bluuebunny/crossref_metadata_2025 huggingface dataset:
Lipase‐catalysed biosynthesis of hexyl butyrate by direct esterification: optimisation by response surface methodology
Authors: Shaw Jei‐Fu , Chang Shu‐Wei , Liao Hui‐Fen , Shieh Chwen‐Jen
Published: October 2003

The ability of immobilised lipase from Rhizomucor miehei (Lipozyme IM‐77) to catalyse the direct esterification of hexanol and butyric acid was investigated. Response surface methodology (RSM) and a four‐factor/five‐level central composite rotatable design (CCRD) were employed to evaluate the effects of synthesis parameters such as reaction time (2–10 h), temperature (25–65 °C), substrate molar ratio of hexanol to butyric acid (1:1–3:1) and enzyme amount (10–50%; 0.24–1.18 BAUN) on the percentage molar conversion of hexyl butyrate by direct esterification. All the parameters had significant effects on the percentage molar conversion. Based on ridge maximum analysis, the optimal conditions for synthesis were: reaction time 8.0 h, temperature 46.9 °C, substrate molar ratio 1:1.2 and enzyme amount 36.4% (0.87 BAUN). The predicted value was 100% and the actual experimental value 98.2% molar conversion. Copyright © 2003 Society of Chemical Industry
Blanching and long‐term freezing affect various bioactive compounds of vegetables in different ways
Authors: Puupponen‐Pimiä Riitta , Häkkinen Suvi T , Aarni Marjukka , Suortti Tapani , Lampi Anna‐Maija , Eurola Merja , Piironen Vieno , Nuutila Anna Maria , Oksman‐Caldentey Kirsi‐Marja
Published: October 2003

An extensive study on the effects of blanching/freezing and long‐term freezer storage on various bioactive compounds of more than 20 commonly used vegetables was performed. Effects were strongly plant species‐dependent. Contents of dietary fibre components either were not affected or increased slightly. Minerals in general were also stable, but some losses of soluble minerals by leaching were observed. Phenolic antioxidants and vitamins were clearly more sensitive. Significant losses (20–30%) of antioxidant activity and total phenolics were detected in many vegetables. A qualitative HPLC profiling method for phenolic antioxidants was developed which proved to be very useful when evaluating the complex behaviour of phenolics during food processing. Up to one‐third of vitamin C contents were lost during blanching, and further slight losses were detected during storage. Folic acid turned out to be very sensitive to blanching, with more than half of the vitamin being lost, but was stable during freezer storage. Carotenoids and sterols were not affected by blanching or freezer storage. The usefulness of the applied screening methods for evaluation of the effects of processing on vegetables is shown. Copyright © 2003 Society of Chemical Industry
Synthesis of Polyphenylene Ether Derivatives: Estimation of Their Dielectric Constants
Authors: Seike Yuusuke , Okude Yuriko , Iwakura Izumi , Chiba Ikuka , Ikeno Taketo , Yamada Tohru
Published: October 2003

A series of poly(2‐alkyl‐6‐phenylphenylene ether)s were prepared by the oxidative polymerization of 2‐alkyl‐6‐phenylphenols. Their dielectric constants were approximately 2.5, whereas it was found that the phenyl group at the 6‐position clearly increased the Q factor of the polymer compared with poly(2,6‐dimethylphenylene ether), PPE. These values were qualitatively predicted from the polarizability and the molar volume calculated by the theoretical analysis of the unit structure at the HF/6‐31G* level.

magnified image
Effect of the Structure of Reactor Poly(propylene‐co‐ethylene) Blends on the Diffusion Coefficient and Activation Energy of a Conventional Antioxidant
Authors: Bertoldo Monica , Ciardelli Francesco , Ferrara Giuseppe , Scoponi Marco
Published: October 2003

The diffusion of a thermal stabilizer, i.e., Irganox 1010, has been studied in three different reactor poly(propylene‐co‐ethylene) blends, namely HecoQ, ExpSS, and Super Soft. The diffusion experiments were carried out by using Roe's method based on a stack of several polymer films where each of them had 60–70 μm thickness. The concentration profile of the stabilizer in every film has been monitored by the absorbance at 282 nm of the recorded UV spectra. Under our experimental conditions, the diffusion of Irganox 1010 for all polymer materials can be correctly interpreted by using Fick's second law resolved under certain boundary conditions. Best‐fitting the experimental data with the equation model also allows calculation of the diffusion coefficient, D, for these polymer materials at 40, 70 and 80 °C. By applying an Arrhenius‐type equation to the calculated D coefficients, an estimation of activation energies of the diffusion process has been achieved. An interpretation, in terms of free volume theory, has been applied to explain the observed variation of D which depends mostly on the amount of amorphous phase of the blends.

