bluuebunny/crossref_metadata_2025 huggingface dataset:
Living cationic polymerization of isobutyl vinyl ether by trimethylsilyl halide/zinc halide initiating systems: effects of carbonyl compounds
Authors: Kamigaito Masami , Sawamoto Mitsuo , Higashimura Toshinobu
Published: April 2003

Effects of carbonyl compounds [acetone, acetophenone, and benzaldehydes (p‐MeO, p‐NO2, and unsubstituted)] were investigated in the polymerization of isobutyl vinyl ether (IBVE) by trimethylsilyl halide/zinc halide (Me3SiX/ZnX2; X = I, Br, Cl) initiating systems in toluene at −15°C. In the presence of acetone and the three benzaldehydes, Me3Sil/Znl2 induced living cationic polymerization, where the number‐average molecular weights (M̄n) of the polymers increased proportionally to monomer conversion and agreed with the calculated values on the assumption that one living polymer per molecule of Me3SiI is formed. The molecular weight distributions (MWDs) stayed very narrow (M̄w/M̄n ≤ 1,1) throughout the reaction. With acetophenone, the M̄n values were larger than the calculated values and the MWDs were slightly broader. For less reactive silyl halides, Me3SiBr and Me3SiCl, p‐MeO‐benzaldehyde gave better results in terms of M̄n values and MWDs than unsubstituted benzaldehyde. 1H NMR analysis of the polymer end structure and the products of model reactions has shown that the initiation occurs via a silyloxycarbocation (Me3SiOC+R1R2 · X−) that is generated by a reaction of Me3SiX with carbonyl compounds.
Thermodynamics of hexanal, its bulk polymerization and polyhexanal from 0 to 340 K at standard pressure
Authors: Lebedev Boris , Vasil'yev Valery , Novosyolova Nina
Published: April 2003

In the present work the enthalpy, entropy and Gibbs function were obtained from calorimetric results, for the bulk polymerization of hexanal in the temperature range from 0 to 330 K at a pressure of p = 101,325 kPa. The physical transitions of hexanal between 11 and 340 K and polyhexanal from 5 to 340 K were studied in a vacuum adiabatic calorimeter, and the corresponding thermodynamic parameters of the monomer and the polymer were determined. From the results obtained the thermodynamic functions of hexanal and polyhexanal were calculated in the range from 0 to 340 K. In a differential automatic microcalorimeter the enthalpy of depolymerization of polyhexanal in acetic acid to the initial monomer was directly measured. The ceiling temperatures of the transition processes of the liquid monomer into the crystalline and highelasticity polymer were estimated.
Crystallinity of uniform triblock oxyethylene/methylene/oxyethylene (EmCnEm) oligomers studied by X‐ray diffraction, differential scanning calorimetry and Raman spectroscopy
Authors: Campbell Carl , Viras Kyriakos , Richardson Michael J. , Masters Andrew J. , Booth Colin
Published: April 2003

Uniform triblock oligomers with a central methylene block and outer oxyethylene blocks terminated by methoxy groups, CH3(OCH2CH2)mO(CH2)n(OCH2CH2)mOCH3 (EmCnEm), were prepared and studied in the solid state by X‐ray diffraction, differential scanning calorimetry and Raman spectroscopy. Both fully crystalline and partly‐crystalline structures were found, with chains in wholly trans‐planar and mixed‐trans‐planar/helical conformations. Comparison is made with previous results for triblock oligomers of type CnEmCn and diblock oligomers of type CnEm.
The anionic polymerization of acrylates, 5. Controlling the molecular weights in the polymerization of 2‐ethylhexyl acrylate initiated by the mixed initiator lithium ester‐enolate/lithium tert‐butoxide
Authors: Vlček Petr , Otoupalová Jaroslava , Kříž Jaroslav
Published: April 2003

In the anionic polymerization of 2‐ethylhexyl acrylate the possibility of controlling the molecular weights of the resulting polymers by varying the initial stoichiometric conditions was studied. The starting concentrations of monomer and initiator, tert‐butyl 2‐lithioisobutyrate, were varied in the range 0,24–1,20 mol/L and 0,006–0,017 mol/L, respectively, so that the mole ratio [M]0/[I]0 spanned the range from 14 to 160. The mole ratio tert‐butyl 2‐lithioisobutyrate: Li tert‐butoxide was 1 : 3 in all experiments. A Mixture toluene/tetrahydrofuran (volume ratio 9 : 1) was used as reaction medium. The molecular weights of the polymers formed (37 00–55 000) depend linearly on the ratio [M]0/[I]0. All products have narrow molecular‐weight distributions. The efficiency of the initiator is not quantitative, but in the range investigated it does not depend markedly on the concentration conditions. NMR analysis of the polymers indicates that the polymerization is initiated by Li ester‐enolate and any metal transfer from the initiator to the monomer can be neglected. The polymerization is shown to proceed by the mechanism which is close to the ideal “living” process.
Coordination polymerization of lactides, 3. Copolymerization of L,L‐lactide and ε‐caprolactone in the presence of initiators containing Zn and Al
Authors: Bero Maciej , Kasperczyk Janusz , Adamus Grazyna
Published: April 2003

High‐molecular‐weight copolymers of L,L‐lactide with ε‐caprolactone were synthesized using initiators containing aluminium and zinc, i.e., AlEt2OEt, ZnEtOiPr, Al(acac)3 and AlEt3 + ZnEt2 + H2O. The chain microstructure was revealed to vary from random to diblock arrangement, depending on temperature and the kind of initiator used. In case of Al(acac)3 as initiator, the reactivity ratios of L,L‐lactide and ε‐caprolactone were determined to be rL = 44 and rC = 0,28, respectively.
Coordination polymerization of lactides, 4. The role of transesterification in the copolymerization of L,L‐lactide and ε‐caprolactone
Authors: Kasperczyk Janusz , Bero Maciej
Published: April 2003

