bluuebunny/crossref_metadata_2025 huggingface dataset:
Photodegradation of poly(methyl methacrylate)
Authors: Allison J. P.
Published: April 2003

The vacuum photodegradation at 30°C. of poly(methyl methacrylate) and copolymers with acrylaldehyde, methacrylaldehyde, and methyl acrylate has been studied. The polymers were examined in the form of expanded films as produced by a freeze‐drying technique. At least one molecule of carbon monoxide is evolved for each chain scission. It is concluded that chain scission in poly(methyl methacrylate) is primarily the result of photoinduced aldehyde groups.
Investigation of autoacceleration effects during the solution polymerization of styrene
Authors: Glass J. E. , Zutty N. L.
Published: April 2003

The possibility of obtaining increases in the rate and degree of polymerization through a decrease in the termination rate in nonviscous, homogeneous solution polymerizations of styrene has been investigated. Decreases in the termination rate were achieved through decreasing segmental diffusion of the propagating macroradical by greater occlusion, on the average, of the radical in the coiled polymeric chain. Coiling of the polymeric chain was effected by polymerizing styrene in thermodynamically poor (θ) solvents near the θ temperature for polystyrene. Examples of such systems are diethyl oxalate at 51.5°C. and cyclohexane at 34.6°C. Polymerization under these conditions did lead to a decrease in the kt/kp2 kinetic ratio; this decrease resulted in increases in the degree of polymerization, but changes in the rate of polymerization, in contrast to the marked increases noted in viscous solution or heterogeneous polymerizations, were not observed. Possible explanations for the latter observations are discussed.
Polyamides from α,ω‐oxaalkanedioic acids having long methylene chain units
Authors: Saotome Kazuo , Sato Kenichiro
Published: April 2003

Three series of polyamides were prepared from diamines (hexamethylenediamine, bis‐5‐aminoamyl ether, p‐xylylenediamine) and α,ω‐oxaalkanedioic acids of formula HOOC(CH2)mO(CH2)nCOOH, where m = n = 3–10, in symmetric structures, but m = 3 or 4 in unsymmetric structures. The melting points of these polymers were plotted against the number of carbon atoms of the oxaalkylene groups. The melting points of polymers from each diamine fell on three different curves according to the structures of the dicarboxylic acids: symmetric (CH2)nO(CH2)n; unsymmetric (CH2)3O(CH2)n, and unsymmetric (CH2)4O(CH2)n. A minimum melting point is observed at about the same point of the acid structure in every curve of the unsymmetric dicarboxylic acids. The marked depression in the polymer melting points around the minimum point is attributed to the increase of the entropy of fusion.
Preparation of poly‐p‐xylylenes by electrolysis
Authors: Gilch H. G.
Published: April 2003

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.
Spectroscopic studies of poly(vinyl chloride) and its deuterated derivatives
Authors: Enomoto S. , Asahina M. , Satoh S.
Published: April 2003

Poly(vinyl chloride) (PVC) and all its deuterated derivatives were prepared by variation of the polymerization method and polymerization temperature to study the structure of PVC and the mechanism of addition polymerization by infrared spectroscopy and high resolution NMR spectroscopy. The CH and CH2 stretching modes of PVC were assigned completely from the infrared spectra of PVC‐αd1, PVC‐β,βd2 and PVC‐d3. The frequencies of the CCI stretching modes of the polymers depended not only on the substituents in the trans position to the Cl atom across both adjacent CC bonds, but also on the atom attached to the C atom of the CCl bond. The frequency shifts were used to assign the CCl stretching modes of PVC‐βd1 and PVC‐α,βd2 and to study the opening of the double bond of VC in the addition polymerization. The differences of the chemical shifts of the α and β protons of PVC due to the tacticity were determined experimentally by PVC‐β,βd2 and PVC‐αd1 without using the spin‐decoupling technique. With PVC‐α,βd2, the conception of the tetrad was required to interpret the four observed peaks whose intensities changed with the polymerization temperature and the trans–cis composition of the monomer used.
Synthesis and characterization of branched polystyrene. Part II. Fractionation
Authors: Gosnell A. B. , Gervasi J. A. , Schindler A.
Published: April 2003

