bluuebunny/crossref_metadata_2025 huggingface dataset:
New crown ether resins prepared by cationic template polymerization
Authors: Li Kai , Ferrari Lorenzo P. , Brown Chris , Stöuver Harald D. H.
Published: April 2003

The synthesis of several dibenzo‐18‐crown‐6 derivatives, and their acid catalyzed incorporation into crosslinked styrene and 4‐methoxystyrene based copolymers is described. Some of these reactions were carried out in the presence of chiral ammonium cations acting as non‐covalent templates. The polymers have been characterized by IR, and by 1H and 13C solution state and magic angle spinning NMR.
Interaction of crosslinked poly(4‐vinylpyridine) with methyl orange
Authors: Kim Woo‐Sik , Lee Suk‐Kee , Seo Kwan‐Ho
Published: April 2003

Various crosslinked poly(4‐vinylpyridine)s (3) having different degrees of crosslinking were prepared by the radical copolymerization of 4‐vinylpyridine (1) with N,N′‐hexamethylenediacrylamide (2) as a crosslinker. These crosslinked polymers were examined for their ability to bind methyl orange at various temperatures in a buffer solution of pH 7. The first binding constants (K1) and thermodynamic parameters that accompany the binding were evaluated. The values of K1 show bell‐shaped curves against both the binding temperature and the degree of crosslinking of 3. Lower temperature and higher degree of crosslinking for the maximum binding in the bell‐shaped phenomenon of this binding system were observed, when they were compared with those of the previously reported binding systems, 1/N,N′‐methylenediacrylamide copolymers‐methyl orange and 1/N,N′‐tetramethylenediacrylamide copolymers‐methyl orange. The values of enthalpy change and entropy change increase with increasing degree of crosslinking of 3, whereas the absolute magnitude of free energy change is not increased. These results could be accounted for in terms of the temperature dependence of the hole size of 3 rather than the hydrophobic interaction in the binding process.
Thermally crosslinked rigid…rod aramids, 1. Synthesis of a new monomer and its polymerization
Authors: Rickert Christoph , Neuenschwander Peter , Suter Ulrich W.
Published: April 2003

With 2,2,6,6‐tetraoxo‐1,3,5,7‐tetrahydro‐2,6‐dithia‐s‐indacene‐4,8‐diamine (DSDA) (8), a new monomer for the synthesis of thermally crosslinkable rigid‐rod aramids was developed. DSDA was copolymerized with p‐phenylenediamine and terephthaloyl dichloride by a low‐temperature solution polycondensation to give high‐molecular‐weight aramids (inherent viscosity ηinh > 2,2 dL/g). The fraction of DSDA could be varied from 0 to 100 mol‐% of the diamine used in the condensation. All polymers showed a weight loss due to thermal elimination of SO2. Thermal crosslinking could be effected by curing the samples at high temperatures (280–320°C). The crosslinking reaction was investigated by means of thermogravimetry (TG), thermogravimetry/mass spectrometry (TG‐MS), Fourier transform infrared (FT‐IR), 13C cross polarization‐magic angle spinning nuclear magnetic resonance (13C CP‐MAS NMR) and electron paramagnetic resonance (EPR). The activation energy for this reaction was found to be between 150 and 170 kJ/mol. Curing of the polymer samples led to the generation of stable, matrix‐isolated radicals.
Structural study of compounds modelling elementary polymer units, 6. X‐ray structural and quantum‐chemical investigation of the cis‐ and trans‐isomeric models of the polynaphthoylenebenzimidazole elementary units
Authors: Lindeman Sergey V. , Ponomaryov Igor I. , Raevsky Nikolai I. , Struchkov Yurii T. , Rusanov Alexandr L.
Published: April 2003

The X‐ray structural investigation of the naphthoylenebis‐(benzimidazole) (1) cis‐ and trans‐isomers as models for the cis and trans elementary units of the corresponding poly(naphthoylene‐benzimidazoles) (PNBI) was carried out. The correctness of the previous identification of the isomers was confirmed, and exact geometrical parameters of the PNBI elementary units (required, in particular, for the calculation of the Kuhn segment of PNBI) were determined. Quantum‐chemical semi‐empirical calculations of the ground and excited electronic states of the isomers were carried out. Both experimental and theoretical data confirm a larger stability of the planar π‐conjugated structure of the trans‐isomer in comparison with the cis‐isomer in the ground as well as in the excited electronic state. Crystals of the cis‐ and trans‐isomers obtained from trifluoroacetic acid solutions are the solvates of bis(trifluoroacetates) of diprotonated 1 with an extremely high content of the solvating trifluoroacetic acid. This peculiarity is favourable for modelling the main characteristics of the interaction between PNBI and protonic polar solvent molecules, viz. preferred types of H‐bonding and a possibility of interaction of the electronic lone pairs of the solvent molecules with the π‐electronic systems of the elementary units of PNBI by charge transfer complexes.
Synthesis of methyl methacrylate/styrene copolymer bearing a carbomethoxyallyl end group with limited molecular weight by addition‐fragmentation reaction of methyl α‐(bromomethyl)‐acrylate
Authors: Yamada Bunichiro , Kobatake Seiya , Aoki Shuzo
Published: April 2003

