bluuebunny/crossref_metadata_2025 huggingface dataset:
Benzheterocycle–imide and amide–imide fibers derived from diacid chlorides containing preformed imide groups
Authors: Preston J. , Dewinter W. , Black W. B.
Published: April 2003

Fibers of benzoxazole–imide ordered copolymers were prepared by cyclodehydrating the amide–phenol units of precursor polyamide–o‐hydroxyimide fibers at 375°C in nitrogen. The precursor polyamide–o‐hydroxyimides were obtained by the reaction of 3,3′‐dihydroxybenzidine with diacid chlorides containing preformed imide rings. The benzoxazole–imide fibers are very thermally stable, especially with respect to retention of tensile properties after heat aging in air. For example, the benzoxazole–imide fibers after heating aging in air for 35 days retained 75% or more of their original tenacities and 50% or more of their original elongations to break. The original fibers did not have high tenacities, probably because of the rather extreme thermal treatment required to cyclodehydrate the amide–phenol units of the precursor fiber. The ultraviolet light stability of one benzoxazole–imide fiber was outstanding for a fiber of the polyheterocycle type: there was no loss in strength or elongation after 140 hr of exposure in a Fade‐Ometer. Fibers of ordered amide–imide polymers based on the same imide‐containing diacid chlorides used for the benzoxazole–imide polymers were also prepared. They were substantially less thermally stable than their benzoxazole–imide fiber counterparts, as expected.
Applications of ESCA to polymer chemistry: Studies of some nitroso rubbers
Authors: Clark D. T. , Kilcast D. , Feast W. J. , Musgrave W. K. R.
Published: April 2003

Molecular core binding energies of the polymers formed by copolymerization of CF3NO with CF2CF2, CF2CFCl, and CF2CFH, respectively, have been studied by means of ESCA. The results are interpreted in terms of CNDO/2 SCF MO calculations on some model systems. Some evidence for structural irregularity is found for the copolymers with CF2CFCl and with CF2CFH. The reaction mechanism for the polymerization is also discussed in terms of the experimental results and INDO SCF MO calculations.
Photochemistry of poly(vinyl cinnamylideneacetate) and related compounds
Authors: Tanaka Hideaki , Tsuda Minoru , Nakanishi Hiroshi
Published: April 2003

The photochemistry of the cinnamylideneacetyl group was investigated with respect to a photosensitive polymer, poly(vinyl cinnamylideneacetate). The photochemical reaction of 1,4‐butanediol dicinnamylideneacetate was intramolecular cyclobutane formation. The photosensitive polymer underwent dimerization of the cinnamylideneacetyl moiety to form a cyclobutane ring. The reactivity of the double bond adjacent to the carbonyl group was larger than that of the double bond adjacent to the phenyl group in the chromophore. The quantum yield of the reaction was larger in the solid state than in solution: ϕ > 1.2 in crystalline state, ϕ = 0.5 in polymer film, ϕ = 0.1 in solution. The reaction was sensitized by triplet sensitizers (ET > 42 kcal/mole). The thermal reaction of the polymer was completely different from the photochemical reaction. A radical initiator was very ineffective for reaction of the polymer.
Perfluoroalkylene‐linked aromatic polyimides. I. Synthesis, structure, and some general physical characteristics
Authors: Critchley J. P. , Grattan Patsy A. , White Mary A. , Pippett J. S.
Published: April 2003

This paper describes the preparation of a series of novel perfluoroalkylene‐ and ether‐linked aromatic polyimides. Depending on the nature of the precursor diamine, the polyimides were prepared by either melt or solution techniques, the latter via the corresponding poly(amic acids). The polymers were characterized by a variety of methods, and their structure is discussed.
Study of (π‐C5H5)2Ti(CH3)Cl and (π‐C5H5)2Ti(C6H5)Cl in soluble Ziegler catalysts
Authors: Waters J. A. , Mortimer George A.
Published: April 2003

Soluble ethylene polymerization catalysts derived from (π‐C5H5)2Ti(R)Cl and R ′AlCl2, where R = methyl or phenyl and R ′ = methyl or ethyl, were studied both by polymerization kinetics at 0°C and by diagnostic experiments. It was found that the first insertion of ethylene into the TiR bond is difficult when R = methyl or phenyl, and for this reason these catalysts show a different overall behavior than when R = ethyl or higher alkyl.
Cyclization of synthetic cis‐1,4‐polyisoprene
Authors: Agnihotri Ram K. , Falcon D. , Fredericks E. C.
Published: April 2003

