bluuebunny/crossref_metadata_2025 huggingface dataset:
Molecular instabilities in capillary flow of polymer melts: Interfacial stick‐slip transition, wall slip and extrudate distortion
Authors: Wang Shi‐Qing , Drda Patrick
Published: April 2003

This article summarizes our recent experimental studies of an important class of polymer melt rheological phenomena including flow instabilities, stick‐slip transitions, interfacial melt/wall slip, gross extrudate distortion and sharkskin like surface roughening of extrudates. Our experimental results indicate that most aspects of the perplexing flow behavior of strongly entangled melts in polymer extrusion can be depicted in terms of melt/wall interfacial interactions at a molecular level. For high surface energy walls, a transition from no‐slip to slip hydrodynamic boundary condition (HBC) occurs through molecular disentanglement (coil‐to‐stretch) of adsorbed chains from unbound chains. For weakly adsorbing walls, interfacial slip takes place through a second molecular mechanism involving a stress‐induced polymer desorption process. Since the coil‐stretch transition of adsorbed chains is controlled by interfacial shear stress, the HBC can be unstable throughout the die wall under the condition of a constant flow rate, where the wall stress may fluctuate in time. Unstable HBC due to the interfacial molecular instabilities is shown to be the origin of a variety of global and local flow instabilities including the oscillating flow and the sharkskin like distortion of extrudate surface. With a set of new experiments to directly probe the interfacial molecular processes, we will be able to support the unified understanding of intriguing capillary melt flow characteristics summarized in this article.
Polymerization of cyclic monomers, 3. Synthesis, radical and cationic polymerization of bicyclic 2‐methylene‐1,3‐dioxepanes
Authors: Moszner Norbert , Völkel Thomas , Rheinberger Volker , Klemm Elisabeth
Published: April 2003

New bicyclic 2‐methylene‐1,3‐dioxepanes, were synthesized starting from 2‐bromomethyl‐5,6‐dihydroxy‐1,3‐dioxepanes. The structure of the 2‐methylene‐1,3‐dioxepanes was confirmed by elemental analysis, IR, 1H NMR and 13C NMR spectroscopy. Radical polymerization of 2‐methylene‐1,3‐dioxepanes in bulk with 2,2′‐azoisobutyronitrile (AIBN) and di‐tert‐butyl peroxide (DtBPO), respectively, gives highly viscous polymers. The polymerization of liquid monomers is accompanied by negative volume changes. The spectroscopic investigations of the formed polymers show that 2‐methylene‐1,3‐dioxepanes undergo primarily radical ring‐opening polymerization, whereas the cationic photopolymerization is mainly a vinyl polymerization.
Tailored rigid‐flexible block copolymers, 2. Intrinsic viscosity behavior
Authors: Cavalleri Piero , Chavan Nayaku N. , Ciferri Alberto , Dell'Erba Carlo , Novi Marino , Marrucci Giuseppe , Renamayor Carmen S.
Published: April 2003

The determination of single‐chain properties for heterogeneous molecules such as a rigid‐flexible block copolymer requires the use of solvents capable of reducing selective interactions involving the blocks and the diluent. Molecular dispersion is displayed by a two‐block copolymer of benzoyl‐terminated poly(p‐benzamide) (poly(imino‐1,4‐phenyl‐enecarbonyl) and anilino‐terminated poly(m‐phenyleneisophthalamide) in 96 wt.‐% sulfuric acid. For a series of such copolymers, intrinsic viscosities were measured avoiding degradation effects due to H2SO4. The intrinsic viscosity ([η]) of the copolymers was found to decrease with increasing length of the flexible block, but [η] remained larger than the value corresponding to an equimolar blend of rigid and flexible homopolymers. These results are explained by theoretical considerations within the framework of the hydrodynamic behavior of single rodlike and single coiled macromolecules.
The effects of hydrogen bonding on the miscibility, complexation and crystallization in blends of crystalline and amorphous components
Authors: Zhou Hui , Xiang Maoliang , Chen Wenjie , Jiang Ming
Published: April 2003

The miscibility and crystallization of blends of poly{styrene‐co‐[p‐(2,2,2‐trifluoro‐1‐hydroxy‐1‐trifluoromethyl)ethyl‐a‐methylstyrene]} (PS(OH)) and polycaprolactone (PCL) have been investigated by viscometry and differential scanning calorimetry. With increasing the hydroxyl content in PS(OH), the transitions from immiscibility to miscibility and then to complexation can be realized. Depending on the states in which the blends exist, a different behavior of PCL crystallization is observed. Crystallization in the immiscible blends, is almost not affected by the presence of PS(OH). In the miscible blends, an apparent depression of crystallization is observed. Particularly, for the blends with a hydroxyl content larger than 8 mol‐% in PS(OH), complete depression of PCL crystallization is found, which can be attributed to a complex formed by pairing segments of PCL and PS(OH).
Synthesis and properties of polyimides containing 2,2′‐bipyridine derivatives
Authors: Sun Xuehui , Yang Yu‐kun , Lu Fengcai
Published: April 2003

A series of polyimides containing 2,2′‐bipyridine, 7, were synthesized by reaction of 4,4′‐diamino‐2,2′‐bipyridine (4) with various aromatic dianhydrides, followed by imidization upon heating. These polyimides are fairly thermostable, and 5% weight loss occurs in the range of 484°C‐580°C. The glass transition temperatures are between 276°C and 313°C. Their poly(amic acids) 6 can be partially quaternized using 1,2‐dibromoethane and then easily imidized upon heating. The temperature of quaternized polyimides at which 5% weight loss is observed is around 300°C, the glass transition temperatures range from 202–239°C. These quaternized polyimides can also develop color under UV irradiation in a poly(N‐vinyl‐2‐pyrrolidone) (PVP) matrix with maximum absorption at 800 nm. The bipyridine‐based poly(amic acids) 6 can trap various metal ions from solution and then can be imidized by heating. The XPS data indicate the formation of a 1:1 (bipyridine: metal molar ratio) complex and a 2:1 complex. The temperature at which for the polyimide‐metal complexes 5% weight loss is observed is around 300°C. Both the poly(amic acid)‐metal complex and the polyimide‐metal complex catalyze the condensation of benzaldehyde with acetophenone, with yields of chalcone of ca. 6.7–31.7%. The order of catalytic activity for different metal ions is Zn(II) > Co(II) > Cu(II).
Experimental and simulation studies on ethyl acrylate polymerization
Authors: Gao Jun , McManus Neil T. , Penlidis Alexander
Published: April 2003

