bluuebunny/crossref_metadata_2025 huggingface dataset:
Emulsion polymerization. V. Lowest theoretical limits of the ratio kt/kp
Authors: Gardon J. L.
Published: April 2003

It is assumed that the propagating polymeric radicals have no diffusive mobility in the very highly viscous medium within latex particles. Chain growth takes place on a lattice when the polymeric radical reacts with a monomer present on a lattice site adjacent to that occupied by the reactive chain end. For termination, two radical chain ends must be positioned on adjacent lattice sites at the same instant. The kt/kp ratios calculated with this model are either similar to or somewhat lower than the values determined in emulsion polymerization experiments. A minimum value of kt/kp can be calculated with the aid of the rate equation of Part III by assuming that only “living” polymer is produced during emulsion polymerization. This value of kt/kp is significantly lower than that calculated by the lattice model. Since the value corresponding to the lattice model gives the slowest practically achievable termination rate, it is concluded from these calculations that emulsion polymerization cannot be carried out under conditions in which chain termination is completely suppressed.
Polymerization of acrylamide and methacrylamide photoinitiated by azidopentamminecobalt(III) chloride
Authors: Natarajan L. V. , Santappa M.
Published: April 2003

The kinetics of polymerization of acrylamide and methacrylamide, photoinitiated by azidopentamminecobalt(III) chloride in homogeneous aqueous acid medium was studied systematically. Monochromatic wavelengths 365, 405, and 435 mμ were employed for irradiation. Polymerization proceeded without any induction period, and the reaction was followed by measurements of rate of monomer disappearance (bromometrically), rate of complex disappearance (spectrophotometrically), and the chain lengths of the polymer formed (viscometrically). The dependences of the rate of polymerization on variables like light intensity, light absorption fraction by the complex, wavelength, monomer concentration, hydrogen ion concentration, nature of the acid used (HClO4, HNO3, and H2SO4), etc., were studied. The rate of polymerization of acrylamide depended on the unit power of monomer concentration and on the square root of light absorption fraction kε and light intensity I. The rate of methacrylamide polymerization was proportional to the unit power of monomer concentration and fractional powers of 0.25 and 0.30 of kε and I, respectively. A kinetic reaction scheme is proposed and discussed in the light of the experimental results, and it has been concluded that (1) the primary photochemical act is an electron transfer reaction from the azide ion to Co(III) in the complex, (2) initiation of polymerization is by azide radical, (3) termination is by mutual destruction of polymer radicals.
Anionic graft copolymerization of diene polymers with vinyl monomers
Authors: Minoura Yuji , Harada Hiroshi
Published: April 2003

A mixture of homopolymer and graft copolymer was obtained by adding the monomer at 0°C to the polylithiodiene solution. Styrene, methyl methacrylate, and acrylonitrile were used as the monomers. Polylithiodienes were prepared by the metalation of diene polymers, i.e., polybutadiene or polyisoprene, with the use of n‐butyllithium in the presence of a tertiary amine (N,N,N′,N′‐tetramethylethylenediamine) in n‐heptane. The graft copolymers were separated by solvent extraction and were confirmed by turbidimetric titration and elementary analysis. Oxidation of the polybutadiene–styrene grafts revealed that the molecular weight of the side chains was the same as the molecular weight of the free polystyrene formed. The grafting efficiency and grafting percentage were studied for polybutadiene–styrene graft copolymers prepared under various conditions.
Four‐center type photopolymerization in the solid state. II. Polymerization mechanism of 2,5‐distyrylpyrazine
Authors: Nakanishi Hachiro , Suzuki Yasuzo , Suzuki Fusae , Hasegawa Masaki
Published: April 2003

The polymerization mechanism of trans,trans‐2,5‐distyrylpyrazine (DSP) has been investigated and some crystal changes along with the polymerization process have been observed through polarizing microscope and x‐ray diffraction pattern. Information has been obtained on the active species, polymerization reaction type, and other factors such as light intensity, reaction temperature, or crystalline state. The polymerization of DSP occurs only in the solid state by photoirradiation. Reduced viscosity increases gradually with the increase of conversion and increases sharply above 80% conversion. Polymerization rate increases with the increase of light intensity and temperature. On the other hand, reduced viscosity decreases with the increase of temperature but does not depend on light intensity within the range investigated. The polymer obtained at low conversion as well as at high conversion has high crystallinity, and the direction of polymer axes is simply related to that of monomer crystal. It was concluded that the four‐center type polymerization of DSP proceeds topochemically by a photochemically induced stepwise mechanism.
Radiation chemical studies of protein reactions: Effect of irradiation liquid containing aromatic hydrocarbons and pH on viscosity
Authors: Nisizawa Mizuho
Published: April 2003

When protein is irradiated by γ‐rays from a 60Co source in various liquids containing aromatic hydrocarbons, such as benzene, naphthalene, and phenanthrene, the effect of the radiation varies with the irradiation liquids containing aromatic hydrocarbons. An empirical equation for the viscosity change was obtained. Protein irradiated by γ‐rays from a 60Co source in air showed the effect of pH on protein reactions. An empirical equation for the viscosity change was obtained.
Structure and reactivity of α,β‐unsaturated ethers. V. Cationic copolymerizations of ring‐substituted phenyl vinyl ethers
Authors: Fueno T. , Okuyama T. , Matsumura I. , Furukawa J.
Published: April 2003