Arrhenius plots of ln D versus 1/(RT) for the polymers given in legend.

magnified image

Arrhenius plots of ln D versus 1/(RT) for the polymers given in legend.
Regioselective Synthesis and Structures of (+)‐Catechin‐Aldehyde Polycondensates
Authors: Kim Young‐Jin , Chung Joo Eun , Kurisawa Motoichi , Uyama Hiroshi , Kobayashi Shiro
Published: October 2003

The polymerization of (+)‐catechin with various aldehydes has been performed in the presence of an acid catalyst to produce catechin‐aldehyde polycondensates in high yields. NMR analysis of the product showed that the polymerization regioselectively proceeded to form the polymer linked by an ethyl bridge through C‐6 and C‐8 positions of catechin A ring. Specific rotation and CD measurements of the polymer showed the change of chemical bonding and conformation at near chiral center. The direction of specific rotation was changed from dextrorotatory (+) to levorotatory (−) and a new chiral center was formed on the bridge moiety between the catechin units. Computer simulation suggests the coiled interactions in the polymer by hydrogen bonds between hydroxyl groups and pyranic oxygens.

magnified image
Mechanical and Chemical Analysis of Gelatin‐Based Hydrogel Degradation
Authors: Martínez‐Díaz Gabriel J. , Nelson Darceé , Crone Wendy C. , Kao Weiyuan John
Published: October 2003

The interrelated effect of environmental pH and temperature, gelatin backbone modification and content on the tensile and degradative property of interpenetrating networks (IPNs) containing gelatin and poly(ethylene glycol) diacrylate (PEGdA) was examined. Either increasing the PEGdA content or modifying the gelatin backbone with PEG‐monoacetate ester and/or polyanions decreased the IPN elasticity at ambient room temperature (rt). Under an aqueous environment of varying pH levels and elevated temperature, the degradation of IPN tensile properties was further accelerated. IPNs showed an enhanced elasticity and strength when compared to glutaraldehyde‐fixed gelatin hydrogels. Under an aqueous condition, IPNs showed a wider range of degradation products than hydrogels cross‐linked with glutaraldehyde, as characterized with gel permeation chromatography. The nature of IPN degradation products was independent of the type of gelatin backbone modification. The presence of loaded drug, chlorohexidine digluconate, which was found to interact with PEG‐monoacetate esters of the modified gelatin backbone, resulted in unique degradation products. The tensile and chemical degradation of IPNs is a complex interrelationship of the environmental condition, time, and material modification.

Stress‐strain curves of some IPNs studied here.

magnified image

Stress‐strain curves of some IPNs studied here.
Syntheses and Characterization of Luminescent Polymers Containing Rhenium(I) Pyridinyl‐Carbonyl Complexes
Authors: Bignozzi Carlo A. , Ferri Violetta , Scoponi Marco
Published: October 2003

The syntheses of methacrylate‐ and styrene‐based monomers containing substituted pyridine ligands are reported. The preparation of the corresponding homopolymers has been performed by free radical polymerization by using 2,2′‐azoisobutyronitrile (AIBN) at 60 °C. The high molecular weights, up to 119 000 g · mol−1, and low glass transition (Tg) values (< −43 °C) have been obtained by the copolymerization reaction with butyl acrylate. The free metal homopolymer and copolymer were subsequently metalated by reaction with Re[phen(CO)3(acetone)]+. All polymer materials have been characterized by conventional experimental techniques, such as gel permeation chromatography (GPC), differential scanning calorimetry (DSC), and thermogravimetric analysis (TGA). UV‐Vis and fluorescence spectroscopy have been used to investigate the optical and photophysical properties of the polymers in solid‐state films and in solution. 1H NMR spectra confirmed the structure of the synthesized polymers and contributed to the estimate of the monomer sequences in the copolymer chains. Time‐resolved and emission‐quenching experiments in diluted solutions and on the solid films suggest application of the polymeric materials as oxygen sensors. The morphological aspects of some polymers containing a low amount of rhenium metal complexes have been investigated by scanning electron microscopy (SEM).

One of the Re complex‐containing copolymers synthesized here.

magnified image

One of the Re complex‐containing copolymers synthesized here.
Crystal Growth in Poly(L‐lactide) Thin Film Revealed by in situ Atomic Force Microscopy
Authors: Kikkawa Yoshihiro , Abe Hideki , Fujita Masahiro , Iwata Tadahisa , Inoue Yoshio , Doi Yoshiharu
Published: October 2003

Direct visualization of crystal growth in poly(L‐lactide) thin films was carried out by using a temperature‐controlled atomic force microscopy (AFM). At the initial stage of crystallization, edge‐on lamellar crystals have nucleated and elongated. Subsequently, the edge‐on lamellar crystals showed S‐shaped morphology and changed their orientation from edge‐on manner to flat‐on one. The curvature of edge‐on lamellar crystal has been discussed in terms of inclination and distortion of polymer chains in the crystal. In addition, mechanism on the formation of flat‐on crystal from edge‐on lamellae was proposed as derivative growth on the basis of in situ AFM observation of crystal growth and enzymatic degradation.

