bluuebunny/crossref_metadata_2025 huggingface dataset:
The effect of copolymers of 4(5)‐vinylimidazole and quaternary imidazolium salts on the hydrolysis rates of charged and neutral esters. I
Authors: Overberger C. G. , Pacansky T. J.
Published: June 2010

Cooperative and electrostatic effects were investigated for the hydrolysis of charged and neutral substrates catalyzed by a copolymer containing pendant nucleophiles (imidazole groups) and permanent positive charges (quaternary imidazolium halides). Limited evidence was also presented for apolar bonding in the hydrolysis of long chain anionic substrates catalyzed by a copolymer of 4 (5)‐vinylimidazole and 2, 3‐dimethyl‐1‐vinylimidazolium iodide (plm + C1+I−).
Polymerization of vinylpyridinium salts. VII. Formation of high molecular weight polyvinylpyridinium salts by spontaneous polymerization
Authors: Salamone J. C. , Ellis E. J. , Bardoliwalla D. F.
Published: June 2010

In this work are discussed the reactions of 2‐vinylpyridine and 2‐methyl‐5‐vinylpyridine with dilute and concentrated acid solutions. In reactions with dilute acid, the concept of pyridyl‐ethylation leading to initiation of polymerization was studied for both monomers. Although this reaction was applicable for 2‐vinylpyridinium salts, it apparently did not occur with 2‐methyl‐5‐vinylpyridinium salts. In reactions with concentrated acid, both monomers have been found to polymerize spontaneously to high molecular weight polymers. In addition, an analysis of the neutralized polymers by gel permeation chromatography (GPC) has shown them to be of narrow molecular weight distribution. An investigation of the effect of air or oxygen on these reactions has shown that they do not significantly alter the resulting molecular weights or molecular weight distributions that can be obtained. From a study of the percent conversion versus time, the data obtained indicated that these spontaneous polymerization reactions are chain‐growth processes.
Viscoelastic behavior of styrene/n‐butyl‐methacrylate/potassium methacrylate polymers
Authors: Erhardt Peter F. , O'Reilly James M. , Richards W. Conrad , Williams Meurig W.
Published: June 2010

This study concerns the ion containing terpolymers of styrene, n‐butylmethacrylate, and potassium methacrylate (S/n‐BMA/K+MA−) produced by the partial hydrolysis of random S/n‐BMA copolymers. The extent of hydrolysis resulted in terpolymers having 1 to 5 mol % potassium ions. The introduction of ionic sites produces labile crosslinks in these low‐molecular weight amorphous polymers which are reflected in many of the physical properties. The effects of temperature, shear rate, and shear stress on steady state and dynamic rheological properties are examined as functions of molecular parameters (ion content, S/n‐BMA composition, and molecular weight). The dependence of viscosity on composition and molecular weight are complicated by the occurrence of molecular entanglements at lower molecular weights as the proportion of n‐BMA is increased. It is found that the Newtonian viscosity, at constant T‐Tg, varies exponentially with the molar ion content. The rate of log viscosity increase with molar ion content varies as the inverse molecular weight of the S/n‐BMA copolymers in the region of molecular weights studied. At ion contents above about 4 mol % potassium ions, the system is rheologically complex. The viscosity exhibits different shear dependence in steady state and in oscillatory response, and the temperature dependence of the shift factor log aT changes abruptly. These have generally been taken to indicate some degree of ion clustering, although no direct evidence for the existence of clusters by low angle x‐ray studies has so far been observed in these materials.
Crystallization of poly‐(ethylene coacrylic acids) and poly(ethylene comethacrylic acids) and their salts
Authors: Macknight W. J. , Taggart W. P. , McKenna L.
Published: June 2010

A study of the crystallization behavior of poly(ethylene coacrylic acids) and poly‐(ethylene comethacrylic acids) and their lithium, sodium, calcium, and cesium salts has been made utilizing the techniques of X‐ray diffraction, differential scanning calorimetry, and infrared spectroscopy. The acid substituent content ranged from 2.1 to 6.3 mol %. The results indicate that the acid substituents do not incorporate into the polyethylene crystal lattice and that these substituents have large effects on the kinetics of crystallization, especially in the case of the salts. The results are interpreted on the basis of a three‐phase model consisting of a polyethylene crystal phase, a mixed amorphous phase, and a micro‐phase‐separated ionic cluster phase.
Modulus of tightly crosslinked polymers related to concentration and length of chains
Authors: Smith Thor L.
Published: June 2010

