bluuebunny/crossref_metadata_2025_split huggingface dataset:
Side‐chain crystallinity in comb‐like polymers. Poly‐(ethylene oxide)‐polyacrylates and ‐polymethacrylates
Authors: Yang Fen , Déjardin Philippe , Frère Yves , Gramain Philippe 
Published: April 2003

AbstractMelting temperatures, heats of fusion and the derived enthalpies and entropies of fusion were obtained by differential scanning calorimetry for poly(ethylene oxide) (PEO)‐acrylate and ‐methacrylate macromonomers and the corresponding polymers. The side‐chain lengths varied from three to ninety‐three ethylene oxide units. The thermodynamic data for macromonomers and polymers were calculated according to the theory of Flory and Vrij, which has been shown to describe well the melting behavior of linear PEO. It is shown that the melting parameters for macromonomers are identical to those of pure PEO in spite of the presence of the chain ends of different nature. With the PEO comb‐like polyacrylates and polymethacrylates, the melting points are only a few degrees higher than those of the corresponding monomers. Their crystalline content calculated from the molar enthalpies are 83% and 78%, respectively. In contrast to linear PEO, the interfacial free energy is negative for both types of polymers due to a high value of the interfacial entropy. It is suggested that the tighter packing of the chain ends, including the backbone, is responsible for this high value, together with the possible presence between the lamellae of constructed amorphous side chains. The combined results lead to the conclusion that the crystalline organization is quite comparable to that of pure PEO of equal length with, however, one or two fewer crystallized EO units.
13C NMR studies of the polymerization mechanism and the dynamics of poly(alkyl methacrylate) grafted onto silk fibers
Authors: Lenka Subasini , Demura Makoto , Asakura Tetsuo 
Published: April 2003

Abstract13C NMR was extensively used to determine the tacticity of poly(methyl methacrylate) (PMMA), poly(ethyl methacrylate) (PEMA), and poly(butyl methacrylate) (PBMA) grafted onto silk fibers using radiation‐induced graft copolymerization. All polymers are predominantly syndiotactic and the tacticity is virtually independent of the degree of grafting. The value of PΣ (= Pm/r + Pr/m) was calculated from the triad distribution and was found to be approximately one. This indicates that all the above polymer chains grafted onto silk fibers are syndiotactic and obey Bernoullian statistics. The number‐average sequence length of either meso or racemic additions was determined using the triad distribution. The 13C NMR relaxation parameters, spin‐lattice relaxation time, T1, and nuclear Overhauser effect, NOE, were observed and then the value of the correlation time for average segmental motion, τc, and the width parameter, p, were determined by assuming a log χ2 distribution for the correlation time. A relatively small value of p was obtained, indicating that the distribution of the correlation time is large. Taking into account the τc values of different poly(alkyl methacrylate) chains grafted onto silk fibers, the following order of segmental motion was furnished: PMMA > PEMA > PBMA.
Complexation of poly(ethylene glycol) with lithium salts in solution
Authors: Bekturov Esen A. , Ismagulova Svetlana S. , Dzumadilov Talkybek K. 
Published: April 2003

AbstractThe complexation of poly(ethylene glycol) (PEG) with lithium salts (LiCl, LiBr, LiNO3, LiClO4, LiSCN) in solution is investigated using electroconductivity, 1H NMR and 7Li NMR spectroscopy. For the systems PEG‐LiNO3 and PEG‐LiCl in acetonitrile the interaction of salt with polyether hydroxyl groups leads to a dissociation of the salt.
NMR studies on the structure of linear polyurethanes and their interactions with chromium (III) chloride. A 1H, 13C, 17O and two‐dimensional investigation
Authors: Hiller Wolf , Gähde Joachim , Gehrke Rolf , Stopperka Klaus 
Published: April 2003

