bluuebunny/crossref_metadata_2025 huggingface dataset:
Cyclic imino ethers — Polymerization chemistry and polymer characteristics
Authors: Saegusa Takeo , Kobayashi Shiro
Published: March 2011

This paper describes recent developments in polymerization of cyclic imino ethers, 2‐oxazolines and 5,6‐dihydro‐4H‐1,3‐oxazines, which have been performed mainly in our laboratory. Cationic ring‐opening polymerizations of these two kinds of monomers gave poly(N‐acylethylenimine)s and poly(N‐acyltrimethylenimine)s, whose hydrolysis produced linear poly‐ethylenimine and poly(trimethylenimine), respectively. The mechanism of the polymerization is mainly governed by the nature of monomer and of the counter anion derived from initiator. There are two types of stable propagating species; cyclic onium species and covalent alkyl halide species. In a specific case, e.g., the polymerization of 5‐methyl‐2‐oxazoline with MeI initiator, both ionic and covalent species are involved in equilibrium and propagate concurrently. Then, a new terminology of “Electrophile Polymerization” has been proposed as a broader expression including cationic and covalent propagating species. By utilizing living nature of the cyclic imino ether polymerization, block copolymerizations between these monomers were performed. A poly(cyclic imino ether) chain becomes hydrophilic or lipophilic depending on the monomer. Product AB and ABA type block copolymers were soluble in water and showed excellent surface properties reflected by values of surface tension (γ), when A (or B) and B (or A) are hydrophilic and lipophilic. Thus, various nonionic polymer surfactants of block and graft type have been prepared from cyclic imino ethers. Finally, poly(N‐acetylethylenimine) chain showed good compatibility with poly(vinyl chloride). Cellulose diacetate and poly(vinyl chloride) are not miscible, but cellulose diacetate g‐poly(N‐acetylethylenimine) is miscible with poly(vinyl chloride), the graft chain acting as a “compatibilizer”.
Energy absorbing polymer‐based composites
Authors: Hull Derek
Published: March 2011

The ability of polymer‐based fibre reinforced composite materials to absorb energy when subjected to high stress depends on the micromechanics of deformation and fracture of the individual laminae and the interaction between laminae. The micromechanismsdepend on the properties of the matrix, fibres and fibre‐matrix interface. The capacity of material to absorb energy is important in many applications and particular reference is made to the response of structures to impact.
Ferroelectric polymers and applications
Authors: Hicheron François
Published: March 2011

This paper reviews the general features of ferroelectricity in polyvinylidene fluoride and related polymers; ferroelectricity is shown as the origin of piezoelectricity, pyroelectricity and high dielectric permittivity. Preparation technologies are discussed, and applications are presented, with special attention to capacitor dielectrics and piezoelectric transducers.
Stiff chain persistence lengths in liquid crystalline copolyesters
Authors: Blackwell John , Biswas Amit
Published: March 2011

This paper describes a continuation of our X‐ray diffraction work on the structure of the mesomorphic copolyesters prepared from p‐hydroxybenzoic acid (HBA) and 2‐hydroxy‐6‐naphthoic acid (HNA). The X‐ray patterns of meltspun fibers of these copolymers show a series of aperiodic meridional maxima, and these are predicted by a model consisting of stiff extended chains of completely random copolymer sequence. The calculated intensity data are independent of the chain length for the model, except that the width of the peak at d≃2.1Å decreases with increasing chain length. For 58/42 copoly(HBA/HNA) the best agreement obtained is for a chain length of 11 monomers, and this corresponds to a correlation or persistence length for the stiff chain conformation in the solid state. This effect has been modeled for an infinite chain by deriving experimental monomer length distribution functions, from a survey of the conformations of models of typical random chain sequences. The distribution function is then incorporated into the intensity calculations and leads to prediction of peak widths that are comparable to those observed.
Solid state polymerization of new polyesters containing diacetylenic groups
Authors: Lescano G. R. , Rau N. O. , Schulz R. C.
Published: March 2011

Synthesis and properties of some new polyesters of 10, 12‐docosadiyn‐1, 22‐diol are described. The diyn‐polyesters as films became coloured polydiacetylenic films on exposure to UV radiation and their properties were studied.
Synthesis and thermal behaviour of polybutadiene resins containing acetylene groups in the side chains
Authors: Strumia M. , Bertorello H.
Published: March 2011

Two resins were synthesized containing triple bonds in the side chains. The polymers were characterized by IR and NMR spectroscopy. DSC and thermal decomposition temperatures were determined. These resins show high thermal stability.
Ring‐chain competition kinetic models for linear and nonlinear step‐reaction copolymerizations
Authors: Sarmoria Claudia , Vallés Enrique , Miller Douglas R.
Published: March 2011

Mathematical models of kinetically controlled random copolymerizations with intramolecular reactions have been developed for A2 + B2 and A3 + B2 type reactions, in which the B2 monomer is long and flexible enough to have a Gaussian end‐to‐end distance. Concentrations of different molecular species are calculated, as well as weight‐average molecular weight, gel point and various network parameters. The calculations show the influence of the molecular weight and the concentration of reactants on the amount of intramolecular reaction. The results indicate that the main deviations from ideality are due to the smaller rings.
Newer concepts on the acid catalyzed degradation of cellulose according to kinetic investigations in the high, medium and low molecular weight range
Authors: Marx‐Figini M.
Published: March 2011

