bluuebunny/crossref_metadata_2025 huggingface dataset:
Acrylonitrile‐Acrylic Acid Copolymer Membrane Imprinted with Uric Acid for Clinical Uses
Authors: Cristallini Caterina , Ciardelli Gianluca , Barbani Niccoletta , Giusti Paolo
Published: February 2004

Summary: The preparation of new polymeric membranes using molecular imprinting technology for application in blood filtration devices is described. Membranes, based on an acrylic acid‐acrylonitrile copolymer, produced through phase inversion, were modified by introducing specific binding sites for uric acid into their structure. The materials prepared are intended for use to selectively remove uric acid from the blood in the case of increased serum uric acid values associated with different pathologies. The interactions at a molecular level between the membrane forming copolymer and the template were investigated by means of calorimetry, infrared spectroscopy and morphological analysis. The presence of interactions between the template and the copolymer, and a good thermal stability of the imprinted membranes were observed. In addition, the results of rebinding tests on the imprinted membranes indicated a good capacity of molecular recognition for the template and satisfactory selectivity properties towards compounds of similar structure such as theophylline. Membrane permeability values suggest their application as (ultra) haemofiltration devices.

Poly(acrylonitrile‐co‐acrylic acid) membrane.

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Poly(acrylonitrile‐co‐acrylic acid) membrane.
Spherical Molecularly Imprinted Polymers (SMIPs) via a Novel Precipitation Polymerization in the Controlled Delivery of Sulfasalazine
Authors: Puoci F. , Iemma F. , Muzzalupo R. , Spizzirri U. G. , Trombino S. , Cassano R. , Picci N.
Published: February 2004

Summary: Spherical molecularly imprinted polymers (SMIPs) have been prepared via a novel precipitation polymerization using sulfasalazine (prodrug used in the diseases of the colon) as template. The sulfasalazine was incorporated into SMIPs and into a spherical non‐imprinted polymer (control), and then the release rate of the bioactive agent at different pH values was evaluated. Considerable differences in the release characteristics between imprinted and non‐imprinted polymers have been observed. This opens the possibility of the development of drug release systems capable of modulating the release of a specific molecule.

Photomicrography of spherical molecularly imprinted polymers (SMIPs).

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Photomicrography of spherical molecularly imprinted polymers (SMIPs).
Effect of Drug‐loading Methods on Drug Load, Encapsulation Efficiency and Release Properties of Alginate/Poly‐L‐Arginine/Chitosan Ternary Complex Microcapsules
Authors: Wang Shi‐Bin , Chen Ai‐Zheng , Weng Lian‐Jin , Chen Mei‐Ying , Xie Xiao‐Lin
Published: February 2004

Summary: The drug‐loaded alginate/poly‐L‐arginine/chitosan ternary complex microcapsules were prepared by mixing method, absorption method and the combined method of mixing and absorption, respectively. The effect of drug‐loading methods on drug load, the encapsulation efficiency and the release properties of the complex microcapsules were investigated. The results showed that the absorption process is a dominating factor to greatly increase the drug load of Hb into microcapsules. Upon loading Hb into microcapsules by combined method of mixing and absorption, the drug load (19.9%) is up to the maximum value, and the encapsulation efficiency is 93.8%. Moreover, the drug release is a zero‐order kinetics process for the ternary complex microcapsules made by mixing. For the complex microcapsules made by absorption, the drug release is a first‐order kinetics. However, for the complex microcapsules made by combining the mixing and the absorption, the drug release obeys a first‐order kinetics during the first eighteen hours, changing afterwards to a zero‐order kinetics process.

Effect of drug‐loading methods on drug load and encapsulation efficiency of alginate/poly‐L‐arginine/chitosan ternary complex microcapsules.

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Effect of drug‐loading methods on drug load and encapsulation efficiency of alginate/poly‐L‐arginine/chitosan ternary complex microcapsules.
Preparation and Characterization of Biodegradable Microspheres Containing Hepatitis B Surface Antigen
Authors: Zhou Shaobing , Liao Xueyan , Liang Zhenglun , Li Xiaohong , Deng Xianmo , Li Heming
Published: February 2004

Summary: Poly‐DL‐lactide‐poly(ethylene glycol) (PELA) microspheres containing Hepatitis B surface antigen (HBsAg) were elaborated by a solvent extraction method based on the formation of a double water/oil/water (w/o/w) emulsion. Microspheres were characterized in terms of morphology, size and size distribution, encapsulation efficiency, and the efficiency of microsphere formation (EMF). Transmission electron microscopy (TEM) and polyacrylamide gel electrophoresis (PAGE) were used to investigate the structural integrality of HBsAg encapsulated in PELA microspheres. The release profile was investigated by the measurement of antigen present in the release medium at various intervals. The PELA‐10 microspheres displayed the highest antigen encapsulation efficiency (about 80%), and antigen molecules could be stabilized in the PELA‐10 microspheres during the preparation process. It suggested that the PELA microspheres had a great potential as a new polymer adjuvant for HBsAg.

The release of Hepatitis B surface antigen from poly‐DL‐lactide‐poly(ethylene glycol) microspheres.

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The release of Hepatitis B surface antigen from poly‐DL‐lactide‐poly(ethylene glycol) microspheres.
High Activity of Enzymes Immobilized in Colloidal Nanoreactors
Authors: Neumann Thorsten , Haupt Björn , Ballauff Matthias
Published: February 2004

Summary: We present a novel type of nanoreactor suitable for the immobilization of enzymes. The particles used consist of a polystyrene core onto which long chains of poly(acrylic acid) are grafted (“spherical polyelectrolyte brush”). Proteins adsorbed spontaneously onto these particles from aqueous solutions if the ionic strength is low. We immobilized glucoamylase on these particles and showed that this enzyme keeps nearly its full activity. This is shown by analyzing the enzymatic activity in terms of the Michaelis‐Menten kinetics. No leaching out of the enzyme takes place during the reaction and the colloidal stability is not impeded by the adsorbed biomolecules. The data presented here suggest that the principle of immobilizing enzymes on these particles may be of general use.