The synthesis of methyl methacrylate/styrene copolymer bearing overwhelmingly bromine and the 2‐carbomethoxyallyl group (CH2C(COOCH3)CH2) at the α‐ and ω‐termini instead of the fragment of the initiator with reduced molecular weight was investigated by using methyl α‐(bromomethyl)acrylate as chain transfer agent through the addition‐fragmentation mechanism. The molecular weight of the copolymer was effectively decreased with bromomethylacrylate, and the unsaturated end groups quantitatively bound to two types of the monomeric units were differentiated by means of 1H NMR spectroscopy. Equations estimating the reactivities of methyl α‐(bromomethyl)acrylate towards polystyrene and poly(methyl methacrylate) radicals were derived. Methyl α‐(bromomethyl)acrylate was found to be more reactive toward the poly(methyl methacrylate) radical than the polystyrene radical by a factor of 0,62.
Radical polymerization of ring‐substituted trans‐cinnamonitriles and formation of ladder spin polymer
Authors: Tanaka Hitoshi , Kikukawa Yoshimasa , Sataki Maki , Sato Tsuneyuki , Ota Tadatoshi
Published: April 2003

The polymerization of ring‐substituted trans‐cinnamonitriles has been studied with radical initiators such as peroxides and azo compounds at 60–130°C. 3,4,5‐Trimethoxycinnamonitriles (3,4,5‐MOCN) yield a homopolymer with a molecular weight of about 104 in contrast to the unsubstituted cinnamonitrile. The activation energy of the 3,4,5‐MOCN polymerization is 106 kJ/mol and the polymerization rate is proportional to the 0,45th power of the initiator concentration. Radical copolymerization of 3,4,5‐MOCN yields copolymers with vinyl monomers such as styrene and acrylonitrile. ESR studies suggested that the primary radical from an azo initiator attacks at the olefinic carbon of the cinnamonitrile bearing the cyano group. Heating of the 3,4,5‐MOCN homopolymer produces a ladder spin polymer with hydroaniline units in the main chain.
Multicolor electrochromic behavior of polyaniline composite films combined with tungsten trioxide
Authors: Morita Mitsuyuki
Published: April 2003

The electrochromic behavior of polyaniline‐poly(vinyl alcohol) composite films (CPAn‐PVA) combined with an electrochemically synthesized tungsten trioxide film (WO3) was investigated in LiClO4CH3CN aprotic non‐aqueous solution. The combination was achieved by chemical deposition of CPAn‐PVA on WO3. The combined film shows an electrochromic behavior roughly identical with the sum of the behaviors of each component material. The color change of the combined film from blue to green in the cathodic region is of lower contrast in comparison with that expected from the combination. From ex‐situ FT‐IR spectroscopy it became clear that the weakened electrochromic change is due to some interaction between polyaniline and WO3. However, this interaction also activates the electrochemical oxidation process of polyaniline. As a result, the combined film shows a color change owing to the oxidation of polyaniline applying much lower potential than for CPAn‐PVA. This suggests the possibility of construction of electrochromic devices with high electrochemical stability operating at low potentials.
Particle growth in butadiene emulsion polymerization, 2. Gamma radiolysis
Authors: Verdurmen Edwin M. , German Anton L. , Sudol E. David , Gilbert Robert G.
Published: April 2003

The kinetics of the emulsion polymerization of butadiene at 60°C in Smith‐Ewart interval III were investigated using gamma radiation to produce initiating species. The aim of this work was to determine radical desorption rate coefficients through monitoring non‐steady state kinetics. The acquired data of the average number of radicals per particle (n) were in good agreement with data obtained from chemically initiated experiments. It was shown that the approach to steady state is kinetically determined and that thermal background initiation is negligible in the butadiene emulsion polymerization. While radical desorption rate coefficient data was determined with high uncertainty, the results are consistent with the transfer diffusion mechanism of radical exit.
Particle growth in butadiene emulsion polymerization, 3. Radical adsorption and desorption rate coefficients
Authors: Verdurmen Edwin M. , Geurts John M. , German Anton L.
Published: April 2003

The kinetis of the emulsion polymerization of butadiene at 60°C in Smith‐Ewart interval III were investigated using peroxodisulfate as initiator. The aim of this work was to obtain insight in the radical adsorption and desorption rate coefficients through monitoring non‐steady state kinetics. The acquired data shows an initiator concentration dependence of the desorption rate coefficients. This dependence explains the independences of the rate of butadiene emulsion polymerization of the peroxodisulfate concentration in the presence of tertiary dodecylthiols.
Influence of ageing on the ordering phenomena of syndiotactic polystyrene
Authors: de Candia Francesco , Russo Roberto , Vittoria Vittoria
Published: April 2003

The crystallization from the glassy state of different samples of syndiotactic polystyrene (sPS) was investigated with different techniques, such as differential scanning calorimetry, infrared analysis, and polarized optical microscopy. The different samples of sPS were obtained by ageing the glassy sPS films at room temperature and at 70°C; the behaviour of these films was compared with that of the fresh sample, put at the crystallization temperature as soon as prepared. The temperature of crystallization was 120°C; at this temperature, besides the crystalline phase, a fraction of mesophase is formed. All the techniques investigated to follow the crystallization phenomenon show that the fresh sample crystallizes much sooner than the others; the sample aged at 70°C takes the longest time to crystallize, whereas an intermediate behaviour characterizes the sample aged at room temperature. This result was correlated with the initial structural organization of the glassy amorphous samples.
The system methylcyclohexane/polystyrene. Experimental critical curves, cloud‐point and spinodal isopleths, and their description with a semi‐phenomenological treatment
Authors: Vanhee Sabine , Kiepen Friedheinz , Brinkmann Dirk , Borchard Werner , Koningsveld Ronald , Berghmans Hugo
Published: April 2003

