William E. Douglas

Curing reactions in acetylene terminated resins—I. Uncatalyzed cure of arylpropargyl ether terminated monomers

Abstract Two arylpropargyl ether terminated monomers have been synthesized, (pHCCCH2OC6H4)2CMe2 (I) and the analogous model monomer pHCCCH2OC6H4CMe2Ph (II) having a single arylpropargyl ether group. DSC, i.r., 1H- and 13C-NMR analysis of the products resulting from partial cure of I and complete cure of II showed that the crosslinking involves prior sigmatropic rearrangement of the arylpropargyl ether groups to 2H-1-benzopyran structures which subsequently polymerize. The various intermediate 2H-1-benzopyran-containing species were isolated and characterized.

Preparation of diphenylsilylene polymers containing main-chain acetylene and (hetero)aromatic groups : χ(2) non-linear optical and other properties

Abstract Polymers having the structure ???CCSi(Ph 2 )CCZ??? (Z = 1,4-benzene, 4,4′-biphenyl, 9,10-anthracene, 2,7-fluorene, 6,6′-bipyridine, 2,5 and 2,6-pyridine, 2,5-thiophene, 2,6- p -dimethylaminonitrobenzene, 2,6- p -nitroaniline, 2,6- p -nitrophenol, 2,6- p -cyanophenol, p -tetrafluorobenzene and 2,7-fluoren-9-one) were prepared by reaction of diethynyldiphenylsilane with the appropriate (hetero)aromatic dibromide or diiodide in the presence of [(PPh 3 ) 2 PdCl 2 ], CuI and PPh 3 , the solvent being either triethylamine or triethylamine with toluene. Depending on the Z group and the solvent system, the weight-average molecular weight as determined by SEC ranged from 2600 for 2,6-pyridine to 34,000 for 1,4-benzene. The UV/visible spectra show absorption maxima in the region 250–400 nm. The polymer with 2,6- p -dimethylaminonitrobenzene groups was χ (2) active, the value of r 33 being 0.8 pm V −1 following fixed electrode poling at 17.5 V μm −1 . The polymers did not melt below the decomposition temperature, and all transitions shown in the DSC thermogram to 300°C were found to be absent on repeat scans. Thermogravimetric and thermal dynamic analysis of the polymer where Z = 1,4-benzene showed decomposition commencing at 290°C and continuing up to ca . 750°C. The residue was composed of α-SiC and amorphous carbon. Treatment of the same polymer with BH 3 /SMe 2 gave rise to an insoluble polymer containing boron. The polymer where Z = 6,6′-bipyridine reacted with copper(II) trifluoromethanesulfonate to give a copper(II) -containing polymer, hydrazine reduction of which afforded the corresponding Cu I -containing polymer.

Preparation of oligomers containing tetraphenylsilole, acetylene and aromatic groups in the main chain, and incorporation of iron carbonyl

Abstract Polycarbosilanes with the structure [-SiR 2 CCZCz.tbnd;C]- n (R 2 Si = 2,3,4,5-tetraphenyl-1-sila-2,4- cyclopentadiene; Z = 1,4-benzene, 4,4′-biphenyl, 9,10-anthracene, 2,7-fluorene, 2,5- and 2,6-pyridine, 6,6′-bipyridine, 2,5-thiophene, 2,6- p -dimethylaminonitrobenzene, 2,6- p -nitroaniline, 2,6- p -nitrophenol, and 2,7-fluoren-9-one) were prepared by reaction of 1,1-diethynyl- 2,3,4,5-tetraphenyl-1-sila-2,4-cyclopentadiene with the appropriate (hetero)aromatic dibromide or diiodide in the presence of [(PPh 3 ) 2 PdCl 2 ] and CuI. Exo- and endotherms observed in the initial DSC scans were absent in repeat scans. The oligomer where Z = p -C 6 H 4 reacted with [Fe(CO) 5 ] under UV irradiation to give an oligomer containing iron carbonyl fragments attached to ca . 30% of the silole groups.

Preparation et reactivite de composes chiraux et non chiraux derives de (η5-cyclopentadienyl) dicarbonylfer. stereochimie de la coupure de la liaison fer—silicium

Abstract The preparation and some properties of compounds of the type (η5-C5H5)Fe(CO)(L)SiR3 (L = CO, PPh3, PCy3 (Cy = cyclohexyl), P(OEt)3 and R3 = Ph3, Ph2Me, PhMe2, Ph2(CH=CH2) or optically active MePh-1-Np) are described. When the environments of the silicon and iron atoms are asymmetric, it is possible to isolate the diastereoisomers. The iron—silicon bond is particularly stable; it is cleaved with retention of configuration by some nucleophiles (H2O, LiAlH4); electrophilic cleavages (Cl2, Br2, Cl2/AlCl3, Cl2/PPh3) are more complex and lead both to retention and inversion depending on the nature of the reagent and the substrate.

Curing reactions in acetylene terminated resins—III. DSC, TGA and TMA study of catalyzed cure of an ethynylaryl-terminated monomer

Abstract DSC shows that the curing of the ethynylaryl-terminated monomer (1,4-(1,3-HCCC6H4-CH2O)C6H4)2CMe2 (II) in the presence of (η-Cp)Co(CO)2, (η-Cp)2Ni, (PPh3)2NiCl2, (PPh3)2PdCl2, or (PPh3)3RhCl takes place at lower temperatures than in the absence of the catalysts. The enthalpies of polymerization are also lower except in the case of the (η-Cp)Co(CO)2-catalyzed system which shows a value similar to that for the uncatalyzed resin. Comparison with calculated polymerization enthalpies suggests that crosslinking occurs by cyclotrimerization in the presence of (η-Cp)Co(CO)2, but predominantly by non-aromatic conjugated linear polyene formation with the other catalysts. TG analysis indicates that the resulting resins, crosslinked in the presence of catalysts, are all of similar thermal stability, this property being determined by the structure of II rather than by that of the crosslinks. The Tg values determined by TMA are similar except for a low value for the (η-Cp)Co(CO)2-catalyzed resin which is therefore less rigid.

