bluuebunny/crossref_metadata_2025 huggingface dataset:
Macroscopic, microscopic and molecular aspects of fracture in polymers
Authors: Devries K. L. , Hornberger L. E.
Published: March 2011

The distribution of stress at macroscopic and molecular levels can dramatically affect mechanical properties. This paper explores both these aspects. In the first part, quenching operations for polycarbonate and polystyrene were shown to develop favorable residual stresses as well as structural alterations (as manifested by changes in density, hardness, DSC results, etc.). The changes in these glassy polymers can be accompanied by as much as an order of magnitude increase in impact strength and fatigue life. In the other phase of our study, various analytical methods were used to investigate phenomena associated with fracture in oriented semi‐crystalline polymers. In the studies reported here, the combined effects of stress and environmental agents on mechanical strength of nylon, polyethylene, and Kevlar fibers were measured. These results, in conjunction with investigations of bond rupture kinetics, suggest that fracture in these materials involve thermally activated chain scission in which the activation energy is aided by stress and the chemical environment. Different mechanisms appear to dominate fracture in spherulitic forms of chemically similar polymers.
Designing polymer additives to minimise loss
Authors: Billingham N. C.
Published: March 2011

The solubility of additives in polymers is shown to determine the state of the additive in a processed sample and the mechanisms by which it may be lost. The loss of additives is described in terms of a model which considers the effects of solubility, diffusion rate and volatility, and it is shown that the rate and mechanism of loss depends upon these quantities and upon the sample geometry. The effects of additive structure on loss mechanism and rate are discussed and the implications for additive design are reviewed.
Functional derivatives of sterically hindered amines. 1. Glycidyl compounds
Authors: Lustoň Jozef , Vašš František
Published: March 2011

Four polymerizable glycidyl derivatives of sterically hindered amines were prepared from derivatives of 2, 2, 6, 6‐tetramethyl‐4‐hydroxypiperidine and 14, 16‐dioxo‐7, 15‐diazadispiro [5, 1, 5, 3] hexadecane. One of them is a stable nitroxyl derivative.
Physical model explaining the effect of physical ageing on dynamic mechanical and calorimetric properties of poly(methyl methacrylate)
Authors: Diaz‐Calleja R. , Perez J. , Gomez‐Ribelles J. L. , Ribes‐Greus A.
Published: March 2011

Using the theory of non‐elastic deformation based on a specific model for the mobility in amorphous polymers, an equation was obtained including the real and imaginary parts of the complex modulus and the heat capacity as a function of temperature and ageing time. Thus, the model is based on the calculation of time and temperature evolution of the population of “faults” (corresponding to an excess of enthalpy and entropy) in the structure. We employ the model with only one “characteristic” relaxation time obtained from a concept of hierarchical correlation. The parameters appearing in the equations for G* and cp are the same in each case and are obtained from classical experiments (mechanical spectroscopy, dilatometry, calorimetry, etc.), thus having a specific physical meaning. Dynamic loss tangent and specific heat of PMMA measured after different thermal histories involving isothermal ageing agrees quite well with the prediction of the model.
Thermal degradation of polyethylene
Authors: Piiroja Eduard , Lippmaa Helle
Published: March 2011

Thermal degradation of low‐density polyethylene (LDPE) in the temperature range from 450 to 525°C has been studied using a sieve‐bottom reactor with inert gas as heat‐transferring agent bubbled through the PE melt. Temperature dependence of the degradation rate was determined. Full degradation of LDPE into gaseous and wax‐like hydrocarbons (alkanes and 1‐alkenes) was achieved. Temperature rise and prolonging of the contact time increased the yield of the gaseous hydrocarbons and decreased the molecular weight of the wax‐like product.
Structural recovery of polymer glasses
Authors: Hutchinson J. M. , Ruddy M.
Published: March 2011

The structural recovery of polystyrene glasses subjected to thermal cycles in the glass transition region is studied by differential scanning calorimetry and by dilatometry. Three different types of behaviour are observed in respect of the peak in the specific heat capacity or thermal expansion coefficient on heating, and are found to be in full agreement with the predictions of the KAHR model. First, for well‐stabilized glasses, the dependence of the (main) peak temperature on heating rate and annealing time yields consistent values for the structure parameter x by means of the peak‐shift method. Second, for poorly‐stabilized glasses, the (upper) peak temperatures shift quite differently, but again consistently with theory. Third, for glasses intermediate between poorly‐and well‐stabilized conditions, both main and upper peaks can be observed simultaneously in the same endotherm.
High‐performance polyolefin composites by chemical modification
Authors: Rätzsch Manfred
Published: March 2011

The paper will give a short introducing survey on the present state of polyolefin and copolyolefin cross linking.

The combination of high‐density polyethylene (PEHD) and polypropylene (PP) with elastomers, particularly with ethylene‐propylene terpolymer (EPDM), results in high‐impact strength PP (HI‐PP) and in thermoplastic elastomers (TPE) considered as high‐performance polyolefin composites (HP‐POC). By filling of PEHD and PP, HP‐POCs with increased stiffness, modulus, and abrasion resistance can be produced. They are cost ‐ advantageous substitutes for construction materials as, for example, ABS. Possibilities and limits are demonstrated by own investigations in this field.