The Figure shows a schematic representation of the colloidal nanoreactors.

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The Figure shows a schematic representation of the colloidal nanoreactors.
Fabrication of Honeycomb‐Patterned Cellulose Films
Authors: Kasai Wakako , Kondo Tetsuo
Published: February 2004

Summary: This paper reports for the first time on the fabrication of honeycomb‐patterned cellulose films by casting water in oil emulsion of cellulose acetate onto a glass substrate and subsequent deacetylation treatment. The honeycomb pore size could be controlled from 1 to 100 μm under a saturated water vapor condition. Both cellulose and cellulose acetate films with honeycomb‐pattern are expected to be a two‐dimensional model of plant cell walls as well as of micro‐wells for single cell cultivation.

Surface topographic image of a honeycomb‐patterned cellulose film (scalebar: 50 μm).

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Surface topographic image of a honeycomb‐patterned cellulose film (scalebar: 50 μm).
Association of Calcium Phosphate and Fibroblast Growth Factor‐2: a Dynamic Light Scattering Study
Authors: Onuma Kazuo , Kanzaki Noriko , Kobayashi Naoko
Published: February 2004

Summary: The size distributions of fibroblast growth factor‐2 (FGF‐2) in aqueous solutions with neutral pH were investigated with a dynamic light scattering technique. We found that the FGF‐2 was distributed in dimer or trimer form at concentrations of 0.1–1.0 mg · mL−1. An aggregate with a hydrodynamic radius of approximately 90 nm coexisted with this and its proportion increased with a decrease in concentration. At lower concentrations (less than 0.10 mg · mL−1) FGF‐2 aggregates with an average radius of 80–100 nm were dominant and were stable for more than a day. These FGF‐2 solutions were mixed with calcium phosphate solutions to produce a sub‐micron sized compound of FGF‐2 and hydroxyapatite, which could be used as a biological implant that possessed a pharmacological function for bone formation. By utilizing a transformation from amorphous calcium phosphate to hydroxyapatite, FGF‐2 was effectively incorporated into polycrystals of hydroxyapatite.

SEM photograph of a mixture of hydroxyapatite and FGF‐2.

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SEM photograph of a mixture of hydroxyapatite and FGF‐2.
Cover Picture: Macromol. Biosci. 1/2004
Authors: Kasai Wakako , Kondo Tetsuo
Published: February 2004

Cover: This picture shows the 2‐dimensional image and the surface topographic image (inset) of a honeycomb‐patterned cellulose acetate film, obtained by mild alkali‐treatment of the cellulose acetate film without deformation of the structural pattern. The pore size of the honeycomb‐pattern in the cellulose films could be controlled from 1 to 100 μm.

Further details can be found in the Communication by W. Kasai, T. Kondo* on page 17.
Electromechanics of a Chiral Smectic C Elastomer: Measurement of Complex Piezoelectric Constant through Successive Phase Transformations
Authors: Hiraoka Kazuyuki , Stein Peter , Finkelmann Heino
Published: February 2004

Summary: Piezoelectric properties of a chiral smectic liquid crystalline elastomer are investigated by means of dynamic electromechanical measurements. We have confirmed that the piezoelectric constant is fairly large in the chiral smectic C (SmC*) phase. A relaxation of the piezoelectric constant is observed in the frequency dispersion curve of a director orientated elastomer obtained by a uniaxial deformation. The temperature dependence of the relaxation frequency in the smectic phases is nicely fitted to the Vogel‐Fulcher‐Tammann law, because the dynamics observed here is closely related to the glass transition phenomena. A resonance instead of a relaxation is recognized in the case of a biaxial deformed elastomer in which both layer and director are oriented to their preferred directions. In addition, the piezoelectric constant of the biaxially deformed elastomer possessing a macroscopically spontaneous polarization is smaller than that of the uniaxially deformed elastomer with no net spontaneous polarization. We discuss the mechanism of polarization generation in the electromechanical response of the SmC* elastomers, and also consider the emergence of the resonance in the biaxial deformed elastomer.

Geometry of sample deformation.

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Geometry of sample deformation.
Radical Polymerisation of 1H,1H,2H,2H‐perfluoro‐3,5‐alkyldiynol and 1H,1H‐perfluoro‐2,4‐alkyldiynol Acrylates and Methacrylates: A New Family of Fluorinated Polymers
Authors: Estelrich Ana Robert , Ameduri Bruno , López‐Calahorra Francisco
Published: February 2004

Summary: The preparation of a new family of acrylic esters with a perfluorinated chain directly bonded to one or two conjugated triple bonds from 1H,1H,2H,2H‐perfluoro‐3,5‐alkyldiynol and 1H,1H‐perfluoro‐2,4‐alkyldiynol is reported. Their solution homopolymerisation was studied in the presence of a radical initiator and it was found that the polymerisation process bore more similarity to that observed with the analogous hydrocarbonated monomers containing triple bonds rather than that observed with polyfluorinated monomers without any alkyne groups. Furthermore, under the reaction conditions used, the triple bonds remained unchanged as there was no cross‐linking process. The homopolymers obtained were characterised by NMR, infrared spectroscopy and gel permeation chromatography whenever possible.

Structure of new fluorinated homopolymers.

