Treatment Of Poly Research Articles

Synthesis and characterization of tricarbonylmolybdenum-functionalized poly(methylphenylsilane)

The synthesis and characterization of a new metal-functionalized polysilane is reported. Treatment of poly(methylphenylsilane) with Mo(CO) 3(NC 5H 5) 3 and BF 3,OEt 2 affords the novel copolymer, poly(methylphenylsilane- stat-methyl(η 6-phenyltricarbonylmolybdenum)silane). The synthesis and characterization of the model compounds, (η 6-phenyltricarbonylmolybdenum)trimethylsilane, 1-phenyl-2-(η 6-phenyltricarbonylmolybdenum)tetramethyldisilane and 1,2-di(η 6-phenyltricarbonylmolybdenum)tetramethyldisilane, are used to support a full structural characterization of the copolymer.

Fluorescence Quantum Yield of Poly(p-phenylenevinylene) Prepared via the Paracyclophene Route: Effect of Chain Length and Interchain Contacts

The monomer 9-[(tert-butyldimethylsilyl)oxy][2.2]paracyclophan-1-ene (1) is polymerized by Mo(NAr)(CHCMe2Ph)(OCMe(CF3)2)2 (Ar = 2,6-diisopropylphenyl) in a living manner. Block copolymers containing poly(1) and polynorbornene (poly(NBE)) can be prepared and have narrow polydispersities. Treatment of poly(1) with NBu4F produces poly(9-hydroxy[2.2]paracyclophan-1-ene) which dehydrates to poly(p-phenylenevinylene) (PPV) under mild conditions. Block copolymers containing segments of size-specific and defect-free PPV with poly(NBE) of various dimensions can be prepared readily and are soluble in a variety of common organic solvents. These polymers serve as excellent candidates to measure the effect of chain length and frequency of interchain contacts on PPV's fluorescence quantum yield (Φf). Solution and solid-state quantum yield determinations, coupled to fluorescence lifetime measurements, reveal an acute drop in Φf as the degree of polymerization of the emissive species increases and as the average distance between PPV chains decreases. PPVx-block-poly(NBE)y prepared in solution consistently shows larger Φf than material prepared by solid-state dehydration. The poly(NBE) companion block also serves to protect PPV from atmospheric degradation.

Polymeric networks by the cationic crosslinking reaction of poly(allenyl ether)s having oligo(oxyethylene) moieties in the side chain

Cationic crosslinking reactions of poly(allenyl ether)s having oligo(oxyethylene) moieties prepared by the radical polymerization of the corresponding allenyl ethers were carried out under some varied reaction conditions. For instance, a crosslinked polymer was obtained in 82% yield by the treatment of poly(ethylene glycol methyl allenyl ether) (1a) with 1.2 mol% of BF3·OEt2 (2) under high concentration in dichloromethane (46 wt %). The gels obtained showed good swelling properties in water, alcohols, and polar organic solvents such as dichloromethane. In particular, the degrees of swelling of these gels in aqueous sodium chloride (1M) were quite similar to those in ion-free water, indicating that these gels served as nonionic hydrogels. © 1994 John Wiley & Sons, Inc.

Poly[(amino acid ester)phosphazenes] as substrates for the controlled release of small molecules

Three different poly[(amino acid ester) phosphazenes] have been examined in order to investigate their possible use as drug delivery vehicles. The three polymers are poly[di(ethyl glycinato)phosphazene], poly[di(ethyl alanato)phosphazene] and poly[di(benzyl alanato)phosphazene]. These macromolecules either share the same amino acid residue or the same ester group, and this facilitated comparisons of the hydrolytic decomposition and the small molecule release profiles of the polymers. The polymers were synthesized by treatment of poly(dichlorophosphazene) with an excess of the appropriate amino acid ester. Tetrahydrofuran solutions of each polymer were then thoroughly mixed with ethacrynic acid, a diuretic, or Biebrich Scarlet, an azo dye. Films cast from these solutions were immersed in aqueous media (pH 7) at 25°C and at 37°C for approximately 1400 h. During these experiments, the release of the small molecules was monitored by UV/visible spectroscopy. The molecular weight decline and the mass loss of the polyphosphazene films were measured.

