bluuebunny/crossref_metadata_2025_split huggingface dataset:
Aromatic polyesterimides
Authors: Loncrini D. F. 
Published: April 2003

AbstractSeveral novel arylene bis(trimellitate) dianhydrides have been prepared by: the acidolysis reaction of trimellitic anhydride (TMA) with aromatic diacetoxy compounds and the reaction of trimellitic anhydride monoacid chloride with diphenols. These novel aromatic bisesteranhydrides were reacted with aromatic diamines in polar solvents to give high molecular weight polyamic acid solutions. Heat converted these soluble precursors to insoluble aromatic polyesterimides having good physical and thermal properties. The mechanism of the acidolysis reaction between an aromatic acid and an aromatic acetoxy compound is briefly discussed.
Oxygen diffusion limitation in autoxidation of polypropylene
Authors: Boss C. R. , Chien J. C. W. 
Published: April 2003

AbstractThe induction period for the autoxidation of polypropylene increases with increasing sample thickness (from 1 to 75 mils) and with decreasing oxygen pressure. The rate of oxidation shows the opposite dependences. In contrast, neither the rate nor the induction period in well stirred oxidations of squalane is oxygen pressure‐dependent. It is concluded that autoxidation of polypropylene is controlled by diffusion of oxygen into the sample.
Heterogeneous polymer systems. IV. Mechanism of rubber particle formation in rubber‐modified vinyl polymers
Authors: Molau Gunther E. , Keskkula Henno 
Published: April 2003

AbstractA mechanism for the formation of rubber particles in the polymerization of solutions of rubber in vinyl monomers is presented. A polymeric oil‐in‐oil emulsion is formed in the first phase of the polymerization. This polymeric oil‐in‐oil emulsion is transtormed into a solid dispersion of rubber in vinyl polymer in the second phase of the polymerization. A phase inversion takes place in the emulsion in the first phase of the polymerization. Rubber solution droplets are formed at the phase inversion point. These droplets harden as the polymerization proceeds and are gradually transformed into the solid, crosslinked rubber particles of the final polymer.
Stereoregular polymerization of methyl vinyl ether with fluoro aluminum initiators
Authors: Kern R. J. , Calfee J. D. 
Published: April 2003

AbstractThe reactions of HF, BF3, or certain organic fluorine compounds with AlCl3, (C2H5)3Al, or ethylaluminum chlorides in chlorinated hydrocarbons give rise to gels which exhibit pronounced stereoregular polymerization initiating ability toward methyl vinyl ether. The active sites are believed to involve species of the type RAlF4. Polymeric products having a wide range of stereoregularities are obtained. Several polymerization variables were examined. The reaction systems exhibit a variety of appearances and interesting rheological sequences. These are the consequences of differential solubility behaviors of the various stereoregular fractions. The most highly stereoregular fractions may be fabricated as fibers, films, or molded objects. Fractions of intermediate stereoregularity exhibit interesting emulsion‐forming properties. Stereoregularity is shown to afford a novel control over degree of water absorption in films.
A new series of organoboranes. VII. The preparation of poly‐m‐carboranylenesiloxanes
Authors: Papetti Stelvio , Schaeffer B. B. , Gray A. P. , Heying T. L. 
Published: April 2003

AbstractThis paper describes the preparation of the first members of a new series of polysiloxanes characterized by having m‐carborane nuclei in the backbone of the polymers. Although neither hydrolysis of 1,7‐bis(chlorodialkylsilyl)‐m‐carborane monomers nor catalytic dehydration of the corresponding dihydroxy compounds would proceed to give the type of polysiloxanes desired, the polymers were readily prepared by the ferric chloridecatalyzed elimination of an alkyl halide from equimolar mixtures of dichloro‐ and dialkoxysilanes. This technique allowed the systematic introduction of dialkylsiloxy groups between m‐carborane nuclei. Characterization of the polymers is described as well as differential scanning calorimetry studies which show the prime members of the series to be thermally stable to 500°C. and oxidatively stable to about 350°C.
Thermal behavior of polyhydrazides and poly‐1,3,4‐oxadiazoles
Authors: Frazer A. H. , Sarasohn I. M. 
Published: April 2003