Best mechanical properties are obtained by reinforcement with fibres, particularly with glass fibres. Requirement for superior parameters is a chemical coupling between glass‐fibre surface or glass‐fibre size, respectively, and the PP matrix.

A new adhesive agent on the basis of siloxane allows to reach high strength and toughness of the composites. The effect seems to be due to a better mutual penetration of the adhesive agent, the size, and the PP matrix. Outlooks will be given on the further development of HP‐POC in the field of reinforcement and reactive combination with other polymers.
Melting behaviour of gelspun/drawn polyolefins
Authors: Bastiaansen C. W. M. , Lemstra P. J.
Published: March 2011

The melting behaviour of gelspun/drawn UHMW‐PE and UHMW‐PP fibres was investigated. Unconstrained UHMW‐PE and UHMW‐PP fibres melt at 142°C and 170°C, respectively. Upon constraining, by holding the fibres at a fixed length or by embedding the fibres in a matrix, an increase in the melting temperature of both fibres is observed. In the case of UHMW‐PE fibres a solid‐solid phase transition in polyethylene at 155°C from the orthorombic to the hexagonal crystal structure occurs. Above 155°C, the fibres can not sustain any load. This solid‐solid phase transition at 155°C sets an upper limit to both the maximum curing and continuous use temperature of PE‐fibre reinforced composites. In gelspun/drawn UHMW‐PP, such a detrimental solid‐solid phase transition is absent, and therefore the increase in melting temperature can be utilized effectively. For example, heating of UHMW‐PP fibres for 30 minutes at 200°C does hardly affect the room temperature Young's modulus and tensile strength if the fibre is constrained during heating.
Radiation modification of semicrystalline polymers
Authors: Dobó J.
Published: March 2011

Three problems of the radiation modification of polymers are dealt with. Different methods of grafting are compared with respect of the formation of true graft copolymer and homopolymer in the polyethylene‐styrene system; the prevention of the penetration of monomer by grafting polytetrafluoroethylene is shown; the mechanical properties of crosslinked ethylene polymers below and above the melting point are discussed.
Surface tension and mechanical properties in polyolefin composites
Authors: Pukánszky Béla , Fekete Erika , Tüdós Ferenc
Published: March 2011

Polyolefin composites were prepared with CaCO3 fillers of different specific surface area. The fillers were surface treated with stearic acid between 0 and 100% surface coverage. As an effect of the treatment, surface tension of the fillers and also polymer/filler interaction decreased. The relation between interfacial interaction and mechanical properties of the composites was analysed by the equation developed earlier to describe the composition dependence of the tensile yield stress. The characteristics of the interphase were calculated, its yield stress decreases and thickness increases with increasing surface coverage. Reversible work of adhesion can be successfully related to the tensile yield stress, but a more complicated correlation exists between the thickness of the interphase and the strength of the interaction than assumed earlier. Other mechanical properties also change with the surface treatment; modulus and strength decrease and extensibility increases with decreasing polymer/filler interaction.
Effect of fiber treatment on mechanical properties of polypropylene‐wood fiber composites
Authors: Raj R. G. , Kokta B. V. , Daneault C.
Published: March 2011

Polypropylene (PP) was reinforced with chemi‐thermomechanical (CTMP) pulp and wood flour. Different chemical treatment of the fiber a) polyethylene‐poly‐(phenyl isocyanate), b) silane A‐172 and c) epolene was carried out to improve the bonding between the polymer and fiber. PP reinforced with CTMP pulp and wood flour showed a decrease in stress values as the concentration of fiber increased in the composite. Tensile modulus generally increased with filler loading and was not much affected by fiber treatment. Experimental results of the composites were compared with theoretically predicted values.
Free volume conception op dispersed systems and formation of highly loaded composites
Authors: Kuleznev Valery N. , Kandyrin Leonid B.
Published: March 2011

The present paper deals with the study of the interrelationship between the structure and properties of a relatively new class of promising polymeric materials ‐ highly loaded composites with a liquid thermoset hinder, hardened in the course of processing. One of the main targets when creating these composites is the development of formulations containing a maximum amount of dispersed filler, while retaining, at the same time, the optimum complex of properties.
Vinyl chloride suspension polymerisation and the control of polymer properties
Authors: Smallwood P. V.
Published: March 2011

A number of poly(vinyl alcohols), used in the suspension polymerisation of vinyl chloride, have been fractionated and characterised. The most effective had the highest molecular weight and contained the most unsaturation. The more insoluble fractions gave the best balance of product properties. Reactor sampling experiments have been used to determine the mechanism of polymerisation. In most polymerisations, the final grain size is determined by factors that control the coalescence and break‐up of the monomer droplets during the first 15% conversion. It is suggested that the structure within the grains is controlled by the formation of a continuous network of PVC primaries which retards droplet contraction.
Advances in the investigation of vinyl chloride (CO)polymerization kinetics
Authors: Mrázek Zdenêk , Lukáš Rudolf
Published: March 2011

Gas chromatographic determination of unreacted monomers in periodically taken samples of a heterogeneous reaction mixture was applied in an investigation of the kinetics of suspension homopolymerization of vinyl chloride and of its copolymerization with 1‐olefins. Examples are given of the application of the method in a kinetic description of the synthesis of various types of PVC (K values 58–70), in the testing of various initiators and in the optimization of recipes and reaction conditions of the copolymerization of vinyl chloride with propene. The results presented in the form of conversion curves and time dependences of the reaction rates are discussed.
Configurational and conformational control of chemical modification and thermal degradation of poly(vinyl chloride)
Authors: Millán José‐Luis , Martínez Gerardo , Mijangos Carmen , Gómez‐Elvira José Manuel
Published: March 2011