The equilibrium shear modulus G of network polymers increases rapidly with the chain concentration ν when ν ≳ 10−3 mol/cm3. This behavior is accounted for by the equation G=ΦnνRTΓ(1/λm) where Φn(=r̄t2/r̄00) may depend on n̄, the mean number of backbone bonds per chain, and Γ(1/λm) is a function of 1/λm, the mean fractional extension of chains in the isotropic (undeformed) network. In turn, 1/λm=(ΦnC̄n/q2n̄)1/2, where C̄n is a characteristic ratio (= r̄02/n/2) which, for short chains, depends on n̄, and q is a constant determined by bond angles and lengths. An expression for Γ, suggested by a well known equation for a regular cubic network of freely jointed volumeless chains, is derived and then shown to be approximated closely by Γapp=5λ/(5λ‐6) for 1/λm < 0.88. The moduli of some 26 ethyl acrylate‐dimethacrylate networks, for which 5 < n̄ < 23 and 2 × 107 < G < 5 × 109 dyn/cm2, were represented by the equation through use of effective parameters, Φef and Cef, which are independent of n̄. When C̄n is allowed to vary realistically with n̄, the equation also represents G. It then is found that Φn = 0.50 ± 0.05 when n̄ > 9.6, but that Φn increases twofold with decreasing n̄ when n̄ < 9.6. This variation is consistent with the assumption that the volume pervaded by the chains joined at a junction cannot be occupied by other chains.
Isothermal transitions of a thermosetting system
Authors: Gillham J. K. , Benci J. A. , Noshay A.
Published: June 2010

A study of the curing reactions of a cycloaliphatic epoxy resin/anhydride system by torsional braid analysis showed the existence of two critical isothermal temperatures. These are Tg∞ (the maximum glass transition temperature of the thermoset system) and Tgg (the glass transition temperature of the material at its gel point). Two rheologically active kinetic transitions occur during isothermal cure which correspond to gelation and vitrification. Three types of isothermal behavior occur: if Tcure > Tg∞, only gelation is observed; if Tg∞ > Tcure > Tgg, both gelation and vitrification are observed; if Tcure < Tgg, only vitrification is observed. Tgg corresponds to the isothermal cure temperature at which gelation and vitrification occur simultaneously. Methods for determining the time to gel and the time to vitrify, and also Tg∞ and Tgg, have been developed. The time to gel obeyed the Arrhenius relationship; the time to vitrify passed through a minimum. Application of these results to thermosetting systems in general is discussed in terms of the influence of molecular structure on the values of Tg∞ and Tgg.
Preparation of poly (4‐vinylpyridine borane) and its action as polymeric reducing reagent
Authors: Hallensleben Manfred L.
Published: June 2010

Linear and cross‐linked copolymers of 4‐vinylpyridine borane (4VP·BH3) with 4‐vinyl‐pyridine (4VP) and with styrene were prepared and used as polymeric reducing reagents towards various aldehydes and ketones. The monomer 4VP·BH3 could only be obtained in a mixture with 4VP, from which the IR data are submitted.
Synthesis properties and matrix binding of fe‐porphyrins containing isocyanate side‐chains
Authors: Kühn M. , Pommerening K. , Müller H. G. , Mohr P.
Published: June 2010

Fixation of the prosthetic groups of hemoproteids on synthetic macromolecular carriers is important from the viewpoint of biocatalytic investigations.

Fe‐porphyrins which contained isocyanate sidechains have been prepared by two methods. This isocyanate reacted in pyridine as the solvent at room temperature with cross‐linked poly(2‐hydroxyethylmethacrylate) and with Sephadex LH 20, a hydroxypropyl group containing a carrier.

The identity of the new Fe‐porphyrin derivatives and coupling products with synthetic carriers could be ascertained by elementary analysis and by absorption spectroscopy in the visible and infrared region.

The properties of mesohemin IX are retained after covalent binding to the carriers. At near neutral pH, a spectrum typical of alkaline hematin (parahematin) occurred. At pH 1.6, the spectrum of acidic hematin appears. The ligand binding ability to CN− and imidazole has been retained. The reduction of the Fe(III) with sodium dithionite is possible. The coupling products show peroxidatic activity.
Ion exchangers. XIX. Some properties of the carboxylic cation exchangers obtained by intermesh polymerization of methacrylic acid into styrene and divinylbenzene porous copolymers
Authors: Kolarz Bozena N.
Published: June 2010

Modification parameters of porous styrene and divinylbenzene (DVB) copolymers modified with methacrylic acid have been investigated using nonlinear optimization techniques. As the basic criterion of the investigation, the exchange capacity of carboxylic cation exchangers has been taken. The impregnation ratio of modifying mixture (1.4 cm3/g of the copolymer) was kept constant. Optimum parameters were found to be as follows: DVB concentration—1.5 % by weight (related to monomers); inert diluent (n‐heptane) concentration—13.3% by volume; temperature—95°C; time—90min, and benzoyl peroxide—2 g/100g of the modifying mixture.

Porous copolymers of styrene with the varying amount of DVB (x = 3–17.4%) were modified under these optimal conditions. A constant degree of modification of about 120% was obtained by keeping the constant independent of the swelling of the copolymer, by impregnation, and, thus a similar exchange capacity of the cation exchangers of about 6 meq/g of resin has been reached.

Some characteristic properties of six carboxlic cation exchangers as a function of the degree of cross‐linking in the starting porous copolymers were investigated: fractional attainment of equilibium of the exchange H+/Na+ and Na+/MB (methylene blue); exchange half‐time; internal diffusion coefficient; apparent equivalent volume; separation factor of the exchange Na+/Cu2+; porosity; and distribution pore volume.

