bluuebunny/crossref_metadata_2025 huggingface dataset:
Synthesis of well‐defined polystyrene with multi‐functional end groups utilizing cyclotriphosphazene
Authors: Inoue Kenzo , Negayama Sadao , Itaya Tomoyuki , Sugiyama Minoru
Published: April 2003

Telechelic polystyrenes with five benzyl chloride moieties at the polymer end (PSt‐E) were prepared by coupling reaction of polystyryllithium with hexakis(4‐chloromethyl‐phenoxy)cyclotriphosphazene (4). The coupling reaction occurs almost quantitatively and unfavorable side reactions were not operative. When a mole ratio [4]/[sec‐BuLi] = 9.3 was used, polystyrenes with cyclophosphazene carrying five benzyl chloride moieties at the polymer end (PSt‐E) were obtained in more than 90% yield, which have narrow and predictable molecular weights (Mw/Mn = 1.05). A star shaped polystyrene with phosphazene core could also be prepared by using excess polystyryl anions.
Hyperbranched polycarbosilane macromonomers bearing oxazoline functionalities
Authors: Lach Christian , Müller Philipp , Frey Holger , Mülhaupt Rolf
Published: April 2003

Synthesis of hyperbranched polycarbosilanes by hydrosilylation of triallylsilane is reported. Soluble high molecular weight polymer was obtained in an uncontrolled bulk reaction. Addition of 2‐(10‐decen‐1‐yl)‐1,3‐oxazoline (i) afforded control over degree of polymerization (DP) and (ii) resulted in hyperbranched macromonomers. 17000 ≥ Mw ≥ 800 (GPC (PS)) was obtained. 29Si NMR spectroscopy allowed identification of dendritic, branched, linear, and terminal silicon branch‐points. A modified definition for the degree of branching yielded a value of 0.48 ± 0.05 (theory: 0.44).
New metallomesogenic polymers built by self‐assembly of non‐mesomorphic stilbazole dimers and CF3SO3Ag through coordination bonds
Authors: Kihara Hideyuki , Kato Takashi , Uryu Toshiyuki
Published: April 2003

Supramolecular liquid‐crystalline main‐chain polymers have been obtained by self‐assembly of non‐mesomorphic bifunctional ligands and a transition metal ion. Stibazole dimers, bis[2‐(2‐{4‐[2‐(4‐pyridyl)vinyl]phenoxy}ethoxy)ethyl] ether (1) and 1,2‐bis[2‐(2‐{4‐[2‐(4‐pyridyl)vinyl]phenoxy}ethoxy)ethoxy]benzene (2) have been synthesized and complexed with silver trifluoromethanesulfonate (CF3SO3Ag). The metallomesogenic polymeric complexes formed by coordination bonds between the pyridyl groups of the stilbazole dimers and the silver ion exhibit smectic phases.
Polyelectrolyte‐surfactant complexes containing photolabile diazosulfonate chromophores
Authors: Antonietti Markus , Kublickas Rimantas , Nuyken Oskar , Voit Brigitte
Published: April 2003

Low‐molar‐mass surfactants (S) and polyelectrolytes (PE) containing diazosulfonate chromophores which are photo‐labile and electrically charged were used for the formation of polyelectrolyte/surfactant complexes (PESC) in combination with commonly used polyelectrolytes and surfactants. The stable complexes are no longer water‐soluble and were characterized by means of nuclear magnetic resonance spectroscopy and in some cases by means of gel‐permeation chromatography measurements. Complexes with a 1 : 1 stoichiomctry with respect to charge are formed. Ultraviolet irradiation of the photo‐labile PESC resulted in the loss of the ionic interactions.
Amphiphilic derivatives of poly(acrylic acid) as stabilizer in emulsion polymerisation
Authors: Antonietti Markus , Weißenberger Markus C.
Published: April 2003

Poly(acrylic acid)s of various molecular weights and different degree of hydrophobic modification have been synthesized by a polymer analogous reaction with tetradecylamine or copolymerization with styrene. Testing these amphiphilic polymers as stabilizers for the emulsion polymerization of styrene reveals that well stabilized latices are obtained within a certain range of molecular weight and hydrophobicity. As an example, the addition of 1 wt.‐% polymer with respect to the monomer allows the synthesis of polystyrene latices with a radius of about 100 nm in the absence of ionic initiators or polar comonomers.
Reversible local melting in polymer crystals
Authors: Okazaki Iwao , Wunderlich Bernhard
Published: April 2003

The melting of poly(ethylene terephthalate) is analyzed by quasi‐isothermal, temperature‐modulated differential scanning calorimetry. The measurement is done by sinusoidally changing the temperature in the melting range (± 1.0 K). In the melting range a small portion of the sample melts reversibly. This observation is taken as a direct observation of the reversibility of melting of specific macromolecules as long as they are melting only partially and need no molecular nucleation for recrystallization.
Alternating terpolymerization of three non‐homopolymerizable monomers
Authors: Braun Dietrich , Schacht Matthias , Elsässer Hartmut , Tüdős Ferenc
Published: April 2003

The free‐radical terpolymerization of maleic anhydride (MSA), isobutyl vinyl ether (VIBE) and anethol (ANE) at 60°C is described. These three monomers do not homopolymerize under the conditions used. Binary copolymers are only obtained from MSA and one of the two investigated donor monomers, whereas the binary copolymerization of VIBE with ANE is not possible. In all terpolymers from these three non‐homopolymerizable monomers the MSA content amounts to about 50 mol‐%; VIBE is about twice as reactive as ANE. The terpolymerization can formally also be described under the assumption that two binary complexes (MSA/ANE (I) and MSA/VIBE (II)) are copolymerized. For this case the reactivity ratios rI = 0,9 and rII = 1,7 are obtained.
Liquid‐crystalline main‐chain elastomers
Authors: Bergmann Gerd H. F. , Finkelmann Heino , Percec Virgil , Zhao Mingyang
Published: April 2003

