Studies on stable free radicals. XVI. Copolymerizationo of a stable N-oxyl biradical with p-xylylene

Six copolymers were obtained by the reaction of a sterically hindered N-oxyl biradical with pseudodiradical p-xylylene using the reactivity of an N-oxyl toward the carbon radical. The feed ratio of the N-oxyl biradical to α-chloro-p-xylene, which was used as the precursor of the pseudodiradical p-xylylene, governed the properties of the copolymers produced. The copolymers with a terminalN-oxyl group, were obtained when a 0.4-1.2 molar ratio of the N-oxyl biradical to α-chloro-p-xylene. The polymerization process was also discussed.     

Polymerization of α-halogenated p-xylenes with base

Various α-halo-p-xylenes have been polymerized with base yielding p-xylylene polymers. The reaction involves a 1,6-dehydrohalogenation to give a xylylene which then polymerizes. α,α′-Dichloro-p-xylene forms poly-α-chloro-p-xylylene and polymers containing stilbene units; α,α,α′,α′-tetrachloro-p-xylene gives poly-α,α,α′-trichloro-p-xylylene; alkyl, aryl, and halogen ring-substituted α-chloro-p-xylenes give the corresponding ring-substituted poly-p-xylylenes. The more halogens in the α positions (up to five), the weaker the base necessary for dehydrohalogenation. Sodium hydroxide in methanol will polymerize tetrachloro-p-xylene, while potassium tert-butoxide in refluxing p-xylene is necessary to polymerize α-chloro-p-xylenes. Stilbenes are formed when α-halo-p-xylenes are reacted with potassium tert-butoxide in polar solvents such as dimethyl sulfoxide.     

Preparation of poly-p-xylylenes by electrolysis

Poly-p-xylylenes were prepared by electrolytic reduction of α,α′-dihalo-p-xylenes at controlled cathode potentials (c.p.). Polymers and halides are formed at the cathode; at the anode the halide is oxidized to halogen. Poly-p-xylylene was prepared from α,α′-dichloro-p-xylene (c.p. ?1.2 v.) and α,α′-dibromo-p-xylene (c.p. ?1.2 v.); poly-p-2-chloroxylylene from α,α′,2-trichloro-p-xylene (c.p. ?1.4 v.) and α,α′-dibromo-2-chloro-p-xylene (c.p. ?1.2 v.); poly-α,α,α′,α′-tetrachloro-p-xylylene from α,α,α,α′,α′,α′-hexachloro-p-xylene (c.p. ?0.7 v.), and poly-α,α,α′,α′-tetrafluoro-p-xylylene from α,α′-dibromo-α,α,α′,α′-tetrafluoro-p-xylene (c.p. ?1.1 v.). The cathode potentials were measured and controlled with respect to a saturated calomel electrode. Current efficiencies up to 96% were observed. α,α,α′,α′-Tetrachloro-p-xylylene was identified as an intermediate in the reduction of α,α,α,α′,α′,α′-hexachloro-p-xylene. A general mechanism for these reactions is suggested and discussed. It involves elimination of halide by a two-electron charge transfer with formation of a xylyl anion, followed by an elimination of halide in α′-position yielding xylylenes which then polymerize.     

Direct polycondensation of carbon dioxide with xylylene glycols: a new method for the synthesis of polycarbonates

This communication describes the direct polycondensation of carbon dioxide with p- and m-xylylene glycols using the system trisubstituted phosphine/carbon tetrahalide/base as a condensing agent. The polymerization reaction of carbon dioxide with p-xylylene glycol was carried out in the presence of the condensing agent in N,N-dimethylformamide. The yield was at most 81.0% obtained by using the condensing agent tributylphosphine/carbon tetrabromide/N-cyclohexyl-N′,N′,N″,N″-tetramethylguanidine (CyTMG). The structure of the product was determined by means of ¹H NMR, ¹³C NMR, and IR spectroscopy to be that of a polycarbonate. The molecular weight was estimated to be ca. 1 000–2 000 by ¹H NMR analyses.     