The following suggestions on the mechanism of modification of porous copolymers can be proposed. The modified copolymers which have a high and medium degree of cross‐linking and little swelling have undergone a filling of pores, while a decrease in cross‐linking and an increase in the swelling ability results in two parallel tendencies. The first is filling of pores connected with a simultaneous penetration into the net. In this way, porous (double porous or hybrid) cation exchangers have been produced.
Determination of chemical inhomogeneity of transformation products of poly(vinyl chloride) by extraction of film from aluminium foil
Authors: Hace D. , Vurdelja V.
Published: June 2010

The chemical transformation of poly (vinyl chloride) with toluene in 1, 2‐dichloro‐ethane as solvent has been carried out in the presence of aluminium bromide. A series of copolymer products of certain degrees of transformation has been prepared. The chemical and molecular inhomogeneity has been qualitatively investigated.

The products have been fractionated by the Fuchs extraction method and refractionated by successive precipitation methods. The selective solvent systems have been predetermined. The benzene/methanol mixture is selective for the separation of aromatic fractions in copolymer products with low transformation degree. The fractions with noncyclisized aromatic units are separated with a methyl ethyl ketone/methanol mixture. Chloroform/methanol successfully selects aromatic fractions without vinyl chloride units in copolymer products of greater degree of transformation. The ratio of solvent/nonsolvent has been examined.

The following fractions have been isolated: the fraction of unreacted homopolymer PVC, the fraction with p‐methylstyrene units in chain, and the fraction of random copolymer with differences in the ratio of vinyl chloride, p‐methylstyrene, and 5‐methyl‐1, 3‐dimethyleneindan units. Characterization of the products and their fractions has been done on the basis of IR spectra, chlorine content, intrinsic viscosity, and x‐ray diffraction results. Analysis of IR spectra for PVC of low transformation degree in th region of C‐Cl stretching vibrations indicates the presence of changes. The inclusion of coloured crystalline complexes of C6H5CH3‐Al2Br6‐HCl intermediate from the reaction, which is incorporated into the copolymer, has been noticed.
Effect of the polymer matrix structure of reticular poly(vinylpyridines) on their electron‐donor properties
Authors: Saldadze K. M. , Kopzlova V. D. , Kargman V. A. , Gali‐Tskaya N. B.
Published: June 2010

The effect of the polymeric matrix structure on the acidic‐base, coordination, and kinetic properties of reticular poly (vinylpyridines) (RPVPs) obtained by copolymerization of 4‐vinylpyridine (AH‐40) and 2‐methyl‐5‐vinylpyridine (AH‐25) with divinyl aromatic compounds has been investigated by potentiometric as well as by IR and EPR spectroscopic methods.

The increase in the content of the crosslinking agent results in a lower pKa of RPVP and in reduced stability constants of their complexes with transient metal ions; therefore, the defectiveness of the coordination centers is increased.

The nature of the crosslinking agent determines the flexibility of the polymeric matrix and the availability of electron‐donor groups in them affects the structure of the average statistical coordination center, thus bringing about a change in the RPVP electron‐donor properties and in the stability constant of the polymeric complex.
Thermodynamic and hydrodynamic properties of polyelectrolytes
Authors: Nagasawa Mitsuru
Published: June 2010

An outline of thermodynamic and hydrodynamic properties of polyelectrolytes in solution is given. It is pointed out that proper models should be adopted to explain those properties. A polyion is often assumed to be a rigid rod having smeared charges on its surface for analyzing thermodynamic properties. The electrostatic potential distribution around rod‐like polyions, which may be calculated from the Poisson‐Boltzmann equation, can be tested by comparison with potentiometric titration data of poly(weak acids). Features of the counterion‐binding concept in analyzing thermodynamic properties are explained.

It is pointed out that the radius of gyration is important for analyzing hydrodynamic properties. Features of sedimentation, diffusion, and electrophoresis are explained and compared with each other. Discussion on the expansion factor of the polyion in the presence of added salt is also given in comparison with the theories published. Finally, a characteristic polymer concentration dependence of reduced viscosity, diffusion coefficient, and osmotic pressure coefficient of polyelectrolytes in pure aqueous solutions is explained.
Gel chromatography studies of gelatin
Authors: Coopes I. H.
Published: June 2010

Gel chromatography studies of a series of gelatins and dextrans on Sepharose 4B substrates are described. The intrinsic viscosities and weight average molecular weights of the gelatin samples are also measured. A plot of mean partition coefficients versus log (M>W[η]) is found to be linear for the dextrans, but not for the gelatins, in 0.1 M urea. In 0.1 M urea/0.1 M NaCl solution, the gelatins behaved more reproducibly.

The molecular weight distributions of the various gelatins, as delineated by the gel chromatography data, are considered in relation to manufacturing processes and physical properties.
Applications of thermal analysis to polymers
Authors: Loft B. C.
Published: June 2010

The term “thermal analysis” now refers to a set of techniques which measure the response of a specimen to a linearly varying temperature. They are versatile techniques with particular value for polymer science. The applications of the various thermoanalytical methods to the study of fusion, crystallization, glass transition, thermal degradation, oxidation, and crosslinking reactions and the use of the results in polymer science and technology are discussed.
Polymerization kinetics of N–vinyl pyrrolidone
Authors: Senogles E. , Thomas R.
Published: June 2010