Fractionations have been carried out by a column‐elution method on mixtures of linear and branched polystyrene. These had been prepared by anionic polymerization followed by a coupling reaction to form star‐shaped branched polymers. Therefore, the components of the mixture were each of narrow distribution, and their molecular weights differed from each other as multiples of the original single chain length. For single chains in the 25,000–30,000 molecular weight range, separations were accomplished in which the multiples (number of branches) were 1, 2, 4, and 6. By this means, virtually monodisperse samples of the branched polymers could be isolated.
NMR spectra of model compounds of poly(vinyl chloride)
Authors: Abe Yasuaki , Tasumi Mitsuo , Shimanouchi Takehiko , Satoh Shiroh , Chûjô Riichiro
Published: April 2003

The NMR spectra of three stereoisomers of 2,4,6‐trichloroheptane as model compounds of poly(vinyl chloride) have been studied. Spectra were observed at 60 and 100 Mc./sec., both at room temperature and at high temperatures. A spin‐decoupling experiment was performed. Computational analysis of the spectra was carried out on an IBM 7090 computer. The difference of the chemical shifts of the two meso methylene protons at 60 Mc./sec. was found to be ca. 7 cps. for the isotactic three‐unit model while it was ca. 16 cps. for the isotactic two‐unit model or heterotactic three‐unit model. The spectra of poly(vinyl chloride) were interpreted reasonably on the basis of this result. Observed values of vicinal coupling constants of model compounds were interpreted as the weighted means of those for several conformations, and the stable conformations of the models were determined.
Polymerization of aromatic nuclei. X. Polymerization of benzene to p‐polyphenyl oligomers by nitrogen dioxide—aluminum chloride
Authors: Kovacic Peter , Hopper Roger J.
Published: April 2003

Benzene was polymerized to p‐polyphenyl oligomers by nitrogen dioxide–aluminum chloride. Polymer production was favored by AlCl3:NO2 ratios of at least 2, long reaction times, and higher temperatures. Evidence for the polymer structure was obtained from elemental analyses, oxidative degradation, solubility, molecular weight, functional group tests, low molecular weight products, and infrared and ultraviolet spectra. The chains contained small amounts of chloro, amino, hydroxyl, and carboxyl substituents. Molecular weight data on the benzene‐soluble portion (40–71%) revealed an average of 4–6 phenylene units per chain. Under altered conditions nitrobenzene could be obtained as the major product, indicating the sensitivity of the system to changes in reaction variables. With nitrobenzene as oxidant, a similar type of polymer resulted. The theoretical aspects are discussed.
Aromatic polyesterimides
Authors: Loncrini D. F.
Published: April 2003

Several 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

The 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

A 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

The 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

This 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

The 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

Poly(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

In 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

It 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

Kinetics 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

Isobutyl 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

Poly‐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

A 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

The 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

The 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

Epoxides, 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

The 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

The 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

The 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

Several 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

The 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

p‐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.
Polymerization kinetics in highly viscous media
Authors: De Schrijver F. , Smets G.
Published: April 2003

