bluuebunny/crossref_metadata_2025 huggingface dataset:
Kinetic and structural studies of the copolymerization of the cleavable bismaleimide p‐maleimidobenzoic anhydride and styrene
Authors: Winter Herman , Vegte Erik v. d. , Sijben Hans , Dušek Karel
Published: April 2003

The polymerization of a bismaleimide‐styrene system was studied by using a model compound, p‐maleimidobenzoic anhydride, that can be split by simple hydrolysis. Compared to known divinyl systems, a decreased reactivity of the pendant double bonds is observed, probably as a result of cyclization and the steric excluded volume effect. The use of a solvent causes an additional shift of the gel point towards higher conversion. Hydrolysis of gelled material affords soluble p‐maleimidobenzoic acid‐alt‐styrene copolymers. Compared to a linear system, methyl p‐maleimidobenzoate and styrene, the primary chains obtained by hydrolysis show an increased polydispersity, probably due to retardation of bimolecular termination of the free radicals that are attached to the polymer network (gel effect).
Investigation of the kinetics of ethylene polymerization with supported titanium‐magnesium catalysts of various composition
Authors: Skomorokhov Vladimir B. , Zakharov Vladimir A. , Kirillov Valerii A.
Published: April 2003

A mathematical model of the polymerization process is suggested on the basis of kinetic data, obtained for the polymerization of ethylene with supported titanium‐magnesium catalysts of various compositions differing in particle size, content of electron donor modifier, oxidation state of titanium in the initial catalyst and combination with different cocatalysts. The model includes stages of the formation and deactivation of active sites and takes into account monomer diffusion into the polymer particle. The analysis of experimental data by means of the mathematical model allowed to obtain the rate constants for single stages of the polymerization process. The suggested model and the obtained set of parameters allow to make a satisfactory description of a wide spectrum of experimental data, corresponding to different shapes of kinetic curves. The kinetic parameters were found to depend on the oxidation state of titanium in the catalyst and on the nature of the cocatalyst.
Improvement of the synthesis of poly(L‐cystyl‐L‐cystine): a new biodegradable polymer
Authors: Bechaouch Soufiane , Coutin Bernard , Sekiguchi Hikaru
Published: April 2003

A new synthesis of poly(L‐cystyl‐L‐cystine) by using N,N′‐bis(trimethylsilyl)cystine dibenzyl ester is described. The polycondensation of the latter with N,N′‐bis(benzyloxycarbonyl)cystine bis(pentafluorophenyl) ester allowed us to obtain polymers having higher molar masses (28 700 instead of 14000 g/mol) and improved properties compared with earlier methods. The partial as well as complete deprotection of the polymer using a new method, generally used in peptide chemistry, is also described.
All‐aromatic homo‐and copolyesters derived from 3,4′‐disubstituted diphenyl sulfides
Authors: Carpaneto Luca , Costa Giovanna , Peluffo Cristiana , Vezzani Sonia , Valenti Barbara
Published: April 2003

The synthesis of two new isomeric asymmetrically disubstituted disulfide monomers, [4‐(3‐hydroxyphenylthio)benzoic acid and 3‐(4‐hydroxyphenylthio)benzoic acid], with potential applications as all‐aromatic polymer chain flexibilizers and flame‐retardant additives, is here reported. The preparation and characterization of their homo‐ and copolymers obtained with 4‐hydroxybenzoic acid, terephthalic acid and hydroquinone or its phenyl and methyl derivatives is also described. The purity of the monomers has been determined by gas chromatography, elemental analysis and NMR spectroscopy. Both monomers and polymers have been characterized by several techniques. DSC analysis and optical microscopy in polarized light have been used to determine the phase behaviour of the polymers. The remarkable differences in crystallinity and mesogenicity of the polymers derived from the two isomeric monomers are compared to the behaviour of copolymers containing the analogous oxygen‐bridged compounds.
Hydrogenated butadiene/ethene/1‐olefin terpolymers as model substances for short‐chain branched polyethylene
Authors: Gerum Werner , Höhne Günther W. H. , Wilke Wolfgang , Arnold Manfred , Wegner Tino
Published: April 2003

Poly[(butadiene‐alt‐ethene)‐co‐(butadiene‐alt‐1‐olefin)] terpolymers were synthesized by Ziegler‐Natta polymerization using VO(O‐neopentyl)2Cl/Al(i‐Bu)3 catalyst system in toluene. Variation of the 1‐olefin/ethene ratio in the monomer feed produces terpolymers with mixed units of butadiene‐alt‐ethene and butadiene‐alt‐1‐olefin. After hydrogenation one obtains model substances for LLDPE with a special distribution of methylene sequences between branching points. Differential scanning calorimetry (DSC) was used to determine the degree of crystallinity and the melting behavior. From the melting temperature region, the thickness distribution of the crystal lamellac, and thus the average number of C‐atoms between the alkyl branches, can be determined. From detailed X‐ray diffractometry, the mean crystallite size, the lattice distortions and the degree of crystallinity was determined for those products which show distinct reflections. The crystallization behavior can only be described by a three‐phase model.
Doped non‐conjugated polymers with enhanced electrical conductivity, 2
Authors: Sinigersky Vesselin , Kossmehl Gerhard , Mladenova Lyudmila , Schopov Ivan
Published: April 2003