Polymerization rates of N‐vinyl pyrrolidone and corresponding activation energies depend on the nature of the polymerization solvent. This is mainly due to the influence of solvent polarity on the propagation reaction. The dependence of the termination rate on the viscosity of the polymerization medium has a relatively minor effect.
Isothermal growth, thickening, and melting of poly(ethylene oxide) single crystals in the bulk
Authors: Kovacs A. J. , Gonthier A. , Straupe C.
Published: June 2010

Characteristic features of isothermal growth, thickening, and melting behavior of melt grown single crystals of low molecular weight poly (ethylene oxide) fractions are presented and discussed in terms of their relevance to basic concepts of polymer crystal growth. Measurements of growth (G) and thickening rates of once folded chain crystals were extended (up to the melting point) into a temperature range where usually only extended chain crystals grow. Monolayer extended and folded chain crystals melt by lateral shrinkage, the rate of which (G−) depends not only on temperature, but also on thermal history. G− increases exponentially with the degree of superheating, and the value of the temperature coefficient d log G−/dT is proportional to the lamellar thickness. In the narrow temperature interval where transition from once folded to extended chain growth occurs, the crystal morphology displays some spectacular features. These may be accounted for in terms of the crystal habit and the rate of completion, g. of a molecular layer in the particular (hk0) prism face considered. Morphological analysis shows that g is of the same order of magnitude as G(hkO), leading to the conclusion that the growth of these PEO crystals is controlled by multiple surface nucleation rather than by deposition of a single surface nucleus.
Viscoelastic behavior of polystyrene‐tricresyl phosphate solutions
Authors: Riande Evaristo , Markovitz Hershel , Plazek Donald J. , Raghupathi N.
Published: June 2010

The viscoelastic behavior of solutions of a narrow molecular weight distribution polystyrene in tri‐m‐toly 1 phosphate has been determined from the glassy to the terminal zones of response. The polymer concentration was varied from one to 100% thereby providing for the first time a complete picture of the influence of a solvent on the time‐dependent response of a polymer.

A computer analysis, governed by human judgment, has been used to extract retardation spectra which can be used to regenerate the reduced recoverable creep compliance curves within the scatter bands of the data. With the resulting retardation spectra, dynamic compliance and moduli curves have been calculated.
Multicomponent solutions of biological macro‐molecules: Thermodynamic and conformational studies of DNA
Authors: Eisenberg Henryk
Published: June 2010

In this contribution we show how theoretical concepts and experimental procedures developed in the study of macromolecular solutions can be applied towards obtaining information on polymers of biological interest. Thermodynamic and conform ational studies of DNA solutions will be reviewed. Equilibrium sedimentation and density measurements under well specified conditions contribute to our understanding of preferential and, sometimes, specific interactions. Equilibrium sedimentation in a density gradient unambiguously determines the molecular weight of large DNA particles. The flexibility of DNA molecules is well described by the persistent, or worm‐like chain. The Kratky‐Porod persistence length (derived from light scattering and transport measurements) provides a unique parameter invariant over the whole molecular weight range accessible to experimentation. Angular dependence of the scattering of light has now been extended to the study of quasi‐elastic scattering which provides additional information with respect to internal motion and flexibility on DNA molecules.
The cationic dimerization of 1,1‐diphenylethylene. I. Nature of active centers in the case of protonic and lewis acids initiation, at low temperature, in dichloromethane solution
Authors: Sauvet G. , Vairon J. P. , Sigwalt P.
Published: June 2010

The reaction of 1,1‐diphenylethylene with titanium tetrachloride or with trifluoromethane‐sulfonic acid has been studied at −30 and −70°C in dichloromethane solution, and has given, in both cases, relatively stable diphenyl alkyl carbocations. PMR spectra show that these cationic species are mainly monomeric, i.e., (I). In the electronic spectra, a main absorption band at 435 nm is assigned to both monomeric (I) and dimeric (II) cations, whereas, a 520 nm absorption is assigned to monomer solvated forms of I and II. A third absorption at 456 nm was detected by resolution of the overlapping absorptions at 435 and 520 nm and might be assigned to the dimeric cation, autostabilized through a ß‐phenyl ring interaction. Constants of the equilibria between the different species were determined at − 30°C.
Vinyl ketone‐sec‐allyl alcohol copolymers–open chain‐hemiacetal ring tautomerism
Authors: Merle‐Aubry Liliane , Merle Yves , Selegny Eric
Published: June 2010

Three poly(vinyl ketones) have been partially reduced to obtain different copolymers of vinyl ketones and secondary allyl alcohols. The first set of copolymers is obtained by partial reduction of poly(phenyl vinyl ketone). UV studies indicated that the Beer‐Lambert law cannot be applied to the different carbonyl bands. This is explained by a ring‐chain tautomerism between a carbonyl group and a neighboring hydroxyl group.

IR and 13C NMR spectroscopy confirmed these results and proved the existence of this tautomerism.

The second set of copolymers were obtained by partial reduction of poly(methyl vinyl ketone). UV showed the tautomsrism was strongly shifted toward the ring form; acetal condensation occurs in (tetrahydrofuran) THF‐methanol‐water mixture solution.

The third set of copolymers obtained by partial reduction of chiral poly [(S‐2‐methyl‐butyl)vinyl ketone] were studied by UV, ORD (optical rotary dispersion), and CD (circular dichroism); all three methods giving concordant results. The tautomerism was shifted more toward the chain form than for the reduced poly(methyl vinyl ketones) but less than for reduced poly(phenyl vinyl ketones).

