Linear all-ortho oligomers of phenol–formaldehyde resins. I. Preparations,characterizations, and solution properties

Three kinds of all-ortho methylene-linked phenolic oligomers, i.e., 4-tert-butylphenol (BP), phenol (AO), and O-methylated BP (BPM), were prepared with good yields and their dilute solution properties were studied. In acetone, all of these oligomers are highly solvated and molecularly dispersed. In chloroform, however, AO and BP molecules strongly form hydrogen bonds among themselves. By intramolecular and intermolecular hydrogen-bondings, a large portion of the dimers and the trimers of AO and BP associate to form bimolecular aggregates in chloroform, assuming pseudo-cyclic conformations analogous to calix [4] arene and calix [6] arene, respectively. By intramolecular hydrogen-bonding, the tetramers and the hexamers also form pseudo-cyclic conformations by themselves in chloroform. © 1993 John Wiley & Sons, Inc.     

Ab initio studies on hydrogen-bonded clusters. I. Linear and cyclic oligomers of hydrogen cyanide

Large-scale ab initio calculations have been performed on linear and cyclic oligomers of hydrogen cyanide molecules applying basis sets ranging from double-zeta to near-Hartree-Fock quality. Equilibrium geometries of linear (HCN)_n clusters with n = 1 to 5 and of cyclic clusters with n = 3, 4 are reported. For most of the complexes complete vibrational analysis has been carried out. In agreement with recent experimental data the linear HCN trimer was found to be more stable than the cyclic trimer. In case of the tetramer linear and cyclic structures are of comparable stability. The structural changes taking place upon polymerization of linear HCN clusters and the convergence of various stage properties to those of the infinite polymer (HCN)_∞ are discussed in detail. The evolution from vibrational spectra of small oligomers to phonon dispersion curves of the infinite polymer is illustrated too.     

Copolymerization of elemental sulfur with cyclic(arylene disulfide) oligomers

Copolymerization reactions between cyclic(arylene disulfide) oligomers were studied. The cyclic disulfide oligomers derived from 4,4′-isopropylidene bisbenzenethiol gave soluble polysulfanes via copolymerization with S₈. The copolymerization reactions were studied both in solution and melt by GPC and NMR. Solution copolymerization reactions can only form polysulfanes with up to three to four sulfur linkages; however, melt copolymerization reactions gave polysulfanes with up to seven sulfur linkages (average). The melt copolymerization reactions between cyclic disulfide oligomers derived from 4,4′-thiobis(benzenethiol) and S₈ were studied using DSC, TGA, and DMTA. With increasing contents of sulfur in the polysulfanes, T_gs, 5% weight losses by TGA, and tan δ decreased. With seven sulfur linkages in the polymer, it is a rubber with a T_g of 12°C, a 5% weight loss by TGA of 249°C, and tan δ of 44°C, respectively. © 1997 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 35 : 2961–2968, 1997     

Dimers, trimers and oligomers of sulfur oxides: an ab initio and density functional study

Ab initio (HF/3-21G^*), DFT (B3LYP with basis sets 6-31G^*, 6-311+G^* and 6-311+G(2d)) and, in some cases, MP2/6-31G^* calculations, were done on cyclic dimers, trimers, etc. and on acyclic oligomers (with OH and H on the ends) of sulfur monoxide and sulfur dioxide. The four cyclic (SO)_n molecules were (S–O)₂ (1,3,2,4-dioxadithietane, 1a), (S–O)₃ (1,3,5,2,4,6-trioxatrithiane, 2a), (S(=O))₄ (tetrathietane 1,2,3,4-tetraoxide, 1b), and (S(=O))₆ (hexathiane 1,2,3,4,5,6-hexaoxide, 2b). The four cyclic (SO₂)_n molecules were the dioxide of 1a (1,3,2,4-dioxadithietane 2,4-dioxide, 1c), the trioxide of 2a (1,3,5,2,4,6-trioxatrithiane 2,4,6-trioxide, 2c), the tetraoxide of 1b (tetrathietane 1,1,2,2,3,3,4,4-octaoxide, 1d) and the hexaoxide of 2b (hexathiane 1,1,2,2,3,3,4,4,5,5,6,6-dodecaoxide, 2d). The 16 acyclic molecules (oxides of disulfane, trisulfane, etc. and oxides of oxadisulfane, dioxatrisulfane, etc.) were (–S–O–)_n, (–S(=O)–)_n, (–S(=O)O–)_n, and (–S(=O)₂–)_n, with n from 2 to 5 and HO, H at the ends. Most of these species are relative minima on the B3LYP/6-31G^* potential energy surface. In energy content, the SO dimer, etc. lie below, and the SO₂ dimer, etc. above, their SO_x components, at all the electron-correlated levels.     

