bluuebunny/crossref_metadata_2025 huggingface dataset:
Synthesis of polyvinylamine and polymer analogous reactions
Authors: Fischer Thomas , Heitz Walter
Published: April 2003

Polyvinylamine (PVVAm) was synthesized using the precursor poly(tert‐butyl N‐vinylcarbamate) (PTBNVC). The monomer synthesis was improved, and the control of the molecular weight of the PTBNVC and the PVAm by a transfer reaction with the solvent is demonstrated. TBNVC was radically polymerized. In suspension polymerization molecular weights of 106 g/mol are accessible. Different polymer analogous reactions were carried out. The resulting polymers are methylated polyvinylamine, poly(N‐vinylureas), poly(N‐vinylalkanamides) and PVAm‐adducts with acrylic acid derivatives.
On the intrinsic viscosity of anionic and nonionic rodlike polysaccharide solutions
Authors: Chun Myung‐Suk , Park O Ok
Published: April 2003

The ionic strength dependence of intrinsic viscosity as a function of molecular weight was observed substantially for the anionic xanthan polyelectrolyte, while the intrinsic viscosity of nonionic schizophyllan does not change with ionic strength. Ultrasonic degradation was applied as the best mean of obtaining polymer fractions of different molecular weights. It is true, as expected, that schizophyllan has a more rigid triple helix backbone than that of xanthan. As the molecular weight increases, the extension coefficient ε of the xanthan chain with ionic strength is found empirically to increase by order 1,48 of molecular weight. Using the Yamakawa‐Fujii theory for worm‐like chains, both the persistence length q and the contour length Lc were determined from the best fit of the experimental data of intrinsic viscosity for different ionic strengths to the theoretical curves. The stiffness parameter was established from the ratio of the Kuhn statistical segment length (i. e., twice the persistence length) to the contour length. As the molecular weight decreases, stiff chains of short degraded xanthan become rodlike, while they become gradually worm‐like with increasing molecular weight. It also can be seen that the chain stiffness depends on the ionic strength.
Dielectric properties of poly[bis(trifluoroethoxy)phosphazene] and poly[bis(m‐methylphenoxy)phosphazene]
Authors: Moriya Keiichi , Nishibe Yasushi , Yano Shinichi
Published: April 2003

Dielectric properties of poly[bis(trifluoroethoxy)phosphazene] (PFEP) and poly[bis(m‐methylphenoxy)phosphazene] (PmMPP) were studied in a temperature range from −195 to 120°C and at several frequencies between 0,1 and 100 kHz. In PFEP, two relaxations, an α relaxation above the glass transition temperature (Tg) and a β relaxation below Tg, which are related to a glass‐rubber transition and a local molecular motion of short segments, respectively, were observed. However, PmMPP shows no β relaxation. From the above dielectric results, it was concluded that side groups play an important role in molecular motion of the polyphosphazenes. In PmMPP a γ′ relaxation was found below Tg by immersing the polymers into water. The γ′ relaxation is related to the molecular motin of absorbed water.
The structure of poly(ethylene oxide)‐salt complexes with 13c CPMAS NMR and relaxation studies
Authors: Maunu Sirkka L. , Soljamo Kari , Laanterä Matti , Sundholm Franciska
Published: April 2003

13C cross polarization and magic‐angle spinning (CPMAS) NMR studies were made on poly(ethylene oxide) (PEO) complexed wit LiClO4, NaClO4, BaSCN, Bal2 and Ba(ClO4)2. The proton and carbon spin‐lattice relaxation times in a rotating frame (T1ρH, T1ρC) as well as the rate of cross polarization were measured at room temperature. For Ba(ClO4)2 the measurements were made with different polymer molar masses and salt concentrations. The changes in relaxation behaviour indicate changes in polymer chain mobility as well as strong interaction between ions and PEO chains. The T1ρH and T1ρC decrease with decreasing salt concentration towards the relaxation times of the pure polymer. Nonexponential relaxation behaviour was found for the samples according to the T1ρC and TCH measurements.
Catalytic behavior in the olefin oxidation and characterization of polyacrylonitrile‐palladium complexes
Authors: Jia Cheng‐Guo , Jin Feng‐You , Pan Hui‐Quan , Huang Mei‐Yu , Jiang Ying‐Yan
Published: April 2003

We prepared polyacrylonitrile‐palladium(PAN‐Pd) complexes in which palladium is coordinated with approximately 2 nitrile groups and has a mixed valency (Pd(0) + Pd(I) + Pd(II)). The complexes contain small palladium aggregates (diameter ca. 50 Å) which are rather stable due to the coordination of palladium to the polymer. The PAN‐Pd complexes are highly active and stable catalysts for the oxidation of olefins in the presence of cocatalysts like CuCl2·2H2O. They could be recycled 5 times without loss of activity in the oxidation of 1‐heptene.
Structure analysis of the noncrystalline material in poly(ethylene terephthalate) fibers
Authors: Fu Yigang , Busing William R. , Jin Yimin , Affholter Kathleen A. , Wunderlich Bernhard
Published: April 2003

The structures of the noncrystalline material of four poly(ethylene terephthalate) fiber samples have been studied by analyzing the X‐ray scattering patterns. The noncrystalline scattering patterns of the three semicrystalline fibers are revealed by removal of the crystalline contribution from the diffraction patterns. The crystalline phase diffraction is calculated from a structure model determined by a full‐pattern X‐ray fiber diffraction analysis. The noncrystalline materials is further divided into an amorphous and an oriented, intermediate phase. The azimuthal scattering pattern of the former is isotropic, the latter anisotropic. The intermediate phase does not only show parallel chains along the fiber direction, but a crystal‐like correlation is also possible, primarily in the materials between the oriented, fibrillar crystallites. The growth of the crystalline phase in fibers is intimately coupled to this intermediate phase. Both amount and detailed structure of the intermediate phase depend on the thermal and mechanical history of the fiber. A first discussion is given of the correlation between the three phases derived by X‐ray diffraction and three phases identified earlier by thermal analysis (crystalline, mobile amorphous and rigid amorphous). The mechanical properties of the fibers are seemingly more dependent on the intermediate phase than on the crystalline or amorphous phases.
On the kinetics and initiation mechanism of acrylamide polymerization using the ceric ion/acetoacetanilide system as initiator
Authors: Dong Jian Hua , Qiu Kun Yuan , De Feng Xin
Published: April 2003

