bluuebunny/crossref_metadata_2025 huggingface dataset:
Composite protostructures: An exercise in model building
Authors: Hahn C. W.
Published: June 2010

One of the most evident characteristics of life, at the subcellular, macroscopic level, is the phenomenon of structure, i.e., the anisotropic organization of matter and processes in space and in time. However, if we know a good deal about the (macroscopically isotropic aspects of the) chemistry of life, our understanding of structure (as defined above) does not go very far beyond what is known about the configuration and conformation of single (macro)molecules, or of finite or infinite symmetrical assemblies of (macro)molecules, and about changes in configuration, conformation, or spatial arrangement of these units – changes to which stereospecific intramolecular and intermolecular interactions can be assigned as causes. As to other macroscopic structures (on a scale comprised between the dimensions of single macromolecules and those of cells), the belief seems to prevail that the principles governing these are of the same kind as the principles governing the former: that “stereospecific intrinsic molecular determinisms” unambiguously determine every kind of biological structure.

In this article, attention is drawn to other macroscopic mechanisms for the organization of matter and processes, mechanisms which are known in classical polymer chemistry under the topics of microphase separation and phase inversion, which are phenomena proper to the macroscopic level of size, not necessarily predictable from, or reducible to, stereospecific molecular determinisms. An attempt is made, at the level of hypothesis and speculative model building, to investigate the possible significance of these phenomena for biological organization.
EPR‐untersuchungen des radikal‐ und molekularzerfalls von hydroperoxyden unter einfluss von zink dialkyl dithiophosphatinhibitoren
Authors: Kateva J. , Ivanov S.
Published: June 2010

The decomposition of the cumene, tetralin, and t‐butylhydroperoxides in the presence of zinc diisopropyl dithiophosphate and of radical‐type inhibitors has been studied. A poisoning of the catalyst and a further change into an inactive form has been found. This leads to an inhibition of the overall decomposition rate of the hydroperoxides. It is suggested that the accumulation of RO* radicals arising from the thermal decomposition of the hydroperoxides reactivates the inactive catalyst. Based on the consumption of phenyl‐β‐naphtylamine and the stable 2,2,6,6‐tetrametylpiperidinoxyl radical, a homolytic decomposition of the hydroperoxides has been shown to take place. The rate of decomposition of the hydroperoxides to free radicals is 103 times slower than that leading to molecular products.
Inhibition of cumene oxidation by polyarylenes
Authors: Ivanov A. A. , Berlin A. A.
Published: June 2010

The kinetics of the initiated cumene oxidation at 60°C in the presence of polyarylenes (polyanthracene (PA), polynaphthalene (PN), copolymers of benzene with anthracene (AB), and naphthalene (NB) has been investigated. The initial oxidation rate dependence upon the initial concentration of inhibitor has been described by the equation obtained for inhibition mechanism which defines the radical attaching to a molecule of inhibitor as the rate limiting step of the reaction, rather than the reversible complex formation. Radical reactivity of polyarylenes increases in the order NB < PN < PA < AB, that is, it is consistent with the increase of reactivity of repeating units of polymer molecules. Reactivity of PA (calculated per repeating unit) is unaffected by the increase of molecular weight. The total quantity of radicals consumed by one molecule of inhibitor is calculated to be equal to 0.29; 1.4; 7.6 and 11 for NB, PN, PA, and AB, respectively. The most active centers in the reaction of inhibition are shown to be paramagnetic centers. Conjugation degree in polyarylene molecules diminishes during the course of the reaction. The main products of PA transformation are PA molecules having 1,4‐anthraquinone units.
The reactivity of antioxidants with peroxy and alkoxy radicals in the presence of transition metals. II. Radical processes in multicomponent antioxidant systems
Authors: Tkáč A. , Omelka L.
Published: June 2010

In nonpolar solvents the mechanism of bimolecular substitution reactions between t‐butyl‐peroxy and t‐butoxy radicals with different phenols and diarylamines was quantitatively studied by means of electron paramagnetic resonance (EPR) spectroscopy in the temperature range of +70 to −140°C. The selective reactivity, in the ligand field, of cobalt complex‐bonded radicals [Co] BuO2, [Co] BuO., and the free continuously generated noncomplex‐bonded BuO2 and BuO radicals to antioxidants are compared. The antioxidant ArH forms with cobalt (II)‐acetylacetonate a complex [Co(acac)2]2 [Arh]n = 1‐4 and prevents the subsequent reactions of the primarily generated RO. radicals with the transition metal (RO. + Co(II) → RO′ + Co(III)) and with the excess of hydroperoxides (RO. + ROOH → ROH + RO2). The concentration and the ratio of RO. and RO.2 radicals in a chain oxidation process in the presence of phenyl β‐ or α‐napthylamine (Ar1HNAr2) can be determined from the different EPR spectra of fixed [Co] [Ar1 NAr2]. and free stable nitroxy (Ar1HNAr2) radicals.
Antioxidants and stabilizers. XXXIX. GPC analyses of the additives for polyolefins and pvc used as food wrappings
Authors: Protivová J. , Pospíšil J. , Zikmund L.
Published: June 2010

