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IUPAC recommendations on source-based nomenclature for single-strand polymers have so far addressed its application mainly to copolymers, non-linear polymers and polymer assemblies, and within generic source-based nomenclature of polymers. In this document, rules are formulated for devising a satisfactory source-based name for a polymer, whether homopolymer or copolymer, which are as clear and rigorous as possible. Thus, the source-based system for naming polymers is presented in a totality that serves as a user-friendly alternative to the structure-based system of polymer nomenclature. In addition, because of their widespread and established use, recommendations for the use of traditional names of polymers are also elaborated.

Statistical long-chain branching occurring during the free-radical polymerization of the system sodium 4-vinylbenzenesulfonate (SSNa) and N, N′-methylene-bis(acrylamide) (MBAA) in aqueous medium was studied by ¹H NMR spectroscopy and SEC. The former method yielded the degree of conversion and the content of the three monomer units in the chain, i.e., SSNa, MBAA with pendant vinyl groups, and MBAA as branching points. It was found that the number of individual monomer units per a total of 1000 monomer units does not perceivably change with the degree of conversion and only slightly increases with increasing ratio MBAA/SSNa in the feed.

BACKGROUND: Number-average molecular weight, M n , is an important characteristic of synthetic polymers. One of the very few promising methods for its determination is size-exclusion chromatography (SEC) using on-line viscometric detection and assuming the validity of the universal calibration concept. RESULTS: We have examined the applicability of this approach to the characterization of statistically branched polymers using 22 copolymers of styrene and divinylbenzene as well as 3 homopolymers of divinylbenzene with various degrees of branching. SEC with three on-line detectors, i.e. concentration, light scattering and viscosity, enables us to evaluate experimental data by various computational procedures yielding M n and weight-average molecular weight, M w . Analysis of the results has shown that the universal calibration theorem has limited validity, apparently due to the dependence of the Flory viscosity function on the molecular shape, the molecular weight distribution and the expansion of molecules. CONCLUSION: For complex polymers, the universal calibration, i.e. the dependence of the product of intrinsic viscosity and molecular weight, [η]M, on elution volume, can differ in values of [η]M from those obtained for narrow molecular weight standards by 10-15%. The method studied is helpful for the determination of M n of polymers, in particular of those with very broad molecular weight distribution, such as statistically highly branched polymers.

A series of samples of linear aromatic polyester of 3-phenylglutaric acid and bisphenol A was prepared with molecular weights ranging from 14 700 to 92 700. The polymers were characterized by size exclusion chromatography with triple light-scattering, viscosity, and concentration detection. Hydrodynamic parameters of the chain were determined using the theory of Yoshizaki, Yamakawa, and Nitta modified by Bohdanecký and Netopilik. The chain parameters are a useful reference in the study of aromatic hyperbranched polyesters.

Stockmayer's classical theory of statistical branching of polymers, as modified by Thurmond and Zimm, and subsequently by Kilb, has been used to describe the evolution of the distribution of the degrees of polymerization with conversion up to the gel point in the copolymerization of a vinyl monomer with a small amount of a divinyl monomer. The weight fractions of molecules with a particular number of branch points per molecule, the averages of the degrees of polymerization of these molecules, and some other characteristics were calculated as functions of a complex variable—the branching parameter γ, including the composition of the monomer mixture, relative reactivities of the individual types of double bonds, and conversion. From these calculations, a few general conclusions on the behaviour of the model system can be drawn. The conclusions are likely to be qualitatively valid also for systems not strictly conforming to the model. Copyright © 2005 Society of Chemical Industry

The evaluation of the size-exclusion chromatography (SEC) concentration elution curves by means of a calibration dependence obtained in a given SEC set for a polymer different from the polymer to be analyzed results in an error in the determination of both molecular weight and molecular-weight distribution (MWD). The problem is analyzed assuming the validity of the universal-calibration concept. The differences between the true and apparent values of molecular weight, MWD and Mw/Mn depend on and are expressed in terms of the parameters of the Mark–Houwink–Kuhn–Sakurada equation, describing the molecular-weight dependence of intrinsic viscosity, for the polymer to be analyzed and the polymer used for calibration. The differences in molecular weight and the Mw/Mn ratio are typically tens of percent and, in extreme cases, can amount up to a factor of three for molecular weight and a factor of two for the Mw/Mn ratio.

