bluuebunny/crossref_metadata_2025 huggingface dataset:
Dilute solution properties of well‐defined multiblock copolymers: poly(4,4′‐isopropylidenediphenyl carbonate)‐block‐polystyrene
Authors: Dems Andrzej , Strobin Graz̊yna
Published: April 2003

Light scattering, osmometric and viscometric studies were carried out with dilute solutions of well‐defined poly(4,4′‐isopropylidenediphenyl carbonate)‐block‐polystyrene multiblock copolymers, PC‐b‐PS, in non‐selective and selective solvent systems. The influence of copolymer composition, numbers and lengths of blocks in the copolymer chain and type of solvent used on the dilute solution properties, conformation of the investigated multiblock copolymers and on some thermodynamic parameters are discussed. The intrinsic viscosity [η], the unperturbed dimension 〈R02〉/Mand the second virial coefficientA2are larger in non‐selective solvents than expected from the averaged values of the parent homopolymers. In benzene, a selective solvent for polystyrene, formation of micelles is possible.
Pressure dependence of viscometric relaxation times measured with a new apparatus. Williams‐Landel‐Ferry behaviour of moderately concentrated solutions of poly(butyl methacrylate)s in 2‐propanol
Authors: Geerissen Heinz , Gernandt Friedhelm , Wolf B. A. , Lentz Harro
Published: April 2003

A new rotational viscometer is presented which can be operated up to 2 000 bar and a maximum shear stress of 420 Pa. It allows, for the first time, to investigate the non‐Newtonian flow behaviour of moderately concentrated polymer solutions. Results of measurements with two representatives of the system 2‐propanol/poly(butyl methacrylate) with weight‐average molecular weights M̄w = 520 000 and M̄w = 2 050 000, and ratios of weight‐ to number‐average molecular weights M̄w/M̄n = 1,08 and M̄w/M̄w = 1,23, resp. in the region of moderate polymer concentrations are reported. For a ca. 7 wt.‐% solution of the higher‐molecular‐weight polymer one obtains viscometric relaxation times τ0 varying from 1 to 100 ms in the region from 1 to 2 000 bar and from 40 to 75°C; at the lower temperature the application of p can raise τ0 by one order of magnitude. The steady‐state shear compliance (proportional to τ0/η0, where η0 is the zero‐shear viscosity), is independent of pressure of varies only slightly. For the present system, which gels thermoreversibly upon cooling, η0 and τ0 as a function of temperature and pressure can be well represented by the Williams‐Landel‐Ferry equation.
Photoresponsive liquid crystals prepared from poly(biphenylyl vinyl ether‐alt‐maleic anhydride)s
Authors: Ikeda Tomiki , Hasegawa Shoichi , Sasaki Takeo , Miyamoto Takeshi , Lin Mao‐Peng , Tazuke Shigeo
Published: April 2003

Photoresponsive groups (azobenzene and cinnamic acid derivatives) were incorporated into alternating copolymers of maleic anhydride and vinyl ethers with pendant 4′‐methoxy‐4‐biphenylyl moieties bound via ethylene glycol spacers. The resulting polymers were examined with respect to their liquid crystalline behavior and photochemical reactivity in relation to the isothermal phase transition behavior.
Catalysts for syndiotactic‐specific polymerization of styrene: A tentative interpretation of some experimental data
Authors: Zambelli Adolfo , Pellecchia Claudio , Oliva Leone , Longo Pasquale , Grassi Alfonso
Published: April 2003

The experimental data available in the literature concerning syndiotactic‐specific polymerization of styrene and the data reported in this paper, mainly concerning the comparison of the behaviour of different catalytic systems, lead to the tentative suggestion that the true catalytic species might be complex cations similar to those involved in α‐olefin polymerization.
Monomer‐isomerization polymerization, 27. Monomer‐isomerization in competition with polymerization of α‐olefins with Ziegler‐Natta catalysts
Authors: Endo Kiyoshi , Otsu Takayuki
Published: April 2003

The monomer‐isomerization was studied in the polymerization of α‐olefins with the catalytic systems TiCl3/(C2H5)3Al and Ti(OC4H9)4/(C2H5)3Al. The isomerization to the corresponding olefins with internal double bond was found to occur during the polymerization. With the system TiCl3/(C2H5)3Al only a small amount of isomerized olefin was produced as result of the rapid polymerization of the α‐olefins. Significant isomerization was observed to take place with a poor polymerization catalyst such as Ti(OC4H9)4/(C2H5)3Al. Isomerization and polymerization of α‐olefins with Ziegler‐Natta catalysts were found to depend on the oxidation state of titanium.
On the reactivity of styryl‐terminated polystyrene macromonomers in anionic copolymerization with butadiene
Authors: Arnold Manfred , Frank Willy , Reinhold Günther
Published: April 2003

Styryl‐terminated polystyrene macromonomers (MA) with molar masses ranging from M̄n = 1 600 to 38 000 g/mol were copolymerized with butadiene (B) by application of the initiator system butyllithium/sodium tert‐butoxide in cyclohexane. The temporal insertion of both monomers into the growing graft polymer chain was observed by means of size‐exclusion chromatography and gravimetrical analysis. The values of 1/rB = kBMA/kBB (kBMA, kBB: rate constants of MA and B insertion, respectively) show that the reactivity of the macromonomers is clearly influenced by their molar mass, the conversion of butadiene, and thus by the obtained molar mass of the growing graft polymer as well as by the mole ratio of the macromonomer and comonomer in the reaction mixture. An almost “ideal” insertion was observed for macromonomers with molar masses of up to about M̄n = 5000 g/mol and a conversion of about 50%. An increase in the values of molar mass, conversion and concentration of the macromonomers has the effect of lowering 1/rB.
Polymer‐supported rare‐earth catalysts for polymerization of styrene
Authors: Zhao Jian , Yang Mujie , Zheng Yi , Shen Zhiquan
Published: April 2003