A survey is given on recent kinetic investigations on the acid catalyzed degradation of cotton cellulose covering the high, medium and low molecular weight range. As it is revealed, there can be distinguished four subsequent particular stages according to the molecular weight range in which the degradation takes place. Possible interpretations of this phenomenon are discussed taking into account, besides of the kinetic data, the behaviour with time of degradation of the molecular weight distribution, the degree of substitution arising through nitration, and the portion of material dissolved in the acid medium.
The amylose triiodide‐iodine complex: Its dependence with the degree of polymerization
Authors: Benegas Julio C. , Ripoll Daniel , Reyes Eduardo , Cesaro Attilio
Published: March 2011

An extension of the Statistical‐Mechanics model for the inclusion complex of amylose with iodine is developed to take into account the influence of the degree of polymerization (x) of the polysaccharide. Good agreetment is found with the experimental data, in particular the iodine binding capacity (IBC) vs x is well reproduced by the model.
X‐ray studies on phospholipid bilayers. VI. Comparative hydration effects on oriented films
Authors: Suwalsky Mario , Tapia Jaime , Knight Elizabeth , Duk Leonora , Seguel Carmen G. , Neira Fernando
Published: March 2011

Oriented films of three diacylphosphatidylethanolamines containing 12, 14 and 16 methylene groups in their hydrocarbon chains and one 14 carbon chain lecithin were studied by X‐ray fiber diffraction. Their molecular conformations, packing arrangement, crystallographic and physico‐chemical parameters as a function of hydration were determined. Basically the four phospholipids exhibit a common bilayer structure. However, they also present some interesting differences which might be relevant to their biological functions.
Morphology of integral (structural) polymer foams
Authors: Shutov Fyodor A.
Published: March 2011

The survey deals with the fundamental morphological parameters of integral (structural) polymer foams, which have a specific structure: a cellular core that gradually turns into a solid skin. Attempts are made to evaluate the effect and the contribution of the main parameters (the core, the skin, and the intermediate zone) on the strength properties of these foams. Further problems in the morphology of integral foams are discussed.
Pressure crystallized and solid‐state extruded poly ‐ ethylene. Precision determination of lattice parameters
Authors: De Micheli R. E. , Vidal H. M. , Macchi E. M.
Published: March 2011

Precision determination of high density polyethylene unit‐cell dimensions are reported. The crystallographic analysis was carried out on pressure crystallized and subsequently solid‐state extruded samples respectively, by means of x‐ray photographic and diffractometric procedures. In all cases the crystal data was derived from a large number of independent reflections. It was shown that the unit‐cell dimensions and the corresponding crystallographic densities of all the specimens are invariant with respect to either crystallization pressure or nominal draw ratio. The effects of deformation on macroscopic density are attributed, therefore, to changes of the degree of crystallinity and to an increase of the density of the amorphous phase. This interpretation is consistent with the experimental data in the framework of the two‐phase model of polymer morphology.
Absolute size exclusion chromatography. Part 2. Calculation of molecular weight averages
Authors: Sorokin Isidoro H. , Andreetta Héctor A. , Figini Rubén V.
Published: March 2011

An absolute method to obtain molecular weight averages is theoretically proved and experimentally applied to size exclusion chromatographic data. The method is based on stoichiometric relationships and uses labelled polymer molecules.
Optimization of continuous polymerization reactors: Start‐up and change of specification
Authors: Farber Jorge N. , Laurence Robert L.
Published: March 2011

Optimal policies for the control of large disturbances (start up and change of specification problems) in continuous polymerization reactors are determined numerically and compared. Several algorithms are implemented for the solution of two‐point boundary value problems characterized by stiff systems and singular controls. The performance of different policies and solution methods is evaluated.
Complexes of Lewis acids in the cationic polymerization of olefins
Authors: Halaška V. , Marek M. , Pecka J.
Published: March 2011

Findings concerning the origin of electron donor‐acceptor complexes between olefinic hydrocarbons and chosen Lewis acids supplemented by new results are summarized. The important characteristics reported here are stoichiometric ratios of complex formation determined by the variation and titration methods, equilibrium constants and the thermodynamic parameters AG, AH and AS derived from them. Attention has been devoted to the characterization of frontier orbitals of olefins and Lewis acids using ionization potentials, half‐wave polarographic oxidation potentials, electron affinities and half‐wave polarographic reduction potentials. The aim consists in a quantitative characterization of redox processes which occur in elemental initiation reactions. The final evaluation of the data obtained has confirmed that the complexes involved in this case are weak and behave in accordance with the Mulliken theory.
Living cationic polymerization of vinyl monomers: Mechanism and synthesis of new polymers
Authors: Sawamoto Mitsuo , Higashimura Toshinobu
Published: March 2011

This paper reviews the recent progress in our research on the living cationic polymerization of vinyl compounds by the hydrogen iodide/iodine (HI/I2) initiating system, with emphasis on its scope, mechanism, and applications to new polymer synthesis. The scope of the living cationic polymerization has been expanded to include vinyl ethers, propenyl ethers, unsaturated cyclic ethers, and styrene derivatives as monomers. The initiation/propagation mechanism was discussed on the basis of recent direct analysis on the living system by NMR and UV/visible spectroscopy. The proposed mechanism involves a quantitative formation of Hl‐vinyl ether adduct [CH3‐CH(OR)‐I; l] that is by itself incapable of initiating polymerization. In the presence of iodine, however, the CH‐I bond of l is electrophilically activated by iodine and living propagation occurs via the insertion of vinyl ether to the activated CH‐I bond. Such living polymerizations were found to proceed in not only nonpolar but polar solvents (CH2Cl2) as well. Quenching the living end with amines gave polymers capped with an amino group that in turn enabled us to determine the living end concentration. Applications of the HI/I2‐initiated living process to the synthesis of new bifunctional and block polymers were also described.
Cationic polymerization of vinyl ethers as synthetic path to diphylic polymers and potential complexants
Authors: Skorokhodov Sergei S.
Published: March 2011