In the light of some earlier works on nucleophilic substitution on poly(vinyl chloride) (PVC) in solution, a conformational mechanism is proposed. It considers the TT isotactic diad conformation to be the only reactive species and the reaction to be controlled by the conformational equilibria that make such conformation available. As a result all the isotactic and the heterotactic triads are capable of reacting provided that they adopt the GTTG− and the GTTT conformation, respectively. Since the replacement of a definite fraction of isotactic triads, which are assumed to be of the GTTG− conformation, results in an enhanced thermal and photochemical stability, the lability of some chlorines at such triads is proved. Further arguments in favour of the conformational mechanism are afforded through recent results of i) substitution studies in the melt and in aqueous suspension with phase transfer catalysts, ii) accurate 13C NMR measurements of triad variation with degree of substitution.
The fate of organotin stabilisers in poly(vinyl chloride) (PVC) under processing conditions and during thermal degradation
Authors: Müller Hermann A.
Published: March 2011

Quantitative 119Sn‐NMR spectroscopy is a valuable tool to identify and determine quantitatively all organotin species which are formed in PVC during processing or a thermal degradation test by reaction with the polymer or by subsequent ligand exchange reactions between different organotin compounds. By this method conversion rates of monoalkyltin and dialkyltin isooctylthioglycolates in PVC have been determined as a function of the duration of thermal treatment. It is shown that organotin stabilisers can also react with lubricants and other additives to compounds like R2Sn(SR)(OCOR) during the processing of PVC, thus influencing the efficiency of the stabilising action.
High heat applications for ELIX® 300 modified rigid PVC in injection moulding, extrusion, calandering and blow moulding
Authors: Mayrhofer P.
Published: March 2011

ELIX® 300 resins ‐ impact modified styrene maleic anhydride terpolymers ‐ allow for improvements in practical heat distortion resistance of PVC to temperatures over 100°C whilst adding impact resistance and maintaining its chemical resistance and fire retardancy. This paper describes what is meant by practical heat distortion resistance and how the semi‐compatible nature of PVC/ELIX® 300 blends helps to meet higher in‐use temperature requirements. Main properties of PVC/ELIX® 300 blends as a function of concentration and K‐value of the PVC, considerations concerning formulations and the influence of compounding techniques on morphology and properties are discussed and some practical application examples are given.
Application problems of PVC materials irradiated with high doses
Authors: Hell Z. , Junaković Z. , Ranogajec F. , Dvornik I. , Barić M.
Published: March 2011

Radiation crosslinking of PVC in the presence of triallyl cyanurate as a sensitizer, dioctyl phthalate as a plasticizer and lead and tin stabilizers was examined. Standard methods of testing PVC materials were used. Direct relations between crosslinking extent, elongation, and Vicat softening temperature changes were found. Lead stabilizers proved to be more efficient than tin stabilizers. The influence of radiation dcse on immediate and long‐term changes of PVC was investigated.
Structure defects and thermal stability of poly(vinyl chloride)
Authors: Zegelman V.I. , Titova V.A. , Pomerantseva E.Gr. , Taikova T.A. , Zilberman E.K.
Published: March 2011

The presence of polyene and peroxide structures in PVC and their contribution to the rate of thermal decomposition were determined using a large number of commercial suspension PVC samples. Two types of PVC having conjugated ‐C=C‐bonds with different reactivity towards dienophiles were found. Polymer samples of the first type react with chlorine, organic phosphites and maleic anhydride under mild conditions whereas the second type PVC under the same conditions reacts only with chlorine. The obtained data show that polyene structures in these two types of PVC are of cis and trans configuration, respectively. It was also demonstrated that the contribution of diene and peroxy groups to the rate of PVC thermal decomposition is greater than the contribution of any other anomalous structures.
Characteristics and applicational properties of peroxide suspensions
Authors: Westmijze Hans
Published: March 2011

Peroxide suspensions are liquid initiators for the manufacture of PVC with the following characteristics: low viscosity (50–500 mPa.s), good pumpability, small average particle size (5–20 μm), good dissolution rate in vinyl chloride and complete safety. Possible applicational advantages are: marginally faster polymerization, higher porosity and lower fish‐eye level of PVC. A review is given of possible causes of fish‐eyes. One of the causes is an inhomogeneous distribution of initiator over vinyl chloride droplets. An explanation of the low fish‐eye level realized with peroxide suspensions, is that (because of good dispersability in water and a small average particle size) a homogeneous distribution of the peroxide over vinyl chloride droplets is obtained in an early stage of the process.
Networks from cyanic acid esters and glycidyl ethers
Authors: Bauer M. , Bauer J.
Published: March 2011

Polycyanurates were prepared by polycyclotrimerization of aromatic dicyanates in bulk. The reaction kinetics and the resulting build‐up of a trifunctional network was modelled. Modified polycyanurates were synthesized by a co‐reaction of dicyanates with diglycidyl ethers. The statistics of the resulting network building process was modelled by cascade theory combined with a model of the kinetics of structural elements. The good agreement between theory and experiment is shown.
Network formation in an epoxy system: A kinetics, viscometric and viscoelastic study
Authors: Feve Michel
Published: March 2011

