bluuebunny/crossref_metadata_2025 huggingface dataset:
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

13C 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

The 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

1H, 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

A 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

The 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

The 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

Catalysts 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

This 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

Thin 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

Isothermally 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

2‐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

The 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

The 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

Thermotropic 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

Polydepsipeptides 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

Liquid‐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

Taking 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

Optimum 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

The 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

The 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

The 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.
TiCl4/MgH2‐supported Ziegler‐type catalyst system, 2. Effect of Ti concentration, Ti content and surface area of TiCl4/MgH2 catalyst on the concentration of active sites in ethylene polymerization
Authors: Jaber Isam A. , Hauschild Klaus , Fink Gerhard
Published: April 2003

The determination of active centres concentration in ethylene polymerization using various TiCl4/MgH2‐Al(C2H5)3 catalytic systems, by the 14CO radio‐tagging method, is reported. It is found that with increasing the absolute titanium amount the concentration of active centres, [C*], increases, whereas the propagation rate constant, kp, decreases. In addition, using various TiCl4/MgH2 catalysts in ethylene polymerization, it is found that the lower the Ti content, the higher is the surface area of the catalyst and the higher is the polymerization activity. Determination of [C*] shows consclusively that the decrease in the polymerization activity observed to occur with increasing the Ti content, and thus decreasing the surface area, is unequivocally due to a reduction in the concentration of active centres but not to any fundamental change in the value of the propagation rate constant.
Induced optical activity on side‐chain aromatic chromophores in copolymers of (−)‐menthyl acrylate with 1,2‐diphenyl‐1,2‐ethanedione‐2‐O‐acryloyloxime
Authors: Angiolini Luigi , Carlini Carlo , Tramontini Maurilio
Published: April 2003

In the present paper the synthesis of optically active copolymers from (−)‐menthyl acrylate (MtA) and 1,2‐diphenyl‐1,2‐ethanedione‐2‐O‐acryloyloxime (BMOA) by radical initiation is described. The copolymers obtained, having different contents of photosensitive O‐acyloxime moieties, were characterized by FT‐IR, 1H NMR and GPC measurements, and their chiroptical properties investigated by circular dichroism. The induced chirality on BMOA co‐units is assigned to isolated rather than to sequential BMOA units. Thus, the induced chirality is due to the molecular dissymmetry of individual O‐acyloxime chromophores flanked by opticaly active MtA units.
Synthesis and characterization of hetero‐arm star copolymers
Authors: Tsitsilianis Constantinos , Chaumont Philippe , Rempp Paul
Published: April 2003

Hetero‐arm star copolymers are constituted of a central core carrying branches of two kinds. The two‐stage synthesis of such polymer species involves an arm‐first step and a core‐first step: A linear anionic living polystyrene precursor was used to initiate the polymerization of a small amount of divinylbenzene, yielding star‐shaped polystyrene bearing living sites inside the cores; in a second stage these sites were used to initiate the polymerization of another monomer — butyl methacrylate —, more electrophilic than styrene. This second step results in the formation of a new set of branches originating from the same polydivinylbenzene cores. The star polystyrenes, and the hetero‐arm star copolymers were characterized adequately, and their molecular weights were found to be in satisfactory agreement with expectation. The presence of some remaining linear precursor in the star polymer samples is discussed thoroughly on the basis of a detailed computerized analysis of the size exclusion chromatograms of both the star polystyrene samples and the hetero‐arm star copolymers.
Copolymerization of styrene and ethylene in the presence of different syndiospecific catalysts
Authors: Longo Pasquale , Grassi Alfonso , Oliva Leone
Published: April 2003

Some catalytic systems based on Ti or Zr compounds and methylalumoxane have been investigated with regard to their ability to promote styrene‐ethylene copolymerization. 13C NMR analysis shows that the structure and the composition of the copolymerization products are dependent on the catalytic system and on the transition metal/methylalumoxane mole ratio. Polymers containing phenylethylene units bridging polyethylene sequences are generally obtained in the presence of Ti‐based catalysts. In the presence of cyclopentadienyltitanium trichloride/methylalumoxane with high A1/Ti mole ratio one can obtain copolymers of ethylene and syndiotactic polystyrene. Zr‐based catalyst don't promote copolymerization at all.
Untersuchungen zur linearen thiol‐en‐photopolymerisation
Authors: Klemm Elisabeth , Sensfuß Steffi , Holfter Uta , Schütz Heidrun
Published: April 2003