Cyclization of synthetic cis‐1,4‐polyisoprene was carried out by using TiCl4 and p‐toluenesulfonic acid catalyst. The average cyclicity and structure of the polymers cyclized to a different degree was studied by infrared and high‐temperature NMR spectroscopy. The methods of synthesizing an average mono‐, bi‐, tri‐, or polycyclic polymer that could be distinguished by high‐temperature NMR spectroscopy and followed by gel‐permeation chromatography are discussed.
Adsorption of gas on ion exchangers. III. The pore structure of m‐aminophenol–formaldehyde condensation resins
Authors: Hashida Isao , Nishimura Masato
Published: April 2003

m‐Aminophenol was condensed with formaldehyde in an acid medium in the presence of a water‐soluble inorganic salt (NaCl, CaCl2 etc) and/or poly(ethylene glycol). The pore structure characteristics of the condensation products were investigated by measurements of average pore size, pore size distribution of channels, total pore volume, surface area, and electron microscopic observation. The type and concentration of inorganic salts appeared to be a significant variable for the resulting pore structure, while poly(ethylene glycol) had a little effect. The nongel interstices of products were channels between many agglomerates of minute spherical gel particles with narrow pore size distribution. The diameters of these spherical gel particles were 3–10 × 10−1µ from the scanning electron microscopic observation. Apparent dissociation constants of functional groups of resin, pKa and pKb, estimated by using the Henderson‐Hasselbach equation, were 10.94 and 10.99, respectively. The resin had an ion‐exchange capacity of 1.0 meq/g for base and 4.8 meq/g for acid.
Polymerization of vinyl stearate multilayers
Authors: Cemel A. , Fort Tomlinson , Lando J. B.
Published: April 2003

A study was made of the solid‐state polymerization of built‐up monomolecular layers of vinyl stearate. Polymerization was initiated by exposing the samples to 60Co γ‐radiation. The reactions were followed by multiple internal reflection infrared spectroscopy. The structure of the multilayer monomer and polymer was studied by x‐ray diffraction. Surface properties of the multilayers were studied by contact‐angle measurements. Results showed that, under the proper conditions, monomer multilayers of vinyl stearate could be polymerized to virtually 100% completion. Reaction was favored by higher irradiation temperatures, larger doses of radiation, and by higher reaction temperatures. The x‐ray diffraction photographs indicated that both the monomer and polymer multilayers possessed some single crystal character. Contact‐angle measurements indicated that the molecules in both the monomer and polymer multilayers were closely packed.
Polymeric supports in peptide synthesis: An alternate preparation of crosslinked 4‐hydroxy‐3‐nitropolystyrene
Authors: Williams R. E.
Published: April 2003

An alternate preparation of the solid‐phase synthetic resin, crosslinked 4‐hydroxy‐3‐nitropolystyrene, is described. The reaction sequence, starting from a commercially available material, includes demethylation of crosslinked 4‐methoxypolystyrene by a mild procedure and nitration of the resulting 4‐hydroxypolystyrene. The final product is identical in all respects with that which has been previously prepared by a much longer route. A racemization test which involves tripeptide formation and separation of the diasteriomeric peptides produced by ion‐exchange chromatography indicates very large amounts of racemization may be associated with the use of the resin if care is not exercised in the choice of amino‐acid‐blocking groups.
Molecular weight distributions in radiation‐induced polymerization. VI. γ‐ray‐induced polymerization of “dry” styrene in the solid state
Authors: Westlake John F. , Huang Robert Y.
Published: April 2003

The γ‐ray‐initiated polymerization of styrene in the solid state has been studied over the temperature range −35°C to −55°C for samples exhaustively purified and dried to remove residual water (“dry” samples). Comparison with kinetic results previously reported for dry samples in the liquid state indicates a sharp decrease in the rate of polymerization resulting from the liquid to solid state transition. The molecular weight distributions for in‐source polymerization at −35°C and −40°C are bimodal in nature, and the appearance of a third peak is noticeable at −47°C and −55°C. In the case of postpolymerization at −35°C the molecular weight distribution is bimodal as in the case of in‐source samples. In the former case, however, the high molecular weight peak is predominant whereas the low molecular weight peak predominates in the latter. These results have been tentatively attributed to the postulated coexistence of two distinct propagating species which are radical and cationic in nature.
Dilute solution properties of sodium amylopectin xanthate
Authors: Manna P. K. , Choudhury P. K.
Published: April 2003

Sodium amylopectin xanthate, prepared by xanthation of potato amylopectin in alkaline medium, was fractionated and the fractions in 1M NaOH were characterized by viscometry and light scattering. The expansion factor α was determined from the expression due to Orofino and Flory. The value of a of the Mark‐Houwink relation, [η] = KMa, was also determined. Its weight‐average molecular weight, end‐to‐end distance, branching, and other parameters in alkali solution were also evaluated. From the data, it was concluded that the sodium amylopectin xanthate molecule had a polydisperse random‐coil chain configuration in 1M NaOH and had no tendency to aggregate in this medium.
Radiation‐induced polymerization of tetraoxane in the solid state. II. Molecular weight distribution
Authors: Nakase Yoshiaki , Yoshida Masaru , Ito Akihiko , Hayashi Koichiro
Published: April 2003

In order to investigate the mechanism of the radiation‐induced postpolymerization of tetraoxane in the solid state, the polymer was fractionated, and the fractions were characterized by reduced viscosity. The molecular weight of polymer formed in vacuo decreased drastically after the introduction of oxygen under conditions such that the polymer yield increased. The decrease in the molecular weight in the postpolymerization of tetraoxane is attributed to degradation of the polymer in the presence of oxygen. It is suggested that at least peroxides formed by preirradiation contribute to both the increase in polymer yield and the decrease in molecular weight of the polymer.
Kinetics of polymerization initiated by peroxides containing heterocyclic groups. I. Kinetics of bulk polymerization of styrene and vinyl acetate initiated by difuroyl peroxide
Authors: Molnar S.
Published: April 2003