A main‐chain elastomer was synthesized for the first time by a cross‐linking hydrosilylation of a cyclosiloxane with a new main‐chain liquid crystalline semiflexible polyether. Imposing a uniaxial mechanical field to the unstretched nematic polydomain sample results in a macroscopic alignment of the director. For this process the sample has to be stretched by a factor of about 5, which considerably exceeds the effect observed for nematic side‐chain elastomers.
An effective etching technique for polycarbonate/core‐shell poly(butyl acrylate)‐poly(methyl methacrylate) blend
Authors: Lu Dan , Dong Lisong , Feng Zhiliu
Published: April 2003

Two etching techniques are used to reveal the morphology of PC/PBA‐cs‐PMMA blend. One is based on acetic acid (CH3COOH) solutions, whereas the other uses CCl4/C2H5OH (3/1 v/v). The latter approach shows to be more appropriate and successful for revealing the morphology of PC/PBA‐cs‐PMMA blend.
Polymerization of ethylene by using zirconocene catalyst anchored on silica with trisiloxane and pentamethylene spacers
Authors: Lee Dong‐ho , Yoon Keun‐byoung , Noh Seok‐kyun
Published: April 2003

New supported catalysts on the basis of cyclopentadienylindenylzirconium dichloride (CpIndZrCl2) anchored on silica with a trisiloxane spacer (ZATS) and a pentamethylene spacer (ZAPM) were prepared and used for ethylene polymerization with modified methylaluminoxane (MAO) as cocatalyst. ZATS and ZAPM produce polyethylene with lower molecular weight but show higher activity than silica‐supported CpIndZrCl2 which was prepared by reacting zirconocene directly with silica, i.e., the activity of silica‐supported CpIndZrCl2 is enhanced by introducing a spacer between silica surface and metallocene species.
Self‐assembled second order nonlinear optical multilayer azo polymer
Authors: Wang Xiaogong , Balasubramanian Srinivasan , Li Lian , Jiang Xinli , Sandman Daniel J. , Rubner Michael F. , Kumar Jayant , Tripathy Sukant K.
Published: April 2003

An epoxy based polymer with nonlinear optical azo chromophores was designed to contain anionic groups to induce water solubility and self assembly. Using this polyanion with a polycation, multilayers were prepared on a glass substrate by alternating adsorption from dilute aqueous solutions. The azo chromophores in the confined layer of the polyanion in the multilayer films self‐assemble into a noncentrosymmetric alignment and demonstrate second order optical nonlinearity (d33 = 19 pm/V).
Lipase‐catalyzed ring‐opening polymerization of lactide
Authors: Matsumura Shuichi , Mabuchi Kimihiro , Toshima Kazunobu
Published: April 2003

The six‐membered lactide was polymerized using the ring‐opening polymerization with lipase as a catalyst at a temperature between 80 and 130°C in bulk to yield the corresponding polylactide with weight‐average molecular weights of up to 126000. The most preferable conditions with respect to the molecular weight of the polylactide are the bulk polymerization using lipase PS at a temperature of 100°C. The D,L‐lactide gave higher molecular weight compared to the D,D‐ and L,L‐lactide.
Interactions of di‐ and trivalent anionic azo dyes with polycations of integral type
Authors: Dragan Stela , Cristea Mariana , Airinei Anton , Simionescu Bogdan C.
Published: April 2003

The spectral changes of Crystal Ponceau 6R and Ponceau 4R induced by the interaction with polycations having N,N‐dimethyl‐2‐hydroxypropane‐1,3‐diylammonium chloride units in the main chain were followed. The stoichiometry of the polycation‐dye complex related to the dye structure was elaborated by UV‐VIS spectrophotometry and viscosimetric measurements. Formation of a tricomponent complex between the polycation/dye complex and poly(sodium acrylate) was also revealed.
Graft copolymers of poly(ethylene glycol) (PEG) and chitosan
Authors: Saito Hiroshi , Wu Xiangdong , Harris J. Milton , Hoffman Allan S.
Published: April 2003

Graft copolymers of poly(ethylene glycol) (PEG) on a chitosan backbone (PEG‐g‐chitosan) have been synthesized and their aqueous solution properties were investigated. At pH 6.5 the graft copolymers are 100% soluble, while chitosan phase separates from solution at those conditions. These interesting graft copolymers may be especially suitable as carriers for delivery of anionic drugs, such as proteins, glycosaminoglycans, and DNA plasmids or oligonucleotides.
Lipase‐catalyzed ring‐opening polymerization of 1,3‐dioxan‐2‐one
Authors: Kobayashi Shiro , Kikuchi Hirofumi , Uyama Hiroshi
Published: April 2003

Enzymatic ring‐opening polymerization of a 6‐membered cyclic carbonate, 1,3‐dioxan‐2‐one, was investigated by using lipase as catalyst in bulk. Supported lipase derived from Candida antarctica catalyzed the polymerization to give the corresponding aliphatic polycarbonate. Unchanged monomer was recovered in the absence of the enzyme or using an inactivated enzyme, indicating that the present polymerization proceeds through enzymatic catalysis.
Effect of co‐catalyst system on α‐olefin polymerization with rac‐ and meso‐[dimethylsilylenebis(2,3,5‐trimethyl‐cyclopentadienyl)]zirconium dichloride
Authors: Naga Naofumi , Mizunuma Kooji
Published: April 2003

Propene, 1‐butene and 1‐hexene polymerization was conducted with a mixture of rac‐ and meso‐[dimethylsilylenebis((2,3,5‐tetramethyl‐cyclopentadienyl))]zirconium dichloride (Me2Si(2,3,5‐Me3Cp)2ZrCl2) (1) combined with methylaluminoxane (MAO), triethylaluminium (AlEt3)/triphenylcarbenium tetrakis(pentafluorophenyl)borate (Ph3CB(C6F5)4) (2) and triisobutylaluminium (AliBu3)/Ph3CB(C6F5)4, respectively, as co‐catalyst systems. The ratios of polymerization rates Rp(rac)/Rp(meso) were changed with the combined cocatalysts. It was found that in the case of using trialkylaluminium/2 as co‐catalyst Rp(rac)/Rp(meso) is lower than when using MAO in any kind of α‐olefin polymerization.
Liquid crystalline, highly luminescent poly(2,5‐dialkoxy‐p‐phenyleneethynylene)
Authors: Steiger Daniel , Smith Paul , Weder Christoph
Published: April 2003