Poly[(amino acid ester)phosphazenes]: Synthesis, Crystallinity, and Hydrolytic Sensitivity in Solution and the Solid State

Fifteen different poly[(amino acid ester)phosphazenes] [N=P(NHCHRCOOR') 2 ] n (R= H, Me, iPr, Bz; R'= Me, Et, tBu, Bz) were synthesized by treatment of poly(dichlorophosphazene) with a large excess of the appropriate amino acid ester. Several of these polymers were crystalline as measured by DSC. Hydrolysis studies were performed to estimate the rates of decomposition of the polymers and the duration over which the polymers maintained their structural integrity

Supercritical fluids: puissant media for the modification of polymers and biopolymers

The use of supercritical fluids as media for several types of polymer modification is demonstrated. Treatment of mixtures of chitosan with glucose or malto-oligosaccharides in supercritical carbon dioxide afforded the corresponding water soluble imine-linked, branched chitosan derivatives with high degrees of conversion. These transformations were substantially more facile and complete than previously reported equivalent reactions in conventional media. Phosphorylations of amylose and poly(vinyl alcohol) were conducted in supercritical carbon dioxide, yielding phosphate ester derivatives with phosphorus contents of 3.70% and 0.88%, respectively. Treatment of poly(vinyl alcohol), starch, maltodextrins, cellulose acetate and paper with mixtures of supercritical carbon dioxide and oxygen (19:1 v/v) led to the corresponding oxidized materials.

Synthesis of a new graphite-like layered material of composition BC3N

Treatment of poly(acrylonitrile) with boron trichloride at 400 °C or acrylonitrile with boron trichloride at 1000 °C Yields a Graphite-like semiconducting solid of composition BC3N

Surface treatment of poly(3-pentylthiophene) by ionizing radiation

The influence of radioactive krypton85Kr on the surface properties of poly(3-pentylthiophene) has been studied. Irradiation by gaseous85Kr leads to structural polymeric chain changes, which induce after iodine doping the formation of charge-transfer complexes with iodine as well as with gaseous sulfur dioxide manifesting itself by the increased electric conductivity. The presence of ammonia brings about reaction with iodine bound in the complex with a conducting polymer.

Treatment of poly(ether ether ketone) (PEEK) surfaces by remote plasma discharge. XPS investigation of the ageing of plasma‐treated PEEK

AbstractThe effect of a cold remote N2 plasma (CRNP) or N2 + O2 plasma (CRNOP) on poly(ether ether ketone) (PEEK) is studied. The amount of nitrogen or oxygen uptake and functionalities are determined by x‐ray photoelectron spectroscopy (XPS). After CRNP treatment, the N/C and O/C atomic ratios are 0.301 and 0.333, respectively. Nitrogen functional groups are not detected by CRNOP treatment, and the O/C atomic ratio is then 0.785. The ageing process of the treated PEEK surface in the open air is investigated in both cases. For CRNOP treatment the O/C atomic ratio decreases by carbonate function departure, whereas for CRNP treatment the total amount of nitrogen and oxygen graft atoms goes through a maximum after 1 h of air exposure.

Electrical conductivity of plasma‐treated poly(p‐phenylene sulfide) doped with iodine

AbstractPlasma treatment of poly(p‐phenylene sulfide) (PPS) doped with I2 is found to increase both the electrical conductivity and the stability of the material. The average conductivity of plasma‐treated samples reaches an apparently saturated value of 1.7 × 10−3s cm−1, which is about six orders of magnitude higher than that of the same material without plasma treatment, and this conductivity remains practically unchanged under exposure to ambient environment for 10 days. Infrared and secondary ion mass spectra of the samples before and after plasma treatment suggest that the charge‐transfer complexes are formed in PPS doped with I2 after plasma treatment. This is also consistent with the temperature dependence of conductivity results which show that the activation energy for electrical conduction decreases from 2.0 eV for pure PPS to 0.2 eV for plasma‐treated I2‐doped PPS. Using isothermal potential and current decay techniques, we have also measured the trap density distribution. Plasma treatment, on the one hand, does create more traps in PPS, but, on the other hand, it enhances conductivity. The mechanism of electrical conduction is briefly discussed.

Surface modification of poly(vinylidene difluoride)(PVDF) by LiOH

Treatment of poly(vinylidene difluoride), PVDF, with aqueous lithium hydroxide solution results in defluorination and oxidation at the polymer surface, whereas all previously reported wet methods for surface modification of fluoropolymers have to be executed under a dry nitrogen atmosphere, this process can be performed in the open laboratory; the chemistry occurring at the solid–liquid interface has been isolated and investigated in detail by XPS.

De novo protein synthesis is essential to human interferon γ gene expression by the stimulation with polyI:polyC

Transcription of human interferon (IFN) γ gene is induced in human peripheral lymphocyte nylon-nonadherent cells (NNA cells) by double strand RNA poly I:poly C [(1985) J. Interferon Res. 5, 77-84]. In this report, the necessity of de novo protein synthesis in an early stage of IFN γ gene expression is described. For induction of IFN γ gene expression, only initial 4 h treatment of poly I:poly C to NNA cells is sufficient. Addition of inhibitor of protein synthesis, cycloheximide (CHX), at an early stage of induction periods (0–4 h) inhibits the IFN γ induction by poly I:poly C. Cell free translation assay using RNAs isolated from NNA cells which are induced by poly I:poly C in the presence of CHX reveals that in these RNAs, IFN γ mRNA does not exist. These results demonstrate that CHX inhibits de novo synthesis of a certain protein (or proteins) and for lack of the protein(s), IFN γ mRNA cannot be transcribed. The evidence is also described in this report which suggests that the essential protein(s) might be that (those) involved in protein kinase C (pkC) activation.

