bluuebunny/crossref_metadata_2025_split huggingface dataset:
Persistent polarization in polymers. I. Relationship between the structure of polymers and their ability to become electrically polarized
Authors: Miller M. L. 
Published: April 2003

AbstractThe ability of various polymers to acquire persistent polarization (i.e., to become electrets) was investigated. Polarization was induced in the polymers by two methods: (a) by cooling under a voltage drop and (b) by cooling with flow under pressure. There was found to be an optimum temperature for electret formation by either method. This optimum temperature was roughly 37°C. above Tg when polarization was produced by application of a voltage drop and roughly 57°C. when polarization was produced by flow under pressure. Crystallinity and the nonhomogeneities present in blended polymers were harmful to electret formation, but a small critical amount of ionic impurity was helpful.
Molecular structure of polyethylene. XIII. An improved cryoscopic method for determining number‐average molecular weight of polyethylene
Authors: Newitt E. J. , Kokle V. 
Published: April 2003

AbstractThe determinations of the number‐average molecular weight of polyethylene by cryoscopy has been improved, permitting precise measurements with both linear and branched polyethylenes in the molecular weight range 4,000–30,000. Improvements include a cryometer of new design, a lower‐melting cryoscopic solvent containing a nucleating agent to control supercooling and rate of crystallization of the solvent, and more precise measurement of freezing point depression. Polyethylene samples are dissolved in hexamethylbenzene admixed with 0.1% of cadmium iodide, and steady‐state freezingpoint depressions are measured with a thermistor to a maximum sensitivity of 5 × 10−5°C. Molecular weight measurements are reproducible to within ±10%. The cryoscopic apparatus and procedure are described in detail, and results obtained with samples of linear and branched polyethylene are presented and discussed.
Structure of pressure‐crystallized polypropylene
Authors: Kardos J. L. , Christiansen A. W. , Baer Eric 
Published: April 2003

AbstractThe structure of polypropylene crystallized at pressures up to 5000 atm. has been studied. Upon slow cooling from the melt at 320 atm., the γ modification, previously found only in low molecular weight and stereoblock fractions, begins to appear in small amounts in addition to the normal α monoclinic form. As the pressure is increased further, a larger proportion of the sample crystallizes in the γ form until, at 5000 atm., only the γ modification is present. X‐ray and DTA studies show that the γ form of polypropylene transforms to the normal α modification at a temperature only slightly below the γ melting point. Evidence is presented which favors the occurrence of a solid‐state transition as a model of transformation to the α form. Results from isothermal crystallizations at low supercoolings and annealing experiments under high pressure show that the melting point of the γ modification of polypropylene is very sensitive to crystallite perfection.
Fibrous/lamellar microstructure in polyethylene
Authors: Williamson R. B. , Novak R. C. 
Published: April 2003

AbstractA shish‐kebab microstructure consisting of both fibrillar and lamellar crystals has been observed with transmission electron microscopy in polyethylene crystallized from the melt. The parallel fibrillar crystals are aligned at right angles to closely spaced lamellar crystals. The lamellar crystals were grown epitaxially on a few fibrillar crystals obtained by shearing a solution which preceded the creation of the thin melt film. The fibrillar/lamellar microstructure revealed by dissolving a paraffin diluent illustrates two aspects of oriented structures not reported previously: (a) a high density of intercrystalline links parallel to the original nucleating fiber connecting the lamellar crystals, and (b) a connectivity between lamellar crystals growing on different nucleating fibers. The samples are observed to have a continuous two‐dimensional crystalline superstructure.
N‐Alkyl‐substituted polyamides and copolyamides having long methylene chain units
Authors: Saotome Kazuo , Komoto Hiroshi 
Published: April 2003

AbstractN‐Alkyl‐substituted polyamides and copolyamides have been prepared from N,N′‐dialkyl p‐xylenediamine and N,N′‐dialkyl hexamethylenediamine with long‐chain aliphatic dicarboxylic acids. Crystalline N‐alkyl polyamides were obtained by the use of dicarboxylic acids higher than C16. The melting point versus composition curves for the crystalline N‐alkyl copolyamides which were prepared from a mixture of diamine and the corresponding N‐alkyl diamine with α,ω‐octadecanedioic acid showed convex type plots. X‐ray examination of N‐alkyl copolyamides revealed that all the systems behaved in the same basic manner, the second component was always present without dissolving in the lattice of the first. Dilatometric curves showed two inflection points, corresponding to the melting points of the N‐alkyl and unsubstituted polyamides respectively. From these results, a block copolymer structure was suggested for the N‐alkyl copolyamides. The mechanisms for the formation of the block structure were also discussed.
Polyurethanes and polyureas having long methylene chain units
Authors: Saotome Kazuo , Komoto Hiroshi 
Published: April 2003

