bluuebunny/crossref_metadata_2025 huggingface dataset:
Free‐radical polymerization of methyl methacrylate at very high conversions, 2. Study of the kinetics of initiation by benzoyl peroxide
Authors: Stickler Manfred , Dumont Emil
Published: April 2003

The initiation kinetics of the free‐radical polymerization of methyl methacrylate at very high monomer conversions was investigated at 80, 100, and 120°C. Using a HPLC (high performance liquid chromatography) analytical technique with UV detection, the consumption of both monomer and initiator as well as the formation of reaction products of the latter could be followed. It was found that (besides very small amounts of biphenyl and benzoic acid) phenyl benzoate is the main decomposition product. The experimental results were analyzed quantitatively with the help of a reaction scheme which takes into account the most important pathways of that complex chemical reaction system. Thus, it was found that, due to the very strong cage effect in the present polymerization system, the experimentally accessible (apparent) first order rate constant of initiator decomposition is substantially lower than that for the primary cleavage of a benzoyl peroxide molecule. Efficiencies of chain initiation were calculated to be in the range of 0,1 to 0,2 in the (nearly) glassy polymer matrix.
Simulation of coupled modification reactions of polymers, 1. Monosubstitution and double bond shift of 1,4‐polybutadiene
Authors: Hummel Klaus , Martl Michael G.
Published: April 2003

Computer simulation is well suited for theoretical investigation of coupled modification reactions of polymers to make subsequent comparison with experimental results. The percentage of units resulting in 1,4‐polybutadiene for substitution coupled with partial double bond shift is calculated for a simplified model. In the computer program three pseudo‐random number generators are used for simulation. The substitution degree SU and the shift degree SH describe the modification. In the general case, 22 chemically different units result. Borderline cases are SH = 0 with at most 3 units and SH/SU = 1,0 with at most 12 units. A detailed investigation is carried out for the especially interesting range SU = 0,1 to 0,5 and SH/SU = 0,1 to 0,5.
The effect of units derived from diethylene glycol on crystallization kinetics of poly(ethylene terephthalate)
Authors: Yu Tongyin , Bu Haishan , Chen Jianhua , Mei Jibang , Hu Jialun
Published: April 2003

The effect of units derived from diethylene glycol (DEG) on the crystallization behaviour and linear growth rate of spherulites of poly(ethylene terephthalate) (PETP) free of metal catalyst residues, is studied by means of differential scanning calorimetry (DSC), small‐angle light scattering (SALS), polarized light microscopy (PLM), and transmission electron microscopy (TEM). The results show that the crystallization behaviour does not depend only on the temperature of crystallization, but also on a large scale on the content of DEG. In hot crystallization, the rate of PETP crystallization decreases with increasing DEG content; in cold crystallization, this effect is not so prominent. The higher the DEG content, the smaller is the number of nuclei and therefore the linear growth rate of PETP and, at the same time, the size of the spherulites becomes greater.
Miscibility of linear and branched polyethylene in the liquid state
Authors: Illers Karl‐Heinz , Köhnlein Ernst
Published: April 2003

HDPE/LDPE blends and the pure components were crosslinked either by irradiation or by di‐tert‐butyl peroxide in the liquid state. The degree of crosslinkage was characterized by the reciprocal degree of swelling Q−1 (xylene, 2 h, 140°C). Above a critical degree of crosslinkage corresponding to Q−1 = 0,2 the DSC curves of HDPE/LDPE blends show only one single crystallization peak on cooling from the melt and only one single melting peak on subsequent heating. This is an unequivocal proof for the single phase structure of HDPE/LDPE blends in the liquid state. Crosslinking with Q−1 ≥ 0,2 prohibits fractional crystallization and forces the unbranched CH2 sequences of both components between the crosslinks into one crystal lattice.
Synthesis and properties of polyurethanes derived from diaminodianhydroalditols
Authors: Thiem Joachim , Lüders Harald
Published: April 2003

The readily accessible 1,4:3,6‐dianhydroalditols with D‐gluco‐ (1), L‐ido‐ (5) and D‐mannoconfigurations (6) were efficiently transformed into the 2,5‐diamino‐1,4:3,6‐dianhydro‐2,5‐dideoxyalditols with D‐gluco‐ (10), D‐manno‐ (13), and L‐ido‐configuration (16). Interfacial polycondensation of these chiral heterocyclic diamines as well as ethylene‐ and tetramethylene diamine with the bis(chloroformate) 3 derived from 1,4:3,6‐dianhydro‐D‐sorbitol gave the polyurethanes 17 to 21. Their number‐average molecular weights were determined to be M̄n ≈ 3000 corresponding to an average degree of polymerisation P̄n ≈ 20. Inherent viscosities were measured, and 1H NMR spectroscopy as well as DSC gave informations about the molecular structure and some polymer properties.
Preparation and electrical properties of poly(3‐thienylacetylene)
Authors: Tanaka Susumu , Okuhara Kunio , Kaeriyama Kyoji
Published: April 2003

3‐Thienylacetylene (1) was prepared by reaction of 3‐(2,2‐dichloro‐1‐fluorovinyl)thiophene with butyllithium in a 1 : 2 mole ratio, and subsequent hydrolysis. Polymerization of 1 with WCl6 and tetraphenyltin gave poly(1), poly[1‐(3‐thienyl)vinylene], which contained a small amount of benzene‐insoluble product. On heating poly(1) no weight loss was observed up to 240°C. At 500°C the weight loss was 18%. In differential scanning calorimetry, an exothermic peak appeared at 245°C. A pressed pellet, doped with iodine, exhibits conductivity of about 10−3 S/cm. The absorption spectrum of poly(1) shows a shoulder at 225 nm, a maximum absorption at 360 nm and tailing up to about 660 nm. In a solution of poly(1) and I2, a new absorption appeared in the near‐infrared region, but failed to develop enough to suggest high conductivity of poly(1) doped with iodine. The electrochemical doping of poly(1) and electrochemical polymerization of 1 gave no conducting products.
Dégradation de polybutadiènes par métathèse avec l'hexène‐3 dioate de diméthyle
Authors: Campistron Irène , Reyx Danièle
Published: April 2003