An experimental study of the bulk free radical polymerization of ethyl acrylate (EA) initiated by 2,2′‐azoisobutyronitrile (AIBN) was conducted. The experiments were carried out based on a factorial design with replicates. The reaction variables investigated were initiator concentration, temperature and chain transfer agent (CTA) concentration (primary octanethiol). The results obtained were used to develop and test a simulation model for EA homopolymerization.
Poly(triacontamethylene triacontanedioate) as polyethylene analogue: Properties and enzymatic degradation
Authors: Cho Iwhan , Lee Kyoolseop
Published: April 2003

Diethyl triacontanedioate (CH3CH2O2C(CH2)28CO2CH2CH3) and triacontane‐ 1,30‐diol (HO(CH2)30OH) were prepared and condensed to synthesize poly(triacontamethylene triacontanedioate) (PTRM). The properties of (PTRM) were compared with those of commercial low density polyethylene (LDPE), and enzymatic degradation of the PTRM was investigated. PTRM showed not only high melting point of 113°C and a thermal stability comparable to LDPE. The elongation at break is low (about 5%) and the tensile strength is around 12.5 MPa, higher than that of LDPE. The small contact angles indicate that PTRM has good wettability compared with LDPE. The increase of total organic carbon by Rhizopus arrhizus lipase and the resulting change of surface morphology confirmed that PTRM is biodegradable.
Saccharide polymers, 2. Synthesis and polymerization of exo‐glucal derivatives
Authors: Yaacoub Emile‐Joseph , Skeries Bernhard , Buchholz Klaus
Published: April 2003

Unsaturated glucopyranose derivatives such as 1,2,3,4‐tetra‐O‐acetyl‐6‐desoxy‐β‐D‐xylo‐hex‐5‐enopyranose (3) and 1,2,3,4‐tetra‐O‐benzoyl‐6‐desoxy‐β‐D‐xylo‐hex‐5‐enopyranose (6), briefly called “Ac‐exo‐glucal (3)” and “Bz‐exo‐glucal (6)”, were synthesized. These exo‐cyclic sugar vinyl ethers were investigated in polymerization reactions. The corresponding “saccharide polymers”, homo‐ and copolymers, were synthesized under free radical conditions. The structures and the compositions of the soluble “saccharide polymers” were established by elemental analysis, 1H and 13C NMR, and FTIR spectroscopy. Characterization of the polymers, like molecular weights and optical rotations are reported. Saccharide polymers with different sugar content and low as well as high molecular weights were obtained.
Doped non‐conjugated polymers with enhanced electrical conductivity, 3. Iodine doping of a liquid crystalline polymer
Authors: Sinigersky Vesselin , Madec Pierre‐Jean , Maréchal Ernest , Schopov Ivan
Published: April 2003

Doping with iodine of a liquid crystalline polymer in its different states was investigated for the first time. It was established that the polymer cannot be doped in solution, but it was doped to different, but rather high levels in the solid state and in frozen liquid crystalline and isotropic states. The products obtained exhibit intensive absorption in the visible region, higher electrical conductivity and paramagnetism. The successful doping of this non‐conjugated polymer in the solid state was explained by a collective interaction of several conjugated parts of the macromolecules (acting as extended conjugation) with iodine.
Asymmetric block copolymers in neutral good solvents: self‐diffusion through the ordering transition
Authors: Lodge Timothy P. , Blazey Matthew A. , Liu Z. , Hamley Ian W.
Published: April 2003

The self‐diffusion coefficients of a styrene‐isoprene diblock and a styrene‐isoprene‐styrene triblock copolymer have been measured as functions of concentration in the neutral good solvent toluene. The sample block molecular weights are 1.0 × 104 and 5.0 × 104 g/mol for the diblock, and 1.0 × 104, 1.0 × 105 and 1.0 × 104 g/mol for the triblock, and the samples are designated SI‐60 and SIS‐120, respectively. Synchrotron small‐angle X‐ray scattering was utilized to locate the ordering transitions, and to identify the morphologies. SI‐60 exhibited an order‐order transition from a hexagonal to a cubic structure (i.e., from cylinders to spheres), prior to disordering, whereas SIS‐120 only exhibited the hexagonal phase. These results were compared to the melt, where both materials exhibit the cylinder‐to‐sphere transition. The concentration range for diffusion measurements extended into the ordered state: weight fractions up to 0.78 for SI‐60 and 0.62 for SIS‐120, where the corresponding ordering concentrations are 0.67 and 0.56. Diffusion measurements were performed by forced Rayleigh scattering and by pulsed‐field‐gradient NMR. The results indicate that substantial concentration fluctuations arise in solution prior to the ordering transition, and that these fluctuations act to retard chain diffusion. However, from comparison of the diblock and triblock mobilities, it appears that the retardation of mobility in the fluctuating and ordered states is due more to the increased monomeric friction in the (cylindrical) styrene‐rich microdomains, than to the thermodynamic barrier for escape of the styrene blocks from these microdomains.
Poly(2‐vinylpyridine)‐based star‐shaped polymers. Synthesis of heteroarm star (AnBn) and star‐block (AB)n copolymers
Authors: Tsitsilianis Constantinos , Voulgaris Dimitris
Published: April 2003