Two modes of transesterification in copolymerization of L,L‐lactide with ε‐caprolactone in the presence of initiators containing Al and Zn were found. The quantitative analysis of the contributions of both types of transesterification reactions is revealed. The transesterification ability of initiators containing zinc is greater than that of initiators containing aluminium. Decrease of the reaction temperature tends to reduce both the first and the second mode of transesterification, leading to an elongation of blocks in the copolymer chains.
Fluorinated gels for gel permeation chromatography
Authors: Juhl Hans‐Jürgen , Heitz Walter
Published: April 2003

The aim of these investigations was the development of stationary phases for GPC compatible with fluorinated solvents. The properties of crosslinked copolymers of 4‐(2‐heptafluoropropoxy‐1, 2,2‐trifluoroethoxy)styrene (1) were investigated in dependence of the mode of synthesis. Divinylbenzene (DVB) was used as crosslinking agent. In the case of homogeneously crosslinked gels, 1 mol‐% of DVB results in a gel with an exclusion molecular weight of 2000. Heterogeneous crosslinking copolymerization of 1 with DVB in presence of inert diluents results in gels with exclusion limits from 5000 to 4000000 in dependence of the diluent composition. Characterization of the gels in GPC experiments was carried out with 2‐(1,2‐dibromotrifluoroethoxy)‐1,1,2,3,3,3‐hexafluoro‐1‐(perfluoropropoxy)propane (PPVE2Br2), hexafluorobenzene, 1,1,2‐trichlorotrifluoroethane (FrigenR113) and trifluoromethylbenzene as eluents.
Doping of poly(phthalidylidenearylene)s. Interaction of iodine with poly(3,3′‐phthalidylidene‐4,4′‐biphenylylene)
Authors: Novoselov Igor V. , Zolotukhin Mikhail G. , Nikiforova Galina I. , Kapina Alevtina P. , Shishlov Nikolai M. , Latchinov Aleksei N. , Sangalov Yuri A.
Published: April 2003

Interactions of iodine with films prepared from poly(3,3′‐phthalidylidene‐4,4′‐biphenylylene) (PPB) were studied by IR, far‐IR and UV spectroscopy. The carbonyl group of the lactone cycle was found to play a main role in the complexation of iodine with PPB. Iodine incorporated into the polymer transforms into polyiodide ions ( I, n = 1 − 3). Various polyiodides, along with complexed iodine (I2comp), may exist in the polymer at a time, and can be transformed into each other, depending on ambient conditions. The process of doping is almost completely reversible. After removal of iodine from the polymer by heating, the latter restores its starting properties.
Concentration dependence in the transport of alkali metal ions against their concentration gradient across cation exchange membranes
Authors: Uragami Tadashi , Tamura Tomoko
Published: April 2003

The kinetics of the transport of alkali metal ions such as Li+, K+, Na+ against their concentration gradient across cation exchange membranes such as poly[isobutylene‐alt‐(maleic anhydride)] (ISBN) and poly(styrenesulfonic acid) (PSA) membranes was studied. The transport for these ions through these membranes obeyed the Michaelis‐Menten equation at the initial stage. The affinity of alkali metal ions to a carboxy group which is a carrier in the ISBN membrane and to a sulfo group which is a carrier in the PSA membrane is in the order K+ > Na+ > Li+. This order agrees with a selective transportability of alkali metal ions through these membranes.
Ziegler‐Natta oligomerization of 1‐alkenes: a catalyst's “fingerprint”, 1. Hydrooligomerization of propene in the presence of a highly isospecific MgCl2‐supported catalyst
Authors: Busico Vincenzo , Cipullo Roberta , Corradini Paolo
Published: April 2003

The stereochemistry of propene polyinsertion catalyzed by a highly isospecific MgCl2‐supported Ziegler‐Natta system was investigated by means of the gas chromatographic/mass spectrometric (GC‐MS) characterization of the saturated oligomers (hydrooligomers) formed in the presence of H2 at high pressure (as a chain transfer agent). It was shown that the hydrooligomer distribution is a true catalyst “fingerprint”, from which, in case of systems with (prevailingly) a single type of active centres, both the regio‐ and the stereospecificity of polyinsertion can be quantitatively evaluated.
Copolymer‐monomer miscibility during copolymerization
Authors: El‐Begawy Salah E. M. , Huglin Malcolm B.
Published: April 2003

Significant drift in the compositions of copolymer and of unreacted monomer mixture is predicted to occur during the bulk copolymerization of N‐vinyl‐2‐pyrrolidone (VP) with butyl acrylate (BA), when the inital feed mixture contains 75 wt.‐% VP. The drift in copolymer composition has been confirmed by 1 the optical appearance and glass transition (Tg) behaviour of the products of the γ‐ray initiated copolymerization at various fractional conversions (C) and 2 the Tg behaviour of low‐conversion samples of poly(VP‐co‐BA) blended in propertions so as to simulate the overall composition of material that would be present cumulatively at selected values of C during an actual copolymerization. The compositions of unreacted monomer mixtures co‐existing with copolymer at selected conversions have been calculated and intrinsic viscosities [η] of blends dissolved in these VP/BA mixtures have been measured. Theta conditions for the blends have been established turbidimetrically in chloroform/heptane and the corresponding values of [η]Θ measured. The chain expansion factors thereby derived from [η] and [η]Θ show a decreasing affinity of copolymer for residual monomer during the course of copolymerization.
New side‐group liquid‐crystalline polymethacrylates
Authors: Rodekirch Gerhard , Rübner Joachim , Zschuppe Veit , Wolff Dietmar , Springer Jürgen
Published: April 2003

A new route of synthesis of liquid‐crystalline polymethacrylates was investigated. The synthetic route involved side‐group liquid‐crystalline polymethacrylates (LCPMA) with a turned ester group between the aromatic rings in the central unit of mesogens (2) as compared with the usual LCPMA (1). For a series of compounds of this type the liquid‐crystalline properties were investigated using differential scanning calorimetry, polarizing microscopy and X‐ray diffraction techniques. Generally stable smectic phases were found for these isomeric LCPMA. The described synthetic route opens possibilities to form new polymers from a wide field of educts.
The β‐relaxation in low‐molecular‐weight and in polymeric side group ferroelectric liquid crystals
Authors: Schönfeld Axel , Kremer Friedrich , Hofmann Achim , Kühnpast Kurt , Springer Jürgen , Scherowsky Günther
Published: April 2003