Our previous investigations showed that polymers built up of short aromatic blocks and methylene chains became conductive upon doping with iodine. Now we prepared similar polymers with conjugated blocks consisting of different types and numbers of rings (benzene, thiophene, 1,3,4‐oxadiazole) and methylene chains of different length. Despite being non‐conjugated these polymers can be doped with iodine, resulting in an increase in electrical conductivity by up to six orders of magnitude. The colour turns black and a new absorption maximum, characteristic of I3−, appears in the UV spectrum at 370 nm. These results confirm our previous assumption that in such a type of polymers, some ordering of the aromatic blocks takes place. This evokes enhanced interaction equivalent to an extension of the conjugation, thus allowing doping, leading to conductivity increase.
Chromatographic investigations of polyacetals in the critical range of liquid chromatography, 2. Determination of functionality and molecular weight distributions in α,ω‐bis(9‐anthrylmethylpoly(1,3,6‐trioxacyclooctane))s obtained by “active chain‐end mechanism”
Authors: Gancheva Valeria B. , Vladimirov Nikolai G. , Velichkova Rumiana S.
Published: April 2003

The fractions obtained by cationic active chain‐end polymerization of 1,3,6‐trioxacylooctane initiated with (CF3SO2)2O (I), CF3SOOCC6H4CO⊕⊖O3SCF3( II) and (C6H5)3C⊕PF (III) were investigated using high‐performance liquid chromatography (HPLC) at the “critical point” of adsorption. The propagating species were converted into 9‐anthrylmethyl groups by suitable reactions of termination of transformation. Their incorporation made the chain ends detectable in the ultraviolet spectrum. The samples were separated at conditions specified for poly(1,3,6‐trioxacyclooctane)s (polyTOCs) obtained with (CF3SO2)2O as initiator. The functionality and molecular weight distribution of polyTOCs obtained with mono‐ and bifunctional initiators and with different counterions were compared and discussed. In the reaction mixtures oligomers of undesired functionality were detected irrespective of the usage of mono‐ or even bifunctional initiators. A correct method was used to determine the completeness of the separation and to calculate the percentages of the individual fractions. The order of initiators depending on the amount of the undesired end‐functionality fractions in the products obtained has been established. Attempts were made to elucidate the reactions complicating the cationic chain‐end polymerization of cyclic acetals and leading to a mixture of cyclic, dead, monofunctional and bifunctional oligomers and polymers. The results were summarized and compared with functionality and molecular weight distributions of oligo(1,3,6‐trioxacyclooctane)s obtained by “activated monomer mechanism” which have been discussed in the first paper of this series.
Single site polymerization of ethylene and 1‐olefins initiated by rare earth metal complexes
Authors: Ihara Eiji , Nodono Mitsufumi , Yasuda Hajime , Kanehisa Nobuko , Kai Yasushi
Published: April 2003

Ethylene polymerization was explored by using the racemic SiMe2(2‐SiMe3‐4‐tBuC5H2)2Sm(THF)2 complex (1), meso type Me2Si(Me2SiOSiMe2)(3‐tBuC5H2)2Sm‐(THF)2 complex (2), and C1‐symmetric SiMe2[2,4‐(SiMe3)2C5H2][3,4‐(SiMe3)2C5H2]‐Sm(THF)2 complex (3) in the absence of methylaluminoxane. As a result, the meso isomer exhibits highest initiating activity, but the number‐average molecular weight is relatively low (Mn = 50000). In contrast to these complexes, the C1‐symmetric complex provides the highest molecular weight of polyethylene, Mn > 1000000, with relatively narrow molecular weight distribution (Mw/Mn = 1.60). Only the racemic complex exhibits good activity for the polymerization of propylene, 1‐pentene and 1‐hexene.
Synthesis, characterization and photoreaction of side‐chain liquid‐crystalline polymers comprising cinnamoyl biphenyl mesogen
Authors: Kawatsuki Nobuhiro , Sakashita Sin‐ichi , Takatani Ken , Yamamoto Tohei , Sangen Osamu
Published: April 2003

Liquid‐crystalline (meth)acrylate monomers and polymers having mesogenic groups based on 4‐alkyloxy‐4′‐cinnamoylbiphenyl (m = 2, 6) were synthesized. The methacrylate monomers 4c, d were polymerized by free radical polymerization. Under the same conditions, the acrylate monomers 4a, b gave unidentified polymers in very low yield. To synthesize the acrylate polymer, the acrylate monomer having 4‐alkyloxy‐4′‐hydroxybiphenyl (m = 2, 6) was polymerized followed by the esterification of the hydroxy group using cinnamoyl chloride. All synthesized polymers having mesogenic moieties showed liquid‐crystalline phases in the high temperature range between 140°C and 245°C. The difference of aggregation of the cinnamoyl biphenyl mesogen among the polymers was studied by UV‐VIS spectroscopy at various temperatures. The photoreaction was performed in both solution and thin film. The [2+2] cycloaddition reaction preferentially occurred in the thin film although both [2+2] cycloaddition and photo‐Fries reactions could occur in the solution.
Micronecking in thin films of isotactic polypropylene
Authors: Plummer Christopher John George , Kausch Hans‐Henning
Published: April 2003

Thin melt crystallized spherulitic films of isotactic polypropylene have been deformed in uniaxial tension at different temperatures and examined by transmission electron microscopy. As the temperature was increased above approximately −80°C, a transition from high aspect ratio craze‐like features to highly voided shear deformation zones was observed, these latter initiating both at spherulite boundaries and along the spherulite diameters perpendicular to the tensile axis. In rapidly crystallized films, the draw ratio in the deformation zones was estimated to be close to the natural draw ratio of the melt entanglement network, and was independent of test temperature in the range investigated. However, for crystallization temperatures above approximately 125°C, the mean draw ratio within the deformation zones was found to increase with crystallization temperature. It was also observed that, although the draw ratios in deformation zones in ß spherulites were similar to those in α spherulites in films containing both modifications, the former showed more homogeneous textures. This suggests that the particularly pronounced textures associated with α spherulites in polypropylene thin films are linked to their crosshatched lath‐like lamellar morphology.
A 40‐membered cyclic arylene ether sulfone from bisphenol‐A: improved synthesis and properties
Authors: Xie Donghang , Gibson Harry W.
Published: April 2003