magnified image
Functionalisation of Polyolefins: Grafting of Phenol Groups on Olefin/5,7‐Dimethylocta‐1,6‐diene Copolymers
Authors: Dolatkhani Marc , Cramail Henri , Deffieux Alain , Santos Jorge Moniz , Ribeiro Maria Rosário , Bordado João M.
Published: October 2003

The grafting of phenol groups on ethylene/5,7‐dimethylocta‐1,6‐diene copolymers and on ethylene/propylene/5,7‐dimethylocta‐1,6‐diene terpolymers was performed, using two different modification procedures. An indirect route involving hydrochlorination followed by phenol insertion was found to be very effective for the terpolymers, and lead to a grafting phenol rate higher than 75%. However, if the phenol grafting is performed directly on a non‐modified terpolymer, lower rates are obtained. When applied to the copolymers the procedures used were revealed to be less efficient. This fact might be related to the lower solubility of the ethylene/5,7‐dimethylocta‐1,6‐diene copolymers (related to a higher crystallinity and a smaller diene content) when compared with the corresponding terpolymers. Although incomplete, the addition of a hindered phenol to the copolymer gave rise to a polymer that, when compared to polyethylene, presents a higher thermal‐oxidative stability.

Grafting of phenol on a hydrochlorinated ethylene/propylene/5,7‐DMO terpolymer.

magnified image

Grafting of phenol on a hydrochlorinated ethylene/propylene/5,7‐DMO terpolymer.
Enthalpy Relaxation of Layered Silicate‐Epoxy Nanocomposites
Authors: Lu Hongbin , Nutt Steven
Published: October 2003

Using standard and temperature‐modulated differential scanning calorimetry, we have studied the segmental relaxation behavior of montmorillonite‐epoxy nanocomposites. The experimental results showed that the incorporation of clay particles caused the epoxy network to exhibit slower relaxation dynamics compared with the neat epoxy resin. Analysis based on the Tool‐Narayanaswamy‐Moynihan (TNM) model indicated that the nanocomposite systems had greater nonlinearity, higher apparent activation energy, and broader relaxation time distribution than the neat epoxy resin. Further analysis based on the Adam‐Gibbs model indicated that the presence of clay nanoparticles decreased the macroscopic configurational entropy of the epoxy network, and increased the size of the cooperative rearrangement region as well as the fundamental energy barrier. The peculiar relaxation behavior observed in the present experiments was attributed to the confinement effect of nanoparticles on molecular entities during the segmental relaxation. This confinement effect led to a stronger temperature dependence of the relaxation behavior near the glass transition temperature, or greater fragility. An inverse correlation between nonexponentiality and fragility was also observed, which is consistent with the results reported in the literature.

The original MDSC curves: complex heat capacity (C_{\rm P}^*) versus temperature; the inset shows the nonexponentiality parameters (β) for all the samples.

magnified image

The original MDSC curves: complex heat capacity (C_{\rm P}^*) versus temperature; the inset shows the nonexponentiality parameters (β) for all the samples.
Reactivities of ω‐Unsaturated Methacrylate Oligomers toward tert‐Butoxy Radicals: Investigation of the Effect of Degree of Polymerization and Ester Alkyl Group
Authors: Sato Eriko , Zetterlund Per B. , Yamada Bunichiro , Busfield W. Ken , Jenkins Ian D.
Published: October 2003

The reactivities of ω‐unsaturated methacrylate oligomers (RMA‐n; n = 2–5) toward tert‐butoxy radicals (t‐BuO·) as a model of the addition step in addition‐fragmentation chain transfer (AFCT) have been investigated by the nitroxide trapping technique in combination with HPLC and electrospray ionization mass spectrometry. The ratio of the rate coefficients for the addition of ω‐unsaturated methyl methacrylate oligomers (MMA‐n) to t‐BuO· to the β‐fragmentation of t‐BuO· (kadd/kβ), where kβ can be treated as a constant, has been shown to decrease with increasing n due to increased steric hindrance of the α‐substituents. However, the value of kadd/kβ reaches a constant value at n = 3–4, and the greatest extent of suppression of the addition rate compared with MMA is less than a factor of four. Comparison of the values of kadd/kβ for ω‐unsaturated cyclohexyl methacrylate oligomers (CHMA‐n; n = 2 and 3) with MMA‐n revealed that the extent of suppression increased with increasing n without regard to the ester alkyl group. Hydrogen abstraction by t‐BuO· from RMA‐n appears to occur mainly at the ester alkyl groups, and the extent is much greater from CHMA‐n than from MMA‐n.

magnified image
Novel Route to Immobilize Metallocenes within Silica‐Based Supports: Investigation of a Nonhydrolytic Sol–Gel Process
Authors: Dever Cédric , Deffieux Alain , Cramail Henri , Mastroianni Sergio
Published: October 2003

A novel approach to metallocene catalyst heterogenization is presented. Supported metallocenes are obtained by metallation of indenyl‐modified silica produced by a nonhydrolytic sol–gel process. The catalytic activities for ethylene polymerization are rather high for supported systems and may reach 190 grams of polyethylene per gram of catalyst per hour per bar. The influence of the preparation and composition of these supported metallocene systems on ethylene polymerization and polyethylene characteristics are reported.