s-Triazines. II. The synthesis of some new cyclopoly-s-triazinylene thioethers and disulfides

A number of new cyclopoly-s-triazinylene thioethers and disulfides have been prepared in dilute solution. Their structures and methods of formation are discussed. A thermo-gravimetric analysis of cyclopoly-2-phenyl-s-triazinylene-4,6-monosulfide is included.     

Internal motion in organosilicon polymers. I. Linear dimethylpolysilazane

A linear dimethylpolysilazane polymer has been prepared and its internal motion studied by the techniques of broadline nuclear magnetic resonance. Second moments and line widths are reported as a function of temperature from ?196 to 30°C. The results are compared to those for linear dimethylpolysiloxane, as well as to those for the crosslinked siloxane and silazane. The experimental low-temperature second moment of 7.25 ± 0.5 gauss² corresponds to a C₃ reorientation of methyl groups about the silicon–carbon bond. The motions occurring in the silazane are found to be the same as those in the corresponding siloxane. The transition to low second moments occurs approximately 30°C. higher in the linear silazane than in the linear siloxane. This is attributed to a somewhat greater resistance to motion in the silazane.     

Some physical properties of polyorganosiloxanes. I. Linear polyorganosiloxanes

Some physical properties of linear polydimethylsiloxanes have been studied. The states and transitions in polydimethylsiloxanes have been investigated by using the method of dynamic heat capacity and a thermomechanic method in the temperature range from ?150 to +200°C. The temperature dependence of primary and secondary crystallization has been studied by optical, calorimetric, and x-ray methods.     

Synthesis,characterization, and curing of well-defined allyl ether-maleate functional ester oligomers: Linear versus nonlinear structures

A series of allyl ether-maleate functional star-shaped esters with from one to four arms has been synthesized. The structures that have been made are an analogous series with increasing molecular weight and functionality where the increase in molecular weight has been made nonlinear, i.e., star-shaped. The resins are monodisperse in the sense that each arm has a well-defined structure and that, within a certain sample, only one type of molecule exists. The viscosity and rheological behavior of the resins have been studied. The curing kinetics of the star-shaped (branched) resins and the properties of the films formed have also been studied. These properties have been related to differences in functionality and to differences in the molecular architecture of the resins. © 1992 John Wiley & Sons, Inc.     

Nonmetals in the argon-inductively coupled plasma-optical emission spectrometry: I. Phosphorus, sulfur and carbon

The behavior of phosphorus, sulfur and carbon in the argon-ICP-OES was systematically investigated for a wide range of nebulizer gas flows and observation heights. Five lines of phosphorus, four lines of sulfur and three lines of carbon, which have analytical usable detection limits, were taken into consideration. The further parameter set was inspired by the needs of every-day-analysis in the laboratory, especially the low integration time that is necessary for analysis of large amounts of samples. For each element line a signal-to-noise plot was obtained with a method described earlier. The optimum conditions for the combined analysis were determined from signal-to-noise plots of those element lines with the lowest detection limits. The lowest detection limits for phosphorus (0.13 mg/L) and carbon (0.01 mg/L) are useful for solving many analytical problems. However, even the best detection limit for sulfur (2.97 mg/L) is only of limited use without further preconcentration. A major problem was the background of carbon, most probably from carbon dioxide, which increased the available detection limit to about 0.04 mg/L. Surprisingly, the best detection limits were obtained at very low observation heights, which were only a couple of millimeters above the load coil. Fortunately, all elements showed a similar behavior and so the detection limits at compromise conditions were only slightly higher compared with the single-element detection limits.     

Investigation by means of I.R. spectroscopy of styrene oligomers containing acrylonitrile active ends

The successive addition of acrylonitrile (AN) portions to oligostyrene anionic ends was studied by means of i.r. spectroscopy. The attachment of AN to the oligostyrene active centre took place mainly across the double bond of the monomer accompanied by formation of the carbanion CHCN with characteristic absorption band at 2030–2040 cm^?1. Comparatively high temperatures of the experiments (above ?40°) provided conditions for side reactions in the polymerization. The latter were checked spectrophotometrically: cyclization according to Ziegler-Thorpe and formation of anionic centre

and proton transfer reaction between this centre and AN causing the formation of enaminonitrile structure. By study of model compounds, the band at 2110–2130 cm^?1 was assigned to the

group.     