The addition of strong acid to the polymer solution shifts the equilibrium toward the chain form; a similar shift is observed when the original polymer is in the solid state.
The formation and dissociation of networks formed by polymer‐plasticizer interactions
Authors: Makaruk L. , Retko I.
Published: June 2010

Systems containing polycarbonate and aromatic plasticizers with nitro groups were investigated. It was found, experimentally, that in these systems the tensile strength and tensile modulus increased. These changes of mechanical properties termed as antiplasticization can be interpreted as a result of crosslinking by the van der Waals bonds between the macromolecules and molecules of plasticizer. Considerations concerning the equilibrium of formation and dissociatiation of these networks were made in order to explain the phenomenon of threshold concentration of the plasticizer, below which antiplasticization and above which plasticization occur, as well as the nonlinear dependence of the glass transition temperature on the plasticizer concentration.
Interaction of maleic acid derivatives with gelatin
Authors: Kovács G. , Hardy G. , Szimàn O. , Szücs M.
Published: June 2010

This work deals with the crosslinking efficiency of different maleic acid derivatives (glycol dimaleate, glycerol trimaleate, pentaerithritol tetramaleate, mannitol hexamaleate) and copolymer of vinyl maleate for a better understanding of the mechanism of crosslinking. The reactions were carried out in an aqueous gel state of the biopolymer at 50°C. The kinetics of network formation was followed by measuring the melting point of the gel in contact with water. Such factors, as the decrease of hydrogen ion concentration or the increase of water content of the gel, were found to accelerate the rate of crosslinking. Amines, which were able to block the active sites in a competitive reaction, retarded the process. Synthetic polymers were used to delimit the possibilities of the interactions which might be responsible for the crosslinking. It was assumed that primarily the free amino groups of gelatin are involved in the crosslinking reaction by forming H‐bonds with the maleates.
Inhomogeneities in epoxy resin networks
Authors: Kreibich Ursula T. , Schmid Rolf
Published: June 2010

Inhomogeneities in the crosslink density of polymer networks have been proven, e.g., by electron microscopic studies, thermomechanical measurements, swelling experiments, light scattering and mechanical investigations. Using the differential scanning calorimetry (DSC)‐method, a new effect arising from inhomogeneities could be found by annealing studies of amorphous polymers carried out well below Tg. At those temperatures, the annealing of common epoxy resin systems causes a phase separation of the higher and lower cross‐linked regions. The results are a splitting of the glass transition into one part occurring at the initial transition temperature, while another part shifts towards significantly lower temperatures. This phenomenon may be used to obtain some information about the extent of the regions of different crosslinking density which, consequently, influence the physical properties of the material. The effect is obviously not restricted to crosslinked polymers, since it could also be confirmed for thermoplastic resins like poly(methyl methacrylate) or polystyrene. With increasing annealing temperatures, the morphology of the polymer is gradually changed to a state where a pronounced short‐range orientation, depending on the chemical structure of the segments, takes place. This state produces an endothermic peak in the DSC diagram superimposed on the glass transition.
Mechanical behavior of partially hydrolyzed preswollen polyacrylonitrile networks
Authors: Janáček J. , Stoy A. , Stoy V.
Published: June 2010

The basic mechanical deformation and ultimate characteristics were measured for three‐dimensional polyacrylonitrile networks swollen in water to equilibrium prepared in the presence of three different concentrations of diluent during polymerization (aqueous solution of ZnCl2, volume fraction of polymer v0 = 0.474, 0.578, 0.666), and hydrolyzed to various degrees. At the same time, the time dependence of the tensile modulus Ep(t) was measured at various temperatures within the range 25–85°C, and the temperature dependence of the modulus Ep(t)(t = 300 sec) within the range 25–80°C was measured. The results of mechanical characteristics were empirically correlated with the time of hydrolysis, the modulus Ep(t) (t = 300 sec; T = 25°C) and the content of the nitrile groups. It was demonstrated that the pseudoequilibrium modulus which is the measure of the degree of crosslinking and depends on the chemical composition of hydrolyzed polymer samples, is closely connected with their ultimate characteristics.
Kinetic and thermodynamic factors in polymer chemistry
Authors: Hawthorne D. G. , Solomon D. H.
Published: June 2010

Many polymer structures cannot be established unambiguously by the traditional methods used by organic chemists, and often it is necessary to postulate the likely manner in which the molecules are distributed and/or the detailed chemical structure of the repeat units. In many cases, polymer scientists have predicted structures based on thermodynamic factors. This approach has been fairly successful in the past, but it is now apparent that unqualified application of considerations based on thermodynamic stability can be misleading in certain cases. Specific examples of this are discussed with reference to the placement of monomers in vinyl polymerization and to the repeat units in cyclopolymerization; other examples are mentioned briefly.
Singlet energy migration down conjugated polymer chains
Authors: North A. M. , Ross D. A.
Published: June 2010

This paper discusses the migration of singlet energy along polymer chains. This is a process of technical importance in that it can affect the efficiency with which the energy from an absorbed photon is transferred to some acceptor molecule which may then function as a photostabilizer or photosensitizer.