Studies of metathetic degradation of polybutadienes containing 70 to 80% of 2‐butene‐1,4‐diyl units (1) in presence of dimethyl 3‐hexenedioate (2) were carried out applying WCl6/Me4Sn as catalyst and r = [2]/[1] values varying between 0,4 and 0,01. The degradation was followed by steric exclusion chromatography, and the structural composition of degraded products was determined by 1H NMR. For r = 0,2, the degradation by cross metathesis between 1 and 2, leading to α,ω‐bifunctionalized “prepolymers”, is superimposed by degradation via intramolecular metathesis and cationic cyclization of 1 units. Cationic side reactions (cyclization) are minimized by addition of ethyl acetate to the catalytic system.
Synthesis of antitumor‐active conjugates of adriamycin or daunomycin with the copolymer of divinyl ether and maleic anhydride
Authors: Hirano Takashi , Ohashi Shinichi , Morimoto Satoshi , Tsuda Keishiro , Kobayashi Tomowo , Tsukagoshi Shigeru
Published: April 2003

Polymeric conjugates of adriamycin (ADR) (2) or daunomycin (DM) (3) were synthesized by reaction of the drugs with the copolymer of divinyl ether and maleic anyhdride (DIVEMA) (1). The content of ADR moieties in the DIVEMA conjugate (4) could be varied depending on the reaction conditions up to 35,8 wt.‐%. Considering the low toxicity and the high possibility of renal excretion, DIVEMA with M̄w of 7000 and M̄w/M̄n = 1,6 was used for the conjugation. The rate of drug release from the conjugate was determined under physiological conditions by reversed phase HPLC. Within 14 days only 15% of the attached ADR was released from conjugate 4. The antitumor activity of the conjugates was tested in vitro and in vivo against mouse P388 leukemia. Conjugate 4 proved to be 28 times less active than ADR in vitro, which could be explained from the slow drug‐release. On the contrary 50% of the leukemic mice treated by 4 survived more than 60 days, whereas no mice given ADR alone or the admixture of ADR and DIVEMA survived 30 days. An antitumor activity of the polymeric conjugate better than that of the free drug was also observed in vivo with DM. Such a polymeric effect can be attributed either to the change in body distribution, the difference in pharmacokinetics, or the slow drugrelease.
Lyotropic mesophase of imogolite, 2. Microscopic observation of imogolite mesophase
Authors: Kajiwara Kanji , Donkai Nobuo , Fujiyoshi Yoshinori , Inagaki Hiroshi
Published: April 2003

Imogolite, though achiral, forms cholesteric spherulites in the anisotropic phase as shown by the regular striations arranged in a swirl‐like or fingerprint pattern observed through a polarizing microscope. Electron microscopy revealed the raft‐like imogolite sheet floating in the anisotropic phase. The structure of the imogolite sheet was deduced from periodicities observed by an electron microscope using various imaging conditions. The origin of the twisting force to maintain the cholesteric ordering is also discussed.
Emulsifying properties of saturated polyesters
Authors: Baumann Harald , Joos Betina , Funke Werner
Published: April 2003

Saturated emulsifying polyesters (EPE's) with terminal carboxyl groups were prepared by melt condensation from 1,6‐hexanediol, 1,4‐butanediol, phthalic acid, and adipic acid. The EPE's were characterized by molar mass, acid number, and hydroxyl number. Micelle formation of the EPE in the neutralized state was studied. The critical micelle concentration of the EPE is influenced by chain structure, chain length, temperature, and presence of electrolyte. A monomer mixture of styrene/unsaturated polyester (1 : 1 by wt.) was solubilized with different EPE's. On addition of NaHCO3 and NaCl the monomer mixture is optimally solubilized at a distinct concentration of electrolyte. At the optimal electrolyte concentration the solubilization of the monomer mixture is influenced by chain structure and chain length of the EPE.
Polymeric phthalocyanines and their precursors, 12. Reversible reduction and reoxidation of thin films of octacyanophthalocyanine in polymer matrices
Authors: Wöhrle Dieter , Kaune Holger , Schumann B. , Jaeger Nils
Published: April 2003

Thin films containing 1–100 μg 2,3,9,10,16,17,23,24‐phthalocyanineoctacarbonitrile (1) and 10–100 μg poly(N‐vinylcarbazole) (2) resp. the polyimide 3 were prepared on gold substrates through casting from solution. Smooth green coloured films were obtained. According to VIS spectra molecules of 1 are aggregated within the polymer matrices. Cyclic voltammetric measurements were carried out in 0,5 M sulfuric acid. Mixed films of 1 and 2 show remarkably stable electrochromic redox behaviour and the charge exchanged in the cathodic and anodic wave, respectively, was found to be between 2,3 and 2,7 F/mol for scan rates up to 400 mV · s−1. For mixed films of 1 and 3 with lower amount of 1 or increasing layer thickness the reduction and reoxidation appears to be a diffusion controlled process.
Morphology of triblock copolymers in the presence of unbonded segments
Authors: Perego Giovanni , Roggero Arnaldo , Vitali Roberto , Zazzetta Alessandro , Skoulios Antoine
Published: April 2003