Dielectric spectroscopy in the microwave regime (106–1010 Hz) is employed to study the molecular dynamics of a set of ferroelectric liquid‐crystalline side group polymers with variable spacer length and different molecular weight, and on their low‐molecular‐weight counter‐part. One relaxation process is observed, the β‐relaxation, which is assigned to the hindered rotation of the mesogens around their long molecular axis. This librational process is nearly uninfluenced by the molecular weight and depends only slightly on the spacer length. At the smectic‐smectic phase transition SA/SC* the β‐relaxation does not decrease in its relaxation strength and shows no slowing down of its relaxation rate. This is in pronounced contrast to the common explanation of the origin of ferroelectricity in liquid crystals and requires a new interpretation.
Synthèse de diamines aromatiques macromoléculaires à basicité controlée à partir de poly(tétraméthylène glycol)
Authors: Bougherara Chaabane , Boutevin Bernard , Robin Jean‐Jaques
Published: April 2003

This study describes the synthesis of poly(tetramethylene glycol) with amino end‐groups on both sides by chemical end modification. For this purpose, α‐hydro‐ω‐hydroxypoly(oxytetramethylene) and α‐propyl‐ω‐(3‐aminopropoxy)poly(oxytetramethylene) are converted into aromatic diamines with controlled basicity. For this, different chemical reactions are performed in order to obtain different links between aromatic amines and poly(oxytetramethylene). This method leads to products which present pKavalues between 2,8 and 5,26 in accordance with theoretical values.
Trägerkatalysatoren aus C12‐allylnickel(II)‐komplexen [Ni(C12H19)]X (X = SbF6, O3SCF3) und amorphem aluminiumfluorid in toluol als modell‐katalysatoren für das technische katalysatorsystem Ni(octanoat)2/BF3·OEt2/AlEt3 zur 1,4‐cis‐polymerisation des butadiens
Authors: Taube Rudolf , Langlotz Jochen , Müller Gert , Müller Jörn
Published: April 2003

The η3, η2, η2‐dodeca‐2(E), 6(E), 10(Z)‐trien‐1‐yl‐nickel(II) complexes [Ni(C12H19)]X (X = SbF6, O3SCF3) were treated in toluene with amorphous aluminium trifluoride (which was prepared from AlEt3 and BF3 · OEt2) in a mole ratio 1 : 10 to 20, forming a highly active catalyst for the 1,4‐cis polymerization of butadiene. This catalyst is comparable in its activity and selectivity, and in the molar mass distribution of the polybutadiene, with the technical nickel catalyst Ni(O2CR)2/BF3ċOEt2/AlE3 developed by Bridgestone Tire Company thirty years ago. The existence of the C12‐allynickel(II) cation [Ni(C12H19)]+ on the AlF3 support could be proved by FAB mass spectroscopic measurements. In agreement with our reaction model for the allyl nickel complex catalyzed butadiene polymerization, it is concluded that the technical nickel catalyst in its effective structure can be described as a polybutadienylnickel(II) complex co‐ordinated to a polymeric fluoroaluminate anion via a fluoride bridge.
Bright field image of banded texture in lyotropic liquid crystals of a polydiacetylene
Authors: Wang Wei , Lieser Günter , Wegner Gerhard
Published: April 2003

Formation of a banded texture was observed in thin films of a polydiacetylene prepared from the lyotropic nematic phase subject to flow. The banded texture was experimentally investigated by polarizing light microscopy and transmission electron microscopy. The banded structure is initially formed in a nematic phase of the polymer and could be imaged by TEM after its transformation to a lamellar phase which is the polymer analogon to a smectic phase in low‐molecular‐weight compounds. A mathematical description of the texture is given. During further relaxation of the system in the lyotropic state the initial orientation is lost by the formation of disclinations.
Synthesis and side‐chain crystallization of comb‐like polymers obtained from isopropenyl‐1,3,5‐triazines carrying two, three, and four long alkyl groups
Authors: Kunisada Hideo , Yuki Yasuo , Kondo Shuji , Goto Ken‐ichi
Published: April 2003

Monomers containing several octadecyl groups, e.g., 2‐isopropenyl‐4,6‐bis(octadecylamino)‐1,3,5‐triazine (2), 2‐dioctadecylamino‐4‐isopropenyl‐6‐octadecylamino‐1,3,5‐triazine (3) and 2,4‐bis(dioctadecylamino)‐6‐isopropenly‐1,3,5‐triazine (4) were prepared by the alkylation reaction of 2,4‐diamino‐6‐isopropenyl‐1,3,5‐triazine (1) with 1‐bromooctadecane in the presence of sodium hydride. In the free‐radical homopolymerization of these monomers, the polymer yield of 3 was lower than that of 2 due to a decrease in the ceiling temperature, and the polymerization of 4 did not proceed. Copolymerizations of these monomers with styrene or methyl methacrylate were carried out and the monomer reactivity ratios (r1 and r2) were determined. The monomer reactivity decreased with increasing the number of octadecyl groups in the monomers. Crystallinity of the octadecyl side chains in the resulting comb‐like polymers was evaluated by differential scanning calorimetry.
Preparation and characterization of poly(methyl‐3,3,3‐trifluoropropylsiloxane‐co‐dimethylsiloxane)
Authors: Kobayashi Hideki , Nishiumi Wataru
Published: April 2003