Cloud‐point and spinodal pressures up to 900 bar were investigated for the system methylcyclohexane/polystyrene using a pressure‐pulse‐induced scattering technique based on the theory of Debye. The molar‐mass range of the polymer samples is 9–50 kg/mol. The values determined isothermally in a large concentration range for a polymer sample with weight‐average molar mass Mw = 17,5 kg/mol lead to isopleths which allow the construction of phase diagrams displaying cloud‐point and spinodal curves (in terms of temperature or pressure against concentration). Critical isopleths have been determined for three further samples with Mw = 9,0, Mw = 28,5 and Mw = 50,0 kg/mol. A semi‐phenomenological treatment of the data is presented which allows an accurate description of experimental phase diagrams and isopleths for one single sample (PS 17,5). A prediction of the critical P(T) curves for the other samples, of different average molar mass, then fails completely. Fitting the model parameters to the critical data of all four samples improves the description of the critical curves but produces phase diagrams showing considerable deviations from the data. One reason for the failure of the model may be sought in its inherent incapability to deal with dilute polymer solutions in which the individual coils are separeated by regions of pure solvent. A first rough attempt to deal with this effect already brings a marked improvement in the agreement between experiment and model calculation for the critical curves, albeit at the cost of introduction of a number of adaptable parameters.
Study of polystyrene‐block‐poly(methyl methacrylate) micelles by size exclusion chromatography/low‐angle laser light scattering, 1. Influence of copolymer concentration and flow rate
Authors: Grubišć‐Gallot Zlatka , Gallot Yves , Sedláček Jan
Published: April 2003

A size exclusion chromatography study of the micellar system polystyrene‐block‐poly(methyl methacrylate) in the mixed solvent 1,4‐dioxane/cyclohexane is reported. Good separation of the peaks of micelles enabled direct determination of the weight‐average molecular weights of micelles with a low‐angle laser light scattering detector. The values obtained were found to be in accordance with those determined independently by static light scattering. Experiments with changing flow rate and concentration of the injected sample solution show moderately fast unimer‐micelles re‐equalibration in the course of the separation. A strong effect of the solute trapping in the column, probably due to the adsorption of the unimer on the packing, was observed.
Rate constants for elementary reactions of the radical polymerization of methyl 2‐(benzyloxymethyl)acrylate as polymerizable acrylate bearing large substitutents
Authors: Yamada Bunichiro , Kobatake Seiya , Aoki Shuzo
Published: April 2003

Methyl 2‐(benzyloxymethyl)acrylate (MBZMA) which was synthesized by reaction of methyl 2‐(bromomethyl)acrylate with benzyl alcohol was radically homo‐ and copolymerized. MBZMA polymerized as fast as methyl methacrylate despite of the presence of a large 2‐substituent. The absolute rate constants for propagation and termination were evaluated from the direct determination of the steady state concentration of the propagating radical by electron spin resonance spectroscopy at 60°C: kp = 182 dm3 · mol−1 · s−1 and kt = 1,6 · 106 dm3 · mol−1 · s−1. It was deduced from the magnitude of the rate constants that the balance of the slow propagation and termination allows the formation of a polymer. Evaluation of the cross‐propagation rate constants in the copolymerization with styrene revealed that primarily the steric effect of the benzyloxymethyl group reduced the reactivity of the polymer radical and that the electronwithdrawing character of the 2‐substituent prevailing the steric effect enhanced the monomer reactivity toward the polystyrene radical.
Fluorescence spectra of polybenzamide in isotropic and nematic solutions
Authors: Bai Fenglian , Zhang Shufan , Yang Junlin , Qian Renyuan
Published: April 2003

The fluorescence spectra of polybenzamide (PBA) in N,N‐dimethylacetamide with 3% LiCl (A) and in 98% H2SO4 (B) solutions have been studied both in very dilute and in nematic solutions. Stacked chromophores of PBA play an important role in the formation of nematic phase. Fluorescence intensity from solution A is much higher than that from solution B under the same conditions of excitation. Differences in the fluorescence behavior of solutions A and B are discussed in regard of the monochromophore emission and monochromophore excitation and long wavelength emission. Fluorescence emission has been shown to be an extremely sensitive tool to probe some molecular species present in minute amounts, which show up readily in the excitation spectrum of fluorescence emission but escape from detection in the absorption spectrum.
Initiation and propagation reactions in the copolymerization of epoxide with carbon dioxide by catalysts based on diethylzinc and polyhydric phenol
Authors: Kuran Witold , Listoś Tomasz
Published: April 2003

Propylene oxide and cyclohexene oxide were copolymerized with carbon dioxide in the presence of catalysts such as diethylzinc with phenol or 1‐phenoxy‐2‐propanol and/or a polyhydric phenol (polyhydroxybenzene derivatives such as 4‐tert‐butylcatechol, pyrogallol): The corresponding copolymers with predominant carbonate linkages and the respective cyclic alkylene carbonates as by‐products were obtained in the presence of catalysts derived from diethylzinc and polyhydric phenol. Cyclic alkylene carbonates but no polymeric products were formed in the presence of catalysts derived from diethylzinc and monoprotic compound. The copolymers were analysed by means of 1H‐ and 13C nuclear magnetic resonance (NMR) spectroscopy in terms of chain microstructure and end groups. Alkaline hydrolysis of the cyclohexene oxide/carbon dioxide copolymer was performed and the trans‐structure of the obtained cyclohexane‐1,2‐diol was determined. Mechanisms for the initiation and propagation reactions are proposed and discussed.
Photodegradation of poly[ethylene‐co‐propene‐co‐(5‐ethylidene‐2‐norbornene)] rubbers, 1. Reappraisal of the photo‐oxidation mechanism under accelerated conditions
Authors: Scoponi Marco , Pradella Fiorella , Carassiti Vittorio , Tartari Davide
Published: April 2003

In this work the reexamination of the photo‐oxidation mechanism of three poly(ethylene‐co‐propene‐co‐5‐ethylidene‐2‐norbornene) (EPDM) terpolymers containing different amounts of 5‐ethylidene‐2‐norbornene (ENB)

System. name: 5‐ethylidenebicyclo[2.2.1]hept‐2‐ene.