By the use of pseudo‐high dilution techniques a 40‐membered cyclic arylene sulfone 4, n = 1 was produced in 67% yield by “1 + 1 cyclization” of 4,4′‐dichlorodiphenyl sulfone with 4,4′‐bis(p‐hydroxyphenylisopropylidene phenoxy)diphenyl sulfone, derived in turn from bisphenol‐A and the dihalosulfone. This is a significant improvement over our previously reported yield of 11%. However, the use of cesium carbonate did not result in a yield improvement, i.e., no “cesium effect” was observed. The purity of macrocycle 4, n = 1 was established by high‐performance liquid chromatography (HPLC), NMR spectroscopy and fast atom bombardment mass spectrosccopy (FAB MS). Macrocycle 4, n = 1 has poor solubility due to its crystallinity (Tm = ca. 500°C), but does have high thermal stability (5% weight loss at 507°C in air). HPLC and FAB MS demonstrated that other homologous macrocyclic products resulted from “2 + 2 cyclization” (4, n = 3), “3 + 3 cyclization” (4, n = 5) and backbiting ether exchange reactions (4, n = 2). The high melting point of 4, n = 1 precludes its use as a monomer for melt ring opening polymerization, but this study provides a methodology for the synthesis of other cyclic monomers designed to have lower melting points and be useful in melt ring opening polymerizations.
Morphological observations of single‐chain glassy polystyrene by means of tapping mode atomic force microscopy
Authors: Qian Renyuan , Shen Jingshu , Bei Nianjiong , Bai Chunli , Zhu Chuanfeng , Wang Xinwen
Published: April 2003

Tapping mode atomic force microscopy has been used to observe single‐chain polystyrene (SCPS) particles sprayed with an atomizer onto freshly cleaved mica surfaces from very dilute solutions of a polydisperse polystyrene sample in good solvents, methylene cloride and benzene, and in poor solvents, CH2Cl2/MeOH 3/1.2 v/v and CH2Cl2/MeOH 3/1.3 v/v. The SCPS particles possess a definite morphology irrespective of the molecular weight but depending on the solvent. The morphology was found to change with time during drying after spraying and to be very sensitive to solvent environment and external forces exerted by the tip of the scanning probe. The particles became oriented due to probe‐tip‐particle interaction during probe scanning. Only qualitative comparison were made for the sizes of the observed images owing to the polydispersity and irregular shape of the particles and uncertainties about the tip convolution effects on the lateral dimensions. Only in the case of spraying the solution in poor solvents particles close to the shape of spheres were observed. In other cases the heights of the particles sprayed were an order of magnitude smaller than the lateral dimensions. AFM imaging has been applied to observe changes in morphology of SCPS particles sprayed from solutions after freeze thaw cycling. The results do not support the idea of cryogenic degradation of PS but the morphology of PS in solution changed to a smaller coil size during cryogenic freezing which persisted after being brought back to room temperature. When the freeze thaw cycled solution was heated to 100°C and then cooled to room temperature the coil size increased with a resulting morphology similar to the morphology observed before freeze thaw cycling.
Effect of bimodality on tear properties of silicone networks
Authors: Shah Gul Bali , Winter Ray Wlliam
Published: April 2003

The effect of blending a short and a long chain prepolymer, i.e. the effect of biomodality, and that of concentration of the crosslinker on mechanical properties has been investigated. The content of short chain prepolymer was varied from 0 to 80 wt.‐%. Different concentrations of crosslinker, 3.9, 9.1 and 12.3 wt.‐%, were used for the bimodal mixtures. It was found that the enhancement of tear properties was dependent upon both the bimodality and the amount of crosslinker used for curing. It has been shown that the enhancement cannot be explained in terms of the existing theoretical equations for tear properties.
On the chain stiffness of poly(lactide)s
Authors: Joziasse Cornelis A. P. , Veenstra Harm , Grijpma Dirk W. , Pennings Albert J.
Published: April 2003

Poly(lactide)s (PLAs) are well known hydrolytically degradable polymers, that are widely used for biomedical applications. However, the intrinsic brittle nature of poly(lactide)s is still poorly understood. The stiffness of a polymer chain, expressed as the characteristic ratio C∞ plays an important role in the deformation mechanism of amorphous polymers. In order to investigate the effect of tacticity, high molecular weight poly(lactide) stereo‐copolymers with D‐lactide contents in the range 0–50 mol‐% were synthesised. These polymers were used in light scattering and differential scanning calorimetry (DSC) experiments for the determination of the characteristic ratio C∞ and glass transition temperature Tg. The results of the light scattering experiments in acetonitrile indicate that the characteristic ratio C∞ for poly(lactide)s depends on the L/D‐lactide ratio and increases with the tacticity of the polymer from 9.5 for racemic PDLLA to an estimated 11.8 for isotactic PLLA. These results are consistent with the observed brittle behaviour of poly(lactide) stereo‐copolymers and agree well with predictions obtained from group contribution methods. The choice of the relevant bond length used for the calculation of the characteristic ratio from the scattering data is not as obvious as it may seem and remains a point of discussion. The tacticity of poly(lactide)s also influences the glass transition temperature, which varies from 54°C for racemic to 63°C for isotactic poly‐(lactide).
Synthesis and polymerization behavior of 2,3‐dihydro‐1,4‐dioxin‐2‐one and its 3‐methyl derivative
Authors: Wulff Günter , Jakoby Kai
Published: April 2003