Methyl‐3,3,3‐trifluoropropylsiloxane (F)‐dimethylsiloxane (D) random and block copolymers were prepared. The random copolymers were prepared by equilibrium copolymerization starting from a mixture of cyclic F and D siloxanes with potassium silanolate as the catalyst. The F‐D block copolymer was prepared by sequential anionic living polymerization of strained cyclic trisiloxanes using butyllithium as initiator, first polymerizing D3 then adding F3 after consumption of D3. The copolymer microstructure was established by means of 29Si NMR, differential scanning calorimetry (DSC), and gel‐permeation chromatography (GPC). Characteristic glass transition temperature (Tg) shifts were observed depending on the F:D ratio of the random copolymers. It was demonstrated that the tensile strength of the poly(methyl‐3,3,3‐trifluoropropylsiloxane)‐poly(dimethylsiloxane) (PTFPMS‐PDMS) blend system was improved when either of the copolymers was added.
Synthesis of chromophore‐labelled polystyrene/poly(ethylene oxide) diblock copolymers
Authors: Caldérara Frédŕic , Hruska Zdenek , Hurtrez Guy , Nugay Turgut , Riess Gérard , Winnik Mitchell A.
Published: April 2003

Polystyrene/poly(ethylene oxide) diblock copolymers bearing anthracene or phenanthrene groups at the block junctions were synthesized by sequential anionic polymerization using cumylpotassium as initiator. Labelled copolymers were characterized by means of ultraviolet (UV) spectroscopy, gel‐permeation chromatography (GPC) and 1H NMR spectroscopy. The solutions of the prepared copolymers in water and 1,2‐dichloroethane/methanol mixtures were studied by fluorescence spectroscopy. The intermolecular energy transfer process confirms the presence of organized structures (micelles) in solutions.
NMR evidence of the block structure of poly(methyl methacrylate)‐block‐poly(ethyl acrylate) prepared by group transfer polymerization
Authors: Kříž Jaroslav , Masař Bohumil , Vlček Petr
Published: April 2003

The structure of poly(methyl methacrylate)‐block‐poly(ethyl acrylate) prepared by group transfer polymerization was studied by 1H and 13C 1 D and 2D NMR methods including SINEPT, COSY, LR H‐H‐C RELAY and COLOC using model homopolymers of methyl methacrylate (MMA) and ethyl acrylate (EA) of a length equal to that of the blocks and prepared under the same conditions. The 1H and 13C spectra of the copolymer are shown to be a superposition of the respective spectra of the homopolymers, with the exception that the copolymer lacks the terminal group present in the MMA homopolymer and the initiating group of the EA polymer. Moreover, a new minor signal is found in the CH2 region of the copolymer which is shown to belong to the link of the blocks. The existence of a direct link between the blocks is further supported by the results of 1D and 2D coherence transfer methods, especially, those using the newly modified DS INEPT and H‐C‐C RELAY pulse sequences.
The polymerization of acrylonitrile by tetraaziridotitanium(IV)
Authors: Billingham Norman Ć. , Lees Peter D.
Published: April 2003

The polymerization of acrylonitrile by tetraaziridotitanium(IV) is very much more rapid than the same reaction initiated by tetrakis(dimethylamino)titanium(IV). The former reaction has dead‐end kinetics but both can be fitted with the same kinetic scheme. Polymerization is accompanied by initiator wastage via unidentified reactions. Insertion of saturated nitriles into the TiN bonds of tetrakis(dimethylamino)titanium can be monitored by NMR and gives products with high activity for the polymerization of acrylonitrile. Despite their high reactivity towards acrylonitrile none of the initiators will polymerize less reactive monomers.
Solution properties and light scattering measurements of poly(2,5‐pyrimidinediylterephthalamide)
Authors: Oertli Alfred G. , Schurtenberger Peter , Suter Ulrich W.
Published: April 2003

A Series of chains of different molecular weight of the fully aromatic polyamide poly(2,5‐pyrimidinediylterephthalamide)

IUPAC name: poly(2,5‐pyrimidinediyliminoterephthaloylimino).

(PPYMT) in the solvents 96 wt.‐% sulfuric acid and methanesulfonic acid have been characterized by means of static and dynamic light scattering, dilute solution viscosimetry and measurements of the critical polymer volume fraction for the onset of a nematic phase. The experimental results are in good agreement with a model of stiff worm‐like chains for the solution conformation of PPYMT, and the persistence length is estimated to be ca. 150 Å (lower limit: 50–100 Å).
Comb‐like poly(aryl‐ether‐ketones) containing naphthalene moieties in the main chain
Authors: Ritter Helmut , Thorwirth Ralf , Müller Gerd
Published: April 2003

1,5‐Naphthalenediol was alkoxylated with 1‐alkyl bromides containing 3‐16 C‐atoms and then acylated with 4‐fluorobenzoyl chloride under Friedel‐Crafts conditions in 4‐ and 8‐position of the naphthalene ring. These new difluorides (3a–d) were condensated with hydroquinone, bisphenol‐A and 4,4′‐biphenyldiol, yielding the corresponding poly(aryl‐ether‐ketones) 4a–d, 5a–d and 6a–d. The melting points of both the difluorides and the poly(aryl‐ether‐ketones) decreased with increasing side chain length. The molecular weights of some of the poly(aryl‐ether‐ketones) were characterized by GPC measurements coupled with viscosity determinations, and they were found to be in the range of M̄n from 10 000 to 19 000. From polymer solutions, solid and mechanically stable films were produced on a glass plate by evaporating the solvents. A perpendicular order of the phenyl ring was calculated by the MMX method.
Aldol‐group‐transfer polymerization of 2‐phenyl‐1,3,2‐dioxaborole. Preparation of graft and comb‐like polymers
Authors: Wulff Günter , Birnbrich Paul
Published: April 2003

The aldol‐group‐transfer polymerization of 2‐phenyl‐1,3,2‐dioxaborole is described. By initiation with aldehydes the molecualr weights of the polymers can be controlled through the mole ratio of initiator to monomer, ranging between 700–130000. The phenylboronic ester groups can be removed from the polymer, yielding polymers carrying a hydroxyl group at each carbon atom of the chain. It was also possible to prepare polymerizable macromonomers by initiation with 4‐vinylbenzaldehyde. Polymerization of the macromonomers by radical initiation yields comb‐like arrangements. Similar polymers can be obtained by grafting phenyl‐1,3,2‐dioxaborole onto a polymer containing benzaldehyde moieties in the side chains.
Synthesis and properties of aromatic polyamides of 2,3‐bis(4‐aminophenoxy)naphthalene
Authors: Yang Chin‐Ping , Chen Wen‐Tung
Published: April 2003