A neodymium complex supported on an ethylene‐vinyl alcohol copolymer (EVA · Nd) was prepared for the first time and the polymerization of styrene in the presence of a new type of catalyst system composed of this complex was studied. The new catalytic system [EVA · NdAl(i‐Bu)3CCl4] (i‐Bu = isobutyl) is characterized by its catalytic activity in comparison with that of conventional rare‐earth catalysts. When [Nd] = 10−3 mol/L, [Styrene] = 5 mol/L, [Al]/[Nd] = 120 and [CCl4]/[Nd] = 35, then the conversion to polystyrene (PS) was 55% in 6 h, and the catalytic activity reached 1972 g PS/g Nd which is higher by a factor of 45 than that of conventional rare‐earth catalysts. The polymerization reaction shows a short induction period where the rate is first order with respect to the monomer concentration. The activation energy is 27,6 kJ/mol. This polymerization may proceed according to a free‐radical or a Ziegler‐type coordination mechanism.
Synthesis and ring‐opening polymerization of 1,4:2,5:3,6‐trianhydro‐D‐mannitol and structure studies by MNDO calculations
Authors: Strietholt Wilhelm A. , Thiem Joachim , Höweler Udo F. B.
Published: April 2003

Base‐catalyzed intramolecular nucleophilic substitution of various dianhydrosorbitol derivatives (2, 4, or 6) led to formation of trianhydromannitol (7), a tricyclic system of three interlinked oxolane rings. By treatment with trifluoromethanesulfonic acid, ring‐opening reactions were achieved to give oligomeric soluble material with a number‐average degree of polymerization \documentclass{article}\pagestyle{empty}\begin{document}$ \overline {DP} _n \approx 5 - 10 $\end{document} Molecular weights were determined by GPC, and by desorptive chemical ionization (DCI) with ammonia a molecular weight assignment gave information on the degree of crosslinking. A complex but consistent picture allows to explain the propagation reactions of protonated trianhydromannitols 8 and 9, and further reactions of the protonated intermediates 13–15 to result in crosslinked products 16 and 17. By semiempirical quantum chemical calculations, geometries, energies and charge distributions of 7 as well as its protonated species were obtained. This allowed comparisons with their chemical reactivity and ring‐opening specificity.
Nouveaux copolymères alternés préparés à partir du dicyanure de propène‐1 ylidène‐1 avec le styrène et la vinyl‐1 pyrrolidone‐2
Authors: Monthéard Jean‐Pierre , Boinon Bernard , Rodriguez Firmin , Pham Quang‐Tho , Waton Hugues
Published: April 2003

A trisubstituted ethylene, 1‐propene‐1‐ylidene dicyanate has been prepared via Knoevenagel reaction of acetaldehyde and malonitrile with β‐alanine as a catalyst. This product has been copolymerized in bulk — with 2,2′‐azoisobutyronitrile as an initiator — with styrene and 1‐vinyl‐2‐pyrrolidone. Preliminary 1H and 13C NMR studies of the copolymers are in good agreement with an alternating structure besides minor proportions of homopolymers of styrene or 1‐vinyl‐2‐pyrrolidone. The propagation mechanism has also been studied with 1H‐1H correlation spectroscopy.
Molecular‐weight distributions in the thermally initiated emulsion polymerization of styrene
Authors: Said Ziad F. M.
Published: April 2003

In both thermal emulsion polymerization of styrene in the temperature range 60–80 °C, and peroxodisulfate‐initiated polymerization at 60 °C, weight‐average to number‐average molecular‐weight ratios (M̄w/M̄n) approach 1,5 when potassium octadecanoate is used as emulsifier. A low activation energy for thermal initiation (≈66,0 kJ/mol) was deduced which may indicate a catalytic effect of the emulsifier during the thermal initiation process. Participation of the emulsifier is probably attributed to a transfer of one of two monomer radicals, produced thermally, to the emulsifier, with subsequent desorption to the aqueous phase, leaving one radical in the polymerization locus.
Hypochromy in polystyrene systems
Authors: Kowal Joanna , Jamróz Dorota
Published: April 2003

The hypochromy of polystyrenes of different degrees of isotacticity in relation to ethylbenzene, and of isotactic polystyrene in relation to atactic polystyrene, was estimated. All polymers showed hypochromy, ca. 2% in case of atactic polystyrene and 5–9% in case of isotactic polystyrene. One may conclude that the helical regions of the solid polymers are partly retained in solution.
Binding of dyes by teichoic acid in competition with other polyanions
Authors: Pal Medini Kanta , Ghosh Tapash Chandra
Published: April 2003

When a cationic dye is added to a mixture of different anionic polymers, the dye will be distributed amongst them according to the binding strengths of the polymers. In such a competitive binding, DNA uses its intercalation ability to win the competition, provided the ligand can be intercalated within the DNA base pairs. For poorly or non‐intercalating ligands like 1,9‐dimethyl‐methylene blue or pinacyanol, the effective mode of binding is only electrostatic. For such ligands the strong polyelectrolyte poly(styrene sulfonate) wins the competition for cationic dyes, as shown by spectroscopic and dichroic probes. The results of the competitive binding of pinacyanol between the two weak chromotropes teichoic acid and DNA are not distinctly indicative, but the dichroic probe hints at a relatively stronger chromotropic ability of DNA.
Sulfonation of low‐density polyethylene films. Infrared absorption coefficients for the sulfonic group
Authors: Arribas Carmen , Rueda Daniel R.
Published: April 2003

The chemical modification of the surface of low‐density polyethylene films exposed to an atmosphere of fuming sulfuric acid for different periods of time has been investigated. The degree of surface sulfonation for each treated film was calculated as the weight‐increase per unit area. The correlation of the absorbance of infrared bands associated to the sulfonic group with the degree of sulfonation of the films allowed to determine the IR absorption coefficients, especially for the band at 1 040 cm−1.
Some spectroscopic evidence on deformation mechanisms in elastomeric networks at very high elongations
Authors: Silva L. K. , Mark J. E. , Boerio F. J.
Published: April 2003