The hitherto unknown 2,3‐dihydro‐1,4‐dioxin‐2‐one (7) and its 3‐methyl derivative 8 have been synthesized for the first time. The olefinic double bond is inserted into the saturated 1,4‐dioxanone precursors 3 and 6a/b by a retro‐Diels‐Alder reaction in the last step of the synthesis. The 1,4‐dioxanone systems of 3 and 6 are prepared by reacting a vicinal dialkoxide with α‐halogenated acyl halides, thus forming the ester and the ether bond in a one‐pot reaction. Monomers 7 and 8 are polymerized by cationic initiation. The resulting products undergo fragmentation to form oligomers in the presence of protic solvents, indicting that ring‐opening polymerization of the δ‐lactone apparently leads to polyester chain segments.
Synthesis and properties of aromatic polyimides derived from 2,7‐triptycenediamine
Authors: Akutsu Fumihiko , Saito Go , Miyamoto Masahiro , Kasashima Yoshio , Inoki Mari , Naruchi Kiyoshi
Published: April 2003

Novel aromatic polyimides were synthesized from 9,10‐dihydro‐9,10‐o‐benzenoanthracene‐1,5‐diamine (2,7‐triptycenediamine) and aromatic tetracarboxylic dianhydrides. The polymerization was carried out in a two‐step procedure including ring‐opening poly‐addition giving polyamic acids, followed by thermal cyclodehydration. The polyamic acids have high inherent viscosities (0.97–1.95 dL/g in 1‐methyl‐2‐pyrrolidone). The polyimides show high glass transition temperatures (392–409°C), high decomposition temperatures at 5% weight loss (516–566°C), and high weight residues (64–69% at 800°C). All polyimides are amorphous. The polyimide from the diamine with 3,3′,4,4′‐diphenylsulfonetetracarboxylic dianhydride (4,4′‐sulfonyldiphthalic anhydride) is soluble in pyridine, N,N‐dimethylacetamide, N,N‐dimethylformamide, dimethyl sulfoxide and conc. sulfuric acid at 60°C, and shows high thermal stability. The introduction of 2,7‐triptycenediyl structure into the polyimide backbone has the effect of improving the solubility and maintaining the high thermal stability.
Interpolymer association between poly(vinylpyridines) and poly(mono‐n‐alkyl itaconates). Effect of the n‐alkyl substituent
Authors: Velada José L. , Cesteros Luis C. , Katime Issa
Published: April 2003

The binary polymeric systems formed by some poly(mono‐n‐alkyl itaconates) and poly(2‐vinylpyridine) or poly(4‐vinylpyridine) are studied. Depending on the solvent, two different types of material have been synthesized. On the one hand, using methanol as common solvent, we have obtained solid polymer‐polymer complexes the composition of which is determined by the initial mixing conditions. On the other hand, pyridine avoids the complexation process, allowing to obtain a true solution of both polymers and, therefore, a solid polymer blend of known composition by solvent casting. Yields of the complexation and stoichiometries of the polymer‐polymer complexes have been analysed. In this way, a favoured composition in the range from 3:2 to 1:1 for the mole ratio (referring to repeating units) ratio poly(mono‐n‐alkyl itaconate):poly(vinylpyridine) was observed depending on the poly‐(mono‐n‐alkyl itaconate used). Differential Scanning Calorimetry and thermogravimetry have been employed to study the thermal behaviour of complexes and blends. Viscometry measurements have been performed to analyse the interactions in solution. One of the aims of this work has been to analyse the effect of the side group of the poly‐(mono‐n‐alkyl itaconate) in the mixing process as well as in the characteristics of the final products. In this way, higher complexation yields have been obtained using poly‐(mono‐n‐alkyl itoconates) with longer n‐alkyl side groups due to the additional stabilisation by solvophobic interactions. On the other hand, the poly(mono‐n‐alkyl itaconates) with longer n‐alkyl groups form polymer‐polymer complexes with a higher proportion of poly(4‐vinylpyridine), presumably due to their slower kinetics of complexation.
Télomérisation en milieu aqueux, 2. Étude cinétique de la télomérisation de l'acide acrylique avec l'acide thioglycolique
Authors: Boutevin Bernard , Rigal Gérard , El Asri Mohammed , Lakhlifi Tahar
Published: April 2003

The telomerization of acrylic acid with thioglycolic acid initiated with hydrogen peroxide in aqueous medium is presented. In order to better control this reaction, the decomposition of H2O2 was first investigated by means of differential scanning calorimetry (DSC), leading to a very high value of the dissociation rate constant (kd), and then studied by volumetry in the presence of a mercaptan. This second method gave a higher value of kd (by about 6 orders of magnitude at 50°C). From the latter value, the ratio fkP2/kTe and the transfer constant of thiogiycolic acid, Ct, were determinated and compared with those reported in the literature. The kinetical parameters, obtained from theoretical and experimental values of DPn and the conversion of the monomer are in good agreement and allow to prepare telomers of acrylic acid with controlled chain length.
Planar para‐phenylene oligomers
Authors: Grimme Julian , Scherf Ullrich
Published: April 2003

Planar, methylene‐bridged quinque‐ and septiphenyl oligomers were synthesized as soluble, hitherto unknown compounds. The series of homologous and planar ladder‐type oligophenyls (ter‐, quinque‐, septiphenyl) was characterized especially with respect to their optical properties (absorption and emission) as function of increasing chain length, and compared to the corresponding ladder‐type polyphenylene. An effective conjugation length of about 12 benzene rings was determined within this series of planar oligo‐ and polyphenylenes.
Uncrosslinked epoxide‐amine addition polymers, 44. Linear arylamine/2,2‐bis[4‐(2,3‐epoxypropoxy)phenyl]‐propane addition polymers — synthesis and properties
Authors: Klee Joachim E. , Grützner Rolf‐Egbert , Hörhold Hans‐Heinrich
Published: April 2003