The polymers of universal solubility like dimethyl ether of ethylene glycol and dioxane are synthesised by cationic polymerization of cis‐1,2‐dimethoxyethylene and p‐dioxene. Some specific features of polymerization, going on long‐lived active centers, are observed. In the case of polymerization of cis‐1,2‐dimethoxyethylene, conducted under usual conditions, the possibility of obtaining polymers with molecular weights as high as 106 and M̄w/M̄N<1.5 is shown. Improved procedures of cyclopolymerization of divinyl ethers of mono‐, di‐, and triethylene glycols are described. Some solution properties of polymers obtained, including conformational transitions and metal ion complexing, are discussed.
Coordination polymerization of ω‐alkenoates and ω‐epoxyalkanoates
Authors: Liping Hu , Vogl Otto
Published: March 2011

As functional polymers have become more and more used, the need for a general synthesis of addition polymers with functional groups became greatly important. We have achieved the polymerization of ω‐alkenoates with coordination initiators of the Ziegler‐Natta initiation type using titanium trichloride‐based transition metal initiators modified with dialkylaluminum chloride. To accomplish this polymerization required that the ω‐alkenoates be precomplexed with dialkylaluminum chloride. High molecular weight homopolymers and copolymers with olefins have been obtained. The polymerization of ω‐epoxyalkanoates with coordinative anionic polymerization systems based on triethylaluminum/water/acetylacetone (1.0/0.5/1.0) has also been accomplished. Homo‐ and copolymers of high molecular weight and of relatively narrow molecular weight distribution have been prepared. All polymers and copolymers of functional olefins and epoxides have been characterized and the study of the reactivity of the functional groups attached via a flexible spacer to the polymer main chain has been started. Special attention was given to the classical cationic copolymerization of trioxane with derivatives of ω‐epoxyundecanoate to prepare novel functional polyoxymethylenes of potential commercial interest.
Olefinpolymerization with highly active soluble zirconium compounds using aluminoxane as co‐catalyst
Authors: Kaminsky Walter , Külper Klaus , Niedoba Stefan
Published: March 2011

The homogeneous Ziegler‐Natta–catalysts, consisting of a zirconocene compound and methyl‐aluminoxane, lead to extremely high polymerization activities. With bis(cyclopentadienyl)zirconium dichloride pure atactic polypropylene and polyethylene with activities up to 30.106 g PE/g Zr·h are formed. The higher the degree of oligomerization of the aluminoxane the more active are the catalysts. The density of polyethylene (LLDPE) can be lowered by using 1‐butene or 1‐hexene as comonomers. Incorporation of dienes gives EPDM‐elastomers. Highly isotactic polypropylene can be prepared by using chiral rac‐ethylene bis–(tetrahydroindenyl) zirconium dichloride together with methylaluminoxane as cocatalyst. The toluene soluble part here consists of less than 0.2 weight percent. After resolution of this racemate it is also possible to produce optically active polypropylene and polybutene.
Advances in the field of organo‐element polymers
Authors: Korshak V. V. , Kozyreva N. M.
Published: March 2011

Organo‐element polymers are a rapidly developing field of high molecular weight compounds. As A.N. Nesmeyanov points out, the organo‐element polymer chemistry is the science lying between inorganic and organic chemistry, that is undoubtedly its positive factor, because this allows to prepare polymeric compounds combining positive properties of the compounds of these two fields. Due to this, many elements of the Periodic System capable of forming various polymeric compounds are widely investigated, and a number of organo‐element polymers have already found practical application in many fields of modern engineering and national economy. It should be noted that at present already more than 75 elements have been used in synthesis of various high molecular weight organo‐element compounds. Besides carbon, among these compounds hydrogen, oxygen and silicon are remarkable. Other elements only begin their way to the polymer field. The concept of raznozvennost (different‐units structure) is of great importance for studying the synthesis and the properties of these polymers. This concept made it possible to clarify distinguishing role of anomalous units in determining the complex of physico‐chemical properties of high molecular weight organo‐element compounds. It is especially important to emphasize that among factors giving rise to anomalous units causing polymer raznozvennost the presence of stable isotope atoms arranged statistically in polymer macromolecules plays an essential role. The lecture is a general review of polymers by the groups of the Periodic System. It discusses the methods for synthesis of organo‐element polymers used at the present time as well as perspective development of this field in the future.
Electrical conductivity of partly oxidized aromatic and heteroaromatic polymers
Authors: Koßmehl Gerhard
Published: March 2011

The electrical conductivity of aromatic and heteroaromatic polymers as well as polymers with aromatic, heteroaromatic and vinylene units in the main chain, can be enhanced by oxidation. In a single electron transfer reaction, a polymer with a salt structure (“doped polymer”) can be formed. Such polymers can also be prepared in a one‐step reaction from low‐molecular weight compounds by oxidants, as well as by electrochemical reaction. Electrochemically produced samples have higher electrical conductivities (as high as 6298K = 0,5 Ω−1 · cm−1) than samples made by chemical oxidation from the same starting material.
Microphase separation transition in block copolymer melts
Authors: Hewel M. , Ruland W.
Published: March 2011

