bluuebunny/crossref_metadata_2025 huggingface dataset:
Polymer morphology and mechanism of macrocrack propagation on fracture surfaces
Authors: Kireenko O. Ph. , Marichin V. A. , Miasnikova L. P. , Regel V. R.
Published: June 2010

Th0e relief of fracture surfaces of oriented monofilaments of nylon 66 has been studied with the help of both transmission and scanning electron microscopy. It has been shown that at different speeds of macrocrack propagation the relief of the so‐called mirror zone can show the original structural features of the material (e.g., the existence of supermolecular structures of the order of a micron, the influence of annealing, the distribution of micropores in the fibrillar amorphous regions) as well as effects connected with deformation processes at the tip of the crack, with discrete and auto‐oscillatory mechanisms of crack growth, the interaction of the macrocrack with the secondary fracture processes, etc.
Morphological investigations of ordered gel formation in polyelectrolytes
Authors: Purz H. J.
Published: June 2010

The diffusion of certain counter ions, such as T1, Ni, Cd or Zn ions, into the anionic polyelectrolyte Na‐cellulose xanthate results in ionotropic formation of ordered gels. These gels show birefringence, swelling anisotropy, ion exchange capability, and, under certain condition, capillary structure. The gel structure depends on the ion species. The factors affecting the capillary structure can advantageously be investigated with Zn‐and Tl‐cellulose xanthate gels. The gels formed under various geometrical arrangements have been investigated by optical, polarization and electron microscopy. The concept of the formation of ordered gels and capillaries is discussed. The gel properties (birefringence, coherent network structure, membrane and capillary structure) are maintained after splitting off the‐CSSH groups of the unstable metal cellulose xanthate gels. This offers the possibility of controlling the formation of supermolecular structure in cellulose by synthesis of ionotropic polyelectrolyte gels.
Structural changes of poly(vinyl chloride) particles
Authors: Ponížil František
Published: June 2010

Minute particles of emulsion paste‐forming poly(vinyl chloride) (PVC) sinter when dried in a nubilous dryer. In contact with a plasticizer they change their structure‐depending on the hardness of their surface they disintegrate into many small particles. Some substances, especially those belonging to a group of simple glycolethers, have been found to considerably accelerate the disintegration process. To study the process, chiefly microscopic observations were carried out completed with additional viscosity and refraction measurements.

In the microscope an unusual interaction of PVC particles with glycolether itself has been observed. In contrast to plasticizer action, irregular fragments are formed instead of small particles. Calorimetric measurements done during the interaction indicated that the interaction is a strongly exothernic process.

Based on the above mentioned measurements a mechanism is suggested for these disintegration processes which greatly affect viscosity of PVC pastes.
A partition function for chain molecules applicable to high and low densities
Authors: Bonner D. C. , Bellemans A. , Prausnitz J. M.
Published: June 2010

The quantitative calculation of vapor‐liquid equilibria in mixtures consisting in part of chain molecules requires a partition function valid at both low and high densities. A preliminary partition function for this purpose is described. It is based on the hole theory of liquids and incorporates the concepts of Prigogine and Hijmans for chain molecules. The new partition function is used to represent the vapor‐liquid coexistence curves of long‐chain n‐alkanes.
Generalization of the flory‐huggins treatment of polymer solutions
Authors: Kennedy J. W. , Gordon M. , Koningsveld R.
Published: June 2010

The Flory‐Huggins form of the free enthalpy (Gibbs free energy) of mixing expression for solutions of linear homopolymers, generalized to make the interaction parameter × a function of concentration (as well as temperature) has been extended further to cover in general copolymeric and branched systems. From the resulting expression it is still possible to obtain the chemical potential, spinodal, and consolute state relationships in closed form. One simple case to which this treatment can be applied is that of the linear homopolymer system in which the interaction parameter is regarded as a function of molecular weight.

A particular form for the molecular weight dependent interaction function is considered. After reducing the number of parameters by applying some thermodynamic restrictions, the remaining constants are evaluated with the aid of critical point data. The resultant interaction function is compared with other available experimental data. The process of reducing the number of floating parameters by means of restrictions of a thermodynamic nature is of general significance.
Quasichemical equilibrium approach to crosslinked polymer solutions
Authors: Dušek K.
Published: June 2010

Thermodynamic functions for mixing of a solvent with a crosslinked (branched) polymer are derived by considering the primary chains as copolymers of crosslinked and uncrosslinked units. Primary chains and solvent molecules are placed on a lattice with coordination number z. The crosslinked units bear one crosslinkable (C) and z‐3 (inner units) or z‐2 (end units) uncrosslinkable (U) contact surfaces. The free enthalpy of mixing is obtained by the quasichemical equilibrium approach and Tompa's modification for polymer molecules with different contact points. The condition of quantitative pairing (of purely entropic nature) of C contact surfaces is then introduced leaving only U contact surfaces available for the quasichemical equilibrium. In the polydisperse case, primary chains with a constant number of crosslinked and uncrosslinked units are taken as components. If mixing causes the dimensions of elastically active network chains (EANC) to be different from their reference (rest) dimensions, an elastic contribution proportional to the number of EANCs is added to the free enthalpy change. Comparing the result with the swelling equation of Flory relating the chemical potential of the solvent to the lattice site fraction of the polymer after swelling (θP) and at crosslinking (θP) and the fraction of EANCs per polymer unit (ve) ΔμS/RT = In (1 ‐ θP) + θP + XθP2 + ve (θP1/3θP02/3 ‐ αθP) (with α ± 1/2), it is shown that the interaction parameter × is a function of the coordination number, degree of crosslinking, molecular weight of primary chains (and concentration); the depedence vanishes if z goes to infinity. The coefficient α depends on the network structure and is equal to 1/2 only for an ideal network obtained by crosslinking of an infinite primary chain.
A refractometric and gel sorption study of the system poly(vinyl alcohol)‐water‐n‐propanol
Authors: Nagy M. , Wolfram E. , Györfi‐szemerei A.
Published: June 2010