Phenyl vinyl ether (M1) has been copolymerized with its various ring‐substituted derivatives (M2) in toluene at −78°C with stannic tetrachloride as catalyst. The substituents investigated include p‐CH3O, m‐CH3O, p‐CH3, m‐CH3, p‐Cl, and m‐Cl. The course of copolymerization was followed by gas chromatographic determinations of residual monomers, and the monomer reactivity ratios were evaluated by use of the integral form of the Mayo‐Lewis copolymerization equation. Except for the unusual case of the m‐CH3O derivative, the observed values of log (1/r1) were found to be linearly correlated with Hammett's σ constants, the reaction constant being ρ = −1.76 with the correlation coefficient r = 0.990. Comparisons of these results with the existing data for the styrene copolymerizations have enlightened the behavior of the oxygen atom in transmitting the electronic effects of ring substituents onto the reaction center.
Termination rate constant in radical polymerization
Authors: Ito Katsukiyo
Published: April 2003

On the basis of the assumption that the primary radical immerses into a polymeric radical, the rate constant of primary radical termination was derived. By applying and developing further the same treatment, the rate constant of chain termination was derived. This rate constant was experimentally confirmed. It was found that the rate constant of chain termination for the polymerization of some methacrylates depends on the distance of translation of radical chain end per collision, solvent viscosity, and the Taft polar constant for ester group.
Interfacial syntheses of polyphosphonate and polyphosphate esters. I. Effects of alkaline medium
Authors: Millich F. , Carraher C. E.
Published: April 2003

The effects on polymer yield and viscosity in the interfacial condensation of hydroquinone with phenylphosphonic dichloride as a function of the pH of the aqueous medium are reported. Reactions competing with polymer formation are discussed. The beneficial advantages in the use of soluble buffers or bases of limited water solubility to control pH are contrasted with results of conventionally used sodium hydroxide. The results of investigations of other comer pairs for which reaction conditions have not been optimized are also reported; desoxyribose and the diols: thymidine, resorcinol, 2,5‐dichlorohydroquinone, 1,3‐dihydroxyacetone, 1,4‐butanediol, tartaric acid, ethylene glycol, and 2,2‐dimethyl‐1,3‐propanediol are tabulated.
Polymerization rates by calorimetry. II
Authors: Andersen H. M.
Published: April 2003

By means of isothermal kinetic calorimetry, an automatic instantaneous record of polymerization rate can be obtained, independent of conversion. A large improvement in resolving kinetic events is thereby realized. Certain abrupt changes in rate due to electrolyte level have been observed.
Relation of the chemical structure of polycyanurates to thermal and mechanical properties
Authors: Nakamura Yoshiro , Mori Kunio , Tamura Kosaku , Saito Yoshiko
Published: April 2003

Forty polycyanurates were prepared by the interfacial polycondensation of 2‐substituted 4,6‐dichloro‐s‐triazines with various aromatic diols. Nitrobenzene was used as a solvent, aqueous sodium hydroxide as an acid acceptor, and a cationic emulsifier as an accelerator. The rate of reaction was largely increased by ultrasonic irradiation. The polymer yield was in the range 57–91%, and the reduced viscosity was 0.41–3.5. The polymers were soluble in chloroform, nitrobenzene, and o‐dichlorobenzene but insoluble in common organic solvents such as alcohol, acetone, and hydrocarbons. A clear film was obtained from the chloroform‐soluble polymers after evaporation of the solvent. The softening temperature and the thermal stability of each polycyanurate was significantly related to the substituent on the s‐triazine nucleus as well as to the diol component in the molecular chain. Polymers of favorable properties were derived from 2‐substituted 4,6‐dichloro‐s‐triazines with R = C6H5, N(C6H5)2, N(C6H11)2, N(C6H5)(SO2C6H4CH3), or carbazyl and aromatic diols such as 4,4′‐dihydroxybenzophenone, Bisphenol A, or phenolphthalein. These polymers showed tensile strength of 500–670 kg/cm2, elongation at break of 2.9–6.0%, and a minor weight loss at 300–350°C.
Differential thermal analysis of polyethylene under high pressure
Authors: Davidson Theodore , Wunderlich Bernhard
Published: April 2003

The design of a differential thermal analysis apparatus for use at elevated pressure is described. Experiments on melting and crystallization of folded‐chain crystals of polyethylene and poly(ethylene–butene‐1) copolymer, and melting of extended‐chain polyethylene crystals have been conducted at pressures up to 4200 bars. The precision in transition temperature measurement was ±1°C. The Clausius‐Clapeyron equation predicts the melting point increase with pressure at atmospheric pressure to be 32.0°C/kb. The melting point depression due to copolymerization remained constant over the complete pressure range analyzed on the poly(ethylene–butene‐1) used in this study. Crystallization of polyethylene is retarded at elevated pressures, and a 50% larger degree of supercooling is necessary at 5000 bars to give a crystallization rate equal to that observed at atmospheric pressure. The difference in melting point between folded‐chain and extended‐chain polyethylene increases from 8.4°C at 1 bar to 25.6°C at 3000 bars.
Statistical models in the study of stereospecific polymerization
Authors: Shelden Ronald , Fueno Takayuki , Furukawa Junji
Published: April 2003