The microphase separation transition (MST) in block copolymer melts has been studied using synchrotron SAXS. The results indicate that the MST occurs in the range of molecular weights and Flory‐Huggins interaction parameters x predicted by the theory of Leibler (Ref. 5). Studies of the MST as a function of molecular weight for constant composition can be used to determine the temperature dependence of x. The observed change of macrolattice constants with temperature is somewhat different from theoretically predicted values.
Solvent modified unperturbed dimensions of macromolecules ‐ their determination via NMR ‐ data and their relevance ‐
Authors: Cantow Hans‐Joachim , Pfannemüller Beate
Published: March 2011

Temperature dependent unperturbed and solvent modified unperturbed dimensions of macromolecules are derived, in a first order approximation, from NMR‐data determined on low‐molecular‐weight analogs in the respective milieu. Because the long range interactions ‐ excluded volume and polymer ‐ polymer interaction ‐ are absent in the conformational balance of those models, the macrodimensions derived in this way are the unperturbed ones, with and without the influence of specific solvent action. Studies on head‐to‐head vinyl polymers are reported. It is demonstrated that the unperturbed dimensions in virtually non‐interacting solvents,o, may exceed those in thermodynamically good ones, s, as a consequence of differing conformational balance at segmental level.

It is pointed out that those temperature and solvent dependent unperturbed dimensions are effective also in polymer solutions, as long as the molecular weight of the polymer is not exceeding the critical length necessary for occurrence of long range interactions.

Capabilities in analyzing the conformational balance in plasticized systems and in compatible polymer blends are discussed. Here the conformation of the second component may be studied in parallel, as a consequence of similar concentrations of both partners in the system.

θ‐dimensions depend on the type of the pseudoideal solvent. This effect is discussed on the base of NMR studies on the unperturbed conformations at segmental level in the respective θ‐ milieu.
Deuteron NMR investigations of structure and dynamics in solid polymers, liquid crystalline polymers and polymer model membranes
Authors: Spiess H. W.
Published: March 2011

Pulsed deuteron NMR offers unique possibilities for studying molecular order and dynamics in polymers. The different techniques employed in this area and the results obtained so far are briefly reviewed. Current developments involving two‐dimensional NMR are also outlined.
Spectral quality enhancement as an aid to polymer characterisation
Authors: Maddams William F.
Published: March 2011

The limit to the information on the microstructure of polymers that may be obtained from their vibrational spectra is often set by overlapping bands, markedly broader than the spectrometer resolution. Following the initial pioneering work of Pohl and Hummel, using a simple curve fitting technique, mathematical methods of spectral quality enhancement have progressed very considerably. These methods are reviewed critically and new results are presented. The desirability of imposing some parameter constraints in curve fitting is demonstrated, and this has led to the development of methods for peak narrowing, as an aid to peak finding. The two important approaches, derivative spectroscopy and Fourier selfdeconvolution (FSD), are discussed in terms of their application to the complex of overlapping bands in the v(C‐Cl) region of the infrared spectrum of poly(vinyl chloride). A development of the FSD method termed Fourier band isolation, is described and preliminary results indicate that it has considerable promise. The maximum entropy method is discussed briefly.
Polymer coatings on steel substrates: An infrared spectroscopic study of temperature effects
Authors: Barbour R. L. , Mooney J. R. , Mehicic M. , Weinert R. J. , Benton K. C. , Grasselli J. G.
Published: March 2011

Polymer coatings on steel substrates were analyzed by reflectance/absorbance infrared spectroscopy. Initial studies were performed ex‐situ on samples which had been cured at a variety of temperatures on two different substrates. Further studies were done in‐situ under both air and nitrogen atmospheres. The two substrates studied were untreated cold‐rolled steel and cold‐rolled steel with a conversion coating of zinc phosphate. Changes in the spectra of the phosphate conversion layer correlated well with anti‐corrosion properties. Mechanisms of degradation and cure could be determined from the in‐situ studies (1).
Über die spektroskopische bestimmung der spezifischen volumina von amorphem (va) und kristallinem (vc) polyethylenterephthalat
Authors: Simak P.
Published: March 2011

The intensity of the IR‐absorption bands of PET, which depends on the chain conformation (crystallinity), has been correlated with the specific volume of the samples produced under different conditions. It has been found that the absorption data of the ‐0‐CH2‐CH2‐0‐groups, discussed in the literature, leads to wrong vc‐ and va‐values. From our FTIR measurements of PET we obtained the spec. volume vc=ca. 0,66 cm3/g and va=0, 747 cm3/g. The amount of the trans‐conformation in the amorphous (for a well quenched sample) PET is about 12 ‐ 15%. The absorption band at 990cm−1 is not due to the sharp folds in PET.
Infrarot‐mikrospektroskopie an polymeren
Authors: Peitscher Günter W.
Published: March 2011

IR microspectroscopy allows the identification and even quantitative analysis of tiny objects down to nanograms. A typical example is the investigation of specks or fish eyes in plastics. Other applications include the determination of local concentration changes of plasticizer or the oxygen uptake during aging. Such microinvestigations require sophisticated preparation techniques and specially equipped high‐performance spectrometers. Some practical examples and results are presented; they demonstrate the use of micro‐KBr, microtome, microsheet, and micropyrolysis techniques.
Molecular analysis of the interface of poly(ether‐ether‐ketone) and the basal plane of graphite single crystals
Authors: Nguyen Huy X. , Ishida Hatsuo
Published: March 2011