A purely aliphatic diepoxy‐diamine system has been used. It is well suited for a gelation study because the chemistry is very simple and the glass transition temperature of the obtained rubber is more than 50 degrees lower than the curing temperature. The kinetics equation, established using isothermal differential scanning calorimetry (DSC) runs, agree well with that suggested by R.J.J. WILLIAMS et al. (1984). The viscoelastic behaviour, monitored by dynamic mechanical analysis, exhibits three successive zones: viscous liquid, viscoelastic material, elastic solid. Gelation occurs in the second one, the duration of which is very short. At the gel point, we observe the behaviour described by CHAMBON & WINTER (1985): tgδ is independent of the frequency;η* and G', respectively, are proportional to ω−1/2 and ω1/2. The high values of viscosity displayed by the viscometer are wrong and the measured torque derives from the elasticity of the material.
Cooperative diffusion in partially neutralized poly(acrylic acid) gels
Authors: Ilmain F. , Candau S. J.
Published: March 2011

Poly(acrylic acid) networks swollen with water and having different ionization degrees and different polymer concentrations, were investigated using elastic and quasi‐elastic light scattering. The scattered intensity was found to vary as the ratio of the polymer concentration to the ionization degree, which shows that the osmotic pressure is dominated by counterion entropy. The behavior of the cooperative diffusion coefficient cannot be explained by the scaling theories and involves an unexpected variation of the frictional coefficient with polymer concentration.
Mechanical and swelling equilibrium characterization of high cis‐1,4‐polyisoprene networks
Authors: Queslel Jean‐Pierre , Monnerie Lucien
Published: March 2011

Equilibrium stress‐strain relationships in uniaxial extension for high cis‐1,4‐polyisoprene (Shell IR 307) networks were obtained by extrapolation of relaxation measurements to infinite time through a Bernstein‐Kearsley‐Zapas (BKZ) constitutive equation. Three series of networks were investigated, each series being characterized by its polymer precursor molecular weight. The influence of cross‐linking density was studied through varying amounts of dicumyl peroxide as cross‐linking agent. These results were used to test Flory and Erman's recent molecular theory of networks with constraints on junctions.

Swelling equilibrium experiments with benzene and cyclohexane were performed on these networks and were in agreement with the mechanical analysis. The polymer‐solvent interaction parameter for the system cis‐polyisoprene + cyclohexane was estimated to be 0.31 at 20°C in the range 0 to 0.2 of polymer volume fraction.
Electron microscopy investigations of the morphology of a polyester‐polyurethane
Authors: Schraders Sigurd , Li Xuan , Guo Fanxiu , Liu Yong , Luo Jijiang , Xu Duanfu
Published: March 2011

In the current paper the morphology of a slightly crosslinked polyester‐polyurethane (hard‐segment content ca. 33 wt.‐%) is studied by means of transmission electron microscopy (TEM).

A new staining technique based on ruthenium tetroxide was applied. This new technique allows the unambiguous visualization of the typical microdomain structure of the polyurethane and also of a wide size spectrum of globular hard‐segment‐rich domains which result from phase separation in the early stage of preparation.

The hard‐segment‐rich microdomains have a size between 1.5 and 10 nm while the globular domains span a size spectrum from 10 to 2000 nm.
Principles of the van der Waals network concept: Time‐dependent processes
Authors: Kilian Hanns‐Georg
Published: March 2011

The leading ideas behind the van der Waals modification of the Gaussian network are explained including a discussion of the meaning of the van der Waals parameters. The utility of approach is demonstrated in terms of a representation of deformations, of networks under different strains and of the heat exchanged during extension. The interpretation of stress‐strain experiments carried out on bimodal end‐linked model networks leads to a characterization of the width of the chain‐length distribution in rubbers. Finally, it is shown that the non‐linear visco‐elastic response in stress‐strain cycles of natural rubber can be understood within the framework of the classical thermodynamics of irreversible processes. The time dependent stress‐strain behaviour is fairly well described in the temperature regime of rubber‐elasticity by using a discrete small‐strain shear‐relaxation spectrum.
Chaotic dynamics and entropy elastic forces of chain molecules
Authors: Winkler R. G. , Reineker P.
Published: March 2011

The dynamic behaviour of a phantom molecular chain, consisting of mass points connected by mass‐less rigid rods, is investigated in two dimensions. The end points of the chain are fixed in space. The dynamics of the molecule are determined by Newton's equations of motion. Their numerical solution is represented in form of Poincaré sections and shows deterministic chaos. It is shown that the forces of constraint, acting on the fixed end points, fluctuate in time. The time average of these forces is calculated as a function of the extension of the chain.
A mean‐field approach of the theory of topological constraints in polymer melts and networks
Authors: Heinrich Gert , Straube Ekkehard
Published: March 2011

A new mean‐field concept is discussed for the topological constraints in polymer melts and networks. The constraining potential is assumed to be determined by the dependence of the free energy of the surrounding chains on the position of the considered chain. The concept is applied to polydisperse systems, in which a new criterion is derived to describe the onset of the influence of entanglement effects.
Distribution functions in elasticity
Authors: Eichinger B. E. , Shy L. Y. , Wei Gaoyuan
Published: March 2011