Triad tacticity data obtained by NMR analysis have previously been interpreted in terms of two basic statistical models in order to elucidate the stereospecific polymerization mechanism. In this paper the characteristics of these two basic models for stereospecific polymerization, the enantiomorphic‐sites (EMS) model, and the polymer‐end control (PEC) model, are examined and compared. The tacticity values accessible to the two‐parameter EMS model, which includes the influence of the chain end unit, are shown to be highly restricted. Only about 20% of the isotacticity versus syndiotacticity plot is accessible to this model. To this extent the consistency of a set of triad tacticity data with the model can be tested. No such tacticity limits are exhibited by the two‐parameter PEC model, which includes the influence of the penultimate unit. Any set of tacticity values which can be interpreted in terms of the two‐parameter EMS model can also be interpreted in terms of the two‐parameter PEC model.
Bond rupture in highly oriented crystalline polymers
Authors: Peterlin A.
Published: April 2003

The strength‐limiting process in the fracture of semicrystalline fibers and highly oriented films is the rupture of tie molecules connecting the folded chain lamellae in the machine direction. This view is supported by the data on stress and temperature dependence of lifetime of fibers under load and on radical formation during the fracture experiment. The observed tensile strength, however, is about 10 times smaller and the number of fractured chains between 100 and 1000 times larger than expected on the basis of the known number of tie molecules in the fracture plane. This discrepancy is a consequence of the inhomogeneity of the micromorphology of fiber structure, which causes a much larger stress concentration on the most unfavorably located tie molecules than the average value one would expect in the case of perfectly uniform stress distribution on identical tie molecules. The fluctuation of amorphous layer thickness, of number and length of tie molecules, produces such a high stress concentration on some tie molecules throughout the sample that they rupture long before the average stress concentration is sufficient for chain fracture. By accumulation of damage caused by gradual chain rupture the weakening of the sample locally proceeds so far that at the maximum damage concentration, microcracks start to form, and the fiber breaks.
Surface energy effects for small holes or particles in elastomers
Authors: Gent A. N. , Tompkins D. A.
Published: April 2003

Expansion of a small spherical hole in a highly elastic solid is treated theoretically. Both elastic and surface energy terms are considered; the corresponding surface forces are assumed to be additive. The surface energy of the elastomer is assumed to be similar to that of simple liquids. Pressures or triaxial tensions required to inflate pre‐existing holes to an indefinitely large size are calculated. Small holes require extremely large pressures, of the order of 1000 atm for holes of 10 Å radius. These results suggest a means of determining the distribution of hole sizes in elastomers and account in principle for experimental observations of cavitation processes. Detachment of the elastomer from a small rigid inclusion is treated in a similar way. The general absence of dilation or cavitation on stretching carbon black‐filled elastomers is thus accounted for solely in terms of the small size of these filler particles.
Transition temperatures and structural correlations for cellulose triesters
Authors: Klarman A. F. , Galanti A. V. , Sperling L. H.
Published: April 2003

Six homologs of the cellulose triester series were found to exhibit, in general, three second‐order transitions as determined dilatometrically. A parallel study of torsional modulus versus temperature revealed one glass–rubber transition, which allowed molecular assignment of one of the above. The dependence of the remaining two transition temperatures on length of the ester group permits some speculation with regard to their origin. The glass–rubber and secondary transitions exhibit an inversion for cellulose trivalerate and higher homologs, the two secondary transitions occurring at temperatures higher than the glass–rubber transition. A possible explanation for this anomaly in terms of side‐chain crystallization is discussed.
Plastic deformation of poly‐4‐methylpentene‐1 crystals
Authors: Woodward A. E. , Morrow D. R.
Published: April 2003

The plastic deformation of poly‐4‐methylpentene‐1 (P4MP1) crystals on a unidirectionally drawn substrate has been investigated by electron microscopy. In addition to cracks spanned by fibrils and buckling perpendicular to the stretch direction, both features found in deformation studies of other polymers, a unique slip mechanism leading to sectorization of P4MP1 crystals is observed; deformation was also found to occur by means of localized lamellar thinning. The exact type of plastic deformation occurring in P4MP1 crystals is found to depend on the orientation of the lamellae with respect to the tensile axis. Some evidence for a periodicity on the fibrils studied is given.
Extended‐chain crystals. V. Thermal analysis and electron microscopy of the melting process in polyethylene
Authors: Prime R. Bruce , Wunderlich Bernhard , Melillo Louis
Published: April 2003

Differential thermal analysis and electron microscopy of partially molten, extended‐chain polyethylene crystals, grown under elevated pressure, was performed. It could be shown that melting peaks on the low temperature side of the main melting peak are due to narrowly distributed, low molecular weight polymer segregated in extended‐chain crystals. Superheating of crystals before melting increased with molecular weight and chain extension. The melting mechanism of extended chain crystals was shown to be a successive peeling off of chains which leaves the chain extension constant up to melting of the last crystal trace.
Electrochemical anionic polymerization of 4‐vinylpyridine in pyridine
Authors: Bhadani S. N. , Parravano G.
Published: April 2003