Preparation And Structure Of Phosphonium Ions With Intramolecular P N Coordination; Novel Diphosphonium Salts And Ionomer Containing Backbone Hypervalent Phosphorus

Starting from R′R2P (R′ = 8-dimethylamino-1-naphthyl) containing a donor dimethylamino group, the new phosphonium salts [R′R2P(CH2Ph)]+Br– [R = Me (9) or Ph (10)] and [R′R2P(p-CH2C6H4CH2)PR2R′]2+[2Br]2– [R = Ph (12)] have been prepared. An interaction between the N and P atoms is evident from the X-ray crystal structure of 10 the N–P distance being less than the sum of the van der Waals radii of the 2 atoms. The geometry of 10 is that of a monocapped tetrahedron whereas the X-ray crystal structure determination shows essentially regular tetrahedral geometry for the analogous compound without the donor amino group, [(1-Np)Ph2P(CH2Ph)]+Br– (11). Treatment of 1,5-bis(dimethylamino)-2,6-dilithionaphthalene with chlorodiphenylphosphane gave 1,5-bis(dimethylamino)-2,6-bis(diphenylphosphanyl)naphthalene (8) which in the presence of methyl iodide afforded the diphosphonium salt [1,5-bis(dimethylamino)-2,6-bis(diphenylmethylphosphonium)naphthalene]2+[2I]2– (13). Similarly, treatment of 8 with 1 equivalent of benzyl bromide gave the monophosphonium salt [1,5-bis(dimethylamino)-2diphenylbenzylphosphonium-6-diphenylphosphanyl-naphthalene]+[Br]– (14) whereas in the presence of 2 equivalents of the same reagent [1,5-bis(dimethylamino)-2,6-bis(diphenylbenzylphosphonium)naphthalene]2+[2 Br]2– (15) was obtained. The ionomer poly([(1,5-bis{dimethylamino}2,6-bis{diphenylphosphonium}naphthalene)-(P,P-p-xylylene)]2+[2 Br]2–) (16), soluble in liquid SO2, was prepared by treatment of 8 with α,α′-dibromo-p-xylene.

N-Ethylcarbazole as a structure-directing agent in poly[(ethynediyl)(arylene)(ethynediyl)silylene]–poly(phenylsilsesquioxane) hybrid nanomaterials exhibiting photorefraction at telecommunication wavelengths

Self-organisation through π-stacking occurs in poly[(ethynediyl)(arylene)(ethynediyl)silylene]–N-ethylcarbazole–poly(phenylsilsesquioxane) compositions giving rise to nanostructured hybrid layered materials exhibiting photorefraction at telecommunication wavelengths. To our knowledge, this is the first such material to be reported the poly[(ethynediyl)(arylene)(ethynediyl)silylene] acting as an optical chromophore, charge generator and conductor. The absorption band tails into the near-IR hence providing charge generation at 1500 nm excitation. The photorefractive response was investigated by using a two-beam coupling technique. The gain of the probe beam intensity, delivered from the pumping beam, reached 40 cm−1 with an electric field strength of 650 kV cm−1 thus confirming the photorefractive nature of the grating. The gain exceeded the absorption (30 cm−1) hence showing the high potential of this material for practical applications.

Nickelocene-catalyzed polymerization of acetylenes

Abstract At 115°C in the absence of solvent, nickelocene catalyses the polymerization of phenylacetylene to give a mixture of cyclotrimers and linear alkene oligomers with 92% conversion after 6 h. In the case of 1-(1-methyl-1-phenylethyl)-4-(2-propynyloxy)benzene under similar conditions, nickelocene catalyses both cyclotrimerization and cyclotetramerization.

Curing reactions in acetylene-terminated resins. Part 5.—Cyclotrimerization versus linear polyene formation in the catalysed cure of ethynylaryl-terminated monomers

Structural differences in the polymers obtained by catalysed cure of the ethynylaryl-terminated monomer [1,4-(1,3-HCCC6H4CH2O)C6H4]2CMe2(1) could not be detected by IR or NMR spectroscopy. However, a study of the solvent-free catalysed polymerization of the model monomer, phenylacetylene, showed that the extent of cyclotrimerization decreased in the order (η-Cp)Co(CO)2≫(η-Cp)2Ni≈(PPh3)2NiCl2≫(PPh3)2PdCl2 with an accompanying increase in the degree of linear polyene formation, suggesting that this is so also for the catalysed cure of 1.

Electrical conductivity of FeCl3-doped poly(alkynylsilane)s

Abstract The electrical conductivies of the poly(alkynylsilane)s [C-SiR 1 R 2 -CC-Z] n (R 1 R 2 Si = Ph 2 Si, n Oct(Me)Si, 2,3.4,5-tetraphenyl-1-sila-2,4-cyclopentene; Z = (hetero)aromatic group) doped with FeCl 3 are found to lie in the range 10 −9 −3 S cm −1 , whereas those of the undoped polymers are less than 10 −10 S cm −1 . The presence of Ph groups on Si leads to incresed conductivity.