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Structure of new fluorinated homopolymers.
Thermoresponsive Properties of Sugar Sensitive Copolymer of N‐Isopropylacrylamide and 3‐(Acrylamido)phenylboronic Acid
Authors: Shiomori Koichiro , Ivanov Alexander E. , Galaev Igor Yu. , Kawano Yoshinobu , Mattiasson Bo
Published: February 2004

Summary: The copolymer of N‐isopropylacrylamide and 3‐(acrylamido)phenylboronic acid (82:18, $\overline M _{\rm n}$ = 47 000 g · mol−1) was prepared by free radical polymerization. The copolymer showed typical thermal precipitation behavior in aqueous solutions, its precipitation temperature (TP) being increased from 23 to 32 °C by increasing the pH from 6.5 to 9.7, because of ionization of the phenylboronate units. The pKa was evaluated as 8.9 ± 0.1 from the effect of pH on TP. At pH > 9, i.e., in the anionic form of the copolymer, TP was affected by a very low concentration of glucose (5.6 μM, ΔTP = 1–1.5 °C), because of complex formation with a high binding constant. At a higher concentration of polyols (560 μM, pH > 8) the increase of TP was maximal for the copolymer complexes with fructose (7–10 °C) and decreased in the order: fructose > glucose ≈ mannitol > pentaerythritol > galactose > Tris >glycerol. Di‐ and oligosaccharides (lactose, sucrose, and dextran) caused a slight increase of TP at pH 7.5–8.7 while no effect was observed at pH > 9. Isothermal dissolution of the copolymer suspension in water (27 °C, pH 8.5) was possible in the presence of fructose or mannitol but required higher concentrations (1.4–3.6 × 103 μM) as compared to those which enabled the shift of TP in the soluble copolymer. The dissolution rate increased with fructose concentrations.

Effect of pH on TP of poly(NIPAAM‐co‐AAPBA) in the presence of various monosaccharides.

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Effect of pH on TP of poly(NIPAAM‐co‐AAPBA) in the presence of various monosaccharides.
Self‐assemblies Based on Poly(4‐diazonium styrene)
Authors: Yang Zhaohui , Cao Weixiao
Published: February 2004

Summary: A series of self‐assembled photosensitive ultra‐thin films have been fabricated from poly(4‐diazonium styrene) (PDS) via different driving forces, mainly by electrostatic and H‐bonding interaction. Under exposure of UV light, the weak ionic and H‐bonds between the layers of the film will be converted to covalent bonds through a photoreaction. Thus, the stability of the film towards polar solvents is reinforced greatly.

UV‐vis spectra of the PDS‐MPR film with different bilayers.

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UV‐vis spectra of the PDS‐MPR film with different bilayers.
Nitroxide‐Mediated Radical Polymerization with Bisaminooxy Compounds as Initiators – Controlled Biradical Polymerization
Authors: Bothe Marc , Schmidt‐Naake Gudrun
Published: February 2004

Summary: The bisaminooxy compounds Bis‐TEMPO and Bis‐TIPNO derived from 2,2,6,6‐tetramethyl‐piperidine‐1‐oxyl (TEMPO) and 2,2,5‐trimethyl‐4‐phenyl‐3‐azahexane‐3‐oxyl (TIPNO) were applied as “biradical initiators” for the nitroxide‐mediated radical polymerization (NMRP) of styrene and n‐butyl acrylate. It was shown by comparison with analogous alkoxyamines as unimolecular initiators and mixing experiments of mono‐ and biradical species, that in the case of the biradical initiators chain growth occurs at both sides under NMRP conditions. This enables a two‐step synthesis of A‐B‐A‐triblock copolymers. Kinetics and molecular mass development were investigated for the controlled biradical polymerization of styrene at different initiator concentrations, temperatures, and with addition of acetic anhydride as accelerator. For the controlled biradical polymerization of n‐butyl acrylate with Bis‐TIPNO, the effect of added free nitroxide relative to the initiator concentration was studied. The poly(styrene‐block‐n‐butyl acrylate‐block‐styrene) copolymers with higher block length prepared by this method show two glass transition temperatures, which indicates microphase separation of the polymer blocks.

Structure of poly(styrene‐block‐n‐butyl acrylate‐block‐styrene), synthesized by nitroxide‐mediated radical polymerization with Bis‐TIPNO as initiator.

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Structure of poly(styrene‐block‐n‐butyl acrylate‐block‐styrene), synthesized by nitroxide‐mediated radical polymerization with Bis‐TIPNO as initiator.
Cationic Grafting of Oxazolyl Copolymers with 2‐Methyl and 2‐Phenyl Oxazoline
Authors: Cabrera Andrés , Schmidt‐Naake Gudrun
Published: February 2004

Summary: Commercial poly(styrene‐co‐acrylonitrile) (SAN) and poly(butadiene‐co‐acrylonitrile) (NBR) were functionalized with oxazoline groups through a reaction with 1,3‐aminoethylpropanediol (AEPD). Each of the two products, along with a third commercial poly(styrene‐co‐vinyl oxazoline) copolymer, went through a reaction with methyl triflate producing stable oxazolinium salts. The products were subsequently used as macroinitiators for the ring‐opening cationic grafting of 2‐methyl and 2‐phenyl oxazoline to produce poly(N‐acylethylenimine) grafts. The products were characterized by FT‐IR, 1H NMR and elemental analysis. The grafted fraction varied from 10 to 55 wt.‐%. The monomer units grafted onto each oxazolinium pendant group varied from 3 to 23 depending on the oxazoline substitution and concentration. The results show, firstly, that controlled and reproducible levels of poly(N‐acylethylenimine) grafts can be incorporated and, secondly, that since these results are general, they are thus applicable to a wide variety of nitrile‐containing polymers.

Reaction of a nitrile group to form an oxazoline functionality.