The rate and degree of bulk polymerization of styrene and vinyl acetate initiated by difuroyl peroxide and, for comparison, by dilauroyl and dibenzoyl peroxides were measured at several temperatures as a function of the initiator concentration. Also the rates of initiation were determined by the inhibition method with Banfield's radicals. The rate of polymerization initiated by difuroyl peroxide appears to be lower than could be expected from the rate of initiation determined by the inhibition method and from the decomposition of difuroyl peroxide. In the case of polymerization of vinyl acetate there are significant deviations from the proportionality between Rp and the square root of the initiator concentration, which follows from the conventional kinetic scheme. The degrees of polymerization are also low, and the plots of Pn−1 versus Rp are not linear. These deviations can be accounted for by postulating a retardation effect of the furan cycle and chain transfer to difuroyl peroxide.
Asymmetric polymers. XXV. Synthesis of some optically active c‐substituted hexahydro‐2H‐azepin‐2‐ones
Authors: Overberger C. G. , Kozlowski John H. , Radlmann Edward
Published: April 2003

A series of optically active hexahydro‐2H‐azepin‐2‐ones substituted at the 5 position were prepared from (S)( − ) and (R)(+)‐hexahydro‐5‐carboxy‐2H‐azepin‐2‐one obtained via resolution of the racemic acid with brucine. Racemic hexahydro‐5‐carboxy‐2H‐azepin‐2‐one was synthesized from 4‐oxocyclohexanecarboxylic acid. Interest in many substituted hexahydro‐2H‐azepin‐2‐ones (ϵ‐caprolactams, 2‐oxohexamethyleneimines) stems in part from their ability to form polymers of the nylon 6 type whose properties may be systematically modified through regulation of the nature and position of the lactam substituent. Further structural control is possible through the use of optically pure monomers. An asymmetric seven‐membered lactam with a polar substituent might lead to a stereoregular polyamide where interaction between the side chain and the polymer backbone could influence the conformational properties of the polymer. A side chain such as the hydroxymethyl moiety would be expected to favor hydrogen bonding. This question is discussed in more detail in the paper which follows on the optical properties of the polymer.
Thermal degradation of a polyphenylquinoxaline in air and vacuum
Authors: Augl Joseph M.
Published: April 2003

A series of poly[2,2′‐(1,4‐phenylene)‐6,6′‐bis(3‐phenylquinoxalines)] were prepared. These polymers had all the same repeating unit but differed in molecular weight and polymer chain endings. The thermal degradation characteristics in air and vacuum were determined by isothermal weight loss measurements. The temperature coefficients of thermal degradation (apparent activation energies) were also determined. Whereas the apparent activation energies for degradation in air showed a considerable dependency on the type of polymer chain endings, no such effect was observed upon pyrolysis in vacuo. A possible chain‐end unzipping mechanism of degradation in air is postulated to explain these results.
Intramolecular cyclization of styrene–p‐divinylbenzene copolymers
Authors: Soper B. , Haward R. N. , White E. F. T.
Published: April 2003

Styrene has been copolymerized at low conversion with minor quantities of p‐divinyl‐benzene (p‐DVB) in (10–15%) solution in toluene and cyclohexane. Under these conditions the molecular weight of the polystyrene formed in the absence of p‐DVB was controlled by chain transfer, and the copolymerization coefficients of the styrene and the p‐DVB agreed with previous work. Polymer molecular weights were studied as a function of conversion. At very low conversions the number‐average (2.2 × 105) and the weight‐average (4.4 × 105) molecular weights were unaffected by substituting some of the styrene by p‐DVB, but as the reaction continued M̄n increased slowly and M̄w much faster. On the other hand, even at the lowest conversions the intrinsic viscosity was drastically reduced by the introduction of p‐DVB, and the radius of gyration, as measured by light scattering, fell. Infrared studies on the polymer show that the concentration of pendent double bonds in low‐conversion copolymers is about half of the doubly substituted phenyl groups. It is concluded that the first polymer chains formed are extensively cyclized with the formation of a relatively large number of small rings.
Synthesis of disulfide polymers of low molecular weight by repeated depolymerization
Authors: Tenc‐Popović Mirjana E. , Popov Svetlana , Radosavljević Slobodan D. , Rekalić Vladimir J.
Published: April 2003

By double or triple depolymerization with sodium hydrogen sulfide in the presence of sodium sulfite, polysulfide polymers of a very low molecular weight can be obtained from disulfide polymers prepared from bis‐2‐chloroethyl formal. The products are mixtures consisting chiefly of dimers and trimers with monomers. The effect of depolymerization will be greater when three depolymerization processes, instead of two, are completed with the same total amount of NaHS and Na2SO3. When depolymerization is repeated, the degree of depolymerization will be higher with polymers of a higher molecular weight. If depolymerization is made with sodium dithionite, the same effect will be achieved by either single or double depolymerization, provided that the same total amount of dithionite has been used.
Chromocene catalysts for ethylene polymerization: Scope of the polymerization
Authors: Karol Frederick J. , Karapinka George L. , Wu Chisung , Dow Alan W. , Johnson Robert N. , Carrick Wayne L.
Published: April 2003