The interfacial interaction of the basal plane of graphite single crystals and poly(aryl‐ether‐etherketone) (PEEK) was investigated using Fourier transform infrared reflection‐absorption spectroscopy (FT‐IR‐RAS). PEEK melt‐quenched on the basal plane of a graphite single crystal does not show preferential orientation. However, upon annealing, the polymer chains crystallize perpendicularly to the basal plane of the graphite single crystal. The rate of this surface‐induced orientation during crystallization is found to be dependent on the film thickness. These results were verified by using model compounds of PEEK and by calculations based on optical theories.
Rheo‐optical fourier‐transform infrared spectroscopy of polymers 12. Variable temperature studies of strain‐induced crystallization in sulfur‐crosslinked natural rubber
Authors: Siesler Heinz W.
Published: March 2011

Rheo‐optical Fourier‐Transform infrared (FTIR) spectroscopy has been applied to investigate the onset, progress and decay of strain‐induced crystallization during loading‐unloading cycles of sulfur‐crosslinked natural rubber in the temperature range from 300 K to 423 K. The technique allows to detect crystallization online to the mechanical treatment upto 383 K.
Solid state 13‐C NMR spectroscopy with special reference to proteins and their derivatives. A comparison with vibrational spectroscopic methods
Authors: Martinmaa Jukka , Lindberg J. Johan , Maunu Sirkka‐Liisa
Published: March 2011

Possible applications of solid‐state NMR in studies on polypeptides and proteins are presented. Several examples of 13‐C CP/MAS NMR spectra are discussed in relation to model compounds and polypeptides from various sources. A comparison is made with vibrational spectroscopic methods. It is concluded that the CP/MAS NMR method is especially useful in elucidating secondary structures in the unperturbed state, and, thus, may also be useful in the study of various conditions involving the disturbance of biochemical equilibria (e.g. the skin disease psoriasis and β‐fibrilloses). In these cases the NMR method is more elucidative than vibrational spectroscopy. However, owing to the fact that multiple spectral scans must be performed, it is very time consuming. It therefore appears that high resolution Fourier transform infra‐red spectroscopy is a complementary method, but not as informative regarding structural details in secondary structures. Combining both methods together provides a powerful tool for structure analysis.
500 MHz 1H NMR studies on the configuration and conformation in the piezoelectric copolymer of vinylidene cyanide and vinyl acetate
Authors: Jo Yong Sung , Inoue Yoshio , Chūjô Riichirô , Miyata Seizo
Published: March 2011

The 500‐MHz 1H NMR spectrum of vinylidene cyanide‐vinyl acetate copolymer, P(VDCN/VAc), provided detailed information concerning the configuration (ϵ‐tacticity) and conformations. The 1H NMR data also demonstrated that P(VDCN/VAc) is an equimolar and highly alternating copolymer without the regioirregular defects (complete head‐to‐tail arrangement), which is in good agreement with the previous C‐13 NMR result. The calculated ϵ‐isotacticity σ(ϵ) is equal to 0.5, suggesting that P(VDCN/VAc) is completely atactic. Due to this nonstereoregular structure, P(VDCN/VAc) in the bulk shows the amorphous phase by X‐ray and DSC measurements. Making use of 1H‐homodecoupling, the splittings due to ϵ‐tacticity as well as proton‐proton spin coupling could be separately assigned. From the vicinal coupling constants, J(AX) and J(BX), obtained in methylene proton resonance, conformer populations around H(A)H(B)C‐CH(X)‐CH(A ‘)H(B’ ), were calculated. The conformation of P(VDCN/VAc) in DMF solution consists of only TG and TT, forming not a random coil structure but a helical structure with a large radius of curvature.
Polarized fluorescence spectra of poly(ethylene terephthalate) films
Authors: Hennecke Manfred , Fuhrmann Jürgen
Published: March 2011

The polarized excitation and fluorescence spectra of lowcrystalline, isotropic poly(ethylene terephthalate) (PET) film samples were measured in the glassy state at room temperature. Whereas the emission anisotropy r0 of the excitation spectrum, recorded at the fluorescence maximum, changes sharply from 0.35 to 0 with decreasing wavelength in the region around 317 nm, the polarization of the fluorescence spectrum of PET is independent of wavelength. The fluorescence polarization of PET remains constant, if the temperature is increased up to 22 °C above Tg until the light scattering due to the crystallization causes complete depolarization.

The photophysical behaviour supports the existence of a dilute solution of groundstate ‐ stable sandwich dimers in the non‐crystalline regions of PET.
The composition of an antioxidant obtained by styrylation of phenol
Authors: Milina R. , Laufenberg G. , Budzikiewicz H.
Published: March 2011

The composition of an antioxidant obtained by styrylation of phenol under the catalysis of oxalic acid has been determined by gas chromatography/mass spectrometry and other mass spectroscopic techniques as well as by comparison with authentic samples. It is shown that in addition to the products obtained by styrene addition to the ortho and/or para position of phenol, mentioned in the literature, oligostyrenes, compounds containing more than three styrene units per phenol molecule, and reaction products with urotropin (hexamethylenetetramine) ‐ added as a quencher ‐ are contained in the mixture.
Plasma treatment of the inner surface of polymer tubes for the improvement of their anticoagulant properties
Authors: Jansen B. , Steinhauser H. , Prohaska W.
Published: March 2011