Synthesis of 1,1,9,9-tetrafluoro[2.2]paracyclophane and its polymerization by vapor deposition method

1,1,9,9-Tetrafluoro[2.2]paracyclophane ( 1 ) was prepared successfully as white crystals in 72% yield via two-step reactions from 1,9-diketo[2.2]-paracyclophane. The polymerization of 1 by the vapor deposition method was carried out at pyrolysis temperature range of 400 to 800°C and deposition temperature range of ?20 to 20°C, and a tough, transparent poly(α,α-difluoro-p-xylylene) film was obtained in 72% yield at the pyrolysis temperature of 750°C and the deposition temperature of ?20°C. It was found that the pyrolysis of 1 gave a reactive α,α-difluoro-p-xylylene, which polymerized on the head-to-tail addition to give poly(α,α-difluoro-p-xylylene). Some properties such as solubility, thermal stability, glass transition temperature, and density for poly(α,α-difluoro-p-xylylene) were studied. © 1995 John Wiley & Sons, Inc.     

A New,General Synthetic Method for the Preparation of Linear Poly-p-xylylenes

A new, general synthetic route to poly-p-xylylene and substituted poly-p-xylylenes is described. The key intermediate in the new process is di-p-xylylene [(2,2)p-cyclophane]. It has been found that di-p-xylylene is quantitatively cleaved by vacuum vapor-phase pyrolysis at 600°C. to two molecules of p-xylylene. p-Xylylene spontaneously polymerizes on condensation to form high molecular weight, linear poly-p-xylylene. The conversion of di-p-xylylene to poly-p-xylylene is quantitative. The process is adaptable to the preparation of a wide variety of substituted poly-p-xylylenes by pyrolysis of ring-substituted di-p-xylylenes and polymerization of the resultant substituted p-xylylenes. Many of these polymers are not attainable by any other route. All are linear and free of crosslinking. Evidence supporting the proposed mechanism of pyrolytic cleavage of every molecule of di-p-xylylene to two molecules of p-xylylene is presented. Tough, transparent polymeric films are obtained from the process when the polymerization of the p-xylylenes is conducted on glass or metal surfaces. Outstanding combinations of physical, electrical, and chemical properties are displayed by poly-p-xylylene, polychloro-p-xylylene, and other substituted polymers. A comparison of the relative merits of the original Szwarc route and the new di-p-xylylene route to poly-p-xylylenes is presented.     

Coupling of benzyl halides mediated through alkali metal supramolecular complexes. A novel route to poly(p-xylylene)

Coupling of benzyl bromide giving 1,2-diphenylethane was demonstrated to proceed at room temperature in THF solution mediated by the potassium/18-crown-6 supramolecular complex. Based on this model reaction a novel method for the low temperature synthesis of poly(p-xylylene) from α,α′-dibromo-p-xylene is proposed. Experimental evidence of the polymer structure was provided by solid-state ¹³C NMR and IR spectroscopy.     

A Facile Synthesis of Biscyclopropane Derivatives

Abstract: Bis(dibutyltelluronium)p-xylylene dibromide reacts easily with α,β-unsaturated carbonyl compounds to give biscyclopropane derivatives in high yield.

     

Unexpected formation of benzofuran derivatives in the C-amidoalkylation of p-cresol with 4-chloro-N-(2,2-dichloro-2-phenylethylidene)benzenesulfonamide*

The C-amidoalkylation of p-cresol with 4-chloro-N-(2,2-dichloro-2-phenylethylidene)benzenesulfon-amide in the presence of H₂SO₄, oleum, or a mixture of H₂SO₄ and P₄O₁₀ was studied for the first time. It was shown that the reaction not only leads to the targeted 4-chloro-N-[2,2-dichloro-1-(2-hydroxy-5-methylphenyl)-2-phenylethyl]benzenesulfonamide but is also accompanied by unexpected formation of the heterocyclic derivatives 4-chloro-N-(5-methyl-2-phenyl-1-benzofuran-3-yl)benzenesulfonamide and 5-methyl-3-phenyl-2-benzofuran-2(3H)-one.     