AbstractPolyurethanes and polyureas containing long methylene chain units have been prepared from the following six series of monomer combinations; aliphatic diisocyanates with aliphatic glycols or diamines, methylene bis(4‐phenyl isocyanate) with aliphatic glycols or diamines, and p‐xylylene diisocyanate with aliphatic glycols or diamines. A good linear relationship was noted between the polymer melting points of each series against the concentration of functional groups. Both polyurethanes and polyureas from p‐xylylene diisocyanate showed higher melting points than those from methylene bis(4‐phenyl isocyanate) with corresponding aliphatic monomers. The relations between the melting points of these polymers with long methylene chains, including polyamides which were previously reported, and the chain components were discussed. The higher melting points of polymers containing p‐xylylene group are attributed to the high rigidity of this group.
NMR study of poly(vinyl formate)
Authors: Ramey Kermit C. , Lini David C. , Statton Gary L. 
Published: April 2003

AbstractThe high resolution nuclear magnetic resonance spectrum of poly(vinyl formate), yielded, upon examination at 100 Mc./sec., and under the conditions of decoupling, information on the three tactic forms present. The normal and decoupled spectra indicate that only the CHO resonance is sensitive to the stereochemical configuration. The three components of the CHO resonance are tentatively assigned to isotactic (i), heterotactic (h), and syndiotactic (s) triads with increasing field strength, respectively. This assignment was made on the basis of poly(vinyl alcohol) and poly(vinyl acetate) derived from poly(vinyl formate). The results show that the tacticity is slightly dependent upon the temperature of free‐radical polymerization.
High‐pressure reactions. II. γ‐Ray polymerization of acrylamide
Authors: Prince M. , Hornyak J. 
Published: April 2003

AbstractThe post‐irradiation effect of high pressure on the γ‐ray‐initiated solid‐state polymerization of acrylamide has been described. Polymer conversion was found to increase significantly with applied pressure. The molecular weight of polymer increases with pressure.
Kinetics of nonequilibrium methylsiloxane polymerization and rearrangement
Authors: Adams Frederick P. , Carmichael Jack B. , Zeman Ronald J. 
Published: April 2003

AbstractNonrandom reactions were demonstrated experimentally during the polymerization of (CH3)3SiOSi(CH3)3 plus [(CH3)2SiO]4 and the rearrangement of (CH3)3SiO[(CH3)2SiO]5Si(CH3)3 or (CH3)3SiO[(CH3)2SiO]8Si(CH3)3, using sulfuric acid‐treated Fuller's earth as catalyst. Cyclic and linear reaction products were analyzed by gas–liquid chromatography. A four‐step polymerization mechanism was proposed to account for the approach to equilibrium from either the forward or reverse direction. Reaction rate expressions for this mechanism were reduced to a finite set of nonlinear ordinary differential equations. These were solved by using a fourth‐order Runge‐Kutta numerical integration on a Burroughs B5500 computer. The calculated molecular weight distributions thus obtained were found to agree at all times with the distributions from polymerization and rearrangement experiments.
Determination of kinetic parameters for pyrolysis of cellulose and cellulose treated with ammonium phosphate by differential thermal analysis and thermal gravimetric analysis
Authors: Akita K. , Kase M. 
Published: April 2003

AbstractActivation energy E, pre‐exponential factor k0, and reaction order n for the pyrolysis of α‐cellulose and cellulose modified with dihydrogen ammonium phosphate were determined by means of TGA and DTA. The results obtained are E = 53.5 kcal./mole, k0 = 1018.8 min.−1, n = 1 for α‐cellulose and E = 32 kcal./mole, k0 = 1012 min.−1, n = 1 for modified cellulose. A new theory of DTA was also developed. This theory, in which it is concluded that the peak value of DTA curve coincides with the maximum rate of reaction, may be used not only for the present work but is generally applicable to DTA studies. Detailed procedures of experiment and theory are described.
Poly‐1,6‐Diselenahexamethylene, 1,2‐diselenane, and their effects on vinyl polymerizations
Authors: Brown J. R. , Gillman G. P. , George M. H. 
Published: April 2003