Small‐diameter tubings from chlorinated polyethylene, polyetherurethane and silicone rubber were treated in a special plasma reactor using 1 kHz audiofrequency with rectangular characteristics with the aim to modify the inner surface of the tubings. Non‐polymerizable gases like air, N2, NH3 and CO2 were used as plasma gases to create suitable functional groups on the surfaces; hydrophilic monomers like N‐methyl‐N‐vinylacetamide and vinyl acetate were used to obtain thin grafted homogeneous surface layers. Surface analysis of the modified tubings was generally conducted by contact angle measurements, and ATR‐spectroscopy in the case of grafted materials. As a first test of the blood‐compatibility the activated and non‐activated partial thromboplastin time of human plasma exposed to the modified polymer tubings was determined.
Molecular level approach to the origin of the steric control in organozinc catalyst for oxirane polymerization
Authors: Tsuruta Teiji
Published: March 2011

A new type of single crystals was formed by a reaction between diethylzinc and DL‐1‐methoxy‐2‐propanol. The constituent unit of this single crystal was shown to be a two to two complex of zinc dialkoxide and ethylzinc alkoxide, [MeOCH2 CH(Me)OZnOCH(Me)CH2 OMe]2 · [EtZnOCH(Me)CH2 OMe]2, which has a chair type structure. The two to two complex was found to exhibit higher activity and stereospecificity in the PO polymerization compared with those of the one to six complex which were reported previously. Molecular level elucidation was made on the basis of NMR studies for polymerization system with a partly deuterated two to two complex as initiator. The excellent stereospecificity in isotactic propagation was ascribed to the highly chiral hole around the active site of the chair type complex. Another series of study revealed chemical behavior of cyclohexene oxide (CHO), which is different from that of PO, toward several organozinc compounds. The two to two complex was the only catalyst which showed high activity for both MO and CHO polymerizations. Three samples (I), (II) and (III) of poly‐(CHO) were prepared with Et2Zn, EtZnOR and the two to two complex, respectively. After careful examinations of each of the three samples, it was concluded that most parts of the main chain of polymer (III) molecule were composed of syndiotactic triad, SS‐RR‐SS(or RR‐SS‐RR), while polymer (I) and (II) molecules contained syndiotactic and heterotactic triads in comparative amounts. In the CHO polymerization, the chiral hole of the two to two complex cannot recognize the mode of orientation of the achiral monomer, and the complex seems to serve as a simple bulky group which facilitates syndiotactic addition of CHO monomer molecule to the active site, strong steric effects being exerted from the penultimate unit of the growing chain during the propagation stage.
Kinetics, mechanisms, and synthesis studies of difunctional aminopropyl terminated polydimethylsiloxane oligomers
Authors: McGrath J. E. , Sormani P. M. , Elsbernd C. S. , Kilic S.
Published: March 2011

The anionic ring opening equilibration polymerization of octamethylcyclotetrasiloxane (D4) initiated with siloxanolates in the presence of 1,3‐bis(3‐aminopropyl)tetramethyldisiloxane (DSX) was investigated. The disiloxane serves as an effective chain transfer agent and source of aminopropyl functionality. Techniques for following the polymerization utilizing gas chromatography and high pressure liquid chromatography (HPLC) were developed and verified to be comparable with alternate methods published in the literature. In these polymerizations, it was concluded that the quaternary siloxanolate led to much more rapid polymerizations than the corresponding potassium based initiators. In all cases, the cyclic tetramer disappeared more rapidly than the disiloxane. However, this does not limit the utilization of the DSX for the synthesis of controlled molecular weight, difunctional species. Polar impurities, such as water in the disiloxane, were shown to influence the reactivity in these systems, especially at relatively low initiator concentrations. The work is continuing and many issues are being addressed, currently in a more quantitative fashion using the analytical procedures developed in the current study.
Free radical ring‐opening polymerization and its use to make biodegradable polymers and functionally terminated oligomers
Authors: Bailey William J. , Chen Paul Y. , Chen Shuh‐Cheng , Chiao Wen‐Bin , Endo Takeshi , Gapud Benjamin , Kuruganti Vijaya , Lin Yin‐Nian , Ni Zhende , Pan Cai‐Yuan , Shaffer Scott E. , Sidney Luann , Wu Shang‐Ren , Yamamoto Noboru , Yamazaki Noboro , Yonezawa Kazuya , Zhou Lin‐Lin
Published: March 2011

Since a carbon‐oxygen double bond is considerably more stable than a carbon‐carbon double bond, it has been possible to use this driving force to promote free radical ring‐opening polymerization of unsaturated heterocyclic compounds. This process, for the first time, has permitted the introduction of functional groups, such as esters, amides and carbonates, into the backbone of addition polymers. Hydrolysis of the copolymers with common monomers produced oligomers capped with hydroxyl, amino or carboxylic acid groups. The presence of an ester group in a copolymer, such as in a copolymer of ethylene, render the copolymer biodegradable.
NMR spectroscopic investigation on polymerization mechanisms of amino acid NCAS
Authors: Kricheldorf Hans R.
Published: March 2011