It has been found that direct measurement of selective sorption of solvent mixture on the loosely crosslinked gels with low polymer concentration would yield some information on the preferential solvation and also on the nature of the interactions. Experimental data obtained by refractometry and sorption measurements carried out with the system poly(vinyl alcohol)‐water‐n‐propanol have shown the proposed way of approximation to be successful. Based on the experimental results a solvate model for this system was proposed in which the n‐propanol is bound to the polymer chain by both hydrogen and hydrophobic bonds.
Etudes spectroscopiques de transitions “helice‐pelote” de polypeptides en solution acide
Authors: Combelas Ph. , Garrigou‐Lagrange C.
Published: June 2010

Infrared spectra of various polypeptides (poly‐L‐alanine, or PLA; poly‐L‐methionine or PLM; poly (γ ‐ benzyl‐L‐glutamate), or PBLG) in CF3COOH‐CHCl3 solutions have been investigated in regions characteristic of the peptide group (amide A, I and II) and of the acid solvent (vOH, vC=O). These spectra have been analyzed by comparison with the infrared spectrum of a model amide (N‐methylacetamide). This analysis shows that by addition of acid the simple amide and the polypeptides exhibit at first a similar behavior by forming complexes by hydrogen bonding, i.e., >C=O…HOOCCF3. At higher acid concentrations, unlike the model amide, polypeptides are not protonated. Furthermore, the evolution of the spectra as a function of complexation clearly indicates the helix‐random coil transition of these polymers and agrees well with optical rotatory dispersion measurements. Thus, steep transitions have been obtained for PBLG and PLM in a small range of acid concentration or of temperature. To the contrary, no discontinuity in the evolution of PLA spectra has been seen. This observation compares well with the slow transformation observed by optical rotatory dispersion (ORD). Finally, it is possible to compare at the level of the repeat unit the strength of the acid perturbation which triggers the transformation of the three polypeptides. This points out the important part played by the sidechains as stabilization forces of the helix and the cooperative aspect of the transitions.
The thermodynamics of solutions of some normal and branched alkanes in polyisobutylene: an investigation by gas‐liquid chromatography
Authors: Hammers W. E. , de Ligny C. L.
Published: June 2010

Gas‐liquid chromatography is a separation method for volatile compounds which is widely used in analytical chemistry. It is based on the partition of the components of a sample between a moving gas phase and a stationary liquid phase of low volatility, the latter in the form of a thin coating on inert support particles filling a long, narrow column. Under proper conditions, values of the standard partial molar free enthalpy of vaporization from infinitely dilute solution in the stationary phase can be obtained from retention times, as a function of temperature. Combination with the standard molar free enthalpy of vaporization of the pure compounds yields the standard partial molar free enthalpy of mixing with the stationary phase. As a method for the investigation of the thermodynamics of interactions in polymer solutions, gas‐liquid chromatography is unique in the sense that it easily yields accurate data at a mole fraction of the polymer near unity and at high temperature. Here the method is applied to solutions of some normal and branched alkanes in polyisobutylene. The results are discussed in terms of a simplified version of the Prigogine solution theory, used by Patterson et al., and in terms of the solution theory of Flory, Orwoll, and Vrij.
On the adsorption of a polymer chain at a boundary
Authors: Bellemans A.
Published: June 2010

On the basis of a simple lattice model, the adsorption of a polymer chain on a surface is discussed, taking excluded volume effects (intrachain interactions) into account. Configurations of finite chains of n elements (self‐avoiding walks) are enumerated exactly for n ≤ 13 on the simple cubic lattice. Some predictions concerning the asymptotic behavior of long chains are derived from these data by using extrapolation methods previously devised by Domb and Sykes for bulk properties.
The reactivity of antioxidants with peroxy and alkoxy radicals in the presence of transition metals. I. Relation between the structure of free antioxidant radicals and inhibition of oxidation in polymers
Authors: Tkáč A. , Omelka L. , Holčík J.
Published: June 2010

The efficiency of homolytic splitting of the OH bond of different phenols, bisphenols, thiophenols, naphthols, and benzophenones and the transfer of the hydrogen atom to an alkoxy or alkyl‐peroxy radical is a function of the electro‐affinity of the substituent in the ortho position. The stability of the formed phenoxy radical is in relation to the delocalization of free electron in the para position, especially if the substituent has aromatic character. The inhibition effect of thermal oxidation is found to be the highest in that case where the substituent does not hinder the recombination of RO2 radicals with those of antioxidant.