Chromocene deposited on silica supports of high surface area forms a highly active catalyst for polymerization of ethylene. Polymerization is believed to occur by a coordinated anionic mechanism previously outlined. The catalyst formation step liberates cyclopentadiene and leads to a new divalent chromium species containing a cyclopentadienyl ligand. The catalyst has a very high chain‐transfer response to hydrogen which permits facile preparation of a full range of molecular weights. Catalyst activity increases with an increase in silica dehydration temperature, chromium content on silica, and ethylene reaction pressure. The temperature‐activity profile is characterized by a maximum near 60°C, presumably caused by a deactivation mechanism involving silica hydroxyl groups. A value of 72 was estimated for the ethylene–propylene reactivity ratio (r1). Linear, highly saturated polymers are normally prepared below 100°C. By contrast with other commercial polyethylenes, the chromocene catalyst produces polyethylenes of relatively narrow molecular weight distribution. Above 100°C, unsaturated, branched polymers or oligomers are formed by a simultaneous polymerization–isomerization process.
Comparison of number–average molecular weights calculated by GPC and membrane osmometry
Authors: Ambler M. R. , Mate R. D.
Published: April 2003

Data are presented which show that when a polymer contains an appreciable amount of low molecular weight species below the diffusion limit of the osmometer membrane, the osmotic molecular weight, M̄n, is generally higher than the M̄n calculated from gel‐permeation chromatography (GPC). Experiments were performed on samples of poly(vinyl chloride) (PVC) and high‐cis polybutadiene polymers. Osmotic data were obtained in the usual manner, while GPC data were obtained using the universal calibration approach. It was found that when all polymer species below approximately 10,000 molecular weight were excluded from the calculation of M̄n by GPC, agreement in M̄n was obtained between membrane osmometry and GPC. The data obtained suggest that the choice of M̄n as measured by membrane osmometry in the calibration of the GPC should not be done casually, as the measured M̄n may not reflect the “true” value of that sample, especially when the polymer sample contains an appreciable amount of low molecular weight material.
Solid‐state polymerization of hexamethylcyclotrisiloxane. II
Authors: Chawla A. S. , St. Pierre L. E.
Published: April 2003

The solid‐state polymerization of hexamethylcyclotrisiloxane has been shown, by means of specific ion scavengers, to proceed by a cationic process. The reaction occurs at the crystal surface rather than within the lattice and exhibits a polymerization rate which is inversely proportional to the defect and negative ion concentrations in the crystalline monomer.
Polymerization of pyromellitic dianhydride with 3,3′‐diaminobenzidine in aprotic solvents II. Dilute solution studies
Authors: Johnston Norman J. , Epps Lionel B.
Published: April 2003

Solution properties were determined for the poly(amide acid amine) obtained from the room‐temperature polymerization of pyromellitic dianhydride with 3,3,‐diaminobenzidine in aprotic solvents. Membrane osmometry data, viscosity studies, solution aging studies, and pH–viscosity relationships were given. Anomalous upswings in viscosity–concentration plots were attributed to absorption or capillary wall effects and not to polyelectrolyte effects, such as were induced by addition of strong bases. Similar absorption effects were found with polyamic acid solutions, in contrast to earlier reports that these polyimide precursors were polyelectrolytes. Unfavorable storage characteristics of the polymer solutions were explained by aging studies which showed that at 25°C dilute solutions exhibited a rapid drop in viscosity; in concentrated solution a slow increase to gelation was observed.
Stereoelective polymerization of racemic α‐olefins: Influence of conversion and of nature of catalyst components
Authors: Carlini Carlo , Bano Hussan , Chiellini Emo
Published: April 2003

The dependence of stereoelectivity on conversion has been investigated by polymerizing racemic 4‐methyl‐1‐hexene (I) and 3,7‐dimethyl‐1‐octene (II) in the presence of catalysts prepared from TiCl4 and bis[(S)‐2‐methylbutyl]‐zinc(III) or tris [(S)‐2‐methylbutyl]aluminum (IV). The influence of the nature of transition metal halide has also been examined by polymerization of racemic I and II with catalysts obtained from III and transition metal halides as well as from TiCl4 and optically active organometallic compounds containing phenyl groups. Stereoelectivity remains practically constant or increases slightly with increasing conversion, but it is affected by the nature of transition metal halide. Moreover a detectable variation of stereoelectivity was observed by changing the chemical structure of the alkyl group in the optically active organometallic component of the catalyst. In any case, however, stereoelectivity is not higher than 5–10%. Evidence in favor of asymmetric induction by the catalytic complex is reported and discussed.
Domain structure and bulk properties of solvent‐cast films of A–B–A block copolymers of styrene‐isoprene‐styrene
Authors: Uchida Takanori , Soen Toshiichi , Inoue Takashi , Kawai Hiromichi
Published: April 2003