The formation of a gel or elastomer entails the linking together of molecules to form a contiguous random network that has macroscopic dimensions. Forces are propagated in networks along polymer chains and through junctions to other chains. It is important to understand the structure of the force constant matrix that describes a system as complicated as this, even in the case where the potential energy is approximated by a simple harmonic function. This force constant matrix was first formulated by James, but because it is a large random matrix, very little progress can be made in the analysis of its properties. We have opted to approach this problem with the use of large scale computations that are based upon simulations of the formation of networks. Subsequent evaluation of the eigenvalue spectrum of the matrix lends considerable insight into the equilibrium and dynamic properties of elastomers. For present purposes this analysis is couched in terms of the calculation of the probability distribution of the gyration tensor for a phantom network in which non‐bonded interactions are not considered.
Syntheses and reactions of azo‐group containing networks
Authors: Nuyken Oskar , Grunow Arthur , Pampus Gottfried
Published: March 2011

Azo monomers of the general structure magnified image have been terpolymerized with styrene and butadiene (I) to form azo‐group containing rubber (SBR).

Copolymerization of butadiene and acrylonitrile with 3 yields azo group containing nitrile rubber (II). Networks are formed, if the copolymerization of butadiene and acrylonitrile is carried out in the presence of divinylbenzene (DVB) (III) or in the presence of DVB and 3 (IV). Thermolysis or photolysis of the polymeric azo initiators (I, II) yields networks without addition of a low molar‐mass crosslinking agent. Heating or irradiation of the azo‐containing pre‐network (IV) increases the network density.

Heating a mixture of (II) or (IV) with natural rubber yields polymer blends which are stabilized by covalent links between the different polymers. The network characterization was carried out by swelling experiments.

The incorporation of the azo monomers into the azo copolymers is almost ideal under “cold rubber” conditions, meaning that the composition of the products does not change with conversion.
The macroporous network of “bead cellulose” and its response to crosslinking with epichlorohydrin
Authors: Loth Fritz , Philipp Burkart
Published: March 2011

Macroporous hydro‐ and xero‐gels of bead cellulose, prepared by thermal coagulation of cellulose xanthate after emulsification in an organic liquid immiscible with water, and subsequent decomposition to cellulose II have been modified by crosslinking with epichlorohydrin during the process of preparation as well as afterwards in different states of drying. The changes in network structure, depending largely on the ratio of crosslinking to total add‐on of epichlorohydrin, are interpreted by the counteracting effects of a “structure tightening” and a spacer action.
Establishing mechanisms for emulsion polymerizations
Authors: Casey Brendan S. , Maxwell Ian A. , Morrison Bradley R. , Gilbert Robert G.
Published: March 2011

Emulsion polymerization systems are so complex that different workers often believe contradictory mechanisms for ostensibly the same system. A number of case studies are examined wherein data have been obtained that are able to refute mechanistic postulates (as distinct from supporting a mechanism by showing that a mathematical model incorporating it is able to reproduce a limited range of data). These examples are: (1) particle nucleation (refutation of micellar entry); (2) free radical desorption (refuting its unimportance for systems with insoluble monomers, and showing that the transfer/diffusion mechanism for this process is suspect); (3) entry (refutation of 100% initiator efficiency); (4) propagation (refutation of the assumption that the propagation rate coefficient (kp) drops to zero at the glass transition); and (5) termination (refutation of the assumption that dependence on lengths of each chain can always be ignored).
On the initiation mechanism in emulsion polymerization systems
Authors: Bartoň Jaroslav
Published: March 2011

The problem of the locus of initiation in conventional emulsion polymerization is discussed on the basis of the literature survey (copolymer composition in the early stages of emulsion polymerization, particle size distribution). The idea of homogeneous nucleation of polymer particles even for non‐polar monomers is supported by recent studies of emulsion polymerization in the presence of oil‐soluble inhibitor. The method of the oil‐soluble inhibitor was also used for inverse emulsion polymerization systems. The studies have brought new experimental evidence for the locus of initiation in classical as well as in inverse emulsion polymerization systems. It seems now reasonable to accept the idea that in conventional emulsion polymerization systems the locus of initiation is the water phase. In inverse emulsion polymerization systems the results point to the phase boundary between the continuous phase and (oil‐soluble part of) inverse micelles as the main locus of initiation for the systems with oil‐soluble initiator.
Preparation and characterization of core‐shell latexes
Authors: Hergeth Wolf‐Dieter , Schmutzler Klaus , Wartewig Siegfried
Published: March 2011

Polymeric dispersions with a concentric core‐shell structure of the latex particles were obtained by a two‐stage emulsion polymerization technique. Conditions for the formation of shells on polymeric seeds are discussed. SANS and SAXS investigations were carried out in order to verify the core‐shell structure of the particles. DSC and IR measurements indicate the existence of an interfacial layer between core and shell polymers. The results are transferred to emulsion polymers containing inorganic filler particles.
Radical polymerization in micelles of surface‐active monomers
Authors: Egorov Vladislav
Published: March 2011