It is found that acetoacetanilide (system. name: N‐phenyl‐3‐oxobutanamide) possesses a very high reactivity towards ceric ions, Ce4+, in initiating the polymerization of vinyl monomers. In the presence of acetoacetanilide, the rate of the acrylamide polymerization is larger by a factor of 30 than the rate of initiating by ceric ions alone. The reaction orders were 0,58, 0,75 and 1,2 with respect to acetoacetanilide, ceric ion and acrylamide concentration, respectively. The activation energy of the acrylamide polymerization initiated by ceric ion/acetoacetanilide is only 12,9 kJ/mol. According to the IR spectrum, fragments of acetoacetanilide are present in the polymer produced by the ceric ion redox initiator comprising acetoacetanilide. The C‐centered and N‐centered primary radicals generated via redox reaction of ceric ion and acetoacetanilide were detected by spin trapping and electron paramagnetic resonance. An initiation mechanism of the ceric ion/acetoacetanilide initiated polymerization is proposed on the basis of experimental results.
Mesogen conformation changes in thermotropic polyesters at phase transitions
Authors: Shilov Sergei , Volchek Boris , Zuev Vyacheslav , Skorokhodov Sergei
Published: April 2003

Mesogen conformations in thermotropic polyesters with alternating mesogens and poly(methylene) spacers were investigated by IR spectroscopy with polarized and unpolarized light. The selective deuteration of terephthaloyl‐bis(p‐oxybenzoate) mesogens gave a possibility of assigning part of the IR bands to terephthalic or to oxybenzoic fragments. It is shown that in the liquid crystalline melt the mesogen conformation is planar, but in the semicrystalline state it is mainly nonplanar. Differences in mesogen conformations of polymers containing an even or an odd number of methylene units in the spacer are detected. Thus, LC ordering seems to affect not only the conformation of the spacer but also the conformation of the mesogen.
The homogeneous photopolymerization of methyl methacrylate by colloidal cadmium sulfide
Authors: Popović Ivanka G. , Katsikas Lynne , Müller Udo , Veličković Jovan S. , Weller Horst
Published: April 2003

A completely new method of initiating the homogeneous radical polymerization of methyl methacrylate in bulk or in solution via the photogeneration of an electron hole pair in colloidal cadmium sulfide is presented. A polymerization mechanism involving an excited cadmium sulfide particle in both the initiation and termination steps is proposed. In the initiation a methyl methacrylate molecule is oxidized by a positive hole photogenerated in a CdS particle, which results in a novel chain‐end structure of the poly(methyl methacrylate) (PMMA). Degradative chain transfer to reduced excited cadmium sulfide particles is responsible for chain termination. Thus, for the first time, a detailed polymerization mechanism in which all states of the polymerization, i.e., initiation, propagation, chain transfer and termination, is presented for the polymerization of vinyl monomers initiated by semiconductors. Thermogravimetry (TG) showed that the newly synthesized PMMA has greatly enhanced thermal stability when compared to normal radically prepared PMMA. In fact, the thermal stability approaches that of anionically prepared PMMA but is experimentally much easier to prepare. This technique enables the homogeneous embedding of CdS particles in a polymer matrix.
Zur kinetik der copolymerisation von methacrylaten mit entkoppelter seitengruppe
Authors: Rübner Joachim , Geßner Uwe , Rodekirch Gerhard , Ruhmann Ralf
Published: April 2003

The copolymerization behavior of methacrylate monomers with several decoupled side groups was studied depending on the structure of the linked mesogen. Some units (NN, CONH) in the mesogen influence the copolymerization reaction in spite of the strong decoupling by a C6‐spacer group and lead to retarding effects and to the preferred insertion of monomers with weaker mesogenic interactions. The liquid‐crystalline behaviour of the copolymers was not affected due to the relatively small differences in the copolymerization parameters.
A mechanistic study of the radical copolymerisation of p‐chlorostyrene with citraconic anhydride via 13C NMR spectroscopy
Authors: Brown Paul G. , Fujimori Kiyohisa
Published: April 2003

The composition and monomer unit sequence distribution of copolymers of p‐chlorostyrene (p‐CST) with citraconic (α‐methylmaleic) anhydride (CA) prepared in methyl ethyl ketone (MEK) at 50,0 ± 0,1°C were determined over a range of comonomer feed mole fractions using 13C NMR spectroscopy. The monomeric units in these copolymers were found to display a mild tendency to alternate, which increased as the mole fraction of CA in the feed increased. The existence of a 1:1 charge‐transfer complex formed between p‐CST and CA in the feed was confirmed via UV spectroscopy and the equilibrium constant for complex formation determined to be 0,10 ± 0,04 L/mol in MEK at ambient temperature. The terminal, penultimate, complex‐participation and complex‐dissociation models were each tested for applicability to the mechanism of copolymerisation for this comonomer system. On the basis of copolymer composition data, the penultimate, complex‐participation and complex‐dissociation models were each found to provide an adequate description of the mechanism of copolymerisation in the comonomer system via non‐linear least squares methods. An analysis of the comonomer unit sequence distributions for these semi‐alternating copolymers and the application of reactivity ratio related test functions to this data allowed applicability of the four models under investigation to be separated more explicitly, with the complex‐dissociation model providing the best fit to the data.
Polyanhydrides, 6. Thermotropic poly(ester anhydride)s derived from 2,5‐bis(alkylthio)terephthalic acids
Authors: Kricheldorf Hans R. , Domschke Angelika
Published: April 2003