Polymerizations of α‐aminoacid N‐carboxyanhydrides (α‐NCAs) can be initiated by nucleophilic or basic reagents. Depending on the nature of the reagent, nucleophilic attack at the carbonyl group C‐5 or deprotonation of the N‐H group may be the first reaction step. 1H NMR spectroscopy is best suited to detect incorporation of initiator fragments. In the case of primary aliphatic amines quantitative endgroup analyses may even allow the calculation of the average degree of polymerization (DP). In the case of base‐initiated polymerization the formation of N‐acyl‐NCA endgroups or the incorporation of the basic initiator is detectable. Furthermore, the role of electrophilic co‐catalysts, such as isocyanates or N‐acyl‐NCAs, can be elucidated. 13C‐ and 15N NMR spectroscopy are better suited than 1H NMR spectroscopy for stereosequence analyses of poly(D,L‐amino acid)s. The results of both methods agree in that primary amine‐initiated polymerizations of D,L‐NCAs yield nearly random stereosequences. Trialkylamine initiated polymerizations of α‐helix forming D,L‐NCAs favour the formation of isotactic blocks, whereas in the case of non‐helicogenic NCAs (e.g. D,L‐Val‐NCA) syndiotactic blocks are preferentially formed. 15N NMR spectroscopy also enables the sequence analysis of binary copolypeptides, and in favourable cases even ternary copolypeptides can be analyzed. 13C NMR crosspolarization/magic angle spinning (CP/MAS) spectroscopy of solid polypeptides enables the qualitative and quantitative determination of their secondary structure. Such investigations revealed that primary amine and tertiary amine‐initiated polymerizations may yield different ratios of crystallites built up by β‐sheets or α‐helices and thereby bimodal molecular weight distributions (MWDs).
Polymerization of propylene oxide by activated monomer mechanism. Suppression of macrocyclics formation
Authors: Wojtania Melania , Kubisa Przemyslaw , Penczek Stanislaw
Published: March 2011

Evidence for the activated monomer (AM) mechanism operating in the polymerization of propylene oxide (PO) initiated with HBF4 is presented. The contribution of AM route of propagation is the highest and formation of cyclic oligomers mostly suppressed when monomer concentration is low enough. This was achieved by slowly adding PO to the reaction mixture, as previously proposed on the basis of kinetic considerations.
Cyclic oligomers content in anionic poly (ϵ‐caprolactam)
Authors: Biagini Emilio , Costa Giovanna , Russo Saverio , Turturro Antonio , Riva Fernando , Rovida Camillo
Published: March 2011

The influence of initiator and activator concentrations on the anionic polymerization of ϵ‐caprolactam and, in particular, on the methanol – extractable fraction of the final polymer has been widely studied. Due to the increasing interest of this polymerization in the field of reaction injection molding (RIM) technology, a thorough investigation has been also carried out to find the best experimental conditions for this reaction in the mold. The effect of postpolymerization annealing on the overall amount of low‐molecular mass substances, among which cyclic oligomers, has been evaluated. Thermal properties as well as crystallinity of the resultant materials have been examined. A comparison with literature data is given; the suggested correlation between the amount of the oligomeric fraction and the molecular arrangement of the polymer in the solid state is discussed.
Effect of ring‐size in cationic polymerization of cyclosiloxanes. D6‐polymerization initiated by trifluoromethanesulfonic acid
Authors: Gobin C. , Masure M. , Sauvet G. , Sigwalt P.
Published: March 2011

Cationic polymerization of dodecamethylcyclohexasiloxane (D6) initiated with triflic acid at 20°C in CH2Cl2 shows a stationary concentration of active centres. This has permitted the measurement of kpx [Pn*] for the various Dx cyclics, and of the ratios of propagation rate constants kp5/kp4 ∼ 2,2 ± 0,4 and kp6/kp4 ∼ 5,8 ± 1,2. On the other hand, the back‐biting rate constants were not significantly different for various cyclics formation (k4 ∼ k5 ∼ k6). These values have been compared with those obtained from D4 and D5 polymerizations.
Anionic polymerization of cyclosiloxanes with cryptates as counterions: New results
Authors: Hubert S. , Hémery P. , Boileau S.
Published: March 2011

A kinetic study of the anionic polymerization of hexamethylcyclotrisiloxane ((CH3)2SiO)3 (D3) was carried out in toluene with the cryptate Li+ + [211] as a counterion. The kinetic order with respect to the living end concentration was found to be equal to 1, and the propagation rate constant relative to cryptated ion pairs was determined at several temperatures between −20 and +20°C. The corresponding activation parameters were calculated : Ep = 9.8 kcal.mol−1 and Δ S°t = −20 cal.mol.−1K−1.

The reaction of 1,3,5,7‐tetramethyl‐1,3,5,7‐tetravinylcyclotetra‐siloxane ((CH3)(CH2=CH)SiO)4 (D4*) was studied under the same conditions, the reactivity towards silanolate active centers was shown to be very close to that of D3. The rate constants of propagation and depropagation of D4* and of larger cycles D5* and D6* were determined from polymerization experiments on D4*. The propagation rate constants were found to be nearly the same for D4* and D5* : 1.2–1.31.mol−1. s−1, D6* being the less reactive monomer : 0.41.mol−1. s−1. The differences observed in equilibrium constants of the cycles are essentially due to the rate constants of their formation which were found to be 0.42, 0.23, and 0.006 s−1 for D4*, D5* and D6*, respectively.
The cationic grafting of cellulose with 2‐methyl‐2‐oxazoline
Authors: Cheradame H. , Upe Tadjang Ambo , Gandini A.
Published: March 2011