The ordering of electrically conducting polyaniline particles dispersed in a non-conducting liquid, 1,2,4-trichlorobenzene, in a weak electric field (of the order V mm −1 ) has been studied. The time needed for the formation of conducting chains, depending on the applied voltage, the polyaniline concentration and the viscosity of the suspension medium, was used to calculate the effective relative electric permittivity for polyaniline, ɛ p = 4.8, responsible for the dipole-dipole interaction leading to the structure formation. Nonlinear limit current-voltage characteristics typical of electrorheological suspensions were observed. The formation of the conducting chains could be followed in an optical microscope.

Electrically conducting polyaniline particles were organized by an electric field in a liquid medium, which was subsequently polymerized to produce a polyurethane network. The changes in electrical conductivity during polymerization were recorded. The chains of conducting polyaniline particles oriented in the direction of the electric field became fixed in the polymer network. In this way, electrically anisotropic materials were produced. The conductivity in the direction parallel to the orientation was several times higher than that in the perpendicular one. The conductivity of these composite materials increases with temperature, while the electrical anisotropy decreases. The effect of electrical anisotropy is explained by simple geometric considerations.

Copolymers of aniline and p-phenylenediamine were prepared by joint chemical oxidation of these chemicals with ammonium peroxydisulphate in aqueous medium. The temperature and frequency dependences of the impedance and permittivity of copolymers were measured. The exponential dependence of resistivity on aniline content was observed.

Dissolution of polystyrene-block-poly(ethylene-co-propylene) (PS—PEP) in decane, a selective solvent for the PEP block, and dioxane, a selective solvent for the PS block, at room temperature leads to formation of metastable micellar structures, which convert into stable micelles with molar mass reduced several times after heating above ∼50°C. By comparing small-angle X-ray scattering (SAXS) and light scattering (LS) data, the following models of micellar structures are suggested: At room temperature, dissolution of PS— PEP in decane yields aggregates of micelles. These are detected by LS, while SAXS reflects the molar mass of individual micellar cores formed by PS blocks. At elevated temperature, these compound particles disaggregate and then reorganize into equilibrium micelles of reduced molar mass. Solutions of PS—PEP in dioxane at room temperature have a different character. The molar masses of the observed particles determined by SAXS are in a good agreement with LS results, so we can exclude aggregation of micelles in this solvent. Nevertheless, also here, after heat treatment, both SAXS and LS yield a molar mass that is about 5 times lower than that determined for unheated solutions. Metastable structures surviving from the solid-state morphology after dissolution in a selective solvent at room temperature may convert to classical equilibrium micelles only after heating.

Aniline was polymerized in the presence of ultrafine colloidal silica particles (hydrodynamic diameter 35 nm) in aqueous media and, given a sufficient silica concentration, colloidally stable polyaniline−silica particles were obtained. The particle size of the resulting dispersions was determined by both dynamic light scattering and disk centrifuge photosedimentometry. The typical size of these polyaniline−silica particles is in the range 300−600 nm and is insensitive to the concentration of components in the reaction mixture, temperature, or acidity of the reaction mixture. Particles produced at 0 °C are spherical and their shape becomes less defined when polymerization proceeds at 25 °C. As the silica size is increased, the composite particles become larger and their raspberry morphology more distinct. The electrical conductivity of a typical polyaniline (37.8 wt%)−silica composite is 6.1 × 10-2 S cm-1 at 25 °C. It grows with increasing temperature and does not depend on the frequency in the investigate...