A high‐molecular‐weight poly(2,5‐dialkoxy‐p‐phenyleneethynylene) derivative has been prepared by the Heck reaction of 1,4‐bis(2‐ethylhexyloxy)‐2,5‐diiodobenzene and 1,4‐diethynyl‐2,5‐dioctyloxybenzene. The highly luminescent polymer exhibits excellent solubility and can readily be processed into high‐optical‐quality films. The weight‐average molecular weight M̄w was 240000 g · mol−1, with a polydispersity index of 2.9. Thermal analysis revealed a glass transition around 90°C, and an onset of chemical crosslinking at 130°C. The high M̄w and the remarkable solubility enabled the preparation of liquid crystalline solutions of the new PPE.
End‐group dynamics of fluorescently labeled dendrimers
Authors: Wilken Ralph , Adams Jörg
Published: April 2003

The molecular dynamics of dendrimer branches were studied by observing the excimer formation of pyrenyl end‐groups. By a selective synthesis only one pyrene moiety per dendron was attached, resulting in a dendrimer with 3 fluorophors per molecule. The first 3 generations of the dendrimer were synthesized by the convergent‐growth approach. By time resolved measurements of the eximer and monomer fluorescence an increased mobility of the end‐groups was observed.
Effect of stereoregularity on the thermo‐oxidative degradation of poly(propylene)s estimated by chemiluminescence
Authors: Osawa Zenjiro , Kato Masahide , Terano Minoru
Published: April 2003

The effect of stereoregularity on the thermo‐oxidative degradation of poly(propylene)s, isotactic (IPP) and syndiotactic (SPP), was compared with that of high density polyethylene (HDPE) by means of chemiluminescence (CL). SPP is extremely stable to thermal oxidation and CL signals appeared much later than in IPP and even later than in HDPE. For example, at 160°C the maximum intensity of CL was measured after only 13 min for IPP, 60 min for HDPE and 260 min for SPP. IR spectroscopic results support the conclusions drawn from CL results.
Gel permeation chromatographic determination of activation rate constants in nitroxide‐controlled free radical polymerization, 1. Direct analysis by peak resolution
Authors: Goto Atsushi , Terauchi Tomoya , Fukuda Takeshi , Miyamoto Takeaki
Published: April 2003

The dissociation rate constant kd related to the homolytic cleavage of the CON bond formed between a polystyrene (PS) and 2,2,6,6‐tetramethylpiperidin‐1‐oxyl (TEMPO) is determined by adopting the gel permeation chromatography peak‐resolution method to the styrene polymerization with a PS‐TEMPO adduct as a probe and the radical initiator tert‐butyl hydroperoxide. The result was given by the Arrhenius equation, kd = A exp(−E/(RT)) with A = 3.0 × 1013 s−1 and E = 124 kJ · mol−1.
Alternating copolymers of tetramethylene urea with 2,2‐dimethyltrimethylene carbonate and ethylene carbonate; preparation of the corresponding polyurethanes
Authors: Schmitz Frank , Keul Helmut , Höcker Hartwig
Published: April 2003

Copolymerization of tetramethylene urea (TeU, 1) with the cyclic carbonates 2,2‐dimethyltrimethylene carbonate (DTC, 2) and ethylene carbonate (EC, 3) results in the polyurethanes 4 and 5 with an approximate number‐average molecular weight of 20 000 and a polydispersity index of two. Polyurethane 4 is an amorphous material with a glass transition temperature of 26.3°C; polyurethane 5 is a semicrystalline material with a melting temperature of 208°C. Distinct copolymerization mechanisms are proposed for the formation of polyurethane 4 and 5, respectively.
Processing‐induced chromism in thin films of polythiophene derivatives
Authors: Leclerc Mario , Lévesque Isabelle , Goldenberg Leonid , Petty M. C.
Published: April 2003

Langmuir‐Blodgett films of amphiphilic poly[3‐oligo(oxyethylene)‐4‐methylthiophene] have been obtained. The resulting thin films are poorly conjugated, with a maximum of absorption at 405 nm which remains almost constant upon heating or cooling. In contrast, cast thin films of this polymer exhibit a maximum of absorption at 550 nm and show interesting thermochromic effects. These results to indicate that the method of preparation of thin films can have a significant influence on the conformational structure of the polymer at room temperature and, consequently, on its thermochromic behaviour.
Synthesis of a new siloxane‐crown ether polyamide
Authors: Ardeleanu Rodinel , Voiculescu Nicolae , Marcu Mihai , Roman Gheorghe , Buchidau Carmen , Sacarescu Liviu , Sacarescu Gabriela
Published: April 2003

The synthesis of a siloxane‐crown ether polyamide by solution polycondensation of 4,4′‐diaminodibenzo‐18‐crown‐6 with a carboxypropyl‐terminated siloxane oligomer is presented. The polymer is characterized by IR and 1H NMR spectroscopy as well as by differential thermal analysis and differential scanning calorimetry.
Synthesis and structure of crosslinked poly[(methylsiloxane)‐co‐(oxymethylene)] copolymers
Authors: Rodríguez‐Baeza Mario , Zapata Melcy , Yoshida I. Valeria P.
Published: April 2003