According to the electron paramagnetic resonance spectra of the generated phenoxy radicals the differently substituted phenols can be divided into five main groups: 1) phenols which form primary stable free radicals; 2) phenols which form secondary stable free radicals, 3) phenols which give stable phenoxy radicals only after coordination into the ligand field of the transition metal; 4) phenols whose radicals undergo disproportionation; 5) phenols substituted with NO2 groups which do not form free radicals in nonpolar solvent.

Cobalt traces induce the decomposition of hydroperoxides generated in thermal initiation of polymer oxidation by quite a similar redox mechanism as the one observed in the fixation of RO2 radicals on transition metal. But the cobalt compounds are not active in polymers if those are free from oxidation products (hydroperoxy groups).
Oxidative stabilization of dimethyl silicone fluids with iron between 70 and 370°C
Authors: Nielsen J. M.
Published: June 2010

Long term oxidation tests below 150°C on dimethyl silicone (DMS) fluids with controlled iron content, in conjunction with previous work, have provided a broad concept of the processes of oxidation in DMS fluids between 70 and 370°C. A nonfree radical, iron‐catalyzed oxidation of DMS fluid occurs both below and above 150°C. A diverging, free radical chain reaction which is inhibited by iron is initiated by direct attack of oxygen on the methyl groups of DMS above 150°C. It is believed that a ferric iron complex is the key mechanistic species both in the catalyzed oxidation and in the free radical reaction inhibition.

When temperature, iron dispersion, and aeration are held constant, the oxidation rate of a DMS fluid below 150°C varies directly with its iron level. Above 150°C the oxidation rate is still dependent on iron level, but an ‘optimum iron level’ for a minimum oxidation rate exists for each temperature of oxidation. This optimum iron level increases with the temperature.

A conceptual diagram has been developed to unify and summarize these effects over the temperature range 70–370°C, providing a basis for the most effective use of iron to stabilize DMS fluids.
Antioxidants and stabilizers. XXXVII. A contribution to the elucidation of differences between the antioxidative activities of isomeric dihydric phenols
Authors: Lisá E. , Pospíšil J.
Published: June 2010

Differences in the antioxidative properties of isomeric dihydric phenols, observed in the stabilization of polypropylene, were thoroughly followed in initiated oxidations of tetralin, cumene, styrene, and 9,10‐dihydroanthracene. 2‐tert‐Butylhydroquinone and 4‐tert‐butylpyrocatechol were used as stabilizers. Values of the induction periods and of the stoichiometric factor, n, were used to rate the activities. In all cases, 2‐tert‐butylhydroquinone caused lower n values than 4‐tert‐butylpyrocatechol. The value n of the latter was not significantly influenced either by the temperature or by the concentration of the reaction components. Under similar conditions, the value n of 2‐tert‐butylhydroquinone was increased with increased rate of initiation. It is possible to state, on the basis of the obtained results, that a side initiation of chains is the cause of the low activity of 2‐tert‐butylhydroquinone in the inhibited oxidation of tetralin. Such a side initiation can be precipitated by an interaction between an aryloxy radical derived from 2‐tert‐butylhydroquinone and tetralyl hydroperoxide.
Antioxidants and stabilizers. XLIII. Structure of phenolic antioxidants and infrared spectra of the hydroxyl groups
Authors: Pivcová H. , Jiráčková L. , Pospíšil J.
Published: June 2010

Infrared spectra of 2,2′‐alkylidene, 2,2′‐thiobisphenols, and 2,2′‐biphenyldiols have been measured in the range of the OH stretching vibrations. From these measurements the possible conformers present in dilute CCl4 solutions are proposed. A correlation between the amount of the free and the intramolecularly bound hydroxyl groups in 2,2′‐bisphenols and their antioxidative activity is discussed.
Ionically crosslinked hydrophilic polymer membranes: Synthesis and measurement of transport properties
Authors: Huang Robert Y. M. , Jarvis Neil R.
Published: June 2010

Water soluble polymer and copolymer systems containing a poly(carboxylic acid) as one component have been ionically crosslinked in the form of membranes using multivalent metal salts. The permeability coefficients for a homologous series of poly(ethylene glycols) permeating through the ionically crosslinked membranes and a commercial cellophane membrane were determined using a continuous flow dialysis apparatus. Solute concentration changes occurring during dialysis were determined by using an in‐line continuous flow differential refractometer. For the ionically crosslinked membranes the permeability coefficients were found to decrease exponentially with increasing permeant molecular weight. For the cellophane membrane the permeability coefficients were observed to be inversely proportional to the square root of the permeant molecular weight. This square root correlation appears to be consistent with a porous flow model for transport through cellophane membranes.
Anionic polymerization of α‐pyrrolidone and α‐piperidone using their quaternary ammonium salts as catalysts
Authors: Sekiguchi Hikaru , Tsourkas Panayota Rapacoulia , Coutin Bernard
Published: June 2010

Quaternary ammonium salts of α‐pyrrolidone, α‐piperidone and ε‐caprolactam, prepared extra situ, were used as catalysts in anionic polymerization of these lactams. Pyrrolidone and piperidone salts gave the corresponding lactam polymers of increased molecular weight, with an improved yield, as compared to those obtained using classical alkaline catalysts (a true high polymer of piperidone with a reduced viscosity of 4.58 was obtained for the first time). The caprolactam polymerization succeeded only at comparatively low temperatures (∼ 100°C).