Domain structures of solvent‐cast films of A–B–A block copolymers of styrene‐isoprene‐styrene were studied by electron microscopy by use of the OsO4 fixation technique. The effects of varying proportions of the two components and the casting solvent upon the domain structures were examined. It is concluded that the domain formation mechanism can be discussed like that of A–B block copolymers irrespective of sequence arrangements, as Matsuo et al. suggested, by treating A–B–A or B–A–B block copolymers as A–(1/2)B or B–(1/2)A block copolymers. The five types of fundamental domain structures—spherical domains of component A in a matrix of component B, rodlike domains of A in a matrix of B, alternating lamellae of the two components, rodlike domains of B in a matrix of A, and spherical domains of B in a matrix of A—are achieved mainly by the change of the fractional composition of the two components for a given solvent. One of the most significant features of the A–B–A block copolymers in contrast to the A–B block copolymers, i.e., that A–B–A chains can interconnect two A domains, was explored by investigating (1) the swelling behavior in a solvent that is a good one for isoprene but a nonsolvent for styrene and (2) mechanical behavior above the glass transition temperature of the styrene segments.
Comparison of optical and mechanical limits of linear relaxation behavior in glassy polycarbonate
Authors: Yannas I. V. , Doyle M. J.
Published: April 2003

The decay in birefringence of glassy polycarbonate held at constant extension has been studied at 23°C, in the time‐scale range 10–103 sec, up to about 6% strain. The results show that, under these conditions, the birefringence can be validly expressed as a linear hereditary integral of the strain history up to a relatively high strain level which is about 3.4% for an experimental time‐scale of 100 sec. Comparison with previously obtained data on the stress relaxation behavior of the same polymer shows that, other factors remaining constant, mechanical relaxation is linear only up to about 1.1% strain. The earlier onset of mechanical nonlinearity is discussed and it is suggested that the mechanical relaxation spectrum is richer than the optical spectrum in relatively long relaxation times, corresponding to relatively slow molecular motions. It is further suggested that these slow molecular motions are accelerated first as the polymer is extended beyond the limit of linear viscoelastic behavior. The observed nonidentity between strain limits for linear mechanical and linear optical behavior is discussed in the light of current practices in photomechanical stress analysis.
Evaluation of methods for determining the refraction correction for light‐scattering photometers
Authors: Wallace T. P. , Volosin M. T. , Delumyea R. G. , Gingello A. D.
Published: April 2003

Recent literature reports from three laboratories have treated the refraction correction for the Sofica and a noncommercial light scattering photometer. Our re‐evaluation of the data contained in these reports, as well as our experiments, indicate that the usually cited n2 refraction correction has not been unquestionably established for these instruments. In some cases, imprecise experimental techniques have been used to support this particular form of the correction. In addition, we find the optical system of the Sofica instrument results in the detector seeing vertically past the horizontal edge of the illuminated volume in violation of a basic assumption in the deduction of the n2 correction. Our experiments, as well as our interpretation of recent literature data, support an exponent of less than 2.0 for the Sofica apparatus, which is consistent with an instrument whose detector views outside the illuminated volume. However, the experimental methods available to evaluate the exponent lack the desired precision.
Crystallization of short aliphatic chains. II. Example of even fold surface with adjacent fold reentry and of a transition to chain extension
Authors: D'ilario L. , Keller A. , Martuscelli E.
Published: April 2003

As a continuation of the preceding study on the folding behavior of short polymer chains, an iodine‐terminated paraffin having 156 Å peak molecular length and a sharp molecular weight distribution was prepared. The paraffin could be crystallized in lamellae of two different thicknesses: (A) thickness close to half the chain length (the most readily obtained); (B) thickness intermediate between half chain length and fully extended chain. Case A corresponds to each chain folding once with equal stems and with ends at the surface. Degradation behavior revealed that the folds must be of closely equal length giving rise to an even fold surface. In case B the situation is more involved: here the chain ends must turn into the lattice. Adjacent reentry is a necessity throughout. In both cases the lamellar thickness could be increased by annealing up to complete chain extension.
Non‐gaussian elasticity of composite and interpenetrating networks
Authors: Smith Jr. K. J. , Gaylord R. J.
Published: April 2003

The elastic behavior of composite and interpenetrating network structures composed of non‐Gaussian chains is investigated. The chain probability density given by Nagai is employed utilizing only the leading correction terms for finite chain extensibility. The independent‐network hypothesis, proven valid in Gaussian statistics, is shown to be erroneous in non‐Gaussian systems. Further, it is found that composite networks composed of monodisperse chains are elastically isotropic, whereas a most probable contourlength distribution yields a large anisotropy but in the direction opposite to that observed experimentally for rubber. On the other hand, retention of the independent‐network hypothesis coupled with a most probable distribution successfully accounts for much of the observed anisotropy. Interpenetrating networks are shown to be substantially anisotropic when a most probable contour‐length distribution is employed.
Lactone polymers. IV. Glass transition temperatures of monomeric lactones and their polymers
Authors: Koleske J. V. , Lundberg R. D.
Published: April 2003

Glass transition temperatures were determined for a homologous series of unsubstituted lactone monomers varying in ring size from four to sixteen atoms. Examination of these transitions as a function of ring size shows a maximum in Tg for the seven‐atom ε‐caproalctone ring. This behavior is interpreted on the basis of a conformational change in lactones which occurs in rings containing seven to nine atoms. The Tg values of polylactones derived from these cyclic esters were determined and correlated with Tg values of the monomers. Except for the anomolous ε‐caprolactone and the strained fourmembered lactone, an apparently constant difference between monomer and polymer Tg is observed. Treatment of the polylactones as methylene copolymers permits extrapolations of the Tg values to obtain that of polyethylene. Two values suggesting the γ and β transitions of polyethylene are obtained.
Pressure‐dependent diffusion in velocity sedimentation
Authors: Weiss George H. , Yphantis David A.
Published: April 2003