AbstractThe thermal properties of a series of polyhydrazides and corresponding poly‐1,3,4‐oxadiazoles have been investigated using differential thermometric and thermogravimetric techniques. In addition, the conversion rates of the polyhydrazides to the corresponding oxadiazole structures have also been measured. In general, weight loss in polyhydrazides occurs in three distinct stages corresponding, respectively, to loss of adsorbed water, cyclodehydration, and decomposition of the poly‐1,3,4‐oxadiazole formed in situ. The polyoxadiazoles generally exhibit only a single weight loss step (below 700°C.) corresponding to decomposition and volatilization of the substrate itself. These data clearly indicate that the presence of aliphatic carbon–carbon linkages in the polymer backbone reduces the temperature at which decomposition of the polyoxadiazoles is noted. Corresponding differential thermometry patterns give additional data on phase transitions in the polymers and indicate, in general, that the poly‐1,3,4‐oxadiazoles formed in situ decompose before reaching their intrinsic melting points (under the specific conditions of these experiments). Comparison of the poly‐1,3,4‐oxadiazoles prepared under the (rapid) dynamic conditions of the differential thermometry and thermogravimetry techniques employed (30°C./min.) with isothermal rate data clearly suggests subtle structural differences in the polyoxadiazoles prepared by the two different modes. In general, ΔE‡ for the hydrazide–oxadiazole conversion amounts to about 49–53 Kcal./mole while ΔS‡ amounts to 14–17 e.u. However, both ΔE‡ and ΔS‡ for the polymer containing exclusively 1,3‐phenylene linkages between incipient oxadiazole groups appear to be considerably higher (ΔE‡ = 62 Kcal./mole, ΔS‡ = 34 e.u.). This striking difference is explained in terms of the increased order resulting from the higher degree of crystallinity in the polyhydrazide.
Homogeneous ion‐exchange membranes of improved flexibility
Authors: Rosenblum P. , Tombalakian A. S. , Graydon W. F. 
Published: April 2003

AbstractPoly(styrenesulfonic acid) ion‐exchange membranes having various degrees of porosity and flexibility have been prepared by using aliphatic and aromatic esters of p‐styrenesulfonic acid. The membranes formed from the aliphatic ester monomers were found to exhibit an increase in water uptake, permeability, and flexibility with increase in the size of the alcohol group of the ester monomer. With membranes formed from the phenyl and β‐naphthyl ester monomers the reverse trend was indicated. The flexibility of the membranes formed from the aromatic ester monomers was much greater than that obtained with the aliphatic esters.
Polymerization of cyclic ethers in the presence of maleic anhydride. Part II. Investigation of the polymerization mechanism
Authors: Takakura Koichi , Hayashi Koichiro , Okamura Seizo 
Published: April 2003

AbstractIn order to elucidate the reaction mechanism of both the radiation‐induced and benzoyl peroxide‐catalyzed polymerizations of cyclic ethers in the presence of maleic anhydride, the development of color during reaction and copolymerization of oxetane derivatives were investigated. Upon addition of a small amount of the γ‐ray or ultraviolet‐irradiated equimolar solution of a cyclic ether and maleic anhydride to isobutyl vinyl ether, a rapid polymerization took place, and the resulting polymer was confirmed to be a homopolymer of isobutyl vinyl ether. A heated solution of dioxane, maleic anhydride, and a small amount of benzoyl peroxide can initiate the polymerization of isobutyl vinyl ether in the same manner. The electrical conductivity of a 1:1 mixture of maleic anhydride and dioxane is increased by about a factor of ten after ultraviolet irradiation. These results indicate that some cationic species are actually formed in the system by irradiation or the decomposition of added benzoyl peroxide. The mechanism of formation of the cationic species responsible for the initiation may be explained as follows. A free radical of an ether is formed by abstraction of a hydrogen atom attached to the carbon adjacent to oxygen atom, followed by a one‐electron transfer from the resulting radical to maleic anhydride, an electron acceptor, to yield the cationic species of the ether and the anion‐radical of maleic anhydride, respectively. The resulting cationic species as well as the counteranion‐radical are resonance‐stabilized. Therefore, the present polymerization may be designated a radical‐induced cationic polymerization.
Polymerization of complex systems. A study of the system methyl methacrylate–vinyl isobutyl ether–maleic anhydride by means of an NMR technique
Authors: Haney Carolyn P. , Johnson F. A. , Baldwin M. G. 
Published: April 2003