Bimodal elastomeric networks are unusually tough materials in that they generally show large increases in modulus at high elongations. In the present study such networks were prepared by end‐linking mixtures of very short and relatively long chains of poly(dimethylsiloxane) (PDMS) [Si(CH3)2O]n, which is known to have easily deformable SiOSi bonds. Their stress‐strain isotherms were then determined in order to locate the range of elongations over which the upturns were most pronounced. Raman and infrared spectra were then obtained in this range using both a double monochromator Raman spectrophotometer and a Fourier transform infrared spectrophotometer with attenuated total reflection. The elongations imposed were found to cause small but not negligible frequency shifts for the stretching and bending modes of the SiOSi backbone. These shifts are probably due to rotational isomerization of the PDMS skeletal bonds, but there could also be a small contribution from bond‐angle deformations. The results thus support the usual assumption that the increases in modulus observed for bimodal networks are primarily due to the very limited number of spatial configurations available to the short network chains, particularly in the case of chains having skeletal bonds that are less easily deformed than those in PDMS.
A new class of highly reactive acrylic monomers, 2. Light‐induced copolymerization with difunctional oligomers
Authors: Decker Christian , Moussa Khalil
Published: April 2003

Acrylic monomers containing a cyclic carbonate group in their structural unit have been shown to copolymerize very rapidly and extensively with urethane and phenoxy oligomers having two acrylic functional end groups. With the most reactive resin, 90% conversion was reached within 20 ms of UV exposure in the presence of air. The kinetics of these ultrafast polymerizations was studied by infrared spectroscopy and their actual profiles were recorded in real time by RTIR spectroscopy. The rate of polymerization and the amount of residual unsaturation were determined for the three monomers studied, and compared to the performance of the mono‐, diand triacrylates commonly used as reactive diluents in UV‐curable systems. Quantum yield measurements indicate a very efficient propagation reaction, with kinetic chain lengths in the order of 104 mol per initiating radical, even in the presence of air. The crosslinked polymers obtained with these new monomers exhibit both a great hardness and a high flexibility, together with a good resistance to organic solvents, chemicals and UV radiation, which makes them well suited for applications as protective coatings.
X‐ray diffraction characterization of amorphous poly(propylene)
Authors: Marigo Antonio , Marega Carla , Zanetti Enrico , Zannetti Roberto , Paganetto Guglielmo
Published: April 2003

The differential radial distribution functions of a sample of amorphous (atactic) poly(propylene) and of an isotactic one were compared, showing the absence, in the former sample, of interatomic correlations beyond 8 Å (1 Å = 0,1 nm). The influence of the length of atactic and isotactic chain segments on the calculated X‐ray interference functions was investigated. A model based on the arrangement of atactic chains in close‐packed spheres fits well the experimental X‐ray diffraction pattern of the amorphous sample.
Study on dipole moments of macromolecules, 3. Dipole moments of poly(4‐methoxystyrene) and poly(4‐bromostyrene) and their dependences on solvent and temperature
Authors: Shima Mikiko , Yamaguchi Noriko , Sato Mari
Published: April 2003

Dipole moments of poly(4‐methoxystyrene) (PMeOSt) and poly(4‐bromostyrene) (PBrSt) were determined from dielectric constant and density measurements on dilute solutions of the polymers in benzene, 1,4‐dioxane and toluene, over the range of temperatures from 25 to 55°C. The average dipole moments per constitutional repeating unit (μ) obtained in benzene (Bz), 1,4‐dioxane (Dox), and toluene (Tol) at 25°C are as follows: 1,219 D (Bz), 1,253 D (Dox) and 1,175 D (Tol) for PMeOSt, and 1,371 D (Bz) and 1,413 D (Dox) for PBrSt

In SI units: 1 D ≈ 3,33564 · 10−30 C · m.

. The dipole moment ratio, Dr = 〈μ2〉2/μ20, was found to be 0,942 for PMeOSt and 0,467 for PBrSt in Bz at 25°C, for which the observed values of the dipole moments of 4‐methoxytoluene and 4‐bromoethylbenzene were used as μ0 for the respective polymer. The variation of the dipole moment ratio with temperature was linear but very small, dDr/dT giving a negative value for PMeOSt but a positive value for PBrSt.
Biaxial and uniaxial extension studies of polydimethylsiloxane networks prepared by end‐linking in solution
Authors: Xu Ping , Mark James E.
Published: April 2003

Polydimethylsiloxane chains were tetrafunctionally end‐linked with tetraethoxysilane in solution, with either a linear dimethylsiloxane oligomer or hexadecane as solvent. Stress‐strain isotherms for the networks thus prepared were obtained in the extracted but unswollen state, both in elongation and in compression (biaxial extension, which was achieved by inflation of sheets of the materials). Measurements were carried out to the rupture points in order to provide as large a range of deformation as possible. Comparison of the experimental and theoretical stress‐strain isotherms indicated that the experimental results were in good agreement with the constrained junction theory of rubberlike elasticity. The results showed that the constraint parameter k decreases with decrease in the volume fraction v2c of polymer present during cross‐linking and incorporated into the network structure, which means that networks prepared at high dilutions have fewer chain‐junction entanglements, as expected. However, the experimental values of the phantom modulus [f] are also a function of the weight fraction of soluble (uncross‐linked) polymer which had been present. This confirms the expectation that networks prepared at high dilutions have imperfections such as loops and dangling ends. There is an excellent agreement, however, between experiment and theory with respect to the relationships among k, the Mooney‐Rivlin 2C1 estimate of the phantom modulus, and v2c.
Cationic polymerization of vinyl monomers with latent initiators, 3. 1‐(p‐methoxybenzyl)tetrahydrothiophenium hexafluoroantimonate as a new potent cationic initiator
Authors: Kikkawa Atsushi , Takata Toshikazu , Endo Takeshi
Published: April 2003