The morphology of ABA triblock copolymers [A: polystyrene, poly(α‐methylstyrene); B: polybutadine] containing unbonded A′ segments (free A chains) was studied using small‐angle X‐ray scattering and transmission electron microscopy. Experimental results indicate the formation of ‘mixed’ segregation microdomains containing both A and A′ segments. With the assumption that homopolymer molecules locate themselves in the central region of the microdomains, away from the interfacial regions — which sounds reasonable at least when the homopolymer concentration is not too high — simple equations were derived permitting the calculation of the microdomain size that would correspond to systems deprived of their parasitic homopolymer. Values obtained are in fairly good agreement with those predicted by Helfand's thermodynamic theory.
Lithium alkylamide catalyzed addition reactions of alkylamines to vinyl monomers, 1. Selective formation of N‐α‐methylbenzyl‐4‐vinylphenethylamine
Authors: Narita Tadashi , Hagiwara Tokio , Hamana Hiroshi , Kurashima Tomihiro
Published: April 2003

The lithium alkylamide catalyzed addition reaction of α‐methylbenzylamine (1) with styrene was found to produce selectively N‐phenethyl‐α‐methylbenzylamine (3). Under the same reaction conditions, addition of (S)‐α‐methylbenzylamine (1′) to 1,4‐divinylbenzene (5) takes place selectively leading to the optically active novel styrene derivative, (S)‐N‐α‐methylbenzyl‐4‐vinylphenethylamine (6), in a one‐step reaction. The specific rotation was found to be [α]4D = −70,1° (c = 1,61 g/dl, in methanol). The following Q, e‐values and the monomer reactivity rations of 6(M1) and styrene (M2) were obtained: Q1 = 1,59, e1 = −1,28; r1 = 0,86, r2 = 0,92.
Synthesis and curing of poly(styrylpyridine)s. Structural study on models and on the resins, 1. Thermal behaviour of low‐molecular‐weight styrylpyridines
Authors: Clavreul Régine , Bloch Bertrand , Brigodiot Maryvonne , Maréchal Ernest
Published: April 2003

It could be shown that the structure of poly(styrylpyridine)s (PSP), which are heat resistant thermosetting resins resulting from the polycondensation of 2,4,6‐trimethylpyridine (1) with terephtalaldehyde (2), is much more complicated than that expected from this polycondensation. 2‐Styrylpyridines were synthesized from benezaldehyde (5) and 2‐methylpyridines and the stability of the respective intermediate alcohol was studied. The thermal behaviour of the styrylpyridines alone or in the presence of their precursors was studied by GPC, IR and NMR spectroscopy and by chemical analyses. It could be shown that the methyl group of 2‐methylpyridine (4) adds reversibly to the double bond of 2‐styrylpyridine (7) to form 2‐phenyl‐1,3‐bis‐(2‐pyridyl)propane (8). This side reaction takes place also in the case of the condensation of 1 with 5. The structures and the reactivity of the condensation products of 1 with 1,2 or 3 molecules of 5 (compounds 14, 17 and 18) were studied. The condensation product 19, a component of PSP resins, was synthesized from 1 and 2 and its reactivity was studied at 200 and 250°C and compared with the non‐methylated derivative 1,4‐bis[2‐(2‐pyridyl)vinyl]benzene (25). The results of a preliminary analysis of the reactions taking place during the PSP thermosetting are reported.
Synthesis and curing of poly(styrylpyridine)s. Structural study on models and on the resins, 2.1H and 13C NMR study of the models
Authors: Clavreul Régine , Bloch Bertrand , Brigodiot Maryvonne , Maréchal Ernest
Published: April 2003

The structures of the compounds, resulting from the condensation of 2‐methylpyridine, 2,6‐dimethylpyridine and 2,4,6‐trimethylpyridine with benzaldehyde and terephtalaldehyde, were confirmed by high field 1H and 13C NMR spectroscopy. Structural assignments were made based on the NMR spectra of the intermediate compounds, 4‐[1‐hydroxy‐2‐4,6‐dimethyl‐2‐pyridyl‐ethyl]benzaldehyde (5) and 4‐[1‐hydroxy‐2‐(6‐methyl‐2‐pyridyl)ethyl]benzaldehyde (6), of the main reaction products 2‐styrylpyridine (3) and 1,4‐bis[2‐(4,6‐dimethyl‐2‐pyridyl)vinyl]‐benzene (1), and of the side reaction product 2‐phenyl‐1,3‐bis(2‐pyridyl)propane (4) resulting from the addition of the methyl groups of 2‐methylpyridine to the double bond of 3.
Polymerization of isobutene with VOCl3 in heptane
Authors: Hasenbein Norbert , Bandermann Friedhelm
Published: April 2003

The polymerization of isobutene with VOCl3 in heptane was investigated. In contrast to reports in the literature, the polymerization only starts upon irradiation with light, also when naphthalene is added, and it ceases when the light source is switched off. Thus, it is suggested that the reaction proceeds like a photoinitiated cationic polymerization, and the claim of a living system is not corroborated.
Surface wettability of silicone rubber films
Authors: Koßmehl Gerhard , Neumann Walter , Schäfer Horst
Published: April 2003

Silicone films were equilibrated with special organosiloxanes in the presence of hexacholorocyclotriphosphatriene as catalyst in ethers as solvents. Thus, the hydrophobic silicone films developed a hydrophilic surface. This surface treatment does in no way reduce the oxygen permeability of the silicone films. The special organosiloxanes required for the equilibration were produced by addition of allyl compounds containing protected OH‐groups to siloxanes containing SiH‐groups, applying H2PtCl6 as catalyst, and subsequent hydrolysis of the addition products.
Effect of N,N,N′,N′‐tetramethylethylenediamine on the reaction parameters of Ziegler‐Natta macromolecular complexes in the polymerization of ethylene
Authors: Mederven Craig , Brun Bruno , Siove Alain , Fontanille Michel
Published: April 2003