AbstractPoly‐1,6‐diselenahexamethylene has been prepared, and some of its properties and those of its depolymerization product, 1,2‐diselenane, have been studied. Depolymerization probably occurs by a free‐radical mechanism. The effects of these organoselenium compounds on the thermal polymerization of styrene, methyl methacrylate, vinyl acetate, and acrylonitrile at 60°C. in the presence and absence of 2,2′‐azobisisobutyronitrile and on the direct photopolymerization of these vinyl monomers at 25°C. has been examined. Various reaction mechanisms are suggested to explain the experimental results.
Kinetics of free‐radical polymerization of p‐vinylbenzyl methyl ether: Crosslinking by initiator free radicals
Authors: Symcox Robert O. , Cotman John D. 
Published: April 2003

AbstractKinetics of polymerization of p‐vinylbenzyl methyl ether at low conversion either in bulk or in benzene have been found to be quite similar to those of the unsubstituted monomer styrene. Rates of polymerization initiated by peroxides or α,α′‐azobisisobutyronitrile over the temperature range 50–70°C. have been found to be proportional to [Monomer][Initiator]1/2 with an activation energy difference Epropagation – 1/2 Etermination ≈ 6 kcal./mole. Azo initiation leads to essentially unbranched poly(vinyl‐benzyl methyl ether) even at very high conversions, whereas initiation of undiluted monomer by diacyl peroxides results in some crosslinking at high conversion. Use of biacetyl as a photoinitiator of polymerization over the temperature range 0–60°C. with either bulk monomer or monomer solutions in benzene has been found in each instance to yield crosslinked, insoluble polymers at low degrees of conversion. Benzene solutions of soluble polymer have been converted to high molecular weight branched polymers by free radicals generated by photolysis of biacetyl, and a substantial preference of methyl free radicals to abstract benzyl hydrogens of poly(p‐vinylbenzyl methyl ether) rather than add to solvent benzene has been observed.
Copolymerization of 4‐cyclopentene‐1,3‐dione with p‐chlorostyrene and vinylidene chloride
Authors: Winston Anthony , Li George T. C. 
Published: April 2003

AbstractThe copolymerization of 4‐cyclopentene‐1,3‐dione (M2) with p‐chlorostyrene and vinylidene chloride is reported. The copolymers were prepared in sealed tubes under nitrogen with azobisisobutyronitrile initiator. Infrared absorption bands at 1580 cm.−1 revealed the presence of a highly enolic β‐diketone and indicated that copolymerization had occurred. The copolymer compositions were determined from the chlorine analyses and the reactivity ratios were evaluated. The copolymerization with p‐chlorostyrene (M1) was highly alternating and provided the reactivity ratios r1 = 0.32 ± 0.06, r2 = 0.02 ± 0.01. Copolymerization with vinylidene chloride (M1) afforded the reactivity ratios r1 = 2.4 ± 0.6, r2 = 0.15 ± 0.05. The Q and e values for the dione (Q = 0.13, e = 1.37), as evaluated from the results of the vinylidene chloride case, agree closely with the previously reported results of copolymerization with methyl methacrylate and acrylonitrile and confirm the general low reactivity of 4‐cyclopentene‐1,3‐dione in nonalternating systems.
Poly(chloral‐1,3‐dioxolane diol)
Authors: Dietrich Heinz J. , Karabinos Joseph V. , Raes Maurice C. 
Published: April 2003

AbstractChloral and cyclic formals were copolymerized in the presence of acidic catalysts and controlled amounts of water to diols of varying compositions and molecular weights. Cyclic oligomers were formed irreversibly as by‐products from the monomers and were also obtained by depolymerization. Condensation of the diols with diisocyanates yielded linear polyurethanes of improved flame resistance.
Radiochemical determination of low unsaturations in polyisobutene. Stoichiometry of the reaction between chlorine and branched double bonds
Authors: McGuchan R. , McNeill I. C. 
Published: April 2003