Heteroarm star copolymers bearing poly(2‐vinylpyridine) and polystyrene arms (AnBn type) were synthesized by a three‐step anionic polymerization method. Polystyrene arms are synthesized first, and they are used to initiate the polymerization of a small amount of divinylbenzene, yielding polystyrene star molecules bearing a number of active sites within its cores. In a subsequent step poly(2‐vinylpyridine) arms are growing from the cores. Poly(2‐vinylpyridine)‐block‐poly(tert‐butyl acrylate) star block copolymers [(AB)n type] were also prepared using the same synthetic route. In this case, short polystyryllithium is used to build grafted poly(DVB) cores. These living plurifunctional initiators can easily polymerize 2‐vinylpyridine and subsequently tert‐butyl acrylate, yielding star molecules bearing diblock copolymers as arms. The short polystyrene grafts of the core can be neglected and the star molecules are considered of the (AB)n type. These star polymers have been characterized adequately and shown to exhibit rather well‐defined structures. The advantages and the drawbacks of the method are discussed.
Cylindrical morphologies in asymmetric ABC triblock copolymers
Authors: Breiner Ulrike , Krappe Udo , Abetz Volker , Stadler Reimund
Published: April 2003

In asymmetric ABC triblock copolymers with C being the matrix‐forming majority component, the formation of cylindrical morphologies is governed by the sum of the volume fractions of the components A and B (ϕA + ϕB) as well as by their ratio (ϕB/ϕA). The paper describes the morphologies of various polystyrene‐block‐polybutadiene‐block‐poly(methyl methacrylate) (SBM) and polystyrene‐block‐poly(ethylene‐co‐butylene)‐block‐poly(methyl methacrylate) block copolymers (SEBM) in dependence on these parameters. In addition to previously reported cylinder in cylinder (cic, core shell) and helical (hel) morphologies, new microphase separated structures as cylinders at cylinder (cac), undulated/perforated cylinder in cylinder (ucic) and spheres on cylinder (soc) are discussed. Based on a simple theoretical approach the transitions between these various morphologies are predicted, especially focusing on the transition between the cic and cac morphologies.
Synthesis and characterization of 3‐hexyl multi‐substituted α,ω‐diformyl‐α‐oligothiophenes (n = 3, 6, 8)
Authors: Olinga Thamas , Destri Silvia , Porzio William , Selva Antonio
Published: April 2003

The synthesis and characterization of a series of thienylenic α,ω‐diformyl‐α‐oligothiophenes with 3, 6 and 8 residues is reported. The chemical structure was determined by 1H NMR, FT‐IR, mass and GPC analyses, while the electronic properties in the neutral state were studied by UV‐Vis spectroscopy both in solution and in the solid state. In the UV‐Vis spectra of thin films, the vibronic structure is observed. The pronounced red‐shift of the absorption maximum, with respect to spectra of unsubstituted α‐oligothiophenes, is indicative of a contribution of carbonyl π‐electrons to the overall delocalization via a mesomeric effect leading to a more planar structure. The solid state aggregation was investigated by XRD spectroscopy and optical microscopy. We observed for the longest terms a smectic arrangement typical of liquid crystalline compounds and a tendency to self‐assembling onto hydrophilic substrates, forming angles ranging from 40–50° with respect to the normal to the surface.
Polymer modification of ethylene‐acrylic copolymers in near‐critical water
Authors: Buback Michael , Elstner Uta , Rindfleisch Frank , McHugh Mark A.
Published: April 2003

Modification reactions are reported for fully‐hydrogenated butadiene‐acrylonitrile (35.8 mol‐% AN) copolymer, ethylene(E)‐butyl acrylate (4.7 mol‐% BA) copolymer, and ethylene(E)‐methyl acrylate (45 mol‐% MA) copolymer in dense, near‐critical water at 250°C and 300°C and at 300 bar and 1500 bar. Nitrile, amide, and ester moieties can be converted into COOH groups, Kinetic analysis of the ester to acid transformations suggests autocatalytic activity of the acid groups.
Synthesis and cationic polymerization of a novel optically active vinyl ether with L‐proline structure
Authors: Sanda Fumio , Endo Takeshi
Published: April 2003

Synthesis and cationic polymerization of a novel vinyl ether with an L‐proline moiety, N‐carbobenzoxy‐L‐proline 2‐vinyloxyethyl ether (ZProVE), were carried out. ZProVE was prepared by the condensation of N‐carbobenzoxy‐L‐proline and 2‐hydroxyethyl vinyl ether. Cationic polymerization of ZProVE was carried out in dichloromethane at −50, −20°C, or room temperature. The number‐average molecular weight (Mn) of the polymer obtained in the polymerization at −50°C was 44900, and the [α] value of the polymer was −36.1°, which was somewhat larger (more positive) than that of ZProVE (−46.4°). Cationic copolymerizations of ZProVE and isobutyl vinyl ether proceeded readily to afford the corresponding copolymers. Alkaline hydrolysis of poly(ZProVE) afforded poly(hydroxyethyl vinyl ether).
Gel‐sol transition of methylcellulose
Authors: Nishinari Katsuyoshi , Hofmann Kate E. , Moritaka Hatsue , Kohyama Kaoru , Nishinari Noriko
Published: April 2003

The gelation mechanism of aqueous solutions of methylcellulose (MC) with different molecular weights was studied by small deformation oscillation rheological measurments and differential scanning calorimetry (DSC). The gelation is promoted by the increase in molecular weight of MC: the elastic modulus becomes larger, the gelation occurs at lower temperatures and the DSC peaks accompanying the gel‐sol transition become sharper. Cooling DSC curves split into two peaks, indicating that the gel‐to‐sol transition occurred via two steps.
Ternary systems involving rod/coil/solvent: poly(p‐benzamide)/poly(2‐phenylene(5‐benzimidazole)‐isophthalamide)/dimethylacetamide + LiCl
Authors: Bianchi Estella , Marsano Enrico , Costa Camilla , Conio Giuseppina , Bisbano Stefania
Published: April 2003

The ternary diagram involving a rigid polymer [poly(p‐benzamide) (PBA)], a flexible polymer [poly(2‐phenylene(5‐benzimidazole)isophthalamide)

Structure‐based name: poly(benzimidazole‐2,5‐diyl‐iminoisophthaloylimino‐1,4‐phenylene).