Cationic polymerization of styrene in the presence of 1‐(p‐methoxybenzyl)tetrahydrothiophenium hexafluoroantimonate (3) as an efficient cationic initiator was investigated. 3 was synthesized in an excellent yield by the reaction of p‐methoxybenzyl bromide with tetrahydrothiophene and the subsequent exchange of bromide ions for hexafluoroantimonate ions. In the polymerization of styrene, 3 acted as a potent thermally latent initiator which initiates the polymerization at a slightly higher temperature than room temperature, although no polymerization occurs at room temperature for 30 min. 3 is a much more active initiator than the previously reported benzylsulfonium salt 1. The enhanced activity of 3 was also confirmed in the polymerization of glycidylb phenyl ether.
Constitutional isomerism in step‐growth polymers: Theoretical aspects of systems with two nonsymmetric monomers
Authors: Gentile Frank T. , Suter Ulrich W.
Published: April 2003

A model was developed to determine the constitution of step‐growth polymers synthesized from the nonsymmetric monomers XabX and YcdY under various modes of mixing. Depending upon the inherent kinetics of the system and the modes of addition of monomers, polymer constitution can be varied over wide ranges. Results are shown for single‐stage polymerizations with all variations of kinetic parameters and mixing modes. The results show that the synthesis of truly “random” polymers is very difficult with this monomer system.
New approach to dextran derivatives containing primary amino functions
Authors: Vandoorne Filip , Bruneel Dorine , Vercauteren Ronny , Schacht Etienne
Published: April 2003

Dextran derivatives containing primary amino functions were prepared by reacting 4‐nitrophenyl carbonate‐substituted dextran with the mono‐protected diamine N‐tritylenediamine (7). Acidic treatment of the resulting dextran N‐[2‐(N‐trityl)aminoethyl]carbamate (8) yields dextran N‐(2‐aminoethyl)carbamate (5a). Alternatively, aminodextran derivatives were prepared by adding 4‐nitrophenyl carbonate‐substituted dextran to a large excess of a diamine or a triamine.
Solution properties of poly(octadecyl methacrylate) in butyl acetate, 1. Dilute Solution
Authors: Ricker Mathias , Schmidt Manfred
Published: April 2003

Dilute solutions of poly(octadecyl methacrylate) (PODMA) obtained by radical‐initiated polymerization were inverstigated in the theta‐solvent butyl acetate (BuAc) by static (SLS) and dynamic light scattering (DLS) and viscometry at six different temperatures between 11°C (near the theta‐temperature Θ) and 30°C. The mass‐average molar masses ranged from M̄w = 6,2 · 105 g · mol−1 to 3,2 · 106 g · mol−1. It was found that PODMA in BuAc behaves in general as expected for linear flexible Gaussian coils in a theta‐solvent. The Kuhn length was determined to be 35 Å. At temperatures slightly above Θ = 10,5°C the exponents of the intrinsic viscosity, radius of gyration and hydrodynamic radius versus molar mass relationships lie significantly below 0,5, the expected value for flexible linear chains at theta‐conditions. Qualitatively, these findings are explained by a coil contraction due to the different chemical nature of the main chain and the side chains and therefore different polymer‐solvent interactions of different parts of the molecules.
Polymer diffusion in mixtures of polystyrene and polymethylstyrene studied by forced rayleigh scattering and photon correlation spectroscopy
Authors: Wesselmann Manfred , Sillescu Hans
Published: April 2003

Tracer diffusion coefficients D* of both components were measured in mixtures of polystyrene (PS) and polymethylstyrene (PMS), a random copolymer from 60 wt.‐% of m‐methylstyrene and 40 wt.‐% of p‐methylstyrene. The results are interpreted in terms of the free‐volume theory which yields master curves even for “asymmetric” mixtures of oligomer and polymer chains, if D* is drawn versus the distance from the glass transition temperature, T–Tg. Whereas D* was measured by the forced Rayleigh scattering technique, we also studied photon correlation spectroscopy in these mixtures and observed “slow modes” with decay constants that correspond to diffusion coefficients 2–3 decades smaller than the interdiffusion coefficient.
External alkoxysilane donors in Ziegler‐Natta catalysis. Effects on poly(propylene) microstructure
Authors: Härkönen Mika , Seppälä Jukka V. , Väänänen Taito
Published: April 2003

Correlations were sought between the structure of an external alkoxysilane donor and the microstructure of the polymer chain obtained by the polymerization of propene with a heterogeneous, high‐activity Ziegler‐Natta catalyst. Fourteen different alkoxysilanes of structure RnSi(OR′)4‐n, where n = 1–3, R = n‐alkyl or phenyl and R′ = C1–3‐alkyl, were used as external donors. The polymers were fractionated by boiling heptane extraction. The microstructures of the polymers were studied by means of 13C NMR spectroscopy. The structure of the donor had a marked effect on the catalyst activity and isotacticity of the polymer. However, all of the alkoxysilanes tested produced qualitatively similar differences in the microstructure of poly(propylene): the size of the isotactic mmmm pentad peak varied with the donor efficiency, but the sizes of the non‐isotactic pentad peaks were more or less constant relative to each other. In the boiling heptane soluble fraction, isotacticity and syndiotacticity increased and the viscosity‐average molecular weight M̄v decreased when a good external donor was used in the polymerization. Results indicate that all external alkoxysilane donors tested have the same qualitative effect on active centers, and only isotacticity, i.e., the number of mmmm sequences, can be controlled by an external alkoxysilane donor. The effectiveness and selectivity of deactivation strongly depend on the structure of the donor.
Kinetics of the anionic polymerization of ϵ‐caprolactone with K+ · (dibenzo‐18‐crown‐6 ether) counterion. Propagation via macroions and macroion pairs
Authors: Sosnowski Stanislaw , Slomkowski Stanislaw , Penczek Stanislaw
Published: April 2003