Abstract1H, 13C, 17O and two‐dimensional NMR measurements were carried out to characterize the interactions of polyurethanes with chromium (III) chloride. It was found that CrCl3 forms complexes with polyurethanes via the NH groups of urethane groups as well as via the carbonyl groups of urethane groups and polyester. The interactions of CrCl3 with carbonyl groups can be confirmed by 17O measurements in model compounds.
New multiphase thermoplastic elastomers by combination of covalent and association‐chain structures
Authors: Hilger Christopher , Stadler Reimund 
Published: April 2003

AbstractA new type of multicomponent thermoplastic elastomers is prepared by attaching 4‐(3,5‐dioxo‐1,2,4‐triazolin‐4‐yl)benzoic acid to polybutadiene chains. The groups are difunctional with respect to a potential chain‐molecule formation via reversible association. Thus, a covalent polymer is combined with an association polymer. Characterisation of the thermal and mechanical properties shows that phase separation between the two ‘polymers’ stabilizes the association polymer. The supramolecular ordered structure is characterised by the observation of a melting endotherm and birefringent textures in the material. The mechanical properties are comparable to thermoplastic elastomers based on covalent multiblock copolymers with high modulus and tensile strength.
Neck profiles in drawn polypropylene and ethylene/propylene copolymers
Authors: Ibhadon Alex O. 
Published: April 2003

AbstractThe application of classical rubber elasticity theory to strain hardening and the determination of entanglement molecular weight enables strain hardening to be modelled mathematically. This together with the strain rate dependence of yield stress have been used to study the shape of the neck in drawn isotactic polypropylene and ethylene/propylene copolymers. The relationship between strain hardening and strain rate sensitivity and the neck formed is discussed, as well as the effects of molecular weight and comonomer content on strain hardening behaviour.
Polymérisation induite par un plasma froid. Intéractions plasma‐polymère, caractérisation de la structure chimique du matériau à la surface et dans i'épaisseur
Authors: Poncin‐Epaillard Fabienne , Brosse Jean‐Claude 
Published: April 2003

AbstractThe polymerization of octadecyl methacrylate (2) and of 3‐methylenepentamethylene triacrylate [trimethylolpropane triacrylate (1)], induced by a microwave plasma and the chemical structure of the final polymers are described. Modification of the polymers by cold plasma (CF4) treatment is pointed out. The extent of fluorination is not proportional to the time of treatment. A maximum is observed which is due to the evolution of the concentration of different excited species, such as F*, CF* and CF*, present in the gas phase.
Propene polymerization with Mg(OEt)2‐supported TiCl4 catalyst, 1. Catalyst composition and behavior
Authors: Jeong Young‐tae , Lee Dong‐ho 
Published: April 2003

AbstractCatalysts obtained from TiCl4 and ball‐milled Mg(OEt)2 in the presence of a halide compound (dichloroethane, chlorobenzene or dichlorobenzene) and/or an internal donor (ethyl benzoate or diisobutyl phthalate) were prepared for propene polymerization. The composition of the catalysts was analyzed by IR, GC, atomic absorption spectroscopy and titration. The exchange reaction between the ethoxy group of the support and the chloride group of TiCl4 was found to depend profoundly on the halide compound and/or the internal donor used. The propene polymerizations were carried out using various Mg(OEt)2‐supported catalysts and triethylaluminium as cocatalyst with or without external donor (triethoxyphenylsilane). The catalyst activity and stereospecificity were examined.
Determination of the number of active centers in Ziegler‐Natta polymerization of propene using sulfur‐containing stoppers, 3. Carbon disulfide tagging – Its mechanism and applicability
Authors: Vozka Pavel , Mejzlík Jiří 
Published: April 2003