The preparation of poly‐4‐vinylpyridine (poly‐4VP) by electrochemical polymerization of 4‐vinylpyridine (4VP) in pyridine containing sodium tetraphenylboron (NaBPh4) is described. Information on the influence of monomer concentration, current density, polymerization rate, molecular weight, and electrochemical efficiency is presented. The polymerizations were performed under conditions of constant electrolysis current. Polymer formed in the cathodic compartment only, where a red‐orange solution developed after about 15 min of electrolysis time. The optical absorption spectra of these colored solutions were studied. Cyclic voltammograms of 4VP in pyridine and NaBPh4 are also reported, and the influence of the scan rate upon peak current is described. The results indicate that the polymerization was anionic and nonterminating. The characteristics of the electrochemical polymerization of 4VP in pyridine are compared with those of the same monomer in liquid NH3. In the former case, the catholyte was homogeneous, and polymer growth occurred in the liquid phase, while in the latter growth took place in a heterogeneous environment. Kinetic consequences of these physical differences are pointed out. Suggestions for the mechanism of this electrochemical initiation are advanced.
Hydrolytic polymerization of caprolactam. II. Vapor–liquid equilibria
Authors: Giori C. , Hayes B. T.
Published: April 2003

The system water–caprolactam–polymer at equilibrium is regarded as a solution consisting of two solvents (water and caprolactam) and one solute (polymer). The activities of water and caprolactam in equilibrium at 270°C in the range of 2–10 wt‐% total water content have been determined by vapor‐pressure measurements. Water shows large negative deviations from Raoult's law, as a consequence of the different size of water and polymer molecules. The partial molar free energies of mixing are compared with the expressions derived from the Flory‐Huggins theory of polymer solutions; the results are not conclusive, but seem to indicate a qualitative agreement with the theory. The increase in vapor pressure during polymerization in sealed systems and the water dependence of the polycondensation equilibrium are discussed and explained in terms of water activity changes.
Synthesis of poly‐2‐oxazolidones from diisocyanates and diepoxides
Authors: Dileone R. R.
Published: April 2003

Poly‐2‐oxazolidones of high molecular weight have been synthesized from diisocy anates and diepoxides. The synthetic method was first developed for the model compound 3‐phenyl‐5‐phenoxymethyl‐2‐oxazolidone prepared from phenyl isocyanate and phenyl glycidyl ether. Conditions found most suitable for a high yield involve slow addition of isocyanate to a solution of epoxide and catalyst, temperatures of 160°C or higher, and a catalytic amount of n‐butoxylithium in 1‐butanol. The same procedure was used to prepare high molecular weight poly‐2‐oxazolidones. The polymer structure was confirmed by infrared spectroscopy and elemental analysis. All polymers prepared were of sufficient molecular weight to be compression molded. The bulk mechanical properties characterize poly‐2‐oxazolidones as potentially useful engineering thermoplastics. A mechanism for oxazolidone formation is proposed.
γ‐ray and ultraviolet graft copolymerization of maleimide by vapor‐phase method
Authors: Hayakawa Kiyoshi , Yamakita Hiromi , Kawase Kaoru
Published: April 2003

Graft copolymerization of maleimide onto ethyl cellulose and polyethylene films by using its sublimation vapor was carried out under γ‐ or ultraviolet irradiation. When polyethylene film was used as a backbone polymer the grafting reaction proceeded without a perceptible sorption of monomer, while a considerable amount of monomer was captured into ethyl cellulose film and grafting of the sorbed monomer was observed. The monomer seemed to be monomolecularly dispersed in this film. The presence of air retarded the reaction. The grafted films were characterized by strong infrared absorption bands due to polymaleimide branching. The fractions assigned to the graft copolymer were isolated from the grafted films by selective elution. The grafted branches were supposed to be very short, judging from the polymaleimide contents of those fractions.
Influence of microstructure on the tensile behavior of acrylic copolymers
Authors: Majerus John N. , Pitochelli Anthony R.
Published: April 2003

Uniaxial tensile properties were determined for two series of copolymers: ethyl acrylate–acrylic acid and butyl acrylate–acrylic acid. The comonomer ratio was varied from 85/15 to 95/5 and various molar ratios of a difunctional carboxylate epoxy crosslinker were used. The master modulus curves indicated that increasing the amount of crosslinker and/or increasing the number of crosslink sites per chain caused both the equilibrium modulus and the transition temperature to increase while increasing the bulk of the side groups decreased both the modulus and transition temperature. All the master ultimate strain curves exhibited a maximum value corresponding to some value of reduced time τc and exhibited a shape analogous to a lognormal distribution function with nonzero asymptotes. The maximum ultimate strains were found to be a nonlinear function of the crosslink density and to occur at higher values of temperature and/or lower values of strain rate when either the amount of crosslinker or the relative frequency of the crosslink sites increased. Replacing the pendant ethyl group with a butyl group caused the maximum ultimate strains to occur at temperatures about 60°F lower than the corresponding ethyl acrylate copolymer. This replacement also decreased the magnitudes of the maximum ultimate strains associated with the same crosslink density. It was concluded that the chemical efficiency of the crosslink sites decreases with decreasing relative frequency of the crosslink sites along the prepolymer. Furthermore, the crosslink efficiency decreased as the length and flexibility of the nonreactive side groups increased. The dependency of the actual crosslink density was found to be critically influenced by the chemical crosslink efficiency. A molecular model involving both chain entanglements and chemical corsslinks is postulated which explains qualitatively the observed behavior of the master ultimate strain data.
Polymerization of sodium 2‐sulfoethyl methacrylate in aqueous solution
Authors: Kangas D. A.
Published: April 2003