The addition polymerization of aromatic disecondary diamines and 2,2‐bis[4‐(2,3‐epoxypropoxy)phenyl]propane (DGEBA) leads to linear high molecular weight epoxide‐amine addition polymers with number‐average molecular weights ranging from 10 000 to 20 000 g/mol. Depending on the amine structure, their glass transition temperatures were estimated between 80 and 140°C. The fractionation of the high molecular weight addition polymers allows the separation of cyclic oligomers and the separation of polymers with narrow molecular weight distribution (M̄w/M̄n = 2.4–2.8). In dilute solution, predominantly cyclic oligomers were formed. Hence, they were prepared in such solutions and isolated by means of column chromatography. Their cyclic structure is proved by combination of M̄ values and 13C NMR spectra.
Synthesis and characterization of poly(2,5‐dipropargyloxy‐1,4‐phenylenevinylene) and its copolymers with 1,4‐phenylenevinylene
Authors: Shim Hong‐Ku , Hwang Do‐Hoon , Yoon Chong‐Bok
Published: April 2003

Poly(2,5‐dipropargyloxy‐1,4‐phenylenevinylene) (PDPPV) and its copolymers were prepared as thin films via the organic‐soluble and water‐soluble precursor routes. Elimination and crosslinking reactions could be controlled by the temperature. Crosslinked PDPPV is stable up to 450°C. The conductivity values of undrawn and drawn FeCl3‐doped PDPPV films are 5.0 × 10−2 and 2.0 × 10−1 Sċcm−1, respectively. The third‐order nonlinear optical susceptibility, χ(3), for the PDPPV film was investigated by degenerate four‐wave mixing (DFWM) technique at 602 nm wavelength, and found to be 2.3 × 10−10 esu.
Morphological study of bacterial poly(3‐hydroxybutyrate‐co‐3‐hydroxypropionate)
Authors: Ichikawa Masafumi , Nakamura Kazuhiro , Yoshie Naoko , Asakawa Naoki , Inoue Yoshio , Doi Yoshiharu
Published: April 2003

The solid‐state structure of a bacterially synthesized copolyester, poly(3‐hydroxybutyrate‐co‐3‐hydroxypropionate), P(3HB‐co‐3HP), with the 3HP content ranging from 0 to 37 mol‐%, was analyzed by 13C solid‐state high‐resolution NMR, X‐ray diffraction, differential scanning calorimetry and optical microscopy. For the copolymers containing up to about 40 mol‐% 3HP, it was confirmed from the X‐ray diffraction measurement that the crystallographic parameters are similar to those of P(3HB) homopolymer and the degree of crystallinity decreases as the 3HP content increases. From the measurement of 13C spin‐lattice relaxtion time (T1c) using solid‐state high‐resolution 13C NMR, it was concluded that the crystalline region is composed only of 3HB units, suggesting that the cocrystallization of 3HB and 3HB units in the same crystal lattice does not occur in P(3HB‐co‐3HP). This conclusion is supported by the thermal properties and the rate of spherulite growth.
Synthesis and electroluminescent properties of quaterphenyl and sexiphenyl containing copolymers
Authors: Keegstra Menno A. , Cimrová Vera , Neher Dieter , Scherf Ullrich
Published: April 2003

Copolymers containing quaterphenyl and sexiphenyl units in which the solubility was introduced by spacer groups were prepared and investigated. Photoluminescence of the compounds appears in the blue region of the visible light. Blue light emitting electroluminescent devices based on the blends of the quaterphenyl copolymer and poly(N‐vinylcarbazole) with indium‐tin oxide(ITO) and aluminium as hole‐ and electron‐injecting electrodes, respectively, were fabricated. Further, the quaterphenyl copolymer was found to be nematic between 236 and 244°C.
Synthesis and polymerization of bis(hexamethylene carbonate) and bis(2,2,3,3,4,4,5,5‐octafluorohexamethylene carbonate)
Authors: Weilandt Karl D. , Keul Helmut , Höcker Hartwig
Published: April 2003

Bis(hexamethylene carbonate) (HC) and bis(2,2,3,3,4,4,5,5‐octafluorohexamethylene carbonate) (FHC) were synthesized starting from the corresponding diols and diphenyl carbonate in a two‐step reaction: (i) first polycondensation occurs, (ii) then ring‐closing depolymerization leads to HC and FHC, respectively. The polymerization of HC is performed withsec‐butyllithium in toluene solution, and the corresponding polymer is obtained in high yield. Polymerization of FHC is perfomed either in tetrahydrofuran solution with dibutylmagnesium as initiator or in the melt with dibutyltin dimethoxide as initiator. Poly(HC) is a semicrystalline polymer with a melting point of 54.0°C and a glass transition temperature of −51.3°C. Poly(FHC) was obtained either as a semicrystalline material with a melting point of 40.8°C or an amorphous material with a glass transition temperature of −39.8°C. Copolymers of HC and FHC with a diad ratio of 19:60:21 were obtained by melt polymerization with dibutyltin dimethoxide as initiator. The ringchain equilibrium established during polymerization was studied for HC in toluene solution and for FHC in the melt. The concentration of the cyclic oligomers at equilibrium was determined, and for poly(HC) the characteristic ratio was calculated to be 10.0 ± 1.0.
Novel water‐soluble block copolymers of dimethylaminoethyl methacrylate and dihydroxypropyl methacrylate
Authors: Hoogeveen Nynke G. , Stuart Martien A. Cohen , Fleer Gerard J. , Frank Willy , Arnold Manfred
Published: April 2003