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Reaction of a nitrile group to form an oxazoline functionality.
Investigation of Soft Component Mobility in Thermoplastic Elastomers using Homo‐ and Heteronuclear Dipolar Filtered 1H Double Quantum NMR Experiments
Authors: Bertmer Marko , Gasper Lothar , Demco Dan E. , Blümich Bernhard , Litvinov Victor M.
Published: February 2004

Summary: Information about segmental mobility in thermoplastic elastomers was obtained using static 1H double quantum (DQ) NMR experiments in combination with homo‐ and heteronuclear dipolar filters, e.g. 13C editing of 1H DQ buildup curves. Block copolymers of poly(butylene terephthalate) (PBT) as hard blocks and poly(tetramethylene oxide) (PTMO) as soft blocks (PBT‐block‐PTMO) were investigated by varying composition and block length. By simulation of the DQ buildup curves, residual dipolar couplings and with this the average order parameter were deduced for the mobile PTMO blocks which are sensitive to the segmental mobility responsible for the viscoelastic properties of thermoplastic elastomers. A strong correlation exists between residual dipolar coupling and composition. Furthermore, the average order parameter correlates linearly with the amount of PTMO in a PTMO‐rich phase as determined in previous studies. Additionally, 1H transverse magnetization relaxation measurements revealed a direct correlation between the effective T2 relaxation time of the soft domain and the composition of the thermoplastic elastomers.

Correlation of the average order parameter vs. the fraction of PTMO in the PTMO‐rich phase.

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Correlation of the average order parameter vs. the fraction of PTMO in the PTMO‐rich phase.
Synthesis of Telechelic Oligomers via Atom Transfer Radical Polymerization, 1
Authors: Otazaghine Belkacem , David Ghislain , Boutevin Bernard , Robin Jean Jacques , Matyjaszewski Kris
Published: February 2004

Summary: Atom Transfer Radical Polymerization (ATRP) of styrene was carried out at 110 °C using various substituted 2‐bromoisobutyrates as initiators and the homogeneous catalyst CuBr/1,1,4,7,10,10‐hexamethyltriethylenetetramine (HMTETA). Telechelic oligomers were obtained by coupling the bromo terminated polymers using Cu(0)/PMDETA catalyst at 90 °C. The products were characterized by 1H NMR and MALDI‐TOF and some unsaturated polymer chains were observed. They could originate from either disproportionation reaction or dehydrohalogenation of halogen terminated oligomers during MALDI analysis. Using this method, polymers with hydroxy, acid, or ester end groups were synthesized in a range of molecular weights from 1 000 to 13 000 g · mol−1. Coupling efficiency was between 79 and 100%, depending on the structure of the initiator.

Coupling reaction of substituted polystyrenes using Cu(0)/PMDETA system at 90 °C.

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Coupling reaction of substituted polystyrenes using Cu(0)/PMDETA system at 90 °C.
Photosulfonation of Low‐Density Polyethylene Films
Authors: Kaneko Masashi , Sato Hisaya
Published: February 2004

Summary: Photosulfonation of low‐density polyethylene (LDPE) films by UV irradiation in the presence of gaseous sulfur dioxide (SO2) and oxygen (O2) was studied by attenuated total reflectance (ATR) infrared spectroscopy and X‐ray photoelectron spectroscopy (XPS). The ATR and XPS analysis and chemical modification of UV‐irradiated LDPE films demonstrated the generation of CC double bonds and sultones in the reaction. These results indicated the possibility that sulfur trioxide (SO3) was produced during the photosulfonation. New pathways for the SO3 reaction with LDPE films, resulting in the formation of sulfonic acid groups, were proposed.

Overview of the mechanism proposed for the photosulfonation of low‐density polyethylene by SO3 (produced upon UV‐irradiation of gaseous SO2 and O2).

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Overview of the mechanism proposed for the photosulfonation of low‐density polyethylene by SO3 (produced upon UV‐irradiation of gaseous SO2 and O2).
Novel Soluble N‐Phenyl‐Carbazole‐Containing PPVs for Light‐Emitting Devices: Synthesis, Electrochemical, Optical, and Electroluminescent Properties
Authors: Li Hongchao , Zhang Yanguang , Hu Yufeng , Ma Dongge , Wang Lixiang , Jing Xiabin , Wang Fosong
Published: February 2004

Summary: Novel PPV derivatives (PCA8‐PV and PCA8‐MEHPV) containing N‐phenyl‐carbazole units on the backbone were successfully synthesized by the Wittig polycondensation of 3,6‐bisformyl‐N‐(4‐octyloxy‐phenyl)carbazole with the corresponding tributyl phosphonium salts in good yields. The newly formed and dominant trans vinylene double bonds were confirmed by FT‐IR and NMR spectroscopy. The polymers (with $\overline M _{\rm w}$ of 6 289 for PCA8‐PV and 7 387 for PCA8‐MEHPV) were soluble in common organic solvents and displayed high thermal stability (Tgs are 110.7 °C for PCA8‐PV and 92.2 °C for PCA8‐MEHPV, respectively) because of the incorporation of the N‐phenyl‐carbazole units. Cyclic voltammetry investigations (onsets: 0.8 V for PCA8‐PV and 0.7 V for PCA8‐MEHPV) suggested that the polymers possess enhanced hole injection/transport properties, which can be also attributed to the N‐phenyl‐carbazole units on the backbone. Both the single‐layer and the double‐layer light‐emitting diodes (LEDs) that used the polymers as the active layer emitted a greenish‐blue or bluish‐green light (the maximum emissions located 494 nm for PCA8‐PV and 507 nm for PCA8‐MEHPV, respectively). Compared with those of the single‐layer devices, the emission efficiencies of the double‐layer devices, in which an electron‐transporting layer (Alq3) was added, were enhanced by a factor of 10, implying that the better hole‐electron balance is achieved because of the incorporation of the electron‐transporting layer.

The N‐phenyl‐carbazole‐containing polymers synthesized.