The rate of sodium 2‐sulfoethyl methacrylate (SEMΘNa⊕) polymerization in aqueous solution was measured as a function of temperature, ionic strength, K2S2O8, and SEMΘ‐Na⊕ concentration. The ratio of rate constants, kpkt−1/2(fkd)1/2, increases with decreasing ionic strength. Because SEMΘNa⊕ is itself an ionic salt, the ratio of polymerization rate constants increases with decreasing monomer concentration. The change in ratio of rate constants as a function of ionic strength can be described by an equation derived from the limiting form of the Debye‐Hückel theory. The value of the effective ionic charge on the polymeric growing radical is 3, as calculated by means of the derived equation.
Etude par RPE des radicaux libres daus le tétraoxane irradié
Authors: Saito E. , Cannavo C. , Hayashi K.
Published: April 2003

The free radicals induced in tetraoxane at liquid nitrogen temperatures by 60Co γ‐rays have been studied by ESR. The powder spectrum as well as he spectra of the single crystal rotated around the b axis have been studied through their modifications from −196°C up to + 80°C. These spectra show that at low temperatures two radicals exist conserving the cyclic nature of the parent molecule. During the course of annealing, starting at −140°C and towards −85°C they are gradually replaced by radicals with a linear structure, this being the first step in the post‐polymerization process of tetraoxane. Further increase in temperature leads to radical sites situated on the polymer chains. At low temperatures evidence has also been found for the formyl radical, radical pairs, and a photo‐sensitive radical.
Use of carbon suboxide to obtain block and graft copolymers. II. Grafting of carbon suboxide on polyethylene
Authors: Bukowski Andrzej , Porejko Stansislaw
Published: April 2003

Experiments have been carried out on grating of carbon suboxide on nonactivated polyethylene films and on films previously activated by ultraviolet irradiation and by γ‐irradiation. The experiments gave a grafted copolymer. A grafted copolymer was also obtained on grafting carbon suboxide in solution on polyethylene films preactivated by means of ozonization at 70°C. Examination of the copolymer indicated its structure to be cross linked. It has been proved that below 50°C single molecules of carbon suboxide react with polyethylene. The polyethylene thus modified is then easily surfacedyed.
Thermal degradation of copolymers of styrene and acrylonitrile. I. Preliminary investigation of changes in molecular weight and the formation of volatile products
Authors: Grassie N. , Bain D. R.
Published: April 2003

By the use of thermal volatilization analysis (TVA), 292°C was chosen as a suitable temperature for a preliminary experimental survey of the thermal degradation of styrene–acrylonitrile copolymers. TVA also indicated that there is no fundamental change in reaction mechanism as the acrylonitrile content of the polymer is increased from zero to 33.4% although there is a progressive increase in the rate of volatilization. The increase in the rate of volatilization over that of polystyrene is directly proportional to the acrylonitrile content of the copolymer. From the changes in molecular weight which occur during the reaction it is clear that the primary effect of the acrylonitrile units on stability is to cause an increased rate of chain scission, but there is a small proportion of “weak links” which are associated with the styrene units and which are broken instantaneously at 292°C. The number of monomer molecules liberated per chain scission, the zip length, is about 40 for polystyrene in the initial stages of degradation and decreases only to the order of 20 even in copolymer containing 24.9% acrylonitrile. Thus the unzipping process is not severely affected by the acrylonitrile units; this is borne out by the fact that acrylonitrile appears among the products in very much greater concentrations than from pure polyacrylonitrile. The proportion of larger chain fragments (dimer, trimer, etc.) also increases with acrylonitrile content.
High‐resolution NMR spectrum of deuterated and undeuterated poly(propene sulfone)
Authors: Ivin K. J. , Navrátil M.
Published: April 2003

100 MHz spectra have been obtained for DMSO‐d6 solutions of poly(propene sulfone) made from propene (I), propene‐1,1,3,3,3‐d5 (II), propene‐cis‐1,2‐d2 (III) and propene‐2‐d1 (IV) by copolymerization with sulfur dioxide; also by oxidation of poly‐(propene‐2‐d1 sulfide)s of different tacticities.

The following chemical shifts and coupling constants were determined: τA = 6.06, 6.12, 6.19; τB = 6.43, 6.51; τC = 6.05; τCH3 = 8.44; J = 6.5 Hz; JAB = 14.0 Hz.
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Both the A and B protons are sensitive to tacticity, giving rise to five lines in the methylene spectrum of III and ten lines, consisting of four overlapping AB quartets, in the methylene spectrum of IV. From a consideration of the relative intensities of the peaks in the spectra of poly(propene‐2‐d1 sulfone)s of different tacticities the following assignment to triad structures has been made: τA: 6.06 hi, 6.12 i and s, 6.19 hs; τB: 6.43 hi and i, 6.51 s and hs. The proportions of the four triad‐structures correspond to a single‐parameter model for chain growth in which the probability of an isotactic placement σ is 0.50 for the free‐radical copolymerization of propene and sulfur dioxide, 0.55 for the ZnCO3‐initiated polymerization of propene sulfide and 0.64 for the CdCO3‐initiated polymerization of propene sulfide. The spectrum of III shows that for polymer made at −90°C, one mode of addition is preferred. By analogy with other systems it is assumed that this is trans addition. For polymer made at 60°C, both trans and cis addition occur in nearly equal proportions. Assuming that cis addition occurs via the inversion of the intermediate alkyl radical, the activation energy for inversion is found to exceed that for addition of sulfur dioxide by 2.7 kcal/mole (11 kJ/mole). This appears to be the first reported case of a preferred mode of addition to an ethylenic bond in a free radically initiated polymerization.
Emulsion polymerization of vinyl acetate. II
Authors: Litt M. , Patsiga R. , Stannett V.
Published: April 2003