A series of new crosslinked copolymers was obtained by cationic ring‐opening copolymerization of 1,3,5,7‐tetramethylcyclotetrasiloxane and 1,3,5‐trioxane. The poly[(methylsiloxane)‐co‐(oxymethylene)] copolymers are white crystals or glassy. Crosslinking reactions take place in the reaction medium. The degree of crosslinking increases with a higher concentration of the methylsiloxane units in the copolymers. The combination of solid‐state magic‐angle spinning nuclear magnetic resonance of 29Si and 13C and Fourier‐transform infrared spectroscopy provided a quantitative description of the copolymer microstructure.
Studies on microgels, 3. Synthesis using living free radical polymerization
Authors: Abrol Simmi , Kambouris Peter A. , Looney Mark G. , Solomon David H.
Published: April 2003

Microgels which are soluble crosslinked polymer networks have been prepared using the nitroxide living free radical polymerization methodology. When heated in the presence of tert‐butylstyrene and 1,4‐divinylbenzene, the alkoxyamine 1 derived from 2,2′‐azoisobutyronitrile (AIBN) afforded a high molecular weight soluble polymer which was shown by size exclusion chromatography in conjunction with an on‐line multi angle laser light scattering (MALLS) detector to have microgel properties.
Alternative molecularly imprinted polymeric membranes from a tetrapeptide residue consisting of D‐ or L‐amino acids
Authors: Yoshikawa Masakazu , Izumi Jun‐ichiro , Kitao Toshio , Sakamoto Shunji
Published: April 2003

Alternative molecularly imprinted polymeric membranes were prepared from a polystyrene resin bearing tetrapeptides consisting of D‐amino acids or L‐amino acids. The membrane prepared from a DLDE derivative (H‐Asp(OcHex)‐Leu‐Asp(OcHex)‐Glu(OBzl)CH2) consisting of D‐amino acids and imprinted by Boc‐D‐Trp recognizes the D‐isomer in preference to the corresponding L‐isomer and vice versa. The amino acid preferentially adsorbed by the membrane was selectively permeated by applying electrodialysis.
Ring‐opening polymerization of chloromethylthiirane with SO42−/TiO2/Nd3+ as initiator
Authors: Shen Zhiquan , Li Weishi , Zhang Fuyao , Zhang Yifeng , Shen Lianfang , Yuan Hanzhen
Published: April 2003

A new type of solid superacid (SO42−/TiO2/Nd3+) was used for the ring‐opening polymerization of chloromethylthiirane (CMT). TiO2 · H2O immersed in a sulfuric acid solution containing Nd3+ ions and calcined at 600°C gave the solid superacid for initiating the polymerization of CMT. The effects of polymerization temperature and amount of the initiator on the CMT polymerization were studied. Poly(CMT) obtained has higher molecular weight (M̄w = 52 000) than ever reported.
Polymerization of cyclic monomers, 4. Synthesis and radical polymerization of bi‐ and trifunctional 2‐vinylcyclopropanes
Authors: Moszner Norbert , Zeuner Frank , Rheinberger Volker
Published: April 2003

Multifunctional 2‐vinylcyclopropanes were synthesized by esterification of the 1‐methoxycarbonyl‐2‐vinylcyclopropane‐1‐carboxylic acid with ethylene glycol, 1,1,1‐trimethylolpropane or 1,4‐cyclohexanediol in the presence of 1,3‐dicyclohexylcarbodiimide (DCC). The structure of the new vinylcyclopropanes was confirmed by elemental analysis, IR, 1H NMR and 13C NMR spectroscopy. The radical polymerization of the 2‐vinylcyclopropanes in bulk with 2,2′‐azoisobutyronitrile (AIBN) results in transparent crosslinked polymers. The polymerization of the liquid monomers is accompanied by a low shrinkage in volume.
Polymerization of styrene to isotactic polymer with MAO‐Ni(acac)2. Examination of the factors that influence activity and stereospecificity
Authors: Crossetti Geraldo Lopes , Bormioli Carlotta , Ripa Alberto , Giarrusso Antonino , Porri Lido
Published: April 2003

The soluble catalyst system methylaluminoxane (MAO)‐Ni(acac), (acac: acetylacetonate) gives polystyrene consisting of an amorphous (aPS) and a crystalline isotactic (ips) fraction. Al(CH3)3, which is always present in commercial samples of MAO, decreases both polymer yield and stereospecificity. The polymer yield increases with increasing the MAO/Ni ratio but, at the same time, the iPS/aPS ratio decreases. Addition of N(C2H5)3 (mole ratio N/Ni = 1) increases the proportion of the isotactic fraction, while it decreases the polymer yield. A tentative interpretation of the stereospecificity is reported.
Polymerization of ϵ‐caprolactone using heterobimetallic lanthanocene complexes
Authors: Hultzsch Kai C. , Okuda Jun
Published: April 2003

The chiral heterobimetallic complexes Li[Ln(η5 : η1‐C5R41SiMe2NCH2CH2R2)2] (Ln = Y, Lu; C5R41 = C5Me4, C5H4, 3‐C5H3 t Bu; R2 = OMe, NMe2; Me: methyl; tBu: tert‐butyl) have been found to polymerize ϵ‐caprolactone to give a polymer of high molecular weight (M̄n < 20 000) and moderate polydispersity (M̄w/M̄n < 2.0). Failure to observe a correlation between monomer/initiator ratio and molecular weight suggests a polymerization mechanism different from a pseudo‐anionic mechanism.
A novel synthesis of semitelechelic functional poly(methacrylate)s through an alcoholate initiated polymerization. Synthesis of poly[2‐(N,N‐diethylaminoethyl) methacrylate] macromonomer
Authors: Nagasaki Yukio , Sato Yasuo , Kato Masao
Published: April 2003