(2‐8 wt.‐%) is discussed. The photo‐oxidation depends on the initial content of ENB units in the chains. The formation of a band at 923 cm−1 is attributed to the CH out‐of‐plane deformation of a new double bond in terminal position in the ethylidene moieties. The presence of double bond migration suggests the formation of stable tertiary hydroperoxides which show a new band at 870 cm−1. The kinetic behaviour of a band with similar spectral pattern in the UV at 235 nm has been correlated with double bond migration. The identification of photoproducts both by 2,4‐dinitrophenylhydrazin and SO2 confirms the proposed spectroscopic assignments. The gel measurements of the studied terpolymers, and some comparisons with a poly(ethylene‐co‐propene) (EPR) copolymer having a similar ethylene to propene ratio, suggest that the presence of ENB can strongly influence both the photo‐oxidation and the crosslinking yields of these rubbers.
Degradation of poly(propylene carbonate) by coordination catalysts containing phenolatozinc and alcoholatozinc species
Authors: Kuran Witold , Listoś Tomasz
Published: April 2003

Poly(propylene carbonate) was treated with coordination catalysts exhibiting activity in propylene oxide/carbon dioxide copolymerization and cyclization. Poly(propylene carbonate) was found to undergo degradation and depolymerization reactions which were monitored by intrinsic viscosity of the polymer and the yield of propylene carbonate. End‐groups in the degraded polymer were determined using ultraviolet spectroscopy. Catalysts containing active phenolatozinc species were shown to cleave the poly(propylene carbonate) chain introducing to it the aryloxy moiety as aryl carbonate end‐group and the zinc moiety as alcoholatozinc end‐group. On the contrary, catalysts containing active alcoholatozinc species were shown to cleave the poly(propylene carbonate) chain introducing to it the alcoholate moiety as alcoholate end‐group and the zinc moiety as alkylcarbonatozinc end‐group. Propylene carbonate formation was proposed to occur involving chain depolymerization via alcoholatozinc end‐groups. Propylene carbonate formation involving chains terminated with alkylcarbonatozinc groups was proposed to be preceded by their decarboxylation with CO2 elimination leading to alcoholatozinc end‐groups.
Stimuli‐sensitivities of hydrogels containing phosphate groups
Authors: Miyata Takashi , Nakamae Katsuhiko , Hoffman Allan S. , Kanzaki Yoshio
Published: April 2003

The effect of an introduction of phosphate groups into hydrogels on their stimuli‐sensitivities has been investigated. Several hydrogels containing various phosphate group content were synthesized via solution copolymerization of 2‐(methacryloyloxy)ethyl dihydrogen phosphate (Phosmer) and 2‐hydroxyethyl methacrylate (HEMA) in the presence of 2,2′‐azoisobutyronitrile (AIBN) in methanol at 70°C for 4 h. The content of phosphate groups incorporated into the resulting hydrogels ranged from 1 to 13 mol‐%. The swelling ratio of these hydrogels was found to be strongly affected by pH, solvent, temperature and phosphate group content. The polymersolvent interaction parameter χ of the hydrogel was determined from the Flory‐Rehner equation, using the swelling ratio and the crosslinking density derived from the compression modulus. Furthermore, χ was divided into its enthalpic (χH) and entropic component (χS). Using the interaction parameter, the stimuli‐sensitivity of the hydrogel is discussed in detail based on thermodynamic aspects.
Synthesis and characterization of polymers bearing pyrazole groups, 1. Methacrylic derivatives
Authors: Boutevin Bernard , Guida‐Pietrasanta Francine , Malek Fouad
Published: April 2003

The synthesis of new methacrylic monomers H2CC(CH3)COOCH2G where G is a pyridine, a pyrazole or a bipyrazole group has been achieved. Their homopolymerization was studied and gave fairly low molecular mass polymers. Their copolymerization with styrene gave copolymers tending to be alternating when the bulkiness of group G increased. Moreover, in the presence of Lewis acids the monomers were complexed. With ZnCl2, they were complexed through nitrogen atoms and were shown to be inactive in copolymerization. With SnCl4, they were complexed through the carbonyl group and gave alternating copolymers. The homopolymers exhibited low glass transition temperatures (50–76°C) and moderate thermal stability (decomposition begins at ca. 200–280°C and is complete at 550°C). In the copolymers with styrene the thermal properties showed to be improved.
Determination of the partial specific volumes of thermoreversible gelatin/water and κ‐carrageenan/water gels
Authors: Cöulfen Helmut , Borchard Werner
Published: April 2003

In this paper systematic density measurements of gelatin/water and κ‐carrageenan/water gels are presented in a wide range of concentrations and temperatures. From about 600 measurements for gelatin/water and about 500 measurements for the system κ‐carrageenan/water empirical relations for both systems have been derived which allow to calculate the densities of these gels in a limited concentration range if the temperatures and the polymer weight fractions are known. The calculated densities have an accuracy of better than 0,001 g/cm−3 compared with the directly measured densities. If the extrapolated partial specific volumes of the pure polymer are plotted against the temperature, a jump with an inflexion point can be detected at about 23–24°C for both systems. These data indicate a Λ‐type transition of the expansion coefficient α for both systems at 23–24°C although there are still too few data to make clear conclusions.
Effects of soft segments and hydrolysis on the crystallization behavior of degradable poly(oxyethylene)/poly(L‐lactide) block copolymers
Authors: Hu David Shiaw‐Guang , Liu Hsin‐Jiant
Published: April 2003