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The N‐phenyl‐carbazole‐containing polymers synthesized.
n‐Type Copolymers with Fluorene and 1,3,4‐Heterodiazole Moieties
Authors: Janietz Silvia , Barche Jens , Wedel Armin , Sainova Dessislava
Published: February 2004

Summary: The successful realization of n‐channel field‐effect transistors requires the application of semiconducting polymers with high electron mobility (n‐type). However, reports on n‐type polymers are rather scarce in the literature. Therefore, the development of polymers with suitable electron transport properties is particularly challenging for the synthetic chemistry. Main chain polymers with strong acceptor units, such as 1,3,4‐heterodiazoles, are potential candidates for electron transport materials in electronic devices. The fluorene unit is another ring system with interesting physical and chemical properties, which is often used in rigid‐rod, main chain polymers. The present work introduces the synthesis of organo‐soluble copolymers consisting of alternating fluorene‐, 1,3,4‐heterodiazole, and, in some cases, additional 2,5‐dialkoxyphenylene units in the main chain. The reported synthesis involves modified classical polycondensation as well as the tetrazole route. We demonstrate the possibility of exchanging oxygen in the heteroaromatic ring with sulfur using Lawesson's reagent during the ring closure reaction. An alternative structure of the heterocyclic ring with N‐phenyl in the oxygen position is feasible using the tetrazole synthetic route. The chemical and electrochemical properties of the copolyfluorenes are investigated in detail. Some of the synthesized copolyfluorenes have also been used for the preparation of “electron‐only” devices enabling the calculation of the electron mobilities. Further, an organic field‐effect transistor (OFET) characteristic was shown.

OFET characteristics of the polymer 12b.

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OFET characteristics of the polymer 12b.
Effect of the End‐Positioning of a Lithium Sulfonate Group on the Aggregation and Micellization Behavior ofω‐Lithium Sulfonate Polystyrene‐block‐polyisoprenes
Authors: Sotiriou Kondylia , Pispas Stergios , Hadjichristidis Nikos
Published: February 2004

Summary:ω‐Lithium sulfonate polystyrene‐block‐polyisoprenes were synthesized by anionic polymerization high vacuum techniques and a post‐polymerization reaction with 1,1‐diphenylethylene and 1,3‐propane sultone. The solution properties ofω‐lithium sulfonate block copolymers were studied in a low polarity solvent (CCl4) which is a good solvent for both blocks. The study revealed the formation of aggregates due to the association of the lithium sulfonate groups (SuLi). The mass, size and shape of the aggregates were studied by static and dynamic light scattering and viscometry. The aggregation number decreased as the length of the chain increased and the aggregates showed a behavior similar to that of star polymers. The micellization ofω‐functionalized block copolymers was also studied in a polar selective solvent for polystyrene,N,N‐dimethylacetamide (DMA). Micelles formed from block copolymers containing the sulfonate group at the polyisoprene end exhibited an association number which was about 80% of that of the neutral block copolymer and had a higher critical micelle concentration. The samples having the polar group at the PS end showed a similar behavior.

The structures of the end‐functionalized block copolymers studied.

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The structures of the end‐functionalized block copolymers studied.
Synthesis of New Homopolyester and Copolyesters by Anionic Ring‐opening Polymerization of α,α′,β‐Trisubstituted β‐Lactones
Authors: Barbaud Christel , Faÿ Fabienne , Abdillah Fatoumia , Randriamahefa Solo , Guérin Philippe
Published: February 2004

Summary: Novel polyester and copolyesters have been prepared by anionic ring‐opening polymerization of racemic 4‐alkyloxycarbonyl‐3,3‐dimethyl‐2‐oxetanones that had been synthesized in five steps from diethyl oxalpropionate used as chemical precursor. The anionic polymerizations, realized in bulk or in solution with tetraethylammonium benzoate as initiator, led to a homopolymer and copolymers with high molecular weights and polydispersity indices close to unity. These features can be explained by the presence of two methyl groups on the same carbon atom in the lactone, preventing transfer reactions to the monomer. Preparation of seeds and re‐initiation by addition of fresh monomer confirmed a living process. The hydrolysis of poly[(R,S)‐3,3‐dimethylmalic acid] under physiological conditions yielded (R,S)‐3,3‐dimethylmalic acid. A terpolymer was also prepared for biological studies related to its use as biodegradable materials for tissue regeneration.

Structure of poly[(R,S)‐3,3‐dimethylmalic acid].

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Structure of poly[(R,S)‐3,3‐dimethylmalic acid].
Chromophore‐Functionalized Poly(ether sulfone)s with High Poling Stabilities of the Nonlinear Optical Effect
Authors: Ballet Wim , Picard Isabel , Verbiest Thierry , Persoons André , Samyn Celest
Published: February 2004

Summary: Nonlinear optical (NLO) polymers with high glass transition temperatures were prepared by the functionalization of poly(ether sulfone)s with hydroxyalkyl chromophores via the Mitsunobu reaction. Glass transition temperatures obtained were in the range of 158–212 °C. Thin spin‐coated films of the polymers were corona‐poled and analyzed by second‐harmonic generation measurements; second‐order susceptibility values (d33) up to 181 pm · V−1 were obtained. Poled‐order stability measurements over a period of 1 600 h showed that the percentage of the remaining NLO‐response at 125 °C was 84–96% under nitrogen and 54–76% in air.

Structures of chromophores a–c.

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Structures of chromophores a–c.
A Novel Macroinitiator for the Synthesis of Triblock Copolymers via Atom Transfer Radical Polymerization: Polystyrene‐block‐poly(bisphenol A carbonate)‐block‐polystyrene and Poly(methyl methacrylate)‐block‐poly(bisphenol A carbonate)‐block‐poly(methyl methacrylate)
Authors: Mennicken Martina , Nagelsdiek René , Keul Helmut , Höcker Hartwig
Published: February 2004

Summary: Bis(hydroxy)telechelic bisphenol A polycarbonate (PC) was prepared via melt polycondensation of bisphenol A (BPA) and diphenyl carbonate (DPC) using lanthanum(III) acetylacetonate as a catalyst for transesterification. Subsequently, the polycarbonate was converted to a bifunctional macroinitiator for atom transfer radical polymerization (ATRP) with the reagent, α‐chlorophenylacetyl chloride. The macroinitiator was used for the polymerization of styrene (S) and methyl methacrylate (MMA) to give PS‐block‐PC‐block‐PS and PMMA‐block‐PC‐block‐PMMA triblock copolymers. These block copolymers were characterized by NMR and GPC. When styrene and methyl methacrylate were used in large excess, significant shifts toward high molecular weights were observed with quantitative consumption of the macroinitiator. Several ligands were studied in combination with CuCl as the ATRP catalyst. Kinetic studies reveal the controlled nature of the polymerization reaction for all the ligands used.