Potassium alcoholate was found to initiate the anionic polymerization of 2‐(N,N‐diethylaminoethyl) methacrylate (AMA) to form poly[2‐(N,N‐diethylaminoethyl) methacrylate] (PAMA). The molecular weight of the polymers was controlled by the monomer‐initiator ratio with a narrow molecular weight distribution. Increased reactivity of the initiator by chelation of the monomer to the cation may be important for the polymerization. Using potassium (4‐vinylbenzyl) alcoholate as an initiator, PAMA having a vinylbenzyl group was prepared which is a macromonomer having pH sensitive amino groups in each monomeric unit. By radical copolymerization with styrene, the PAMA macromonomer was incorporated as a graft chain.
Swelling behavior of ampholytic gels prepared by γ‐irradiation
Authors: Wada Seiichi , Satoh Mitsuru , Komiyama Jiro
Published: April 2003

Heterogeneous ampholytic gels were prepared by two‐step γ‐irradiation of aqueous solutions of poly(vinyl alcohol)s having sulfonate and quaternary ammonium groups, respectively. A reference gel was prepared by one‐step irradiation. The heterogeneous gels turned out to swell to lesser degrees with increasing ionic strength of the immersing solution than the reference gel. However, the ion‐specific swelling and deswelling behavior, which had been found for the reference gel, was also observed for the present heterogeneous gel.
Water solubility of regioselectively 2,3‐O‐substituted carboxymethylcellulose
Authors: Liu Hai‐Qing , Zhang Li‐Na , Takaragi Akira , Miyamoto Takeaki
Published: April 2003

A series of 2,3‐O‐carboxymethylcelluloses (CMC's), which are regioselectively substituted at the C‐2 and C‐3 position, were prepared and their water solubility was examined. It was found that the lower limit for the degree of substitution (DS) value of water‐soluble 2,3‐O‐CMC is about 0.3. This value was almost the same as that of CMC prepared in a slurry of isopropyl alcohol/water with isopropyl chloroacetate and sodium hydroxide, showing that the uniform alkylation is rather important to convert cellulose into water‐soluble derivatives.
A new polyphenylene derivative bearing two stable radicals
Authors: Zhang Ruifeng , Zheng Haipeng , Shen Jiacong
Published: April 2003

Hydroxylization of poly(N,N‐dimethylaniline) (PDMA) by using H2O2 in base medium gives rise to a new polyphenylene derivative containing a high concentration of stable phenoxy radicals in the solid state. In solution, hydroxylated PDMA can have two forms of stable radicals, phenoxy radical and radical cation, and these two forms can be converted reversibly into each other by adjusting the pH value of the solution.
Novel polyelectrolyte complexes based on diazo‐resins
Authors: Cao Wei‐xiao , Ye Shu‐jian , Cao Shu‐guang , Zhao Chao
Published: April 2003

Polyelectrolyte complexes containing diazonium groups (PEC‐N2) with a high ionic crosslinking rate were prepared as a precipitate by mixing the diazo‐resin with polyanion solutions. The photochemical decomposition of the complexes from different polyanions was studied. It was shown that PEC‐N2 exhibit high photosensitive properties. Under irradiation of UV light, the complexes which can be dissolved in ternary mixtures such as H2O‐DMF‐LiCl,H2O‐DMF‐NaSCN or H2O‐DMF‐ZnCl2 (DMF: N,N‐dimethylformamide) become indissoluble since the crosslinking structure of the complexes changes from ionic to covalent.
The first approach to non‐aqueous solutions of carboxymethylcellulose
Authors: Heinze Thomas , Heinze Ute
Published: April 2003

Formic acid was found to dissolve sodium carboxymethylcellulose (Na‐CMC) with comparatively slight chain degradation. The dissolution of Na‐CMC in a wide range of degree of substitution from 0.4 to 2.0 occurs under partial formylation of the remaining OH groups of the polymer, i.e., formic acid is the first non‐aqueous, so‐called derivatizing solvent. The Na‐CMC formyl esters, which can be isolated under water‐free conditions, are even soluble in dipolar‐aprotic solvents, and they can be regenerated to Na‐CMC by treating with aqueous solutions of NaOH.
Narrow‐polydispersity polystyrene/poly[styrene‐co‐(butyl methacrylate)] block copolymers by an N‐oxyl mediated free radical polymerization process
Authors: Butz Sören , Baethge Heike , Schmidt‐Naake Gudrun
Published: April 2003

Polystyrene/poly[styrene‐co‐(butyl methacrylate)] block copolymers with controlled molecular weights and with polydispersities generally below M̄w/M̄n = 1,45 and partially as low as M̄w/M̄n = 1,19 were synthesized by a free radical bulk copolymerization using a 2,2,6,6‐tetramethylpiperidine‐N‐oxyl (TEMPO)‐capped polystyrene macroinitiator. The influence of the macroinitiator concentration on the block copolymerization was studied. The polymerization rates are independent of the macroinitiator concentration and are close to that of thermally self‐initiated styrene/butyl methacrylate copolymerizations showing the important role of self‐initiation for N‐oxyl mediated free radical polymerizations.
Bis‐macromonomers of 2‐alkyl‐2‐oxazolines–synthesis and polymerization
Authors: Christova Darinka , Velichkova Rumiana , Goethals Eric J.
Published: April 2003

Poly(2‐alkyl‐2‐oxazoline)s having an acrylate group at both chain ends were synthesized by terminating living bifunctional poly(2‐methyl‐2‐oxazoline) or poly(2‐ethyl‐2‐oxazoline) with acrylic acid. These macromonomers have been polymerized to the corresponding polyoxazoline networks. Thermal as well as UV‐initiated free radical polymerization were applied and the influence of the polymerization conditions and molecular weight of the prepolymer used on the properties of the networks were investigated. Both methods of polymerization produced high fractions of soluble material, probably due to the low concentration of the acrylate end groups.
Cationic initiation of oligomerization of vinylformamide
Authors: Spange Stefan , Madl Alexander , Eismann Ulrike , Utecht Jens
Published: April 2003

Vinylformamide (VFA) is cationically polymerized in various solvents at 273 K and reaction temperature by the following initiators: iodine, bis(4‐methoxyphenyl)‐methyl chloride/silica, triphenylmethyl chloride/silica, and trimethylsilyl triflate. In every case defined oligomers with narrow molecular weight distribution are obtained in moderate yield (20–50%). Acid hydrolysis of the obtained oligomers yields well defined oligovinylamine products. The cationic initiation mechanism of VFA is discussed in terms of the HSAB‐concept