Gel permeation chromatography (GPC) method, either alone or in combination with thin‐layer chromatography (TLC) or PC, has been used for determining the number of mononuclear and binuclear phenolic antioxidants used for the stabilization of polyethylene, and of some organophosphites and organotin compounds suitable for the stabilization of poly(vinyl chloride) (PVC). A differential flow refractometer and a UV detector were used for the detection of the compounds by GPC. Qualitative determination of the components of more complex mixtures is facilitated by the use of a curve resolver. Particular attention has been devoted to the types of stabilizer approved by the food codex. The data on PVC stabilizers have been complemented by the Ve values of the plasticizers, and their interference with the stabilizing components has been investigated. The control analyses have been carried out on mixtures of stabilizers and polymer extracts.
Antioxidants and stabilizers. XLVI. Transformations of antioxidants during inhibited oxidative degradation: Dihydric phenols in tetralin and polypropylene
Authors: Pospíšil J. , Taimr L. , Horák J.
Published: June 2010

An investigation was made of reactions of 2‐tert‐butylhydroquinone and 4‐tert‐butyl‐pyrocatechol with tert‐butylhydroperoxide and tetralylhydroperoxide in the presence and absence of a cobalt catalyst, modeling the transformations of these antioxidants during inhibited oxidation. The reaction product was a benzoquinone derivative in the first case and a mixture of benzoquinone and hydroxybenzoquinone, in the second. The formation of products also corresponded to the transformations of both isomeric tert‐butylated benzoquinones caused by tert‐butyl hydroperoxide. In agreement with the investigated model the same products of the oxidative transformation of dihydric phenols during inhibited oxidation of tetralin and atactic polypropylene were detected. Under the conditions for oxidative degradation of polyolefins at temperatures above 150°C, deactivation due to direct oxidation with oxygen must also be taken into account. The extent and rate of the formation of transformational products is one of the reasons for different antioxidative activity of isomeric dihydric phenols.
Sorption of water vapor in partially hydrolyzed poly(vinyl acetate)
Authors: Spencer H. Garth , Honeycutt S. C.
Published: June 2010

The diffusion and sorption properties of water vapor‐polymer systems are of considerable interest because these properties are uniquely influenced by certain structural features of the polymer, i.e., the presence of hydrophilic groups, and because many uses of polymer membranes and films depend on their water permenation characteristics. The concentration dependence of the diffusion coefficient D varies from a conconstant or slightly decreasing function in hydrophobic polymers [1] to a strongly increasing function in hydrophilic polymers [2].

The sorption kinetics of H2O and D2O in copolymers of partially hydrolyzed poly(vinyl acetate) (PVAc) is the subject of this study. The value of D and its lack of dependence on concentration in PVAc is well known [3,4], and a strong dependence of D on concentration in poly(vinyl alcohol) (PVOH) has been reported [3, 5]. Emphasis in this work is placed on the comparison of the sorption kinetics within the sequence: PVAc, VAc‐VOH copolymers, and PVOH.

Transient‐state sorption studies in water vapor‐polymer systems present special measurement problems [5, 6]. These problems and their limitations on the results are discussed.
Peculiar features of emulsion copolymerization with functionally substituted water‐soluble comonomers
Authors: Yeliseyeva V. I. , Petrova S. A. , Zuikov A. V.
Published: June 2010

Despite the considerable interest displayed by industry in latex polymers with functional groups, the study of the process of producing such latexes by the method of emulsion polymerization has just started. It should be expected that the introduction of functional groups into the interphase layer will entail a change in the course of the colloid and polymerization processes in the reaction system. In this work, the authors studied precisely this aspect of the process of emulsion copolymerization. Correlation between the polarity of a monomer (or monomer composition) on the one hand, and the kinetics of polymerization and adsorption of the emulsifier, on the other, has been shown in the case of alkyl acrylates and their copolymerization with functional monomers differing in their solubility in water. It has also been shown that localization in the interphase layer of functional groups capable of interaction, for instance, owing to the formation of hydrogen bonds, sharply intensifies the effect of these groups on the mechanical and thermomechanical properties of a polymer obtained through emulsion polymerization. The same fact leads to localization of crossing processes in interglobular regions in a latex polymer.
Self‐condensation of aromatic tetraamines and their polycondensation with some tetrachloro compounds
Authors: Banihashemi A. , Marvel C. S.
Published: June 2010

Several ladder and partial ladder polymers have been synthesized by self‐condensation reactions of 1,2,4,5‐tetraaminobenzene, 3,3′,4,4′‐tetraaminodiphenylether, 3,3′‐diamino‐benzidine and 3,3′, 4,4′‐tetraaminodiphenyl sulfone in polyphosphoric acid. These products are highly colored and have good thermal stability. Polyquinoxaline or dihydrophenazine or a mixture of these two recurring units seem to form these compounds. These compounds are slightly soluble in methanesulfonic acid and concenterated sulfuric acid and have inherent viscosities in the 0.2–0.4 range. Also, new ladder and partial lader aromatic heteropolymers have been obtained from 1,2,5,6‐tetraaminoanthraquinione with 2,3,7,8‐tetrachloro‐1,4,6,9‐tetraazaanthracene, 2,2′,3,3′‐tetrachloro‐6,6′‐diquinoxaline, 2,2′,3,3′‐tetrachloro‐6,6′‐di‐quinoxalylether and 2,2′,3,3′‐tetrachloro‐6,6′‐diquinoxalyl sulfone. In these cases poly‐condensation was carried out both in solution and in melt. Their inherent viscosities were in the range of 0.1–0.44. These polymers were also highly colored, have good thermal stability, and were soluble in methanesulfonic acid and concentrated sulfuric acid.
Copolymerization of unsaturated 1,3‐diox‐ane derivatives with maleic anhydride
Authors: Maśalińaska‐Solich Jolanta , Jedlińaski Zbigniew
Published: June 2010