2,5‐Bis(alkylthio)terephthalic acids (and their acyl chlorides) were prepared by nucleophilic substitution of diethyl 2,5‐dibromoterephthalate with octane‐, dodecane‐ and hexadecanethiol. The poly(ester anhydrides) were obtained by thermal polycondensation of disubstituted terephthaloyl chlorides with silylated 4‐hydroxybenzoic acid and silylated hydroquinone. The resulting polymers were characterized by elemental analyses, inherent viscosities, differential scanning calorimetry (DSC) and wide‐angle X‐ray scattering (WAXS) measurements, optical microscopy and 13C NMR cross polarization/magic angle spinning (CP/MAS) spectroscopy. These measurements suggest that the disubstituted poly(ester anhydrides) form a sanidic type of layer structure in the solid state. Increasing length of the alkyl substituents favours the formation of ordered paraffin domains between the stacks of the main chains. The stability of these quasicrystalline paraffin domains decreases with increasing mole fraction of the anhydride groups. In contrast to their monosubstituted analogues the disubstituted poly(ester anhydrides) do not form normal nematic melts.
Electron transfer catalyzed by manganese tetratolyl‐prophyrinate across poly(γ‐methyl L‐glutamate) membrane
Authors: Dewa Takehisa , Satoh Mitsuru , Komiyama Jiro , Nango Mamoru , Tsuda Kazuichi
Published: April 2003

A poly(γ‐methyl L‐glutamate) (PMLG) membrane containing manganese tetratolylporphyrinate (MnTTP) was prepared in order to examine the transmembrane electron transfer in a redox system constructed as S2O42−/membrane/Fe(CN)63−. Electron transfer was observed in 0,1 M pH 7,0 imidazole (Im) buffer but not in 0,1 M pH 7,0 phosphate buffer. The apparent transfer rate increased with MnTTP content and also with the Im concentration in the buffer, indicating that electron is transferred by MnTTP, which is coupled with proton transport by Im distributed in the membrane. The transfer catalyzed by MnTTP was more effectively accelerated with Im than with 2‐methylimidazole (2‐Melm) but not at all with 1‐methylimidazole (1‐Melm). This implies that the 1‐N site on the imidazoles as the axial ligand of MnTTP is a crucial position for the mediation of electron transfer between MnTTP's. In the pH range 6,0–8,5 of Im buffer, the electron transfer rate showed a maximum at pH 7,0. This pH dependence is discussed in terms of the concentration and mobility of proton in the membrane.
DSC and 13C NMR studies of ethylene‐propene copolymers prepared by a highly active and stereospecific catalyst
Authors: Zhang Xuequan , Chen Hui , Zhou Zinan , Huang Baotong , Wang Zhanwang , Jiang Ming , Yang Yongran
Published: April 2003

Ethylene‐propene copolymers (EPR) were synthesized at different feed compositions using a highly active and isospecific MgCl2‐supported Ti‐based catalyst. The thermal behavior of EPR was studied by differential scanning calorimetry, the heterogeneity by fractionation, and the chain structure by 13C NMR using the method of substituent chemical shift. The results show that EPR of very low crystallinity (1,0 wt.‐%) can be obtained at high propene content in the feed with a heptane‐insoluble fraction of only 0,9 wt.‐%. Thus, a high isotacticity in propylene sequences and a high randomness in EPR can be achieved at the same time, and producing high‐impact poly(propylene) in a reactor is possible with this catalyst. Sequence distribution and length distribution of ethylene sequences indicate that EPR is produced at multiple active sites, and each site is dominated not only by a first‐order Markovian model but also by unsteady diffusion factors.
Emulsion polymerization of butyl acrylate, 2. Effect of the initiator type and concentration
Authors: Capek Ignác
Published: April 2003

The free radical emulsion polymerization of butyl acrylate initiated by a water‐soluble initiator (ammonium peroxodisulfate, AP) at 60°C in the presence of a blend of anionic and non‐ionic emulsifiers was investigated. The effect of a blend of water‐ and oil‐soluble initiators (AP + 2,2′‐azoisobutyronitrile (AIBN)) is analyzed. Over the interval 2 the rate of polymerization is proportional to the 0,43rd or 0,25th power of the initiator (AP) concentration for runs without or with AIBN. The molecular weights of polymer were found to increase over the low and medium conversion ranges, and the increase is more pronounced at low conversions. Besides, the molecular weight slightly decreases with increasing AP concentration. The addition of AIBN was found to decrease the molecular weight and the rate of polymerization.
Ring opening metathesis polymerization of cyclic alkenes containing heteroatoms
Authors: Watkins Neil , Quigley Paul , Orton Michael
Published: April 2003

The Ring Opening Metathesis Polymerization (ROMP) of a series of cyclic alkenes bearing heteroatom functionality has been performed using a classical WCl6‐based catalyst system. All of the alkenes studied exhibited significantly slower polymerization rates compared with the hydrocarbon monomer dicyclopentadiene (DCPD), this being most pronounced for monomers containing a tertiary nitrogen atom substituted at the 2 position of the norbornene skeleton. Cyclic alkene anhydrides, prepared by the Diels‐Alder addition of cyclopentadiene to maleic and itaconic anhdrides, were found to be polymerizable with high yields giving cross‐linked polymers which exhibited very high glass transition temperatures. Monofunctional cyclic imide derivatives of the cyclopentadiene‐itaconic anhydride adduct were found to be polymerizable to moderate molecular weight thermoplastic materials with high glass transition temperatures, whilst difunctional cyclic imide derivatives led to cross‐linked thermoset polymers. The solution copolymerizations of the cyclopentadiene‐maleic anhydride adduct with DCPD, and of a cyclic imide derivative of the cyclopentadiene‐itaconic anhydride adduct with DCPD, were carried out to form copolymers in high yields having glass transition temperatures intermediate between those of the respective homopolymers.
Ring‐opening metathesis polymerization of endo‐ and exo‐5‐methoxymethylbicyclo[2.2.1]hept‐2‐ene; microstructure of the polymers
Authors: Ivin Kenneth J. , Lam Luk‐Mui , Rooney John J.
Published: April 2003