(PABI)] and a diluent composed of dimethylacetamide plus 3 wt.‐% LiCl (DMAc/3LiCl) was investigated. Addition of PABI to PBA solutions increases the critical volume fraction value at which a nematic phase is observed. The line connecting these values at different PBA/PABI ratios divides a region of isotropic solutions from a biphasic area. No case of a single anisotropic phase was observed. A peculiarity of the diagram is that the composition of the anisotropic phase in the biphasic region lies on the PBA‐diluent axis when the molecular weight of PABI is relatively high, whereas it shows a small content of PABI when its molecular weight is low. This result has recently been theoretically predicted by considering the existence of anisotropic interactions in the mesophase. The agreement between theoretical and experimental phase diagrams is fairly good.
Isotactic 1‐butene polymerization promoted by C2‐symmetric metallocene catalysts
Authors: Borriello Anna , Busico Vincenzo , Cipullo Roberta , Fusco Ofelia , Chadwick John C.
Published: April 2003

1‐Butene polyinsertion promoted by two typical C2‐symmetric zirconocene catalysts (i.e. rac‐ethylenebis(1‐indenyl)ZrCl2 (1) and rac‐dimethylsilylbis(1‐indenyl)ZrCl2) (2) was investigated under both hydrooligomerization and polymerization conditions and compared with that of propene. It was found that, in spite of a similar regiospecificity for the two monomers, the fraction of “dormant” sites is higher in 1‐butene polymerization, as a result of a (much) lower reactivity of a 2,1 last‐inserted unit. Accordingly, in the investigated cases, 2,1 units of 1‐butene were not incorporated in the growing chains but either isomerized to 4,1 units or remained at the chain end until they underwent chain transfer via β‐hydrogen elimination. Experimental evidence is also presented of an epimerization reaction of the growing poly(1‐butene) chain with a 1,2 last‐inserted unit, leading to a decrease of polymer stereoregularity with decreasing monomer concentration.
Thermal behavior of some polyarylene ethers: A comparative study of the kinetics of degradation
Authors: Abate Lorenzo , Calanna Sabrina , Pollicino Antonino , Recca Antonino
Published: April 2003

The degradation of four aromatic thermoplastics containing carbonyl, ether and sulfone linkages was performed in a thermogravimetric analyzer in both nitrogen and air environments, in isothermal and dynamic heating conditions. The obtained results suggest that degradations started by random chain scission under all the experimental conditions. Under N2 flow branching and crosslinking were superimposed on the initial process, while in air complete oxidative degradation occurred. The apparent activation energies associated with the first degradation stage were evaluated and correlated with the linkages present in the polymer chains. The obtained values indicate that the chemical reactions occurring under nitrogen are different from those in air. In addition, the ratio of the chain scission rate to the branching and crosslinking rates in nitrogen is dependent on temperature in isothermal experiments and on heating rate in the dynamic ones. A comparison with poly(ether ether ketone) is also reported.
Synthesis of fluorescence‐labelled short‐chain polyester segments for the investigation of bioresorbable poly(ester‐urethane)s
Authors: Ciardelli Gianluca , Saad Bashar , Lendlein Andreas , Neuenschwander Peter , Suter Ulrich W.
Published: April 2003

The synthesis and characterization of fluorescence‐labelled low‐molecular‐weight polyesters based on known biocompatible and degradable materials such as poly[(R)‐3‐hydroxybutyric acid] (PHB) and poly(ε‐caprolactone‐co‐glycolide) is described. A telechelic OH‐terminated poly[(R)‐3‐hydroxybutyric acid] (Mn= 2300) was modified at the end groups through esterification with BOC‐glycine. After removal of the BOC protection, the so‐obtained free amino groups were conjugated with dansyl chloride to obtain dansyl‐labelled end groups. No degradation of the starting material was observed during the several synthetic steps, while the crystallinity of the material was not significantly affected by the modification of the end groups. Fluorescence‐labelled low‐molecular‐weight poly(ε‐caprolactone) and poly(ε‐caprolactone‐co‐glycolide) were obtained by bulk ring‐opening polymerization of the corresponding cyclic monomers (ε‐caprolactone and diglycolide) with dansylcadaverine. Both random (amorphous) and block (semi‐crystalline) copolymers were obtained depending on the presence of the catalyst (Bu2SnO). The so obtained fluorescence‐labelled polyesters are promising materials for the investigation of the biocompatibility and degradation of block poly(ester‐urethane)s (Degra‐Pol®) with fluorescence‐aided microscopic and spectroscopic techniques.
Redox‐initiated radical polymerization of 2‐hydroxyethyl methacrylate, 3. Copolymerization with nine monomers, effect of structure and media on the reactivity of monomers
Authors: Mathew‐Krotz Jainamma , Mahadevan Venkatanarayana
Published: April 2003

Copolymerization of 2‐hydroxyethyl methacrylate (HEMA) with eight acrylic monomers and vinyl acetate using redox initiators was carried out in DMF and in aqueous medium. Reactivity ratios were calculated according to the general copolymerization equation using Fineman‐Ross, Kelen‐Tüdős and the YBR methods. The results indicate that reactivity of the methacrylates towards growing HEMA radicals decreased in the order, methyl methacrylate > 2‐dimethylaminoethyl methacrylate > 2,3‐epoxypropyl methacrylate. Reactivity of the acrylates decreased in the order butyl acrylate > ethyl acrylate > methyl acrylate. In the HEMA‐acrylate systems, the intrinsic viscosity of the copolymers decreased with increasing content of the acrylates in the copolymer. On the other hand, the intrinsic viscosity of the copolymers of HEMA‐MMA showed an increasing trend with increasing content of MMA in the copolymer. Changing the polymerization medium from DMF to water resulted in copolymers having a higher HEMA content.
Synthesis and characterization of polymers containing 4‐cyanobiphenyl‐based side groups for nonlinear optical applications, 3. Poly(p‐chloromethylstyrene) derivatives
Authors: Noël Claudine , Gangadhara  , Ching Kathlen Chane , Large Maryanne , Reyx Danièle , Kajzar François
Published: April 2003