The copolymerization of unsaturated 1,3‐dioxane derivatives and maleic anhydride in the presence of α, α azobisisobutyronitrile was investigated and alternating copolymers have been obtained. It has been shown that unsaturated 1,3‐dioxane derivatives form a charge‐transfer complex with maleic anhydride. The equilibrium constants of the charge‐transfer complexes were determined by NMR spectroscopy. The mechanism of the polymerization was discussed.
Radical copolymerization of maleic anhydride with organotin acrylates
Authors: Rzaev Z. M. , Sadykh‐Zade S. I.
Published: June 2010

Copolymerization of maleic anhydride (MA) with trialkylstannylmethacrylates has been studied. Copolymerization constants (r1 r2) have been determined for maleic anhydride and trialkylstannylmethacrylates, the parameters Q2 and e2 have been calculated for (CH3)3Sn‐ (C2H7)3 Sn‐ and (n‐C4H9)3Sn‐ and (n‐C4H9)3Sn‐ methacrylic acid derivatives: Q2 = 0.31, 0.27, 0.23 and 0.18; e2 = − 0.64, − 0.75, − 0.81 and − 0.88. Kinetic regularities of the reaction have been studied. It has been shown that organotin copolymers composition, as well as their model compound structures, are characterized by the occurrence of coordinate bonds of type. There has been revealed the effect of internal complexation in radical copolymerization responsible for both monomer links laternation along macromolecular chain and possible stereodirection of the reaction. The reactivity of complexomers MA‐TBSM and MA‐ Styrene (St) has been studied by means of terpolymerization.
Paracrystallinity of hot stretched linear polyethylene cut in slices parallel to the fiber axis and graft copolymerized with styrene
Authors: Čačković H. , Loboda‐Čačković J. , Hosemann R.
Published: June 2010

Linear polyethylene (PE), hot stretched 10‐fold at 80°C and cut into 0.1 mm‐thick slices parallel to the fiber axis was annealed for 102 min at 120°C and then graft copolymerized in styrene by varied doses of 60Co up to 0.4 Mrad. The ungrafted styrene was washed out and the sample then vaccum dried for 24 hr. Again, by a combined analysis of small and wide angle x‐ray scattering (SAXS and WAXS), characteristic changes can be observed during the first 40% increase of weight ΔG. The diffraction analysis proves with the help of the theory of paracrystals, that microslices parallel to the plane of cutting are produced, within them the g13‐value of the paracrystalline superlattice decreases till ΔG = 20% by 4% and reaches its old value g13 = 28% again at ΔG = 45%, while g23, orthogonal to the slices, till ΔG = 20% increases by 2% and then decreases by 4% to the value g23 = 30% at ΔG = 45%. The graft copolymerization up to ΔG = 20% mainly takes place in the “amorphous” layers of the ultrafibrils, until the shortest PE tie molecules are stretched to such an amount that families of adjacent microparacrystals build up common backfolding surfaces. Above ΔG = 20% all styrene graft copolymerizes in the lateral grain boundaries of the ultrafibrils. At ΔG = 40% they reach a main thickness of ∼ 30 Å. Then the adhesive forces between adjacent microparacrystals are so weakened that they are pushed back into their old position with larger g13‐values, by which g23 automatically reaches a 4% smaller values. At ΔG = 200% the lateral grain boundaries are 140 Å thick in the average and can not grow more at higher doses, since now the PE tie molecules between lateral microparacrystals are stretched out too. The importance of these grain boundaries between adjacent ultrafibrils is pointed out. Though contrary to “amorphous” layers they practically have the same electron density as the microparacrystals they play an important role for the physico chemical behavior of the polymers which can not be understood by the conventional two phase model. Some new observations of distortions in the microparacrystals depending on the degree of graft copolymerization are described. They give hints about kinks and kink blocks in the microparacrystallites.
Polymerization of vinyl chloride by organometallic compounds III. Characterization of the structure of poly (vinyl chloride) samples prepared by various methods
Authors: Kolínský M. , Jíšová V. , Lím D.
Published: June 2010

The polymerization of vinyl chloride by various organo‐lithium compounds, either alone or engaged in various complexes, yields polymers which show higher thermal stabilities than polymers resulting from polymerizations initiated by customary radical catalysts. By comparing various samples prepared under different conditions, an attempt has been made to find out what the structural factors are which have such a significant effect on the improvement of the properties of these more thermostable polymers.
Ion exchange of polyacrylic acid grafted on polypropylene
Authors: Pegoraro Mario , Penati Amabile
Published: June 2010