The title monomers 1 and 2 were polymerized by Ru‐, Ir‐, Mo‐, W‐ and Re‐based metathesis catalysts to yield polymers with cis contents ranging from 10% to at least 90% for 1 and 23–60% for 2. Assignments of the 13C NMR spectra were made. No significant head‐tail bias was observed in either polymer. A high‐trans polymer made from the optically active endo monomer ((−)‐1) was atactic, while high‐cis polymers could be either atactic or biased towards syndiotactic, depending on the catalyst.
Synthesis and characterization of crystalline poly(ethyleneimine)s with mesogenic side chains forming liquid crystals on quaternization
Authors: Masson Patrick , Heinrich Benoit , Frègre Yves , Gramain Philippe
Published: April 2003

The synthesis and thermal properties of a new type of side‐chain liquid‐crystalline polysalts are described. The polymers are first obtained by partial or complete alkylation of a linear poly(ethyleneimine) with 6‐(4‐methoxy‐4′‐biphenylyloxy)hexyl bromide or 12‐(4‐methoxy‐4′‐biphenylyloxy)dodecyl bromide. In a second step, polysalts are prepared by partial or complete quaternization with acyl bromide or dimethyl sulfate. Differential scanning calorimetry, polarizing optical microscopy and X‐ray diffraction experiments show that the polymers and copolymers alkylated with the mesogenic groups are all crystalline. When quaternized, they exhibit thermotropic smectic A phases. This behaviour confirms the smectogenic function of the ammonium units located in the backbone, as already observed with poly(4‐vinylpyridinium) salts.
Primary thermal degradation processes of poly(ether‐sulfone) and poly(phenylene oxide) investigated by direct pyrolysis‐mass spectrometry
Authors: Montaudo Giorgio , Puglisi Concetto , Rapisardi R. , Samperi Filippo
Published: April 2003

The thermal degradation processes which occur in poly(ether‐sulfone) (PES) and poly(phenylene oxide) (PPO) have been studied by Direct Pyrolysis‐Mass Spectrometry (DPMS). The pyrolysis mass spectra of PES and PPO contain molecular ions up to m/z 700, corresponding to pyrolysis compounds of sufficient size to allow the characterization of the primary processes which occur in the thermal cleavage of these polymers. The results obtained indicate that the thermal degradation of PES and PPO proceeds by thermal cleavage of the groups located at the bridges. In the case of PPO the bridges are all homogeneous, and therefore both an intramolecular thermal rearrangement or a radical cleavage process can account for the formation of the primary pyrolysis products. Formation of dibenzofuran units along the PPO chain is a parallel thermal process. In the case PES the simultaneous thermal cleavage of two different bridged units, diphenyl sulfone and diphenyl ether occurs. Extrusion of SO2, with consequent formation of compounds containing biphenyl units, is observed in the thermal degradation of PES. This process is accompanied by formation of dibenzofuran units along the polymer chain, as expected from the thermal cleavage of diphenyl ether units, and by another rearrangement of the polymer backbone, yielding structures containing more oxygen atoms with respect to that of PES.
Primary thermal degradation processes of poly(ether/ketone) and poly(ether ketone)/poly(ether‐sulfone) copolymers investigated by direct pyrolysis‐mass spectrometry
Authors: Montaudo Giorgio , Puglisi Concetto , Samperi Filippo
Published: April 2003

The mechanisms of thermal degradation of poly(ether‐ketone) (PEK) and four poly(ether‐ketone)/poly(ether‐sulfone) copolymers (PEK/PES) have been investigated by direct pyrolysis‐mass spectrometry (DPMS). Several families of pyrolysis compounds with H, OH and CHO end‐groups have been identified in the pyrolysis mass spectra of PEK. All these pyrolysis compounds can arise from degradation mechanisms involving cleavages of the bridged groups (diphenyl ether and dibenzophenone units). Our data show that the main degradation products of PEK are aldehydes, most likely formed by an intramolecular thermal cleavage of benzophenone units. Compounds containing dibenzofuran units have also been observed in the DCI mass spectrum of PEK. The thermal decomposition of a low molecular weight PEK sample occurs in two stages with the maxima of decomposition at 390°C and 490°C, respectively. This fact indicates the occurrence of an end‐group initiated thermal decomposition in the early degradation stage which is not present in the case of the high molecular weight PEK sample. The pyrolysis of PEK does not produce compounds containing biphenyl units, indicating that extrusion of carbonyls or recominbation processes are not involved. The thermal degradation compounds of the PEK/PES copolymers originate from the thermal cleavage of the bridge groups (diphenyl ether, benzophenone and diphenyl sulfone). The pyrolysis mass spectra of 1:1 (alt.), 1:1 (random), 3:1 and 1:3 PEK/PES copolymers appear essentially identical (apart for obvious differences in peak intensities), indicating that the molecular rearrangements (SO2 extrusion, transesterification, cleavage of bridges) which occur at higher temperatures and/or in the pyrolysis processes are able to randomize the distribution of comonomer units originally present in the copolymers. Differences in peak intensities have been found to reflect almost quantitatively the molar composition of the copolymers.
Aqueous ring‐opening metathesis polymerisation of 7‐oxanorbornene derivatives with oxygen‐containing functionalities
Authors: Lu Shui‐Yu , Amass Judith M. , Majid Nazia , Glennon Dermott , Byerley Andrew , Heatley Frank , Quayle Peter , Booth Colin , Yeates Stephen G. , Padget John C.
Published: April 2003