Soluble complexes of ω‐lithiumbutenylpoly(styrene‐co‐butadiene) (≈ 100: ≈ 3 DP) with TiCl4 were used in conjunction with N,N,N′,N′‐tetramethylethylenediamine (TMEDA), to initiate the polymerization of ethylene. The activity of such a system was measured as a function of the number of amino groups (N) per active center (A. C.) ([N]/[A. C.]). From measurements of the amount of polystyrene‐block‐polyethylene produced and from kinetic studies of the polymerization of ethylene, the influence of TMEDA on both the efficiency of the system and the reactivity of the active species was studied. The depressor effect of the diamine on the reaction parameters, controlling the polymerization of ethylene, was connected with the proposed structure of the active sites. The role of the Lewis base was discussed by assuming a reversible blockage of a vacant coordination site at the titanium throughout the complexation of the electrophilic “host sites” of the polymer [TiCl2, TiCl3, 3 LiCl] complexes.
Copolymerization via zwitterion, 8. β‐butyrolactone and 2‐ethyl‐2‐oxazoline
Authors: Rivas Bernabé L. , Canessa Guido S. , Pooley Sonia A.
Published: April 2003

2‐Ethyl‐2‐oxazoline (ETOX) as nucleophilic monomer and β‐butyrolactone (BUL) as electrophilic monomer were copolymerized in bulk in the absence of initiator at 45°C. Copolymers were characterized by elemental analysis, IR, 1H NMR, and 13C NMR spectroscopy. The copolymer composition was determined by elemental analysis and by 1H NMR spectroscopy. All copolymers contain a BUL:ETOX mole ratio greater than one.
Computer simulation of the steady state in reversible polymer‐analogous reactions, 2. Simulation of the statistics in detailed balance
Authors: Krieger Dorit , Klesper Ernst
Published: April 2003

The steady state of reversible polymer‐analogous reactions is simulated by Monte Carlo methods. Two types of sets of relative rate constants were investigated, first, K1 = K2 = K3, K1 · K3 = (K2)2, and second, K1 ≠ K2, K1 ≠ K3, K2 ≠ K3, K1 · K3 = (K2)2. For both cases a detailed balance was found. The sequence probabilities depend on dimensionless relative rate constants Kn only, while the rates of sequence flow depend on reaction probabilities p and ordinary rate constants k. For the first case, the sequence probabilities obey a Bernoullian statistics, while for the second case a first‐order Markov statistics is found.
Kinetics of the free radical terpolymerization of diethyl maleate with methyl methacrylate and styrene
Authors: Braun Dietrich , Cei Gustavo
Published: April 2003

The kinetics of the free radical terpolymerization of diethyl maleate (DEM) (M1) with methyl methacrylate (MMA) (M2) and styrene (M3) was investigated at 60°C with AIBN as initiator. The analysis of the dependence of the terpolymer composition on the feed composition was difficult due to the similar chemical and physical properties of diethyl maleate and methyl methacrylate and also by the low content of the former monomer in the terpolymers. Finally, the terpolymer composition could be determined by means of microanalyses of carbon and hydrogen content. The results of these determinations were confirmed by 13C NMR spectroscopy. The initiation rate constant of AIBN was studied at different feed compositions by means of the inhibition method. For the study of the over‐all polymerization kinetics of this ternary system it was necessary to take into account the dependence of the termination rate on the feed composition. It was found that not only the viscosity of the solution, but also the properties of the polymer segment next to the radical site have to be considered. Containing only parameters and constants measured independently from terpolymerization, the kinetic equation obtained described satisfactorily the initial over‐all rates.
Polymerization of lactams, 77. On the limit temperature (ceiling temperature) of the anionic polymerization of 2‐pyrrolidone
Authors: Fries Tomáš , Bělohlávková Jana , Nováková Olga , Roda Jan , Králíček Jarosloav
Published: April 2003

The kinetics of the nonactivated anionic polymerization of 2‐pyrrolidone (PD) initiated with the potassium salt of 2‐pyrrolidone (KPD) and anionic polymerizations of PD accelerated with CO2 and 1‐(1‐pyrrolin‐2‐yl)‐2‐pyrrolidone or activated with 1‐benzoyl‐2‐pyrrolidone and 1‐acetyl‐2‐pyrrolidone were followed near the ceiling temperature (limit temp. T1) and discussed. The values of T1 were extrapolated from the data obtained for the given initiation systems. The dependence of T1 on the concentration of the initiation system was also investigated.
Steric effects on excimer formation in 2‐amino‐1,3‐di(2‐naphtyl)propane luminiscent markers covalently bonded to poly [N‐(2‐hydroxypropyl)methacrylamide]
Authors: Burešová Marie , Koñák Čestmír , Labský Jiří
Published: April 2003

The fluorescence spectra of poly[N‐(2‐hydroxypropyl)methacrylamide] (poly[1‐(2‐hydroxypropylaminocarbonyl)‐1‐methylethylene]) with covalently bonded luminiscent markers (2‐amino‐1, 3‐di(2‐naphthyl)propane (ADNP)) dissolved in methanol were measured over the temperature range 190–290 K. The effect of the spacer length on intramolecular excimer formation in ADNP was investigated. The ratio of the fluorescence intensities of the dimer ID and the monomer IM follows an Arrhenius temperature dependence in the temperature range 190–250 K with an activation energy independent of the spacer length. The numerical value of ID/IM at constant temperature increased with increasing spacer length reaching quickly a limiting value. The effect is explained by increasing hindrance to intramolecular excimer formation which is due—particularly for the shortest spacers—to increased steric interactions of the marker with the polymer chain.
Influence of termination and transfer on molecular weight distribution of polymers, 8. Spontaneous transfer
Authors: Yuan Cui‐ming , Yan De‐yue
Published: April 2003

The kinetics of cationic polymerization with instantaneous initiations and spontaneous transfer is treated theoretically. By means of a non‐steady state analysis, rigorous expressions for the molecular weight distribution and other molecular parameters are derived from the set of differential equations without introducing any approximations. The influence of spontaneous transfer on the molecular weight distribution is discussed in detail based on several numerical examples.
Conductivity and spectroscopic characterization of polyacetylene doped with ferric chloride
Authors: Chen Zhongxin , Shen Zhiquan , Chen Changshen , Zhao Yonggang , Yang Mujie
Published: April 2003

cis‐ and trans‐Polyacetylene

Systematic name: (Z)‐ and (E)‐poly(viny1ene).