Following our earlier work on the polymerization of lactones involving crowned cations, kinetics of the anionic polymerization of ϵ‐caprolactone (ϵCL) with K+ · (dibenzo‐18‐crown‐6 ether) (K+DB18C6) counterion was studied calorimetrically in THF solution in the temperature range from 0 to 20°C. Dissociation constants of CH3(CH2)5O−K+DB18C6, modelling the active centers, were determined conductometrically: KD (20°C) = 7,7 · 10−5 mol · dm−3, ΔH = 9,3 ± 0,2 kJ · mol−1, ΔS = −47 ± 2J · mol−1 · K−1. From kinetic measurements and from measurements of the dissociation constant of CH3(CH2)5O− K+DB18C6, rate constants of propagation via macroions and via macroion pairs were determined. Activation parameters for propagation via these species are equal to: ΔH = 39,2 ± 0,2 kJ · mol−1, ΔS = −63 ± 1 J · mol−1 · K−1, ΔH = 13,7 ± 0,1 kJ · mol−1, ΔS = −185 ± 2 J · mol−1 · K−1. At 20°C, k = 3,50 · 102 dm3 · mol−1 · s−1 and k = 5,2 dm3 · mol−1 · s−1. Due to the large difference of ΔH≠ for propagation via macroions and macroion pairs (vide supra), the isokinetic point (k = k) would appear at −65°C.
Polymers with pharmacological activity, 5. Hydrolytical behaviour of polymethacrylic hydrogels bearing “paracetamol” side groups
Authors: Levenfeld Belén , Román Julio San , Bunel Claude , Vairon Jean‐Pierre
Published: April 2003

The heterogeneous hydrolytical behaviour of hydrogels based on copolymers of 2‐hydroxyethyl methacrylate (HEMA) with 4‐(methacryloyloxy)acetanilide (MOA)b is analyzed by measuring the concentration of active metabolites released into the alkaline‐buffered solution used as the hydrolytical medium. Previously, we studied the swelling of hydrogel matrices of copolymers prepared with a MOA content between 1,0 and 5,0 wt.‐%, in order to know the diffusional character of the reagents and the released species. The results obtained demonstrate that the swelling phenomenon is much faster than the hydrolytical chemical reaction. Thus, the hydrolysis is studied on the basis of a kinetic scheme which considers the formation of different kinds of residues, i.e., the sodium salts of 4‐hydroxyacetanilide (PC) and 4‐aminophenol (PA), according to the UV spectra obtained at different times of treatment. The characteristic rate coefficients, k1, k2, kc and k′c are evaluated from the experimental data on the basis of the suggested kinetic scheme.
Grafting of acrylonitrile to poly(styrene‐co‐acrylonitrile) by transformation with a titanium catalyst
Authors: Menceloğlu Yusuf Z. , Güngör Attila , Baysal Bahattin M.
Published: April 2003

Poly(styrene‐co‐acrylonitrile)‐graft‐polyacrylonitrile graft copolymers were prepared using a mixed (free‐radical Vanionic) mechanism technique. For this purpose, poly(styrene‐co‐acrylo‐nitrile) random copolymers which contain different amounts of acrylonitrile segments were regarded as saturated high‐molecular‐weight nitrile compounds and were allowed to react with tetrakis(dimethyl amino)titanium. By this treatment pendant nitrile groups were transformed to organometallic active sites. These active groups lead to the polymerization of acrylonitrile via an anionic insertion process. Polyacrylonitrile grafts were grown on the poly(styrene‐co‐acrylonitrile) backbone.
Surface properties of epoxy systems, 1. Influence of the chemical structure on surface energy of monomers, comonomers and additives
Authors: Chen Dong , Pascault Jean Pierre , Sage Daniel
Published: April 2003

The plate method was used to measure the surface tension of different epoxy prepolymers and different hardeners. The values are correlated to the chemical structure. The effect of molecular weight is very weak for diglycidyl ether of bisphenol A (DGEBA) prepolymers. For α,ω‐diamino‐terminated poly(propylene oxide) (PPO) oligomers, the surface tension remains constant when M̄n changes. However, the surface tension increases for PPO oligomers when the number of amino end‐groups increases, and for α,ω‐epoxy‐terminated oligomers when M̄n increases. These results are discussed in terms of a competition between the surface tension of the chain ends and the surface tension of the constitutional repeating units. The surface tension of carboxy‐(CTBN) and epoxy (ETBN)‐terminated butadiene‐acrylonitrile random copolymers is lower than the value of DGEBA prepolymers. In homogeneous blends these oligomers have a surfactant effect.
Surface properties of epoxy systems, 2. Evolution of epoxy‐amine system with reaction time
Authors: Chen Dong , Pascault Jean Pierre , Sage Daniel
Published: April 2003

With the plate method we determined dynamically the surface tension of different epoxy‐amine systems. After different critical observations about the validity of this type of measurement during the reaction time, we were able to correlate the evolution of the surface tension with epoxy conversion. For epoxy systems based on cycloaliphatic diamines, the diamine is the low energy component in the monomer blend. As the diamine reacts, its concentration in the bulk decreases, the surface is improverished in surfactant, and the surface tension of the reactive system increases. A constant value is obtained when all the diamine monomer has been consumed. The final surface tension of a fully cured epoxy system without additive can be higher than any of the surface tensions of the initial reactants. But for rubber‐modified epoxy systems, the rubber is the component with the lowest surface energy, the surface properties of the reactive system are independent of the reaction time and very close to the surface properties of the rubber.
Synthesis of polymers containing pseudohalide groups by cationic polymerization, 2. Copolymerization of 3,3‐bis(azidomethyl)oxetane with substituted oxetanes containing azide groups
Authors: Cheradame Hervé , Gojon Eric
Published: April 2003