The high activity of these catalysts permitted us to prepare high polymers, using slow initiators or initiators of inferior activity. The influences of coexisting functional groups extraneous to the polymerization, namely water, are demonstrated.

The polymerization data indicate that the dimension of catalyst cation plays an important part in molecular growth in the heterogeneous reaction phase and provide some arguments in favor of our mechanism.
The kinetics of anionic polymerization of styrene in 1,2‐dimethoxiethane
Authors: Alvarino J. M. , Chmeliř M. , Schmitt B. J. , Schulz G. V.
Published: June 2010

Kinetic measurements in a flow apparatus in combination with conductance measurements, permit the determination of the two equilibrium constantsKesandKdiss* and the three propagation rate constantsk(±)c, k(±)sandk(−) as a function of temperature. The great differences in the polymerization rate in various solvents are mainly caused by their influence on the equilibrium constants. The influence of the solvent on the rate constants is not greater than in other chemical reactions.
Radical copolymerization of 2‐vinyl‐1,3‐dioxane with vinyl compounds and maleic anhydride
Authors: Acosta J. L. , Enriquez M. , Mateo J. L.
Published: June 2010

A exploratory study on the copolymerizability of 2‐vinyl‐1,3‐dioxane (VD) has been carried out.

VD was polymerized with styrene, vinyl acetate, methyl methacrylate, and acrylonitrile. Acrylonitrile was the only one which provided copolymerization products. For the acrylonitrile (M1)‐VD (M2) pair, r1 = 3.64 ± 0.1 and r2 = 0.057 ± 0.01 at 70°C. The transfer reactions of a series of 1, 3‐dioxane compounds in the styrene polymerization were investigated, with the result that the acetalic hydrogen is responsible for the transfer values found. VD was also copolymerized with maleic anhydride yielding alternating copolymers.
Kinetic studies on the preparation of polycarbonates in solution
Authors: Turska Eligia , Dems Andrzej , Bortnowska‐Barela Barbara
Published: June 2010

The results of previous works have shown that the coil expansion factor of the reacting macromolecules is a parameter directly affecting the values of the kinetic constants measured. Since this factor is also dependent on the molecular weight, the present study was carried out using a homogeneous polymer fraction as one of the substrates and mono‐functional model compound as the other. The results show that the rate constant is dependent on the density of segments in the coil of the reacting macromolecules. The changes in the density of segments in the coil will characterize here the variation of diffusion coefficient inside the macromolecule coil.
Studies on poly(vinyl chloride) compatibility with other polymers. IV. Poly(vinyl chloride) with butadiene‐α‐methyl‐styrene copolymer blends
Authors: Feldman Dorel , Rusu Mihai
Published: June 2010

One studies the compatibility of poly (vinyl chloride) with butadiene‐α‐methylstyrene copolymer (BAMS) using the dielectric and dynamic properties and also the physico‐mechanical indexes; these values were determined at various temperatures and compositions.

The results showed that the compatibility of these two polymers depends on their blending ratio. Systems which have less than 60% BAMS copolymer are incompatible, while the blends with more than this amount of elastomer are compatible. The compatibility of the blends in which the elastomer is predominant is due to the polarization action of high polar groups of poly (vinyl chloride) on the benzene rings from the copolymer macromolecules.
Thermal conductivities of amorphous polymers
Authors: Hands D. , Lane K. , Sheldon R. P.
Published: June 2010

Although at the present time no precise agreement between theory and experiment exists for amorphous polymers, as might be expected on the limited understanding of the liquid state, nevertheless certain trends in the thermal conductivity of these materials may be predicted with some confidence. This paper considers the influence of two factors, temperature and polymer density, with a view to providing guidance to engineers concerned with the manipulation and use of amorphous polymers.
Dilute and semidilute solutions: Light and neutron scattering and osmotic pressure
Authors: Cotton J. P. , Farnoux B. , Jannink G. , Strazielle C.
Published: June 2010

Light and neutron scattering data and osmotic pressure measurement are analyzed in polystyrene solutions up to concentration of 0.1 g cm−3. The results show two different ranges of concentration. These two ranges are consistent with the dilute and semidilute ranges proposed by S. F. Edwards. The transition occurs at the concentration for which the average distance between chain is of order of magnitude of the radius of gyration.
A light scattering study of the optical anisotropy of polystyrene and polyvinylacetate latices
Authors: Petres J. J. , Deželić G. J.
Published: June 2010

By the method of light scattering, measurements were made on particles of polystyrene and polyvinylacetate latices. The angular distribution of the scattered light was measured and the partial Rayleigh ratios as well as the polarization ratios were determined. These values were measured as a function of the concentration and the measurements were extrapolated to the zero concentration. Values of the specific partial Rayleigh ratios (Hv:/c)0 and (Vh/c)0 proved to be significantly different from zero indicating the existence of the optical anisotropy of particles. The polarization ratio Dv was also found to be significantly different from zero. The optical anisotropy of polystyrene latices was found to be significantly higher than that of polyvinylacetate latices. This was ascribed to a structural anisotropy of the polymeric material within the particles. The hard polystyrene spheres show a small but existing degree of crystallinity, whereas the soft polyvinylacetate spheres, although having a finite anisotropy, show a vanishing degree of crystallinity.
The influence of cellulose structure on the swelling of cellulose in organic liquids
Authors: Philipp Burkart , Schleicher Harry , Wagenknecht Wolfgang
Published: June 2010