A number of 7‐oxanorbornene derivatives with hydroxymethyl, methoxymethyl and acetoxymethyl functionalities were synthesised and investigated as monomers in ring‐opening metathesis polymerisation (ROMP) catalysed by commercial ruthenium trichloride in aqueous ethanolic solvents. Comparison was made with related polymerisations of 7‐oxanorbornene derivatives with anhydride, methoxymethyl and carboxylic acid functionalities. The structures of the polymers were investigated by 1H and 13C NMR and their molar masses and molar mass distributions by gel‐permeation chromatography.
Synthesis of vinyl‐terminated isotactic poly(propylene) using the coupling reaction between Zn‐terminated polymer and allyl halides
Authors: Kurosawa Hiroki , Shiono Takeshi , Soga Kazuo
Published: April 2003

Propene was polymerized with the TiCl3/Al(C2H5)2Cl catalyst system using Zn(C2H5)2 as a chain transfer reagent. The resulting Zn‐terminated poly(propylene) (PP) was then brought into contact with allyl halides (chloride, bromide and iodide) in the presence of N‐methylimidazole to obtain vinyl‐terminated PP. Allyl bromide gave the highest conversion among these allyl halides. When the coupling reaction was conducted with allyl bromide at 40°C for 24 h, the conversion to the terminal vinyl groups was over 90% for atactic PP and approximately 60% for isotactic PP. The Zn‐polymer bonds of both atactic and isotactic PP were almost quantitatively converted into terminal vinyl groups at 130°C for 3 h.
The influence of regio‐ and stereoirregularities on the crystallization behaviour of isotactic poly(propylene)s prepared with homogeneous group IVa metallocene/methylaluminoxane Ziegler‐Natta catalysts
Authors: Fischer David , Mülhaupt Rolf
Published: April 2003

Poly(propylene)s with narrow molecular weight distributions were prepared with various methylaluminoxane‐activated metallocene‐based Ziegler‐Natta catalysts to study the influence of randomly incorporated regio‐ and stereoirregularities on the crystallization behavior. As a function of the metallocene type and the polymerization temperature, the molecular weights varied between 11500 < Mn < 63 000, melting temperatures of annealed samples between 125 to 158°C, and the corresponding degrees of crystallinity, as measured by wide‐angle X‐ray scattering, between 49 and 67%. While the virgin poly(propylene)s exhibited exclusively the α‐modification, annealing and melt crystallization favored the development of the γ‐modification. The microstructure analysis by 13C NMR spectroscopy revealed a linear correlation between the content of the γ‐modification and the average length of the isotactic segments.
OH‐radical‐induced crosslinking and strand breakage of poly(vinyl alcohol) in aqueous solution in the absence and presence of oxygen. A pulse radiolysis and product study
Authors: Ulanski Piotr , Bothe Eberhard , Rosiak Janusz M. , von Sonntag Clemens
Published: April 2003

Hydroxyl radicals were generated radiolytically in N2O‐ or N2O/O2(4:1)‐saturated aqueous solutions of poly(vinyl alcohol) (PVAL) or its low‐molecular‐weight model compound pentane‐2,4‐diol (PD). Using the pulse radiolysis technique, the rate constant of OH with PD and PVAL has been determined to be 2,3 · 109 dm3 · mol−1 · s−1 and 1,5 · 108 dm3 · mol−1 · s−1, respectively. Upon OH attack two kinds of radicals are generated: (i) tertiary α‐hydroxyalkyl radicals and (ii) alkyl radicals. The former rapidly reduce tetranitromethane yielding the stable nitroform anion, and from its yield it is calculated that 70–75% of the radicals are α‐hydroxyalkyl radicals in both systems. In the presence of oxygen, the carbon‐centered radicals are converted into the corresponding peroxyl radicals. The α‐hydroxyalkylperoxyl radicals eliminate HO2˙/O2˙ in spontaneous and base‐catalyzed reactions (rate constants ≈700 s−1 and ≈2,3 · 109 dm3 · mol−1 · s−1, respectively). There are marked differences in the rates of the bimolecular radical decay reactions. The carbon‐centered radicals of PD decay with a rate constant of 5 · 108 dm3 · mol−1 · s−1, whereas those of PVAL decay, under pulse‐radiolytic conditions, mainly intramolecularly (loop formation), with rate constants which reach, at high radical numbers per macromolecule, values as high as 1010 dm3 · mol−1 · s−1. With PD it was shown by product studies that the radicals mainly (90%) disproportionate and dimerize only to 10%, thus limiting the yield of crosslinks in PVAL to the latter value. The bimolecular decay rates of the organic peroxyl radicals in O2˙ containing solutions are more difficult to investigate because of the effective unimolecular HO2˙‐elimination reaction. However, it is estimated that the peroxyl radicals of both compounds decay (under otherwise equal conditions) more than one order of magnitude slower than the carbon‐centered radicals. The measured yields of strand breaks in oxygenated solutions as well as the yields of intermolecular crosslinks under anoxia, determined with PVAL by low‐angle laser light‐scattering at different dose‐rates and pH values, support these conclusions.
Phase‐restricted radiation crosslinking in semicrystalline polyolefins investigated by two‐dimensional solid‐state nuclear magnetic resonance
Authors: Beckham Haskell W. , Spiess Hans Wolfgang
Published: April 2003