The cationic copolymerization of 3,3‐bis(azidomethyl)oxetane (BAMO) was studied, initiated by a mixture of boron trifluoride diethyl etherate/diethylene glycol (2,2′‐oxydiethanol). The copolymerization of BAMO with 3‐azidomethyl‐3‐(2,5‐dioxaheptyl)oxetane (AMDHO) and 3‐azidomethyl‐3‐(2,5,8‐trioxadecyl)oxetane (AMTDO) was investigated in order to obtain at the same time a decrease of the crystallization tendency and of the glass transition temperature of poly(BAMO). The interest in this copolymerization is linked with the fact that, when BAMO was copolymerized with 15 wt.‐% of AMTDO, it was possible to obtain bifunctional oligomers with a glass transition temperature in the −50 to −60°C range, without significant loss in the nitrogen content.
Synthesis and properties of processable rigid polymers containing spiroacetal moieties
Authors: Lee Kwang‐Sup , Kim Hyun Min , Rhee John M. , Lee Soo‐Min
Published: April 2003

A series of rigid rod‐like polyspiroacetals bearing flexible side chains was prepared by interfacial polycondensation of 4,4′‐(2,4,8,10‐tetraoxaspiro[5,5]undecane‐3,9‐diyl)diphenol with 2,5‐dialkoxy‐substituted terephthaloyl dichlorides. The majority of these polymers were soluble in polar solvents like tetrahydrofuran (THF), dimethylformamide (DMF), CHCl3, phenol/CCl4 (1 : 1 by vol.) mixtures, etc. The molecular weights ranged from 7 600 to 15 000 and the melting temperature from 182 to 228°C. Both of the above values decreased with increasing length of the side chains. The TG curves revealed 5% weight loss at 350–370°C under N2 gas atmosphere. Wide‐angle X‐ray diffractograms showed that all of the polymers have considerable crystallinity at room temperature.
Effect of phosphoric acid on the polycondensation of ε‐caprolactone with δ‐valerolactone and biodegradation of their copolyesters
Authors: Imasaka Kazumichi , Nagai Tsuneji , Yoshida Masaru , Fukuzaki Hironobu , Asano Masaharu , Kumakura Minoru
Published: April 2003

Copolycondensation of ε‐caprolactone (CL) and δ‐valerolactone (VL) was performed in the presence and absence of phosphoric acid, in order to clarify the competition between the ring‐opening reaction of lactones and the polycondensation of linear compounds produced by this reaction. The gel permeation chromatography data showed that the monomer peaks remained in the system even after 7 h from start of the reaction when polymerized in the absence of phosphoric acid and, on the contrary, in the presence of phosphoric acid the peaks disappear perfectly within 1 h. The weight‐average molecular weights (M̄w) of poly(CL‐co‐VL), obtained by copolycondensation with and without phosphoric acid at 200°C for 1 h, were approximately 540 and 8900, suggesting that phosphoric acid markedly accelerates not only the rate of ring‐opening but also the rate of copolycondensation. On the other hand, the biodegradation of the copolyesters obtained is characterized by the action of a lipase‐type enzyme, showing a typical parabolic‐type degradation pattern.
Synthesis and rheological study of some maleic acid and fumaric acid stereoregular polyesters, 6. Influence of some parameters on the polycondensation reaction of potassium maleate and 1,4‐dihalogenobutanes
Authors: Sepulchre Marie‐Odile , Sepulchre Maurice , Spassky Nicolas , Djonlagić Jasna , Jaćović Mihailo S.
Published: April 2003

The influence of several parameters on the polycondensation reaction of potassium maleate and 1,4‐dihalogenobutanes has been studied in 1‐methyl‐2‐pyrrolidone at moderate temperature. The yield and molecular weight of the obtained polyesters as well as the extent of trans isomerization and the nature of chain end‐groups depend strongly on the mole ratio of reagents, the nature of halogen in the 1,4‐dihalogenobutanes and on the presence of small amounts of water in the reaction mixture. In particular, it has been observed that water increases the consumption rate constant of 1,4‐dibromobutane but at the same time acts as a terminating agent.
Factor analysis applied to X‐ray diffraction diagrams of polymer blends
Authors: Zhang Hongfang , Yin Jinhua
Published: April 2003

The feasibility of applying the method of factor analysis to X‐ray diffraction diagrams of binary blends of polypropylene and ethylene‐propylene‐diene terpolymer (PP/EPDM) was examined. The result of mathematical treatment was satisfactory. The number of scattering species and their concentrations in six kinds of PP/EPDM blends were determined. The separation of the spectral peaks of each species in the blends, contributing spectral intensities, was carried out.
Photo‐degradable polymer microcapsules
Authors: Kitano Hiromi , Oehmichen Thomas , Ise Norio
Published: April 2003

Microcapsules were prepared by a coupling reaction of disuccinimido 4,4′‐azobis(4‐cyanovalerate)

Systematic name: 5,5′‐bis(imidooxy)‐2,2′‐dimethyl‐5,5′‐dioxo‐2,2′‐azodipentanenitrile.

with L‐lysine, and/or polyallylamine in a water/oil emulsion system. The microcapsules show a light‐responsive release of an inner content, succinylated bovine serum albumin, to the outer bulk phase. Effects of the composition of the coupling suspension on the photo‐durability of the microcapsules obtained were examined. The microcapsules would be useful as a device of photo‐responsive systems.
Effect of the internal/external donor pair in high‐yield catalysts for propylene polymerization, 1. Catalyst‐cocatalyst interactions
Authors: Noristi Luciano , Barbè Pier Camillo , Baruzzi Giovanni
Published: April 2003