Grafting of cellulosic materials, including bleached kraft pulp, has been achieved by electrophilic polymerization. The process involves two steps, (i) the tosylation of the cellulosic substrate by reaction with tosyl chloride, (ii) polymerization of 2‐methyl‐2‐oxazoline in contact with the esterified cellulose. The grafting efficiency was generally in the range of 20 to 50 %, which was attributed to the occurrence of a transfer reaction specific to the cellulose.
The synthesis of polyamine networks using cationic living poly(1‐tert‐butylaziridine)
Authors: van De Velde M. , Goethals E.J.
Published: March 2011

Polyamine networks have been synthesized by end‐linking bifunctional living poly‐TBA with polyfunctional nucleophilic reagents. The bifunctional living poly‐TBA was obtained by polymerization of TBA initiated by low molecular weight bifunctional living poly(tetrahydrofuran). The swelling degrees of the networks in several solvents are reported.
Synthesis of stereoregular poly(alkyl malolactonates)
Authors: Arnold Steven C. , Lenz Robert W.
Published: March 2011

Optically pure methyl, ethyl, isopropyl, and benzyl (R)‐malolactonate were prepared from (S)‐(‐)‐malic acid and were polymerized in the bulk with tetraethylammonium benzoate as the initiator to yield high‐molecular‐weight, crystalline polymers. The optical purity of methyl and benzyl malolactonate was determined by 1H NMR spectroscopy of the β‐lactone complexed with a chiral europium shift reagent. Enantiomeric excesses of 100% were found (the experimental error was 3%). Optically active poly(β‐malic acid) was obtained from optically active poly[benzyl (S)‐malate] by catalytic hydrogenolysis of the pendent benzyl esters. Ethyl and benzyl (R)‐malolactonate were also copolymerized, and the benzyl esters of the resulting copolymer were converted into carboxylic acid units by hydrogenolysis.
Benzyl esters of optically active malic acid stereocopolymers as obtained by ring‐opening polymerization of (R)‐(+) and (S)‐(‐)‐benzyl malolactonates
Authors: Guerin Ph. , Francillette J. , Braud C. , Vert M.
Published: March 2011

(R)‐(+) and (S)‐(‐)‐benzyl malolactonates were copolymerized anionically by using triethylamine and aluminum porphyrin as initiators. Configurational composition of resulting optically active poly(benzyl β‐malate) stereocopolymers depends on the enantiomeric purity in the monomer feed. Stereochemistry during the multistep synthesis starting from aspartic acid enantiomers used as precursors is discussed. It is shown that natural L(+)‐aspartic acid yields (‐)‐poly(benzyl β‐malate) which degrades to L(‐)‐malic acid in alkaline aqueous medium. Configurational structures were investigated by 13C NMR (75.47 MHz) and splittings of stereosensitive resonances are discussed in terms of stereosequence distributions. Results show that stereocopolymerization proceeds through random addition of chiral repeating units according to Bernoullian statistics. In order to exemplify the effect of enantiomeric composition on physical properties, thermal characteristics have been investigated by DSC for the whole series of stereocopolymers. Samples with more than 70% (S) or (R)‐units are semicrystalline. Melting temperature and crystallinity increase with stereoregularity.
Aspects of epoxy resin curing reactions
Authors: Barton John M.
Published: March 2011

The progress that has been made in establishing the mechanism of the curing reaction between epoxides and amines, particularly through the use of calorimetric methods (DSC), is discussed. A novel application of tritium‐labelled compounds to the study of the reaction of epoxides with imidazoles is also presented. The radiochemical method has produced an enhanced understanding of the reaction mechanism and has given kinetic data in good agreement with DSC measurements.
Network structure and plasticization of epoxy‐based resins
Authors: Apicella A. , Nicolais L.
Published: March 2011

The sorption behaviour of water molecules in epoxy‐based thermosetting networks is discussed and related to the modifications of their properties. The hypothesized sorption modes and the corresponding mechanisms of plasticization are discussed on the basis of experimental vapor and liquid sorption tests, differential scanning calorimetry (DSC), thermomechanical analysis (TMA) studies, and dynamic mechanical analyses.

Three modes of moisture sorption are assumed: increase in the free volume of the system, hydrogen bonding onto hydrophilic groups present in the network and adsorption onto the surfaces of “holes” which define the excess free volume of the glassy structure. The less stiff Diglycidyl ether of bisphenol‐A (DGEBA) systems have no appreciable sorption via hydrogen bonding, but rather most of the moisture absorbed is due to the free volume increase and adsorption in the “holes”. On the other hand, the stiffer Tetraglycidyl Diaminodiphenyl Methane (TGDDM) systems absorb more moisture through significant hydrogen bonding rather than by the free volume increase. High plasticizations, evident as Tg depressions by 30 to 80°C, are possible being experimentally observed for the stiffer TGDDM resins.

Relationships derived from the free volume theory or the classical thermodynamic treatment may be used to describe the dependence of Tg on the composition of miscible blends.
New aspects on intrinsically conducting organic systems and their synthesis
Authors: Naarmann Herbert
Published: March 2011

Organic polymer films with intrinsic conductivity can be produced in a continuous process directly from the monomers by anodic oxidation.

This paper describes the synthesis, the scope available for variation in the process, and the main properties of the new polymers.

Electrochemical oxidation, e.g. of pyrrole to polypyrrole, is a new polymerization principle that differs essentially from those adopted for classical plastics, i.e. radical or ionic polymerization and polyaddition or polycondensation techniques.

It is not only the principle underlying the synthesis that differs, and the properties of the new polymers are unusual.