AbstractIt has been shown that the rates of polymerization of individual monomers in a mixture of monomers can be followed by means of an NMR technique. The technique is rapid and simple and requires very little sample. The system MMA–MA–VIBE was investigated by the technique. From the data obtained it was concluded that the polymer formed in a mixture of the three monomers is a block copolymer made up of (MMA)m and (MA–VIBE)n units, the lengths of which depend on the monomer concentrations.
Polymerization of styrene with chromium acetylacetonate and triethylaluminum and diethylaluminum bromide
Authors: Deshpande A. B. , Subramanian R. V. , Kapur S. L. 
Published: April 2003

AbstractKinetics of the polymerization of styrene in the presence of benzene at 30°C., with chromium acetylacetonate in combination with triethylaluminum and also in combination with diethylaluminum bromide as catalyst, have been studied. Chromium acetylacetonate forms a homogeneous system with triethylaluminum, and chromium acetylacetonate with diethylaluminum bromide behaves as a heterogeneous system. This homogeneous catalyst system, though reported inactive in the polymerization of α‐olefins, has been found effective with styrene. Depending on the homogeneity and heterogeneity of the system, the rate of polymerization is proportional to half order and first order of catalyst concentration. A probable reason for the effect of homogeneity on the order of reaction has been discussed. A study of the effect of diethylzinc as a chain‐transfer agent has helped to confirm the mechanism of polymerization.
Low‐temperature polymerization of isobutyl vinyl ether
Authors: Blake G. J. , Carlson A. M. 
Published: April 2003

AbstractIsobutyl vinyl ether has been polymerized under conditions well known to yield isotactic polymer, viz., with boron trifluoride etherate at 78°C. in a nonpolar hydrocarbon diluent. A particular mixed solvent ratio and previous dissolution of catalyst enabled the polymerization to proceed homogeneously at the beginning. By following the temperature rise in an initially thermostatted system, we showed that the progress of the reaction eventually proceeded via a homogeneous phase to a gellike phase. Isotactic polymer is shown to be produced in both steps by a mechanism of slow chain propagation.
Bulk polymerization of α‐chloroacrylonitrile
Authors: Grassie N. , Grant E. M. 
Published: April 2003

AbstractPoly‐α‐chloroacrylonitrile, which may be regarded as a hybrid of poly(vinyl chloride) and polyacrylonitrile, is, like these polymers, insoluble in its own monomer. Its bulk polymerization is thus heterogeneous, showing abnormal kinetic features by comparison with homogeneous polymerizations. The polymerization exhibits autocatalytic properties. The initiator exponents at 0 and 5% polymerization are 0.45 and 0.44, respectively, and the overall energy of activation is 23.0 ± 2 Kcal./mole. There is no significant change in molecular weight with catalyst concentration in the range 0.057–0.90% nor with conversion up to 12%, but the reaction is accelerated by addition of polymer. Bulk polymerization results in colored products, the color deepening with conversion. These results have been compared with those of Bamford and Jenkins for acrylonitrile and Bengough and Norrish for vinyl chloride and are found to be in closer accord with the latter. They can be accounted for satisfactorily by Bengough and Norrish's suggestion that transfer occurs between growing polymer radicals and dead polymer molecules, the radicals thus formed on the surface of the polymer being removed by transfer to monomer.
Preparation and properties of poly(methylene terephthalates)
Authors: Smith James G. , Kibler Charles J. , Sublett Bobby J. 
Published: April 2003

AbstractA systematic study of poly(methylene terephthalates) has been made. Melting points, second‐order transition temperatures, and solubility temperatures are presented for the homologous series of terephthalate polyesters of ethylene glycol through 1,10‐dodecanediol, and for terephthalate copolyesters of: (1) ethylene glycol/1,3‐propanediol and (2) ethylene glycol/1,4‐butanediol. Fiber properties of the terephthalate polyesters and the 70/30 ethylene glycol/1,3‐propanediol copolyterephthalate ester are presented. Only the first three members of the poly(methylene terephthalate) series show promise for use in textile fibers.
Studies on Ziegler‐Natta catalysts. Part I. Reaction between trimethylaluminum and α‐titanium trichloride
Authors: Rodriguez L. A. M. , van Looy H. M. , Gabant J. A. 
Published: April 2003