The chemistry of the catalyst‐cocatalyst interaction was investigated in systems containing different internal/external donor pairs. Qualitatively similar results were obtained with the ethyl benzoate/methyl p‐toluate (EB/MPT) and dibutyl phthalate/triethoxy(phenyl)silane (DBP/EPS) systems, which thus were assumed to follow the same model. Quantitative differences were accounted for by assuming a different basic strength of the two donor pairs towards MgCl2 and AlEt3.
Complex structure formation in thin microlithographic coating systems
Authors: Köhler Johann Michael , Weh Lothar
Published: April 2003

A characteristic sequence of structures is observed during the curing process of bilayer systems of thin films of novolak and poly(vinyl alcohol). Patterns arise spontaneously in such thin film systems heated above 140°C. At first, cell‐like structures are formed followed by wave and ripple patterns. The temporal order of the formed features is in opposition to the well‐known order of dissipative structures of coupled hydrodynamical instabilities. The rate of pattern formation strongly increases with temperature and thickness of the novolak sublayer. The character of the final pattern depends on this film thickness, too.
A new procedure for the determination of molar mass distribution from sedimentation equilibrium runs in an analytical ultracentrifuge (AUC), 1. Measurements with interference optics
Authors: Lechner M. Dieter , Mächtle Walter
Published: April 2003

A new procedure for the determination of the number‐, weight‐ and z‐average molar masses M̄n, M̄w and M̄z and a model molar mass distribution W(M) has been developed from measurements of the sedimentation equilibrium. The method is based on the determination of the experimentally measured reduced concentration profile by extrapolation to zero concentration and direct calculation of the molar mass distribution W(M) by nonlinear regression of the integral equation according to the Simplex procedure. Results obtained in different solvents for the well characterized polystyrene NBS 706 with broad distribution are reasonable. Generally, it can be concluded that the suggested procedure is a suitable possibility for the determination of molar mass average values and the molar mass distribution of polymers if the latter is a log‐normal, Schulz‐Flory or Poisson distribution.
Surface modification of poly(methyl methacrylate) by graft copolymerization
Authors: Ichijima Hideji , Okada Toshiyuki , Uyama Yoshikimi , Ikada Yoshito
Published: April 2003

Graft copolymerization was carried out onto a poly(methyl methacrylate) (PMMA) plate for surface modification. The following treatments were conducted to introduce peroxides into the PMMA surface prior to graft copolymerization: UV irradation, corona discharge, glow discharge, and ozone exposure. The static contact angle of the PMMA plate toward water decreased from 66° to 45 and 38° by the pre‐treatment with corona and glow discharge for 5 min, respectively, whereas the pre‐treatment with UV irradiation and ozone exposure caused no appreciable decrease in contact angle. When graft copolymerization of acrylamide (AAm) was carried out onto the pre‐treated PMMA plates by near‐UV light irradiation to decompose the peroxides in the presence of riboflavin, the contact angle further decreased to approximately 20° and the amount of AAm polymer grafted was 20–25 μg · cm−2 for the pre‐treatments with corona discharge, glow discharge and UV irradiation. However, graft copolymerization was practically not achieved onto the PMMA plate pre‐treated with ozone exposure. On the other hand, when graft copolymerization was performed at 50°C after degassing without UV irradiation, the amount of AAm polymer grafted was always less than 10 μg · cm‐2, independent of the pre‐treatment methods.
Porosity determination of poly(trimethylolpropane trimethacrylate) gels
Authors: Schmid Andrea , Kulin Lars‐Inge , Flodin Per
Published: April 2003

Trimethylolpropane trimethacrylate (TRIM) was suspension‐polymerized with toluene as poreforming agent. The concentration of the monomer (TRIM) in the porogen was varied between 20 and 50 vol.‐% of the organic phase. The poly(TRIM) particles had narrow particle‐size distributions. The porosity of the dry gels was studied with scanning electron microscopy, nitrogen adsorption/desorption and mercury porosimetry. All gels had bimodal pore‐size distributions. The size distribution of large pores (r > 50 Å) of solvent free poly(TRIM) broadened when the amount of TRIM was decreased. The pore‐size distributions of the swollen poly(TRIM) gel particles were calculated from size‐exclusion chromatography (SEC) results. The separation range for poly(TRIM) particles of polystyrene standards varied with the monomer concentration. A relationship between the pore‐size distribution of dry poly(TRIM) gels and those of swollen gels is proposed. Whether or not the structure of poly(TRIM) gels could be described as fractals is discussed.
Behaviour of ring‐shaped polymers in dilute solution. Quantitative calculation and experimental verification for molecular dimensions and second virial coefficient
Authors: Huang Jiaxian , Li Chunrong , Chen Guohua , Zhu Duanhui , Shen Jun , Liu Dongzhou
Published: April 2003

Relationships between the ratios of the mean‐square radii of gyration gs and the second virial coefficients gA2 of ring‐shaped and linear polymers with the degree of polymerization P of the polymer and its Peterlin exponent ε in dilute solution were derived theoretically and numerical values calculated. The second virial coefficients of ring‐shaped and of linear polystyrene at 25°C in toluene were determined using light scattering. By verifying the theoretical calculation based on the experimental determination of this polymer‐solvent system with light scattering and other methods reported in the literature, the agreement between theoretical calculation and experimental results is shown. The correlation equations for linear (l) and ring‐shaped (r) polystyrene in toluene at 25°C A2, 1 = 8,06 · 10−3 · M0,224 and A2,r = 6,68 · 10−3 · M0,218 were obtained using light scattering.
Photosensitivity in doped and sensitized cis‐polyphenylacetylene
Authors: Yang Mujie , Zhao Jian , Zhang Wende , Shen Zhiquan
Published: April 2003