Possible structure of the indenyl‐modified silicas.

magnified image

Possible structure of the indenyl‐modified silicas.
Preparation of Binary Conductive Polymer Composites with Very Low Percolation Threshold by Latex Blending
Authors: Hu Ji Wen , Li Ming Wei , Zhang Ming Qiu , Xiao Ding Shu , Cheng Gen Shui , Rong Min Zhi
Published: October 2003

The communication reports a way to prepare carbon black (CB)/waterborne polyurethane conducting composites with percolation thresholds as low as 0.2 vol.‐% through conventional latex blending. CB particles in the composites appear segregated in their distribution and are located in the two‐dimensional interstices among the polymer domains. The intimate filler/matrix interaction also improves the tensile strength of the matrix at the CB content corresponding to the electrical percolation threshold.

Room temperature conductivity, σ, and tensile strength as a function of carbon black (CB) concentration of the waterborne‐polyurethane‐based composites prepared by latex blending.

magnified image

Room temperature conductivity, σ, and tensile strength as a function of carbon black (CB) concentration of the waterborne‐polyurethane‐based composites prepared by latex blending.
Regio‐ and Stereochemistry in Propylene Polymerization Catalyzed with Bis(phenoxy‐imine) Zr and Hf Complexes/MAO Systems
Authors: Makio Haruyuki , Tohi Yasushi , Saito Junji , Onda Mitsuhiko , Fujita Terunori
Published: October 2003

End‐group analyses of the oligo‐ and polypropylenes produced with bis(phenoxy‐imine) Zr and Hf complexes with methylaluminoxane (MAO) indicate that the polymerization is initiated by two consecutive 1,2‐insertions and is terminated by a β‐H transfer following a 2,1‐insertion. Our data indicate that chain propagation occurs with prevailing 1,2‐regiochemistry but with considerable regioerrors, and with virtually no stereoselectivity.

The polymerization of propylene mediated by bis(phenoxy‐imine) Zr and Hf complexes with MAO.

magnified image

The polymerization of propylene mediated by bis(phenoxy‐imine) Zr and Hf complexes with MAO.
New Microphase‐Separated Diblock Copolymers Carrying Semifluorinated Side Groups Prepared by ROMP
Authors: Wewerka Karin , Wewerka Alf , Stelzer Franz , Gallot Bernard , Andruzzi Luisa , Galli Giancarlo
Published: October 2003

We prepared new varied diblock copolymers by ring‐opening metathesis polymerization of functionalized norbornenes and cyclooctene in the presence of Schrock‐type initiators, either [Mo(CHCMe2Ph)(N‐2,6‐iPr2Ph)(OCCH3(CF3)2)2] or [Mo(CHCMe2Ph)(N‐2,6‐iPr2Ph)(OC(CH3)3)2]. The block copolymers were microphase separated and presented the individual phases of each polymer block constituent, that were amorphous/amorphous, amorphous/semicrystalline, or semicrystalline/liquid‐crystalline. One example of such a block copolymer is shown.

magnified image
Heterogenization of a Modified Grubbs–Hoveyda Catalyst on a ROMP‐Derived Monolithic Support
Authors: Krause Jens O. , Lubbad Said H. , Nuyken Oskar , Buchmeiser Michael R.
Published: October 2003

A ring‐opening metathesis polymerization‐ (ROMP‐) based monolith was synthesized using a Grubbs' first generation catalyst. The living termini were used for surface grafting of norborn‐5‐ene‐2‐ylmethyl hexafluoroglutarate. The free carboxylic acid groups of the graft polymer were converted into the corresponding silver salt and reacted with the Grubbs–Hoveyda catalyst [RuCl2(CH(2‐iPrO)C6H4)(IMesH2)] (IMesH2 = 1,3‐bis(2,4,6‐trimethylphenyl)‐4,5‐dihydroimidazol‐2‐ylidene) to yield a stable heterogeneous version of this catalyst for use in ring‐closing metathesis (RCM) under continuous flow conditions.

The monolith‐supported Grubbs–Hoveyda catalyst.

magnified image

The monolith‐supported Grubbs–Hoveyda catalyst.
α,ω‐Nitroxide‐Capped Polystyrenes and Poly(butyl acrylate)s as Macroinitiators for the Free‐Radical Polymerization of Methyl Methacrylate
Authors: Bothe Marc , Schmidt‐Naake Gudrun
Published: October 2003

The use of a bisaminooxy compound as initiator for nitroxide‐mediated radical polymerization (NMRP) of styrene or n‐butyl acrylate allows the synthesis of α,ω‐nitroxide‐capped polymers. At high temperatures and with the addition of acetic anhydride, it was found that these polymers could be applied as macroinitiators in the free‐radical polymerization of methyl methacrylate. This enables the synthesis of block copolymers with only minor contents of homopolymer.