The photoinitiated free‐radical polymerization of 3,6‐dioxa‐1,8‐octanedithiol and bis(allyl) hydroquinone ether or ethylene glycol divinyl ether leads to poly(thioethers) having anti Markovnikov structure with number‐average molar mass M̄n: 14000, 12000 g/mol, respectively. The chain propagation is limited by disulfide propagation is limited by disulfide production (nearly 3%) and cycle production (nearly 4 %). Differential scanning calorimetry (DSC) investigations showed that the rate of polymerization decreases in the series vinyl ether ≫ allyl ether > 1‐alkene. The influence of the dithiol structure (β‐mercapto ether, thioglycolate, aliphatic thiols) is not dominant.
Preparation of polyimide/polydimethylsiloxane graft copolymer and its permeabilities for gases and liquids
Authors: Nagase Yu , Mori Shigehiro , Egawa Masahiko , Matsui Kiyohide
Published: April 2003

Polyimide/polydimethylsiloxane (PI/PDMS) graft copolymers with various PDMS contents were prepared by polycondensation of PDMS macromonomer 1 with aromatic diamines and pyromellitic dianhydride followed by heating at 220°C. The PDMS content of the grafts copolymers was controlled by changing the average degree of polymerization of the PDMS macromonomer in the range between 4 and 21. Graft copolymer membranes were prepared by casting films in the poly(amic acid) stage 2 and subsequent imidation upon heating. PI/PDMS membranes thus obtained are insoluble. The permeability coefficients towards nitrogen, oxygen, hydrogen, methane and carbon dioxide were evaluated. In the region of a PDMS content above 50 wt.‐%, the oxygen permeability coefficient of a PI/PDMS graft copolymer membrane is > 10−8 cm3(STP) · cm · cm−2 · s−1 · cmHg−1. In addition, the permeability coefficient of methane is remarkably enhanced in comparison with a PI membrane. Preferential permeation of ethanol was observed through the graft copolymer membrane in the case of pervaporation of aqueous ethanol solution. Furthermore, acetone, acetonitrile and tetrahydrofuran were efficiently separated from water at any solvent/water ratio in the mixture.
Polymerization by [3 + 2] cycloaddition, 4. Polymers from hexafluoroacetone azine and diallylic compounds
Authors: Nuyken Oskar , Maier Gerhard , Burger Klaus
Published: April 2003

“Criss‐cross” cycloaddition polymerization between hexafluoroacetone azine and several diallylic compounds, such as diallyl ethers or diallyldimethylsilane, is described. In one case (with diallyl resorcinol ether) a polymer could be produced which is completely soluble in common organic solvents. The number‐average molar mass of this product is M̄n = 12000 g/mol. The expected structures of the polymers (or their soluble fractions) are confirmed by spectroscopic methods.
Synthesis, polymerization and copolymerization of 5‐methyl‐3‐methylene‐2‐pyrrolidone
Authors: Van Beylen Marcel , Samyn Celeste
Published: April 2003

A new lactam monomer containing a vinylidene group was synthesized, namely, 5‐methyl‐3‐methylene‐2‐pyrrolidone (4). The homopolymerization and copolymerization with methyl methacrylate and with styrene were studied. The copolymerization parameters r1 and r2 were also evaluated. Hydrolysis of the pendent lactam groups yields a polyelectrolyte (or homopolymer) with pendent γ‐amino acid units.
Thermotropic liquid‐crystalline polymers, 28. Structural transformation “nematic‐smectic A — reentrant nematic” in a comb‐like polymer and its mixture with a low‐molar‐mass liquid‐crystal compound
Authors: Kostromin Sergey G. , Shibaev Valery P. , Diele Siegmar
Published: April 2003

Comb‐like liquid‐crystalline polyacrylate, 1, containing 4′‐cyano‐4‐biphenylyl mesogenic groups and forming a reentrant nematic (Nr) phase, as well as its mixture with 4‐cyano‐4′‐hexyloxybiphenyl were studied by X‐ray diffraction. X‐ray diffraction patterns of magnetically‐oriented samples and the micro‐densitometer curves obtained from them allowed to observe the distortion of the layers with orthogonal packing of the mesogenic groups in the Nr phase. These results are compared with electrooptical data obtained earlier. As a result a domain formation with tilted arrangement of the mesogenic groups in the pseudolayer is proposed.
Study on epoxy network solid electrolytes
Authors: Ba Henfei , Peng Xinsheng , Qi Yuchen , Chen Donglin , Wang Fosong
Published: April 2003