Poly[p‐(4′‐cyanobiphenyl‐4‐yloxymethyl)styrene]s (PCBMS) were prepared by chemical modification of poly(p‐chloromethylstyrene) with the sodium salt of 4‐cyano‐4′‐hydroxybiphenyl or free radical polymerization of p‐(4′‐cyanobiphenyl‐4‐yloxymethyl)‐styrene (CBMS). The latter method appeared to be a good one for the preparation of polymers with high glass transition temperature and high chromophore content if performed in dimethyl sulfoxide. There was no real evidence for liquid crystal properties in the resulting polymers, which resemble typical amorphous isotropic polymers. This indicates that these polymers should be considered to be polyethylene containing the benzyl ether of 4‐cyano‐4′‐hydroxybiphenyl as the mesogenic group attached directly to the backbone, and not as polystyrenes containing the cyanobiphenyl group attached to the backbone through a OCH2spacer. Some preliminary Corona poling experiments were performed, and the second harmonic generation coefficients d31 and d33, were measured by Maker fringe analysis. Interestingly, the ratio of d33 to d31 was found to be 6, which is much larger than the value of 3 predicted by the molecular statistical model for electric field poling of isotropic systems. This was attributed to conformational constraints on chromophore ordering as expected in such polymers containing no flexible spacer.
Gas sorption in substituted polyacetylenes
Authors: Bondar Valeri , Alentiev Alexander , Masuda Toshio , Yampolskii Yuri
Published: April 2003

Sorption of several gases (He, N2, Ar, CH4, CO2, C2H6) was measured in an extended pressure range (up to 100 at m) in two glassy polyacetylenes: poly[1‐phenyl‐2‐(p‐tert‐butylphenyl)acetylene] and samples of poly[1‐(trimethylsilyl)‐1‐propyne] (PTMSP), which were partly oxidized during long term storage in the ambient atmosphere. Sorption isotherms are concave to the pressure axis and can be described by the dual mode sorption model. Both polyacetylenes are distinguished by relatively large Langmuir sorption capacity parameters C′H. However, the C′H values and solubility coefficients are significantly lower than those of fresh PTMSP.
Polylactones, 38. Polymerization of L‐lactide with Fe(II) lactate and other resorbable Fe(II) salts
Authors: Kricheldorf Hans R. , Damrau Dirk‐Olaf
Published: April 2003

Commercial FeCl2 and Fe(II) glycolate, Fe(II) L‐lactate or Fe(II) L‐mandelate were used as initiators for the polymerization of L‐lactide. All polymerizations were conducted in bulk at 150°C, because no conversion was observed in bulk at 120°C. The Fe(II) lactate was found to be more reactive than FeCl2, and it yielded slightly higher molecular weights than all other initiators. Under the optimum conditions, viscosity average molecular weights (M̄v) around 50 000 and yields above 90% were obtained. However, slight racemization (2–5%) of the isolated poly(L‐lactide) was also observed under most circumstances. Characterization of unreacted monomer proved that the racemization mainly involves the monomeric lactide due to its higher CH acidity.
Mobile macromolecular carriers of ionic substances, 1. Transport of heavy metal ions by polymer analogues of teichoic acids
Authors: Wódzki Romuald , Kałużyński Krzysztof , Kłosiński Paweł
Published: April 2003

Bioanalogous organic polyphosphates (PP) and polymer ion‐exchange membranes (IEM) were used to arrange a membrane system for the transportation of Zn(II), Mn(II), Cu(II), Co(II) and Ni(II) ions. The system consists of three membranes separating a feed and a strip solution with metal sulfates and sulfuric acid, respectively:

Poly(trimethylene phosphate), α‐hydroxy‐ω‐(2‐ethylhexyl)poly(trimethylene phosphate), poly(1,2‐glycerol phosphate) and poly(2,3‐acetoxyglycerol phosphate) were used as ionic carriers for mimicking some transport functions of natural teichoic acids. These polyelectrolytes were found to facilitate the exchange‐diffusion process of heavy metal ions and to exhibit fluxes in the range 3,5 · 10−9 – 6 · 10−9 mol M(II)/(cm2 · s). The specific stationary fluxes typically change in the order JCu > JCo > JNi > JMn > JZn. The observed transport preference is consistent with the affinity order of teichoic acids or the bacteria cell wall toward Cu(II), Mn(II) and Zn(II).
Solid state behaviour and properties of compression moulded poly(ether ether ketone)/polysulfone blends
Authors: Arzak Andone , Eguiazábal José Ignacio , Nazábal Jon
Published: April 2003

Poly(ether ether ketone) (PEEK)/polysulfone (PSF) blends were obtained by kneading and compression moulding over the whole composition range. The blends were then both quenched and slowly cooled. Both cooling procedures provided blends with two practically pure phases and good small strain properties. Ductility was worsened, as expected, in slowly cooled blends. However, in quenched blends, which provided less phase‐separated fracture surfaces and no very different free volume, ductility showed unexpected good values which are tentatively attributed to common features of the chemical structure of both blend components.
Performance‐improved photo‐driven liquid crystal cell using azobenzene‐grafted ladderlike polysiloxane as command layer
Authors: Tang Yongxin , Xie Ping , Liu Dongsheng , Zhang Rongben , Zhang Zhiyong , Yao Naiyan
Published: April 2003