AbstractIn a previous paper, the radiochemical determination of low unsaturation in polyisobutene was effected by reacting radiochlorine with the double bonds. The reaction is one of substitution rather than addition, and the derivation of true unsaturation values required an assumption to be made regarding the number of chlorine atoms (one or two) incorporated per double bond. In this paper the assumption is tested by examining the stoichiometry of the chlorination of suitable model compounds of known or measurable unsaturation under the experimental conditions used previously. It is found that reaction leads to a monochloro product rather than the dichloro product previously assumed. Conclusions regarding the chain termination process in isobutene polymerization are re‐examined in the light of this result.
Stress–strain behavior of swollen polymeric networks
Authors: Rijke A. M. , Taylor G. L. 
Published: April 2003

AbstractThe network parameters of swollen, solution‐crosslinked polymer filaments can be collected from deswelling measurements in solutions of nonpermeating polymer or, as shown in this paper, from the stress–strain relation when in equilibrium with the surrounding solvent. The degree of swelling, at which the partial molar free energy of elasticity equals zero, is found to vary with solvent power in agreement with earlier findings on other systems. Comparison with results of studies on rubber networks crosslinked in the absence of diluent show that previously observed discrepancies between theory and experiment can be attributed to the deficiency of the single term involving the one‐third power of the volume fraction of polymer in the swollen network to describe the contribution of the partial elastic free energy.
Studies on tacticity of polyacrylonitrile. II. High‐resolution nuclear magnetic resonance spectra of 2,4‐dicyanopentanes
Authors: Murano Masao , Yamadera Reizo 
Published: April 2003

AbstractThe NMR spectra of 2,4‐DCNP were measured in CCl4, NaCNS–D2O, DMSO‐d6, and other solutions. The spectra of the meso form show no significant change with the solvent, but the racemic form shows two kinds of spectra, one of which is observed in a solvent for PAN and the other in a nonsolvent. In the solution, the meso 2,4‐DCNP is considered to have two equivalent conformations, TG and G'T, which are the mirror images with each other. The racemic 2,4‐DCNP, however, might have predominantly either the TT or GG conformation in CCl4, pyridine, and benzene, while it has the two conformers with almost equal probability in NaCNS–D2O and DMSO‐d6. The results obtained from the calculation assuming appropriate constants are in fairly good agreements with the observed spectra of the 2,4‐DCNP isomers. The values of chemical shifts and coupling constants used in the calculation correspond to those of PAN which were obtained previously from the analysis of the NMR spectra.
A study of the molecular weights of tetrahydrofuran–propylene oxide copolymers by gel permeation chromatography and other methods
Authors: Blanchard L. P. , Baijal M. D. 
Published: April 2003

AbstractThe cationic copolymerization of tetrahydrofuran and propylene oxide was studied in a batch system. Boron fluoride ethyl ether and 1,2‐propanediol were used as catalyst—co—catalyst system. Number‐average molecular weights M̄n of various copolymers were determined by vapor‐pressure osmometry (VPO) and hydroxyl endgroup analysis (OH). The VPO and OH molecular weights differed considerably. To explain the differences, several copolymers were analyzed by gel permeation chromatography (GPC). The chromatograms obtained showed for each copolymer analyzed two peaks, one located in the high molecular weight region, the other in the low molecular weight region. An attempt is made to correlate the results and to show the usefulness of GPC in the characterization of THF—PO copolymers.
Polymerization of styrene with VOCl3–aluminum alkyls
Authors: Anand L. C. , Deshpande A. B. , Kapur S. L. 
Published: April 2003

AbstractThe polymerization of styrene with VOCl3 in combination with AlEt3 and with Al(i‐Bu)3 in n‐hexane at 40°C. has been investigated. The rate of polymerization was found to be second order with respect to monomer in both systems. With respect to catalyst the rate of polymerization was first order for VOCl3–AlEt3 and second order for VOCl3‐Al(i‐Bu)3 systems. The activation energies for VOCl3–AlEt3 and VOCl3–Al(i‐Bu)3 systems were 7.37 and 11.25 kcal./mole, respectively. The molecular weight of polystyrene in the AlEt3 system was considerably higher than that in the Al(i‐Bu)3 system. The valence of vanadium obtained by a potentiometric method showed that the catalyst sites in the AlEt3 system are different in nature from those in the Al(i‐Bu)3 system. The effect of diethylzinc as a chain‐transfer agent in the AlEt3 system was also studied.
Free‐radical polymerization of vinyl ferrocene
Authors: Baldwin Mart G. , Johnson Kenneth E. 
Published: April 2003