Formation of a bifunctional ATRP macroinitiator by esterification of bis(hydroxy)telechelic PC with α‐chlorophenylacetyl chloride.

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Formation of a bifunctional ATRP macroinitiator by esterification of bis(hydroxy)telechelic PC with α‐chlorophenylacetyl chloride.
Molecular Design, Synthesis and Properties of Novel Polyurethanes Containing Tetracyanocyclopropyl Groups as Piezoelectric Chromophores
Authors: Lee Ju‐Yeon , Bang Han‐Bae
Published: February 2004

Summary: 1‐(2′,2′,3′,3′‐Tetracyanocyclopropyl)‐3,4‐di‐2′‐hydroxyethoxybenzene (4) was prepared by the reaction of bromomalononitrile with 3,4‐di‐(2′‐hydroxyethoxy)benzylidenemalononitrile (3). The dipole moment of diol 4, calculated by the ASED‐MO method, was 4.01 D. Diol 4 was condensed with 2,4‐toluenediisocyanate and 3,3′‐dimethoxy‐4,4′‐biphenylenediisocyanate to yield polyurethanes 5 and 6 containing tetracyanocyclopropane functionalities in the side‐group. The resulting polymers 5 and 6 were soluble in common organic solvents and the inherent viscosities were in the range of 0.25–0.30 dL · g−1. Solution‐cast films showed a thermal stability up to 280 °C with glass‐transition temperatures of 163–167 °C. The approximate lengths of aligned piezoelectric chromophores estimated from AFM images of poled polymer films were about 4 nm. Piezoelectric coefficients (d31) of the poled polymer films 5 and 6 were around 2.2–2.4 pC · N−1. These polymers showed good temporal and long‐term thermal stability due to the hydrogen bonding of the urethane linkage.

Structure of one of the obtained polymers.

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Structure of one of the obtained polymers.
Phase Separation of Hydrophilic Monomer/Surfactant Aqueous Solution Studied by a Combined Light Scattering and Interference Approach
Authors: Peng Mao , Yuan Xiaoxue
Published: February 2004

Summary: Polymerization‐induced phase separation behavior of 2‐acryllamido‐2‐methyl‐1‐propanesulfonic acid (AMPS)/sodium dodecylsulfonate (SDS) aqueous solution was investigated by using a combined small angle light scattering (SALS) and laser light interference (LI) system. Compared with the conventional SALS technique that has been widely used in studying the phase separation kinetics and mechanism of multicomponent polymer blends or solution, the present combined SALS and LI system can additionally provide valuable information on polymerization kinetics prior to the onset of phase separation. It was found that the 1 mol · L−1 AMPS aqueous solution in the presence of 0.2 mol · L−1 SDS underwent apparent phase separation when polymerization conversion approached 82%. The phase separation rate is so rapid that it takes only 90 s for scattering intensity to reach the maximum. The early stage phase separation follows the spinodal decomposition (SD) mechanism that can be described by the classic linear theory sponsored by Cahn and Hilliard. At late stage of phase separation, however, an observable shift of characteristic vector qm to larger values take place, which may result from the secondary phase separation in the monomer‐rich phase that leads to a deceased average domain size in sample solution. On the other hand, the integral scattering intensity decreased apparently at late stage of phase separation due to the decreased refractive index difference between the monomer‐rich and polymer‐rich phases as a result of the continued polymerization in the monomer‐rich phase.

Illustration of the combined SALS and LI system.

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Illustration of the combined SALS and LI system.
Propylene Polymerization with Titanium‐Based Ziegler‐Natta Catalysts: Effects of Temperature and Modifiers on Molecular Weight, Molecular Weight Distribution and Stereospecificity
Authors: Kissin Yury V. , Ohnishi Rikuo , Konakazawa Takehito
Published: February 2004

Summary: The article discusses two subjects: (a) temperature effects on the molecular weight, molecular weight distribution and stereoregularity of crystalline fractions of propylene polymers prepared with a supported TiCl4/dibutyl phthalate/MgCl2 – Al(i‐Bu)3 catalyst system, and (b) effects of different modifiers (components of cocatalyst mixtures that either greatly increase or decrease the content of the crystalline material) on the structures of the crystalline and the amorphous fraction. The principal approach of the research is the combination of GPC data for a series of polypropylene samples prepared under different conditions, the data on the distributional stereoregularity of the polymers (from analytical temperature‐rising elution fractionation (Tref) and DSC), and the 13C NMR analysis in order to produce a coherent picture of functioning of active centers. The combination of the experimental results shows that the crystalline fractions of polypropylene are produced by several families of active centers. The centers significantly differ in the average molecular weights of the polymer components they produce and in stereospecificity. The steric control exerted by the active centers of the highest isospecificity slightly decreases with temperature. In contrast, average isotacticity parameters of the crystalline fractions (estimated by NMR) increase with temperature. The latter effect is mainly the outcome of the variation in the relative contents of polymer components of low isotacticity in the crystalline fractions prepared at different temperatures. When a silane is used as a part of a cocatalyst, it not only poisons aspecific centers but poisons the centers of reduced isospecificity as well. This effect results in the increase of the average molecular weight of the crystalline fraction, narrowing of its molecular weight distribution and the increase of its average isotacticity.

Resolution of GPC curves of crystalline fractions into Flory components at 50 °C.