The forms of polyaniline, viz. pernigraniline, emeraldine and leucoemeraldine, their mutual transformations and their roles in the chemical polymerization of aniline, are discussed. Absorption spectra of its various protonated forms and corresponding bases are reported. A simple reaction scheme is proposed to account for the colour and acidity changes during polymerization.

The chemical oxidation of aniline to polyaniline has been monitored by colour and acidity changes during dispersion polymerization. A small amount of various p-phenylenediamines or benzidine was found to accelerate the formation of polyaniline. The ability of such compounds to form cation radicals upon oxidation allows them to act as mediators in electron-transfer processes. Related chemicals, e.g. o-phenylenediamine, had little effect on polymerization, while m-phenylenediamine caused its retardation.

Optical absorption spectra of polyaniline dispersions in aqueous media have been investigated. Two absorption bands located at 340 and 610 nm are found for blue polyaniline base in ammonia solutions. The spectra of alkalized dispersions are close to those observed for polyaniline base in N-methylpyrrolidone solution (maxima at 332 and 638 nm), but the position of the maxima depends on the nature of the alkali. In the acidic region, three distinct absorption bands of the green protonated polyaniline are observed at 350, 430 and 810 nm. The spectroscopic response to change of pH is fast but additional slow changes occur and may extend for hours when close to neutral media. The absorption coefficient of polyaniline in 1 M hydrochloric acid for a local maximum between 380 and 420 nm is estimated as ϵ=31 500 ± 1700 cm2 per gram of polyaniline hydrochloride. Spectroscopy is used to follow up the dispersion polymerization of aniline. After an induction period, a fast polymerization takes place and the originally colourless solution turns blue. A subsequent change of colour to green indicates termination of polymerization.

Stable aqueous dispersions of polyaniline (PANI) have been prepared using an underivatized poly(vinyl alcohol-co-acetate) (PVAL) as a steric stabilizer. Investigation of aqueous PANI dispersions by scanning electron microscopy and light scattering revealed that oxidative polymerization of aniline in the presence of PVAL results in the formation of spherical particles. Their size does not depend on the concentration of aniline in the polymerizing system but the uniformity of the particles seems to be improved as the aniline concentration is increased at least up to a certain limit. Electron absorption spectroscopy study of PANI dispersions made it possible to follow the changes of PANI on both molecular and supermolecular levels. When the initial concentration of aniline in the polymerizing system was ca 2 wt% (at a concentration of PVAL from 2 to 10 wt%), electrical conductivity of free standing films cast from dispersions reached 10−1S/cm.

Phase behavior of a hydrogenated styrene/isoprene diblock copolymer in a dimethylformamide/methylcyclohexane demixing-solvent pair has been studied. At a fixed copolymer concentration (1% w/v), the scheme of phase behavior (temperature vs. mixed-solvent composition) of the system has been found to be complex, with several areas where various supramolecular structures are spontaneously formed. In a particular area of the scheme, a multistep demixing-solvent fractionation of the copolymer has been performed. The resulting fractions have been characterized and the data used to construct integral distribution functions of copolymer molar mass and copolymer composition. These functions have been compared with those obtained by a previously reported light-scattering characterization of the whole, unfractionated, nonhydrogenated precursor of the copolymer © 1993 John Wiley & Sons, Inc.

Brechungsindexinkremente der Copolymeren von N-Phenylmaleimid mit Styrol, Methylmethacrylat und Acrylnitril sowie der entsprechenden Homopolymeren wurden in verschiedenen Losungsmitteln bei 536 nm und 25°C gemessen. Die Brechungsindexinkremente der Copolymeren mit Styrol und Methylmethacrylat zeigten in allen verwendeten Losungsmitteln positive Abweichungen von der fur die meisten Copolymeren ublichen Additivitat. Dies wurde durch unabhangige Mesungen der partiellen spezifischen Volumina bestatigt. Mogliche Ursachen der Nichtadditivitat werden erortert. Refractive index increments of copolymers of N-phenyl maleimide with styrene, methyl methacrylate and acrylonitrile, and of the corresponding homopolymers were measured in different solvents at 536 nm and 25°C. In contrast to the usually observed behaviour, the refractive index increments of the copolymers with styrene and methyl methacrylate exhibit positive deviations from additivity in all solvents used. This result was confirmed by independent measurements of the partial specific volumes. Possible reasons for nonadditivity are discussed.