HSAB: Hard and soft acids and bases.
Threading of cyclodextrins onto a polyester of octanedicarboxylic acid and polyethylene glycol
Authors: Weickenmeier Meik , Wenz Gerhard
Published: April 2003

A water‐soluble polyester was synthesized from dimethyl octane‐1,8‐dicarboxylate and polyethylene glycol (M̄n = 900). This polymer forms water‐soluble inclusion compounds with α‐, β‐ and hydroxypropyl‐α‐cyclodextrin as proven by surface tension measurements, 1H NMR spectroscopy and titration microcalorimetry. Mainly the octamethylene segments were covered by the cyclodextrins. This inclusion can be used to increase the solubility and the critical micelle concentration of the polyester in water.
Association thickener by host guest interaction of a β‐cyclodextrin polymer and a polymer with hydrophobic side‐groups
Authors: Weickenmeier Meik , Wenz Gerhard , Huff Jürgen
Published: April 2003

A host polymer with pending β‐cyclodextrin side‐groups and a guest polymer with pending hydrophobic 4‐tert‐butylanilide side groups were synthesized by polymeranalogous reactions starting from poly[(maleic anhydride)‐alt‐(isobutene)] (M̄w = 60000). The inclusions of both polymers with complementary monomeric guests and hosts are proven by microcalorimetry. The interaction of the host polymer and the guest polymer in aqueous solution is accompanied by a tremendous increase in viscosity.
Elastomers with multimodal distributions of network chain lengths
Authors: Mark J.E.
Published: April 2003

The goal of primary interest in these investigations was the development of a novel method for preparing elastomeric networks having unusually good ultimate properties. The technique involves end linking mixtures of very short and relatively long functionally‐terminated chains to give bimodal networks. Such (unfilled) “bimodal” elastomers show very large increases in reduced stress or modulus at high elongations because of the very limited extensibility of the short chains present in the networks. This non‐Gaussian behavior also appears in compression or biaxial extension, shear, tearing, and cyclic fatigue tests. Non‐Gaussian theories taking into account this limited extensibility give a good account of the experimental results. Bimodal distributions also facilitate strain‐induced crystallization, and thus the reinforcement it provides. Suggestions are made for seeking additional advantages from multimodal distributions that are trimodal or higher.
The relaxation spectra of polymer networks with different types of topology, ordering, heterogeneity
Authors: Gotlib Yuli Ya. , Gurtovenko Andrew A. , Torchinskii Isaak A. , Shevelev Vladimir A. , Toshchevikov Vladimir P.
Published: April 2003

Many characteristic features of the relaxation spectra of the different types of polymer networks (meshlike and tree‐like) manifesting in experimental behaviour are determined by manifold types of local and long‐range irregularities or inclusions existing even in the simplest network structures. These irregularities in the local topology, in the fluctuations of the local orientational order existing due to stretching of the chains in the bulk elastomers (even in the non‐ordered elastomers), also due to possible LC‐ordering, the distribution of chain lengths between junctions and possible existence of cross‐link agglomerations and domains at random cross‐linking and the influence of the position of the chain element relative to junctions lead to variety of relaxation spectra, frequency and time‐dependencies. The long‐range hydrodynamic effects in bulk network can also lead to drastic variation of relaxation spectra. The inclusion of elongated rigid particles in polymer gels and network leads to the appearance of new branches of relaxation spectra changing and overlapping the relaxation spectra of the primary network system.
Scale dependent diffusion in latex films studied by photoinduced grating relaxation technique
Authors: Bartsch Eckhard , Jahr Thilo , Eckert Thomas , Sillescu Hans , Veniaminov Andrei
Published: April 2003

The transition from an aqueous dispersion of polyacrylate latices into a homogeneous polymer film on drying has been studied by monitoring the diffusion of hydrophobia and hydrophilic photochromic molecular probes with the help of a holographic grating relaxation (forced Rayleigh scattering) technique. Experiments with the hydrophobic probe in wet films result in an unusual spatial scale‐dependence of the apparent diffusion coefficient that degenerates into a normal scale‐independent diffusion coefficient as the film dries. Employment of a two‐state diffusion model allows extracting the diffusion coefficients and mean displacements of the tracer in the polymer cores of the latex particles and in the hydrophilic interface meshes surrounding them. The cores were found to stay essentially intact, whereas the interfacial regions change dramatically with the residual water concentration. Its influence on diffusion disappears on drying but can be partially restored by remoistening the material. The interface can be efficiently controlled by varying the surfactant concentration. A water‐soluble tracer was found to diffuse in four different environments. In addition to the already known polymer cores and the hydrophilic interfacial regions, we found a large contribution of fast diffusion in a water rich region and a very small contribution of “ultraslow” diffusion in a state supposedly related with aggregated surfactant.
Interaction of dissolved proteins with spherical polyelectrolyte brushes
Authors: Wittemann A. , Haupt B. , Merkle R. , Ballauff M.
Published: April 2003

We consider the adsorption of bovine serum albumin (BSA) on spherical polyelectrolyte brushes (SPB). The SPB consist of a solid polystyrene core of 100nm diameter onto which linear polyelectrolyte chains (poly(acrylic acid), (PAA)) are grafted. The adsorption of BSA is studied at a pH of 6.1 at different concentrations of added salt and buffer (MES). We observe strong adsorption of BSA onto the SPB despite the effect that the particles as well as the dissolved BSA are charged negatively. The adsorption of BSA is strongest at low salt concentration and decreases drastically with increasing amounts of added salt. The adsorbed protein can be washed out again by raising the ionic strength. The various driving forces for the adsorption are discussed. It is demonstrated that the main driving force is located in the electrostatic interaction of the protein with the brush layer of the particles. All data show that the SPB present a new class of carrier particles whose interaction with proteins can be tuned in a well‐defined manner.
Novel diacetylene‐containing polymers for second order NLO applications: effect of main chains and structure property relationships
Authors: Hernández Susana , Miura Hirohiko , Beristain Miriam F. , Ogawa Takeshi , Watanabe Toshiyuki , Miyata Seizo
Published: April 2003