films prepared by a rare‐earth coordination catalyst were doped with ferric chloride in nitromethane solution. The doped polyacetylene films [CH(FeCl4)y]x exhibit high electrical conductivities which change very little when stored in dry air. Infra‐red absorption bands at 900 cm−1, 1300 cm−1 and 1400 cm−1 are typical for cis‐and trans‐polyacetylenes slightly doped with FeCl3. In the samples with dopant mole fractions y < 0,02, two superimposed ESR signals with different g values are observed: one very narrow, the other one extraordinarily broad. 57Fe‐Mössbauer effect measurements reveal that Fe(II) and Fe(III) species coexist in freshly doped cis‐polyacetylene, appearing in the form of FeCl2 · nH2O and FeCl−4, respectively. Fe(II) species do not interact with the polyacetylene chain; they exist at a site separated from Fe(III) species.
Polymerizable tautomers, 4. Solvent effects in radical copolymerization of ethyl 3‐oxo‐4‐pentenoate and styrene
Authors: Masuda Seizo , Tanaka Masami , Ota Tadatoshi
Published: April 2003

Ethyl 3‐oxo‐4‐pentenoate (1) exhibits the coexistence of two tautomers, the ketonic and enolic form, and its tautomeric equilibrium shifts with the solvent. The monomer reactivity ratios for the radical copolymerization of 1 (M1) and styrene (M2) in various solvents were determined. There is a marked and a minor solvent effect on r1 and r2, respectively. Regression analysis of r1 with the solvatochromic parameters yields a fairly good linear relationship, taking into account three factors: polarity and hydrogen bond donating and accepting powers of the solvents.
A calorimetric investigation of interactions in aqueous solutions of poly(oxyethylene), 1. Heats of mixing of oligomeric models
Authors: Biroš Ján , Pouchlý Julius , Živný Antonín
Published: April 2003

Heats of mixing with water as function of the composition of the mixtures for oligomeric models of poly(oxyethylene) at 25°C are reported, i. e. for compounds of the type XO(CH2CH2O)nX (where X = H or CH3 and n = 1, 2, 3, or 4) and CH3O(CH2CH2O)mH (where m = 1 or 2). These dependencies greatly depend on the character of the end groups and on the degree of oligomerization. A procedure has been suggested for the comparison between the heat of mixing of longer chains and that of shorter ones with elimination of the effect of end groups. On the same mass basis, longer chains release more heat than shorter ones in mixing with water for concentrated solutions; hence, one may assume some kind of cooperativity of ether oxygen atoms in the same chain by hydration.
Crystallization kinetics of 1,4‐trans‐polyisoprene, 1. Pure polymer
Authors: Chaturvedi Prakash N.
Published: April 2003

The Crystallization kinetics of an unfractionated sample of 1,4‐trans‐polyisoprene was studied from its melt by means of the dilatometric method. The data are analysed according to the secondary nucleation theory. A critical discussion and comparison of previously published kinetic parameters with those derived in the present study is made. The values of the product of interfacial free energies, σσe, were found to be 590,5 and 915 erg2/cm4 for the low melting and high melting polymorphs, respectively. The observed deviation from the Avrami theory towards completion of the process is interpreted to be due to the low molecular weight species of the low melting polymorph.
Spherulites primary nucleation in binary miscible blends of poly(ethylene oxide) with poly(methyl methacrylate)
Authors: Bartczak Zbigniev , Martuscelli Ezio
Published: April 2003

The influence of composition on the primary nucleation process of poly(ethylene oxide) spherulites in the case of poly(ethylene oxide)/poly(methyl methacrylate) (PEO/PMMA) blends was investigated by optical microscopy and DSC. In the case of isothermally crystallized samples it was found that heterogeneous nucleation is depressed in the blends in comparison with plain PEO. This depression is caused by the dilution effect of PMMA. The self‐seeding nucleation mode is also disturbed by the presence of PMMA in the blends. This is due to both the diluent effect and to the decrease of the PEO melting temperature. In the case of non‐isothermally crystallized samples of PEO/PMMA blends an apparent increase of the nucleation density was observed. This observation is attributed to the fact that the growth rate is depressed in the blends: thus, at an earlier stage of crystallization, the volume in which the nuclei are free to develop (for a given crystallization condition) is larger.
Transfer by weak acids in the slow‐initiation‐no‐termination (SINT) polymerization of butyl cyanoacrylate
Authors: Pepper David Charles
Published: April 2003

The theory of slow‐initiation‐no‐termination polymerization has been extended to take account of transfer by added or adventitious transfer agents (T), giving equations relating the number‐average molecular weight (M̄n) to the ratios of concentrations of transfer agent to monomer ([T]0/[M]0) and of transfer to propagation rate constants (ktr/kp). The equations are shown to give a fair description of the M̄n values found in the polymerization of butyl cyanoacrylate by pyridine and by tetrabutylammonium acetate in presence of known concentrations of cyanoacetic, chloroacetic and acetic acids. Approximate values are yielded for the rate constant ratios, viz. 102(ktr/kp) ≈ 15,5 and 0,3, respectively (in tetrahydrofuran at 20°C). Conversely, the theory is shown to explain variations in M̄n values found in polymerizations of five different samples of this monomer, permitting characterization of the unknown concentrations of transfer‐causing impurity.
On the kinetics and mechanism of thermal degradation of poly(p‐methylstyrene)
Authors: Schröder Ulrich K. O. , Ederer Hanns J. , Ebert Klaus H.
Published: April 2003