Polystyrene-block-poly(ethylene-co-propylene) solutions in decane have been investigated by dynamic and static light scattering. The dissolution of the diblock copolymer in a solvent, which is selective of aliphatic blocks, yields well-defined metastable micellar structures. These structures are converted into equilibrium micelles on heating and change into frozen micelles when cooled. A similar pattern is observed also in dioxane, which is a selective solvent for polystyrene blocks.

Methyl methacrylate was polymerized in an aqueous medium in the presence of gelatin using potassium persulfate as initiator. The dispersion mode of polymerization, when the monomer is completely miscible with water, was investigated and compared with an emulsion process, which proceeds at higher monomer concentration. Spherical and relatively uniform polymer particles were formed. Macroscopic precipitation of polymer is prevented by combination of the steric stabilization by grafted gelatin and of repulsive electrostatic interactions from the initiator residues attached to the particle surface. Static and dynamic light scattering have been used to determine the molar mass (molar mass of the whole dispersion particle, MwD ∼ 108-109 g mol−1) and hydrodynamic radius (RhD ∼ 50-120 nm) of the particles. The number of particles per unit volume does not depend on overall monomer concentration, and it is higher, and therefore the particle size is smaller, than that observed for the soapless emulsion polymerization. The addition of gelatin may be thus used to modify the particle size. Acrylonitrile dispersions were prepared under similar conditions. Unlike methyl methacrylate, this monomer does not swell the polymer particles. While poly(methyl methacrylate) particles are spherical and relatively uniform, the polyacrylonitrile dispersions consist of polydisperse aggregates of tiny polymer particles.

Several series of polyaniline dispersions were prepared by oxidative polymerization of aniline in aqueous medium. Ammonium persulfate was used as an oxidizing agent and poly(vinyl alcohol) as a steric stabilizer of dispersions. The amount of dispersion particles, their size and uniformity, and the fraction of the steric stabilizer attached to the particles were determined in dependence on the concentration of the individual components and on temperature. The properties of resulting dispersions are controlled mainly by the concentration of the oxidizing agent and by the polyaniline/stabilizer ratio

The synthesis of branched poly(methyl methacrylate) is described. The method used is based on an anionic technique with initiation by enolate ions. details of product characterization are included.

The reaction of vanadocene dichloride with sodium arsenate gives Cp(2)V(O(2)AsO(2)H). This compound was identified on the basis of the super-hyperfine coupling observed in the solution EPR spectrum. The effect of substitution was studied on the ring-substituted and ansa-bridged compounds.

When selective solvents are used for the dissolution of block copolymers, their solid-state structure may be partly preserved in solution. At room temperature, polystyrene- block -poly(ethylene- co -propylene) dissolves in decane, a selective solvent for the aliphatic block, to form a solution of metastable micellar structures with polystyrene core. These convert to stable micelles at elevated temperature; the molar mass of the micelles is reduced several times after the heat treatment. The change of the structure is explained by the existence of a frozen state of the micellar core at room temperature. A possible connection with the glass transition of the core is discussed. Static and dynamic light scattering, small-angle X-ray scattering, differential scanning calorimetry and viscometry have been used to characterize equilibrium and non-equilibrium micelles. A pronounced mutual interaction of micelles has been observed by light scattering even at a concentration as low as 5 × 10 −4 g cm −3 . The concept of sticky chains is introduced to explain the association of the micellar shells. The behaviour of micelles in another selective solvent, diisopropylether, is simpler, both effects observed in decane being absent.