In order to obtain polymers having high second order nonlinear optical (NLO) response, various novel polymers that contain polar dye molecules in side chains and diacetylenic groups in the main chains were synthesized, and their second order NLO properties were studied. Some of these polymers consisting of para‐benzoate and para‐cinnamate main chains, showed extremely high NLO coefficients, d33 of 200 ‐ 350 pm/V, and the corresponding meta polymers showed much inferior NLO coefficients. The polymers having aliphatic main chains had very little NLO response probably because of their low glass transition temperatures and flexibility of main chains. The high SHG responses of these polymers are attributed to their facile orientation of both chromophores and main chains. In the case of para‐polymers, the main chain orientation of alkoxybenzoate and cinnamate along the chromophore is thought to be a reason for their high NLO coefficients.
Styrene copolymerization using diphenylzinc‐additive initiator systems: styrene/p‐substituted styrenes
Authors: Rabagliati Franco M. , Pérez Mónica A. , Cancino Rodrigo A. , Soto Marcelo A. , Rodriguez Francisco J. , Caro Carlos J.
Published: April 2003

Combined systems including diphenylzinc (Ph2Zn), a metallocene, and methylaluminoxane (MAO), have been employed to initiate the copolymerization of styrene (S) with p‐alkylsubstituted styrenes and with α‐olefins. The copolymerization processes depend largely on the comonomer, the nature of the metallocene included in the initiator system, the presence of Ph2Zn, the polymerization temperature and the solvent used. Titanocenes produced true copolymers for S/p‐substituted styrene, but not in S/α‐olefin copolymerization. On the other hand zirconocenes either did not copolymerize S/p‐substituted styrene or produced very low conversions, while they succeeded in copolymerizing S/α‐olefin, depending on the particular zirconocene employed. A low p‐methylstyrene (p‐MeS) content in the S/p‐MeS copolymer and a low p‐tertbutylstyrene (p‐ButS) content in the S/p‐ButS copolymer decreased Tm, making them easier to process material than s‐PS.
Suppression of secondary PL emission by indirect photoexcitation
Authors: Byun H.Y. , Chung I.J. , Suh Y.‐S. , Shim H.K. , Kim D.Y. , Kim C.Y.
Published: April 2003

A blend of a newly synthesized polyfluorene(PDHBF) and polyvinylcarbazole(PVK) exhibits a photoluminescence(PL) emission spectrum of PDHBF without an increase in the PL intensity on photoexcitation at 340 nm, the UV‐visible absorption maximum of PVK, despite of a substantial spectrum overlap. However, the indirect photoexcitation of the blend suppresses the secondary emission of the PL with the maximum at 520 nm. The chromophores generating the secondary emission are formed when the chromophores are photoexcited above the critical energy level of an excited state. The chromophores formed by the energy transfer have energy lower than the critical energy and fail to form the excimers. A low temperature PL study of the blend in a cryogenic chamber proves that the energy transfer in the system takes place mainly between the excimers of PVK generated by the partially eclipsed dimeric states of two carbazole units and the fluorophores of PDHBF.
Durable chiral sensor based on quartz crystal microbalance using self‐assembled monolayer of permethylated β‐cyclodextrin
Authors: Ng Siu‐Choon , Sun Tong , Chan Hardy S.O.
Published: April 2003

A novel chiral sensor based on quartz crystal microbalance (QCM) with a self‐assembled monolayer of permethylated β‐cyclodextrin as the enantioselective coating has been derived which exhibit improved enantioselectivity and excellent long‐term environmental stability when used in gas phase sensing.
Core‐shell particles: building blocks for advanced polymer materials
Authors: Pham Hung H. , Kumacheva Eugenia
Published: April 2003

Polymer particles with submicrometer dimensions show promising applications in “bottom‐to‐top approach” to fabrication of materials with periodic structure, function, and composition. A novel approach to producing such materials is proposed, which employs core‐shell particles with specific structures and compositions. We report on the synthesis of core‐shell particles using interfacial polymerization and heterocoagulation techniques. The compositions of core‐forming material and/or the shell‐forming polymers were selectively controlled to be make the cores or the shells rigid or fluid, fluorescent or non‐fluorescent, organic or inorganic. Several potential applications of nanocomposite materials obtained from these particles are demonstrated, including three‐dimensional optical data storage and optical limiting and switching.
Effects of external fields on macromolecular cholesteric phase
Authors: Wang Linge , Huang Yong
Published: April 2003

Effects of external fields such as magnetic field and boundary conditions on supramolecular structure, molecular arrangement and the texture of the ethyl‐cyanoethyl cellulose cholesteric liquid crystalline solutions were investigated. It was found that the molecules of (E‐CE)C are oriented to perpendicular to the magnetic field and the diamagnetic anisotropy of (E‐CE)C is negative. With homeotropic anchoring boundary condition, the molecules are aggregated with focal‐conics arrangement the molecules are aggregated with planar arrangement with homogeneous anchoring boundary condition. The effects of the external field on the orientation of the cholesteric phase were influenced by the concentration of the solution because the twist power of the cholesteric was varied with the concentration. And the effects are also restrains by the surface tension of the interphase.
Structural evidence of grafting in electron beam irradiated starch‐allylurea blends
Authors: Olivier A. , Luna‐Carlos J. , Cazaux F. , Coqueret X.
Published: April 2003