Thermal oxidative stability of poly-p-xylylenes

The air oxidation of poly-p-xylylene films was studied at temperatures between 125 and 200°C. The oxidation kinetics were obtained from neutron activation (NA) oxygen analyses and infrared (IR) Spectroscopy. A correlation between the NA oxygen analyses and mechanical properties indicated that the amount of oxygen incorporated into these polymers before a significant degradation mechanical properties is about 1000 ppm for poly(dichloro-p-xylylene) and 5000 ppm for poly(monochloro-p-xylylene) or poly-p-xylylene. The activation energy for the oxidation of these polymers was about 30 kcal/mole. Long-term-use (100,000 hr) temperatures were also estimated for each of the poly-p-xylylenes studied. The 100,000-hr maximum continuous-use temperature is 112°C for poly(dichloro-p-xylylene), 72°C for poly(monochloro-p-xylylene), and 57°C for poly-p-xylylene.     

Crystallization during polymerization of poly-p-xylylene. II. Polymerization at low temperature

The polymerization of p-xylylene was followed with a newly designed differential thermal analysis system at temperatures between ?196°C and ?20°C. It was found that at the lower temperatures the monomer condenses first to the crystalline monomer before simultaneous polymerization and crystallization. At the higher temperatures, polymerization and crystallization are successive. The data are in agreement with the morphology and crystal structure data derived in Part I of this series of papers on crystallization during polymerization of poly-p-xylylene.     

Chemical vapour deposition polymerization of substituted [2.2]paracyclophanes

Chemical vapour deposition polymerisation of substituted [2.2]paracyclophanes is applied to the functionalised coating of stainless steel surfaces. Poly[o-trifluoroacetyl-p-xylylene-co-p-xylylene] ( 2a ), poly[o-hydroxymethyl-p-xylylene-co-p-xylylene] ( 2b ), poly[o-amino-p-xylylene-co-p-xylylene] ( 2c ) and poly(p-xylylene-2,3-dicarboxylic anhydride) ( 2d ) were deposited as thin layers.     

Crystal structure of poly-p-xylylene. I. The α form

The molecular conformation and the crystal structure of α-form poly-p-xylylene has been determined by x-ray diffraction. The polymer has a monoclinic unit cell with a = 5.92, b = 10.64, c (fiber axis) = 6.55 Å, and β = 134.7°. Two chains pass through the unit cell, and the space groups is C2/m. The packing fraction is 0.705. One monomer unit makes up the fiber identity period and the internal rotation angles are 0° and 90° for the ? CH₂? CH₂? and ? CH₂? ?? bonds, respectively. All benzene rings are in parallel orientation, perpendicular to the ac plane.     

N-Chloro-N-(1,2,2,2-tetrachloro- and 1,2,2-trichloroethyl)- sulfonamides from N,N-Dichlorosulfonamides and 1,2-Polychloroethenes

N,N-Dichlorosulfonamides react with trichloroethylene and 1,2-dichloroethylene at a temperature not exceeding 20°C to afford unstable addition products, N-chloro-N-(1,2,2,2-tetrachloroethyl)- and N-chloro-N-(1,2,2-trichloroethyl)sulfonamides. The latter undergo elimination of chlorine on heating, irradiation, or prolonged storage to give the corresponding N-(2,2-di- or 2,2,2-trichloroethylidene)arene(or trifluoromethane)sulfonamides.     

Fused indoles. 2. Synthesis and reactions of imidazo[1,2-a]- and pyrimido[1,2-a]-indoles

The alkylation of 2-chloroindole-3-carboxaldehyde ( 1 ) and 3-acetyl-2-chloroindole ( 5 ) with 3-chloro-N,N-dimethyl-1-propylamine, 3-chloro-N,N-diethyl-1-propylamine and 2-chloro-N,N-dimethyl-1-ethylamine is described. Following alkylation, demethylation occurs and furnishes imidazo[1,2,-a]- and pyrimido[1,2-a]indoles ( 3a,6,8,10 ). Pyrimido-indole 3a , on treatment with lithium aluminum hydride, furnishes the bis-indole 12 . Analogous reaction with diborane affords the reduced product 14 , while reaction with methyllithium yields the deformylated product 13 . Spectral data of the resulting compounds are also discussed.     