AbstractThe reaction between α‐TiCl3 and AlMe3 at 65°C. in the absence of solvent was studied by a method which gives information about the early stages of the reaction. The results obtained give evidence for a sequence of consecutive reactions and show that the first of these is a fast partial alkylation of the α‐TiCl3 surface. The mechanism of formation of methane in the last step of the reaction is discussed in detail.
Studies on Ziegler‐Natta catalysts. Part II. Reactions between α‐ or β‐TiCl3 and AlMe3, AlMe2Cl, or AlEt3 at various temperatures
Authors: Rodriguez L. A. M. , van Looy H. M. , Gabant J. A. 
Published: April 2003

AbstractThe following reactions, carried out in the absence of solvents, has been studied: α‐TiCl3 + Al(CH3)3 at 20°C., β‐TiCl3 + Al(CH3)3 at 65°C., α‐TiCl3 + Al(CH3)2Cl at 20 and 65°C., and α‐TiCl3 + Al(C2H5)3 between 30 and 65°C. It appears that a general reaction mechanism, such as discussed in the preceding paper of this series, applies to all these reactions between TiCl3 and aluminum alkyls. The differences in overall stoichiometry between some of these systems may be linked to differences in stability of the intermediate TiC bonds. In the case of α‐TiCl3 + Al(CH3)2Cl, alkylation is probably accompanied by fixation of the AlCH3Cl2 on the nonvolatile product.
AlEt3–metal soap catalysts for the polymerization of epoxides
Authors: Takahashi Akio , Gaylord Norman G. 
Published: April 2003

AbstractEpoxides, propylene oxide in particular, were polymerized by a catalyst system consisting of AlEt3–metal soap, to high molecular weight polyethers in high conversion. Carboxylic acid salts of Ti, V, Cr, Zr, Mo, Co, and Ni, transition metals of groups IV–VIII in the Periodic Table, were most preferable. Metal salts of stearic, octanoic, lauric and naphthenic acid were examined as catalyst components and proved to be very active for the polymerization of epoxides when used with an organoaluminum compound such as AlEt3 or AlEt2Cl. Copolymerization of propylene oxide and allyl glycidyl ether was successfully carried out with an AlEt3–Zr octoate catalyst.
Radiation‐induced copolymerization of formaldehyde and styrene
Authors: Castille Y. P. , Stannett V. 
Published: April 2003

AbstractThe radiation‐induced copolymerization of styrene with liquid formaldehyde in bulk and in solution has been studied at low temperatures. In bulk and in methylene chloride solution copolymerization took place, whereas in diethyl ether solution only homopolymerization of the formaldehyde was found. At −78°C., in bulk and in methylene chloride solution, no evidence of polystyrene blocks could be found, whereas at −30°C. in bulk about 30% of the styrene content of the copolymer was in the form of high molecular weight blocks. The rate of copolymerization in methylene chloride solution was found to be first‐order with respect to dose rate and third‐order with respect to formaldehyde concentration similar to results reported for formaldehyde in toluene solution. The thermal stabilities of the copolymers were found to be intermediate between those of pure polyoxymethylene and commercially stabilized polymers. Since the latter were of higher molecular weight and contain added stabilizers, the increased thermal stabilities of the copolymers were considered to be particularly significant.
Preparation of crystalline polyamides by the alternating copolymerization of aziridines and cyclic imides
Authors: Kagiya Tsutomu , Narisawa Shizuo , Manabe Kuniyoshi , Kobata Mikio , Fukui Kenichi 
Published: April 2003

AbstractThe copolymerization of aziridines and cyclic imides was studied. Aziridines copolymerized alternately with cyclic imides to give crystalline polyamides. Ethylenimine and succinimide copolymerized to nylon 2,4, melting near 300°C., without any catalyst. Similarly, the corresponding crystalline polyamides were obtained from the systems of 1,2‐propylenimine–succinimide, ethylenimine–glutarimide, and ethylenimine–phthalimide. The copolymerization of aziridines and cyclic imides in the presence of BF3OEt2 gave a copolymer which was rich in aziridine units, whereas, the addition of triethylamine had no influence on the copolymer composition. A mechanism of copolymerization was proposed based on the facts that N‐tetramethylenesuccinamide was obtained by the reaction of pyrrolidine and succinimide, N‐acetylethylenimine reacted with acetamide to yield N,N′‐diacetylethylenediamine and that the rate of this copolymerization was dependent on the electrophilicity of imide.
Quantum efficiency of the 2537 A. Photolysis of a mixed phenyl–methyl polysiloxane
Authors: Siegel Seymour , Champetier Robert J. , Calloway A. R. 
Published: April 2003