Blends of the diglycidyl ether of poly(ethylene glycol) (1)

IUPAC name of1: α‐(2,3‐epoxypropyl)‐ω‐(2,3‐epoxypropoxy)poly(oxyethylene).

and the triglycidyl ether of glycerol (2)

IUPAC name of2: 1,2,3‐tris(2,3‐epoxypropoxy)propane.

were crosslinked in the presence of LiClO4which seems to act as both a catalytic curing agent and as the source of the ionic charge carriers. The cured film showed a rather high ionic conductivity of about 10−5S/cm at 25°C. The effect of composition, salt concentration and molecular weight of1on the conductivity and on the glass transition temperatureTgof the cured1/2LiClO4system was examined. The conductivity increased whereasTgdecreased with increasing1/2ratio. An increase of the molecular weight of1favoured the lowering ofTgand thus raised the conductivity. As to the effect of LiCIO4concentration, the maximum conductivity occurred at about 5 wt.‐% of LiClO4andTgincreased with increasing LiClO4content. The temperature dependence of the conductivity followed the Vogel‐Tamman‐Fulcher equation. This indicated that the ionic conductivity is effected by the cooperative segmental motion. All of the prepared specimens were found to be amorphous. They were mechanically strong films and showed rubber‐elasticity at room temperature.
Ordered odd‐number terpolyamides, 2. Crystal structure
Authors: Prieto Arcadi , Coutin Bernard , Sekiguchi Hikaru , Subirana Juan A. , Guerra Sebastián Muñoz
Published: April 2003

A combined X‐ray diffraction and electron microscopy study was carried out on both the solution‐grown crystals and oriented films of nylons 3/5/7 and 7/5/3. These regular odd‐odd‐odd terpolyamides have such sequence of amide groups along the chain that they have to be aligned parallel in order to form every hydrogen bond without strain. It was found that a layered α‐structure with hydrogen‐bonded sheets made up of parallel chains in fully extended conformation is adopted in both cases. These results are not necessarily generalized to odd‐numbered nylons where an antiparallel alignement of chains is compatible with the formation of hydrogen bonds. Chain‐folded lamellar crystals obtained from solution were investigated by electron diffraction and their surface topology examined by polymer decoration with polyethylene. A bimodal orientation of hydrogen‐bonded sheets within the lamella is assumed to occur in order to account for the obtained decorating patterns. Either way, chain foldings are not contained in such sheets but intersect them at an angle of about 60°.
A DSC study on miscible blends containing two crystalline components: poly(ε‐caprolactone)/poly[3,3‐bis(chloromethyl)oxetane]
Authors: Guo Qipeng
Published: April 2003

Blends of poly(ε‐caprolactone) (PCL) with poly[3,3‐bis(chloromethyl)oxetanel] (Penton) were prepared by casting from a common solvent. All blends show a single, composition‐dependent glass transition temperature (Tg), indicating that the blends are miscible in the amorphous state and in the melt. The crystallization rate of PCL in the blend decreases with increasing Penton content, that of Penton decreases with increasing PCL content. The crystallinity index of PCL in the blend decreases with increasing Penton content owing to the enhanced Tg of the system, whereas that of Penton does not depend on composition. The interaction parameter B of the two polymers in the melt was found to be −15 J/cm3.
Preparation of sodium 5‐methyl‐3,7‐octadienoate and its polymerization under irradiation with UV light
Authors: Arai Kenichiro , Miyahara Shigeyoshi
Published: April 2003

Sodium 5‐methyl‐3,7‐octadienoate (2) was synthesized as an amphiphile which contains a double bond at the chain end. The micelle formation behaviour of 2 was examined by measuring the electric conductivity of its aqueous solutions; the pre‐critical micelle concentration (pre‐CMC) and the genuine critical micelle concentration (CMC) were estimated to be 0,09 and 0,23 mol · 1−1, respectively. Polymerization of 2 under irradiation with UV light was investigated, and it was found that practically no polymer is obtained at concentrations lower than the pre‐CMC, while the amount of polymer obtained increases rapidly with increasing concentration of 2 in the polymerization system at concentrations higher than the pre‐CMC. The number‐average degree of polymerization of poly(2) is about 6. Pre‐CMC and CMC of poly(2), which are inferred to correspond to the concentrations to start intra‐ and intermolecular aggregation, are 1,2 · 10−3 and 9,4 · 10−3 mol · 1−1, respectively. These results are compared with those of sodium 10‐undecenoate.
Elektronenmikroskopische untersuchungen zum monomer‐volumenanteil in polyvinylchlorid‐latexpartikeln im verlauf der emulsionspolymerisation
Authors: Paulke Bernd‐R. , Tauer Klaus , Büchtemann Andreas , Müller Ingo , Schulz Eckhard
Published: April 2003