The effectiveness of covalent grafting in mixtures of N‐allylurea (AU) and amorphized starch submitted to electron beam irradiation was studied for elucidating the chemical changes at the origin of the physical stabilization observed after radiation processing. FTIR and nmr analysis were used to quantify the progress of AU conversion upon irradiation of the mixtures and to gain information on the structure of the products. The grafting yield was determined by gravimetry after selective solubilization that extracts AU monomer and its homopolymer from the covalently modified polysaccharide. MALDI‐TOF spectrometry applied to irradiated mixtures of AU and maltotriose, as a model compound, affords unambiguous evidence of covalent grafting. The obtained data allow to estimate the size of the AU grafts and to propose mechanistic pathways for radiation grafting.
Surface thermal molecular motion of chain end‐modified polystyrenes
Authors: Kajiyama Tisato , Tanaka Keiji , Takahara Atsushi
Published: April 2003

Surface glass transition temperature, Tgs, of three classes of monodisperse polystyrene, proton‐terminated (PS‐H), α,ω‐diamino‐terminated (α,ω‐PS(NH2)2) and α,ω‐dicarboxy‐terminated (α,ω‐PS(COOH)2), were studied by scanning force microscopy. Tgs of all samples was discernibly lower than the corresponding bulk glass transition temperature, Tgb. Also, Tgs value was strongly dependent on what the chemical structure of chain end groups was. Based on the time‐temperature superposition principle, apparent activation energy of the αa‐relaxation process corresponding to surface segmental motion was evaluated to be approximately 230 kJ·mol−1. This value was much smaller than the reported bulk ones, and was independent of the chemical structure of chain ends. This result implies that the cooperativity for the αa‐relaxation process at the PS surface is reduced in comparison with the bulk due probably to an existence of the free space presented to polymer segments at the surface. Hence, it was concluded that the surface αa‐relaxation process was activated by not only the chain end effect but also the reduced cooperativity at the surface.
Real‐time AFM study of lamellar growth of semi‐crystalline polymers
Authors: Luo Yan‐Hong , Jiang Yong , Jin Xi‐Gao , Li Lin , Chan Chi‐Ming
Published: April 2003

Atomic force microscopy (AFM) has been used to study the lamellar development during the crystallization and melting processes of poly(bisphenol A‐co‐alkyl ether) (BA‐Cn) films. High‐resolution and real‐time AFM phase imaging enables us to observe the detailed growth process of the lamellae. At the early stage of the lamellar growth, embryos appeared firstly and some disappeared on the film surface after a period of time. The stable embryo developed into a single lamella. Then the lamella developed into a lamellar sheaf through branching and splaying. Our results revealed that the branches of the lamellae were formed by induced nucleation and it was also dependent on the crystallization temperature. Real‐time AFM study of the melting, recrystallization and remelting processes of lamellae indicated that the thermal stability of different segments of a single lamella is different and that the thermal stability of the different lamellae is also different even if they develop at the same annealing temperature. The orientation and the development of the lamellae at the characteristic eyes and boundaries of the spherulites are observed in details.
Production of nanocomposites of PET‐montmorillonite clay by an extrusion process
Authors: Sanchez‐Solis A. , Garcia‐Rejon A. , Manero O.
Published: April 2003

Polyethylene terephthalate (PET) was mixed by extrusion with clay (montmorillonite) to produce nanocomposites. Additives (pentaerythrytol and maleic anhydride) were added to induce compatibility between the particles and the matrix. Thermal, mechanical and Theological properties of the nanocomposites were evaluated. The nanocomposites with additives presented improved mechanical strength. In shear, the viscoelastic properties decrease with rising particle concentration and additives content. The resulting new materiales present processing advantages and potential improvements in performance.
Amphiphilic and mesomorphic fullerene‐based dendrimers
Authors: Guillon Daniel , Nierengarten Jean‐François , Gallani Jean‐Louis , Eckert Jean‐François , Rio Yannick , del Pilar Carreon Maria , Dardel Blaise , Deschenaux Robert
Published: April 2003

Growing attention is currently devoted to large dendritic structures for applications in nanotechnology and materials science. In this respect, the incorporation of such compounds into thin ordered films appears to be an important issue. One of the most widely pursued approaches to structurally ordered dendrimer assemblies has been the preparation of Langmuir films at the air‐water interface. We report on the case of a diblock globular fullerene‐based dendrimer and show that peripheral substitution of the dendrimer with hydrophobic chains on one hemisphere and hydrophilic groups on the other provides the required hydrophobic/hydrophilic balance allowing the formation of stable Langmuir films. A second approach has been to consider the case of fullerene containing dendrimers terminated by mesogenic groups such as cyanobiphenyl subunits. Whatever the generation is, up to the fourth one, all these compounds exhibit a well‐defined liquid crystalline smectic A phase. The molecular organisation within the smectic layers is found to be monolayered or bilayered depending on the generation. For the smallest dendrimers, the organisation is mainly governed by the size of the fullerene moiety, whereas for the higher ones, it is governed by the interactions between the terminal mesogenic groups. These two approaches appear particularly interesting for functional groups such as fullerenes, which are not well adapted to be organised in nanoscale architectures. The present study shows that fullerenes can indeed be introduced into different types of ordered structure when they have been chemically adequately modified.
Analysis of polyamides by size exclusion chromatography and laser light scattering
Authors: Chen Jinglu , Radke Wolfgang , Pasch Harald
Published: April 2003

The molar mass analysis of polyamides is complicated due to the fact that only a limited range of solvents can be used and association and aggregation phenomena have to be screened by adding electrolytes to the mobile phase. Optimum SEC behaviour is obtained when hexafluoroisopropanol + 0.05 mol/L potassium trifluoroacetate is used as the mobile phase. The calibration of the SEC system can be conducted in different ways. While a calibration with narrow disperse polymethyl methacrylate standards does not yield accurate molar mass information, the quantification can be done using an “artificial” calibration curve. This calibration curve is obtained by correcting the PMMA calibration curve with polyamide molar mass data from light scattering. The resulting molar mass distributions for different types of polyamides are compared with molar masses that are determined by size exclusion chromatography with a light scattering detector and an excellent correlation is obtained.