The thermal behavior of polydisperse poly(p‐methylstyrene) (PPMS) samples with M̄w's of 99200 and 356000 g/mol was investigated under oxygen‐free conditions at temperatures between 220 and 345°C. The reaction products were analysed by gel permeation chromatography (GPC), gas chromatography (GC) and swelling measurements. In the initial stage of the reaction crosslinking occurs; at higher temperatures the gel decomposes to polymers with a low degree of polymerization and to volatile products with molecular weights in the range up to trimers. A radical chain mechanism is proposed for degradation which explains the experimental results. On this basis a model is evaluated for gel formation, which is discussed in detail. The results of the present investigation are compared with the thermal degradation of polystyrene (PS) which is chemically similar but does not crosslink.
Hydroxytelechelic polybutadiene, 10. Molecular weight and functionality distribution of a radically obtained hydroxytelechelic polybutadiene studied by GPC and 1H NMR
Authors: Deschères Isabelle , Païssé Olivier , Colonna‐Ceccaldi Jean‐Noël , Pham Quang‐Tho
Published: April 2003

Hydroxytelechelic polybutadiene (HTPB) Arco‐R45M® obtained by free‐radical‐initiated polymerization of butadiene was fractionated by preparative gel permeation chromatography (GPC) using styragel and silicagel as column material. The fractions separated were extensively studied by vapour pressure osmometry (VPO), GPC, and 1H NMR. Commercially available non‐hydroxylated polystyrene and polybutadiene standards cannot be utilized for the proper direct determination of the molecular weight of HTPB by means of GPC. Both high and low hydroxyl functionalities were found for high‐ and low‐molecular‐weight HTPB. The analytical results are discussed in terms of the polymerization mechanism.
Melt rheology of compatible binary blends: Poly(ethylene oxide)‐poly(methyl methacrylate) and poly(ethylene oxide)‐poly(vinyl acetate)
Authors: Martuscelli Ezio , Vicini Loredana , Seves Alberto
Published: April 2003

A study of the rheological behaviour of poly(ethylene oxide)‐poly(methyl methacrylate) and poly(ethylene oxide)‐poly(vinyl acetate) compatible blends in the molten state is reported. Zero shear viscosity η0 and the activation energy for the viscous flow ΔE* were obtained as function of both composition and molar mass of the components. Positive and negative deviations from the additivity rule were observed both in the case of log η0 and ΔE*.
Single crystal structure of a polymerization active Nd‐Al bimetallic complex
Authors: Shan Chengji , Lin Yonghua , Ouyang Jun , Fan Yuguo , Yang Guangdi
Published: April 2003

A polynuclear Nd‐Al bimetallic complex in single crystalline form, which is active for diene polymerization, was isolated and its detailed structure was determined by X‐ray diffraction technique. The results indicate that the crystal is triclinic, space group P1; the lattice parameters are: a = 15,195(6), b = 15,263 (5), c = 13,749 (4) Å; α = 90,01 (2), β = 95,12 (3), γ = 82,65 (3)°; V = 3149,5 Å3; Z = 1. The coordination number of the Nd atom is seven and the configuration is monocap‐prism. Nd atoms can be divided into three groups according to their coordination environment.
Stress‐induced orientation in lightly crosslinked liquid‐crystalline side‐group polymers
Authors: Zentel Rudolf , Benalia Mokhtar
Published: April 2003

X‐ray measurements of stretched crosslinked liquid‐crystalline side group polymers show that two types of orientation of the mesogenic groups relative to the polymer chains (parallel or perpendicular) are possible, depending on the structure of the polymer chain. For two liquid‐crystalline polymethacrylates with long spacer groups (6 methylene units) the mesogenic groups orient preferably perpendicularly to the polymer chains (axis of strain). For three liquid‐crystalline polyacrylates with long or short spacer groups (6 or 2 methylene units), the mesogenic groups orient preferably parallel to the polymer chains (axis of strain). The reason for this difference is not yet clear. These results are compared with earlier results of melt‐drawn fibres of uncrosslinked polymers.
Emulsion polymerization of butyl methacrylate initiated by 2,2′‐azoisobutyronitrile, 3. On the applicability of the modified Smith‐Ewart model
Authors: Capek Ignác , Bartoň Jaroslav , Kárpátyová Angela
Published: April 2003

The applicability of the modified Smith‐Ewart model to the butyl methacrylate emulsion polymerization in interval II, initiated by both 2,2′‐azoisobutyronitrile (AIBN) and ammonium persulfate at 60°C, was tested. The equilibrium monomer concentration in the latex particles in interval II was found to be constant and independent of the emulsifier concentration and the initiator type used. The rate of initiation increases with increasing emulsifier concentration for the polymerizations initiated with a water‐soluble initiator. In the systems with the oil‐soluble initiator, the rate of initiation is independent of the emulsifier concentration. The rate of polymerization increase with increasing emulsifier concentration for both initiator systems. In the system with the oil‐soluble initiator lower values of the polymerization rate and higher values of the viscosity‐average molecular masses of the polymer were observed. The number of particles, the radical concentration within polymer particles and the calculated rate of polymerization increase, while the mean particle radius decreases with increasing concentration of the emulsifier for both systems. The average‐number of radicals per particle and the ratio of the rate constants for propagation and termination was found to be independent of the emulsifier concentration and the initiator type. A good agreement was observed between the estimated and observed particle radii for both initiator systems. The Smith‐Ewart model was found to be applicable for the emulsion polymerization of butyl methacrylate initiated by both ammonium persulfate and AIBN.
Synthesis of monoazacrown ether containing styrene derivatives and monoazacrown ether end‐capped 3‐(or 4‐)vinyl substituted styrene oligomers and polymers
Authors: Akashi Ryojiro , Nagasaki Yukio , Tsuruta Teiji
Published: April 2003