Samples of polypropylene grafted with polyacrylic acid, homopolymer free, containing different amounts of polyacid and having different physical formation (moldings, powders, membranes, films) have been put into contact with solutions at various NaCl concentrations. The exchange kinetic has been followed through pH measurements; the kinetic is influenced by the diffusion; at the end it is possible to come to an equilibrium state, the constant of which has been calculated by several measurement cycles. The value of the constant is not dependent on the physical state of the examined samples and is practically the same determined using polyacrylic acid homopolymer insolubilized by the presence of NaCl.
The influence of supermolecular structure on linear polyethylene drawing
Authors: Korsukov V. E. , Marichin V. A. , Miasnikova L. P. , Novak I. I.
Published: June 2010

The influence of the supermolecular structure type of linear polyethylene films on the relationship between the strengthening process and loss of strength at drawing has been studied by the infrared spectroscopy technique. It has been found that the progress of the strengthening process (which is connected with the macromolecular segments orientation in the microfibril amorphous region), as well as the loss of strength process (which is caused by macromolecules scissions), is strongly influenced by the initial supermolecular structure.
Effect of orientation on radiation behavior of polyolefins
Authors: Yurkevich V. G. , Karpov V. L. , Zverev B. I. , Aleksandrova L. B.
Published: June 2010

The fundamental radiation‐chemical reactions under irradiation, destruction and crosslinking of macromolecules, primarily depend on the molecular structure. However, the action of radiation on polymeric fibers (anomalous deterioration of strength properties) obtained out of the same polymer occurs depending on the dose. This results from the character of the conformation of the macromolecules in the stretched polymer. To solve this question, the change of solubility, characteristic viscosity, and gelation under irradiation were studied.

The orientation parameter was studied by the optical microscope, and isometrical heating, the radiothermoluminescence and roentgen‐structure were analyzed, also. The obtained dependences were compared with the change in tensile strength of polyolefin fibers (polyethylene, polypropylene) under irradiation. It was determined that the degree of orientation of the polymer has an essential influence upon the radiation yield of the reaction of destruction and crosslinking of macromolecules. Structure changes in polyethylene fibers exposured to a radiation dose of from 0 to 2000 Mrads were studied. The influence of the postirradiation treatment on the structure was studied, too. The behavior of fibrous material after irradiation is predominantly influenced by its chemical shructure; the behavior of a fiber is not very different from that of the base polymer in some other form. The rather remarkable effects that have been observed with some materials (e.g., polyethylene) during irradiation have stimulated research toward finding improved fibers for use in textiles. This trend is reflected in much of the literature that deals with radiation effects on fibrous materials.

The modification of textile fiber properties by radiation per se to produce improved products does not appear promising. As a gross effect, the properties of all textile materials are harmed by exposure to radiation under ordinary conditions. Hence the action of radiation on polymeric fibers obtained from the same polymer causes the anomalous deterioration of strength depending on the dose.

This investigation was concerned with the effect of orientation on the radiation behavior of polymers, and was carried out on manufactured polyolefin fibers (polyethylene (PE), and polypropylene (PP)). The change of solubility, characteristic viscosity, and gelation mechanical properties by radiation were studied. The orientation parameter by the optical microscope, the isometrical heating, the radiothermoluminescence, and roentgen structure were analyzed, too.
Isothermal crystallization of low density polyethylene and chlorinated polyethylenes by calorimetry
Authors: Erä Väinö , Venäläinen Heikki
Published: June 2010

Isothermal crystallization of LDPE and CPE with varying chlorine contents has been studied by differential scanning calorimetry. The effect of chlorine on the crystallization kinetics is shown by varying shapes of the crystallization isotherms as well as by variations of the slopes of the straight lines representing the plot of the maximum crystallinities against the crystallization temperatures.
Viscoelastic and high‐elastic properties of solutions of “monodisperse” polybutadienes in the region of critical concentrations
Authors: Ya. Malkin A. , Berezhnaya G. V. , Vinogradov G. V.
Published: June 2010

There occurs a transition from the local to the continuum viscoelasticity of polymer solutions at the critical concentration, and this affects the change of the form of the concentration dependence of all the characteristics of the viscoelasticity of the solution. For polymers of different molecular weight, the concentration dependences of their viscoelastic properties over the entire range of concentrations are determined by the volume filling of the system.
Applications of refractive index to polymer characterization. II
Authors: Albert Richard , Malone William M.
Published: June 2010

A new approach has been developed for estimating the limiting refractive index and tacticity of polymers based on structural knowledge. Furthermore, an equation is derived relating solution end‐to‐end distance to the polymer solution refractive index.
Light scattering on optically active polythiol esters. determination of molecular weight and optical anisotropy of poly‐(s) (‐)‐α‐para‐toluenesulfonamido‐β‐propiothio‐lactones
Authors: Šegudović N. , Deželić G. J. , Fleš D.
Published: June 2010

Optically active polythiol esters (PTE) were prepared by polymerization of (S)‐a‐p‐toluenesulfonamido β‐propiothiolactone in bulk, in dimethylformamide (DMF) solution, and from benzene‐water interface. By the light scattering method the optical anisotropy of the polymers dissolved in DMF was studied. In the determination of molecular weights it was found necessary to correct the Rayleigh ratios for the anisotropic scattering. The optical anisotropies of the PTE samples were found to be significantly higher than those recorded for ordinary flexible polymers. The possible secondary structure of the polymer in solution is discussed in view of the light scattering data.
The optical properties of chiral centers used as tools for studying irreversible or reversible reactions of synthetic polymers in solution
Authors: Vert Michel , Selegny Eric
Published: June 2010