In this publication we describe the synthesis and properties of a novel type of block copolymer. The anionically synthesised block copolymer consists of a neutral, watersoluble block (2,3‐dihydroxypropyl methacrylate, HMA) and a pH‐dependently charged one (2‐dimethylaminoethyl methacrylate, AMA). The adsorption on silica and its effect on the colloidal stability were evaluated. The adsorbed amount is mainly determined by the electrostatics, which leads to a maximum adsorbed amount at low AMA content. The block copolymers tend to destabilise colloidal silica, due to a charge neutralisation upon adsorption, which is not compensated by the formation of a steric layer.
Poly{arylene‐alt‐[bis(1‐methylpyrrolylene)]}s, 1. Synthesis and electrochemical polymerization of terarenes
Authors: Geißler Uwe , Hallensleben Manfred L. , Rohde Nils
Published: April 2003

Novel alternating conjugated copolymers were prepared by electrochemical polymerization of defined bis(1‐methylpyrrol‐2‐yl)arenes. The comonomers were synthesized by the nickel‐catalyzed coupling reaction (Kumada synthesis) of 1‐methylpyrrol‐2‐yl anion with various dibromoarenes. The monomers were characterized via common techniques, such as ultraviolet/visible (UV/Vis), proton nuclear magnetic resonance (1H NMR), 13C NMR, infrared (IR) and mass spectroscopy (MS). All monomers show irreversible electrochemical behavior and could therefore be polymerized to conducting polymers. The resulting copolymers reveal a conductivity in the range of 10‐2 S/cm to less than 10‐6 S/cm. The conductivity mainly depends on steric hindrance between the aromatic rings. A high decoupling of the conjugated systems could be observed in case of the anthracene/bis(1‐methylpyrrole) copolymer, which is due to the highest torsion angle between the rings of the series. Additionally, in the case of the furan derivative a soluble copolymer is formed under certain conditions in the reduced state.
Highly stereoelective polymerization of rac‐(D,L)‐lactide with a chiral schiff's base/aluminium alkoxide initiator
Authors: Spassky Nicolas , Wisniewski Muriel , Pluta Christian , Le Borgne Alain
Published: April 2003

A chiral Schiff's base/aluminium alkoxide initiator bearing a ligand derived from R‐(+)‐1,1′‐binaphthyl‐2,2′‐diamine was synthesized and used for the stereoelective polymerization of rac‐(D,L)‐lactide. Rather high stereoelectivity is observed: a polymer with 88% enantiomeric enrichment in D units is obtained at 19% conversion. At high conversions a stereocomplex between D‐ and L‐enriched stereocopolymers is formed. The polymerization reaction shows living type features, and narrow molecular weight distributions (M̄w/M̄n = 1,05–1,30) are obtained up to very high conversions. This indicates that transesterification reactions do not occur significantly with this sterically hindered initiator.
Reactivity ratios in group transfer copolymerization of methyl methacrylate/ethyl methacrylate and methacrylonitrile/methyl methacrylate systems obtained by semi‐integral and integral methods
Authors: Çatalgil‐Giz Huceste
Published: April 2003

The monomer reactivity ratios for the methyl methacrylate/ethyl methacrylate (MMA/EMA) and methacrylonitrile/methyl methacrylate (MAN/MMA) systems are calculated by linearized semi‐integral and nonlinear fully integral methods. For the MMA/EMA system, rMMA values obtained by various methods are between 1.24 and 1.25 and rEMA values between 0.30 and 0.34. For MAN/MMA system, rMAN values are between 3.2 and 3.8 and for rMMA an upper bound can be determined, i.e., rMMA<0.05. The results show that previous values obtained by the linearized method (the initial Kelen‐Tüdős method) overestimate the reactivity of the less active monomer.
Synthesis and characterization of some novel polyamides containing diacetylene side groups
Authors: Fomina Lioudmila , Vega Adriana , Fomine Sergei , Gaviño Ruben , Ogawa Takeshi
Published: April 2003

A series of novel polyamides containing diacetylene groups as side chains were prepared by Cadiot‐Chodkiewcz‐coupling of polymer precursors bearing 2‐propynyloxy side groups with 4‐bromo‐3‐butyn‐1‐ol. The conversion of the acetylenic groups was in the range of 87.5–96.5% depending on the chemical structure of the polymer backbone. The polymers are highly amorphous and undergo random cross‐linking on heating. Thermally treated polymer films show third‐order nonlinear optical susceptibility χ(3) of the order of 10−10 esu (= 10−18m5/V2).
Chromatographical investigation and mass spectrometry of cyclic polyimides by matrix‐assisted laser desorption
Authors: Kottner Nils , Bublitz Renate , Klemm Elisabeth
Published: April 2003

The Diels‐Alder addition polymerization of bispyrone 1 with 2 mol bismaleimide 2 was shown to lead to cyclic polyimides 3 (64%, M̄n = 15 000 g/mol) and to cyclic oligomers (36%) applying by gel‐permeation chromatography analysis (GPC) and by means of matrix‐assisted laser desorption/ionisation technique (MALDI).
Free radical “grafting from” hyperbranched polyesters based on polymeric azo initiators
Authors: Brenner Axel R. , Voit Brigitte I.
Published: April 2003