Monomer‐swollen poly(vinyl chloride) latex particles directly taken from emulsion polymerization were fixed and stained with a dilute solution of osmium tetroxide. The particle size distribution of this dispersion was compared with that of the corresponding monomer‐free latex by transmission electron microscopy. The monomer volume fractions of the particles ϕM were calculated in dependence of their diameter (d). Smaller particles contain more vinyl chloride than larger ones under the experimental conditions adjusted. The mean value of the monomer volume fraction agrees with experimental data published by Berens and Nilsson. The equation of Morton, Kaizerman and Altier was used to estimate the Flory‐Huggins interaction parameter χ. An upper and a lower limit for χ was calculated applying the experimental values of d and ϕM in the particle size range investigated. The real χ for the particles observed lies between these limits.
Kinetic and statistical derivation of the copolymerization equation
Authors: Farina Mario
Published: April 2003

A critical analysis of the various methods of derivation of the copolymerization equation leads to the following conclusions: the steady‐state assumption is not a necessary condition for the “kinetic” derivation; all known methods of derivation are implicitly or explicitly related to the condition of chain continuity; other methods, simpler than the traditional ones, are reported in the literature and deserve more attention.
Polyarylenes and poly(arylenevinylene)s, 3. Oligomeric model compounds for poly(9,10‐anthrylenevinylene)
Authors: Weitzel Hans‐Peter , Bohen Angelika , Müllen Klaus
Published: April 2003

Some reactions for the synthesis of poly(phenylenevinylene), PPV, are examined for their capability to form poly(9,10‐anthrylenevinylene). The reasons for the failure of these reactions are described. Soluble oligomers with up to seven anthracene units are synthesized. The properties of the oligomers are studied and conclusions for the properties of poly(9,10‐anthrylenevinylene), PAV, are drawn.
Chemical modification of polymer main chain — A new path to liquid‐crystalline polyesters with long siloxane segments. Significance of molecular mobility in the formation of the liquid‐crystalline state
Authors: Zuev Vjacheslav V. , Smirnova Galina S. , Nikonorova Natalja A. , Borisova Tamara I. , Skorokhodov Sergei S.
Published: April 2003

A new method for the synthesis of polymers incorporating dimethylsiloxane fragments of different length based on chemical modification of liquid‐crystalline poly[oxy(dimethylsilylene)‐methyleneoxycarbonyl‐1,4‐phenyleneoxyterephthaloyloxy‐1,4‐phenylenecarbonyloxymethylene‐(dimethylsilylene)] (polymer 1) is described. A series of thermotropic LC polymers 2 with extended dimethylsiloxane segments (up to 10 Si atoms per siloxane spacer) was synthesized by means of the reaction of prepolymer 1 with octamethylcyclotetrasiloxane in the presence of a sulfocation exchanger. Investigation of the dielectric properties of the polyesters 2 revealed that there exists a relationship between the ability of the polymers to form a mesophase and their molecular mobility parameters.
Synthesis of polysiloxanes with pendant viologen groups and their characteristic behavior of aggregation and deposition observed on electron transfer
Authors: Yamada Kazunobu , Ueno Yukihiko , Ikeda Koji , Takamiya Nobuo , Kaneko Masao
Published: April 2003

In order to prepare polysiloxanes with the ability of electron transport, pendant viologen groups were introduced. Chloromethylated poly(methyl‐β‐phenethylsiloxane) (2) was reacted with monoalkylbipyridinium chlorides (3a, 3b) to give polysiloxanes (4a, 4b) containing pendant viologen groups. These polymers show reversible redox behavior. They are deposited on ITO electrodes when the pendant viologen dication groups are electrochemically reduced to cation radicals. The polymer deposited shows an absorption maximum (λmax) at 500 nm, which is due to a highly aggregated structure of cation radicals. On the contrary, when the electrode was coated by the polymer before the measurement (pre‐cast membrane), the cation radicals formed electrochemically show λmax at 530 nm, indicating that the degree of aggregation is lower than that in the membrane formed reductively from solution.
N‐substituted aldonamides, 4. Phase behaviour in aqueous solution of monomers and polymers with alkylaldonamide side chains — comparison with model compounds
Authors: Loos Manon , Baeyens‐Volant Danielle , Szalaï Eva , David Christiane
Published: April 2003