The influence of the viscosity of the reaction medium on the rate of polymerization of styrene has been examined by adding different amounts of inert polystyrene to pure monomer and its solutions in benzene. Azobisisobutyronitrile was decomposed photochemically (λ = 365 mμ) at 25°C. or thermally at 70°C.; its rate of decomposition was followed by ultraviolet spectrometry. The rate of formation of dimethyl‐N‐cyanoisopropylketenimine (DKI) was followed by infrared spectrometry (2020 cm.−1). The initiation efficiency was determined by the scintillation method with the use of a 14Clabeled initiator. The rate of polymerization was followed dilatometrically. An increase of viscosity does not affect the rate of decomposition of the initiator; on the contrary, during the photochemical decomposition, it causes an increase of DKI concentration and an appreciable decrease of efficiency (from 0.51 to 0.30). From the point of view of the rate of photopolymerization, an increase of viscosity causes a decrease in the order of the reaction with respect to the initiator (from 0.5 to 0.3) and an increase with respect to monomer from 1.5 to 2. These results are interpreted on the basis of a decrease of termination rate constant between two growing chains in favor of a termination reaction between a growing chain and a primary radical. These effects, due to an increase of the viscosity of the solution, on the initiation and termination reactions influence the rate of polymerization in opposite direction and compensate each other to approximatively 25%.
Studies on polymers containing functional groups. III. Charge‐transfer interaction between quinone and aza polymers
Authors: Sugiyama Hiroko , Kamogawa Hiroyoshi
Published: April 2003

Absorption maxima and equilibrium constants for charge‐transfer complexes between quinone and aza polymers, such as poly‐2‐vinylpyridine, poly‐4‐vinylpyridine, poly‐2‐methyl‐5‐vinylpyridine, and poly‐N‐dimethylaminomethylacrylamide, were determined spectrophotometrically. For comparison, those for charge‐transfer complexes between quinone and aza compounds, such as pyridine, methyl‐substituted pyridines, quinoline, triethylamine, and dimethylaniline were also presented. It was found that the equilibrium constants for polymer complexes are always larger than those for the corresponding monomer complexes, while the time required for attaining the equilibrium was longer for polymer complexes than for monomer complexes. In the interaction between quinone and poly‐N‐dimethylaminomethylacrylamide, two absorption maxima which gradually shifted towards each other were observed. The same phenomenon was found in the interaction between quinone and the corresponding monomer, triethylamine.
Fluorodienes. V. Copolymerization of 1,1,4,4‐tetrafluoro‐1,3‐butadiene with oxygen and nitric oxide
Authors: Putnam R. E. , Sharkey W. H.
Published: April 2003

1,1,4,4‐Tetrafluoro‐1,3‐butadiene reacts with oxygen to form a polyperoxide containing 1.0–1.1 peroxide groups for each diene unit. This polymer behaves like a typical peroxide. It explodes violently when heated to 120°C. or when subjected to shock, and it initiates polymerization of vinyl monomers at temperatures of 90°C. or higher. The tetrafluorobutadiene also copolymerizes with nitric oxide to give a highly crosslinked polymer containing three molecules of diene for each two molecules of nitric oxide.
γ‐radiation‐induced ionic polymerization of pure liquid styrene. II
Authors: Potter R. C. , Bretton R. H. , Metz D. J.
Published: April 2003

In this second paper of the series we present additional evidence that the γ‐radiation‐induced polymerization of very pure, ultradry styrene exhibits kinetics that can best be explained as due to one or more ionic processes, depending on the dryness of the sample. We have shown the effect of the various steps in the drying procedure on the observed kinetics, and we have described a preparative procedure which yields good reproducibility among independently prepared samples. Under these conditions, the rate of polymerization is proportional to the 0.70 power of the dose rate at 0°C.; there appears to be no wall effect; and the temperature coefficient for the process appears to be a complicated function, most probably a small negative value over the range of temperature (0–50°C.) and dose rates (∼103–105 rad/hr.) covered in this study. The maximum G value for disappearance of monomer which we have observed is of the order of 6 × 105 molecules of monomer/100 e.v. at 0°C. and a dose rate of 2 × 103 rad/hr.
Preparation and thermal stability of organometallosiloxanes and organometallic compounds
Authors: Delman A. D. , Stein A. A. , Simms B. B. , Katzenstein R. J.
Published: April 2003