The optically active manifestations (ORD and CD) of asymmetric centers of synthetic macromolecules are discussed. Well known for conformational studies, they can also detect or give quantative information about the covalent or associative reactions of these polymers when important contributions of rigid or ordered structures are absent. The Moffitt equation can not only characterize the helical conformation of polypeptides but it is also, and in a more general manner, satisfied when at least one of the Cotton effects of sufficient amplitude contributing to the ORD of the polymer is of opposite sign to the other ones. These contributions are met in several cases which are classified and illustrated. An example is given where the b0 constant of the Moffitt equation is used to determine the composition of a copolymer resulting from a chemical modification of some of the monomeric units of a polymer. The results are discussed.
Destruction of polymers with benzoxazole and imide fragments in the main chain
Authors: Tseitlin G. M. , Korshak V. V. , Rode V. V. , Vinogradov A. V. , Al‐Haidar L. T.
Published: June 2010

Thermal and thermooxidative destruction of polyimidobenzoxazoles having the same ratio of imide and benzoxazole cycles was studied. The benzoxazole cycle was shown to be more thermally stable than the imide cycle. It has been concluded from the composition of the products of polymer decomposition and the kinetics of their formation that both in vacuum and in the presence of oxygen decomposition of the polymer by a radical mechanism predominates. Above 550°C there is slight hydrolytic decomposition of the benzoxazole fragments of the chain.
On the mechanism of the thermal degradation of polyvinyl acetate
Authors: Troitskii B. B. , Razuvaev G. A. , Khokhlova L. V. , Bortnikov G. N.
Published: June 2010

The kinetics of deacetylation and benzene formation, and the polymer crosslinking and absorption spectra of PVAc during thermal degradation (in vacuo at 200–280°C with or without removal of volatile products) were studied. The effects of the molecular weight of PVAc samples and the addition of various substances such as acids, metal chlorides, amines, phenols, triphenylmethane, organic salts of Ca, and dialkyltin on the thermal decomposition of PVAc were investigated.

Deacetylation kinetics of the polymer with continuous removal of volatile products can be described by the first order reaction equation with the rate constant ket = 9.6 × 1015 e−51400/RT sec−1. The PVAc degradation rate does not depend on the molecular weight of the polymer. During the thermal degradation of PVAc, polyenes having up to six conjugated double bonds form. A scheme is proposed for the thermal degradation of PVAc by the molecular mechanism.

In the presence of volatile degradation products the kinetic curves of PVAc deacetylation have a distinct autocatalytic character. This is due to the accelerating effect of acetic acid. Degradation of PVAc is also accelerated by other acids. There is a certain correlation between the degradation rate and dissociation constants of acids. This indicates that acids accelerate the thermal degradation of PVAc by the ionic mechanism.

A rapid crosslinking of the polymer takes place in the process of PVAc thermal decomposition. This evidently results from Diels‐Alder reactions between polyenes. The inhibitors of the free radical reactions, organic salts, have no effect on deacetylation rate of PVAc.
Degradation of polyethers containing in‐chain alicyclic ring structures
Authors: Kops Jørgen
Published: June 2010

The degradation of polymers prepared by ring‐opening polymerization of methyl substituted 7‐oxabicyclo‐[2.2.1]‐heptanes has been investigated. The thermal stability was found to be dependent upon the molecular weight up to a limiting value. For the polymers with high molecular weights the thermal stability with regard to initial weight loss was found to be comparable to that of the aromatic analog polyphenyleneoxide (PPO) when the degradation occurs in inert atmosphere. The thermal degradation proceeds differently for the different polymers and while PPO carbonizes with a substantial residue, the alicyclic polymers do not discolorize during a process where quantitative conversion to volatile products takes place. Gas‐liquid chromatography established that the monomer could not be found among the degradation products. The suitability of utilization of a combination of TGA and GPC measurements for studying the course of the degradation is demonstrated. Oxidative degradation was found to proceed at a much faster rate than that of the purely thermally induced process for both alicyclic and aromatic polymers. However, for PPO it was found that 20–30% of the initial weight is lost very quickly in an exothermic reaction after which the weight loss become very slow. The oxidative weight loss for the alicyclic polymers is essentially linear with time and occurs with a rate which is slower than the initial rate for PPO.
Stressed polymer ageing under irradiation and in chemically active media
Authors: Regel V. R. , Vershinina M. P.
Published: June 2010

The results of the experimental study of the lifetime of stressed polymers under the action of irradiation of various kinds and in chemically active media are summarized. The lifetime of polymers under the action of additional destructive factors is compared with the lifetime of the same polymers in the absence of these factors. The results of the experiments are interpreted within the framework of the kinetic concept of strength.
Radiation degradation of polymethylmeth‐acrylate in the presence of liquid organic additives
Authors: Dziedziela W. M. , Sudzik R. , Kroh J.
Published: June 2010

The effect of α‐methylstyrene, ethylbenzene, and 2‐mercaptoethanol on radiation induced degradation of polymethylmethacrylate (PMM) was investigated. The deaerated viscous mixtures containing from 11 to 33 w/w % of PMM were irradiated with 60Co gamma rays and molecular weight of polymers determined by osmometry.