In comparison with our previous work1, the stability of the command layer based on an azobenzene‐grafted ladderlike copoly(hydromethylsilsesquioxane) (PMHSQ) coated on quartz plates, is improved evidently by linking through a coupling reagent (triethoxyvinylsilane) to the backbone. The liquid crystal (LC) cell filled with 4‐cyano‐4′‐pentylbiphenyl (5CB) exhibits a much faster switching behavior, so that activation is unnecessary. The results show that the photo‐driving behavior is strongly dependent on the nature of the LCs as well as the structure of the azobenzene (Az) side chains. The cyanobiphenyl type LC (5CB) with a strong polarity sandwiched between such two command layers changes the alignment between homeotropic and planar modes while TC3 (mainly phenylcyclohexanecarboxylates) with a weak polarity fails to do so. The Az units with longer spacer are more effective to induce changes of the LC alignment. It was found that the phenyl benzoates are not stable to ultraviolet (UV) irradiation and that they absorb the UV light strongly. Thus, we suppose that such negative aspects as the necessary activation and the slow response of our previously studied photo‐driven LC cell using commercial TEB‐30 (mainly cyanobiphenyls and phenyl benzoates as well) are caused by the phenyl benzoate components.
Network parameters and scaling behaviour of chemically crosslinked hydrogels of poly[(N,N‐dimethylacrylamide)‐co‐(methyl methacrylate)]
Authors: Liu Yan , Mao Runsheng , Huglin Malcolm B. , Holmes Paul A.
Published: April 2003

Copolymerization of N,N‐dimethylacrylamide (DMA) with methyl methacrylate in both the presence and absence of ethylene dimethacrylate (EDMA) was effected to very high conversion by γ‐irradiation. The resultant xerogels were swollen to equilibrium in water at five specific temperatures within the interval 280.2–338.2 K. The volume fractions of the polymer ϕ2 in the hydrogels were determined from the measured dimensions, and compression‐strain measurements yielded the polymer‐water interaction parameter, the effective crosslinking densities, and Young's moduli Y. The observed dependence of these parameters on copolymer composition and content of EDMA is discussed. A scaling law of the form Y ∝ ϕ is obeyed well by hydrogels of xerogels containing 80 wt.‐% DMA (r = 2.37 ± 0.10) and moderately well by hydrogels of xerogels with only 50 wt.‐% DMA (r = 2.54 ± 0.10).
Bulk polymerization of lactides initiated by aluminium isopropoxide, 2. Beneficial effect of lewis bases and transfer agents
Authors: Degée Philippe , Dubois Philippe , Jérôme Robert
Published: April 2003

A high increase in the bulk polymerization rate of L,L‐lactide and racemic D,L‐lactide is observed when aluminium isopropoxide is added with an equimolar amount of a Lewis base, such as triphenylphosphine (P(ϕ)3) and better 4‐picoline (C6H7N). Polylactide of high molecular weight and narrow molecular weight distribution is accordingly prepared in a controlled manner when the Al(OiPr)3 · C6H7N combination is used as an initiator over a large temperature range from 110 to 180°C. A secondary alcohol, such as 2‐propanol, has proved to be an efficient transfer agent, which allows the amount of Al per kg of polylactide to be advantageously reduced. All the alcohol molecules participate in the ring‐opening polymerization even at an [iPrOH]0/[Al] ratio as high as 103.
Bulk polymerization of lactides initiated by aluminium isopropoxide, 3. Thermal stability and viscoelastic properties
Authors: Degée Philippe , Dubois Philippe , Jérôme Robert
Published: April 2003

The thermal stability of poly(L‐lactide) and L/D‐lactide stereocopolymers polymerized in bulk with aluminium isopropoxide as initiator was investigated by thermogravimetric analysis, and time and temperature dependence of molecular weight and polydispersity. Compared to poly(L‐lactide) prepared with stannous octoate as catalyst the thermal stability of polylactides is remarkably enhanced when the ring‐opening polymerization is initiated by aluminium alkoxide. Ultimate mechanical properties and viscoelasticity of these melt‐stable thermoplastics have also been studied in relation to the polyester enantiomeric composition.
Low molecular weight poly(imide‐amide)s obtained by copolycondensation of 4,4′‐methylenedi(phenyl isocyanate), trimellitic anhydride and benzoic acid in N‐methyl‐2‐pyrrolidone, 3. Absolute number‐average molecular weights and glass transition temperatures
Authors: Sintès‐Zydowicz Nathalie , Pham Quang Tho , Dubois Jacque , Michaud Philippe
Published: April 2003

In depth study of low molecular weight poly(imide‐amide)s (PIA) obtained by copolycondensation of 4,4′‐methylenedi(phenyl isocyanate), trimellitic anhydride and benzoic acid by 1H and 13C NMR spectroscopy and size‐exclusion chromatography allows the determination of their absolute number‐average molecular weights M̄n, abs. Viscosimetric measurements reveal that, dissolved in N‐methyl‐2‐pyrrolidone, these low molecular weight PIAs should be semi‐rigid because of the presence of very short crystalline chains. By using the semi‐empirical Fox‐Flory relation, the extrapolated glass transition temperature equals 300°C for high molecular weight.
Regularities of γ‐ray induced polymerization for two mesogen‐containing acrylic monomers
Authors: Yuranova Tat'yana I. , Vasilets Victor N. , Kovalchuk Anatolii V. , Savenkov Gennadii N. , Zubarev Evgenii R. , Otmakhova Olga A. , Talroze Raisa V.
Published: April 2003

The possibility of γ‐ray induced polymerization for acrylic monomers with different mesogenic groups is studied. The irradiation of the monomers in the condensed phase shows the competition of decomposition and polymerization in the initial stage of the irradiation process. The influence of the phase state and chemical structure of initial monomers as well as irradiation conditions on the kinetics of γ‐ray induced polymerization and characteristics of resultant polymers is shown and discussed. For irradiation doses below 1 kGy, the phase behavior of monomer‐polymer systems depends on their miscibility below and above the melting point of the initial monomer and is quite different for the monomers investigated.
Preparation and properties of polymides, polyamides and poly(amide‐imide)s based on a spirobichroman dietheramine
Authors: Hsiao Sheng‐Huei , Yang Ching‐Yen
Published: April 2003