A new polymer‐forming diamine, 2,3‐bis(4‐aminophenoxy)naphthalene, was synthesized in two steps from the condensation of 2,3‐naphthalenediol and p‐chloronitrobenzene, giving 2,3‐bis(4‐nitrophenoxy)naphthalene, followed by the reduction with hydrazine/Pd‐C system. A series of novel aromatic polyamides (aramids) were synthesized by direct polycondensation of the diamine with various aromatic dicarboxylic acids in N‐methyl‐2‐pyrrolidone (NMP) using triphenyl phosphite and pyridine as condensing agents. These aramids have inherent viscosities of 0,70–1,48 dL/g and were obtained in quantitative yield. The polymers are generally soluble in a wide range of solvents, such as N,N‐dimethylacetamide, NMP, dimethyl sulfoxide, pyridine, and tetrahydrofuran, and afford transparent, flexible, and tough films upon casting from their solutions. The glass transition temperatures of these aramids are in the range of 242−267°C, and the 10% weight loss temperatures are above 503°C in nitrogen and above 496°C in air.
Investigation of poly(arylenevinylene)s, 40. Electrochemical studies on poly(p‐phenylenevinylene)s
Authors: Helbig Manfred , Hörhold Hans‐Heinrich
Published: April 2003

Differential pulse polarography (DPP) and cyclovoltammetry (CV) were conducted to study the redox behaviour of poly(p‐phenylenevinylene) (PPV; E = 0,76 V; E = −1,74 V) as well as of three insoluble PPV‐derivatives and four soluble aryl‐substituted PPV's. Oxidation studies of DP‐PPV, DMOP‐PPV and DPOP‐PPV in comparison with two series of the oligomeric model compounds 1a–e and 2a–d lead to the conclusion that for DMOP‐PPV (E = 0,98, 1,24,1,31 V) and DPOP‐PPV (E = 1,10, 1,29, 1,44 V) three distinct oxidation stages exist, which are reversibly occupied and represent 1/2, 1 and 2 positive charges per repeating unit. In DP‐PPV two oxidation stages representing 1/2 and 1 positive charges were found to be reversibly occupied (E = 1,17, 1,69 V), whereas at higher potentials irreversible dehydrocyclization occurred.
Synthesis of poly(bisphenol‐a carbonate)‐graft‐polystyrene via the macromonomer technique
Authors: Rohrbach Peter , Heitz Thomas , Keul Helmut , Höcker Hartwig , Buning Gerhard H. Werumeus
Published: April 2003

The synthesis of poly(bisphenol‐A carbonate)‐graft‐polystyrene with grafts of definite, predictable, nearly identical length was achieved using the macromonomer technique, i.e., copolycondensation of polystyrene macromonomers, carrying aromatic hydroxyl function, with bisphenol‐A and triphosgene in pyridine/methylene chloride solution. The incorporation of the macromonomer into the polycarbonate backbone was examined both qualitatively and quantitatively. The copolycarbonate show — in the contrast to polystyrene/polycarbonate blends of comparable molecular weights and composition — only one glass transition temperature, which proved to be dependent on the polystyrene content, following the Fox equation. The title compounds exhibit reduced stress‐induced birefringence compared to polycarbonate.
Polylactones, 24. Polymerizations of racemic and meso‐D,L‐lactide with AlO initiators. Analyses of stereosequences
Authors: Kricheldorf Hans R. , Boettcher Caroline
Published: April 2003

Racemic D,L‐lactide and meso‐D,L‐lactide were polymerized with four different initiators: Al(isopropoxide)3, AIEt3/neopentyl alcohol (1 : 1, mole ratio), AIEt3/(+)‐menthol (1 : 1, mole ratio) and methylaumoxane. Most polymerizations were conducted in xylene at 60, 90 and 120°C, but at 60°C the yields were below 10%. 1H NMR end‐group analyses revealed the formation of alkyl ester end‐groups from all Al‐alkoxide initiators, in agreement with an insertion mechanism. The highest molecular weights were obtained with the methylalumoxane initiator. The stereosequences of the isolated poly(D,L‐lactide)s were analyzed by 1H and 13C NMR spectroscopy on the basis of tetrad effects. poly(D,L‐Iactide)s prepared from racemic D,L‐lactide suggest a stereospecific polymerization favoring syndiotactic growing steps. In the case of meso‐D,L‐lactide all polymerizations follow Bernoullian statistics. Transesterification is poor or absent at temperatures ≤ 120°C. However, random stereosequences may be obtained by bulk polymerizations at 180°C. DSC measurements revealed that the glass transition temperature mainly depends on the molecular weight and not on slight differences in the stereosequences.
Microstructure determination of styrene/ethyl acrylate copolymers by NMR spectroscopy and its correlation with glass transition temperature
Authors: Brar Ajaib Singh , Sunita
Published: April 2003

Styrene/ethyl acrylate (S/E) copolymers of different compositions were prepared by bulk polymerization using benzoyl peroxide as an initiator. Copolymer compositions were determined from NMR spectra and reactivity ratios r1 and r2 were calculated using a non‐linear least‐squares errors‐in‐variables method (EVM) which gives more reliable values of r1 and r2. The copolymerization parameters such as terminal, penultimate reactivity ratios, diad concentrations, conditional probabilities, number‐average sequence lengths and run numbers in the copolymers were calculated by evaluating 13C{1H} NMR spectra. The observed sequence concentrations of triads as determined from 13C{1H} NMR spectra were in good agreement with those calculated from the reactivity ratios. The coisotacticity parameter (σ) was calculated from NMR spectroscopy data using the oxymethylene resonance signal in 1H NMR spectra. The glass transition temperatures (Tg) of various copolymers were obtained from Barton's equation (using diad relation) and are in agreement with those determined by means of differential scanning calorimetry.
Synthesis of nonlinear optical polymers functionalized with 4‐amino‐4′‐cyanostilbene and ‐azobenzene dyes. Second harmonic generation in corona‐poled thin films
Authors: S'Heeren Gert , Persoons André , Rondou Philippe , Wiersma John , van Beylen Marcel , Samyn Celest
Published: April 2003