We have calculated approximate profiles for the concentration gradient in velocity sedimentation of a homogeneous solute when both the diffusion and the sedimentation coefficient depend on pressure. Pressure dependence of the diffusion coefficient narrows the peak but does not seem to shift the maximum appreciably.
Viscoelastic properties of crosslinked solutions of poly(2‐hydroxymethyl methacrylate) in diethylene glycol. VI. Comparison with poly(butyl methacrylate) and poly(butyl acrylate) networks crosslinked to very low degrees
Authors: Janáček J. , Ferry John D.
Published: April 2003

On the basis of our own experimental and some literature data, the contributions of slow relaxation mechanisms to the shear modulus, (GeN — Ge), and the parameter C2 of the Mooney‐Rivlin equation have been examined for lightly crosslinked poly(butyl methacrylate), poly(butyl acrylate), poly(2‐hydroxyethyl methacrylate), and some rubber networks. For the rubbers, increasing degree of crosslinking caused a decrease in GeN — Ge and an increase in C2; for the other networks, both GeN — Ge and C2 diminished with increasing crosslinking. The effectiveness of the crosslinking polymerization, and also the absolute values of the physical crosslinking degree, decreased in the order of poly(2‐hydroxyethyl methacrylate), poly(butyl methacrylate), and poly(butyl acrylate). The values of the equilibrium compliances J of the networks studied, obtained by various methods, have also been compared, and good agreement has been found.
Dielectric behavior of aqueous solutions of sodium carboxymethyl cellulose
Authors: Allen D. J. , Neale S. M. , Tait P. J. T.
Published: April 2003

Measurements are reported for the dielectric loss factor of the SCMC solutions over the frequency range 2 MHz to 50 MHz as a function of concentration of SCMC, concentration of added sodium chloride, molecular weight, and temperature. The results are in general agreement with those of other workers and are interpreted in terms of ionic theories in which motion of the diffuse counterions is the dominant feature.
Kinetics of formation of polybisbenzimidazobenzophenanthroline‐dione (BBB polymer)
Authors: Ammons Vernon G. , Berry Guy C.
Published: April 2003

The kinetics of the polycondensation of 3,3′‐diaminobenzidine with 1,4,5,8‐naphthalenetetracarboxylic acid (NTC) have been investigated. Polymerizations were carried out in solution in either polyphosphoric acid (PPA) or in PPA mixed with some sulfuric acid. The reaction is heterogeneous in PPA owing to partial solubility of NTC, whereas it is homogeneous in the mixed solvent. The rate of disappearance of NTC and of dicarboxylic endgroups on oligomers was followed as a function of time at several reaction temperatures. The results show that NTC is more reactive than oligomers, so that the principle of equal reactivity is not valid for the initial steps in the polycondensation reaction.
Proton spin‐lattice relaxation study of polymer solutions
Authors: Sato Kazuo , Nishioka Atsuo
Published: April 2003

Proton spin‐lattice relaxation times of solvent molecules were measured on ternary mixtures of a polymer and two solvents by the adiabatic rapid‐passage method. The selective adsorption of a good solvent was verified by this experimental technique for the systems benzene—cyclohexane—polystyrene(PS), benzene—carbon tetrachloride—poly(methyl methacrylate)(PMMA), and chloroform—carbon tetrachloride—PMMA. The number of molecules of adsorbed benzene per monomeric unit of PS was estimated to be about four, which is almost identical with that determined previously by thermodynamic measurements. The number of molecules of benzene and chloroform adsorbed on PMMA were also determined to be about five and four, respectively. It was found that the interaction between chloroform and PMMA has the greatest effect on the molecular motion of the solvent, whereas the benzene—PS interaction is weak.
Thermal healing of scratches and determination of solid surface tension of selenium
Authors: Harris Lee B. , Vernon J. Peter
Published: April 2003

The healing of scratches on the surface of vitreous selenium was observed over a period of nine weeks, and from the data the solid surface tension of vitreous Se is estimated to be (100 ± 20) dyne/cm at 38.8°C, about the same as that of the liquid at the melting point. This value is three times as large as the critical surface tension determined from contact angle measurements, which indicates that for vitreous Se in contact with organic liquids, the solid—liquid interfacial tension is about two‐thirds as much as the solid surface tension. The present method of measurement can probably be used to determine the solid surface tension of other polymers, and by measuring the healing of scratches on a solid immersed in a liquid the method could be used to determine the solid—liquid interfacial tension.
Effects of melting on dielectric relaxation in poly(hexamethylene sebacamide) (nylon 610)
Authors: Boyd Richard H. , Porter Christopher H.
Published: April 2003