A novel diamine, 7,7′‐bis(4‐aminophenoxy)‐4,4,4′,4′‐tetramethyl‐2,2′‐spirobichroman (3), was synthesized and used as a monomer with various aromatic tetracarboxylic dianhydrides, dicarboxylic acids and imide ring‐containing dicarboxylic acids, to synthesize polymides, polyamides and poly(amide‐imide)s, respectively. The polyimides 5a–f were prepared from diamine 3 and various aromatic tetracarboxylic dianhydrides via a conventional two‐stage procedure. The intermediate poly(amic acid)s had inherent viscosities of 0,84 – 1,65 dL/g and could be thermally converted into transparent, flexible, and tough polyimide films. Some polyimides were readily soluble in polar solvents such as N,N‐dimethylacetamide (DMAc) and N‐methyl‐2‐pyrrolidone (NMP). The glass transition temperatures (Tg) of these polyimides were in the range of 155–280°C, and 10% weight loss temperatures were above 450°C in air or nitrogen. Furthermore, a series of polyamides and poly(amide‐imide)s having inherent viscosity between 0,40–1,69 dL/g were prepared by direct polycondensation of the diamine 3 with various aromatic dicarboxylic acids and imide ring‐containing dicarboxylic acids. All the polyamides and poly(amide‐imide)s were soluble in a variety of organic solvents and could be solution‐cast into flexible and tough films. They had Tg values in the 150–237°C range and showed no significant weight loss below 400°C in air and nitrogen atmosphere.
Synthesis and optical properties of polyureas with azoaromatic groups in the main chain
Authors: Lee Taek Seung , Kim Dong‐Yu , Jiang Xin Li , Li Lian , Kumar Jayant , Tripathy Sukant
Published: April 2003

We report the synthesis and optical properties of two different polyureas containing azo units in the main chain. The polymers were synthesized from the reaction between a diisocyanate and a diaminoazo compound (4,4′‐diaminoazobenzene) with good yield. These polyureas have glass transition temperatures around 197°C and the films of these polymers show an absorption maximum at 380 nm due to the azo chromophore. Upon polarized laser irradiation at 488 nm, dichroism was optically induced in these main‐chain azoaromatic polymers with a fairly high glass transition temperature. In addition we observed a degree of polar order by corona poling and a build up of second harmonic signal. It is conjectured that the induced order results mainly from an alignment of azo units through trans‐cis‐trans isomerization, as well as from the molecular rearrangement of the polyurea backbone. We further observed regularly‐spaced surface relief gratings on the polyurea film upon exposure to an interference pattern of polarized argon laser beams. Large scale molecular migration in this high glass transition temperature (Tg) polymer at room temperature was achieved for the first time.
Dethreading during the preparation of polyrotaxanes
Authors: Gong Caiguo , Gibson Harry W.
Published: April 2003

Using a diol blocking group, bis(p‐tert‐butylphenyl)bis[p‐(2‐(2‐hydroxyethoxy)ethoxy)phenyl]methane (diol BG 1), a diol with a sterically large core, copolysebacate 30‐crown‐10 (30C10) rotaxanes 8, 9 and 10 were synthesized by incorporating different amounts of 1,10‐decanediol. These copolymeric rotaxanes were characterized by different techniques, including proton NMR spectra, hydrolytic recovery of 30C10 and 2D NOESY. It was found that threaded 30C10 displayed a range of chemical shifts corresponding to the various sequence structures in which it was constrained. In addition, it was proved that the threading efficiency (m/n value, the average number of cyclic molecules per repeating unit) increased with feed ratio of diol BG 1 vs. 1,10‐decanediol. A linear relationship of threading or dethreading degree vs. the percentage of diol BG in the total diol feed was revealed; more BG, less dethreading. The results demonstrate that dethreading occurs during the polycondensation in the absence of BGs.
Branched poly(ethylene glycol) linkers
Authors: Martinez Anthony , Pendri Annapurna , Xia Jing , Greenwald Richard B.
Published: April 2003

Novel types of methoxy poly(ethylene glycol) (PEG) linkers (U‐PEG linkers) have been synthesized. These PEG linkers are linear polymers that attach to bioactive agents via a functional group, derived from a 2° alcohol, located in the center of the polymer chain versus the traditional terminal attachment site. These new types of linkers can be prepared with different functional groups (e.g. active ester, succinimidyl carbonate, and carbazate) for selected point of attachment, including ethylene oxide oligomers to provide “stems” when steric factors need to be addressed. Conversion of p‐nitrophenyl carbonates to the more desirable succinimidyl carbonates has also been accomplished by a novel nucleophilic displacement procedure. Modification of proteins with these reagents is easily accomplished and is illustrated by the conjugation of a U‐PEG linker with L‐asparaginase.
Photo‐cross‐linkable poly(p‐phenylene)s. Synthesis, Langmuir‐Blodgett multilayer film properties and pattern formation
Authors: Remmers Marcus , Neher Dieter , Wegner Gerhard
Published: April 2003

We describe the synthesis of a soluble poly(p‐phenylene) (PPP) derivative with hydroxy‐functionalities in the side chain by copolycondensation. This allows the introduction of further functionalities by polymer analogous reactions. Esterification with cinnamoyl chloride leads to a photo‐reactive material that can be processed by the Langmuir‐Blodgett (LB)‐technique to form ultrathin, highly anisotropic films. Photo‐irradiation of these films leads to the formation of cross‐links which lock in the long range ordered structure of the layered films which then becomes stable to temperatures of more than 160°C. Cross‐linking is achieved by direct irradiation into the absorption band of the photo‐reactive units or by use of sensitizers, which gives rise to more efficient reaction conditions with fewer side‐reactions. Since the cross‐linked film is insoluble in all solvents, the photo‐reactive material serves as photo‐resist. Irradiation through a mask followed by dissolution of the non‐cross‐linked film can be used for microlithography at micron scale resolution.
Vapour‐liquid equilibria of concentrated poly(styrene‐co‐butadiene) and poly(styrene‐co‐acrylonitrile) solutions
Authors: Wohlfarth Christian
Published: April 2003

Isopiestic vapor sorption measurements were carried out for concentrated solutions of poly(styrene‐co‐butadiene) (SBR) and poly(styrene‐co‐acrylonitrile) (SAN) in a number of aromatic solvents in the temperature range of 343 to 398 K. Henry constants were determined by means of inverse gas‐liquid chromatography in the temperature range of 373 K (SBR) or 423 K (SAN) to 473 K, to obtain additional data at infinite dilution for the solvents, and for two of the monomers, styrene and 1,3‐butadiene, in SBR.