AbstractThe ultraviolet (λ = 2537 A.) photolysis of a degassed mixed phenyl and methyl polysiloxane liquid is examined in terms of gas and crosslinking yields. Results are compared to the published values obtained by ionizing irradiation of this type of molecule. It is shown that ultraviolet radiation is less efficient by two orders of magnitude in producing decomposition (i.e., gaseous products) than is ionizing radiation. The comparisons for crosslinking efficiencies are less certain, but the yields seem to have much more similar values in this case based on a spectroscopic estimation of crosslinking (i.e., analysis for substituted phenylcyclohexadiene formation). The gas quantum yields were ϕH2 = 2.6 × 10−5, ϕCH4 = 0.63 × 10−5, ϕC2H6 ≈ 0.12 × 10−5, and ϕC2H2 ≈ 0.06 × 10−5.
Studies in some new initiator systems for vinyl polymerization. Part I. Molecular halogens or halates as one component
Authors: Saha Mihir K. , Sen Manasi , Pramanick Dinabandhu 
Published: April 2003

AbstractSeveral new initiating systems involving a molecular halogen, halates, or perhalate as one of the components and a reducing metal salt, ammonia, an amine or an organic compound as the other component, have been introduced for the aqueous (and in a few cases the non‐aqueous) polymerization of methyl methacrylate. Some of the resulting polymers have been subjected to endgroup analysis by the application of the ultrasensitive dye techniques recently developed in our laboratory. Reducing metal salt—halogen‐initiated polymers are found to incorporate hydroxyl and halogen endgroups, while polymers initiated by amine—halogen systems incorporate hydroxyl and halogen as well as amino endgroups. However, in the ammonia—halogen system polymers incorporate only halogen endgroups. On the basis of the results of the endgroup analysis of the polymers an attempt has been made to explain the probable initiation mechanism with regard to the nature and identity of the initiating species involved in such processes.
Irradiation of some polysiloxanes in various gases
Authors: Jenkins Robert K. 
Published: April 2003

AbstractThe changes produced by γ‐irradiations on two polysiloxanes in several gaseous atmospheres were studied by both sequential and parallel exposures with an in‐situ vibrating reed technique. Irradiation in atmospheres of N2O, He, air, and a mixture of 20% NO2 and 80% N2, caused reduction in the crosslinking rates of the polymers as compared to vacuum. Marked discolorations of the samples occurred when irradiations were conducted in air, N2O, and 20% NO2–80% N2. Similarities in crosslinking rates and color changes were obtained when the polymers were irradiated in either air or the gas mixture.
p‐Chlorophenyldiazonium hexafluorophosphate as a catalyst in the polymerization of tetrahydrofuran and other cyclic ethers
Authors: Dreyfuss M. P. , Dreyfuss P. 
Published: April 2003

Abstractp‐Chlorophenyldiazonium hexafluorophosphate is shown to be a convenient and effective catalyst for initiating the polymerization of tetrahydrofuran (TH) and other cyclic ethers. The polymerizations apparently proceed without any significant termination or transfer reactions (i.e., “living” polymers result), and materials of very high molecular weight can be obtained. A mobile monomer‐polymer equilibrium for THF was obtained during polymerization and equilibrium conversions were determined at a number of temperatures. The ceiling temperature derived from these data was 84°C., the heat of polymerization was −4.58 kcal./mole and the corresponding entropy change was − 17.7 cal./°C.‐mole. Hydrocarbons are suitable inert solvents for these polymerizations, but concentrated solutions must be used at ambient temperatures in order to stay above the required equilibrium monomer conceiitration and also to dissolve the catalyst which is insoluble in hydrocarbons. It was shown that acyclic ethers act as transfer agents in these polymerizations and that transfer with consequent reduction of molecular weight continues even after monomer‐polymer equilibrium is reached. Cyclic ethers do not act as transfer agents but only copolymerize. Trimethyl orthoformate was shown to be a particularly effective transfer agent; it resulted in a polymer with methoxy endgroups and produced methyl formate as a by‐product. The data obtained are consistent with a mechanism involving initiation by hydrogen abstraction and polymerization via tertiary oxonium ions associated with PF−6 gegenions. This gegenion is thought to be responsible for the “living” nature of the system.