N‐substituted polymethacrylamides with mesogenic side chains of formula (CH2)n NHCOR′ where R′ is derived from ribose, have been synthetized. Thermotropic and lyotropic properties of the monomers, polymers, and copolymers with butyl acrylate have been investigated.
Lösungsmittelabhängigkeit der Bruttopolymerisationsgeschwindigkeit bei der radikalischen Copolymerisation von donator‐ und Acceptormonomeren
Authors: Schmidt Hermann , Schmidt‐Naake Gudrun , Berger Werner
Published: April 2003

The influence of the solvent on the reactivity ratios in free‐radical copolymerization of donor monomers with acceptor monomers is very strong. The copolymerization reactivity ratios decrease with increasing donor number and dielectric constant of the solvent. This can be rationalized on the basis of the complex stability constant of the two monomers as compared with those of the monomers and the solvent.
Modellselektion bei der Copolymerisation ternärer Donator‐Acceptor systeme
Authors: Schmidt‐Naake Gudrun , Schmidt Hermann , Litauszki Beata , Berger Werner
Published: April 2003

The free‐radical copolymerization of donor, acceptor and neutral monomers to ternary copolymers is studied. It is shown that the composition of the ternary copolymers can be calculated from their monomer feed, in case the reactivity ratio (r) values of the three binary subsystems are known. The calculation based on the copolymer equation only considers really existing propagation steps.
Polyether‐1,2‐ and ‐1,3‐diols as macromonomers for the synthesis of graft copolymers, 1. Synthesis and characterization of the macromonomers
Authors: Fock Jürgen , Möhring Volker
Published: April 2003

This article describes the synthesis and characterization of a new type of macromonomers, which can be used in condensation and addition reactions affording graft copolymers. The polyether‐based macromonomers having two hydroxyl groups at one chain end were synthesized by anionic alkoxylation of hydroxy‐functional cyclic ketals, blocking by Williamson reaction and cleavage of the ketal. Moreover, the synthesis and characterization of such macromonomers having sulfonate and perfluoroalkyl end groups, respectively, were performed. Yields were influenced by side reactions depending on the type of epoxide used and the final molecular weight of the macromonomer.
Compatibility of poly(N‐vinyl‐2‐pyrrolidone) with ethyl methacrylate/2‐hydroxyethyl methacrylate copolymers
Authors: Goh Suat Hong , Lee Swee Yong
Published: April 2003

The compatibility of poly(N‐vinyl‐2‐pyrrolidone) (PVP) with ethyl methacrylate/2‐hydroxyethyl methacrylate (EMA/HEMA) copolymers of varying HEMA contents was studied by differential scanning calorimetry. PVP is incompatible with EMA/HEMA copolymers with HEMA contents of 2,1 and 5,7 mol‐%, but is compatible with copolymers with HEMA contents of 7,5, 10,0 and 18,2 mol‐%. TheTg‐composition curves of three compatible systems can be fitted by the Gordon‐Taylor equation.
Liquid‐crystalline polysiloxanes with fluorene units, and related monomeric compounds
Authors: Koßmehl Gerhard , Schulz Michael , Vieth Hans‐Martin
Published: April 2003

The synthesis of the liquid‐crystalline polysiloxanes, 4a, 4b, 5a, 5b with 2,7‐disubstituted fluorene units and of the related liquid‐crystalline model compounds 2 and 3 is reported. Polymers 4a, 4b, 5a, 5b were prepared from monomers 2 and 3, respectively, and poly(hydrogenmethyl‐siloxane) (PHMS) in a polymer‐analogous reaction. The liquid‐crystalline properties of the polymers and the corresponding low‐molecular‐weight compounds 2 and 3 were characterized by differential scanning calorimetry (DSC) and polarizing microscopy. Both compounds 2 and 3 show a smectic A and a smectic E mesophase, and the resulting polysiloxanes also exhibit smectic A‐ and smectic E‐like textures but no nematic phase. The clearing point of the polymers is on the average by 100°C higher than that found for the low‐molecular‐weight compounds.
Study of heterocyclic polymers, 2. Model reactions of 2‐pyridinecarboxylic acid with glycidyl phenyl ether
Authors: Hsu Ying Gev , Hsu Miau Jing , Chen Keng Ming
Published: April 2003