Poly(methyl methacrylate) (PMMA) dispersions in decane stabilized by polystyrene- block -poly(ethylene- co -propylene) copolymer were prepared with various monomer and steric stabilizer concentrations. The number of PMMA macromolecules formed in the dispersion polymerization does not depend on monomer and stabilizer concentrations. The kinetics of polymerization seems to be only slightly affected by the colloidal character of the system. Correlations have been established between the parameters of the whole system, of dispersion particles and of the individual PMMA macromolecules.

Micellar solutions of a triblock copolymer polystyrene- block -poly(hydrogenated butadiene)- block -polystyrene, in heptane and in 1,4- dioxane 25 vol % heptane have been studied by light scattering and sedimentation velocity methods. In dilute solutions, micellar molar mass, hydrodynamic radius of micelles, average volume fraction of polymer segments in a micellar core and in the whole micelle, and the unimer/micelles ratio have been determined. While in semidilute mixed solvent solutions only one diffusion mode, corresponding to collective diffusion, has been determined, at least two modes, diffusion and relaxation ones, have been observed in spectra of decay times in semidilute heptane solutions. Micellar models have been proposed for both systems under study, accommodating satisfactorily all experimental results.

The molecular weight distribution functions of polystyrene degraded by shear stress in isopropylphenyl phosphate solution were compared with the calculated ones, obtained by assuming that up to a certain distance from each chain end the probability of bond scission is zero. Two phenomenological models were proposed for the probability of degradation in the central part of the chain. A comparison with experimental data suggests that the probability of degradation increases towards the center of the chain. Branched fractions formed by degradation in the presence of air were found to be present by the GPC method with on-line viscometric detection.

Two different units have been incorporated into polymer backbones to provide sites for potential anionic grafting reactions. In the first case, the sites were provided by p-vinylacetophenone residues, and the technique attempted involved the addition of polystyryl anions. In the second case, the functional sites were p-isopropenylstyrene residues, and these were used as initiating centres, from which grafts of poly(methyl methacrylate) were grown by means of anionic polymerisation initiated by butyllithium. Only the second method was met with success.

A copolymer, containing a minor proportion of residues derived from a special monomer with particular structural features, has been synthesised and used in a subsequent grafting step in which functional groups belonging to the special monomer residues were converted into initiating centres from which grafts were grown by means of “group-transfer” polymerisation. It is shown that this technique constitutes a satisfactory method for the synthesis of graft copolymers (or branched, i. e. comb-like, homopolymers) free from linear homopolymer, and the procedure is applied to a specific system in which the principal backbone monomer is styrene, the special backbone monomer component is (2-isobutyryloxy)ethyl methacrylate, and the grafting monomer is methyl methacrylate.

The oxidative polymerization of aniline gives rise to polyaniline which exists in a variety of forms, differing in electrical conductivity and in colour. A scheme of interrelated structures which accounts for all the spectroscopic and conductometric observations, is proposed, together with a set of equations summarizing the chemical transformations involved.

New copolymer materials based on polyaniline (PANI) were prepared. The electric and dielectric characteristics, i.e., dependences of the impedance and the permittivity on the frequency and temperature are studied.

Polyaniline dispersions can be prepared by the oxidative polymerization of aniline in the presence of the steric stabilizer, poly(vinyl alcohol). Dispersion particles are spherical and relatively uniform. Dynamic light scattering was used to determine their hydrodynamic radius and static light scattering to estimate mass-average particle mass. From a series of experiments, a typical example of the preparation and characterization of polyaniline dispersion is described.