The structure of bis‐TIPNO, the bisaminooxy compound used as an initiator for the nitroxide‐mediated radical polymerization of styrene or n‐butyl acrylate.

magnified image

The structure of bis‐TIPNO, the bisaminooxy compound used as an initiator for the nitroxide‐mediated radical polymerization of styrene or n‐butyl acrylate.
Shape persistence as a concept in the design of macromolecular architectures
Authors: Wegner Gerhard
Published: October 2003

Shape persistent macromolecules are objects defined by a time independent overall shape. In most cases such macromolecular objects are characterized by an exterior surface structure and an internal architecture giving coherence to the shape and topology. Shape persistent macromolecules are essential to the development of a polymer based nanotechnology and serve as constitutive units of larger scale architectures either via self‐organization or via processes in which they are assembled to give constructs of nanoscale defined patterns.
Dendritic macromolecules at the interface of nanoscience and nanotechnology
Authors: Fréchet Jean M.J.
Published: October 2003

As a result of their unique architecture and structural as well as functional versatility, dendrimers have generated considerable interest in numerous areas of the physical sciences, engineering, as well as the biological sciences. Both their size ‐ in the 1‐10 nm range ‐ and their globular shape resemble those of many proteins suggesting a host of biomimetic and nanotechnological applications. This brief highlight describes some of our recent work with nascent applications of dendrimers as unimolecular nanoreactors, as nanoscale antennae for energy harvesting and transduction, and as nanosized carriers for diagnostic or therapeutic applications. While implementation of some of these applications may still be distant, the impatient critic might remember that new markets are not created overnight as demonstrated by the slow commercial acceptance of many promising molecules and technologies with development frequently extending decades after their initial discovery.
The influence of hydrogen bonds on the globular structure of HP‐copolymers
Authors: Kriksin Yury , Khalatur Pavel , Khokhlov Alexei
Published: October 2003

We present the results of computer modeling of coil‐globule transition of HP‐copolymer which can form hydrogen bonds between some specific monomer units (hydrogen bond units). Langevin dynamics approach is used for the simulation of coil‐globule transition. We study the influence of the number and distribution of hydrogen bond units along primary sequence on the formation of globular conformations.
Polymer modeling: where has it been and where is it going?
Authors: Rigby David , Eichinger B.E.
Published: October 2003

The development of the area of polymer modeling often referred to as molecular modeling has been reviewed from its early beginnings to the present day. Key forces influencing the development include computational power, algorithmic advances and access to computational resources. The desire to apply modeling techniques to predict the properties of increasingly complex polymer‐containing systems, taken in conjunction with a number of current limitations discussed in this brief review, is expected to define in part some essential future developments.
Polymer concepts in microscopically‐viewed phase transition behavior of crystalline polymers
Authors: Tashiro Kohji , Yoshioka Yayoi , Hama Hisakatsu , Yoshioka Akiko
Published: October 2003

Structural evolution process in crystalline phase transition, isothermal crystallization from melt and solvent‐induced crystallization has been investigated for crystalline polymers on the basis of the time and/or temperature dependence of small‐angle X‐ray scattering (SAXS), wide‐angle X‐ray scattering (WAXS) and infrared/Raman spectra. As examples of isothermal crystallization study, polyethylene and polyoxymethylene were investigated. As for polyoxymethylene, the time‐resolved infrared spectral measurement clarified the appearance of infrared bands characteristic of folded chain crystal (FCC) in the early stage of crystallization process, followed by the detection of infrared bands characteristic of extended chain crystal (ECC) in a later stage. From the time‐resolved SAXS measurement, the stacked lamellar structure of ca. 14 nm long period was detected at first and it was followed by an appearance of the new lamellae in the amorphous region sandwiched between the original lamellae, resulting in the tightly stacked lamellar structure of 7 nm long period. The timing of detecting the SAXS 14 nm peak was almost the same with the observation of infrared FCC bands and the SAXS 7 nm peak with the infrared ECC band. This correspondency allowed us to speculate that some chains bridging several lamellae became fully extended when the new lamellae were formed in the amorphous region sandwiched between the original lamellae. As a result the ECC‐like structural parts were formed, giving the ECC infrared bands. As other examples, the Brill transition of aliphatic nylons and the solvent‐induced crystallization of syndiotactic polystyrene have been reviewed.
Competing short‐range and long‐range interactions in block copolymers: a role of connectivity in polymer science
Authors: Hashimoto T. , Yamauchi K. , Yamaguchi D. , Hasegawa H.
Published: October 2003