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Resolution of GPC curves of crystalline fractions into Flory components at 50 °C.
Isolated Ethylene Units in Isotactic Polystyrene Chain: Stereocontrol of an Isospecific Post‐Metallocene Titanium Catalyst
Authors: Capacchione Carmine , D'Acunzi Maria , Motta Oriana , Oliva Leone , Proto Antonio , Okuda Jun
Published: February 2004

Summary: Copolymerization of styrene with small amounts of ethylene using the catalyst system dichloro{1,4‐dithiabutanediyl‐2,2′‐bis(4,6‐di‐tert‐butyl‐phenoxy)}titanium/methylaluminoxane results in the unprecedented formation of isotactic polystyrene containing isolated ethylene units. 13C NMR spectroscopic analysis of the copolymer indicates that an “enantiomorphic site” control mechanism for isospecific propagation is operating. DSC measurements also indicate the presence of isolated ethylene units which modify the crystallization behavior of the isotactic polystyrene.

Schematic representation of the copolymerization of styrene with small amounts of ethylene using dichloro{1,4‐dithiabutanediyl‐2,2′‐bis(4,6‐di‐tert‐butyl‐phenoxy)}titanium/methylaluminoxane as catalyst system.

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Schematic representation of the copolymerization of styrene with small amounts of ethylene using dichloro{1,4‐dithiabutanediyl‐2,2′‐bis(4,6‐di‐tert‐butyl‐phenoxy)}titanium/methylaluminoxane as catalyst system.
Non‐Helical Chain Conformations of Isotactic Polymers in the Crystalline State
Authors: Auriemma Finizia , De Rosa Claudio , Corradini Paolo
Published: February 2004

Summary: The vast majority of head‐to‐tail stereoregular crystallizable polymers with an isotactic structure generally assume a helical symmetry in the crystalline state, compatible with the regular repetition along the chain axis of isomorphous isoclined units. There are at least two cases, in which an isotactic polymer chain does not adopt a helical conformation in the crystalline state. One is the crystalline alternating copolymer ethylene‐cis‐butene‐2, (E2B) adopting a (T3G+T3G−)n conformation in the crystalline state, and the second case is isotactic polystyrene (i‐PS) in crystalline gels. In this contribution, the case of E2B and i‐PS is discussed in detail. In the first case, the theoretical provision that an isotactic polymer may show a chain conformation in the crystal state is verified, which corresponds to a regular succession of enantiomorphous, anticlined structural units, instead of a helical repetition of isomorphous isoclined structural units. A new conformational model is presented for the second case, i‐PS chains in the crystalline gels, which could account for all the experimental data concerning this system collected so far in the literature. The limit ordered conformational model of i‐PS chains in crystalline gels proposed is built up of regular helical blocks of chains of opposite handedness alternating along the chain and explains the 0.51 nm meridional reflection in the x‐ray diffraction patterns of stretched i‐PS gels. For the most ordered conformation, it includes 16 monomeric units in a period of 3.06 nm.

Minimum energy conformations for i‐PS chains including (TG)n helical stems of opposite chirality (R, L indicate the right‐ and the left‐handed helical portions, respectively) A: The right‐handed spiral sequence (G−T)n is followed by a left handed one, (TG+)m. B: The left‐handed helical sequence (TG+) is followed by a right‐handed one trough the junction (TT′). C: Possible conformational model for i‐PS chains, corresponding to the sequence of dihedral angles …(G−T)3n(TG+)3j(TT′)(G−T)3m… These types of junctions shown in A and B must alternate along the chain.

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Minimum energy conformations for i‐PS chains including (TG)n helical stems of opposite chirality (R, L indicate the right‐ and the left‐handed helical portions, respectively) A: The right‐handed spiral sequence (G−T)n is followed by a left handed one, (TG+)m. B: The left‐handed helical sequence (TG+) is followed by a right‐handed one trough the junction (TT′). C: Possible conformational model for i‐PS chains, corresponding to the sequence of dihedral angles …(G−T)3n(TG+)3j(TT′)(G−T)3m… These types of junctions shown in A and B must alternate along the chain.
Thermal Behavior and Structural Features of Propene/1‐Pentene Copolymers by Metallocene Catalysts
Authors: Costa Giovanna , Stagnaro Paola , Trefiletti Vincenzo , Sacchi Maria Carmela , Forlini Fabrizio , Alfonso Giovanni Carlo , Tincul Ioan , Wahner Udo M.
Published: February 2004

Summary: Two families of propene/1‐pentene copolymers prepared with different isospecific metallocene catalysts, rac‐Et(Ind)2ZrCl2 and rac‐Me2Si(2‐MeBenz‐[e]Ind)2ZrCl2, containing increasing amounts of 1‐pentene were studied by differential scanning calorimetry (DSC) and wide angle X‐ray diffraction (WAXD). The thermal behavior of the copolymers was correlated with their microstructural features and a relationship between melting temperatures and average length of the isotactic sequences was established. Furthermore, the influence of the comonomer on the degree and type of crystallinity of the copolymers was investigated. Preliminary WAXD results demonstrate that only the α‐modification is present when crystallization takes place under fast cooling conditions, both in crystallized samples as well as in samples that had been aged for several weeks at room temperature.

Melting temperatures of endotherm I vs. the calculated niso values for the two series of propene/1‐pentene copolymers and the corresponding polypropenes.