The emulsion polymerization of vinyl acetate was investigated at low ionic strengths and has quite unusual kinetics. The rate of polymerization is dependent on the initiator concentration to the first power and independent of soap concentration. In seeded polymerizations, the rate of polymerization depends on initiator to the 0.8 power, particle concentration to the 0.2 power, and monomer volume to 0.35 power. In all cases the rate of polymerization is almost independent of monomer concentration in the particles until 85–90% conversion. These results were rationalized by the following mechanism: (a) polymerization initiates in the aqueous phase because of the solubility of the monomer and is stabilized there by adsorption of ionic soap on the growing polymer molecule; (b) the growing polymer is swept up by a particle at a degree of polymerization (under our conditions) of about 50–200. Growth continues in the particle. This sweep‐up is activation‐controlled as both particle and polymer are charged. (c) Chain transfer to the acetyl group of monomer gives a new small radical which cyclizes to the water‐soluble butyrolactonyl radical, and reinitiates polymerization in the aqueous phase; (d) the main termination step is reaction of an uncharged butyrolactonyl radical with a growing aqueous polymer radical. A secondary reaction at low ionic strength is sweep‐up of an aqueous radical by a particle containing a radical. At high ionic strength, this is the major termination step. The unusual kinetic steps are justified by data from the literature. They are combined with the usual mechanisms operating for vinyl acetate polymerization and kinetic equations are derived and integrated. The integral equations were compared with the experimental data and shown to match it almost completely over the whole range of experimental variables.
Calculation of the glass transition temperatures of polymers. Part I. Homopolymers and copolymers with alkyl side chains
Authors: Lee W. A.
Published: April 2003

Four equations, relating the glass transition temperatures Tg of homopolymers and copolymers to invariant additive temperature parameters (ATP) associated with their constituent groups, but weighted in different ways, have been applied to the calculation of the Tg of seven series of polymers having alkyl side chains. It is shown that the Tg of the 32 polymers considered may be calculated, within 7°K of the observed values, without the use of interaction coefficients from 15 independent variables, representing summations of the ATP's. The present calculations are confined to those structures which may be formed by a recombination of the structures corresponding to these independent variables. It is an essential feature of the approach that a distinction is made between groups with different nearest neighbors. Alternative methods of calculation are considered. The temperature parameter for a sequence of three or more methylene groups is estimated as 141°K, in conformity with the transition in polyethylene at 148°K. Nearest‐neighbor interactions, stereoregularity, and crystallinity effects are discussed.
Hyperelectronic polarization, a physical property of EKA‐conjugated polymers
Authors: Wyhof J. R. , Pohl H. A.
Published: April 2003

Hyperelectronic polarization is a molecular mechanism which can produce very large dielectric constants in certain macromolecular solids. The present paper reports studies of the frequency, pressure, and temperature responses of this extreme polarization and related electronic conductivity on a variety of new polymers. The polymers studied were quinazone, metallo‐organic dithiooxamide type, and pyropolymers. The latter were examined in pure and in metal‐doped forms. Dielectric constants ranging from 10 to 500 were observed for the quinazone polymer, which was, incidentally, found to exist in two forms. Dielectric constants ranged from 30 to 100 for the metallo‐organic polymer from 25 to 10,000 for the pure pyropolymer and were of the order of 500 for a calcium doped pyropolymer. One set of nickel‐doped pyropolymers was found to conduct quite well (resistivity 76.8 × 10−6 ohm‐cm).
Simultaneous measurement of vapor diffusion and solubility coefficients in polymers by frequency response techniques
Authors: Evnochides S. K. , Henley E. J.
Published: April 2003

An experimental technique for the simultaneous measurement of solubility and diffusion coefficients in polymers by frequency response techniques has been developed. A sample of polymer suspended from an electrobalance is exposed to a permeating gas whose pressure is being varied sinusoidally at ultra‐low frequencies. The phase angle and amplitude of the weight changes are measured as a function of the frequency of the pressure wave. It is shown that in the linear range the diffusivity coefficient for polyethylene–ethane calculated from the phase angle lag and the Henry's law solubility and the diffusivity obtained from the amplitude ratios are in excellent internal agreement and also agree with values obtained from transient measurements.
Unit‐cell dimensions of bulk‐ and solution‐crystallized linear polyethylene
Authors: Kitamaru R. , Mandelkern L.
Published: April 2003