This study covers the results of synthesis and investigation of thermal stabilities of several organometallosiloxanes and organometal compounds containing Group IV elements. Investigations indicate, in general, that heat resistance is related to the dissociation energies of the MO bonds, the number of organic groups connected to the metal atom, and the structure of the molecule as a whole. More specifically, the substitution of GeO and SnO bonds for some SiO linkages in organosiloxanes produces a reduction in heat stability. The influence of the GeO bond to decrease the resistance of siloxanes is less than that of the SnO linkage; an increase in the number of SnO linkages producing a corresponding decrease in heat stability of the organosiloxane. The resistances of the germoxysiloxanes to heat degradation are less than that which would be expected from indications given by the relative stabilities of more simple organometallic compounds.
Photolysis of poly(tert‐butyl acrylate) in the region of the glass transition temperature
Authors: Monahan Alan R.
Published: April 2003

The thin film (1 × 10−5 cm.) photolysis (2537 A.) of poly(tert‐butyl acrylate) under 1 atm. helium pressure has been investigated in detail. Isobutene was the only significant volatile product in the temperature range 20–110°C. The reaction was demonstrated to be initially a first‐order decomposition with an energy of activation of 3.3 kcal./mole in the glassy state. Above the glass transition temperature a value of 1.8 kcal./mole was found. The rate of isobutene formation is autoaccelerated when a minimum of one acrylic acid unit is generated per chain. The initial quantum yield for the formation of isobutene varies from 0.083 to 0.17 over the temperature range studied. There was no dependence of quantum yield on the exciting wavelength using sources of 1849, 2537, and 3660 A. The intensity exponent was found to be unity, consistent with first‐order decomposition kinetics.
Thermal degradation of polyacrylonitrile in the temperature range 280–450°c.
Authors: Monahan Alan R.
Published: April 2003

This paper presents a study of the thermal degradation of polyacrylonitrile of 13,000 to 43,000 number‐average molecular weight in vacuum over the temperature range 280–450°C. Sixteen products of the decomposition were identified by chromatographic and infrared analytical techniques. The five major products, i.e., cyanogen, hydrogen cyanide, acrylonitrile, acetonitrile, and vinylacetonitrile, were monitored at intervals during the decomposition using gas chromatography. Activation energies of 15 and 23 kcal./mole were calculated from initial rates of formation of HCN and cyanogen, respectively. The overall activation energy of the polymer degradation was found to be 3.6 kcal./mole. The residue of the decomposition in the temperature region 280–450°C. was suggested by infrared absorption measurements and elemental analysis to be a polymer of the structure
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The rate of production of vinylacetonitrile was found to be proportional to the production of the residual black poly‐1,4,4‐trihydronaphthyridine. A new photothermal degradation cell is also presented.
Kinetic studies of polymerization of propylene with active TiCl3–Zn(C2H5)2
Authors: Soga Kazuo , Keii Tominaga
Published: April 2003

In order to elucidate the structure of the Ziegler‐Natta polymerization center, we have carried out some kinetic studies on the polymerization of propylene with active TiCl3—Zn(C2H5)2 in the temperature range of 25–56°C. and the Zn(C2H5)2 concentration range of 4 × 10−3–8 × 10−2 mole/1., and compared the results with those obtained with active TiCl3—Al(C2H5)3. The following differences were found: (1) the activation energy of the stationary rate of polymerization is 6.5 kcal/mole with Zn(C2H5)2 and 13.8 kcal./mole with Al(C2H5)3; (2) the growth rate of the polymer chains with Zn(C2H5)2 is about times slower at 43.5°C.; and (3) the polymerization centers formed with Zn(C2H5)2 are more unstable. It can be concluded that the structure of the polymerization center with Zn(C2H5)2 is different from that with Al(C2H5)3.
Graft copolymers of phenolic novolacs on polyamide backbones
Authors: Ravve A. , Fitko C. W.
Published: April 2003