In order to investigate the role of solid morphology on molecular relaxation in crystaline polymers, the effect of melting on the α relaxation in poly(hexamethylene sebacamide) (nylon 610) was measured dielectrically. It was found that the α loss peak was continuous into the melt with respect to location in the frequency‐temperature domain and with respect to the shape of the peak. However, the strength of the process, as measured by the difference in the relaxed and unrelaxed dielectric constants, was discontinuous on melting, the process being much stronger in the melt. These observations are consistent with a two‐phase model of discrete crystalline and amorphous regions. The relaxation takes place in the amorphous regions, and melting creates more of this material but does not greatly after its nature. The correlation of the amount of amorphous material as measured by dielectric relaxation with that infrared from density measurements is discussed for nylon610, polyoxymethylene, and poly(ethylene oxide).
Extension and compression behavior of rubbery polymer networks
Authors: De Candia F. , Amelino L.
Published: April 2003

The elastic behavior of different types of rubbery polymers (natural rubber, polybutadiene, silicone, and polyisoprene) networks at various degrees of vulcanization and swelling was examined in extension and compression. The data are represented by the Mooney‐Rivlin equation. In compression, although C2 is zero, C1 decreases strongly with increasing swelling to a limiting value which, in some cases, may be correlated with the value of C1 found in extension and hence related to the theoretical modulus for highly swollen networks. A possible explanation is presented in terms of supramolecular order in the amorphous materials.
Membrane selectivity for an aqueous system by dynamic osmometry
Authors: Sheffer Howard , Sumner Paul
Published: April 2003

Commercial and fractionated samples of poly(ethylene glycol) and a sample of Dextran were used as standards to show the limitation of a cellulose acetate membrane for osmotic pressure determination of molecular weight in an aqueous system. The leakage of this membrane was much greater in the aqueous system than in organic solvents.
Quantitative structural characterization of the mechanical properties of poly(ethylene terephthalate)
Authors: Samuels Robert J.
Published: April 2003

The mechanical properties of poly(ethylene terephthalate) are examined to see if the quantitative morphological criteria previously used to define the structural state of isotactic polypropylene will lead to similar quantitative structure‐property correlations when applied to PET. Tenacity, thermal shrinkage in oil and air, tensile modulus, dynamic loss modulus, long spacings, and small‐angle x‐ray intensities are included in the study. All of the data were obtained from the open literature. In all cases the physical properties correlate simply and quantitatively with the internal structure of the PET, and the character of the correlations leads to new insights into the nature of the internal mechanisms controlling the observed properties. The study shows that only by considering the structural state of a polymer, and not its fabrication parameters, can general, simplifying, quantitative, structure‐property correlations be achieved.
Experimental investigation of the concept of molecular migration within sheared polystyrene
Authors: Whitlock L. Ronald , Porter Roger S.
Published: April 2003

Several important aspects of the flow in polymer melts through capillaries remain unexplored. This paper examines experimentally one such effect associated with the radial shear‐stress gradient in capillaries. During capillary melt flow of a polymer with a wide molecular weight distribution, migration of the large molecules away from the region of highest shear stress, i.e., at the capillary wall, has been predicted but only modestly investigated. This effect has the potential to produce a molecular weight spectrum over the cross section of extruded polymer. Studies of distribution in shear were conducted on a well‐characterized wide‐distribution polystyrene (M̄w = 234,000). An Instron Rheometer equipped with a long capillary (length/diameter ratio of 66.7) was used to perform the extrusion at temperatures of 160–250°C. A solvent coring procedure was used to dissolve away concentric layers of polymer from the extrudate for molecular weight analyses. The method has been shown to cut clean sections without selective extraction. Values of M̄w, M̄n and M̄w/M̄n were calculated from complete molecular weight distribution data obtained by calibrated gel permeation chromatography. For a wide range of shear rates and temperatures, no evidence for molecular fractionation was observed. Shear degradation of this polymer was found to be small. However, at high shear rates at 250°C, evidence indicating extensive shear‐induced thermal degradation was found. No evidence for oxidative degradation at the extrudate surface was found at either low or high shear rates at this temperature.
Mass and momentum transfer in polymers. I. Effects of equilibrium vapor sorption on tensile creep of an amorphous polymer
Authors: Machin D. , Rogers C. E.
Published: April 2003

Diffusion and tensile creep measurements were made for systems of poly(‐n‐butyl methacrylate) (PBMA) and sorbed ethanol, MEK, or benzene at 23°C. Rates of penetration of an inert spherical indenter into PBMA also were investigated and compared with the tensile creep behavior of the polymer. Creep measurements for various volume fractions of penetrant sorbed at equilibrium revealed that master curves, resulting from a time‐concentration superposition procedure, could be constructed for each penetrant. At long times, these master curves, particularly that for ethanol, show deviations from the corresponding time‐temperature superposition master curve. These deviations are interpreted in terms of probable long‐range entanglement coupling governed in part by the partially specific nature of polymer‐penetrant interactions. Parameters calculated by a free‐volume theory, describing both diffusion and tensile‐creep data, indicate that MEK is a more efficient plasticizing agent than the other penetrants and requires less local free volume for diffusion. Analysis in terms of the free volume concept was not attempted for the case of ethanol, where specific polymer‐penetrant interactions are more important.
Direct analysis of small‐angle equatorial x‐ray scattering from fibrous systems. II. Methods of extracting physical parameters describing the scattering system
Authors: Harget P. J. , Krimm S.
Published: April 2003