The copolymerization of methyl methacrylate with small amounts (0.25-1 mol %) of bis (4-methacryloxybenzilidene)-1,2-diaminoethane in the pregelation stage was investigated. The mole fractions in the copolymers of the divinyl monomer, of the reacted vinyl groups of divinyl monomer, and of the totally reacted divinyl monomer units forming intermolecular crosslinks were determined experimentally and some other parameters were calculated from these quantities. The amount of intramolecular crosslinks, forming closed rings, has been shown to predominate over the amount of intermolecular crosslinks. The comparison of the experimental data with values calculated from Wesslau's theory, based on the classical concepts of copolymerization, reveals differences increasing up to an order of magnitude with rising content of the divinyl monomer. A major reason for this divergence appears to be the intramolecular crosslinking.

Statistical copolymers of styrene and acrylonitrile, covering a wide range of compositions, were synthetized by emulsion polymerization conducted to both low and high conversion. The weight-average molecular weights of the copolymers were determined by light scattering and correlated with intrinsic viscosities measured in methyl ethyl ketone and/or dimethyl formamide solutions. The copolymers polymerized in emulsion are suggested to consist of macromolecules with long chain branching. Statistische Styren-Acrylnitril-Copolymere wurden durch Emulsionspolymerisation in einem breiten Bereich der Zusammensetzung sowohl bei niedrigen als auch bei hohen Umsatzen hergestellt. Die Massenmittel der relativen Molekulmassen der Copolymere wurden mittels Lichtstreuung ermittelt und mit den in Methylethylketon- bzw. Dimethylformamid-Losungen gemessenen Grenzviskositatszahlen in Beziehung gebracht. Es wird gefolgert, das die in Emulsion polymerisierten Copolymere aus Makromolekulen mit Langkettenverzweigungen bestehen.

Copolymerisation radicalaire du macromere polydimethylsiloxane avec le methacrylate de methyle

Interaction between non-identical polymer molecules in a dilute solution of a mixture of two polymers is quantitatively characterized by the interaction parameter A 24 , which is the second virial coefficient for interaction of unlike species. The value of A 24 may be experimentally obtained by light scattering. The determination of A 24 is very sensitive to experimental error in the input data, particularly for mixtures in which one polymer is greatly in excess, and for mixtures of polymers having molecular weights differing by orders of magnitude. A slight rise in A 24 with temperature has been observed for solutions of mixtures of polystyrene and poly(methyl methacrylate) in diethyl malonate in the range 25–100 C. This change in A 24 reflects the increased mutual miscibility of the polymers in solution at elevated temperatures.

Twenty low-conversion statistical copolymers of styrene and 2-methoxyethyl methacrylate with various composition were prepared. The dependence of the copolymer composition, molecular weight, initiation efficiency and other parameters on the composition of the monomer mixture is discussed. Kinetic data are correlated by means of various models of the copolymerization kinetics. The best fit with experimental data is provided by a diffusion-controlled termination model, especially its dyad variant suggested in this study.

Solution properties of poly(2-methoxyethyl methacrylate) (PMEMA) were investigated by light scattering, viscometry, and gel-permeation chromatography (GPC). The refractive and density increments and the apparent partial specific volumes of PMEMA in various solvents were determined. The properties of cosolvent mixtures for PMEMA are discussed. The constants of the Mark—Houwink equation for PMEMA fractions were determined in methyl ethyl ketone and tetrahydrofuran. The steric factor of PMEMA was determined from viscometric data. Comparison of the molecular parameters of PMEMA calculated from the GPC data and measured by an independent method confirmed the validity of the universal calibration. The solution properties of PMEMA and poly(methyl methacrylate) are compared.

Solution properties of poly[1(2-hydroxyethyl)pyridiniumbenzene sulfonate methacrylate] and poly[1(2-hydroxyethyl)trimethylammoniumbenzene sulfonate methacrylate] were studied. Within a certain concentration range of some added low molecular weight electrolytes, phase separation occurs. The dependence of intrinsic viscosity on molecular weight was determined and the steric factor estimated for both polymers. For nonaqueous solvents, an extrapolation of the dependence of the refractive index increment of the polymer on the refractive index of the solvent leads to an apparent refractive index of the polymer, different from the refractive index determined directly by the immersion method. Some peculiarities of light scattering in solutions with no electrolyte added are mentioned.