The unit‐cell dimensions and density, at room temperature, of bulk‐ and solution‐crystallized linear polyethylene have been determined. The macroscopic measured densities for the bulk‐crystallized samples ranged from 0.917 to 0.993 g/cc, and the lattice parameters were found to be independent of the sample density. In contrast, for solution‐formed crystals, despite the limited range in macroscopic densities that can be attained, there is a systematic variation in the a and b dimensions with the measured density and the crystallite thickness. The implication of these results for the calculation of the degree of crystallinity and the interpretation of certain infrared bands are discussed.
Small‐angle light scattering by random assemblies of incomplete spherulites. II. Truncated spherulites
Authors: Stein Richard S. , Picot Claude
Published: April 2003

Previous theoretical calculations of the scattering from spherulites are for isolated complete spheres, whereas most spherulitic polymer samples contain truncated spherulites as a result of impingement by other spherulites. The effect of such truncations on the scattering patterns for two‐dimensional spherulites is explored as a function of the size, number and location of the truncations. The scattering of severely truncated spherulites is modified, particularly with regard to the enhancement of the HV scattering at small angles. However, reasonable amounts of truncation corresponding to experimentally observed structures do not produce appreciable modification of the pattern so that the neglect of truncation will not lead to appreciable error in the estimated spherulite size from light scattering.
Characterization of cellulose acetates by nuclear magnetic resonance
Authors: Goodlett V. W. , Dougherty J. T. , Patton H. W.
Published: April 2003

An NMR method for determining the distribution of acetyl groups in cellulose acetates was developed. Treatment of cellulose acetates with acetyl‐d3 chloride gave products having simple spectra which could be analyzed quantitatively to give the distribution of acetyl groups in the original sample. The method was applied to studying (1) the hydrolysis of cellulose triacetate with ammonia, (2) the acetylation of cellulose acetate with acetyl chloride, and (3) the acetylation of cellulose acetate with acetic anhydride.
Radiation‐induced solid‐state polymerization of trioxane under high pressure
Authors: Yamazawa Yuzo , Iwai Tadashi , Ito Akihiko , Hayashi Koichiro
Published: April 2003

The in‐source polymerization of trioxane in the solid state was investigated over a wide range of temperature and pressure, i.e., from 30 to 140°C and up to 7000 kg/cm2, respectively. In the polymerization that was carried out slightly below the melting point under pressure, the higher the pressure, the higher the rate of polymerization. It was confirmed that the maximum rate of solid‐state polymerization of trioxane occurs near the melting points, even under elevated pressure. The rate of polymerization decreased with increasing pressure at constant temperature. The shape of the time–conversion curves may be classified into two types, i.e., one which is typical of high pressure and low temperature, and the other which is typical of low pressure and high temperature. Changes in the shape of the conversion—intrinsic viscosity curves occurred coincidentally. Thus, three regions for the different “polymerization characteristic” were determined as functions of polymerization temperature and pressure. Explanations are given for the above‐mentioned polymerization characteristic.
Orientation of polymer molecules during melt spinning. I. Estimation of degree of orientation by retraction above Tm
Authors: Furukawa Junji , Kitao Toshio , Yamashita Shinzo , Ohya Seigo
Published: April 2003

The elastic deformation ratio by spin‐stretching was estimated by means of thermal retraction technique, data for a melt‐spun filament from a crystalline polymer were compared with those from an amorphous one. The necessary conditions for equilibrium retraction were determined as 7 min at 170°C for amorphous polystyrene and 30 min at 180°C for high‐density polyethylene. The effects of molecular weight and melt draw ratio on the retraction behavior were discussed and concluded to be negligible. The apparent activation energies of viscous flow were calculated from the temperature dependence of the retraction curves. The activation energy for polystyrene decreases with increasing temperature of retraction, as predicted by the WLF equation, and that of polyethylene obeys Arrhenius law (about 12 kcal/mole). This may be attributed to the difference in glass transition temperatures of the two polymers. By measuring the effective melt draw ratio of the resultant filaments of different melt draw ratio, it was made clear that the elastic deformation increases with increasing apparent melt draw ratio. Finally, the optical anisotropy of the filaments was related to the deformation ratio. It was concluded that Kuhn and Grün's equation may be applicable for polystyrene but not for polyethylene.
Ladder pyrrolone structures with anthraquinone recurring units
Authors: Szita Jeno , Brannigan L. H. , Marvel C. S.
Published: April 2003

1,2,4,5‐Tetraaminoanthraquinone and 1,4,5,8‐naphthalene‐tetracarboxylic acid dianhydride react in dimethylacetamide to give a tetrameric prepolymer with balanced endgroups of anhydride and diamine. When this prepolymer is carefully treated with polyphosphoric acid at elevated temperature it is converted to a soluble polypyrrolone type structure with an inherent viscosity of 2.3–2.7. Polymers of this molecular weight can be wet‐spun into pliable fibers from methanesulfonic acid. The TGA curve in air shows little weight loss below 550°C. The polymer can also be solubilized by reduction with sodium dithionite in alkaline aqueous dimethyl sulfoxide.
Polyaromatic pyrazines: Synthesis and thermogravimetric analysis
Authors: Higgins Jerry , Jones Joe F. , Thornburgh Allan
Published: April 2003