The utility of two‐dimensional wideline separation (2D WISE) NMR in following the phase dependence of the radiation‐induced crosslinking of multiphase materials has been demonstrated. Crosslink production in semicrystalline polyolefins by high‐energy electron irradiation in air was monitored via the experimentally resolved 1H lineshapes of the respective amorphous and crystalline regions. It was shown that radiation‐induced crosslinks can be primarily restricted to one phase or the other by proper functionalization, or nonfunctionalization, of the host polymer. Poly(1,23‐tetracosadiyne), a diacetylene‐functionalized polyethylene, was synthesized and shown to predominantly undergo crystalline‐phase crosslinking for dosages of 100 kGy and less. Thus, chain mobility within amorphous regions may be maintained upon radiation‐induced crosslinking. In comparison, linear polyethylene exhibited amorphous‐phase crosslinking for electron beam radiation dosages of at least 400 kGy; application of 2D WISE NMR represents a direct method for following this well‐known process.
Dimerizations of acrylate monomers with sodium hydroxymethanesulfinate and characterization of the products
Authors: Wang Cheng‐Chien , Kuo Jen‐Feng , Chen Chuh‐Yung
Published: April 2003

The reactions of sodium hydroxymethanesulfinate (sodium formaldehyde sulfoxylate, SFS) with various monomers, including acrylates, methacrylates, styrene and vinyl acetate, were studied. The reaction products formed depended on the molecular structure of the monomers and acidity of the reaction solution. Among the monomers studied, acrylates with resonance stability values Q between 0,38 and 0,45 produced diacrylate sulfones in neutral conditions. The other monomers or reaction conditions did not result in a dimer. The obtained diacrylate sulfones were characterized by elemental analysis, mass spectrometry, IR spectra, normal 1H and 13C NMR, CHn (n = 1, 2 and 3) subspectra by Distortionless Enchancement by Polarization Transfer at θ = 3π/4, as well as by 1H‐ 13C 2D‐NMR spectra using Correlated Spectroscopy and Heteronuclear Multiple Bonding Correlation methods. A possible reaction mechanism for the formation of dimers is suggested. The morphology and thermal properties of these diacrylate sulfones were determined.
Anionic polymerisation of propylene oxide. Investigation of double‐bond and head‐to‐head content by NMR spectroscopy
Authors: Yu Ga‐Er , Masters Andrew J. , Heatley Frank , Booth Colin , Blease Trevor G.
Published: April 2003

Propylene oxide was anionically polymerised in bulk at 80°C under a range of initial conditions, from zero hydroxyl content to a mole ratio of hydroxyl to potassium catalyst of 10. The double bond content of the polymers was measured by 1H NMR spectroscopy over a wide range of conversions, and values of the transfer constant were determined. The results were fitted to a reaction mechanism involving suppression of the transfer reaction by hydrogen bonding of hydroxyl groups to active ion pairs. The head‐to‐head content of the polymers was measured by 13C NMR spectroscopy. The overall proportion (approximately 4%) of ‘head‐to‐head’ reactions relative to head‐to‐tail addition was not greatly affected by suppression of the transfer reaction, since an increase in the number of head‐to‐head additions compensated the decrease in proton abstraction from methyl groups via the transfer reaction.
Immobilization of enzymes by multilayer microcapsules
Authors: Pommersheim Rainer , Schrezenmeir Jürgen , Vogt Walter
Published: April 2003

A method is described to obtain a new type of microcapsules for immobilization of enzymes or living cells. The wall of these capsules consists of several layers of poly(ethyleneimine) and poly(acrylic acid). The idea is that diverging properties of the whole assembly can be better controlled when the membrane is built up by several consecutive steps, each being optimized with respect to a special property, for example, permeability or mechanical strength. The encapsulation of acidic phosphatase and the cleavage of p‐nitrophenyl phosphate was used as a model system. The charged capsules were characterized by their enzymatic activity, as a function of membrane composition (number and sequence of layers) and storing time. The permeability for the substrate and the retaining ability for the enzyme were also measured.
Ferroelectric liquid crystalline polysiloxanes designed for high second‐order nonlinear susceptibilities
Authors: Wischerhoff Erik , Zentel Rudolf , Redmond Maura , Mondain‐Monval Olivier , Coles Harry
Published: April 2003

Ferroelectric liquid crystalline (FLC) copolysiloxanes containing suitable comonomers (“NLO‐chromophores”) for second harmonic generation (SHG) have been prepared. Their important feature is a donor‐acceptor π‐system sited perpendicular to the long axis of the side‐group moieties in order to adopt the polar ordering of the ferroelectric LC phase. The influences of the mesogen structure and of the content of NLO‐chromophores on the liquid crystalline and ferroelectric properties are studied. The desired chiral smectic C* phase is retained up to 30 mol‐% of chromophore. Also, first measurements of second harmonic generation have been performed.
Bacterial production of polyesters bearing phenoxy groups in the side chains, 1. Poly(3‐hydroxy‐5‐phenoxypentanoate‐co‐3‐hydroxy‐9‐phenoxynonanoate) from Pseudomonas oleovorans
Authors: Ritter Helmut , von Spee Astrid Gräfin
Published: April 2003

The production of phenoxy‐substituted poly(3‐hydroxyalkanoates) (PHA) by Pseudomonas oleovorans was investigated. 11‐Phenoxyundecanoic acid was used as a single carbon source for the bacterial culture. At the maximum growth rate of the culture, the cells were isolated by centrifugation. The cells were lyophylized and then extracted with trichloromethane, yielding a comb‐like copolyester. Methanolysis of this polyester was performed to characterize the incorporated hydroxyacids. This proved the polyester to be a copolymer: poly(3‐hydroxy‐5‐phenoxypentanoate‐co‐3‐hydroxy‐9‐phenoxynonanoate) (5; 6:1 mole ratio). GPC measurements with polystyrene as standard indicated Mn values of approximately 76 000 and a molecular weight distribution index of Mw/Mn = 2,3. The copolyester showed a glass transition at 14°C.
In situ X‐ray absorption spectroscopy at the K‐edge of red phosphorus in polyamide 6,6 during a thermo‐oxidative degradation
Authors: Küper Gerhild , Hormes Josef , Sommer Klaus
Published: April 2003