When the side groups or unit chromophores on a chain are connected by strong electronic interactions (as in conjugated systems), the energy migration is extremely efficient, and it is probable that the energy is delocalized as a coherent exciton. The observed migration characteristics in poly(phenyl acetylene) and poly(p‐methoxyphenyl acetylene) are explained in terms of delocalization in a distribution of conjugated sequence lengths. In fluid solutions, segmental rotation maintains the distribution in dynamic flux, providing an “intersystem” ladder for the energy to be converted to long wavelength excitons, so that the effective migration distance is large and most of the fluorescence is long wavelength. In solids the distribution is static, effective migration distances are smaller, and the fluorescence contains an appreciable emission at shorter wavelengths from short sequences.
Photosensitized and γ‐ray‐induced graft copolymerizations of monomers to cellulose
Authors: Davis Neil P. , Garnett John L. , Urquhart Rodney G.
Published: June 2010

The variables affecting the photosensitized copolymerization of monomers to cellulose using the simultaneous technique have been systematically investigated. Such variables include type of sensitizer, structure of monomer, and type of solvent. LOW molecular weight alcohols are particularly effective as grafting solvents, especially for styrene and methyl methacrylate. Polyfunctional acrylates predominantly homopolymerize rather than graft, as do acrylonitrile and acrylic acid. Vinyl acetate and 4‐vinylpyridine graft with little competing homopolymerization, although only the latter monomer gives reasonable yields at short conversion times. A Trommsdorff effect is observed for the styrene‐alcohol system. Novel copolymerization behavior is found when mixed alcohols are used as solvents for styrene grafting. Data from the photosensitized grafting are compared with corresponding studies using initiation by ionizing radiation. Results in both ultraviolet and ionizing radiation systems are interpreted in terms of common intermediates involving charge‐transfer bonded species.
Trityl salt‐initiated polymerization of styrene
Authors: Johnson A. F. , Pearce D. A.
Published: June 2010

Styrene reacts with catalytic quantities (10−3 to 10−6 mole/1.) of trityl hexachloroantimonate (Ph3CSbCl6) in methylene chloride at ambient temperature to produce trace quantities of various styrene dimers and no polymer during the lifetime of the salt. Both linear and cyclic dimers have been found, some of which contained a trityl group; however, the major proportion consisted of isomeric forms of 1,3‐diphenylbutene‐1 and 1‐methyl‐3‐phenylindane. A kinetic study of the loss of Ph3CSbCl6 showed that the reaction is first‐order with respect to both [monomer] and [salt], and an initiation rate constant of 2.7 mole−1 sec−1 is obtained. With Ph3CSbCl6 concentrations greater than 10−3 mole/1., polymerization occurs. In contrast, trityl hexafluoroantimonate (Ph3CSbP6) in the same solvent at concentrations of 10−3 to 10−6 mole/1. gives rise to rapid and complete polymerization of styrene before all the salt is consumed. An apparent kp of ∼ 5.0 × 102 1./mole · sec has been obtained, but a gel‐permeation chromatography (GPC) analysis of the polymers shows the polymerization to be more complex than is apparent from the kinetic data at 0°C.
Cationic polymerization of 2‐alkenylfurans. I. General features
Authors: Gandini Alessandro , Martinez Ricardo
Published: June 2010

This paper reviews the major features of the cationic polymerization of 2‐vinylfuran, 2‐isopropenylfuran, 2‐vinyl‐5‐methylfuran, and 2‐isopropenyl‐5‐methylfuran, in methylene chloride using trifluoroacetic acid as initiator. Only the latter monomer gives polymers of regular structure in the temperature range −78 to 30°C. The others exhibit important side reactions leading to alkylation of the furan ring at 5C (when this is not methylated) and to polyunsaturated chains (if the carbon in the α position to the ring is tertiary). The kinetics of the polymerizations are affected by these side reactions. A brief analysis is made of the initiation, propagation, and termination reactions, and of the nature of the active species.
Synthesis of elastomers by cationic polymerization with expansion in volume
Authors: Bailey William J. , Iwama Hideaki , Tsushima Rikio
Published: June 2010

A bifunctional bis spiro ortho ester, hydroquinone bis‐(1,4,6‐trioxaspiro[4.4]non‐2‐ylmethyl) ether, was prepared in a 30% yield by treating hydroquinone diglycidyl ether with γ‐butyrolactone in the presence of boron trifluoride etherate. Copolymerization of a mixture consisting of 90% of 1,4,6‐trioxaspiro[4.4]‐nonane and 10% of the bis spiro ortho ester produced an elastomer with essentially no change in volume. Condensation of ethylene thiocarbonate with pentaerythritol in the presence of tributyltin oxide gave a 20% yield of a bis spiro ortho carbonate, 1,4,6,10,12,15,16,19‐octaoxatrispiro[4.2.2.4.2.2]nonadecane. Copolymerization of a mixture consisting of 90% of 1,5,7,11‐tetraoxaspiro[5.5]undecane and 10% of the bis spiro ortho carbonate gave an elastomer with a 3% increase in volume.
The initiation reaction in the molecular iodine‐induced polymerization of vinyl alkyl ethers
Authors: Johnson A. F. , Young R. N.
Published: June 2010