The formation of graft copolymers of novolacs on polyamide backbones was carried out under conditions which permitted product isolation and investigation. Grafting was performed on nylons 11, 610, 66, and 6 with the use of the condensates of formaldehyde with either phenol, p‐cresol, or p‐nonyl phenol. Physical properties of the reaction products were studied, and the proof of grafting was established by means of chemical, infrared, and NMR investigations.
Kinetics of urethane cleavage in crosslinked polyurethanes
Authors: Singh Ajaib , Weissbein Leonard
Published: April 2003

A series of clean, well‐defined polyurethane networks was synthesized from polyester glycols, 2,4‐tolylene diisocyanate, and 1,1′,1″‐trimethylolpropane by means that afforded precise control over the content of urethane groups per network chain. The thermal cleavage of these networks was studied using the technique of stress relaxation. Analysis of the stress‐relaxation data on each network structure revealed two exponential decay processes differing in rate by about an order of magnitude. The rate of the slower process, which dominates the overall stress decay, was shown to be directly dependent on the content of urethane groups per network chain. Positive identification of this process with urethane cleavage was thereby established. The kinetic and thermodynamic constants associated with urethane cleavage were then calculated from data on this process at different temperatures. The more transient stress‐decay process was not uniquely definable, but probably originated from the cleavage of one or more types of weak linkages found in small but variable proportions in the different polyurethane networks. The nature and origin of these weak linkages was discussed.
Costereosymmetric α‐olefin copolymers
Authors: Coover H. W. , McConnell Richard L. , Joyner F. B. , Slonaker D. F. , Combs R. L.
Published: April 2003

Copolymerization of propylene and 1‐butene with highly stereospecific three‐component coordination catalysts produced multiblock crystalline copolymers having stereo‐regular sequences of both propylene and 1‐butene. Copolymers containing from 3 to about 80% 1‐butene had two DTA melting points which were attributable to polypropylene and poly‐1‐butene crystallinity. Those containing from 18 to about 70% 1‐butene had x‐ray diffraction patterns showing peaks characteristic of polypropylene and form I poly‐1‐butene, but form II poly‐1‐butene crystallinity was never observed. The multiblock copolymer structure observed is also supported by the fact that the product of the reactivity ratios is greater than unity. The composition distributions of low‐conversion and continuously prepared copolymers were similar and relatively broad. For example, copolymers containing an average of 12% 1‐butene had species containing from 5–30% 1‐butene. High‐conversion copolymers had an even broader composition distribution due to the gradual increase of the 1‐butene concentration in the comonomer mixture as the copolymerization proceeded. The absence of homopolymers was demonstrated by fractionation. The ability to detect homopolymers was proved by the fact that a mixture of stereoregular polypropylene and poly‐1‐butene were readily separated. Increasing the amount of 1‐butene tended to decrease those properties dependent upon crystallinity such as hardness, tensile strength, stiffness, density, and melting point, but tended to improve significantly the impact strength, low temperature properties, and clarity of molded objects. These duocrystalline copolymers retained a much higher level of properties than that observed for random copolymers prepared with less stereospecific coordination catalysts.
Active site measurements in the coordinated anionic polymerization of propylene
Authors: Coover H. W. , Guillet J. E. , Combs R. L. , Joyner F. B.
Published: April 2003

The active‐site concentration was determined by using tritium labeling on three coordinate anionic catalysts containing violet titanium(III) chloride [hereafter referred to as titanium(III) chloride or TiCl3]. These catalysts were used in the polymerization of propylene. Three‐component catalysts, as well as two‐component catalysts, were investigated. Previous estimates of active‐site concentrations for (C2H5)2AlCl—TiCl3 catalysts appear to be too high by at least a factor of 10. The reason for the previous high estimates can be attributed to the marked reduction in chain‐transfer rate which occurs when the amount of polymer formed exceeds about 2 g./g. TiCl3. The chain‐transfer process appears to involve both alkylaluminum and monomer, but the effective monomer concentration is apparently not reduced until a later stage in the polymerization. The propagation rate is, therefore, unaffected; but the transfer rate is reduced, leading to the formation of polymer with much higher molecular weight. Extension of this process could lead to the observed broad distribution of molecular weights in polypropylene. As a result of the low value of active‐site concentrations [about 10−3 mole/mole titanium(III) chloride], the absolute value calculated for the propagation rate constant for propylene polymerization is in the range of 50 l./mole sec., and the average lifetime of a growing polymer molecule during the early stages of the polymerization is about 1 min.
Poly(vinyl fluoride) solution characteristics
Authors: Wallach M. L. , Kabayama M. A.
Published: April 2003