AbstractThe results of quantitative studies of the rates of free‐radical polymerization of vinyl ferrocene indicate that the latter has polymerization characteristics similar to those of styrene. The rates of homopolymerization of these two monomers in benzene at 70°C. were measured with the use of azobisisobutyronitrile as catalyst. The rate constants (k = Rp/[M][I]1/2) are kVF = (1.1 − 1.8) × 10−4, kSTY = 1.65 × 10−4. Small amounts of vinyl ferrocene and styrene have similar effects on the rates of polymerizations of methyl methacrylate and ethyl acrylate and on the molecular weights of the resulting polymer. Polystyrene and poly(vinyl ferrocene) with similar molecular weights are isolated from polymerizations carried out under identical conditions. The rates of copolymerization of vinyl ferrocene—methyl methacrylate, vinyl ferrocene—styrene, and styrene—methyl methacrylate were determined by following the disappearance of monomers by means of gas chromatographic analyses. The relative reactivity for vinyl ferrocene is slightly lower than that for styrene.
Influence of intrachain interactions on the kinetics of styrene polymerization and copolymerization
Authors: O'Driscoll K. F. , Wertz William , Husar Anna 
Published: April 2003

AbstractIn the free‐radical polymerization of styrene, it has been observed that the onset of an acceleration of the polymerization due to increased solution viscosity can be quantitatively measured as occurring at a critical point. The product of the degree of polymerization of the polymer in solution at the critical point times its volume fraction can be represented by a temperature‐dependent constant (P̄n, Vc, = K ). The value of the constant passes through a maximum between 60 and 90°C. The value of the constant is somewhat lower than that for the phenomenon called chain entanglement. It is postulated that the temperature‐dependent behavior of K is due to a previously reported solution phase transition which is believed to be caused by interaction between phenylgroups on the polystyrene chain. Observations on the ultraviolet absorbance of styrene copolymers and calculations on the absolute rate of copolymerization of styrene with methyl methacrylate are presented to support the postulated intrachain interactions.
Isomerization polymerization of 2‐vinyl‐1,3‐dioxolane by α,α′‐azobisisobutyronitrile or by γ‐ray irradiation
Authors: Kagiya Tsutomu , Nakayama Takeo , Nakai Yoshio , Fukui Kenichi 
Published: April 2003

Abstract2‐Vinyl‐1,3‐dioxolane was polymerized by use of α,α′‐azobisisobutyronitrile (AIBN) or by γ‐ray irradiation. The polymer obtained was white amorphous powder which melted at ca. 70°C. and was soluble in chloroform, acetone, and p‐dioxane. The infrared spectrum of the polymer indicated peaks at 1735 cm.−1 characteristic of the carbonyl group, and at 1200–1000 cm.−1 characteristic of the acetal group, while no absorption at 990 and 3100 cm.−1 due to the vinyl group was observed. The spectra of the polymers obtained by AIBN and by γ‐ray irradiation were essentially identical. The saponified product of the polymer was white powder and its reduced viscosity was a little larger than that of the original polymer. These results indicate that the polymer has no ester unit in the main chain. The results of gas chromatographic analysis of the saponified product of the polymer, indicate the presence of a small amount of ethyl alcohol. The results of the saponification showed that the ester content in the polymer varied from 7 to 25% depending upon the polymerization temperature. These results indicate that 2‐vinyl‐1,3‐dioxolane polymerized by AIBN or by γ‐irradiation with two modes of vinyl and hydrogen migration, yielding a copolymer having the unit structures magnified image
Stereoregular condensation polymers. I. Synthesis and comparison of optically active and inactive polycamphorates and polycamphoramides
Authors: Toy Madeline S. 
Published: April 2003

AbstractOptically active and inactive polycamphorates and polycamphoramides were prepared by polycondensation of d‐ and dl‐camphoryl dichloride with 1,4‐butanediol, bisphenol A, and piperazine. The higher melting and more crystalline properties of optically active stereoregular condensation polymers compared to inactive atactic forms appear consistent with results from optically active isotactic and inactive atactic addition polymers.