The crystallization behavior of poly(oxyethylene) (PEG)/poly(L‐lactide) (PLLA) block copolymers with PEG (number‐average molecular weights Mn = 1000–6000) contents ≦ 18,3 wt.‐% has been studied under different isothermal temperature and linear cooling conditions. A differential scanning calorimeter was used to monitor the energetics of the crystallization process from the melt state. The influence of copolymer composition and hydrolysis on radial growth rates of spherulites, G, in PEG/PLLA copolymer was investigated using polarized light video‐microscopy. The data were analyzed in terms of a model describing two processes, namely crystal nucleation and growth which were observed experimentally in a typical Avrami plot for the isothermal data. At a given crystallization temperature, G's are increased with increasing PEG content and with decreasing PEG segment length in PEG/PLLA copolymer spherulites. The Avrami exponent n and rate coefficient k of PEG/PLLA copolymers decrease with increasing hydrolysis time up to 200 h. The spherulite morphology appeared to be a complex function of copolymer composition, hydrolysis time and crystallization temperature.
Shear influence on the phase separation of oligomer blends
Authors: Muniz Edvani C. , Nunes Suzana P. , Wolf B. A.
Published: April 2003

Shear influences on the phase separation behaviour of four different blends of ethylene glycol/propylene glycol oligomers, exhibiting upper critical solution temperatures, were investigated. Cloud point curves at rest (turbidity measurements) are reported for all systems, spinodal conditions (light scattering) and tie‐lines (analysis of the coexisting phases) are given for some examples. Phase diagrams under shear were obtained from rheological data. They demonstrate that the demixing temperatures of systems where both glycols bear OH end‐groups are lowered up to ca. 1°C by shear rates of 1000s−1; the critical composition, generalized to the non‐equilibrium conditions of flow, is markedly shifted. These observations are explained in terms of the generalized Gibbs energy (containing the mechanical energy the system stores during flow) as a consequence of the strongly interacting end‐groups of the glycols. This interpretation is backed by the fact that the shear effects disappear when the glycols are methylated.
Liquid‐crystalline main‐chain polymers with a poly(p‐phenylene terephthalate) backbone, 8. Synthesis and characterization of polyesters with 3‐ethoxypropoxy and 6‐(pentyloxy)hexyloxy side chains
Authors: Mercx Frans P. M. , Tinnemans Alois H. A. , Damman Sebastiaan B.
Published: April 2003

The influence of replacing a methylene group in the middle of the side chain of alkoxy‐substituted poly(p‐phenylene terephthalate)s by an oxygen atom was investigated by differential scanning calorimetry (DSC), rheological measurements and X‐ray diffraction. Due to the presence of the oxygen atom the side chains of the polymer with long side chains (PTA12(O)HQ) lose their ability to crystallize. Except for this difference and a shift of the transition temperatures to lower temperatures, this polymer shows a similar phase behaviour compared to the corresponding alkoxy‐substituted polyester PTA12HQ. The polymer with short side chains, PTA6(O)HQ, shows a similar behaviour as the corresponding polymer without an extra oxygen atom, PTA6HQ. Only the transition to the nematic mesophase is shifted to lower temperatures.
Preparation of surface‐modified polystyrene microspheres by an azo‐initiator having analogous structure to the head group of phosphatidylcholine
Authors: Sugiyama Kazuo , Ohga Koji , Kikukawa Kiyoshi
Published: April 2003

A novel azo‐initiator, 2‐[(2‐ethylphosphatoethyl)dimethylammonio]ethyl 4,4′‐azobis‐(4‐cyanovalerate) (EAP‐501), was prepared. EAP‐501 [m. p. 97°C (dec.), λmax 346 nm in H2O] was found to be amphiphilic, with a Krafft point of 11,5°C and a critical micelle concentration of 47,2 mmol·dm−3 at 30°C and 48,6 mmol·dm−3 at 70°C. The rate and activation parameters for the thermal decomposition of EAP‐501 at 70°C were estimated to be kd = 2,35·10−5 s−1, ΔH≠ = 118,4 kJ·mol−1 and ΔS≠ = 10,5 J·mol−1·K−1. Emulsion polymerization of styrene initiated with EAP‐501 gave polymer microspheres in high yield. The resulting polystyrene microspheres were characterized by transmission electron microscopy (TEM) and X‐ray photoelectron spectroscopy (XPS). The polystyrene microspheres have diameters from 321 to 649 nm by varying the EAP‐501 concentration. The ammonium phosphate groups, which are comparable to the polar head group of phospholipids, are concentrated on the surface of the particles. The particles were found to reduce the adsorption of bovine serum albumin (BSA) compared with particles prepared by the emulsion polymerization of styrene initiated with potassium persulfate as an initiator.
Liquid crystal elastomers: Influence of the orientational distribution of the crosslinks on the phase behaviour and reorientation processes
Authors: Küupfer Jürgen , Finkelmann Heino
Published: April 2003

The influence of the crosslinking conditions on the phase behaviour and reorientation processes of nematic elastomers is investigated. Two series of elastomers with various network anisotropies crosslinked either in the nematic or in the isotropic state were investigated by means of IR‐dichroism and stress‐strain measurements. The experimental results clearly demonstrate that for nematic elastomers not only the coupling between the network anisotropy and the state of order has to be considered. It is shown that the influence of the crosslinks and their orientational distribution on the phase behaviour, the state of order as well as on director reorientation processes cannot be neglected.
Copolymerization of olefins with SiO2‐, Al2O3‐, and MgCl2‐supported metallocene catalysts activated by trialkylaluminiums
Authors: Soga Kazuo , Kaminaka Manabu
Published: April 2003