Using the method of a modified water‐retention value (LRV), the time dependence and final value of swelling of cellulose in various liquids are found to be determined by the cellulose structure as well as by molar volume and the solubility parameter δH of the liquid, especially its hydrogen bonding part δH and the polar part δP. The different kinetics of swelling of native and regenerated cellulose samples in some liquids of high swelling power like DMSO, as well as the strong influence of the state of drying on the final LRV with native samples, and on swelling kinetics with regenerated cellulose are interpreted by means of the concept of a “pore and void” model of cellulose structure.
Synthesis of polymers of 1,2‐disubstituted ethylenes (polymeric alcohols and their derivatives) and investigation of the influence of the nature of side groups on the properties of macromolecules
Authors: Skorokhodov S. S. , Anufrieva E. V. , Koltsov A. I. , Lushchik V. B. , Pautov V. D. , Stepanov V. V.
Published: June 2010

Methods for synthesis of polymeric alcohols and their ethers of type poly‐1,2‐disubstituted ethylenes have been considered. Cationic polymerization of cis‐1,2‐dimethoxy‐ethylene was carried out in a solvent‐nonsolvent mixture, and a polymer was obtained with a molecular weight of about 200,000 which is unusually high for this type of polymers. On the basis of PMR spectra of model compounds, poly‐1,2‐dimethoxyethylene (PDME) is assumed to be threo‐diisotactic. Intramolecular mobility and its relationship with microstructure of the polymer chain were investigated by the polarization fluorescence method. A strong influence of side group interactions on the properties of macromolecules in solution was observed. It was probably caused by the peculiarity of the chemical structure of poly‐1,2‐disubstituted ethylenes.
The rheo‐optical and mechanical behavior of a systematic series of hard‐soft segmented urethanes
Authors: Samuels S. L. , Wilkes G. L.
Published: June 2010

A battery of characterizational tests have been performed on a systematically varying series of segmented polyurethanes. These tests include small angle light scattering (SALS), small angle and wide angle x‐ray diffraction, optical and electron microscopy, and mechanical testing (both tensile and dynamic).

Observable macroscopic properties are directly correlated with and interpreted by a model based on the observed anisotropic spherulitic macrostructure which is dependent on the chemical microstructure and the sample history.
On the nature of polymeric liquid crystals
Authors: Frenkel S.
Published: June 2010

Starting from the theory of formation of liquid crystalline mesophases in solutions of rod‐like rigid chain macromolecules, developed by Flory and DiMarzio, the situation is analyzed where the flexibility parameter, f, which is essential in this theory, is variable and concentration dependent. It is shown that energetic factors of physical‐chemical origin expressed by the polymer‐solvent interaction parameter, χ1, and connected with the selectivity of these interactions may influence substantially f, changing its value from the supercritical ( > 0.63), when self‐organization in an ordered mesophase is impossible, to the subcritical, i.e., values down to f→ 0, when a spontaneous formation of a liquid crystalline phase occurs. In quite a similar manner (the analogy encompassing even the corresponding formulae) f is affected by external fields, as a result, in a stationary orienting field a system of flexible chain macromolecules may become equivalent to a unperturbed system of rigid chain macromolecules. The external field can also decrease the critical concentration of the formation of the liquid crystalline phase in rigid chain systems and liquidate the domain structure, thus transforming such a system into a unique “liquid single crystal”. This is shown to be true for the behavior of a rigid chain polymer polyparabenzamide in strong magnetic fields.

The analysis leads to the conclusion that a purely entropic formalism for the description of the formation of extended chain liquid crystals is neither necessary nor sufficient, and purely energetic factors most certainly must be taken into account. However, following incorporation of these data, it becomes possible to reduce the formation of the ordered phase to the “entropic” mechanism of Flory‐DiMarzio.
Thermodynamic nature of supermolecular order in the aqueous solutions of poly (vinyl alcohol)
Authors: Klenin V. J. , Klenina O. V. , Shvartsburd B. I. , Frenkel S. Ya.
Published: June 2010

The temperature dependence of the second virial coefficient, A2, in an aqueous solution of poly (vinyl alcohol) (PVA) has been studied by the light‐scattering method within the temperature range from 20 to 130°CC.

The experiment was carried out under conditions which rule out the aggregation of macromolecules. The temperature dependence of A2 has the form of an extremum with an unpronounced minimum between 80–90°CC. In the temperature region studied here, A2 > 0, this condition is regarded as a proof of the stability of the system with respect to amorphous separation. Consequently, the supermolecular order which forms in the PVA‐water system over this range of temperatures (see Chem. Abst, (1967), 66: 11295u; (1971) 73, 56516x; (1971) 74, 23183d) has a crystalline nature.

The literature noting an increase in the degree of sweiling with increasing temperature in the PVA‐water system in the interval 20–80°CC, which seems contradictory to a decrease in the solvent power (decrease in A2), may be explained by a decrease in the degree of crystallinity (degree of physical crosslinking) of the polymer.
Thermodynamic properties of polystyrene gels of different crosslinking density in cyclohexane
Authors: Borchard W.
Published: June 2010

An optical‐mechanical device is described with which the length of a gel and the transmitted light can be registered. The swelling curves of gels of the crosslinked polystyrene in cyclohexane have been measured in the temperature range from 10 to 70°CC. Glycol dimeth‐acrylate was used as the crosslinking agent varying from 0.05 to 3% by weight of the polymer. The swelling curves are in good agreement with those determined gravimetrically. From the slightly crosslinked gels nearly 50% soluble polymer could be extracted.