Small‐angle equatorial x‐ray scattering from fibrous systems is often complicated by the effects of morphological organization and/or heterogeneities as well as by macromolecular structure and organization influencing this same region of scattering space. In previous work it was shown that closed form mathematical expressions could be obtained for the Patterson function, without prior assumptions about the scattering system, when the intensity data were purposely truncated. In this paper the use of these expressions to extract the physical parameters describing the scattering system is demonstrated by application to a model system. The expressions are also expanded to include lattice distortions and long range coherency. A second approach is presented for cases when the coherence is small, and finally the use of higher‐resolution data is discussed.
Growth stages in epitaxial crystallization of poly(γ‐benzyl L‐glutamate)
Authors: Rybnikar F. , Geil P. H.
Published: April 2003

The electron microscope study of the isothermal epitaxial crystallization of PBLG on 001 cleavage surface of NaCl or KCl from 0.01% chloroform solution with various n‐octane contents has shown that the epitaxial growth process could be divided in two stages. In the first stage a rapid growth of a lamellar layer 20–40 Å thick could be observed; the PBLG molecules in αhelix conformation are oriented along <110> substrate directions. The dimensions and perfectness of alignment of these lamellae along the <110> direction depends on the molecular weight of the PBLG. In the second stage of PBLG epitaxial crystallization the relatively slow thickening of some initial lamellae takes place and one can observe many types of secondary structures. With increasing thickness of the epitaxial structures and increasing molecular weight of the PBLG the degree of orientation in relation to <110> substrate direction diminishes. The two growth stages in PBLG epitaxial crystallization are related to different kinds of orienting and attracting forces of the alkali halide substrate.
Elastic and thermoelastic behavior of cis‐polybutadiene crosslinked in the swollen state
Authors: De Candia F. , Amelino L. , Price C.
Published: April 2003

Samples of cis‐polybutadiene were cross‐linked in the presence of decalin at values of ϕr (the volume fraction of rubber) ranging from 0.25 to 0.50. After the diluent had been removed, a study was made of the force‐extension and thermoelastic behavior of the networks. Within experimental error, the ratio of the Mooney‐Rivlin constants 2C2/2C1 was found to be zero for networks prepared at low ϕr (0.25 and 0.30) but started to increase towards the conventional value at higher ϕr. The quantity fe/f was found to be independent of the ratio 2C2/2C1 and of the extension ratio α; the average value of fe/f was found to be 0.11.
Analysis of anisotropy in dielectric absorption due to defects in the polyoxymethylene crystal
Authors: Tanaka Akira , Ishida Yōichi
Published: April 2003

The dielectric absorption due to terminal polar groups localized in defect regions of polyoxymethylene crystals shows an anisotropy relative to an applied field. An attempt to interpret this anisotropy has been made by applying the barrier theory of Hoffman. The potential energy map for the rotation of the terminal polar group calculated from conformational analysis gives two minima. The angle between the dipole moment of the terminal OH and the fiber axis calculated in terms of the two conformations corresponding to the potential energy minima is in good agreement with results from infrared dichroism. This agreement is considered as evidence that the conformational analysis is reliable for estimating the potential energy minima required in the calculation according to the barrier theory. The barrier height obtained by the conformational analysis and the anisotropy calculated from the components of the dipole moments for the terminal polar group in terms of the barrier theory are in qualitative agreement with the experimental data.
Steady flow measurements on moderately concentrated solutions of poly(sodium acrylate)
Authors: Sakai Mototsugu , Noda Ichiro , Nagasawa Mitsuru
Published: April 2003

Shear stress P21 and normal stress P11 –P22 functions of moderately concentrated aqueous solutions of sodium poly (acrylate) were measured under steady shear flow at various shear rates \documentclass{article}\pagestyle{empty}\begin{document}$\dot \gamma$\end{document} with a Weissenberg rheogoniometer. The compliance function Js = (P11 – P22)/2P212 is found to vary with shear rate. The double logarithmic plot of Js versus
\documentclass{article}\pagestyle{empty}\begin{document}$\dot \gamma$\end{document} can be superposed with respect to molecular weight at constant concentrations of added neutral salt and polymer. These reduced plots differ markedly as the concentration of added salt is varied but converge to a single line at high shear rates.
Viscoelastic properties and flow of narrow distribution polybutadienes and polyisoprenes
Authors: Vinogradov G. V. , Ya. Malkin A. , Yanovskii Yu. G. , Borisenkova E. K. , Yarlykov B. V. , Berezhnaya G. V.
Published: April 2003

The dynamic shear modulus and the flow rate through capillaries under constant pressure and under constant velocity of the piston, have been measured for polybutadienes and polyisoprenes of narrow molecular weight distribution with molecular weights ranging, respectively, from 3.8 × 104 to 5.8 × 105 and from 1.06 × 105 to 6.02 × 105. The phenomena of the discontinuous increase of volume flow rate and self‐oscillatory flow regime at critical rates of deformation have been considered in detail. It is proposed that these phenomena are due to the induced transition of the polymer from the fluid to the high‐elastic state at higher deformation rates. As a result, an inference has been made that polybutadienes and polyisoprenes with a narrow molecular weight distribution in the high‐elastic state, behave in certain respects as crosslinked polymers incapable of displaying fluidity. The quantitative relationships among the viscoelastic characteristics measured under dynamic regimes, the parameters determining the critical flow regimes, and the molecular weights of polybutadienes and polyisoprenes have been worked out.