Photo‐ and thermoinitiated radical polymerization was investigated in solution and micelles of cationic surface‐active monomers in water. Kinetics of this process depend on the structure of micelles. Polymerization proceeds in aqueous solution of monomers, in their lamellae and spheric micelles, but doesn't occur in anisotropic ones. The polymerization rate in spheric micelles increases with the decrease of counterion size in the “head” and/or the length of the “tail” in monomer molecule. This results from the decrease of the rate of bimolecular termination reaction due to the increase of the density of micelles.
Preparation of monodisperse latexes and study of their rheological properties
Authors: Zecha Helmut
Published: March 2011

The synthesis of (monodisperse) poly(styrene) latexes was reexamined using sodiumdodecyl sulfate as emulsifier and potassium persulfate as initiator. It has been shown, that at fixed emulsifier concentration cE the variation of persulfate amount produces similar particle size variations as changes of electrolyte (potassium sulfate) concentration at a given low initiator level. For cE << cmc a maximum of particle size versus initiator or electrolyte concentrations has been found. Concentrated monodisperse poly(styrene) dispersions and carboxylated latexes up to 50% have been prepared by a carefully controlled seeding process using monomer feed.

Particle size influence on steady shear viscosity has been studied for different kinds of polymer dispersions: for electrostatic stabilized poly(styrene) latexes at high ionic strengths, for electrostatic and sterically stabilized carboxylated latexes at different pH values and for steric stabilized dispersions of poly(vinyl chloride) in plasticizer (dioctyl phthalate). All three kinds of dispersions give pronounced particle size effects on viscosity, which is different from hard‐sphere‐behaviour. Simple model equations have been formulated to describe the concentration and shear rate dependence on viscosity. Particle size influence may be discussed on the basis of the effective hydrodynamic particle diameter. Causes for the increase of the hydrodynamic particle size are given either by surface swelling or by the formation of particle clusters which are formed and destroyed within the shear field.
Effect of a bi‐unsaturated monomer on the emulsion polymerization of ethyl acrylate
Authors: Capek Ignac , Kostrubová Jana , Bartoň Jaroslav
Published: March 2011

The emulsion polymerization and copolymerization of ethyl acrylate with a bi‐unsaturated comonomer (divinylbenzene, 1,6‐hexamethylene diacrylate), present in small proportions, in the presence of anionic emulsifier sodium dodecyl sulfate have been kinetically investigated at 60°C under batch conditions by gas chromatograhy and gravimetric methods. The rate of polymerization in interval 2 was found to be proportional to the 0,37, 0,23, and 0,5 power of the emulsifier concentration for the system A (ethyl acrylate), the system B (ethyl acrylatedivinylbenzene), and the system C (ethyl acrylate/1,6‐hexamethylene diacrylate). Divinylbenzene was found to decrease both the rate of polymerization and the polymer particle size. Addition of 1,6‐hexamethylene diacrylate slightly increases both the rate of polymerization and the polymer particle size.
New prospects for “living” anionic polymerization of (meth) acrylic esters
Authors: Teyssié PH. , Fayt R. , Hautekeer J. P. , Jacobs C. , Jérôme R. , Leemans L. , Varshney S. K.
Published: March 2011

The living low temperature polymerization in polar solvents of most methacrylates, even functional ones, can now be performed by direct and experimentally convenient anionic methods, thanks to the use of α‐methylstyrene and of complex‐purified monomers. A diversified family of block copolymers has thus been generated, that are used as compatibilizing agents in the designing of interesting heterophase materials: i.e. blends of polymers and inorganic fillers, and liquid‐solid dispersions.

The living polymerization of acrylates (or of methacrylates under more drastic conditions) raises additional requirements: they have been met to a large extent by the use of specific ligands of the growing ion‐pair. Resulting structures such as f.i. block copolymers and end‐functionalized oligomers of a low dispersity, should have a great interest in the molecular engineering of (meth)acrylate‐based products.

Finally, these new initiators lend themselves to structural and mechanistic studies which should shed some light on the critical features of these living propagation processes.
Effect of reaction medium on ionic lactam polymerization
Authors: Šebenda J.
Published: March 2011

Ring‐size and substitution greatly affect the permittivity and donor‐acceptor properties of lactams and their derivatives as well as of the corresponding polymers. Permittivity changes occurring during bulk polymerization affect dissociation equilibria and the very high increase in permittivity during polymerization is responsible for the autoacceleration observed in the anionic polymerization of the seven‐membered lactam. In diluted solution, pronounced effects of the nature of solvent or additive have been observed in anionic polymerization of substituted four‐membered lactams. Whereas the initial rate of polymerization is independent of the monomer concentration, the apparent order in the monomer increases and the rate of polymerization in most solvents decreases during polymerization, except in solvents of very low polarity. Changes of permittivity and conductivity during and after polymerization indicate, that changes in the solvation and rearrangement of the growth center are responsible for its varying activity. These processes increase the reactivity during ageing of the living system. Similarly to other heterocyclic monomers, the cationic polymerization of N‐acyllactams is rather insensitive to the permittivity of the reaction medium.
A chemical approach to the problem of slow initiation in living cationic polymerizations
Authors: Zsuga Miklós , Kelen Tibor , Kennedy Joseph P.
Published: March 2011