The first stage in the molecular iodine‐initiated polymerization of some vinyl alkyl ethers has been investigated at ambient temperature in several solvents. An equilibrium is established between monomer and iodine, prior to polymerization, which has the stoichiometry I2 + MX. The equilibrium constants in n‐hexane, cyclohexane, and chloroform have been investigated and the heat of formation of X determined. The results indicate that X is a diiodide and not a charge‐transfer complex. In solvents of higher dielectric constant, the equilibrium is perturbed by polymerization. Conventional spectrophotometry and stopped‐flow techniques have been employed to determine the rate of equilibration. In all of the solvents examined, a first‐order dependence on [monomer] and a second‐order dependence on [iodine] was observed. A mechanism is proposed.
Beitrag zur verfolgung des abbaues von polyäthylen während der verarbeitung
Authors: Zámorský Z.
Published: June 2010

The degradation of low‐density polyethylene under thermal stress in a quiet state and during processing from the melt was investigated. It was found that the limiting viscosity value decreases in both cases and the gel content increases, reaching a maximum in the range of 140–160°C. The molecular weight distribution broadens mostly toward the low fractions at the expense of the middle fractions. The main factors in the destruction are temperature and oxygen. The influence of frictions is not important.
Study of the thermal oxidation of polyole‐fins. V. Volatile products in the thermal oxidation of polyethylene
Authors: Barabás K. , Iring M. , Kelen T. , Tüdös F.
Published: June 2010

Organic volatiles formed in the thermooxidation of polyethylene at 150 and 160°C, 760 torr oxygen pressure were investigated by gas chromatographic analysis. Aldehydes and ketones having a linear chain were identified as the major components of the organic fragments investigated. Their concentration in the gas phase was found to decrease with increasing molecular weight; the main component was acetaldehyde which was present in an amount exceeding that of any other component by nearly one order of magnitude. A considerable amount of ethylene and low molecular weight alcohols was also found in the degradation atmosphere.

The evolution kinetics of the volatile products has been described by S type curves very similar to those of oxygen absorption with the period of maximum slopes coinciding with maximum hydroperoxide content in the polymer. Organic compounds are estimated to constitute only a small percent of the total amount of volatiles, in accordance with previous observations, recording that water is the dominant component.
Antioxidants and stabilizers. LX. Transformations of octadecyl 3‐(3,5‐di‐tert‐butyl‐4‐hydroxyphenyl) propionate and properties of products
Authors: Lerchová J. , Nikiforov C. A. , Pospíšil J.
Published: June 2010

The oxidation of octadecyl 3‐(3,5‐di‐tert‐butyl‐4‐hydroxyphenyl) propionate (I,R = C18H37) with tert‐butylperoxyl gives rise to a derivative of cyclohexadienone II. The mixture remaining after the isolation of the above compound contains colored compounds which are not quinonemethide III (R = C18H37); the latter was prepared by oxidation of I with Ag2O. The effect of I‐III on the oxidation of tetralin was determined at 65 and 120°C.
Antioxidants and stabilizers. LXIV. Effect of derivatives of cyclohexadienone and 1,4‐benzoquinone on the oxidation of atactic polypropylene at 120°C
Authors: Buben I. , Pospíšil J.
Published: June 2010

The effects of selected alkylperoxycyclohexadienones and derivatives of 1,4‐benzoquinone on the oxidation of atactic polypropylene, cetane, and tetralin at 120°C were compared. Considerable differences have been found in the ways of influencing the oxidation of the first two hydrocarbons which under certain given conditions absorb oxygen much more slowly than tetralin in previous investigations (Buben and Pospíšil, Collect. Czech. Chem. Commun., 40, 977, 987 (1975)).
Recrystallization of polymers during drawing
Authors: Čačković H. , Loboda‐Čačković J. , Hosemann R.
Published: June 2010

It is known that in branched polyethylene during cold‐drawing a solid state diffusion of the single chains takes place during which the branches are trapped in the amorphous phase and an equilibrium state of highest possible crystallinity is attained if ϵ ≦ 1.3%. This no longer can be achieved for larger e values and the sizes D̄002 of the microparacrystallites (mPC) in fiber direction attain a definite smallest value of 60 å. This is explained by a feedback of the lateral dimensions of the mPCs which on account of paracrystalline distortions, have sizes of 60‐100 å in a metastable state. The driving force of a minimum surface‐to‐volume ratio stabilizes therefore the D̄002 value and constraints the incorporation of more and more branches into the mPCs. Now the volume of the lattice cell increases monotonically with e > 0.013 and the melting point decreases according to Sanchez and Eby.
Study of orientation in amorphous polymers by the creep thermomechanical method
Authors: Forgács P. , Hedvig P.
Published: June 2010

Tensile creep of unplasticized and plasticized PVC and toughened polystyrene compounds were recorded as a function of the temperature with the UNIRELAX device developed in our laboratory and produced by Tetrahedron Associates, San Diego, California, U.S.A. The thermomechanical curves obtained this way were found to be governed by the creep process as well as by the recovery of the elastic deformation frozen‐in by processing. Using small stress levels (10 g/mm2) the thermomechanical curve was mainly determined by the recovery of the frozen‐in deformation. Effects of thermal history on the creep thermomechanical curves were studied and interpreted. Using a mathematical formalism derived earlier for amorphous polymers, the curves were computer‐processed in order to separate creep from the recovery of the frozen‐in deformation and to obtain isothermal kinetic curves.
Properties of polypropylene fibers made from polymer homologue mixtures
Authors: Geleji Frigyes , Kóczy László , Fülöp István , Bodor Géza
Published: June 2010