Monoazacrown ether containing styrene derivatives and monoazacrown ether end‐capped 3‐(or 4‐)vinyl substituted styrene oligomers and polymers were synthesized using 1,4,7,10,13‐pentaoxa‐16‐azacyclooctadecane (1a). N‐Lithio‐1,4,7,10,13‐pentaoxa‐16‐azacyclooctadecane (1b) reacts with styrene to form a 1:1 adduct, N‐phenethyl‐1,4,7,10,13‐pentaoxa‐16‐azacyclooctadecane (4). The reactivity of 1b toward styrene, however, is lower than that of other lithium dialkylamides such a lithium diethylamide. 1b reacts also with divinylbenzene to form a 1:1 adduct, N‐(4‐vinylphenethyl)‐1,4,7,10,13‐pentaoxa‐16‐azacyclooctadecane (7), in non‐polar media. The reactivity of 1b toward divinylbenzene is much higher than toward styrene. The yield of the 1:1 adduct 7 was found to attain more than 70% in cyclohexane. In polar media, however, 1b induced a prompt polymerization of divinylbenzene to form a soluble polymer, each molecule of which was found to have one crown ether unit at the end of the polymer chain and a pendant vinyl group on each monomeric unit.
Zerlegung von hemicellulosereichem biologischem material mit wasser in einem strömungsreaktor
Authors: Köll Peter , Lenhardt Herbert
Published: April 2003

Biological materials, rich in hemicelluloses (birch and pine wood, wheat straw and rice hulls) were disintegrated batchwise in a flow reactor with pure water at elevated temperatures and pressures. The resulting extractives and residual fibre compounds were characterized. Because of rapid removal of carbohydrate based extractives from the hot reaction zone, the degradation of pentosans and hexosans to furfural and hydroxymethylfurfural could be limited to only a small amount. Contrary to normal prehydrolysis conditions employing a sealed batch reactor, temperatures of 190 to 210°C and residence times of goods of 60 min are the optimum. Thus, hemicelluloses are dissolved and isolated with up to more than 90% yield. At temperatures above 225°C severe destruction of hemicelluloses and solvolysis of cellulose starts. Depending on disintegration temperatures, pentosan average molecular weights (M̄w) vary in case of birch wood between 3800 at 150°C and 900 at 225°C. The content of monomers rises with temperature and reaches a maximum of 45% at 225°C. DPw of residual cellulose is also temperature dependent and varies in case of birch wood and wheat straw between 1500 and 450. Lignin, which is mostly not dissolved, can be removed almost quantitatively by further treatment of the residue with ethanol/water at 250°C, thus allowing the isolation of relatively pure cellulose.
Preparation of poly(N‐methylmethacrylamide) microspheres containing peroxy ester groups and their use in graft copolymerization
Authors: Sato Tsuneyuki , Matsumoto Yoshitada , Tanaka Hitoshi , Ota Tadatoshi
Published: April 2003

Poly(N‐methylmethacrylamide) [poly(1)] microspheres, carrying peroxy ester groups, were prepared by radical copolymerization of 1 with a small amount of di‐tert‐butyl perfumarate (2) in benzene. Thermal and photo‐induced polymerizations of vinyl monomers with the microspheres were carried out, to produce graft copolymers. Ethanol as additive was found to accelerate the polymerization of benzyl methacrylate (3) at 80°C although the accelerating effect levels off at higher concentrations of ethanol. The grafting efficiency was not high (up to 16,5%) and exhibited a maximum on varying the ethanol concentration. On the other hand, in the photo‐induced polymerization the conversion of 3 increased with increasing ethanol concentration. The grafting efficiency similarly showed a maximum on varying the ethanol concentration. The effects of reaction variables on the thermal and photo‐induced graft copolymerizations of 3 onto the microspheres in the presence of a definite amount of ethanol were examined in the light of the conversion of 3, the grafting efficiency and the percentage of grafting. Long‐lived propagating poly(1) radicals (6) were observed by ESR during heating at 70°C or UV‐irradiation at 30°C of the microspheres in a toluene/ethanol mixture. Thermolysis or photolysis of the microspheres in the presence of 3 yielded a stable propagating poly(3) radical (7). Similarly, this microsphere method was applied to the preparation of long‐lived propagating polymer radicals of some other vinyl monomers.
New thermo‐crosslinking reactions of copolymers of phenyl methacrylates by use of polyfunctional epoxy compounds
Authors: Nishikubo Tadatomi , Saita Seiji
Published: April 2003

Successful new thermo‐crosslinking reactions of copolymers of various phenyl methacrylates by use of polyfunctional epoxy compounds were carried out in the film state at 100–150°C in presence of quaternary ammonium salts, quaternary phosphonium salts, tert‐amines, or the crown ether dicyclohexyl‐18‐crown‐6/potassium salt systems as a catalyst. Addition reactions of 4‐nitrophenyl, 4‐chlorophenyl or phenyl ester groups in the copolymers with ethylene glycol diglycidyl ether (EGGE) result in gel compounds without other side reactions. The rate of gel production of the copolymer having electron‐attracting groups such as the 4‐nitro group on phenoxide is faster than that of the other copolymers. It was also found that the rate of gel production of the copolymer is affected by the amount of phenyl methacrylate component in the copolymer, the glass transition temperature (Tg) of the copolymer, the structure of polyfunctional epoxy compounds as a crosslinking reagent, the length of alkyl chain in the catalyst, and the kind of counter anion of the catalysts, respectively.
Molecular characterization of gelatin by light scattering
Authors: Stejskal Jaroslav , Straková Dagmar , Kratochvíl Pavel
Published: April 2003

In aqueous KSCN solutions the salt is preferentially desorbed from the domain of gelatin molecules, similarly to synthetic polyelectrolytes. Light‐scattering measurements in gelatin solutions in 0,5 M KSCN and in a single solvent (formamide) show that both solvents are suited for the molecular characterization of gelatin at room temperature. Neglecting the effect of selective sorption in salt solutions does not cause any considerable error in the molar mass determination of gelatin.
NMR study of aggregation of heterotactic‐like poly(methyl methacrylate) in solution
Authors: Spěváček Jiří , Fernandez‐Pierola Inés
Published: April 2003