The results are compared with those of other authors and are discussed on the basis of statistical theories of swollen networks.
The effect of ion‐site interactions on the apparent molal volume of polystyrenesulfonic acid and its salts in aqueous solutions
Authors: Caillé A. , Daoust H.
Published: June 2010

Apparent molal volumes of two samples of polystyrenesulfonic acid and p‐toluenesulfonic acid and their alkaline salts in water have been determined at 25°C using the magnetic float technique. The results show that the monomeric acid and salts behave like ordinary strong electrolytes. In the case of the polystyrenesulfonates, the variation of the apparent molal volume with molar concentration does not follow the simple Masson's equation, i.e., φv decreases rapidly at concentration below 0.005 mole/liter. Furthermore, the additivity rule (applied to the ionic partial molal volumes at infinite dilution) does not hold too well for the strong polyelectrolytes investigated in this work. This anomalous behavior is discussed in terms of persisting ion‐binding at infinite dilution. Theoretical calculations on the variation of degree of ion‐binding with concentration indicate that the number of bound cations at infinite dilution is a function of their size.
Solution rheological properties of a copoly(ethyl acrylate‐acrylic acid)
Authors: Rauscher Raymond J. , Garfield Lawrence J. , Connelly Richard W.
Published: June 2010

This study was carried out to determine the effects of various solution and molecular parameters on the characteristic entanglement molecular weight of a copoly(ethyl acrylate‐acrylic acid) of 55:45 molar ratio. Fractions obtained by bulk precipitation, varying in molecular weight from 5,000 to 500,000, were characterized by intrinsic viscosity, light scattering, aqueous exclusion chromatography, and titration. Polydispersities of the fractions were about two; their chemical compositions were independent of molecular weight. Dilute solution properties of both the ionized and unionized polymer in several media suggest that, depending upon polymer‐solvent and polymer‐polymer interactions, the polymer may exist in a compact or a highly extended conformation. However, on the basis of the entanglement properties in concentrated solutions in the same media, it appears that the ionized and unionized polymers in concentrated solutions assume their unperturbed dimensions. Thus it follows that for this polyelectrolyte the factors contributing to chain contraction present in concentrated solutions are large enough to overcome the substantial chain expansion factors.
Hydrolyzed starch ‐ polyacrylonitrile graft copolymer solutions: Effect of shear history on transient and steady ‐ state viscoelastic behavior
Authors: Bagley E. B. , Taylor N. W.
Published: June 2010

Both viscosity ζ and primary normal stress difference (P11 ‐ P22) of water solutions of hydrolyzed starch‐polyacrylonitrile graft copolymers have been investigated, with a cone and plate rheometer, as a function of time and sample history at a variety of shear rates. At a constant shear rate the highly viscoelastic fluids show strong stress overshoot effects, both ζ and (P11 ‐ P22) rising to a maximum and then falling to a steady‐state value. Both equilibrium levels and peak heights strongly depend on sample history. Unexpectedly, oscillatory shearing of certain samples at low frequency and amplitude, before steady shearing at constant shear rate, had an extreme effect on observed peak heights of both ζ and (P11 ‐ P22) but little on equilibrium levels. Magnitude of the effect depends on the time for which the oscillations are imposed. Such behavior may be characteristic of some high molecular weight polymers in solution and useful in identifying long‐range entanglements which strongly influence the elastic properties of these solutions.
Viscoelastic properties of polyurethane block polymers
Authors: Seymour Robert W. , Cooper Stuart L.
Published: June 2010

Orientation measurements using differential infrared dichroism experiments have been applied to the study of the viscoelastic properties of polyurethane block polymers. The time dependence of the orientation function reflects the influence of both the viscoelastic nature of the blocks and of the two‐phase microstructure. A study of the effect of hard block length on the orientation response suggests the presence of an interlocked hard phase structure for most compositions. Such a structure severely restricts relaxation of orientation under strain. At very short hard segment lengths, this morphology is not present and extensive relaxation does occur.
Preparation of block copolymers by use of some new polymeric peroxides and characterization of the products
Authors: Baysal B. M. , Orhan E. H. , Yilgör I.
Published: June 2010

Block copolymers containing prepolymer segments such as poly(ethylene oxide), poly‐(propylene oxide), polybutadiene, and butadiene‐styrene copolymer and segments of a vinyl polymer such as styrene and methyl methacrylate were synthesized. A commercially available low‐molecular‐weight dihydroxyl‐terminated prepolymer was reacted with an aliphatic diisocyanate and with 2, 5‐dimethyl‐2, 5‐bis‐(hydroperoxy) hexane. The resulting polymeric peroxycarbamates were used as free radical initiators of vinyl polymerization. Various modes of preparation and the properties of the copolymers are described. Formation of block copolymers was illustrated by several characterization methods such as IR spectroscopy, elemental analysis, and elastic modulus versus temperature measurements. The modulation of the mechanical properties of the copolymers with respect to homopolymers was observed and reported by impact strength as well as other certain ASTM properties.
Macronet isoporous gels through crosslinking of dissolved polystyrene
Authors: Davankov V. A. , Rogoshin S. V. , Tsyurupa M. P.
Published: June 2010