The degradation of PMM in the presence of additives proceeded with higher yield as compared with pure solid polymer. The yields of main chain scission G(s) were found dependent on the nature and concentration of additives. Sensibilization effect increased in the order: α‐methyl‐styrene, 2‐mercaptoethanol, and ethylbenzene as the most effective agent. Within the concentration range investigated G(s) increased linear with concentration of additives. The mechanism of processes occuring during irradiation of PMM in the presence of additives is discussed.
Influence of short‐term thermal pretreatment on the rate of acidolysis of cellulose
Authors: Rusznák I. , Tánczos I.
Published: June 2010

Cotton and regenerated cellulose had been hydrolyzed under acid conditions on thermally pretreated and untreated samples. Three to four times higher rate constants could be calculated from the loss in DP of the acid‐hydrolyzed thermally pretreated cellulose. Loss in humidity regain as well as dyestuff uptake could be observed on the same samples. Consequently the increase in the rate of hydrolysis cannot be ascribed to accessibility changes. No correlation could be found between the increased rate of reaction and the acid adsorption or the rate of its diffusion. Not enough chemical changes could be detected in the cellulose for the wanted explanation.
The conformational statistics of pectic acid
Authors: Whittington S. G. , Glover R. M. , Hallman G. M.
Published: June 2010

The effect of random insertions of 1,2‐linked a‐ and β‐L‐rhamnose units on the characteristic ratio of a 1,4‐linked poly‐a‐D‐galacturonic acid molecule was investigated. In each case the characteristic ratio decreases dramatically as the proportion of rhamnose units is increased, the effect being more marked with the β sugar than with the a sugar. The effect is interpreted in terms of kinks which are introduced into the chain by the insertion of the rhamnose units.
The initial stages of the heterogeneous degradation of alkali cellulose by oxygen in relation to the morphology of native cotton cellulose
Authors: Palma A. , Jovanović S. , Schulz G. V.
Published: June 2010

Treatment of cotton cellulose with sodium hydroxide solutions of varying concentration over extended periods in the absence of oxygen markedly decreases the intrinsic viscosity of both the cellulose in cuoxam and its cellulose trinitrate derivative (CTN) in acetone. Light‐scattering measurements show that the molecular weight does not change while the radius of gyration decreases and the second virial coefficient increases. The narrow molecular weight distribution of the native cotton is still maintained. Mild oxidation first causes the intrinsic viscosity to increase. At more prolonged oxidation times the viscosity decreases. These results are interpreted by an intramolecular cross‐linking reaction in the folded cellulose chains with the formation of chemically resistent bonds. Cleavage of the resultant cyclic structures leads to molecules with a larger radius of gyration but the same molecular weight.
Conformational variation and versatility of the connective tissue hyaluronates
Authors: Atkins E. D. T. , Brown Jacqueline H. , Landsdall Julia M. , Nieduszynski I. A. , Sheehan J. K.
Published: June 2010

Four distinct conformations for the hyaluronic acid backbone have been observed. A two‐fold helix with a projected disaccharide repeat of 9.8Å, a three‐fold helix with a repeat of 9.5Å, and two perturbed four‐fold helical conformations with projected disaccharide repeats of 9.3Å and 8.3Å. In addition the three‐fold conformations exist for both univalent and divalent salt forms in a number of two‐dimensional packing arrangements which may be described in tesselation notation.
A model for the degradation of cotton cellulose
Authors: Elema R. J.
Published: June 2010

Certain correlations have been established experimentally on degraded cotton cellulose between degree of polymerization (DP) on the one hand and the polymolecularity (quotient of weight‐average DP and number‐average DP), tenacity, and rate of degradation, on the other hand. It was found that these correlations may be accounted for by the assumption of weak and reactive spots in the cellulose macromolecules at regular intervals of about 500 base units. The same characteristic length of 500 base units follows also from recent concepts of cotton fiber structure.

According to our model all ends of the composing macromolecules in a newly matured yet undegraded cotton fiber cause areas of disorder in the crystalline elementary fibrils at intervals of 500 base units. These disorders bring about stresses that activate the chemical bonds in the rigid cellulose chains.

This model is in agreement with current ideas and is supported by various other experimental results published in the literature.
Copolymerization of acrylil and methacrylil chlorides with vinyl compounds
Authors: Nazhmiddinov Sh. , Turayev A. S. , Usmanov Kh. U. , Bazarbayev A.
Published: June 2010

Radical chain copolymerization of acrylil and methacrylil chlorides and vinyl acetate and vinyl pyrrolidone in presence of azobisisobutyronitrile allowed estimation of copolv‐merization constants. Besides, chloroanhydrides were shown to be reactive during this process. Later it was shown that in the case of vinylacetates the reaction is governed by the laws of a typical vinyl copolymerization, while the chloroanhydride‐vinyl pyrrolidone system can be characterized by certain stable relations. The formation and structural pecularities of such a compound as well as details of the process were explained by the fact of their participation in the reaction.
Multiphase structure and properties of crystalline polymers
Authors: Mandelkern L.
Published: June 2010