Copolymerizations of ethylene with propene, of ethylene with 1‐hexene and of propene with 1‐hexene were carried out at 40°C under atmospheric pressure with SiO2‐, Al2O3‐ and MgCl2‐supported metallocene catalysts using common alkylaluminiums as cocatalyst. From a detailed analysis of copolymers by 13C NMR, all the copolymers obtained were found to be random (r1·r2 ≤ 1). When ethylene was used as a base monomer, the polymer yield markedly increased with increasing comonomer concentration. The molecular weight of the copolymers obtained in this study were found to be much higher than those obtained with homogeneous Kaminsky‐Sinn catalysts. Whereas, the polydispersity (Mw/Mn) of the copolymer is dependent on the combination of monomers as well as on the inorganic compounds used as carrier.
Phase separation in poly(methyl methacrylate)‐block‐poly(2,3‐dibromopropyl methacrylate) copolymers
Authors: Davy Kenneth W. M.
Published: April 2003

AB block copolymers poly(methyl methacrylate)‐block‐poly(2,3‐dibromopropyl methacrylate) were prepared by a two‐stage process involving the sequential anionic polymerization of methyl methacrylate and allyl methacrylate followed by bromination of the pendant allylic groups. Transmission electron microscopy of thin sections of cast films revealed phase separation, the morphology depending upon composition of the block. In particulate form these copolymers gelled with methyl methacrylate to form doughs that could be moulded and heat cured to produce hard X‐ray opaque copolymers.
Production of poly(β‐hydroxyalkanoates) with β‐substituents containing terminal ester groups by Pseudomonas oleovorans
Authors: Scholz Carmen , Fuller R. Clinton , Lenz Robert W.
Published: April 2003

Pseudomonas oleovorans was grown separately on the methyl, ethyl and tert‐butyl esters of octanoic, nonanoic and decanoic acid in attempts to obtain poly(β‐hydroxyalkanoates), PHAs, with ester groups at the terminal position of the β‐substituent. The growth rate increased from methyl to tert‐butyl esters, but the rate for the slowest growing substrates, the methyl esters, could be accelerated by using special feeding techniques, either by prefeeding with sodium acetate or by cofeeding with a good growth and polymer producing substrate, sodium octanoate. For the ethyl esters the prefeeding technique had minimal success, but a considerable increase of the growth rate was achieved by starting the bacterial growth with a pre‐culture that was grown on the substrate under investigation. Tert‐butyl nonanoate as the substrate gave the most rapid growth, but the growth rate was not influenced by special feeding techniques. All of these substrates formed copolymers which contained up to eight different repeating units and some had terminal ester groups on alkane side chains of varying lengths. The use of methyl esters as substrates resulted in the incorporation of a reasonably high degree of pendant methyl ester groups in the polymer produced, and the amount of repeating units carrying pendant ester groups dependend directly on the oxygen supply available to the bacterial culture. The fermentation of substrates with ethyl ester groups resulted in the formation of copolymers containing either unsubstituted units or units containing either ethyl or methyl ester groups, or both. The reason for this unexpected behavior was not clarified. The large tert‐butyl ester group was not maintained as a substituent group in the polymer, but instead, growth on this substrate always resulted in producing polymers consisting of the unsubstituted repeating units expected from the corresponding carboxylic acid alone.
Structural analyses of poly(m‐xylene‐α,α′‐diyladipamide) and nylon 66 by 15N solid state NMR
Authors: Yeo Joo‐Hong , Asakura Tetsuo , Shimazaki Hisashi
Published: April 2003

15N solid state NMR, viz. both 15N cross polarization (CP) NMR and 15N CP/magic angle spinning (MAS) NMR, is applied to the structural determination—including molecular orientation—of uniaxially oriented poly(m‐xylene‐α,α′‐diyladipamide) film and nylon 66 fiber on the basis of the chemical shift tensors. In the spectrum of a poly(m‐xylene‐α,α′‐diyladipamide) block sample whose fiber axis was set up parallel to the applied magnetic field, a single main peak with 20% powder pattern (non‐crystalline domains) was observed. The small difference in the structure of the main chain between these two uniaxially stretched polyamides was clarified from the chemical shift data of the parallel spectra which reflect the angle between the NH bond and the fiber axis. Determinations of the angles between various molecular‐fixed axes and the axis of polymer alignment were tried.
Modelling of size‐exclusion chromatograms from molecular weight distribution calculations. Application to the grafting of polymers onto functionalized silica
Authors: Guillot Jean , Leroux Denis
Published: April 2003

The objective of this paper is the modelling of the molecular weight distribution (MWD) and the polydispersity index (P. I.) of polystyrene grafted on porous silica beads prefunctionalized by a thiosilane molecule. Grafting occurs by a transfer reaction to the fixed mercapto groups. We have analysed the MWD of both grafted and ungrafted polymers by size‐exclusion chromatography (SEC). A good agreement between the experimental SEC diagrams and those calculated from the reaction rate constants is obtained with the following hypotheses: (1) the medium is a two‐phase system constituted of an interparticle phase and a porous intraparticle phase with a high local mercapto group concentration in the pores; (2) a higher transfer efficiency of the transfer agent in the pores (what could be attributed to a higher mobility of the very short chains inside the pores); (3) a lower termination rate in the pores, which results in a higher rate of polymerization than in the interparticle phase (probably due to an increase of the medium viscosity).
Nuclear magnetic resonance spectroscopic characterization of carboxymethylcellulose
Authors: Baar Andreas , Kulicke Werner‐Michael , Szablikowski Klaus , Kiesewetter René
Published: April 2003