The chain‐of‐rotators (COR) equation of state model was used to calculate the thermodynamic quantities applying a group‐contribution approach. In general, good agreement is observed between experimental and calculated results.
Aromatic polyethers with oxadiazole units – synthesis and application in organic light emitting diodes
Authors: Brütting Rita , Pösch Peter , Strohriegl Peter , Buchwald Elke , Brütting Wolfgang , Schwoerer Markus
Published: April 2003

Detailed synthetic aspects of new aromatic polyethers containing oxadiazole units are described. They are obtained by the nucleophilic displacement reaction of 2,2‐bis(4‐hydroxyphenyl)hexafluoropropane with 2,5‐bis(4‐fluorophenyl)‐1,3,4‐oxadiazole and 2,5‐bis(4‐fluoronaphthyl)‐1,3,4‐oxadiazole. The purity of the polyethers strongly depends on the reaction solvent. Best results were achieved with Ph2SO2 as compared to N‐methyl‐2‐pyrrolidone (NMP) and 1,3‐dimethyltetrahydro‐2(1H)‐pyrimidinone (DMPU) in the temperature range from 190–200°C. All polyethers are fully soluble in common organic solvents and excellent films are obtained by spin‐coating. High molecular weight polyethers without oligomers were only achieved, when Ph2SO2 was used as solvent. All polyethers are characterized by high thermal stability and high glass transition temperatures. The substitution of bisphenyloxadiazole by bisnaphthyloxadiazole units in the polyethers leads to a bathochromic shift of the absorption from 299 nm to 345 nm. Polyethers with bisnaphthyloxadiazole units show a blue fluorescence with a maximum at 427 nm. The application of these novel polyethers as efficient electron transport and injection layer in bilayer light emitting diodes based on poly(1,4‐phenylenevinylene) is shown. The best results were obtained with oxadiazole polyethers containing bisnaphthyloxadiazole units.
Propene polymerization with zirconocene catalysts supported on siloxane copolymers
Authors: Soga Kazuo , Ban Hoang The , Arai Takashi , Uozumi Toshiya
Published: April 2003

A supported version of zirconocene catalysts on siloxane copolymers having 1,2,3,4‐tetramethylcyclopentadienyl (Cp″)‐fluorenyl (Flu) (I) or cyclopentadienyl (Cp)‐fluorenyl (II) groups as substituents was prepared and applied to propene polymerization using methylalumoxane (MAO) or [Ph3C][B(C6F5)4] as cocatalyst. Catalyst (I), which was soluble in toluene, exhibited very low activity, whereas catalyst (II), which was composed of a toluene soluble (Cat‐A) and an insoluble fraction (Cat‐B), displayed a fairly high activity. Both catalysts (A and B) give a mixture of syndiotactic, atactic and a small quantity of isotactic polypropene, with a fraction of syndiotactic pentads ranging from about 50–75%. In contrast, the corresponding non‐supported catalyst gives almost completely atactic polypropene.
Soluble, well‐defined copper(I) and silver(I) coordination polymers from 4,4″‐bis((9‐aryl)‐2‐o‐phenanthrolinyl)‐2′,5′‐dihexyl‐p‐terphenyl
Authors: Velten Ulf , Lahn Brigitte , Rehahn Matthias
Published: April 2003

A novel synthetic concept is presented which allows, for the first time, the preparation of soluble, constitutionally well‐defined transition‐metal coordination polymers of considerable molecular weights from kinetically unstable, pseudotetrahedral copper(I)‐ and silver(I)‐phenanthroline complexes. It is demonstrated that rigorous exclusion of all molecules that might act as competitive ligands for the metal ions of the polymer constitutes the central requirement for obtaining solutions of “proper” coordination polymers, i.e., polymers having a constant number of repeating units per individual chain. Tetrachloroethane was found to be an appropriate solvent for this purpose. Solubility of the copper(I) and silver(I) coordination polymers – which are polyelectrolytes – in this rather apolar solvent was achieved by the attachment of two hexyl side chains to each polymer repeating unit. It was thus possible to prove the defect‐free constitution of the obtained coordination polymers and to show their excellent stability in solution with the aid of 1H and 13C NMR spectroscopy. Moreover, formation of coordination polymers of considerable chain lengths is supported by the complete disappearance of end‐group absorptions in the 1H NMR spectra and the results of viscosimetric investigations.
Self‐organization of a liquid crystalline methacrylate‐monofunctionalized crown‐ether compound in low‐shrinkage acrylate mixtures
Authors: Beginn Uwe , Zipp Gabriela , Möller Martin , Johansson Gary , Percec Virgil
Published: April 2003

Crystallization and supramolecular aggregation of 1,4,7,10,13‐pentaoxacyclopentadecane‐2‐ylmethyl 3,4‐bis[4‐(dodecyl‐1‐oxy)benzyloxy]‐5‐(11‐methacryloyloxyundecyl‐1‐oxy)benzoate (1) and its complexes with sodium triflate are described in solutions of the methacrylate monomers. Formation of a gel was observed covering a rather wide concentration range in the pseudo‐binary phase diagram. In the low concentration regime and at low temperatures, gel formation by elongated crystals of 1 was observed. It was demonstrated that the formation of a crystalline network and the shape of the crystals strongly depend on the cooling rate.