AbstractThis paper analyses in detail the dependence of the number of CS2 tags in polypropene (PP) on the relative polymerization rate upon addition of CS2. It is shown that centers of higher activity are subjected to a faster deactivation and tagging by CS2. It was deduced that their higher reactivity with CS2 is not likely to be connected with their stereospecificity. Irreversibility of the CS2‐insertion reaction was documented, at least under the conditions of our experimentation. A mechanism of action of CS2 was outlined and adsorption coefficients were determined for the TiCl3/AlEt2Cl and TiCl3/AlEt3 systems. A direct proof of insertion of CS2 into the growing transition metal‐carbon bond could not be obtained. An indirect method (employing COS as a poison) allowed us to conclude that in case of CS2 two atoms of sulfur are incorporated into the polymer per each deactivated center. On this basis, the number of centers was determined for both catalyst systems. A much higher propagation rate constant (kp) was found for the AlEt3‐cocatalyzed polymerization. It was concluded that the above method is applicable to the determination of active centers, but caution must be exerted in widening its application to other systems.
Glow discharge decomposition of phenylsilane in the presence of oxygen
Authors: Nakamura Takashi , Sinigersky Vesselin A. , Sato Kota , Koinuma Hideomi 
Published: April 2003

AbstractThin films of organosilicon were prepared by glow discharge decomposition of phenylsilane in the presence of oxygen. As a result of spectral analyses and optical band gap measurements of the deposited films, the oxygen was found to be scarcely incorporated in the bulk of the films at least when the mole fraction of oxygen in phenylsilane was less than 0,5. The oxygen appeared to promote plasma polymerization of phenylsilane. The electric conductivity of the films prepared from mixed O2/C6H5SiH3 was enhanced by iodine “doping” by four orders of magnitude.
Phase transformation in poly(1‐butene) blended with hydrogenated oligo(cyclopentadiene)
Authors: Canetti Maurizio , Romanó Maria , Sadocco Patrizia , Seves Alberto 
Published: April 2003

AbstractIsothermally crystallized blends of isotactic poly(1‐butene) (PB‐1) with hydrogenated oligo‐(cyclopentadiene) (HOCP) were annealed for different periods of time and at different temperatures and then analyzed by differential scanning calorimetry. The HOCP, a glassy oligomer with a relatively high Tg value, results with PB‐1 in a one‐phase system in the melt. The kinetics of crystal transformation of poly(1‐butene) from form II to form I are subject to the influence of the non‐crystallizable component on the amorphous phase of PB‐1. The phase transformation process was also analyzed by means of the Avrami equation. During the conversion process secondary crystallization of PB‐1 was observed.
Polymers from 2‐allyloxymethyl‐2‐ethyltrimethylene carbonate and copolymers with 2,2‐dimethyltrimethylene carbonate obtained by anionic ring‐opening polymerization
Authors: Kühling Steffen , Keul Helmut , Höcker Hartwig 
Published: April 2003

Abstract2‐Allyloxymethyl‐2‐ethyltrimethylene carbonate (1) was polymerized in toluene with sec‐butyllithium as initiator. The resulting product exhibits a bimodal molecular weight distribution. The low‐molecular‐weight fraction consists mainly of cyclic oligomers and to a minor portion of acyclic oligomers. With 2,2‐dimethyltrimethylene carbonate (2) as a comonomer, statistical and block copolymers were obtained upon addition of the initiator to a mixture of the monomers or upon consecutive addition of the monomers to the initiator, respectively. The primary structure of these copolymers was unambiguously determined by means of 13C NMR spectroscopy of especially the carbonyl region, since the carbonyl carbon atom is a sensitive probe for structural changes in its neighbourhood. All polymers were crosslinked upon using di‐tert‐butyl peroxide as a source of radicals. The thermal behaviour of the polymers before and after crosslinking was studied.
Equilibria in the anionic polymerization of methyl methacrylate, 2. Effect of lithium tert‐butoxide on rate and equilibrium constants
Authors: Lochmann Lubomír , Müller Axel H. E. 
Published: April 2003