The reaction of 2‐pyridinecarboxylic acid (picolinic acid, PA) with 2,3‐epoxypropyl phenyl ether (glycidyl phenyl ether, GPE) was studied by means of high performance liquid chromatography (HPLC). It was found that the reaction between PA and GPE is quite different from that between nicotinic acid (NA) or isonicotinic acid (ISNA) and GPE, and does not obey the kinetics of second or other order; hence the rate constant of the reaction cannot be obtained. The reaction may be described by a three‐step mechanism. PA reacts first with GPE to yield N‐(2‐hydroxy‐3‐phenoxypropyl)pyridinium‐2‐carboxylate (PA‐1). PA‐1 is then decarboxylated to form an ylide. The ylide reacts immediately with PA to yield N‐(2‐hydroxy‐3‐phenoxypropyl)pyridinium picolinate (NPP). NPP subsequently catalyzes the reaction between PA and GPE, with 2‐hydroxy‐3‐phenoxypropyl picolinate (PA‐2) as a product. Because the concentration of NPP increases with time, the rate of reaction between PA and GPE is increasing with time. The mechanism of the reaction is discussed in detail.
Pyrolysis gas chromatographic studies on polyphosphate esters of bisphenol A
Authors: Annakutty Kunnappallil S. , Kishore Kaushal
Published: April 2003

Pyrolysis gas chromatographic studies were carried out on two polyphosphate esters of bisphenol A

Systematic name: 2,2′‐isopropylidendiphenol.

. The gaseous pyrolysis products were found to be mainly phenols and a few phosphate compounds. The identification of phosphorus compounds in the gas phase proves a gas phase mechanism of flame retardant action for polyphosphates. The presence of phosphoric acid in the char residue supports the existence of the conventional condensed‐phase mechanism. Thus, the study demonstrates that both condensed‐phase and gas‐phase mechanisms are operative in the flame‐retardant action of polyphosphates.
Regular odd‐number terpolyamides, 1. Synthesis
Authors: Coutin Bernard , Sekiguchi Hikaru , Prieto Arcadi , Muñoz‐Guerra Sebastián
Published: April 2003

In order to improve our comprehension of the crystalline structure of polyamides, two regular odd terpolyamides containing 3‐aminopropanoyl, 5‐aminopentanoyl and 7‐aminoheptanoyl units were prepared by the active ester polycondensation method. The choice of the sequencing order in the starting compounds (called here heterotrimers) and the various routes leading to them are discussed. It was found that both the reactions and the purification of intermediates were most conveniently performed by combining the heterodimer of the lower amino acids with the higher amino acid. The polycondensation was carried out through a multiple step process either in solution or in the solid‐state at a temperature below 200°C. 13C NMR spectra showed that no rearrangement during the polycondensation occurs under these conditions. The terpolyamides have sufficiently high molecular weights to provide good films for crystallographic studies. The two terpolyamides of inversed order do not cocrystallize even when coprecipitated from a solution, probably because of their different crystalline structures.
Propene polymerization in the presence of MgCl2‐supported Ziegler‐Natta catalysts, 4.. Effects of Lewis bases on polymer stereochemistry
Authors: Busico Vincenzo , Corradini Paolo , Martino Luigi De , Graziano Flavia , Iadicicco Annamaria
Published: April 2003

The stereochemistry of polypropenes obtained in the presence of several MgCl2‐supported Ziegler‐Natta catalyst systems comprising different Lewis bases has been investigated by 13C NMR spectroscopy, with special attention paid to the “less tactic” (heptane‐soluble) fractions. These have been found to consist of “tendentially isotactic” and “tendentially syndiotactic” stereosequences, in largely variable amounts (depending on the catalyst system). The microstructure of the former is in accordance with the enantiomorphic site model, whereas that of the latter suggests a stereocontrol arising from the asymmetry of the growing chain end. In both cases, propene insertion is primary (1–2). Polymerization conditions leading to the formation of “syndiotacticrich” polymers showing syndiotactic crystallinity have been identified.