Aromatic and aliphatic hyperbranched polyesters were prepared by AB2polycondensation process. The highly branched, functional structure of these polymers leads to excellent solubility in combination with low solution viscosities. Varied numbers of the functional groups of the hyperbranched structures were modified with azo functions which are able to initiate free radical polymerization. An increase in temperature in the presence of the vinyl monomers methyl methacrylate (MMA), butyl methacrylate (BMA), styrene (S), or acrylamide (AA) results in “grafting from” the hyperbranched structure. Using this method several graft products were synthesized with variations in structure, number, and size of the graft arms. Gel‐permeation chromatography (GPC) with universal calibration and viscosity measurements indicate a strong influence of the hyperbranched core on the properties of the graft product. It was possible to control the phase behavior of the graft products from two phases to homogeneous by the ratio hyperbranched polyester: grafted monomer. The film forming properties which are very poor for unmodified hyperbranched polyester were improved by grafting with linear polymer chains.
Chromatographic investigations of macromolecules in the critical range of liquid chromatography, 10. Polymer blend analysis using a viscosity detector
Authors: Pasch Harald , Rode Karsten
Published: April 2003

Binary polymer blends were separated by liquid chromatography at the critical point of adsorption. By operating at chromatographic conditions corresponding to the critical point of one blend component, the blends were separated regardless of the molar mass distributions of the components. After the separation step both components were precisely detected by an on‐line capillary viscometer. In contrast to refractive index detection, where a strong solvent peak appears in most cases, the viscosity signal is not affected by sight deviations in the mobile phase composition. Under critical conditions of adsorption of one component both blend components exhibit normal Mark‐Houwink behaviour. Therefore, the viscosity detector in conjunction with a concentration detector can be used for determining the molar mass distribution of both blend components.
Fluorescence study of the microstructure of a lyotropic liquid‐crystalline polyester substituted with sulfonato and nitro groups
Authors: Takahashi Hiromitsu , Horie Kazuyuki , Yamashita Takashi , Machida Shinjiro , Hannah David T. B. , Sherrington David C.
Published: April 2003

The fluorescence behaviour of a lyotropic liquid‐crystalline polyester substituted with sulfonato and nitro groups, poly[potassium oxy(x‐sulfonato‐1,4‐phenylene)oxy(x‐nitroterephthaloyl)] (1), was studied in various phases by changing the polymer concentration. This liquid‐crystalline polymer is soluble in several organic solvents and water. The observed fluorescence is originated from complexes between the potassium sulfonate‐substituted aromatic moiety and the nitro‐substituted aromatic moiety, and also from the dimer of the potassium sulfonate‐substituted moiety. From the results of fluorescence intensity changes with concentration, the change of phase in this lyotropic liquid‐crystalline system is suggested to occur gradually. By comparing the fluorescence behaviour in various phases with those of model compounds, the microstructure of the liquid‐crystalline state can be evaluated to some extent.
Structure and dynamics of polyelectrolyte‐surfactant complexes as revealed by solid state NMR
Authors: Antonietti Markus , Radloff Detlev , Wiesner Ulrich , Spiess Hans Wolfgang
Published: April 2003

13C‐CP/MAS‐NMR (cross‐polarization magic angle spinning), 2D‐WISE (wideline separation experiment) and 1H‐spin diffusion experiments allow to gain new insight into the structure and dynamics of solid polyelectrolyte‐surfactant complexes, a material with pronounced mesophase formation. Experiments were performed on two different complexes of polystyrene sulfonate and octadecyltrimethylammonium or tetradecyltrimethylammonium counterions, PSS‐C18 and PSS‐C14. The strong mobility differences between the ionic and alkyl phase in the lamellar complex PSS‐C18 are reflected in the NMR behavior: in the surfactant tails, a mobility gradient towards the terminal methyl group is observed. This fact as well as a high content of gauche conformations suggest a non‐interdigitating morphology of the tails at room temperature. The behavior changes during cooling below an endothermic transition centered at 255 K where a high trans content and a homogenization of the side chain dynamics is observed. We attribute this transition which is invisible in the X‐ray experiments to the formation of a highly transoid, interdigitated phase of the surfactant tails which is however not crystallized in a classical sense. 1H‐spin diffusion experiments allow to estimate the distance between mobile and immobile regions of the sample. For the complex PSS‐C14, the length scale determined by NMR is essentially that of the primary lamellar structure. For PSS‐C18, a characteristic length of the density fluctuations within the proposed undulated lamellar structure is estimated.
γ‐ray polymerization of a mesogenic methacrylate in the crystalline, liquid crystalline and liquid state: kinetics, molecular weight distribution and conversion‐dependent phase behaviour
Authors: Hohn Wilfried , Tieke Bernd
Published: April 2003

The γ‐ray polymerization of mesogenic 4‐methoxy‐4′‐(6‐methacryloyloxyhexyloxy)biphenyl (1) was investigated. 1 can be polymerized in the crystalline, in the liquid crystalline and in the molten state. The rate of polymerization increases from the crystalline to the melt phase. In order to reach 90% conversion to polymer in melt, smectic and crystalline phase, radiation doses of 10, 40 and more than 120 kGy are necessary. Melt polymerization leads to a weight‐average molecular weight of about 1 × 106 independent of the conversion to polymer. In the smectic and crystalline phase the corresponding molecular weights are about 3.8 × 105 and 4.1 × 104 at low conversion, and shifted to 2.6 × 105 and 3.9 × 104 at high conversion. The polydispersity generally increases with the γ‐ray dose and the reaction temperature. The origin of the different reaction rates and molecular weight obtained in the various phases is discussed in terms of the mobility of growing chain ends and residual monomer, which influences chain growth and termination and thus the kinetic chain length. Differential scanning calorimetry (DSC) of partially polymerized samples was used to describe the conversion‐dependent phase behaviour. Optical microscopy showed that the melt polymerization at 78.5°C proceeds under phase separation into a liquid, monomer‐rich and a solid, polymer‐rich phase. As a consequence, liquid monomer samples solidify upon γ‐irradiation once a higher conversion to polymer is reached.
Polyanhydrides, 9. Thermotropic poly(ester‐anhydride)s derived from naphthalene‐2,6‐dicarboxylic acid and biphenyl‐4,4′‐dicarboxylic acid
Authors: Kricheldorf Hans R. , Jürgens Claas
Published: April 2003