AbstractThe effect of lithium tert‐butoxide (t‐BuOLi) on rate constants and equilibrium constants of reactions involved in the initial stage of the anionic polymerization of methyl methacrylate (MMA) in tetrahydrofuran, initiated by methyl α‐lithioisobutyrate (P) was investigated at 23 ± 3°C. Addition of t‐BuOLi decreases the rate constants of initiation and propagation by one order of magnitude; the rate constants of termination by cyclization decrease by two orders of magnitude. This leads to an overall tenfold higher preference of propagation with respect to termination and explains the favourable effect of alkoxide in the polymerization reported earlier. Within experimental error, the equilibrium constant for initiation is independent of alkoxide. The infrared spectra prove the interaction of lithiated MMA‐dimer with t‐BuOLi and show the changed properties of the Li‐enolate group as well as the increased extent of the γ‐ester group coordination to lithium.
Concentration effect in acceptor‐catalytic polyesterification
Authors: Vasnes Valerii A. , Ignatov Vladimir N. , Vinogradova Svetlana V. , Tseitlin Henric M. 
Published: April 2003

AbstractThe effect of the concentration of reagents on the kinetics of acceptor‐catalytic esterification is investigated for a homologous series of poly(oxyethylene)s 1 (number of oxyethylene units in the polymer chain: n is between 1 and 68). The reaction rate constant, k0, is found to be dependent on the concentration of the reagents and on the length of the polymer chain. The effect of concentration is most pronounced in the case of low‐molecular‐weight 1 (n = 1; 3). With an increase in the polymer chain length the concentration effect on the reactivity of the end groups decreases and is practically nil for oligomers containing 45 and 68 oxyethylene units.
Synthesis and thermal properties of liquid‐crystalline polyesters with mesogenic units and siloxane spacers in the main chain
Authors: Braun Frank , Willner Lutz , Heß Michael , Kosfeld Robert 
Published: April 2003

AbstractThermotropic liquid‐crystalline polyesters with either 4,4″‐p‐terphenylylene or p‐phenylene‐oxyterephthaloyloxy‐p‐phenylene as mesogenic units and dimethylsiloxane spacers in the main chain were synthesized. The thermal behaviour was studied by means of differential scanning calorimetry, polarizing microscopy, and X‐ray diffractometry. The polymers show mainly smectic mesomorphism. The transition temperatures were found to be much lower than in the corresponding polyesters containing polymethylene or poly(oxyethylene) spacers.
Synthesis of alternating polydepsipeptides by ring‐opening polymerization of morpholine‐2,5‐dione derivatives
Authors: in 't Veld Peter J. A. , Dijkstra Pieter J. , van Lochem Jan H. , Feijen Jan 
Published: April 2003

AbstractPolydepsipeptides with alternating α‐hydroxy acid and α‐amino acid residues were synthesized by ring‐opening polymerization of morpholine‐2,5‐dione derivatives. The polymerizations were performed in the melt using stannous octoate as an initiator. Molecular weights of the polydepsipeptides obtained ranged from 0,9 · 104 to 7,4 · 104. Morpholine‐2,5‐dione derivatives unsubstituted at the 6‐position gave polymers with the highest molecular weights. Poly((S)‐alanine‐alt‐glycolic acid) was semi‐crystalline, whereas all other polydepsipeptides synthesized were amorphous. Morpholine‐2,5‐dione derivatives were synthesized by N‐acylation of glycine, (S)‐alanine or (S)‐valine with chloroacetyl chloride or (R,S)‐2‐bromopropionyl bromide, followed by ring‐closure of N‐(2‐halogenacyl)‐amino acid sodium salts in the melt in 4 to 83% yield. Low yields in the cyclization reaction of N‐(2‐halogenacyl)‐(S)‐valine were accompanied by the formation of the corresponding polydepsipeptides in 13 to 46% yield, with molecular weights ranging from 3,3 · 104 to 4,9 · 104.
Thermodynamic investigation of the phase separation behaviour of ethylene‐vinyl acetate copolymers in diphenyl ether
Authors: Van der Haegen Rudy , van Opstal Luc 
Published: April 2003