The synthesis and susceptibilities χ and χ to two series of polymethacrylates functionalized with 4‐dialkylamino‐4′‐cyanoazobenzene and 4‐dialkylamino‐4′‐cyanostilbene dyes are reported. The monomeric dyes were homo‐ and copolymerized with methyl methacrylate in various ratios, to produce polymers useful for nonlinear optical (NLO) applications. The second‐order nonlinear optical properties of corona‐poled aligned polymers were evaluated by second harmonic generation measurements. The χ results for the azo‐dye polymers are in the range of 25–324 · 10−9 esu, and for the stilbene‐dye polymers in the range of 42–57 · 10−9 esu, depending on the functionalisation degree of the copolymers. The poled films do not show a significant decay in the second harmonic signal after four months.
13C cross polarization/magic‐angle spinning NMR and infrared spectroscopic study of poly(ε‐caprolactam) and of poly(ε‐caprolactam)/polystyrene blends
Authors: Schmidt Pavel , Dybal Jiří , Straka Jaroslav , Schneider Bohdan
Published: April 2003

Infrared and 13C cross polarization/magic‐angle spinning nuclear magnetic resonance (13C CP/MAS NMR) spectra and T relaxation times of differently treated poly(ε‐caprolactam)1

Systematic IUPAC name: poly[imino(1‐oxohexamethylene)].

(PCL) and of poly(ε‐caprolactam)/polystyrene blends were measured and the fractions of the α‐ and α‐crystalline and mesomorphous PCL forms were determined. The amounts of the α‐form obtained from the infrared and 13C CP/MAS NMR spectra are in agreement. In the blends, the fraction of the PCL α‐crystalline form is higher as compared with extruded pure PCL. The existence of a single T parameter for PCL in each of the samples indicates small dimensions of the crystalline regions; the obtained T values correspond to the PCL phase composition.
Anionic polymerization of ε‐caprolactam, 63. Catalysis by potassium‐graphite intercalate
Authors: Puffr Rudolf , Vladimirov Nikolay
Published: April 2003

The overall rate constants of the isothermal bulk polymerization of ε‐caprolactam were determined for the non‐activated polymerization with a heterogeneous catalyst (KC24) and a homogeneous catalyst (potassium ε‐caprolactamate), and also for the corresponding polymerizations activated with N‐benzoyl‐ε‐caprolactam. In comparison to the homogeneous catalysis, the non‐activated polymerizations with KC24 are slower, proceed with an induction period and give polyamide with a low molecular weight that does not diminish when the polymerization approaches equilibrium.
Unsteady diffusion kinetics of Ziegler‐Natta heterogeneous catalyst polymerization, 4. Prediction of experimental results of propylene/ethylene/1‐hexadecene terpolymerization
Authors: Wang Jian‐Guo , Chen Hai , Huang Bao‐Tong
Published: April 2003

The prediction, based on unsteady diffusion kinetics, of the enhancement of reactivity and incorporation of 1‐hexadecene in its copolymerization with propylene on adding a small amount of ethylene (increase from 5,2 mol‐% to 10,8 mol‐% when 2% of ethylene was added, and to 16, 1 mol‐% when 5% was added) was verified in the terpolymerization of propylene/ 1‐hexadecene/ ethylene on a commercial Solvay‐type δ‐TiCl3 catalyst. The catalyst efficiency was thus also increased. These augmentations originate from the increase in diffusion coefficient of 1‐hexadecene at the catalyst surface when the PP crystallinity decreases on introduction of ethylene. Calculation based on unsteady diffusion kinetics showed that the order of diffusion coefficients ethylene > propylene > 1‐hexadecene is reversed as the monomer concentration increases when the monomers are not at their equilibrium concentration. Sequence distribution as determined by means of 13C NMR revealed a tendency of blocky structure rather than a Bernoullian one. The terpolymer compositions obtained by means of an IR method developed in this work conform rather well with the NMR results. Results in this work not only support the unsteady diffusion kinetics but also provide a new route to prepare olefinic copolymer rubbers with heterogeneous titanium catalysts.
Preparation of polyvinylamine from polyacrylamide: a reinvestigation of the hofmann reaction
Authors: Achari Ahmida El , Coqueret Xavier , Lablache‐Combier Alain , Loucheux Claude
Published: April 2003

The Hofmann modification of polyacrylamide to yield vinylamine homo‐ or copolymers was reinvestigated in order to determine the real scope of a procedure of great potential interest in polymer chemistry. The conditions of the treatment by sodium hypochlorite followed by concentrated sodium hydroxide at low temperature (0°C) were adjusted to avoid or to limit side‐reactions between pendant reactive groups. A broad range of initial mole ratio a of sodium hypochlorite per initial amide function (0,05 < a < 1,10) was explored. The reported procedure allows to prepare in excellent yield water‐soluble polymers of controlled vinylamine content. The presence of carboxylic acid function (2 – 10 mol‐%) on the main chain, observed with low values of a, or of urea functions (1 – 5 mol‐%) observed with the highest values of a, was evidenced on the basis of analytic and spectroscopic measurements. Simple mechanistic consideration allow to propose rational schemes accounting for the side‐reactions leading to the detected minor functionalities.
Spontaneous polymerization of amphiphilic vinyl monomers, 4. Spontaneous polymerization of methacrylic derivatives of quaternary ammonium bromides with a long alkyl chain
Authors: Yasuda Yutaka , Rindo Katsuhiko , Tsushima Rikio , Aoki Shuzo
Published: April 2003