Two series of thermotropic poly(ester‐anhydride)s, LC‐PEAs, were studied. The first series was prepared by polycondensation of naphthalene‐2,6‐dicarbonyl dichloride with silylated 4‐hydroxybenzoic acid, silylated and substituted 4‐hydroxybenzoic acids or silylated 6‐hydroxy‐2‐naphthoic acid. A second analogous series of LC‐PEAs was prepared by means of biphenyl‐4,4′‐dicarbonyl dichloride. Most LC‐PEAs were semicrystalline materials with melting temperatures (Tm) in the range of 280−400°C. All LC‐PEAs formed a nematic melt above Tm, but due to the high temperatures the isotropization was affected by thermal degradation.
Synthesis and copolymerization of macromonomers based on 2‐nonyl‐ and 2‐phenyl‐2‐oxazoline
Authors: Groß Aurelia , Maier Gerhard , Nuyken Oskar
Published: April 2003

Several macromonomers were prepared by cationic ring‐opening polymerization of 2‐nonyl‐ and 2‐phenyl‐2‐oxazoline using different techniques of functionalization. Introduction of the unsaturated functional group directly via a suitable termination agent proved to be superior to the use of a phenol‐functionalized initiator and to the introduction of hydroxyl end groups via hydrolysis of the reactive cationic chain end and subsequent esterification with methacryloyl chloride. The macromonomers were characterized by spectroscopic techniques as well as GPC. One of the 4‐vinylbenzyl‐terminated macromonomers was copolymerized with MMA in different ratios. The copolymerization parameter r1 was determined to be 0.75. The resulting graft copolymers were characterized regarding number of grafts per chain, molar mass, and glass transition temperature.
Sequential reordering in condensation copolymers, 1. Melting‐ and crystallization‐induced sequential reordering in immiscible blends of poly(ethylene terephthalate) with polycarbonate or polyarylate
Authors: Fakirov Stoyko , Sarkissova Marianna , Denchev Zlatan
Published: April 2003

Unlike previous attempts, the entire cycle of melting‐ and crystallization‐induced reordering is realized in binary polymer blends in the following order: two homopolymers → block copolymer → random copolymer → block copolymer. Blends of poly(ethylene terephthalate)

Systematic IUPAC name: poly(oxyethyleneoxyterephthaloyl).

(PET) and bisphenol‐A/polycarbonate (PC) as well as PET/polyarylate (PAr) blends, are annealed directly in a differential scanning calorimeter at 280°C for various times. Scanning the samples in the heating mode reveals the complete disappearance of crystallization or melting in the blends where the ratio of PET/PC repeating units is less than 5.7/1.0. Such an amorphization is attributed to the formation of random copolymers. This statement is confirmed by NMR measurements, by the observation of one glass transition temperature Tg in the range between the initial two Tgs, and by solubility tests. Once randomized, annealing the samples at 235°C and 245°C, i. e., below melting of PET, results in a Tg shift toward the Tg of PET as well as in reappearance of melting. This effect is accompanied by an eight‐fold crystallinity increase in the equimolar blend, as compared to the randomized sample. The regenerated crystallization ability is explained by restoration of the blocks. According to previous findings, it is concluded that the considerable enthropy increase is the main driving force of randomization. The rival trend to the formation of a block copolymer by sequential reordering is driven by the crystallization of PET blocks formed. The conclusion that the observed changes in the crystallization ability and Tg‐values are based on sequential reordering is supported by experiments with samples containing increased amounts of transesterification catalyst leading to a much faster appearance of these changes. No randomization is observed with the blend composition ratio of repeating units PET/PC > 5.7/1.0. When the annealing is performed for 300 min at 165°C, where no significant exchange reactions are expected to occur, no restoration of the crystallization ability is observed.
Sequential reordering in condensation copolymers, 2. Melting‐ and crystallization‐induced sequential reordering in miscible poly(butylene terephthalate)/polyarylate blends
Authors: Denchev Zlatan , Sarkissova Marianna , Fakirov Stoyko , Yilmaz Ferdane
Published: April 2003

A 50/50 (weight ratio (38/62 mole ratio referred to repeating units)) blend of poly(butylene terephthalate) (PBT) and polyarylate (PAr), was studied by means of thermal, solubility, X‐ray and nuclear magnetic resonance techniques after annealing procedures that enable transesterification. Prolonged thermal treatment at 290°C gives rise to a copolymer that no longer reveals melting or crystallization. In accordance with previous reports, this effect is attributed to the formation of a random copolymer. Additional annealing of such samples at the relatively low temperature of 140°C results in the reappearance of melting endotherms in the differential scanning calorimetry curves. This effect is explained by crystallization‐induced sequential reordering from random to block copolymer by means of transreactions. In that way a PBT/PAr blend was shown to be another polymer system, along with poly(ethylene terephthalate) (PET)/polycarbonate (PC) and PET/PAr blends, in which the entire cycle is realized, from two homopolymers via a block‐ and random copolymer to a block copolymer. The unusually low temperature at which the crystallization‐induced sequential reordering to block polymers takes place is explained by the miscibility of PBT and PAr which enables transreactions to take place in the bulk.