Fibers from mixtures of two polypropylene types were produced with the same conditions. The polymer base was a normal fiber grade polymer to which a high molecular weight polypropylene was added in amounts of 25, 50, and 75%. The extensibility of the fibers changed considerably by increasing the high polymer amount. The tensile properties were measured and compared with measured structural properties, such as crystallinity, crystalline particle size, amorphous orientation, amorphous region derived from small and wide‐angle X‐ray scattering. New terms, the specific amorphous orientation and the structural deformability index, were proposed, and it was shown that the tensile properties, i.e., strength, elongation at break, initial modulus and sonic modulus, are in very good correlation with them.
Method for the quantitative characterization of the supermolecular structure of highly oriented polymers
Authors: Jungnickel B. J.
Published: June 2010

The morphology of polymers having fiber texture is commonly considered to consist of a fibrillar structure. The author proposes a method for the quantitative description of the internal structure of the fibrils by analysis of X‐ray small‐angle scattering patterns. A theoretically relevant quantity, “morphology index” (μ) characterizing the fibril morphology can be calculated from structure parameters. Microfibrillar (μ » 1) and lamellar (μ « 1) structures represent limiting cases of the actual structural order. The dependence of μ on the temperature was determined for a series of fixed ends annealed polyamide‐6 filaments. A distinct change from the microfibrillar to the lamellar structure was verified, with slight increase of the microfibrillar character up to 140°C. With drawn polyamide‐6 samples the morphology index remains unchanged, in spite of slight changes of individual parameters, such as crystallite size, and weak shearing of fibrils. This suggests that drawing does not lead to essential changes of the internal structure of fibrils.
Isothermal growth, thickening, and melting of polyethylene oxide) single crystals in the bulk. II
Authors: Kovacs A. J. , Straupe C. , Gonthier A.
Published: June 2010

Characteristic features of isothermal growth, thickening, and melting of melt‐grown single crystals of poly(ethylene oxide) fractions, as reported in a recent paper, are complemented and further discussed. A newly discovered phenomenon–isothermal superheating–is described and its implications are discussed. Growth and thickening rate data are analyzed in terms of the two independent molecular parameters which determine the lamellar thickness: the number, n, of folds per molecule and the total chain length, λ Current formulations of kinetic theories are critically analyzed in view of their applicability to the present growth rate data. The analysis reveals that, for the low‐molecular‐weight fractions, the theory only applies to fast growth obtained at high undercooling. At low undercooling, where molecules deposit in extended or n‐times folded‐chain conformation, however, growth proceeds by a nucleation mechanism which appears to be quite different from that implied by the theory.
Determination of the conformation of polyelectrolytes in solution by small‐angle neutron elastic scattering
Authors: Moan Michel , Wolff Claude , Cotton Jean‐Pierre , Ober Raymond
Published: June 2010

This is a survey of recent experimental results obtained by small‐angle neutron scattering on the conformation of polyelectrolytes in the dilute and semidilute regime, in solutions both with and without salt. Some scaling laws are included.
Phase‐separation phenomena in solutions of poly(2,6‐dimethyl‐1,4‐phenylene oxide). III. Pulse‐induced critical scattering of solutions in toluene
Authors: Koenhen D. M. , Smolders C. A. , Gordon M.
Published: June 2010

For the polymer‐solvent system poly(phenylene oxide) in toluene the mechanism and kinetics of crystallization have been studied with the Pulse Induced Critical Scattering technique. It was found that after a delay‐time τ the growth mechanism was diffusion controlled. The delay‐time is thought to be connected with the nucleation of the crystallites and it disappeared in the “seeded” crystallizations studied. After incomplete melting of crystallites the first stages of growth resemble a condensation reaction.
The form‐anisotropy in light scattering: Experimental study of the validity of the rayleigh‐gans‐debye type approximation
Authors: Ravey Jean‐Claude
Published: June 2010

Some experimental evidence of the validity of the (extended) Rayleigh‐Gans‐Debye approximation when used to describe the anisotropic form of not very small particles (α < 5) is presented. This approximate theory affords results of reasonably good value for each case where exact analytical expressions occur for small particles (α < 1).
Fluorescence correction in light scattering measurements
Authors: Grebeňová B. , Hloušek M.
Published: June 2010

A. correction for the light scattering measurement of poly(2,6‐dimethylphenyleneoxide) due to partially polarized fluorescence is described.
Light scattering by large ellipsoidal particles. II. Determination of optical anisotropy by polarization ratio
Authors: Petres J. J. , Deželić Gj.
Published: June 2010

Polarization ratios of monodisperse ellipsoidal particles of barium sulfate were determined at wavelengths of 546 and 436 nm, and the optical anisotropy was determined. A significant increase of the optical anisotropy with the increasing axial ratio of particles was found. A part of the optical anisotropy can be ascribed to the anisotropic form, but the other portion is a consequence of the internal anisotropy of the barium sulfate particles.