One of the characteristic features of copolymers is their chemical heterogeneity. Examples are given of the dependence of conversion heterogeneity in the chemical composition of random copolymers on the initial composition of the monomer mixture, along with typical examples of the differential distribution functions of chemical composition. The maximum attainable values of the conversion heterogeneity parameter have been calculated depending on the copolymerization parameters. The conditions are discussed under which copolymers may acquire chemical heterogeneities high enough to be perceived or determined by fractionation or light scattering. Limits are estimated beyond which the chemical heterogeneity becomes undetectably low and the copolymers can be regarded as chemically homogeneous.

Aus der Untersuchung des Verhaltens von einigen chemisch heterogenen Modellsystemen rnit diskreten Verteilungen der chemischen Zusammensetzung (Homopolymergemische von Polystyrol und Poly(2-methoxyethylmethacrylat) und Gemischen ihrer statistischen Copolymere) bei der Phasentrennung in verschiedenen Losungsmittelsystemen ergab sich folgendes : (a) Die Trennung solcher Systeme lediglich nach der chemischen Zusammensetzung (ungeachtet der rel. Molekulmasse) ist im Prinzip moglich, wenn sich die einzelnen Systemkomponenten in ihrem Loslichkeits-verhalten voneinander genugend unterscheiden; (b) Die Trennung ausschlieslich nach der rel. Molekulmasse ist sehr schwierig und kann nur in Einzelfallen verwirklicht werden. Der Fraktionierungsverlauf hangt im allgemeinen immer von der chemischen Natur der Komponenten des zu trennenden Gemisches ab. The investigation of the behaviour of some chemically heterogeneous model systems having discrete distributions of chemical composition (homopolymer mixtures of polystyrene and poly(2-methoxy-ethylmethacrylate) and mixtures of their random copolymers) in phase separation processes in various solvent systems provided the following results : (a) The separation of these systems according to the chemical composition (independent of the molecular weight) is principally possible, if the solubility of the components is sufficiently different. (b) The separation exclusively according to the molecular weigth is very difficult and can be achieved only in particular cases. Generally, the fractionation process depends on the chemical properties of the components in the mixture to be separated.

In aqueous KSCN solutions the salt is preferentially desorbed from the domain of gelatin molecules, similarly to synthetic polyelectrolytes. Light-scattering measurements in gelatin solutions in 0,5 M KSCN and in a single solvent (formamide) show that both solvents are suited for the molecular characterization of gelatin at room temperature. Neglecting the effect of selective sorption in salt solutions does not cause any considerable error in the molar mass determination of gelatin.

Parameters characterizing the interaction of nonidentical polymer molecules in dilute solutions of mixtures of two polymers have been defined on the basis of Stockmayer's theory of light scattering in multicomponent systems. Various procedures for evaluation of the interaction parameters from experimental data have been compared. Specific features of the investigation of such interactions are demonstrated with the scattering behavior of the system polystyrene-poly-(methyl methacrylate)-dioxane.

The refractive index increments of linear and branched polyethylene were determined for several solvents and various wavelengths (403, 436, 546, and 633 nm), mainly at 135°C. Differences were observed between values for linear and branched samples. Data obtained in this investigation are compared with the reported ones.