The aggregation of heterotactic‐like poly(methyl methacrylate) (PMMA) in some solutions was proved by NMR spectroscopy. It was found that the fraction of aggregated units depends on solvent, solution concentration and temperature; the aggregates are completely decomposed at 45°C. Aggregation occurs by intermolecular interactions of m‐diads with rrr‐tetrads, i. e. by interactions of the stereocomplex type. The formation of a stable aggregated structure is probably a consequence of the microstructure of the heterotactic‐like PMMA chain, with relatively long sequences of regularly repeating mrrr pentads or mrrr hexads. The aggregation in mixtures of heterotactic‐like PMMA solutions with isotactic or syndiotactic PMMA solutions was also studied.
Silicium‐29 kern‐relaxations‐messungen an kieselsäurederivaten
Authors: Marsmann Heinrich C. , Meyer Ehler
Published: April 2003

Derivatives of silicic acid of the type Si6O5R18 and Si8O7R18 (R = Cl, OCH3, and OC2H5) as well as bicyclic Si8O9(OC2H5)14 were isolated and characterized by 29Si NMR. The spin‐lattice‐relaxation and the nuclear Overhauser enhancement factor of the esters were determined between 273 and 343 K. The temperature dependency of the dipolar contribution to the longitudinal relaxation time gave an energy of activation for the segmental motion of the siloxane skeleton of about 10 kJ/mol which is independent of the kind of building unit.
Resonance Raman spectroscopic studies on dehydrochlorinated stretched poly(vinyl chloride)
Authors: Bowley Heather J. , Gerrard Donald L. , Maddams William F.
Published: April 2003

Resonance Raman spectroscopy has been used to assess the effect of streching on the formation of conjugated polyenes during the thermal dehydrochlorination of poly(vinyl chloride). Two samples, a commerical mass polymer and a material prepared at −30°C, have been examined, unplasticised and plasticised, at different draw ratios. Stretching prior to dehydrochlorination leads to an increase in the length of the polyene sequences, the effect being more marked with the low temperature polymer and with increasing draw ratio. Stretching after dehydrochlorination has no significant effect on the polyene distribution. These observations are consistent with the occurrence of chain orientation and alignment during stretching; this reduces the incidence of cross‐linking between polyene sequences in adjacent chains and leads to an increase in the average sequence length.
Acid and base functionalization of ethylene‐propylene rubbers, 2. Influence of type and content of functional groups on the mechanical and thermal behaviour of elastomeric network
Authors: Greco Pietro , Laurienzo Paola , Maglio Giovanni , Malinconico Mario , Martuscelli Ezio
Published: April 2003

Thermal and mechanical properties of various functionalized ethylene‐propylene rubbers (EPR) were evaluated. The samples studied varied both in the type of functional groups and in the grafting degree. Grafted molecules included succinic anhydride, 2‐(dimethylamino)ethylsuccinimide and 2‐(dimethylamino)ethyl methacrylate. The insertion of these groups was found to influence deeply the elastic response of rubbers, leading to the formation of network whose properties were dependent upon the density of polar crosslinks introduced. On the other hand, the thermal properties were less influenced, i.e. the glass transition temperature Tg increased only slightly with increasing content of functional groups.
Photo‐oxydation des polyéther‐bloc‐polyamides, 2. Influence de la composition des polymères multiséquencés
Authors: Gauvin Pascal , Lemaire Jacques , Sallet Daniel
Published: April 2003

Analytical and kinetical aspects of the photooxidation in the solid state of two polyether‐block‐polyamides 1c and 1d are described. The block copolymers studied contain different polyether sequences at different percentages. In copolymer 1d as well as in copolymers 1a and 1b, previously studied, the photooxidation concerns mainly the ether groups. High maximal concentrations of hydroperoxy groups, CH(OOH)OCH2, are observed (0,12 mol.kg−1). These hydroperoxides are converted into hemi‐acetals, CH(OH)OCH2, saturated esters and formate through photolysis or thermolysis above 60°C. The hemi‐acetal groups are thermo‐unstable too and decompose into alcohol and aldehyde groups. The photooxidation of copolymer 1c presents different features. At long wavelengths, low stationary concentration of hydroperoxy groups are observed (0,02 mol.kg−1). Hydroperoxidation of the polyamide 6 sequences is revealed by the formation of imide groups. Hydroperoxidation of the poly(propylene glycol) sequences are surprisingly located on the ether methylene groups. Excitation of polyamide 6 sequences at short wavelength (254 nm) induces the formation of crotonized aldehyde groups.
Photo‐oxydation et photolyse de copolymères d'éthylène et d'acétate de vinyle à courte et grandes longueurs d'onde
Authors: Glikman Jean‐François , Arnaud René , Lemaire Jacques , Seinera Henri
Published: April 2003

Analytical and kinetic aspects of the photooxidation and photolysis in the solid state of various ethylene‐vinyl acetate (EVA) copolymers (0 < VA (in mol‐%) < 26) are described. At long wavelengths (λ > 300 nm), the photooxidation is independent of the vinyl acetate content. The acetate groups, which are not preferential sites for the photo‐induced hydroperoxidation, are photoconverted into chain ketones similar to those formed in the photooxidation of low density polyethylene (LDPE). As the content of monomeric units of vinyl acetate increases, associations between alcohols formed and the acetate groups are observed, based on the appearance of the 3530 cm−1 absorption band. The rate of the formation of vinyl‐type insaturations is a decreasing function of the content of monomeric units of vinyl acetate. At short wavelength (λ = 254 nm) direct photolysis of the acetate groups is observed through the formation of alcohols and ketones again similar to those found in LDPE photooxidation. The rate of the EVA photolysis varies linearly with the vinyl acetate content. Oxygen reacts with the primary radicals formed at 254 nm. Alcohols and ketones are formed faster than through photolysis, although no stoichiometry change is observed.