Macronet isoporous polystyrene gels, obtained by cross‐linking of linear polystyrene in solution with p‐xylylenedichloride or 4, 4′‐bis‐chloromethylbiphenyl, differ from conventional styrene‐divinylbenzene (DVB) copolymers by high solvent‐uptake capacity, high inner surface area, and the ability to increase their volume in any solvent, including hexane, methanol, and water.
Changes in the structure of chloromethy‐lated polyethylene modified with styrene and divinylbenzene foils due to friedel‐crafts catalysts
Authors: Czarczynska Henryka , Trochimczuk Witold
Published: June 2010

The purpose of the present work was to investigate the influence of Friedel‐Crafts catalysts—SnCl4, ZnCl2, and AlCl3,—on the structure and other properties of chloromethy‐lated polyethylene (PE) foil modified with styrene (S) divinylbenzene (DVB) (S + DVB). The high‐pressure PE foil (d = 0.927) used in chloromethylation was previously modified with S and DVB in the presence of benzoyl peroxide. The foil contained 30 % (by weight) of S + DVB. The DVB content was 0.5 %‐15% related to the total of monomers, or 0.15‐4.5 % related to all other compounds (PE + S + DVB). Chloromethylation of unmodified PE foil has also been carried out.

Chloromethylation parameters have been optimized. It has been established by means of extraction that in the chloromethylation process, additional binding of PE occurs, using AlCl3—20%, ZnCl2—30%, and SnCl4—35% of bound PE. The crystallinity degree, which is 47% for modified foil, decreases after chloromethylation to 15%. The chlorine substitution ratio apparently depends on the DVB content in modified foils. For AlCl3 and SnCl4 with 0.5 and 5% DVB content, the substitution degree is ca. 90%; for 2% DVB, 80%; for ZnCl2, ca. 75 and 60%, respectively. The structure changes have been shown in photomicrographs, tensile strength and relative elongation have also been tested.
Water transport joined with ion exchange in resins
Authors: Dickel Gerhard
Published: June 2010

The exchange of ions in an ion exchanger is combined with a variation of the water sorption which results from the effect of osmosis and the osmotic pressure difference. If the ion exchange is connected with an increase of water, the process of swelling is in accordance with the result deduced from the transport scheme. This is not the case if a decrease of water takes place. In this event, a temporary formation of a pure water phase must be supposed.
On the measurement of the polymer microenvironment polarity and the effect of the polymer microenvironment polarity to some reactions on polymers
Authors: Strop P. , Mikes F. , Kalal J.
Published: June 2010

The effect of the polymer microenvironment polarity on some reactions of polymers is briefly discussed. The polymer microenvironment polarity has been measured using the Kosower semiempirical polarity scale based on the energy of the solvatochromic chargetransfer absorption band. The microenvironment polarity of synthetic vinylic polymers due to the nonpolar contribution of the polymer chain has been found to be lower than that of a solvent. Furthermore, the photochemical isomerization of the stilbene moiety in the side chain of poly (2‐hydroxyethylmethacrylate), a reaction sensitive to the medium polarity, was investigated. A satisfactory correlation was found between the determined polymer microenvironment polarity and the rates of the isomerization.
Polyphosphazene elastomers
Authors: Tate D. P.
Published: June 2010

Poly (dichlorophosphazene) rubber was discovered eighty years ago. Its rapid hydrolysis in moist air has hitherto precluded applications. The polymer was intractable and could not conveniently be modified chemically until Allcock (1965) reported that a soluble form could be obtained by careful control of the polymerization. This polymer could be substituted quantitatively with alkoxides or amines to give polymers of good thermal and hydrolytic stability. The polymers produced often have high crystalline melting points. Rose (1968) showed that use of mixed alkoxy substituents gave elastomers with low glass‐transition temperatures. Fluoroalkoxy substituents are particularly useful since elastomers with good resistance to swelling by petroleum fluids are obtained. Glass transition temperatures as low as −68°C have been observed so that the limitations of other oil‐resistant elastomers at low temperatures are absent. Toughness and dynamic flex resistance are comparable with hydrocarbon polymers and much better than in siloxane polymers. Fluoroalkoxyphosphazene vulcanizates show adequate retention of properties at 150‐200°C and withstand prolonged heating in aqueous alkali. They can be processed on conventional rubber machinery. Silica, carbon black, or clay fillers may be used. Vulcanization can be achieved with either peroxide or sulfur‐accelerator systems.
The mechanics of rubber elasticity
Authors: Treloar Leslie R. G.
Published: June 2010

This paper reviews the various attempts which have been made to represent the mechanical properties of rubber in terms of the strain‐energy function W for the most general types of strain. The inadequacy of the Mooney equation is shown by the early work of Rivlin and Saunders and also by the recent work of Obata, Kawabata, and Kawai. Of recent theories, those of Ogden and of Valanis and Landel, both of which depart from the restrictions on the form of W postulated by Rivlin, show possibilities for a more direct representation of experimental data, as well as for the simplification of mathematical analyses. General biaxial strain data by the author are shown to be capable of accurate representation on the basis of the Valanis‐Landel theory in terms of a function w(λ) of the single strain parameter λ. This function may also be expressed as an algebraic series, corresponding to the Ogden formulation.
Factors influencing the strength of rubbers
Authors: Thomas Alan G.
Published: June 2010