Excision of the imidazole ring-opened form of N-2-aminofluorene-C(8)-guanine adduct in poly(dG-dC) by Escherichia coli formamidopyrimidine-DNA glycosylase.

A polynucleotide containing N-(deoxyguanosine-8-yl)-2-aminofluorene residues (dGuo-C8-AF) was obtained by treatment of poly(dG-dC) with [3H]ring-N-hydroxy-2-amino-fluorene. This substrate was further treated under alkaline conditions to convert dGuo-C8-AF residues into their imidazole ring-opened derivative or 1-[6-(2,5-diamino-4-oxo-pyrimidinyl-N-6-deoxyribose]-3-(2-fluorenyl++ +)urea (iro-dGuo-C8-AF). The ring-opening of 50% of the dGuo-C8-AF residues occurs in 24 h at 37 degrees C in the presence of 0.1 N NaOH. This modified polynucleotide was used as substrate for the homogeneous formamidopyrimidine-DNA glycosylase (Fapy-DNA glycosyase) of Escherichia coli. Analysis of the reaction products shows that Fapy-DNA glycosylase releases the imidazole ring-opened derivative (iro-G-C8-AF). In contrast the primary adduct (G-C8-AF) is not removed. These results show that the imidazole ring-opened form of guanine residue modified at the C8 position by a bulky adduct is a substrate for the formamidopyrimidine-DNA glycosylase of E. coli. These observations show that the formamidopyrimidine-DNA glycosylase has a broad substrate specificity including imidazole ring-opened purines either modified at N7 or C8 positions in DNA. Therefore, the Fapy-DNA glycosylase might be involved in the repair of minor lesions induced by many chemical carcinogens.

DNA adduct formation in primary rabbit tracheal epithelial cells following treatment with 1,8-dinitropyrene and its partially reduced derivative, 1-nitro-8-nitrosopyrene.

Formation of DNA adducts, following treatment of primary rabbit tracheal epithelial cells (RTEC) with 1,8-dinitropyrene (1,8-DNP) and its partially reduced derivative, 1-nitro-8-nitrosopyrene (1,8-NONO2), was examined using the 32P-post-labelling technique. Treatment of aerobic cells with 1,8-DNP or 1,8-NONO2 produced qualitatively similar results. Cochromatography showed that the major adduct observed corresponded to the major adduct seen following treatment of poly(dG.dC) with N-hydroxyl-1-amino-8-nitropyrene, generated from 1,8-NONO2. A minor adduct migrated to the same area on the TLC plate as the major compound observed following a similar treatment with poly(dA.dT). Relative adduct labelling (RAL) values were consistently an order of magnitude higher with 1,8-NONO2 than with 1,8-DNP, suggesting that reduction of a nitro group of 1,8-DNP to a nitroso group may be a rate-limiting step in the cells. In studies on the formation and persistence of the 1,8-NONO2 adduct in RTEC maximum binding was observed at 1 h. Fifteen hours later the RAL value was less than 15% of this maximum level.

Properties of FeCl3-intercalated graphite film prepared by heat treatment of poly(p-phenylene vinylene) film.

Acceptor-type compounds (${\mathrm{FeCl}}_{3}$ and ${\mathrm{CuCl}}_{2}$) have been successfully intercalated into graphite films formed by heat treatment of poly(p-phenylene vinylene). These acceptor-type intercalated graphite films show metallic characteristics in the electrical conductivity and optical reflectance. However, thermoelectric power cannot be explained by a simple metallic system. These results are very similar to those of intercalation compound prepared by using single-crystal or highly oriented pyrolytic graphite.

Treatment with poly I.C. enhances lipid peroxidation and the activity of xanthine oxidase, and decreases hepatic P-450 content and activities in mice and rats

Treatment of mice and rats with polyriboinosinic acid-polyribocytidylic acid (poly I.C., 5 mg/kg i.p.), a potent interferon inducer, decreased hepatic cytochrome P-450 system content and activities without influencing P-450-independent xenobiotic metabolizing enzymes. Treatment with poly I.C. decreased the content of P-450 by 28% in mice (P less than 0.05) and 30% in rats (P less than 0.05) but did not alter the activity of cytochrome c reductase. With treatment of poly I.C., the activity of XO increased 87% in mice (P less than 0.01) and 30% in rats (P less than 0.01). Lipid peroxidation was enhanced by 82% in mice (P less than 0.01) and 95% in rats (P less than 0.05). These results raise the possibility that a part of the depression of P-450 system content and activities by poly I.C. might be caused by enhanced lipid peroxidation associated with increased activity of XO.