The effect of slow initiation on initiation efficiency and MWD has been investigated, with regard to the living carbocationic polymerization of isobutylene. The initiating system trans−2,5‐diacetoxy‐2,5‐dimethyl−3–hexene(DiOAcDiMeH6)BCl3 has been investigated at −35°C in CH3Cl. Based on considerations valid also for anionic polymerizations, the following methods have been applied to increase the initiation efficiency: 1. Increasing [Mo]/[Io] (batch, AMI) or [ΔM].j/[Io] (IMA). The applicability of this method is limited by the solubility of the polymer. 2. Increasing ki/kp, by (i) increasing ki, e.g., by introducing an electron withdrawing substituent into the initiator, (ii) decreasing kp, e.g., by the addition of a strong electron donor (DMSO) to the system, (iii) using Cl‐CH2‐CH2‐Cl.
Block copolymers of polyacetals
Authors: Franta E. , Refai J. , Durand C. , Reibel L.
Published: March 2011

The polymerization of 1,3‐dioxolane was carried out using trifluoromethanesulfonic acid (triflic acid) as catalyst, in the presence of an oligomeric diol, α‐hydro‐ω‐hydroxypoly(oxyethylene) (PEOG) or α‐hydro‐ω‐hydroxypoly(oxytetramethylene) (poly‐THF‐diol). When PEOG was used, a linear increase of the number average molecular weight versus conversion was observed. A triblock copolymer was obtained as well as small cycles in their usual equilibrium concentration. When poly‐THF‐diol was used, fast transacetalization provoked the “polycondensation” of the diol through acetal linkages at the very onset of the reaction, leading to a very inhomogeneous mixture. After equilibrium was reached, through reactions involving all the various species present, a triblock copolymer was also obtained.

In conclusion, this method is well suited to prepare α,ω‐diol block copolymers in which the initial oligomeric diol constitutes the center block, while the outside blocks are made of polyacetal.
Living cationic polymerization of vinyl ethers
Authors: Nuyken Oskar , Kröner Hubertus , Aechtner Stefan
Published: March 2011

The cationic polymerization of vinyl ethers initiated by CH3‐CH(OR)(I) / R4N+A− (R = Alkyl, A− = ClO4−, BF4−, PF6−, I−, NO3−) shows the characteristics of a living polymerization. The rate of polymerization is a function of the solvent polarity, the temperature, the type and concentration of the ammonium salt. The experimental data can be explained on the basis of the secondary salt effect overlapped by some dipol‐dipol interactions of the chain end and the added salt. Functionalization of the chain end with thermolabile azo functions yields polymeric initiator which was applied for the synthesis of blockcopolymers. Vinyl ethers functionalized with furylacrylic ester groups were polymerized and crosslinked via [2+2] cycloaddition.
Living cationic polymerization of 2‐chloroethyl vinyl ether: Kinetics, mechanism and application to polymer synthesis
Authors: Héroguez Valérie , Deffieux Alain , Fontanille Michel
Published: March 2011

The cationic polymerization of 2‐chloroethyl vinyl ether initiated by HI/weak Lewis acid (I2 or ZnI2) systems has been studied from both a kinetic‐mechanistic and a synthetic viewpoint. At low temperature and in toluene as solvent, the polymerization proceeds via a living process and the kinetic order with respect to monomer varies according to the nature of the Lewis acid activator. This behaviour can be explained by the coordination of the Lewis acid with both the monomer and the chain‐end, the latter leading to a strong activation of the magnified image‐I bond towards monomer insertion.

The living polymerization obtained from divinylether precursors leads to magnified image‐I ended telechelics, and their transformation into dihydroxytelechelic oligomers has been performed.

The chemical modification of chloroalkyl side groups by phase transfer catalysis allows the attachment of specific groups without consumption of‐OH ends.
Synthetic approaches to new polymers
Authors: Schulz Rolf C.
Published: March 2011

A plenary lecture should be an introduction into the main topic of the symposium and a review about the state of art. Therefore, in the first part of this presentation different possibilities for the preparation of new polymers are briefly discussed from a chemical point of view. Some selected examples from the literature show how methods of organic chemistry can be utilized for polymer science: new catalytic systems, new monomers, modification of polymers, new poly‐reactions. In the second part, several polyelectrolytes are described: polymers with sec., tert. and quart. N‐atoms in the main chain, block copolymers and block polyampholytes. The third part deals with the problems of rod‐like macromolecules for instance oligo‐ and poly(p‐phenylene)s, poly(p‐phenyleneethynylene)s, aromatic polyimides and a new spiroionene.
Mesophase structure and some properties of liquid‐crystalline organoelement polymers
Authors: Plate N. A. , Antipov E. M. , Kulitchikhin V. G.
Published: March 2011

The structure and physico‐mechanical properties of polyphosphazene, poly(trimethylvinylsilane) and blends of polyphosphazene with polyethylene were studied. It was shown that these organoelement homopolymers form mesophase structure which can be described as condis‐crystal, and mesophase polymers are effective modifiers when mixed as blends with polyethylene, allowing to make processing more effective and obtain composites with improved mechanical properties.
Tailoring of thermotropic liquid‐crystalline main‐chain polymers
Authors: Cherdron H.
Published: March 2011

The description of the property and processing advantages of thermotropic liquid‐crystalline main‐chain polymers is followed by the discussion of chemical and physical means how to tailor such macromolecules.
The control of structure in emulsion polymerization
Authors: Lee Do Ik
Published: March 2011