The strength behavior of rubbers is discussed in terms of fracture mechanics which treats fatigue and tensile failure as crack growth processes from small flaws. Crack growth can be influenced by the presence of oxygen or ozone. The nature of the vulcanizing system affects strength: crosslinks probably rupture and reform under stress. A new approach to the problem of abrasion is presented using fracture mechanics. Schallamach has shown that rubber often develops a pattern of ridges perpendicular to the direction of abrasion. In the simplest case abrasion is produced by a line contact (e.g., a razor blade) which pulls a tongue of rubber from the ridge producing crack growth at the base of the tongue. Provided the surface configuration is in a steady state, the quantity of rubber abraded can be related quantitatively to the frictional force and the crack growth characteristic of the rubber on some reasonable assumptions. Good agreement with experiment is found for noncrystallizing rubbers but the behavior of strain crystallizing natural rubber suggests that crystallization cannot occur under the conditions used so that the rubber is not strengthened by this means.
Factors affecting the sensitivity of positive electron resists
Authors: Bowden M. J.
Published: June 2010

Positive electron resists are polymeric film‐forming materials which undergo predominantly main‐chain scission upon exposure to high‐energy electrons. The irradiated regions of a selectively “patterned” film may be removed by fractional dissolution, enabling processes such as chemical etching to be carried out on the exposed substrate. Foremost in determining sensitivity (the minimum dose required to render an image developable, i.e., to produce a molecular weight distribution significantly removed from the original distribution) is the G(scission). Poly(methyl methacrylate) (PMMA) has a sensitivity of ∼10−5 C/cm2 (G(s) ∼ 1.9) compared with poly(butene‐1 sulfone) (PBS) whose sensitivity is ∼10−6 C/cm2 (G(s) ∼ 12). The molecular weight and molecular weight distribution are also of extreme importance, e.g., the sensitivity of PBS can be increased to ∼4–5 × 10−7 C/cm2 using molecular weights > 106 with low dispersitivity. Obviously, care must be taken when comparing sensitivities of two different materials.
Catalysis by polymers
Authors: Overberger C. G. , Smith Thomas W. , Dixon Kenneth W.
Published: June 2010

Poly(4(5)‐vinylimidazole) poly(4(5)‐Vlm) has been shown to be an effective catalyst, as compared to monomeric imidazole, for the hydrolysis of various nitrophenyl esters. The catalytic activity of synthetic macromolecules in general and poly(4(5)‐VIm) in particular has been attributed to the approximation of substrate and catalyst by electrostatic‐ or apolar‐bonding and to certain bifunctional interactions. In an effort to exploit the enhancement in catalytic activity derived through hydrophobic interactions between polymer and substrate, 1‐methyl‐5‐vinylimidazole, 1‐methyl‐4‐vinylimidazole, 1‐butyl‐5‐vinylimidazole, and 1‐butyl‐4‐vinylimidazole, have been synthesized and polymerized. The kinetics of the poly‐1‐methyl‐4‐vinylimidazole (poly‐1,4‐Me) and the poly‐1‐methyl‐5‐vinylimidazole (poly‐1,5‐Me) catalyzed hydrolysis of various nitrophenyl esters will be discussed presently. Poly‐1,5‐Me has been proven to be an efficient catalyst, as compared to the model compound, 1,5‐dimethylimidazole (1,5‐DMIm), towards the hydrolysis of nitrophenyl esters. The poly‐1,5‐Me catalyzed hydrolysis of the negatively charged ester 3‐nitro‐4‐acetoxybenzoic acid exhibits a bell‐shaped pH‐rate profile with a maximum at pH 5 where about 40% of the pendant imidazole groups are protonated. When long‐chain nitrophenyl esters are hydrolyzed by poly‐1,5‐Me, order of magnitude rate enhancements over 1,5‐DMIm are realized. The kinetics of the poly‐1,5‐Me catalyzed hydrolysis of long‐chain nitrophenyl esters has been analyzed in terms of the rate‐determining decomposition of an intermediate polymer‐substrate complex. In support of such a mechanism, saturation and inhibition phenomena typical of enzymatic systems have been observed.

Graft copolymers have been prepared from linear and branched polyethylenimine. These graft copolymers were studied as catalysts for the hydrolysis of activated esters in an aqueous system.

The rate enhancements for the hydrolysis catalyzed by the polymer were attributed to electrostatic and hydrophobic effects.

A study of the hydrolysis of p‐nitrophenyl acetate at varying pH showed that there were no cooperative effects between imidazoles or between imidazole and amine. The lack of cooperativity was attributed to the stereochemistry of the system.

Electrostatic effects were investigated by a study of the hydrolysis of 4‐acetoxy‐3‐nitrobenzoic acid at varying pH. A bell‐shaped pH‐rate profile was obtained indicative of an electrostatic attraction between the positive polymer and negative substrate at the maximum rate.

The large rate enhancements obtained in the hydrolysis of the esters of long‐chain fatty acids were explained by hydrophobic effects. This system was complicated by the precipitation of the acylated polymer intermediate, which caused decelerative behavior.