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Melting temperatures of endotherm I vs. the calculated niso values for the two series of propene/1‐pentene copolymers and the corresponding polypropenes.
Synthesis and Reactivity of (C6F5)3BN‐heterocycle Complexes, 2
Authors: Bonazza Alessandra , Camurati Isabella , Guidotti Simona , Mascellari Nicoletta , Resconi Luigi
Published: February 2004

Summary: The reaction of pyrroles and indoles with perfluoroarylboranes produces 1:1 B‐N complexes that contain highly acidic sp3 methylenes. These complexes are stable and can be used as a proton source for the generation of methylmetallocene cations. Indole is preferred over pyrrole. The 1:1:1 borane:indole:dimethylmetallocene compositions are, in some instances, more active than the 500:1 MAO:metallocene catalysts. In addition, the Ind2ZrMe2/IndoleB(C6F5)3 and related catalyst systems require a lower amount of AlR3 scavenger and are more stable compared to the Ind2ZrMe2/B(C6F5)3 catalyst. Also, Ind2ZrCl2/Al(i‐Bu)3/indoleB(C6F5)3 is an active catalyst system. In ethylene/propylene solution copolymerization catalyzed by Ind2ZrMe2, the most active cocatalysts are indoleB(C6F5)3 and 5‐benzyloxy‐indoleB(C6F5)3.

Formation of the catalyst system [Ind2ZrMe]+[B(indolyl)(C6F5)3]−.

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Formation of the catalyst system [Ind2ZrMe]+[B(indolyl)(C6F5)3]−.
Effect of Solvents on Living Polymerization of Propylene with [t‐BuNSiMe2Flu]TiMe2‐MMAO Catalyst System
Authors: Nishii Kei , Matsumae Takashi , Dare Enock O. , Shiono Takeshi , Ikeda Tomiki
Published: February 2004

Summary: Batchwise polymerization of propylene was conducted at 0 °C in heptane using [tert‐BuNSiMe2Flu]TiMe2 (1) combined with dried methylaluminoxane (MAO) and dried modified methylaluminoxane (MMAO), which were prepared from the toluene solutions of MAO and MMAO by removing the solvent and the free trialkylaluminium. The dried MMAO system quantitatively gave the polymer with higher molecular weight and narrower molecular weight distribution (MWD), ca. 1.3, compared with the dried MAO system. In addition, the polymerization with dried MMAO in toluene, chlorobenzene (CB) and ortho‐dichlorobenzene (o‐DCB), as solvent, also produced polymers quantitatively with MWD of ca. 1.1–1.3. The number‐average molecular weight ($\overline M _{\rm n}$) of the polymers, obtained with these systems, increased linearly against the polymer yield, while the narrow MWD was retained and the number of polymer chains was almost constant. The results of post‐polymerization in heptane and o‐DCB proved that the living polymerization proceeded irrespective of the solvent used. The semi‐batch polymerizations under an atmospheric pressure of propylene indicated that the propagation rate was more than 10 times higher in o‐DCB than in heptane. The 13C NMR analysis of the polymers indicated that the syndiotacticity also depended on the polarity of the solvent and increased in the following order: CB ≤ o‐DCB < toluene < heptane.

A plausible scheme for the interaction between active species and solvents.

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A plausible scheme for the interaction between active species and solvents.
Anion Effects on the Activity and Stereoselectivity in Propene Polymerisations Catalyzed by C2‐Symmetric and “Oscillating” Catalysts
Authors: Rodriguez‐Delgado Antonio , Hannant Mark D. , Lancaster Simon J. , Bochmann Manfred
Published: February 2004

Summary: The influence of perfluoroborate anions on catalyst activity and stereospecificity has been determined for propene polymerisations at 20–60 °C. For C2‐symmetric ansa‐zirconocenes, activities were strongly ligand‐dependent, with systems activated by TIBA/Ph3C+X−, where TIBA = AliBu3, X = {Z[B(C6F5)3]2}, and Z = CN or NH2, giving significantly higher activities than methylaluminoxane under comparable conditions. For high‐activity catalysts at 60 °C, {H2N[B(C6F5)3]2}− proved superior to {CN[B(C6F5)3]2}−, presumably due to the higher thermal stability of the amidoborate. The influence of counteranions on PP stereospecificity for these catalysts is negligible. On the other hand, the conformationally flexible catalyst, (2‐PhInd)2ZrCl2/TIBA/Ph3C+X−, shows not only a strong anion dependence of its activity, but also significant variation in poly(propylene) isotacticity, mainly due to the formation of small fractions of highly isotactic (mmmm > 70%) PP. This effect was particularly pronounced for {CN[B(C6F5)3]2}− and the dianion, {Ni[CNB(C6F5)3]4}2−.

Effect of {CN[B(C6F5)3]2}− and {H2N[B(C6F5)3]2}− on propene polymerisation productivities for zirconocenes 1–8 at 20 °C.

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Effect of {CN[B(C6F5)3]2}− and {H2N[B(C6F5)3]2}− on propene polymerisation productivities for zirconocenes 1–8 at 20 °C.
Syndiotactic‐ and Isotactic Specific Bridged Cyclopentadienyl‐Fluorenyl Based Metallocenes; Structural Features, Catalytic Behavior
Authors: Razavi Abbas , Bellia Vincenzo , De Brauwer Yves , Hortmann Kai , Peters Liliane , Sirole Sabine , Van Belle Stephan , Thewalt Ulf
Published: February 2004

Summary: The stereochemistry of propylene insertion/propagation reactions with a variety of Cs and C1 symmetric, bridged cyclopentadienyl‐fluorenyl ligand containing metallocene catalysts are investigated. It is shown that active species with a local Cs symmetry and enantiotopic coordination positions, in the general contest of the chain migratory insertion, behave syndioselective. However, the bilateral symmetry rule, “central dogma” of syndioselectivity, is not a catholic prerequisite and may be ignored by the Cs systems whenever symmetric “excess” in steric bulk is present. An asymmetric “excess” of steric forces, on the other hand, will perturb the migratory insertion process completely and induce a full tactic inversion in resulting C1 symmetric catalysts. The findings also reveal that C2 symmetry and helicity of homotopic catalysts, conditions thought to be essential for high isoselectivity, can be lifted in light of recent developments in high performance centrally chiral, C1 symmetric enantiotopic catalysts.

Ligand outline, chain orientation, and monomer coordination mode with enantiomorphous active species.

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Ligand outline, chain orientation, and monomer coordination mode with enantiomorphous active species.