We explored a role of connectivity in polymer science by using two model systems: mixtures of two lamella‐forming block copolymers with short and long chain lengths and triblock terpolymers of polyisoprene‐block‐polystyrene‐block‐poly(vinyl methyl ether). These two systems commonly have enriched competitions or interplays of short‐range segmental interactions and long‐range interactions arising from connectivity between block chains and their packing in the respective domains. The enriched interplays were found to give an intriguing cosurfactant effect for the block copolymer mixtures and interesting two‐step microphase transitions for the triblcock terpolymers.
New developments and directions in the area of elastomers and rubberlike elasticity
Authors: Mark J.E.
Published: October 2003

There are number of important developments in the area of elastomeric polymers, including (i) network chains of controlled stiffness, (ii) model elastomers (including dangling‐chain networks), (iii) fluorosiloxane elastomers, (iv) new thermoplastic elastomers, (v) other new elastomers, (v) bimodal network chain‐length distributions, (vi) cross linking in solution or in a state of deformation, and (vii) gel collapse. Interesting elastomeric composites include those with (i) in‐situ generated ceramic‐like particles, (ii) ellipsoidal fillers, (iii) clay‐like layered fillers, (iv) polyhedral oligomeric silsesquioxane (POSS) particles, (v) porous fillers, (vi) elastomeric domains modifying ceramics, and (vii) controlled interfaces. New characterization techniques are being developed for elastomers, and there have been new developments in elasticity theory and in elastomer processing. Some examples of societal aspects of relevance are (i) synthesis of elastomers in environmentally‐friendly solvents, (ii) biosynthesis, (iii), recyclability, (iv) improved adhesion to tire cords, and (v) better barrier properties in anti‐terrorism clothing. Educational topics include curriculum development, and mobile laboratories for elastomer experiments and demonstrations.
Supramolecular aspects of polymer science: a challenge for solid state NMR
Authors: Spiess Hans Wolfgang
Published: October 2003

Recent developments in structural elucidation of supramolecular systems by advanced solid state NMR are described. Special emphasis is placed on hydrogen‐bonded sytems and columnar stacks of aromatic moieties. In imidazole‐based proton conductores spatially separated regions of high and low mobility are identified. In stacks of alkyl‐substituted hexabenzocoronenes maximum charge carrier mobility is observed for crystal‐like stacking of the discs.
Watching macromolecules diffuse at surfaces and under confinement
Authors: Granick Steve , Zhao Jiang , Feng Xie Anne , Bae Sung Chul
Published: October 2003

At the single‐molecule level, this laboratory has been making direct measurements of polymer diffusion at and near surfaces. Parameters of special interest have been to understand (a) the role of molecular weight, N; (b) the role of surface coverage, which may range from dilute to saturated, and (c) the role of the surface, which may range from hard (a silicon wafer) to soft (a supported lipid bilayer), and (d) the use of external fields to direct the transport of small molecules through narrow surface channels that are one macromolecule thick.
Surface mobility in monodisperse polystyrene films
Authors: Kajiyama Tisato , Kawaguchi Daisuke , Tanaka Keiji
Published: October 2003

Surface dynamics in monodisperse polystyrene films was examined by lateral force microscopy in conjunction with dynamic secondary ion mass spectroscopy. Glass transition temperature, Tg, at the surface was markedly lower than the corresponding bulk Tg. Also, it was shown that polymer chains present at the surface could diffuse even at a temperature below the bulk Tg. The surface depth, in which molecular motion was activated, was of the order of 5 nm.
Nanostructures formed by combination of nanotube and polymer chain
Authors: Ito Kohzo , Shimomura Takeshi , Okumura Yasushi
Published: October 2003

We have investigated polymeric supramolecular systems of inclusion complexes between molecular nanotube and polymer chains theoretically and experimentally. This system indicates inclusion‐dissociation behavior much sharper than the inclusion complex between cyclic molecule and small compounds. And we propose some functional supramolecules utilizing the combination of the nanotube or nanoring and polymer chains such as insulated molecular wire and topological gel.
Development of multivalent macromolecular ligands for enhanced detection of biological targets
Authors: Levon Kalle , Yu Bin
Published: October 2003

Macromolecular conjugates enable simultaneous binding of multiple ligands on one biological entity and these polyvalent interactions can be collectively stronger than the corresponding monovalent ligands. We have synthesized macromolecules and conjugated them with a lectin (Helix Pomatia lectin, HPA), and an antibody, both with shown affinities to certain bacteria. The binding ability was studied by flow cytometry and the results showed that the affinity of the biomolecules was greatly enhanced due to the polyvalent effect.
Optical absorption and photoluminescence properties of the PPV nanotubes and nanowires
Authors: Kim Kyungkon , Jeoung Sae Chae , Lee Jinwoo , Hyeon Taeghwan , Jin Jung‐Il
Published: October 2003

We measured optical absorption and time resolved photoluminescence decay properties of the PPV nanotubes and nanowires which were prepared by CVD polymerization using templates. When compared with bulk PPV films, their nano objects showed different optical properties, long photoluminescence decay time and higher photoluminescence efficiencies.
Self‐amplifying sensory materials: energy migration in polymer semiconductors
Authors: Kuroda Kenichi , Swager Timothy M.
Published: October 2003