We present a new method for studying the influence of flame retardants as a function of time and temperature by measuring the X‐ray absorption spectra of the corresponding additive. Here, red phosphorus in polyamide 6,6 was investigated at the phosphorus K‐edge using synchrotron radiation. The thermo‐oxidative degradation of the polymer was simulated by heating the sample up to 300°C. XANES

XANES, EXAFS: X‐ray absorption spectroscopy investigating the near edge structure or the fine structure of the extended region, respectively.

spectra were monitored during the degradation process at different temperatures and at a constant reaction temperature as a function of time. The degradation reaction was analyzed by comparing the XANES spectra of red phosphorus and orthophosphoric acid, and the reaction was identified as an oxidation of red phosphorus to H3PO4. The results so obtained are confirmed by the EXAFS spectra of the additive in the polymer sample recorded before and after the thermo‐oxidative degradation process, and by the EXAFS spectra of suitable reference compounds.
Novel regular‐network polyurethane films from polyols and diisocyanates
Authors: Kiyotsukuri Tsuyoshi , Nagata Minoru , Okada Hiroyuki , Miura Daisuke , Tsutsumi Naoto
Published: April 2003

Novel regular‐network polyurethane films were prepared from polyols of phloroglucinol (1), 2,4,2′,4′‐tetrahydroxybenzophenone (2) or glycerol (3), and diisocyanates of hexamethylene diisocyanate (6), 4,4′‐diphenylmethane diisocyanate (4,4′‐methylenebis(1,4‐phenylene) diisocyante (5)) or p‐phenylene diisocyanate (4). Prepolymers prepared by solution polyaddition were cast and successively post‐polymerized at various temperatures between 60 and 160°C for 1 h to form networks. The resultant films were transparent, flexible and insoluble. Heat distortion temperatures (Th) of the polyurethane films increased with increasing post‐polymerization temperature. The highest Th values obtained are 52, 58, 61, 69, 99, 122, 122 and 151°C for 1/5, 3/5, 2/5, 3/6, 2/4, 1/6, 1/4 and 2/6, respectively. The densities of polyurethane films also increased with increasing post‐polymerization temperature, which is comparable with an increase of Th. The X‐ray diffraction patterns of films showed two diffraction peaks, suggesting some ordered structure due to the regular networks. The network polyurethane film showed higher Th and tensile strength compared with the corresponding network polyester film, suggesting an effect of intermolecular hydrogen bonding. All films started to decompose at a temperature around 120°C due to the decomposition of unreacted terminal isocyanate groups. The thermal stability of a network polyurethane film could be remarkably enhanced by capping the unreacted terminal isocyanate group with phenol.
Optically active polymers, 2. Copolymerization of limonene with maleic anhydride
Authors: Maślińska‐Solich Jolanta , Kupka Teobald , Kluczka Mirosław , Solich Anton
Published: April 2003

Copolymerization of maleic anhydride (MA) and (R),(S)‐limonene (LIM) was studied in various solvents, using 2,2′‐azoisobutyronitrile (AIBN) and benzoyl peroxide (BPO) as initiators and radiation (60Co γ‐source) within the temperature range of 20–70°C. Regardless of conversion or initial comonomer feed ratios, the composition of LIM‐MA copolymers ranged from about 1 : 1 to 1 : 1,6 and was dependent on the reaction conditions, leading to a formation of materials with diverse solubilities, degrees of crosslinking and molecular weights. The main product consists of a 1 : 1 LIM‐MA copolymer with pendant 4‐methyl‐3‐cyclohexenyl residues. At higher conversion these alicyclic unsaturations lead to crosslinking. No reference to cyclocopolymerization was detected.
Structural analysis of the components of Chinese lacquer “Kuro‐urushi”
Authors: Hatada Koichi , Kitayama Tatsuki , Nishiura Takafumi , Nishimoto Akira , Simonsick William J. , Vogl Otto
Published: April 2003

The urushiol components in Chinese lacquer “Kuro‐urushi”, which was processed by treating Chinese Raw Urushi (“Ki‐urushi”) with Fe(OH)2, were isolated by reversed‐phase liquid chromatography. A new component, which was not present in “Ki‐urushi”, was found. Structural analysis using 1H NMR and mass spectrometry showed that the component is a regioselectively formed water adduct of the original urushiol component, i. e., 3‐(11′E,13′Z‐8′‐hydroxypentadecadienyl)catechol.
Molecular mechanical analysis of polymer conformation, 2. Relation between chain conformation and birefringence of stretched non‐crystalline polyurethanes with various substituent groups
Authors: Konda Masakazu , Yamane Hideki , Kimura Yoshiharu , Kitao Toshio
Published: April 2003

The relationship between birefringence and polymer structure was studied both by theoretical and experimental analyses of a series of non‐crystalline polyurethanes (PU) with different side groups. The most probable steric structures of PUs were estimated by molecular mechanical calculation (MM2) of their oligomeric model compounds, and their birefringence was theoretically calculated on the structural data obtained. In addition, some of the PUs were practically synthesized and melt‐spun into thin fibers, which were drawn to a maximum draw ratio to measure the values of birefringence. The comparison of the measured and estimated values revealed that the present estimation method is effective for simulating the chain conformations and the birefringence of fully or partially extended polymer chains, which ought to be formed by drawing and melt‐flow of glassy materials. Of particular interest was that phenyl‐substituted PUs exhibit an unexpectedly larger birefringence than methyl‐substituted PUs. This fact was reasonably explained by the angular rotation of the highly polarizable phenyl group, which is energetically easily allowed and influences strongly the value of birefringence.
New catalytic systems for the fixation of carbon dioxide, 2. Synthesis of high molecular weight epichlorohydrin/carbon dioxide copolymer with rare earth phosphonates/triisobutyl‐aluminium systems
Authors: Shen Zhiquan , Chen Xianhai , Zhang Yifeng
Published: April 2003