AbstractLiquid‐liquid phase separation in solutions of ethylene‐vinyl acetate (EVA) random copolymers is investigated for different VA content using diphenyl ether (DPE) as the solvent. Cloud‐point curves (CPC's), spinodal curves (SC's) and critical conditions (CC's) were experimentally established by visual observation, pulse‐induced critical scattering (PICS) and phase‐volume ratio method, respectively. It is found that the miscibility gap, which is of the Upper Critical Solution Temperature (UCST) type, shifts to lower temperatures as the VA content in the copolymer increases. The limits of thermodynamic stability (spinodals) could be reasonably well described by means of the classical rigid lattice model, provided allowance is made for the various constitutional repeating units (CRU's) to differ in nearest‐neighbour contacts. Using this description, CC's and SC's could be predicted in a qualitative way. Further, measured CPC's can be nearly described in a quantitative sense when the value of the higher molecular weight average M̄z is adjusted well above the value suggested by GPC measurements.
Evaluation of unperturbed dimensions parameter from intrinsic viscosity data of any binary or ternary polymer system
Authors: Gavara Rafael , Campos Agustín , Figueruelo Juan E. 
Published: April 2003

AbstractTaking into account the dependency on molar mass of the viscometric interaction parameter B, the modified Stockmayer‐Fixman‐Burchard equation ([η]/M1/2) = KΘ + C″ · A2 · M1/2 is obtained. It relates the intrinsic viscosity, [η], to the second virial coefficient, A2, and to the unperturbed dimensions parameter, KΘ, with C″ being a constant. Hereupon, KΘ can be determined from [η] and A2 data of any binary (solvent/polymer) and/or ternary (solvent 1/solvent 2/polymer) system, BPS and/or TPS. Because of the scarcity of reliable sets of [η] and A2 values mostly for TPS, the application of the above equation to obtain KΘ coefficients rests limited. This limitation can be surmounted by an A2 evaluation from [η] data and trial KΘ values through two‐parameter theories taking into account the interpenetrating factor between chains, ψ, as evaluated from the Flory‐Krigbaum‐Orofino (FKO) theory, from a modified FKO theory, or from the Kurata‐Yamakawa theory. An interative process is followed until coincidence between assumed and evaluated KΘ values is reached. The method has been applied to the KΘ evaluation from [η] with literature data for diverse BPS and TPS of polystyrene, poly(methyl methacrylate), poly(dimethylsiloxane), poly(2‐vinylpyridine) and poly(1‐vinyl‐2‐pyrrolidone), with the respective KΘ values 7,5 · 10−2, 5,8 · 10−2, 8,2 · 10−2 and 6,4 · 10−2, 7.2·10−2 and · 6,4 · 10−2 mL · mol1/2 · g−3/2 being obtained. Moreover, a single C″ value, mainly C″ = 0,52, holds for all five polymers.
Functionalized monomers, 1. Synthesis and characterization of oxirane and oxetane derivatives of styrene
Authors: Truxa Roman , Suchopárek Milos̆ 
Published: April 2003

AbstractOptimum experimental conditions were found for the syntheses of 4‐vinylphenyloxirane (4) and 4‐vinylbenzyloxirane (9). The new monomer 2‐(4‐vinylphenyl)oxetane (11) was synthesized. All mentioned monomers are able to form polymers substituted with heterocyclic groups upon radical polymerization of the vinyl groups. Monomer 4 was found to be able to form polyether 13 containing repeating units substituted with 4‐vinylphenyl groups upon complex coordination polymerization via the oxirane groups, initiated with (C2H5)2AlOAl(C2H5)2.
Functionalized monomers, 2. Kinetics of radical polymerization of oxirane‐ and oxetane‐derivatives of styrene and copolymerization of 4‐vinylphenyloxirane with styrene
Authors: Truxa Roman 
Published: April 2003