Previous assignment of the signals in the spectra of carboxymethylcellulose, based on an incremental calculation and hence on low‐molar‐mass model substances, made determination of the partial degree of substitution fundamentally impossible because overlapping of the relevant signals was predicted. However, the methods of acid and enzymatic hydrolysis employed generate the monomer or a mixture of polymers, oligomers and monomers and hence a large number of end groups, which also influence the nuclear magnetic resonance (NMR) spectra. By using ultrasound, it was possible to degrade the molar mass (lower limit of molar mass approx. 100000 g/mol), without oligomers being generated and cleavage of side groups occuring. The viscosity of 10 wt.‐% polymer solutions was so low that the partial degree of substitution could be determined quantitatively for the first time. An additional 13C NMR spectroscopic examination of the acid hydrolysate enabled the composition of the eight monomers of sodium carboxymethylcellulose (NaCMC) to be determined in a degree of substitution (DS) range of 0,8–3,0. Knowledge of the monomer compositions is then used to reassign the signals of the polymer spectra, which are then evaluated. Comparison with titrimetric methods (polyelectrolyte titration and ASTM method) showed some wide discrepancies with the absolute method (NMR) in the case of samples with a DS greater than 1. The results of the 13C NMR spectroscopic examination of the acid hydrolysate were also used to determine the relative rate constants of the etherification reaction (k2:k3:k6 = 3,0:1,0:2,1), and these were then compared with published data.
Structure of polypropene and poly(ethylene‐co‐propene) produced with an alumina‐supported CpTiCl3/common alkylaluminium catalyst system
Authors: Soga Kazuo , Uozumi Toshiya , Saito Masayoshi , Shiono Takeshi
Published: April 2003

Both propene polymerization and ethylene/propene copolymerization were conducted with an Al2O3‐supported CpTiCl3 (Cp: cyclopentadienyl) catalyst using a common alkylaluminium as cocatalyst. The catalyst system gave atactic polypropene with frequently inverted propene units which are randomly distributed over the polymer chain. The structure of poly(ethylene‐co‐propene) produced with the catalyst system was found to be very different from that obtained with ordinary titanium based catalysts.
Fractionation of polypropylene according to molecular weight and tacticity
Authors: Lehtinen Arja , Paukkeri Ritva
Published: April 2003

Different extraction techniques were applied to the fractionation of isotactic polypropylene. In solvent gradient extraction experiments two different solvent/non‐solvent systems were studied. Investigation of the fractions obtained by GPC, DSC and FTIR indicated that the fractionation proceeded according to molecular weight when ethylene glycol monobutyl ether/diethylene glycol monobutyl ether was used as a solvent/non‐solvent system at 159–161°C. The fractions covered a broad molecular weight range, had narrow molecular weight distribution and showed only small variations in their isotacticity. Xylene/ethylene glycol monoethyl ether combination at 121–128°C separated polypropylene in fractions mainly according to stereoregularity, the separation being less dependent on molecular weight. A large number of fractions with varying stereoregularity could be produced. Successive extraction with solvents of increasing boiling temperature gave fractions differing both in molecular weight and isotacticity, and was the only method to separate the stereoblock copolymer. Comparison of heptane extractables and xylene solubles methods showed differences in the structure and molecular weight of heptane and xylene soluble fractions and heptane and xylene insoluble fractions, respectively.
Liquid‐crystalline polysulfones, 4. Radiation‐induced degradation
Authors: Braun Dietrich , Arnold Norbert , Schmidtke Ingrid
Published: April 2003

Polysulfones are degraded by high‐energy radiation with highly specific bond scission of the main chains. The effect of γ‐ and electron‐beams on selected liquid‐crystalline polysulfones was determined. The radiation‐induced degradation of polysulfones by elimination of the monomers can be used for electro‐optical displays.
(Co)polymers of L‐lactide, 2. Mechanical properties
Authors: Grijpma Dirk W. , Pennings Albert J.
Published: April 2003

The effect of copolymerization of L‐lactide with several lactones and cyclic carbonates and the processing variables in compression moulding of poly(L‐lactide) homopolymers on the mechanical properties was investigated. Sharp maxima in the impact strength versus comonomer composition and heat of fusion were obtained, reflecting the important role of the presence of a crystalline fraction in the material. Crystalline domains increase the interconnectivity of a physical polylactide network and decrease the molecular weight between these physical crosslinks. The brittle strength concomitantly increases, and as the yield stress remains more or less constant, an increase in impact strength is observed. Very high crystalline as‐polymerized poly(L‐lactide) prepared with less active catalysts on the other hand has an extremely low entanglement density and therefore a low brittle tensile strength.
Synthesis and characterization of ether‐type chitin derivatives
Authors: Kim Seon Jeong , Kim Seong Soo , Lee Young Moo
Published: April 2003

Novel ether‐type chitin derivatives were synthesized by reacting alkali salts of chitin with 1‐chloropropane, propylene oxide and 3‐chloro‐1,2‐propanediol to prepare propylchitin (PPC), hydroxypropylchitin (HPC) and dihydroxypropylchitin (DHPC), respectively. The structures of these chitin derivatives were confirmed by FT‐IR and solid state CP/MAS 13C NMR spectrometry. The substituents are introduced primarily at the C6 position of the glucosamine unit in chitin, with a degree of substitution of approx. 30–50%. The three chitin derivatives are soluble in weakly acidic aqueous solutions, DHPC even in pure water.
Solvent effect on the methacrylic acid‐methyl methacrylate radical copolymerization. Analytical estimation by linear and nonlinear solvation energy relationships
Authors: Georgiev Georgi S. , Dakova Ivanka G.
Published: April 2003