Signal amplification for ultra‐sensitive detection has been achieved by energy migration in conjugated semiconducting polymeric assemblies. Critical to optimizing this effect is the synthesis of non‐aggregate polymers, the multidimensional directional transport of excited states (excitons), and extending the intrinsic excited state lifetime of conjugated polymers. We developed new water‐soluble non‐ionic conjugated polymers for use in biosensory applications, which can be used to provide highly sensitive/specific ultra‐trace detection that is immune to specificity problems that plauge ionic conjugated polymers.
Macromolecular helicity inversion of poly(phenylacetylene) derivatives induced by various external stimuli
Authors: Maeda Katsuhiro , Morino Kazuhide , Yashima Eiji
Published: October 2003

Unique macromolecular helicity inversion of stereoregular, optically active poly(phenylacetylene) derivatives induced by external achiral and chiral stimuli is briefly reviewed. Stereoregular, cis‐transoidal poly(phenylacetylene)s bearing an optically active substituent, such as (1R,2S)‐norephedrine (poly‐1) and β‐cyclodextrin residues (poly‐2), show an induced circular dichroism (ICD) in the UV‐visible region of the polymer backbone in solution due to a predominantly one‐handed helical conformation of the polymers. However, poly‐1 undergoes a helix‐helix transition upon complexation with chiral acids having an R configuration, and the complexes exhibit a dramatic change in the ICD of poly‐1. Poly‐2 also shows the inversion of macromolecular helicity responding to molecular and chiral recognition events that occurred at the remote cyclodextrin residues from the polymer backbone; the helicity inversion is accompanied by a visible color change. A similar helix‐helix transition of poly((R)‐ or (S)‐(4‐((1‐(1‐naphthyl)ethyl)carbamoyl)phenyl)acetylene) is also briefly described.
Supramolecular polymers: from scientific curiosity to technological reality
Authors: Bosnian A.W. , Brunsveld L. , Folmer B.J.B. , Sijbesma R.P. , Meijer E.W.
Published: October 2003

Supramolecular polymers[1] are introduced as a new approach to come to materials in which the repeating units are not connected by covalent bonds but by specific secondary interactions. Self‐complementary quadruple hydrogen bonded structures with high association constants are presented as easy to synthesize fragments in supramolecular polymers. Some of the many possibilities of equilibrium polymers are discussed, while it is shown that these supramolecular polymers can obtain materials properties normally only obtained with macromolecules.
Status and dreams of photonics polymer for IT
Authors: Koike Yasuhiro , Ishigure Takaaki , Tagaya Akihiro
Published: October 2003

We have proposed a low‐loss, high‐bandwidth and large‐core graded‐index plastic optical fiber (GI POF) in data‐corn, area. The GI POF enables us to eliminate the “modal noise” problem which is observed in medium‐core silica fibers. Therefore, stable high‐speed data transmission can be realized by the GI POF rather than medium‐core silica fibers. Furthermore, advent of perfluorinated (PF) polymer based GI POF network can support higher transmission than silica fibers network because of the small material dispersion of PF polymer compared with silica. In addition, we proposed a “highly scattering optical transmission (HSOT) polymer” and applied it to a light guide plate of a liquid crystal display backlight. The HSOT polymer backlight that was designed using the HSOT designing simulator demonstrated twice the brightness of the conventional taransparent backlight with sufficient color uniformity. Furthermore, we proposed the two types of zero‐birefringence polymers synthesized by the random copolymerization method and the anisotropic molecule dopant method. Both of the polymers exhibited no orientational birefringence for any orientation of polymer chains.
Quantifying supercritical CO2 dilation of poly(vinylidene fluoride) and poly(vinylidene fluoride‐co‐hexafluoro‐propylene) utilizing a linear variable differential transducer: plasticization and melting behavior
Authors: Shenoy Suresh L. , Fujiwara Tomoko , Wynne Kenneth J.
Published: October 2003

Melting behavior of semicrystalline poly(vinylidene fluoride) (PVDF) and poly(vinylidene fluoride‐co‐hexafluoropropylene) is investigated as a function of supercritical CO2 pressure using a Linear Variable Displacement Transformer (LVDT). The melting temperature (Tm) of both polymers is lowered due to supercritical CO2 plasticization. For PVDF, the maximum lowering of Tm (ΔTm/n=23°C) occurs between 483 and 552 bar. The corresponding value for the copolymer is Δ Tm = 26°C at 552 bar. At higher pressures, hydrostatic effects override plasticization and Tm increases for both polymers. By comparing Tm in N2, a noninteracting gas, the opposing effects of plasticization and hydrostatic pressure on Tm are explored.
Impact of microcellular plastics on industrial practice and academic research
Authors: Suh Nam P.
Published: October 2003