Amphiphilic surface active vinyl monomers (alkyl‐2‐methacryloyloxyethyldimethylammonium bromides) with a long alkyl chain (C8/, C12, C14, C16, and C18) were investigated with respect to their polymerization behavior in the absence of an initiator. These monomers polymerized spontaneously in water, through a free‐radical mechanism, except for the ‘C8 monomer’. In the polymerization of the ‘C16 monomer’, the polymer yield depended on polymerization temperature, and the intrinsic viscosity of the resulting polymer varied with the initial concentration of the monomer just like in ordinary polymerization. The ‘C18 monomer’, having low reactivity, became highly polymerizable upon mixing with a quaternary surfactant (dodecyl‐2‐isobutyryl‐oxyethyldimethylammonium bromide) in a particular mole ratio, owing to a change in the monomer aggregation state. In benzene, all of the quaternary methacrylates polymerized spontaneously, too. It is obvious that formation of monomer aggregates, micelles or reverse micelles is essential for the spontaneous polymerization. The spontaneous polymerization of other quaternary monomers, having a hexadecyl group and a polymerzable acryloyl, acrylamido, or methacrylamido moiety, did also occur, yet with lower rate than in case of the methacrylate.
Poly(ether‐ketone)s with indan structure elements
Authors: Maier Gerhard , Yang Dazhong , Nuyken Oskar
Published: April 2003

1,1,3‐Trimethyl‐3‐[4‐(4‐fluorobenzoyl)phenyl]‐6‐(4‐fluorobenzoyl)indan (5a) and the isomer 5b were synthesized by Friedel‐Crafts acylation of 1,1,3‐trimethyl‐3‐phenylindan with 4‐fluorobenzoyl chloride. This reaction yields a mixture of two isomer. The pure isomer as well as the isomer mixture were employed in the synthesis of poly(ether‐ketone)s via nucleophilic displacement of activated aromatic halogens by different diphenols. The influence of the indan structure element on the polymer properties such as glass transition temperature, crystallinity, solubility, and thermal stability was investigated.
Macrocyclic peptides, 8. Enantiomeric differentiations of various (R)‐ and (S)‐ ammonium and (R)‐ and (S)‐α‐amino acid ester salts by macrocyclic pseudopeptides
Authors: Miyake Hiroyuki , Kojima Yoshitane , Yamashita Tetsushi , Ohsuka Akio
Published: April 2003

The interactions of the hydrobromides of (R)‐ and (S)‐alanine‐N‐methylanilides (1) with 24‐, 27‐ and 36‐membered ring pseudopeptides (H‐24, H‐27 and H‐36, respectively) derived from glycine and (2S,3′ S)‐4‐methyl‐2‐(2′‐oxo‐3′‐isobutyl‐1′‐piperazinyl)pentanoic acid were studied by means of 1H and 13C NMR measurements in CDCl3. It was found from these results that H‐24 and H‐27 distinguished (R)‐ and (S)‐isomers of 1, while H‐36 did not entirely. Moreover, the enantioface‐differentiating abilities of these cyclic peptides were investigated by means of 1H NMR measurements in CDCI3 using (R)‐ and (S)‐1‐phenylethylammonium and (R)‐ and (S)‐p‐methoxy‐1‐phenylethylammonium bromides as the substrates, showing that the enantio‐selectivity of H‐36 is superior to those of H‐24 and H‐27. Also, the chiral recognition ability of H‐24 for the hydrochlorides of (R)‐ and (S)‐alanine (Ala), ‐leucine (Leu), ‐methionine (Met), ‐phenylalanine (Phe), ‐proline (Pro) and ‐valine (Val) methyl esters were examined by 1H and 13C NMR measurements in CDCl3. Among these hydrochlorides, HCl · PheOCH3 was distinguished more effectively with H‐24.
Synthesis and characterization of isomeric biphenyl‐containing poly(aryl ether bisketone)s, 3. Polymers derived from 3,4′‐bis(4‐fluorobenzoyl)biphenyl and bisphenols
Authors: Mani Rajrathnam S. , Weeks Barry R. , Mohanty Dillip K.
Published: April 2003

A series of high‐molecular‐weight amorphous and semicrystalline poly(aryl ether bisketone)s were prepared from bisphenols and 3,4′‐bis(4‐fluorobenzoyl)biphenyl via nucleophilic aromatic substitution reactions. Model compound studies were carried out with several substituted monohydric phenols, 3,4′‐bis(4‐fluorobenzoyl)biphenyl and 3,4′‐bis(4‐Chlorobenzoyl)biphenyl. The dihalo‐substituted aromatic ketones were synthesized by the reaction of 3,4′‐biphenyldicarboxylic acid with thionyl chloride, followed by Friedel‐Crafts acylation with the appropriate aryl halide. The required dicarboxylic acid was prepared starting from 4‐bromotoluene and 3‐methylcyclohexanone. Potassium carbonate mediated reaction of the monomers in dimethylacetamide or diphenyl sulfone gave high‐molecular‐weight polymers in excellent yield. The glass transition temperatures of the polymers are in the 170 to 190°C range. In addition, the polymers exhibit excellent thermal stability, as evidenced by both dynamic and isothermal thermogravimetric analysis, and afford tough films by compression molding.
Characterization of non‐homogeneous polymers with size‐exclusion chromatography by implementing an on‐line viscometer
Authors: Sanayei Ramin A. , Suddaby Kevin G. , Rudin Alfred
Published: April 2003

The viscosity distribution of a polymer sample can be obtained by using an on‐line viscometer as a detector in size‐exclusion chromatography. This newly defined viscosity distribution is closely related to the molecular weight distribution and expresses weight fraction times intrinsic viscosity of species i as a function of the corresponding molecular weight times intrinsic viscosity (wi[ηi] vs. Mi[ηi]). The intrinsic viscosity ([η]) and number‐average molecular weight (M̄n) can be obtained directly from a viscosity distribution. If the Mark‐Houwink exponent a is known (or approximately known) for non‐homogeneous polymer the M̄w/M̄n can be estimated from the viscosity distribution when the molecular weight distribution is approximated with a known distribution function. These estimates are independent of any other detector and are valid even for non‐homogeneous polymer samples. The relation between the moments of the viscosity distribution and the M̄w/M̄n is presented for two widely used distribution functions, the Log‐Normal and the Generalized Exponential Distributions. Polymer characterization based on the viscosity distribution is shown to be a robust technique. It is particularly attractive in characterizing non‐homogeneous polymers since it is solely obtained from on‐line viscometer.
Copolymerizations of sodium 10‐undecenoate with styrene and sodium acrylate
Authors: Arai Kenichiro
Published: April 2003