N-Hydroxy Amides. I. Synthesis of N-Benzyloxy and N-Hydroxy Peptides via Polymerization of N-Benzyloxy Dl-α-Amino Acid N-Carboxy Anhydrides

Abstract Polymerization of N-benzyloxy Dl-α-amino acid N-carboxy anhydrides (N-benzyloxy-NCAs) has been carried out in benzene for 30 d with cyclohexylamine as initiator. The N-benzyloxy-NCAs of glycine, alanine, 2-aminobutyric acid, and leucine give the corresponding polymers in good yields, while the starting material is recovered from those of valine and phenylalanine. The different behavior in the polymerization is discussed in terms of steric crowding. Catalytic hydrogenation of the N-benzyloxy polymers produces poly(N-hydroxy peptide)s. Complex formation of these polymers with iron(III) has been examined. Among the polymers, poly(N-hydroxyalanine) is further converted into poly(N-acetoxyalanine), which acts as an acyl active polymer. Treatment of poly(N-benzyloxyalanine) with B(CF3CO2)3 gives 1,4-dihydroxy-3,6-dimethyl-2,5-piperazinedione.

Misincorporation in DNA synthesis after modification of template or polymerase by MNNG, MMS and UV radiation

The synthetic DNA polymers, poly(dG-dC), poly(dC), poly(dA-dT), poly(dA) and poly(dT), were treated with N-methyl- N′-nitro- N-nitrosoguanidine (MNNG), methyl methanesulfonate (MMS) and UV irradiation. The modified polymers were use as templates to examine the incorporation of non-complementary nucleotides by E. coli DNA polymerase I. Methylation of poly(dG-dC) by MNNG predominantly induced the misincorporation of dTMP, whereas methylation by MMS induced that of dAMP. Treatment of poly(dT) with MNNG caused the misincorporation of dGMP to a considerable extent, but MMS did not enhance the error on poly(dT). The misincorporation of dAMP on poly(dC) and that of dGMP on poly(dA) were also increased by these chemicals. UV irradiation of poly(dT) and poly(dC) induced the error of dGMP and dAMP, respectively. These data on MNNG and MMS in vitro were in fair agreement with the directions of mutation in vivo. But the predominant induction of transitions by UV in vitro did not agree with the UV-induced transversions in E. coli. This inconsistency suggested the participation of other factors than direct mispairing in UV-induced transversion. Modification of DNA polymerase I by MNNG changed the ratio of polymerase to 3′→5∼ exonuclease activity altering the fidelity of this enzyme, whereas MMS and UV-irradiation did not alter the fidelity of the enzyme.

Mutagenesis by alkylating agents: Coding properties for DNA polymerase of poly (dC) template containing 3-methylcytosine

After treatment of poly(dC) by the simple alkylating agent (3H)dimethylsulfate, 90 per cent of the radioactivity cochromatographied with 3-methylcytosine and 10 per cent with 5-methylcytosine which is the normally occurring methylated base. In order to study the influence of 3-methylcytosine on DNA replication, untreated and DMS-treated poly(dC) were used as templates for E. coli DNA polymerase I. The alkylation of poly(dC) inhibits DNA chain elongation, and does not induce any mispairing under high fidelity conditions. The alteration of DNA polymerase I fidelity by manganese ions allows some replication of 3-methylcytosine which mispairs with either dAMP or dTMP. Our results suggest that 3-methylcytosine could be responsible, at least partially, for the killing and the mutagenesis observed after cell treatment by alkylating agents.

Investigation of activation of phosphate groups in mono- and oligonucleotides with mesitoyl chloride.

It has been demonstrated with the use of 31P NMR pulsed spectroscopy that the reaction of mesitoyl chloride (MsCOCl) both with terminal and internucleotide phosphate groups pA, d(MeOTr)TpT and dpTpT (Ac) proceeds in a quantitative fashion within less than 2 min at 0 degrees C with the respective mixed anhydrides being thereby formed. The anhydrides of phosphomonoesters are resistant, unlike those of phosphodiesters which may be readily split by water, alcohol or amine without the internucleotide bonds being broken. Treatment of poly(U) with an excess of MsCOCl leads to rapid cyclization followed by formation of phosphotriesters. A comparatively easy hydrolysis leads to partial cleavage and isomerization of internucleotide bonds. A similar treatment of UpC showed that about 20% of the internucleotide bonds are cleaved, the remaining UpC being a mixture of approximately equal amounts of 3'-5'- and 2'-5'-isomers.