Although lamella‐like crystallites are a well‐established characteristic of polymer systems crystallized either in bulk or from dilute solution, major misconceptions have been engendered with respect to interfacial structures and other morphological features. A detailed analysis of a wide range of properties has allowed for a molecular description of some salient features of the structure of semi‐crystalline polymers. Solution formed crystals possess a disordered amorphous overlayer. Associated with the crystalline regions of bulk systems is a diffuse interfacial layer as well as an interzonal region, wherein the chain units which connect crystallites are in nonordered conformations. These conclusions are in complete accord with electron microscope observations.
Investigation of the glass transition and melting of polymers by nuclear magnetic resonance
Authors: Zachmann H. G.
Published: June 2010

Investigations of the glass transition and melting of partially crystalline polymers by nuclear magnetic resonance provide valuable information on the nature of noncrystalline regions. The broad line NMR signal was separated into a narrow component and a broad component by using a new method which does not imply the ambiguity usually present. From the intensity of the narrow component the mobile fraction was determined. This fraction was extrapolated to “infinite” temperature. By subtracting the mobile fraction from the noncrystalline fraction, the noncrystalline rigid fraction was obtained. Comparison of the measured second moments of the two components of the NMR line with calculated second moments of chains with fixed ends shows the following: The mobile fraction is formed by chains with either one end fixed or both ends fixed in a comparatively small end‐to‐end distance (for example, loops with adjacent reentry); the noncrystalline rigid fraction is formed by chains whose ends are fixed in a comparatively large or medium end‐to‐end distances (for example, tie molecules connecting different crystals).

More detailed information on the chains forming the mobile fraction as well as on the structure in the melt was obtained by high resolution NMR. It was shown that near range order in the melt, for example, the formation of bundles of parallel chains, causes deviations from the lorentzian shape of the NMR line. During primary crystallization the chains within the bundles of parallel chains crystallize. During secondary crystallization, extremely mobile chains outside these bundles are incorporated into the crystals.
Light scattering studies on the deformation of flexible macromolecules in flow
Authors: Heller W.
Published: June 2010

The theoretical background and a suitable apparatus have been developed for deriving from light scattering measurements in streaming polymer solutions information on the deformability, and therefore on the degree of flexibility of macromolecules. In order to differentiate between effects due to polymer deformation and those due to an extrusion, an argument based on the classical Langevin relation is used. Preliminary results on the flow deformation of polyacrylamide were encouraging as regards the potential of the method.
Monomer sequence distribution in ethylene‐propylene terpolymers measured by 13C nuclear magnetic resonance
Authors: Wilkes Charles E. , Carman Charles J. , Harrington Robert A.
Published: June 2010

Considerable progress has been made in the analysis of monomer sequence distribution in ethylene‐propylene copolymers and terpolymers. Fourier transform Carbon‐13 nuclear magnetic resonance spectra provide a significant increase in signal‐to‐noise over our previously published continuous wave (CW) spectra. Most of the methylene, methyl, and methine carbon resonances have been assigned and verified. A few uncertainties remain in the deconvolution of overlapping peaks or the prorating of coincident peaks for some of the minor constituent structures. For a series of four terpolymers containing approximately 1% ethylidenenorbornene as the third monomer, r1 r2 was determined to be 1.0. The precision is estimated to be better than ±0.2. The spectra contain enough data to ultimately provide several internal checks. When the methyl assignments are further refined, comparison may be made between the propylene sequence distributions calculated from methyl and from methine resonances. Devising a system for treating the effects of propylene inversion on the methylene resonances will allow description of the ethylene sequence distribution. The net result should be very reliable r1 r2 products for ethylene‐propylene copolymers and terpolymers of low third monomer content.
Gel permeation chromatography VII. Molecular weight detection of gpc effluents
Authors: Ouano A. C.
Published: June 2010

A detector system for GPC has been built consisting of a pressure cell and capillary viscometer, a constant flow rate pumping system, a concentration detector, and a computer interfacing system. This detector system provides two chromatograms; pressure drop (ΔP) vs retention volume and concentration (C) vs retention volume. Since at constant flow rate ΔP is proportional to the effluent viscosity η, the intrinsic viscosity of any effluent fraction can be computed from the equation,
magnified image
where subscripts 1 and 0 refer to the solution and solvent, respectively.

The precision and accuracy of the above technique were evaluated using well characterized broad and narrow molecular weight distribution polymers. Both the precision and accuracy were found to be comparable to light scattering and other classical molecular weight measurement techniques. In its present form, the molecular weight detector system was found to be very sensitive to polymers with very high molecular weights, as expected, and also useful for molecular weights less than 50,000.
Application of radiotracer techniques to polymer characterization
Authors: Screaton R. M. , Cullen P. F. , Seemann R. W. , Saunders M. D.
Published: June 2010

A method for labeling the functional groups in polymers has been developed. This method converts the COOH (or OH) groups to a radioactive ester which is easier to characterize by GPC than the parent polymer. The method is more sensitive than classical analysis and gives functionality distribution in addition to total functionality. Applications of the method are given for polymers of acrylic acid and vinyl alcohol and liquid epoxy resin.