Copolymerizations of sodium 10‐undecenoate (1) with styrene and sodium acrylate (2) were examined under irradiation with UV light. In the polymerization of 1 in the presence of styrene, solubilized in the aqueous solution of 1, 1 and styrene were found to polymerize independently of each other, and a copolymer was virtually not obtained. In the copolymerization of 1 with 2, at concentrations of 1 higher than its pre‐critical micelle concentration (0,04 mol · L−1, pre‐CMC), two kinds of copolymer were obtained, one consisting predominantly of 2 units, and another consisting of comparable amounts of both monomeric units. However, at concentrations of 1 lower than its pre‐CMC, only one kind of copolymer was obtained, where the composition of the copolymer was a function of the monomer feed ratio. Reactivity ratios of the monomers were estimated in the absence of micelles of 1 (conc. < 0,04 mol · L−1) to be r1 = 0,28 ± 0,09 and r2 = 3,0 ± 1,2, which is indicative of an ideal copolymerization system. The number‐average degrees of polymerization (DPn) of the copolymer did not exceed 7, a value much lower than that of poly(1) obtained in the homopolymerization of 1.
Modeling of molar mass distribution of poly(D‐(–)‐3‐hydroxybutyrate) during bacterial synthesis
Authors: Bradel Roman , Reichert Karl‐Heinz
Published: April 2003

The development of molar mass distribution of poly(D‐(–)‐3‐hydroxybutyrate) (PHB) was studied during the intracellular synthesis in Alcaligenes eutrophus H16 bacteria with fructose as substrate and ammonium sulfate as nitrogen source. The flask culture fermentation experiments were carried out with a high cell density preculture under polymer synthesis conditions at different temperatures, pH values and substrate concentrations. These parameters were kept constant throughout the fermentation process. Polymer samples were isolated from cells by extraction with chloroform. The molar mass distribution of PHB was determined by gel‐permeation chromatography in chloroform. A simple kinetic model based on Michaelis‐Menten kinetics is postulated for synthesis of PHB. With this model the molar mass distributions of PHB were calculated and fitted to the experiment by variation of the kinetic constants.
Cationic ring‐opening polymerization behavior of 2‐ethenyl‐4‐methylene‐1,3‐dioxolane
Authors: Park Jaekyeung , Yokozawa Tsutomu , Endo Takeshi
Published: April 2003

The cationic ring‐opening polymerization of 2‐ethenyl‐4‐methylene‐1,3‐dioxolane (3) was carried out. The unsaturated cyclic acetal 3 was prepared by dehydrochlorination of 4‐chloromethyl‐2‐ethenyl‐1,3‐dioxolane, which was readily obtained from acrolein and epichlorohydrin, with sodium methoxide at ambient temperature. The cationic polymerization of 3 with BF3OEt2 or CF3SO3H at −78°C afforded cross‐linked polymers, whereas the polymerization by CH3SO3H gave a soluble poly(keto‐ether) which consisted of a unit containing a carbon‐carbon double bond in the side chain (unit 4) and a unit containing a vinyl ether group in the main chain (unit 5). The reaction of 3 with ethanethiol in the presence of a protic acid was also carried out as a model reaction of the polymerization. The reaction was initiated by addition of a proton to the 4‐methylene group of 3, followed by quantitative ring‐opening isomerization to afford acyclic ketones containing the ethylthio group. On the basis of the model reaction, some speculation on the polymerization mechanism is disclosed.
Whiskers 5. Copolyesters of 4‐hydroxybenzoic acid and 2‐(4‐carboxyphenyl)‐5‐hydroxybenzoxazole
Authors: Kricheldorf Hans R. , Thomsen Sven A.
Published: April 2003

2‐(4‐Carboxyphenyl)‐5‐hydroxybenzoxazole was obtained by a multi‐step synthesis starting from commercial 2,5‐dimethoxyaniline. Its homopolyester as well as its copolyester with 4‐hydroxybenzoic acid were prepared by polycondensation of the acetyl derivatives in an inert, liquid reaction medium at temperatures of 320, 350 or 400°C. The resulting polyesters are highly crystalline (>90% crystallinity), infusible and isoluble materials. They were characterized by elemental analyses, IR spectroscopy, WAXS and DSC measurements, and electron microscopy. The WAXS powder patterns show that the benzoxazole monomer does not fit well into the crystal modification 1 of poly(4‐hydroxybenzoic acid). Whisker‐type single crystals were obtained only when the 4‐oxybenzoate units represent 90% of the copolyesters. Polycondensations of monomers having silylated carboxyl groups did not yield better results.
Highly isospecific SiO2/MgCl2bisupported catalyst for propene polymerization
Authors: Lu Honglan , Xiao Shijing
Published: April 2003

The propene polymerization with SiO2/MgCl2/TiCl4/D (D = dibutyl phthalate) (SMTD) bisupported catalyst was studied, MgCl2/TiCl4/D (MTD) catalyst was used for comparison. It was found that the Mg content of the catalyst has a remarkable effect on the catalyst activity. The molecular weight distribution (MWD) of polypropene (PP) obtained was similar for both the SMTD and the MTD catalyst. In contrast, the kinetic curves of propene polymerization are largely different in both cases. With the SMTD catalyst the polymerization rate increases with time, while for MTD mainly a decay‐type curve is obtained. The microstructure of PP obtained with SMTD is highly isotactic in comparison to the PP obtained with MTD catalyst, although the ester content in SMTD catalyst is much lower than in MTD. The morphology of the polymer particles obtained with SMTD catalyst is mainly controlled by the morphology of the SiO2used for preparation of the catalyst. Thus, some template effect occurred during polymerization with this catalytic system.