Nine unfractionated poly(vinyl fluoride) samples were characterized for molecular weight and polydispersity by means of sedimentation velocity, osmometry, and viscosity measurements. Molecular weights were in the range of 143,000–654,000 and Mw/Mn = 2.5–5.6. The Mark‐Houwink (M‐H) relation was established as [η] = 6.52 × 10−5 M0.80. The M‐H exponent is at the Flory‐Fox upper limit (0.80), as is characteristic of extended, polar polymers, in good solvents. The unperturbed chain dimensions, characteristic ratio and steric factor were derived by the methods of Stockmayer and Fixman and Kurata and Stockmayer. The steric factor is 1.7, which agrees with data reported for other poly(vinyl halides).
Copolymerization of trialkylvinyltin compounds
Authors: Minoura Yuji , Suzuki Yasuyuki , Sakanaka Yasuhiro , Doi Hiroyuki
Published: April 2003

The polymerizations of trimethylvinyltin (TMSnV) and tributylvinyltin (TBSnV) were carried out with the use of γ‐ray, radical, or ionic initiators. These monomers did not undergo the polymerization by themselves, but they did copolymerize with styrene (St) or methyl methacrylate (MMA) when a radical initiator was used. From the results obtained by the copolymerization, monomer reactivity ratios and Q–e values were obtained as follows: for the system St(M1)TMSnV, r1 = 44.8, r2 = 0.001, Q2 = 0.005, e2 = 0.962; for the system MMA (M1)TMSnV, r1 = 25.1, r2 = 0.03, Q2 = 0.036, e2 = 0.933; for the system St(M1)TBSnV, r1 = 16.0, r2 = 0.005, Q2 = 0.017, e2 = 0.822; for the system MMA(M1)TBSnV, r1 = 27.9, r2 = 0.03, Q2 = 0.031, e2 = 0.822. The abilities of TMSnV and TBSnV to polymerize are discussed on the basis of the Q and e values obtained.
Influence of catalyst depletion or deactivation on polymerization kinetics. III. Solution polymerization of acrylonitrile in N,N‐dimethylformamide at −30°C.
Authors: Chiang R. , Friedlander H. N.
Published: April 2003

The experimental results on homogeneous polymerization of acrylonitrile initiated with the sodium triethylthioisopropoxyaluminate, NaAlEt3S(i‐Pr), catalyst in DMF at −30°C. are compared with the prediction of equations based on a postulated mechanism. The agreement between the calculated and observed number‐average molecular weight combined with the kinetic data and the relationship between the conversion and the initial catalyst concentration provides a rigorous test concerning the validity of the equations and the mechanism of the polymerization. A plausible mechanism is postulated as follows: The initiation must be relatively fast in accordance with the rate equations and the growing polymer undergoes propagation, transfer (to monomer), and deactivation simultaneously. The infrared spectrum of the low molecular weight polymer prepared at a high catalyst concentration showed strong absorption at 2337, 2205, and 1620 cm.−1 but no absorption at 900 cm.−1, indicating that there are two nitriles in the polymer, one of which is conjugated. The possibility of having CHCH2 groups in the polymer is ruled out by the absence of the band at 900 cm.−1. In view of these facts, it is concluded that the polymer has a CHCHCN endgroup resulting from the transfer reaction.