Free‐radical addition polymerization can be carried out using four different processes: mass or bulk, solution, suspension, and emulsion polymerization. Of these four processes, emulsion polymerization is unique because it is a heterogeneous process, in which the polymerization reactions can take place in three different sites: in the continuous aqueous phase, on the surface of growing particles, and within the growing particles. This unique feature of emulsion polymerization offers many possibilities for designing different polymers and latexes: e.g., high‐molecular‐weight polymers, uniform copolymers, copolymers of difficult‐to‐copolymerize monomers, functionalized (surface‐modified) latexes, uniform size latex particles, grafted latexes, and structured latexes having core‐shell, microdomain structures, interpenetrating polymer networks, etc. This paper will describe several aspects of the control of structure in emulsion polymerization.
The use of group transfer polymerization for the control of polymethacrylate molecular structure
Authors: Webster Owen W.
Published: March 2011

The synthesis of polymethacrylates by a repeated silyl Michael addition reaction (GTP)a allows one to control the molecular weight of the polymer by adjusting the monomer/initator ratio. A small amount of cyclic termination occurs but in general low molecular weight dispersity is obtained. Block polymers can be made by sequential addition of monomer. Functionality present on the ketene acetal portion of the initiator will be on one end of each polymer chain. Star polymers result from crosslinking active polymer with a bismethacrylate. Initiation of bismethacrylate with bisinitiator gives a ladder polymer.
Photosensitive resist system composed of phenolic resin and aromatic azide
Authors: Nonogaki Saburo , Toriumi Minoru
Published: March 2011

Phenolic resins such as cresol novolac and poly‐(p‐hydroxystyrene) are photosensitized by the addition of an aromatic azide to give negative‐working photoresists. The spectral sensitivity can be varied from deep UV to visible region by changing the kind of azide. The system composed of poly(p‐hydroxystyrene) and a phenol ester of p‐azidobenzenesulfonic acid is expected to be useful in deep UV fine‐line lithography. The system containing 23 wt% of p‐n‐pentylphenol p‐azidobenzenesulfonate exhibits a photosensitivity about 50 mJ/cm2 at the wavelength of 248 nm.
Biologically active polymer ‐ targeting polymeric antitumor agents‐
Authors: Han Man Jung , Choi Keun Bae , Kim Ki Ho , Hahn Bo Sup , Lee Won Young
Published: March 2011

To synthesize targeting polymeric antitumor agents, poly[(2‐acetoxy‐3,4‐dihydro‐2H‐pyran)‐alt‐(maleic anhydride)] as polymer backbone, chlorophyll derivatives(CpD) extracted from silkworm excreta as targeting moiety and 5‐fluorouracil and 6‐mercaptopurine as pharmacons were selected. The polymer exhibited an antitumor activity comparable to that of cyclophosphamide in vivo. CpD as well as CpD‐polymer conjugate were localized on tumor cells in vitro and delivered to tumor tissues in vivo specifically. The targeting polymeric antitumor agents were synthesized by coupling pharmacons and CpD on the polymer chain with the aid of reactions between functionalities of the reactants and anhydride groups on the polymer backbone. Various tests of their biological activities in vivo are in progress.
Development of biopolymers for artificial skin substitutes and blood‐compatible materials
Authors: Kim Kea‐Yong
Published: March 2011

In order to develop biomedical materials we synthesized various polymers. In this study, gelatin, synthetic poly(amino acid), chitin and chitosan were chosen as the basic materials of artificial skin, polyurethane, amino acid, silicone and N‐vinyl‐2‐pyrrolidone were chosen as the basic materials of blood‐compatible materials.
Aspects of molecular design of conducting polymers
Authors: Qian Renyuan
Published: March 2011

A review discussion of the facts and factors to be considered in the molecular design of conducting polymers is presented. Topics discussed are: molecular properties and solid state properties; towards high conductivity— conjugation length and chain orientation; counter ions and ion exchange; materials design—solubilization, processability and molecular composites.
The one‐dimensional intersoliton electron tunneling conduction in doped polyacetylene: Semiconductor‐metal transition
Authors: Park Y. W. , Yoon C. O. , Lee C. H. , Shirakawa H.
Published: March 2011

The one‐dimensional intersoliton electron tunneling conduction model in doped polyacetylene, which is a semiconductor‐metal transition mechanism, is proposed. With this model, the observed two transition concentrations (y = 0.001 and y = 0.05) can be estimated correctly. In the lightly doped regime (y < 0.001), the three‐dimensional intersoliton electron hopping conduction is dominant. At the intermediate concentration regime (0.001 < y < 0.05), the electrons (or holes dopending on the dopants) can tunnel through the pinned solitons within a single chain. These tunneling charge carriers contribute to the high conductivity. But these tunneling charge carriers can give no Pauli susceptibility since they are not band‐type carriers. Instead, they are transient carriers tunneling between the two soliton sites. Finally, in the high concentration regime (y > 0.05), the pinned soliton wave function can overlap each other forming a soliton liquid. In this stage, the bond alternation of the trans‐polyacetylene chain vanishes being equivalent to the uniform bond length chain. Therefore, the metallic conductivity and finite Pauli susceptibility are expected consistent with the observed experimental results. However, since this metallic state is formed by the soliton liquid it is not a single particle like metal. The internal vibrational modes and other signals characteristic to the soliton can persist in the metallic polyacetylene.