Reactive oligomers. I. Preparation and polymerization of ethylene glycol bis(methyl fumarate)

Ethylene glycol bis(methyl fumarate) (EGBMF) was prepared as a new type of divinyl compound and reactive oligomer: a needle crystal, m.p. 104.5°C. Homopolymerization of EGBMF was carried out in dioxane with 0.1 mol/L AIBN at [M] = 1 mol/L and 60°C; the rate of polymerization was estimated to be 4.44 × 10^?6 mol/L s in a good agreement with diethyl fumarate (DEF). The cyclization constant K_c was obtained as 1.64 mol/L, being rather low compared with diallyl oxalate which is 1,9-diene having two ester groups analogous to EGBMF. Gelatin occurred at about 35% conversion. Finally, the copolymerization of EGBMF (M₁) with diallyl phthalate (DAP) (M₂) is tentatively explored with the intention of the improvement of allyl resins in mechanical properties; remarkable rate enhancement was observed for copolymerization. The monomer reactivity ratios were estimated to be r₁ = 0.96 and r₂ = 0.025, the r₁ value being reduced compared with the DEF-DAP copolymerization system. These results are discussed from the standpoint of steric effect on the polymerization of fumarate as an internal olefin.     

Dilute solution properties of a polyurethane. I. Linear polymers

A linear polyurethane of high molecular weight was prepared in solution by the polyaddition of equimolar amounts of ethylene glycol and methylene bis(4-phenyl isocyanate). The polymer was fractionated by using a direct sequential extraction procedure, with a solvent–nonsolvent system consisting of N,N′-dimethylformamide (DMF) and acetone (A). The resulting fractions were characterized by viscosity and lightscattering measurements. The relationship between the intrinsic viscosity and molecular weight was found in DMF at 25°C. to be [η] = 3.64 × 10^?4M^0.71. The unperturbed polymer chain dimensions were determined from intrinsic viscosity measurements carried out under experimentally determined theta conditions.     

Structure and reactivity of copper(I) oligomers

The reactivity of oligomeric copper(I) complexes towards test electrophiles and hydrogen have been studied. The complexes exhibit similar reactivity patterns in most cases. Photochemical irradiation of the tetramer4, led to the isolation of the ligand8, 2, 6-dimethylphenyl-N-phenylthionocarbamate, present in the tetramer. This compound crystallized in the monoclinic system in the P2₁/n space group witha = 11.992(5) ?, b = 9.886(3) ?,c = 12.783(6) ?, β = 115.91(4)°,V= 1360.37(4) ?{st3}, z = 4. The comparison of the structure of the ligand with the tetramer shows the differences in the structure brought about by coordination. A comparison of the structures of the tetramer4 and the hexamer 5 brings out the differences in the nature of bridging sulphide which considerably alters the properties of the complexes. Differences in the reactivity can be understood in terms of the type of the sulphide bridge present in the complexes. Similarities in the reactivity trends are the result of the dissociation of the oligomers in solution.¹HNMR studies reveal that the structures of these complexes in the solution state are different from the solid state and account for the similarities in the reactivity patterns of these complexes.     

Sulfur modification of polyethylene surfaces. I. Insertion of sulfur into polyethylene surfaces

Atomic sulfur generated respectively by the pyrolysis of carbonyl sulfide and by the photolysis of carbonyl sulfide, carbon disulfide, and sulfur vapors has been shown to modify irreversibly the surface of polyethylene as shown by wettability measurements. The nature of the modification is not completely apparent from this portion of the study, however, insertion of the atomic sulfur into a carbon—hydrogen bond to form a surface thiol group appears likely. The modified surfaces thus formed are shown to undergo several classical organic reactions, as determined by wettability measurements.     

Condensed thiophenes from sulfur bridging. I. Phenanthro[4,5-bcd]thiophene

Treatment of phenanthrene with hydrogen sulfide and an alumina catalyst at 630° gives phenthro[4,5-bcd]thiophene (XVII). Spectral properties of XVII, its sulfoxide, and its sulfone are presented. Other examples of the direct insertion of a sulfur bridging atom into an aromatic molecule are reviewed.