AbstractThe kinetics of radical polymerization of 4‐vinylphenyloxirane (1), 4‐vinylbenzyloxirane (2), and 2‐(4‐vinylphenyl)oxetane (3) initiated by 2,2′‐azoisobutyronitrile (AIBN) was studied. In the case of 1 the initial rate of polymerization was found to depend on the initiator and monomer concentrations as (rp)total ∝︁ [AIBN]0,5 · [M1]1,36. The higher order of the polymerization rate with respect to 1 was interpreted as due to a concurrent thermally initiated polymerization; the rate of the latter was found to depend on the monomer concentration squared. The value of the ratio propagation rate constant over square root of termination rate constant kp/kt1/2 = 2,8 · 10−2 dm3/2 · mol−1/2 · s−1/2 was determined from the measured dependences (rp)total = f[AIBN] and (rp)total = f([M1]), corrected for the rate of thermally initiated polymerization of 1. On the other hand, the kinetics of radical polymerization of 2 and 3 did not deviate from the standard scheme valid for radical polymerization; in both cases the observed reaction order with respect to initiator and monomer was 0,5 and 1, respectively. Radical copolymerization of 4‐vinylphenyloxirane (M1) with styrene (M2) was characterized by monomer reactivity ratios r1 = 1,06 and r2 = 0,78, respectively, corresponding to the Q, e‐scheme values Q = 0,9 and e = −0,36 for monomer 1.
Functionalized monomers, 3. An investigation of initiation systems used in the anionic and complex‐coordination polymerization of oxirane groups in 4‐vinylphenyloxirane
Authors: Truxa Roman 
Published: April 2003

AbstractThe effect of various types of alkoxides and of a complex coordination initiator based on Et2AlOAlEt2, of the polarity of the medium and of the temperature on the rate of polymerization of 4‐vinylphenyloxirane (1) and on the structure of the resulting polymers was studied as part of the investigation of the activity of the oxirane ring in the structure of (1) under the conditions of anionic polymerization. In a nonpolar medium the activity of the initiators increases in the series sodium methoxide < potassium tert‐butoxide < Et2AlOAlEt2. The complex Et2AlOAlEt2 preferentially initiates the polymerization of 1 via the oxirane cycles, giving rise to soluble polymers, the structure of which, determined on the basis of their 13C NMR spectra, corresponds to that of polyethers substituted with 4‐vinylphenyl groups. In the presence of aluminium isopropoxide the polymerization of 1 via the vinyl groups proceeded with the formation of a solution of a polymer which becomes insoluble after the termination of polymerization. Copolymerization of 1 with phenyloxirane, initiated with the complex Et2AlOAlEt2, yields soluble copolymers containing a fraction of monomeric units of 1, higher than that of 1 in the feed.
Copolymers obtained by means of anionic ring‐opening polymerization. Poly(2,2‐dimethyltrimethylene carbonate)‐block‐polypivalolactone
Authors: Keul Helmut , Höcker Hartwig , Leitz Edgar , Ott Karl‐Heinz , Morbitzer Leo 
Published: April 2003

AbstractThe anionic ring‐opening polymerization of mixtures of 2,2‐dimethyltrimethylene carbonate (5,5‐dimethyl‐1,3‐dioxan‐2‐one) (1) and pivalolactone (2,2‐dimethyl‐3‐propanolide) (3) in toluene as a solvent and with potassium dihydronaphthylide as initiator, results in formation of block copolymers with yields of ca. 90%. In tetrahydrofuran as a solvent the polymer yields are ca. 65% only. In toluene, 1 polymerizes first and subsequently 3 resulting in a blocky structure of the copolymer. According to a mechanistic study, the active species is first a 1‐alcoholate, later a 3‐alcoholate and finally a 3‐carboxylate. The copolymers are soluble in deuterochloroform up to a mole fraction of pivalolactone of ca. 0,40. By means of 13C NMR spectroscopy the blocky structure of the copolymers prepared in toluene was confirmed. In tetrahydrofuran as a solvent 1‐3 and 3‐1‐diads are formed to a significant extent. The copolymers were characterized by thermoanalytical and thermomechanical measurements.