Copolymerization of carbon dioxide with epichlorohydrin to synthesize high molecular weight chlorine‐containing poly(carbonate‐ether) with RE(P204)3Al[CH2CH(CH3)2]3 (with RE = La, Eu, Gd, Dy, Ho, Nd, Er, Yb, Lu, Y; P204 = (RO)2POO, R = CH3(CH2)3CH(C2H5)CH2) as a catalyst was carried out for the first time. The most favorable conditions for the copolymerization were: CO2 aged Y(P204)3Al[CH2CH(CH3)2]3 as catalyst; mole ratio Al/Y = 8; reaction time 24 h; temperature 60–70°C; concentration [Y] = 3,31 · 10−2 mol/L; 1,4‐dioxane as solvent. The highest yield, intrinsic viscosity [η] and CO2 content of the copolymer obtained reached 3 945 g per mole of rare earth element, [η] = 1,49 dL/g and f(CO2) = 30 mol‐%, respectively. Results from differential thermal analysis/thermogravimetry showed that the copolymer has high thermal stability and decomposes at 320°C.
Synthesis and structure‐property relations of polymers for light emitting diodes based on isolated chromophore units
Authors: von Seggern Heinke , Schmidt‐Winkel Patrick , Zhang Chi , Schmidt Hans‐Werner
Published: April 2003

New fluorescent polymers for electroluminescent devices were synthesized and characterized. In order to obtain polymers for blue light emitting diodes (LEDs), two different structural concepts based on isolation of the active chromophore units within the polymer main chain were investigated. In the first approach non‐coplanar units were used to reduce the conjugation length in poly(arylenevinylene)s. In a second approach copolymers having isolated chromophore units in the polymers main chain were investigated. For this purpose, copolyesters containing isolated 1,2‐dinaphthylethene chromophore units were synthesized and characterized. The influence of the chemical structure on the photo‐ and electroluminescence is discussed. On the example of copolyester 2b, which shows bluegreen electroluminescence (λmax = 497 nm) in a LED configuration, it was demonstrated that these polyesters can be used as light emitting layer in electrooptical devices.
Thermal properties of poly(butylene isophthalate) and its copolyesters with poly(butylene adipate)
Authors: Righetti Maria Cristina , Pizzoli Maria , Munari Andrea
Published: April 2003

The thermal properties of uniformly random poly(butylene adipate/isophthalate) copolyesters of various composition and different molecular weight were investigated by means of differential scanning calorimetry. All copolymers were partially crystalline, and the main effect of copolymerization was a lowering in the amount of crystallinity and a decrease of melting temperature with respect to pure homopolymers. The heat of fusion of 100% crystalline poly(butylene isophthalate), estimated by different methods, was found to fall within the range 22–25 kJ · mol−1. Completely amorphous samples, obtained by rapid quenching from the melt, showed a monotonic decrease of the glass transition temperature Tg and a monotonic increase of the heat capacity increment ΔCp with increasing butylene adipate content in the copolymers. The Tg‐composition dependence was found to be well fitted by the Couchman equation with no excess enthalpy correction.
Polymers by [3 + 2] cycloaddition, 6. Polyureas with novel structure elements
Authors: Maier Gerhard , Nuyken Oskar , Losert Klaus
Published: April 2003

The synthesis of new diisocyanates via “criss‐cross” cycloaddition between aromatic aldazines and diisocyanates as well as their conversion to polyureas is described. The new monomers and polymers contain the heterocyclic 1,3,5,7‐tetraazabicyclo[3.3.0]octane‐2,6‐dione system in their backbone. The polymers are characterized by spectroscopic techniques, DSC, thermogravimetry, and GPC. The influence of the new structure element on solubility, glass transition temperature, crystallinity, and thermal stability is discussed.
Effect of substituents on the radical copolymerization of ring‐substituted trans‐cinnamonitriles with vinyl monomers
Authors: Tanaka Hitoshi , Sakaguchi Masakazu , Kikukawa Yoshimasa , Sato Tsuneyuki , Ota Tadatoshi
Published: April 2003

Radical copolymerizations of ring‐substituted trans‐cinnamonitriles with olefins such as styrene and acrylonitrile were studied at 60°C. The copolymerization parameters of cinnamonitriles (M1) in the copolymerizations with styrene (M2) were determined to be r1 = 0,01 to 0,30, r2 = 0,45 to 4,25, Q1 = 0,06 to 0,70, and e1 = −0,52 to 1,35. The relative reactivity, log(1/r2), showed a tendency to increase with increasing Hammett constant σ and was higher in conjugated cinnamonitriles than in less conjugated nitriles. For p‐substituted cinnamonitriles, ρ and γ values in the equation of log(1/r2) = ρ · σ + γ · ER were estimated to be 0,48 and 2,0, respectively, where ER is a resonance constant. The relative reactivity was also increased with increasing 13C NMR chemical shift of the olefinic β‐carbon of cinnamonitriles and decreasing polarity of the solvents used. In addition, the relative reactivity towards a poly(acrylonitrile) radical is higher in cinnamonitrile than in cinnamic esters. The structure of the radical generated by the attack of the 2‐methyl‐2‐propyl radical at the cinnamonitrile was examined by means of electron paramagnetic resonance (EPR) spectroscopy.
Syndiospecific polymerization of styrene by soluble alkoxytitanium catalysts
Authors: Kaminsky Walter , Lenk Stephan
Published: April 2003

The activity of Ti(OEt)4 (Et: C2H5) in combination with methylaluminoxane (MAO) in the syndiospecific polymerization of styrene was investigated concenrning the dependence on temperature, mole ratio of Al/Ti, concentrations of monomer, catalyst and MAO. Reaction products of Ti(OEt)4 and erythritol and sorbitol, respectively, were also used in the syndiospecific polymerization of styrene revealing that soluble Ti compounds are the active species.