. The content of HH unit of these HH/HT polymers was determined by ¹H-NMR and ¹³C-NMR spectra. The softening, glass transition, and thermal degradation temperatures of the poly(MA) with HH and HT units were found to somewhat increase with increasing of the content of the HH units. On the other hand, the glass transition and thermal degradation temperatures of the poly(MMA) with HH and HT units increased similarly, but the softening temperature decreased as the content of the HH units increased.     

Phosphorus based epoxy terminated structural adhesive 2. Curing, adhesive strength and thermal stability

The curing behavior of phosphorus based epoxy terminated polymers was studied using diaminodiphenyl ether, diaminodiphenyl sulfone, benzophenone tetracarboxylic dianhydride and the commercial hardener of Ciba-Geigy's two-pack araldite, as curing agent. The adhesive strength of these adhesives was measured by various ASTM methods like lap-shear, peel, and cohesive tests on metal-metal, wood-wood and wood-metal interfaces. All these results were compared with the synthesized epoxy resins prepared from bisphenol-A and epichlorohydrin having the epoxy equivalent value of 0.519. The thermal stability of both the virgin resin and its cured form was also studied by thermogravimetric analysis.     

Biomimetic catalysis with immobilised organometallic ruthenium complexes: substrate- and regioselective transfer hydrogenation of ketones

Chloro-(eta6-arene) complexes of ruthenium(II) with N-sulfonyl-1,2-ethylenediamine ligands that have one or two styrene side chains have been synthesised and characterised. The chloro ligand was substituted with a diphenylphosphinato ligand and the resulting organometallic complexes are transition state analogues for the ruthenium-catalysed transfer hydrogenation of benzophenone. Following the protocol of molecular imprinting, these complexes were copolymerised with ethylene glycol dimethacrylate (EGDMA) in the presence of a porogen. The polymers were ground and sieved, and the phosphinato ligand was substituted with a chloro ligand, thus generating a shape-selective cavity in close proximity to the catalytically active metal centre. When tested for their ability to catalyse the reduction of benzophenone, the imprinted polymers showed a significantly higher activity (up to a factor of seven) than control polymers without cavities. Out of a mixture of seven different aromatic and aliphatic ketones, benzophenone was preferentially reduced when the imprinted polymer was used. Furthermore, the specificity of the catalyst for diaryl ketones has been confirmed in a reaction with a bifunctional substrate, 4-acetyl-benzophenone; the diaryl ketone was reduced faster with the imprinted catalyst than the acetyl group. The opposite regioselectivity was observed with the control polymer. Both the activity and the selectivity of the imprinted catalysts are dependent on how the ruthenium complexes are attached to the polymer backbone. A double connection proved to give superior results.