Dilute solutions of a three-block styrene-butadiene-styrene copolymer in the mixed selective solvent tetrahydrofuran/allyl alcohol exhibit a more or less pronounced turbidity. Sedimentation analysis and light scattering reveal that these solutions contain two components, namely, a molecularly dissolved copolymer (unimer) and rather compact supermolecular aggregates (micelles) with a relatively narrow molecular weight distribution. The unimer/micelles weight ratio and the weight of micelles were determined as a function of the composition of the mixed solvent, temperature, and copolymer concentration. Verdunnte Losungen des Dreiblockcopolymeren vom Typ Styrol-Butadien-Styrol weisen im selektiven Losungsmittelgemisch Tetrahydrofuran/Allylalkohol eine mehr oder weniger stark ausgepragte Trubung auf. Die Methoden der Sedimentationsgeschwindigkeit und Lichtstreuung zeigen, das diese Losungen zwei Komponenten enthalten: namlich molekular gelostes Copolymeres (Unimer) und ziemlich kompakte ubermolekulare Aggregate (Micellen) mit einer verhaltnismasig engen Molekulargewichtsverteilung. Das Gewichtsverhaltnis Unimer/Micellen und das Micellargewicht wurden in Abhangigkeit von der Zusammensetzung des Losungsmittelgemisches, der Temperatur und der Copolymerkonzentration ermittelt.

The steric factors σ of homopolymers of ethyl, n-butyl, and n-octyl methacrylate, of equimolar random and alternating copolymers of these monomers with styrene, and of polystyrene, were determined by measuring intrinsic viscosities in a good solvent (butanone, 25°C) and extrapolating the data thus obtained to zero molecular weight of the polymer. For all comonomeric pairs under investigation, the σ2 of an equimolar random copolymer and, particularly, of an alternating copolymer, is higher than the arithmetic mean (σ + σ)/2 of the σ2 values of the parent homopolymers. The positive deviation from the linear dependence of σ2 on the copolymer composition, expressed as an increment of σ2, is proportional to the mole fraction of alternating dyads in the copolymer chain with in the limits of experimental error. The effect of copolymer microstructure on the unperturbed dimensions of the chains has been compared for equimolar copolymers of styrene with methyl, ethyl, n-butyl, and n-octyl methacrylate by using a relative increment ξ defined as the ratio of σ2 of the alternating copolymer to (σ + σ)/2. The dependence of ξ on the number of carbon atoms in the alcohol substituent of the methacrylate component of the copolymer seems to exhibit a maximum for ethyl methacrylate.

Various termination models in the radical copolymerization are compared on the basis of available experimental data for the dependence of the initial rate of copolymerization on the composition of the monomer mixture. A diffusion-controlled model seems to be more adequate for the majority of reported data than a chemically controlled one. The potential effect of activity coefficients in calculations of the initial rate of copolymerization is discussed.

Statistical copolymers were prepared from N-carboxyanhydrides of L-valine and γ-benzyl-L-glutamate in dioxan with triethylamine as an initiator. The copolymerization conversion was determined by ir spectroscopy, the copolymer composition by amino acid analysis, and the molecular weights by light scattering. The monomer reactivity ratios were found to be rVal = 0.14 and rGlu(OBzl) = 6.4. High-molecular-weight copolymers are formed even at low conversions. The content of β-structure in the copolymers was estimated from the ir spectra in copolymerization mixtures. The sequence-length distribution of L-valine and γ-benzyl-L-glutamate copolymers was calculated and its dependence on copolymerization conversion is discussed. Relations between the sequence-length distribution and the content of β-structure were studied. It was found that the content of β-structure in samples with the same composition is different for low- and high-conversion copolymers. The formation of β-structure in copolymers in the copolymerization mixture requires a certain minimal sequence length, which has been found to be about 6 valine units.

The technique of measurement of light scattering from dilute polyethylene (PE) solutions is reviewed. Conditions are discussed under which various PE samples can be characterized. The choice of the solvent affects the accuracy of molecular weight determination. It appears that measurement with thermodynamically poorer solvents yields results subjected to a smaller error. The interpretation of light scattering data is often disturbed by the presence of supermolecular structures in PE solutions. The effect of reprecipitation on the behavior of PE samples is described. The measurements were mostly performed on PE standards and on the Czechoslovak sample Liten Macro.