The syntheses of five polyaromatic pyrazine polymers are described. These polymers were synthesized by the condensation of bis‐α‐haloaromatic ketones with ammonia in N,N‐dimethylacetamide (DMAc) solvent in the presence of air or peroxides. The condensation of bis‐p‐(α‐bromoacetyl)benzene (IIIa), bis‐p,p′‐(α‐chloroacetyl)biphenyl (IIIb) bis‐p,p′‐(α‐chloroacetyl)diphenyl ether (IIIc), bis‐p,p′‐(α‐chloroacetyl)diphenylmethane (IIId), and α,α′‐dibenzoyl‐α,α′‐dibromo‐p‐xylene (V) under these reaction conditions gave poly[2,5‐(1,4‐phenylene)pyrazine] (IVa), poly[2,5‐(4,4′‐biphenylene)‐pyrazine] (IVb), poly[2,5‐(4,4′‐oxydiphenylene)pyrazine] (IVc), poly[2,5‐(4,4′‐methylenediphenylene)pyrazine] (IVd), and poly[2,5‐(1,4‐phenylene)‐3,6‐diphenylpyrazine] (VI), respectively. Thermogravimetric analysis (TGA) of these polymers showed them to be thermally stable up to the temperature range of 450–550°C in air for short periods of time. The inherent viscosities of these polymers ranged from 0.18 to 1.30.
Preparation and structure of chlorinated poly(vinyl flouride)
Authors: Bacskai R. , Lindeman L. P. , Adams J. Q.
Published: April 2003

The low‐temperature chlorination of poly(vinyl fluoride) (PVF) proceeds readily in CCl4 suspension. The rate of chlorination is high initially, but the reaction slows down considerably when the chlorine content of the polymer reaches 40–50%. At long reaction times, polymers containing 62% chlorine (1.88 chlorine atoms per monomer unit) can be obtained. As the degree of chlorination increases, the solubility of PVF in organic solvents increases. Polymer crystallinity and polymer softening point decrease with chlorination. Polymers containing 40% chlorine appear to be completely amorphous by x‐ray analysis. In this respect, PVF differs from poly(vinyl chloride) (PVC), where chlorination increases the softening point, and it resembles polyethylene where both crystallinity and softening point decrease with chlorination. 19F NMR analysis of the polymers indicates that up to a degree of chlorination of 1 chlorine atom per monomer unit, 50% of the substitution occurs on the α‐carbon of the PVF molecule. This result is very different from the predominant β‐chlorination of PVC reported by several workers. The chemical selectivity observed in the chlorination of PVF is in quantitative agreement with the results of free‐radical chlorination of organic compounds and can be rationalized by considering the size and the electronic properties of the fluorine atom. The results of 1H NMR analysis are also in support of a polymer structure where the chlorine atoms are distributed between α‐ and β‐carbons. Based on a comparison of the 19F and 1H NMR data, the average composition of chlorinated PVF at the 1 chlorine atom per monomer unit level can be represented as: C200H200F100Cl100 = (CH2)63(CHF)50(CHCl)24(CClF)50‐(CCl2)13.
Radiation‐induced crosslinking of cellulose with acrolein
Authors: Ishanov M. M. , Azizov U. A. , Nigmankhodzhayeva M. S. , Usmanov Kh. U.
Published: April 2003

The process of radiation‐induced crosslinking of cellulose is found to be highly influenced by radiation dosage and dose as well as by the solvents used and their concentration. The best crease resistance has been obtained in cases when cellulose is crosslinked with acrolein in the vapor phase. Moreover, the process is entirely radiation‐induced and practically no homopolymer is formed. Chemical analysis and investigations of infrared spectra indicate that crosslinking proceeds on vinyl as well as on aldehyde groups of acrolein.
Anionic graft polymerization of propylene sulfide on cellulose. II. Absorption of iodine, silver, and mercury on the graft polymers
Authors: Cohen Eliahu , Avny Yair , Zilkha Albert
Published: April 2003

The adsorption of iodine, silver nitrate, and mercuric chloride by cellulosic membranes grafted with polypropylene sulfide was investigated. It was found that the grafted polypropylene sulfide adsorbed iodine by complexation from aqueous solution or from gaseous phase. Adsorption from water led to the formation of a complex with molar ratio of I2 to propylene sulfide units of 1, and that while the complex formed from gaseous iodine had a molar ratio I2 to propylene sulfide approaching 2. Most of the sulfide groups participated in complexation. It was found that the complexation of the polysulfide was accompanied by degradation which was attributed to halogenation of the polysulfide at the tertiary carbon atoms. The iodine complex was more stable in water than in organic solvents, where most of the iodine was desorbed. The graft polymers adsorbed also by complexation silver nitrate and mercuric chloride. Adsorption could be described by a Freundlich type isotherm. At low concentrations most of the silver nitrate present in solution was adsorbed.
Free‐radical polymerizations initiated by triethylaluminum–cuprous chloride mixtures
Authors: Kawai Wasaburo , Ogawa Masaji , Ichihashi Taichi
Published: April 2003

Methyl methacrylate was polymerized by triethylaluminum—cuprous chloride catalyst. A study of the polymerization kinetics indicated that the overall rate was represented by the equation, Rp = K[AlEt3] [CuCl]½ [M]2. The overall activation energy was 16.5 kcal/mole. From ESR measurement and the results of copolymerization of methyl methacrylate with styrene, it was suggested that the catalytic system has the character of a radical initiator. A polymerization scheme was also proposed.