Radiotracer techniques have been also used to confirm structure of bisphenol A epoxies by using 14C labeled bisphenol A.
Intramolecular and intermolecular aggregations in aqueous solutions of maleic anhydride copolymers
Authors: Barone G. , Di Virgilio N. , Elia V. , Rizzo E.
Published: June 2010

A study on aqueous solutions of an alternating copolymer maleic anhydride‐2,4,4,‐trimethylpentene‐1 is reported. The main feature of the hydrolysis product (PTMLA) is the remarkable interaction between nearest neighbor carboxyl groups. The interaction between neighbor dipoles is favored by the presence of hydrophobic side chains, which cause the lowering of the “local” dielectric constant. As a result, the PTMLA behaves like a polydi‐basic acid. From viscosimetric trends and other properties, it is possible to deduce that this copolymer undergoes a transition to a highly coiled form at low pH's and then to an intermolecular aggregation. It maintains an expanded conformation in a wide range of alkaline pH's. It is possible to correlate this behavior with its capacity as dispersant as well as the structural characteristics of the side chain for this and other comonomers.
Ordering in solutions of poly (vinyl alcohol) in water as detected by light scattering
Authors: Gruber E. , Soehendra B. , Schurz J.
Published: June 2010

The tendency of poly (vinyl alcohol) in water to form aggregations was studied by light‐scattering measurements. On standing at 25°CC for several days an organized phase structure was formed. This could be seen in a change of the scattering functions (angular dependence of scattered light). At small scattering angles intensity increased and weak side maxima showed up in the scattering functions. This aging process is also characterized by negative A2‐values, by a decreasing limiting viscosity number, and by increasing Huggins‐k′‐values. Speed and character of this change was found to be dependent on the concentration of the solution and the molecular weight of the sample. Models are discussed, which can lead to the observed irregular scattering functions. The most probable explanation is, that during aging gel particles are formed, which have a negative surrounding function, which has an analogous effect as weak repulsion.
Polymer dynamics in solutions and gels from Rayleigh light‐scattered linewidths
Authors: King T. A. , Knox A. , McAdam J. D. G.
Published: June 2010

Local concentration fluctuations in polymer/solvent systems are probed by laser light‐scattered linewidth measurements. Dilute polystyrene solutions are studied over the molecular weight range 4 × 103 to 1.7 × 107 and as a function of concentration. The diffusion coefficient at zero concentration can be expressed as magnified image while the concentration dependence of the diffusion coefficient D is used as a measure of thermodynamic and hydrodynamic virial coefficients and compared with available theory. Results are also presented for light‐scattered linewidths from some polystyrene/tetralin gels of known concentration and crosslink density.
Conformational changes of heparin in concentrated urea solution
Authors: Yuan Leon
Published: June 2010

Conformational changes of heparin in concentrated urea solutions were examined by viscosity and kinetic measurements. The viscosity results are treated using the relation ζsp/C = [ζ]x (1 + k/√C) in an effort to separate out the factors controlling the overall conformational changes –they are, electrostatic interaction and backbone configuration. In 10 M urea, kinetic studies of heparin viscosity revealed the following: (1) after the solution has been shaken for 2.5 hr at 25°C, both [ζ]x and k agree well with the corresponding values previously obtained in the solvents of low dielectric constants; and (2) at higher temperatures, the viscosity decreases from this value. The kinetic data suggest that the reaction consists of two consecutive processes. The first process is too fast to be followed adequately by viscosity. The second process follows first‐order kinetics and the rate constants are proportional to temperature but inversely proportional to heparin concentration. The activation energy for the second process is 35 kcal/mole. For the first process, the parameter [ζ]x increases while k decreases. In the second process, both [ζ]x and k decrease. These kinetic viscosity results suggest that the relaxation of the electrostatic interaction at high dielectric constant will cause a rapid collapse of the ionic atmosphere with an expansion of back‐bone configuration. Then, thermal motion will cause the heparin molecule to become more compact. A molecular model for the polyelectrolyte is postulated, which is a modified version of the Strauss‐Ander model.
Structural interpretation of nonlinear viscoelasticity in polymeric solids
Authors: Matsuoka S. , Bair H. E. , Aloisio C. J.
Published: June 2010

The mechanical relaxation time in a glassy polymer depends on the magnitude of strain. The stress relaxation modulus of a styrene acrylonitrile and polybutadiene composite system (ABS) was measured at strains ranging from 0.005 to 0.10. The relaxation time was observed to shorten by up to four orders of magnitude. In addition, a decrease in the elastic contribution to the modulus was observed. These two aspects of nonlinear viscoelasticity are interpreted in terms of the excess entropy and enthalpy associated with dilatation under strain, a crucial factor for ductile behavior and the formation of crazes. Up to 0.9 cal/g of the excess enthalpy associated with the stress‐induced dilatation is obtained from the differential scanning calorimetry study. As a corollary, brittle behavior following annealing is explained by the fact that it would take a greater magnitude of strain to regain a critical amount of excess enthalpy by the stress induced dilatation.
Relaxation of damped debye lattices in the primary transition region
Authors: Aklonis J. J. , Rele V. B.
Published: June 2010

A brief review of the literature concerning damped Debye lattices as models for viscoelastic relaxation in the primary transition region is presented.

We have observed that polystyrene plasticized with dioctylsebacate behaves in a fashion which is inconsistent with previous predictions based on this model. We have suggested an expanded interpretation of the model which predicts that plasticizers with solubility parameters appreciably different from that of the polymer will behave differently from diluents with the same solubility parameter as the polymer. The results of further experimentation are in accord with this new prediction.

Our work supports the contention that the damped Debye lattice is a viable model and clearly demonstrates that interchain interactions are important in determining physical properties in the primary transition region.