The calculated methacrylic acid‐methyl methacrylate monomer reactivity ratios in toluene (rMA = 1,06 ± 0,02; rMMA = 0,10 ± 0,01), isopropyl alcohol (rMA = 0,33 ± 0,02; rMMA = 0,78 ± 0,03), acetone (rMA = 0,63 ± 0,02; rMMA = 0,31 ± 0,02) and acetonitrile (rMA = 0,46 ± 0,03; rMMA = 0,27 ± 0,03) depend strongly on the polarity, proton donor and proton acceptor ability of the solvent. It is proved that the solvent influence on the logarithm of the relative comonomer reactivities is expressed much better by the linear relationships of the solvatochromic polarity, proton donor and proton acceptor indexes than by the dependences reflecting these effects individually. The possibility of a statistically confident description of the complex solvent influence on the comonomer reactivities by quadratic solvatochromic relationships taking into account the interdependence of solvent effects is shown for the first time.
Chemical synthesis and complexing behaviour of branched cyclodextrins composed of an amylose and a β‐cyclodextrin residue
Authors: Kubik Stefan , Wulff Günter
Published: April 2003

The synthesis of a new class of branched cyclodextrins is presented. In these compounds an amylose residue with a degree of polymerization (DP) of 30 is attached to the C6 position of a β‐cyclodextrin molecule via an alkyl spacer. Hence, these hosts are composed of a combination of two different components linked covalently, both having individual properties. The complexing behaviour was investigated by circular dichroism (CD) spectroscopy. The CD spectra indicate that the inclusion geometry of some guest compounds into the β‐cyclodextrin cavity is influenced by the amylose side chain. However, an additional complexation of these guests inside the amylose helix was not observed.
Orientational distribution in stretched poly(methyl methacrylate) from 13C NMR spectroscopy
Authors: Kulik Andrzej S. , Spiess Hans Wolfgang
Published: April 2003

The orientational distribution in drawn amorphous poly(methyl methacrylate) extended to the ratio λ = 3 was measured with one‐ and two‐dimensional carbon‐13 NMR spectroscopy. In the analysis, signals from the carboxyl carbons were used as a probe of the orientational distribution. The angular‐dependent line shapes were analyzed to determine the orientational distribution function and the order parameter 〈P2〉. The analysis yielded 〈P2〉 = 0,21. A two‐dimensional rotor‐synchronized magic angle spinning experiment was also used to measure the order parameter. The obtained value 〈P2〉 = 0,22 is in excellent agreement with the 1D result. The experimental results obtained for 〈P2〉 are compared to those proposed by the pseudo‐affine model. 〈P2〉 predicted by theory is reduced due to conformational disorder present in the glassy state.
On the polymerization of N,N,N′,N′‐tetramethyl‐α,ω‐alkanediamines with dibromoalkanes—an in‐situ NMR study
Authors: Wang Jianguo , Meyer Wolfgang H. , Wegner Gerhard
Published: April 2003

Based on the Menschutkin reaction, α,ω‐alkanediamines with α,ω‐dibromoalkanes were employed to synthesize cationic polyelectrolytes named ionenes. By means of in‐situ 13C NMR we have characterized the influence of ionic charges on the reactivity of the polymerizing species. The progress of aliphatic ionene polymerization has been found to be a complex reaction. At least four elementary building reactions and two side reactions (Hoffmann degradation and intramolecular cyclization) have been detected in the course of ionene polymerization. As a result, the broad molecular weight distribution which is usually found in ionenes can be explained in terms of the kinetics and by side reactions. Also, the difficulty of achieving high molecular weight ionenes can be understood on the basis of our NMR results.
Calorimetric study of 5‐trimethylsilyl‐2‐norbornene, of its polymerization process and of poly(5‐trimethylsilyl‐2‐norbornene) from 5 to 600 K at standard pressure
Authors: Lebedev Boris , Smirnova Natal'ya , Novosyolova Nina , Makovetskii Kiryll , Ostrovskaya Irina
Published: April 2003

Thermodynamic properties of 5‐trimethylsilyl‐2‐norbornene (TMSNB) and poly(5‐trimethyl‐silyl‐2‐norbornene) (PTMSNB), viz. the temperature dependence of the isobaric heat capacity Cop of the monomer between 10 and 330 K and of the polymer from 7 to 600 K, were studied by adiabatic vacuum and differential dynamic calorimetry. Temperature and enthalpy of monomer melting as well as parameters of glass transition and glassy state of the monomer and the polymer were determined. From the experimental data, the thermodynamic functions H°(T)‐H°(0), S°(T) and G°(T)‐H°(0) were calculated for TMSNB in the range of 0 to 330 K and for PTMSNB from 0 to 380 K. In a differential automatic calorimeter, the enthalpy of polymerization of TMSNB to PTMSNB in toluene solution was measured at T = 301 K and p = 101,325 kPa. Under similar physical conditions and in the same calorimeter, enthalpies of dissolution for the monomer and the polymer were estimated. The results were used to calculate the enthalpy, entropy and Gibbs function of bulk polymerization of TMSNB in the range of 0 to 380 K at standard pressure. The ceiling temperature of the polymerization process was also evaluated.
Iridescent coloration of a copolymer gel in an organic solvent
Authors: Gong Jianping , Okuzaki Hidenori , Osada Yoshihito
Published: April 2003

A polymer gel formed from acrylic acid and methyl acrylate, moderately swollen in toluene or benzene, exhibits iridescent coloration. The color changes with temperature and composition of the gel. This phenomenon has been associated with specific scattering of light.