The photosensitivity in cis‐polyphenylacetylene (cis‐PPA, polymerized with rare‐earth catalysts) can be significantly enhanced by doping the PPA with I2 or FeCl3 and sensitizing with 4‐isothiocyanatofluorescein (F‐II) or 2,4,7‐trinitro‐9‐fluorenone (TNF), which are powerful sensitizers. The electrophotographic photoreceptor (P/R) device with cis‐PPA + F‐II (on Al substrate) appeared preferable in photosensitivity enhancement and showed good photosensitivity: dark decay 1,8 V/s; maximum rate of discharge 321 V/s; residual surface potential 22 V; discharge 89, 1%; photosensitivity 2,96 s−1. This is a new “family” of photosensitive materials which can be used in a duplicator.
Enzyme‐analogue built polymers, 29. The preparation of defined chiral cavities for the racemic resolution of free sugars
Authors: Wulff Günter , Haarer Jutta
Published: April 2003

New types of macroporous polymers containing chiral cavities were prepared for the racemic resolution of free sugars. As template monomers 6‐O‐methyl‐ and 6‐O‐benzyl‐αD‐galactopyranose 1,2;3,4‐tetra‐O‐bis(4‐vinylphenylboronate) (3c and b) as well as 1‐O‐methyl‐ and 1‐O‐benzyl‐βD‐fructopyranose 2,3;4,5‐tetra‐O‐bis(4‐vinylphenylboronate) (4c and b) were copolymerized with a large amount of ethylene dimethacrylate. After splitting off the respective templates, these polymers were used for the racemic resolution of the racemates of D,L‐galactose and D,L‐fructose, and also the racemates, of 1‐O‐methyl‐ and 1‐O‐benzyl‐D,L‐fructose. The polymer prepared from 3b yielded the highest selectivity for the racemic resolution of D,L‐galactose. In the case of fructose the benzyl‐ether‐imprinted polymers yielded the highest selectivity, especially for 1‐O‐methyl‐D,L‐fructose separation. Polymers imprinted with D‐galactose derivatives showed inverse selectivity by preferably absorbing L‐fructose from the racemate. Polymerization at lower temperatures usually yielded more selective polymers.
Copolymerization of styrene and methyl α‐cyanocinnamate, 2. Head‐to‐head and head‐to‐tail penultimate copolymerization
Authors: Kelen Tibor , Borbély János , Bednarski Ralf , Braun Dietrich
Published: April 2003

Based on NMR investigations and on composition data it was concluded that the copolymerization of styrene with methyl α‐cyanocinnamate obeys a penultimate mechanism (reactivity ratios r2 = r′2 = 0) with both head‐to‐tail and head‐to‐head couplings. A theoretical treatment of the mechanism supplied correlations which fit experimental sequence distribution data.
Copolymerization of macromonomers of poly(2,6‐dimethyl‐1,4‐phenylene oxide) with various comonomers
Authors: Wicker Michael , Heitz Walter
Published: April 2003

Macromonomers of poly(2,6‐dimethyl‐1,4‐phenylene oxide) (PPO) were synthesized by reacting the monofunctional polymer with 4‐vinylbenzoyl chloride. The macromonomer was copolymerized with isoprene, butadiene, styrene, ethyl acrylate, and butyl acrylate. Reactivity ratios of 2,6‐dimethylphenyl 4‐vinylbenzoate (2) as a model compound were determined with styrene (St) and butyl acrylate (BA). The values obtained are rSt = 0,504, r2 = 1,233, and rBA = 0,123, r2 = 4,070. Polystyrene‐graft‐PPO is a one‐phase system with a Tg between those of the homopolymers. Tg's of the polyacrylate and PPO fractions are not changed by the composition of the polyacrylate‐graft‐PPO. DSC and dynamic mechanical measurements revealed that the polyacrylate‐graft‐PPO copolymers are phase‐separated if the molecular weight of the PPO macromonomer is high enough. In thermogravimetric analysis the polyacrylate‐graft‐PPO shows a two‐step weight, loss, one due to the polyacrylate at 380–390°C and another due to the PPO at 440–460°C.
Studies of the mechanism of the radical polymerization of vinyl acetate inhibited by furan compounds. Phenomenology and sensitivity analysis
Authors: Rieumont Jacques , Vega Rebeca
Published: April 2003

The classical treatment of inhibition in radical polymerization is complemented by a “sensitivity” analysis. This technique permits to establish which of the possible reactions are relevant or negligible to gain a better insight into the mechanism. The 2,2′‐azoisobutyronitrile (AIBN)‐initiated polymerization of vinyl acetate was studied in the presence of 5‐nitrofuroic acid and 3‐(2‐furyl)acrylic acid as inhibitors. The monomer dependence of the ratio of rate constants for the degradative transfer and chain propagation, ktrs/kp, and the values of the stoichiometric coefficients for these inhibitors were obtained and analyzed in the light of sensitivity analysis.
On the origin of the fluorescence emission of poly(ethylene terephthalate) by excitation at 340 nm
Authors: Chen Liusheng , Jin Xigao , Du Jinhuan , Qian Renyuan
Published: April 2003

Fluorescence emission of amorphous poly(ethylene terephthalate) films at wavelengths larger than that of the excimer emission was investigated. A film thickness dependence of the excitation spectra for 360 nm emission was observed. For thick films (e.g., 280 μm), their excitation spectra for 380–460 nm emission showed excitation peaks in the region of 320–360 nm, and the intensity ratio of the 370 nm emission (excited by 290 nm radiation) to the 390 nm emission (excited by 340 nm radiation) decreased with increasing thickness of the film. Apparently, the 370 nm emission (excimer) and the 380–460 nm emission originate from different species of the excited state. From the studies of model systems, dilute solutions of dimethyl terephthalate in CHCl3‐acetone and dimethyl terephthalate‐PMMA in CHCl3, it was found that the excitation at 340 nm is related to a \documentclass{article}\pagestyle{empty}\begin{document}$ \mathop \pi \limits^* $\end{document} ← n transition. Fluorescence emission from the S1 (n–\documentclass{article}\pagestyle{empty}\begin{document}$ \mathop \pi \limits^* $\end{document}) state and the interaction between the CO group and the phenylene π‐electrons results in the fluorescence in the 380–460 nm region.