Polymerization of para-xylylene derivatives. V. Effects of the sublimation rate of di-p-xylylene on the crystallinity of parylene C deposited at different temperatures

Poly(chloro-p-xylylene) was synthesized in a manner similar to poly(p-xylylene) using Gorham's method at various cryogenic temperatures. The effect of the sublimation rate of dimer on the kinetics of deposition, crystallinity, and crystalline structure was studied. Increasing the sublimation rate of the dimer increases the deposition rate similar to that of poly(p-xylylene). However, an increase in crystallinity, in contrast to Parylene N, is observed, although, in general, Parylene C has lower crystallinity relative to Parylene N. No polymorphism is observed either by decreasing the deposition temperature or by increasing the sublimation rate of the dimer. Solution annealing and isothermal annealing both bring about crystallization without any structural transformation. Solution annealing removes the oligomers and dimers, but no crystalline oligomers are ever detected under the scanning electron microscope (SEM). The surface topology of films synthesized from ambient temperature to ?40°C is very similar to Parylene N. At lower temperatures, in the region ?50 to ?60°C, a rod-type morphology is observed similar to Parylene N. The surface topology of samples synthesized at ?196°C is totally different from that of Parylene N. All low temperature synthesized samples are amorphous.     

Über 3,3,6,9,9-Pentamethyl-2,10-diaza-bicyclo-[4.4.0]-1-decen und einige seiner Derivate. Über synthetische Methoden. 13. Mitteilung

3,3,6,9,9-Pentamethyl-2,10-diaza-bicyclo[4.4.0]-1-decen and some of its derivatives A simple synthesis for the bicyclic amidine 1 (Scheme 3) is described. This base and the salts which were prepared from it show solubility characteristics which make the amidine a potentially useful reagent for salt formation of carboxylic acids and related proton complexes of bidentate ligands. Among the derivatives made from 1 are the sterically strongly hindered N-alkylated amidines 11 , 12 and 14 (Scheme 5), as well as the stable crystalline N¹-oxidoamidine-N²-oxyl radical 2 (Scheme 6). The ability of the latter to serve as a paramagnetic chelating ligand for metal ions is illustrated by the preparation of a corresponding nickel(II) complex. The radical is also a source for the α-nitronyl-nitrosonium cation 4 which shows in its reactivity towards conjugated dienes and olefines some of the expected resemblance to singlet oxygen.     

Analysis of silica hydride and surface hydrosilation reactions by solid-state NMR in the preparation of<Emphasis Type="Italic"> p</Emphasis>-chlorobenzamide bonded silica phase

²⁹Si and ¹³C CP-MAS NMR spectroscopy was used to follow the conversion of native silica to a p-chlorobenzamide bonded silica material. The benzamide bonded phase was prepared via a hydrosilation reaction of a hydride silica intermediate with p-chloro-N-allylbenzamide. Solid-state NMR was used to show the disappearance of reactive surface hydride species (M_H) and to identify newly formed bonded chemical species on the silica surface. DRIFT spectroscopy, elemental analysis, and specific surface-area determinations (BET) of the prepared phases are also reported.     

Convenient synthesis of 6-substituted-2-chloro-5,12-dihydro-5-oxobenzoxazolo[3,2-a]quinolines and N-acylated-3-chlorodibenz[b,e][1,4]oxazepin-11(5H)-ones

Convenient synthesis of variously substituted 2-chloro-5,12-dihydro-5-oxobenzoxazolo[3,2-a]quinolines at the 6-position and N-acylated-3-chlorodibenz[b,e][1,4]oxazepin-11(5H)-ones are reported. The former compounds were obtained in 65–93% yield by simply heating N-acyl-4-chloro-N-(2-hydroxyphenyl)-anthranilic acids in acetic anhydride for 4 hours, and the latter by heating sodium salt of N-acyl-4-chloro-N-(2-hydroxyphenyl)anthranilic acids with acetic anhydride.     

Polyurethanes and polyureas having long methylene chain units

Polyurethanes and polyureas containing long methylene chain units have been prepared from the following six series of monomer combinations; aliphatic diisocyanates with aliphatic glycols or diamines, methylene bis(4-phenyl isocyanate) with aliphatic glycols or diamines, and p-xylylene diisocyanate with aliphatic glycols or diamines. A good linear relationship was noted between the polymer melting points of each series against the concentration of functional groups. Both polyurethanes and polyureas from p-xylylene diisocyanate showed higher melting points than those from methylene bis(4-phenyl isocyanate) with corresponding aliphatic monomers. The relations between the melting points of these polymers with long methylene chains, including polyamides which were previously reported, and the chain components were discussed. The higher melting points of polymers containing p-xylylene group are attributed to the high rigidity of this group.