Microcellular plastics (MCP) refer to any plastic with tiny bubbles of less than about 50 microns. It is made by subjecting polymers with a large amount of dissolved gas to a thermodynamic instability so as to nucleate a large number of cells instantaneously. MCP has been extruded and injection molded to make various industrial products. The fundamental theory for design of MCP and the processing methods are reviewed. It also discusses the design of equipment, including the die or mold, for MCP processing. The performance of MCP and the advantages of using MCP are presented. Some of industrial applications are also highlighted.
Lignin: its functions and successive flow
Authors: Funaoka Masamitsu
Published: October 2003

Phenolic lignin‐based polymers with structure‐variable function have originally been designed, and a process has been developed for synthesizing them directly from native lignins. The key point of the process is to set up two different solvents, which are immiscible each other, for selective modification and separation of lignin and carbohydrates: hydrophobic solvent for hydrophobic lignin and hydrophilic solvent for hydrophilic carbohydrates. The native lignins, three dimensional network polymers, are subjected to selective modifications at the interface between both phases to give linear type polymers (lignophenols) composed mainly of 1,1‐bis(aryl)propane type units, almost quantitatively. The process provides a new system for successively utilizing lignocellulosics in the molecular level.
The new science of protein mimetics
Authors: Goodman Murray , Cai Weibo , Kinberger Garth A.
Published: October 2003

New chemistries have been developed for de novo protein design. Protein mimetics of different structural and functional properties such as synthetic peptide ligases and Dn symmetrical helical bundles have been reported. The Template‐Assembled Synthetic Protein (TASP) method (as well as the ßMolecular Kit' approach) has also been utilized to prepare protein‐like molecules. Here we report the synthesis of single chain, scaffold (TRIS)‐ and dendrimer‐assembled collagen mimetics composed of the Gly‐Nleu‐Pro sequence where Nleu denotes N‐isobutyl glycine. From the CD spectra and the thermal denaturation studies it can be seen that the collagen mimetics prepared form stable triple helices except the single chain structure. Furthermore, the 162‐residue collagen mimetic dendrimer exhibits enhanced triple helical stability compared to the equivalent scaffold‐terminated structure by an increase in the melting temperature in both H2O and 2:1 ethylene glycol/H2O (4°C and 12°C respectively). The concentration dependence for the melting transition of the collagen mimetic dendrimer was measured from which it was determined that the stabilization effect arises from the intramolecular clustering of the triple helical arrays about the core structure. This ensemble excludes solvent from the interior portion of the array which stabilizes the triple helix cluster.
DNA: beyond the double helix
Authors: Seeman Nadrian C.
Published: October 2003

Reciprocal exchange can be used to produce DNA motifs based on branching at the level of secondary structure. These motifs can be combined by sticky‐ended cohesion to produce a variety of structures. Stick polyhedra and nanomechanical devices have been produced by self‐assembly from motifs based on branched DNA. Periodic arrays with tunable surface features has also been produced; aperiodic arrangements have been used for DNA‐based computation.
Novel biomaterials derived from deoxyribozyme and NAPzyme
Authors: Okumoto Yasuhide , Fujiki Hiroyoshi , Kawakami Junji , Nakashima Shoji , Nakano Shu‐ichi , Ohmichi Tatsuo , Miyoshi Daisuke , Sugimoto Naoki
Published: October 2003

We report the potential of a small Ca2+‐dependent deoxyribozyme as a novel biomaterial to distinguish RNA foldings. It is found that an immobilized deoxyribozyme using avidin‐biotin interaction cleaves the target site within only single‐stranded RNAs. The RNA cleavage reaction is also detected using the deoxyribozyme SPR sensor chip. Furthermore, we develop a novel NAPzyme (nucleic acid peptide deoxyribozyme) with its RNA cleavage function in the absence of divalent metal ions.
Living polymerization of cyclic esters – a route to (bio)degradable polymers. Influence of chain transfer to polymer on livingness
Authors: Penczek Stanislaw , Szymanski Ryszard , Duda Andrzej , Baran Jolanta
Published: October 2003

Polymerization of cyclic esters leads to (bio)degradable polymers of the increasing industrial importance. These polymerizations are of the living nature, although chain transfer to polymer with chain scission may cause deviations from the livingness and introduce structural differences (e.g. in end‐groups), important for physical properties. Two different systems are discussed. In the first one two living macromolecules react one with another and reproduce two living macromolecules, retaining the same reactivities and the same end‐groups. Polymerizations of ϵ‐caprolactone and lactide belong to this category. On the other hand, polymerization of cyclic carbonates proceeds with chain transfer, in which disproportionation of the living chains takes place: from two living macromolecules one “dead” and one “doubly active” can be formed. Conditions of retaining the livingness in terms of the ratios of the rate constants of transfer, reinitiation, and propagation are discussed.
Bioprocessing – no longer a field of dreams
Authors: Sawyer Daniel J.
Published: October 2003

A Field of Dreams was a movie about baseball. The theme was “Build it and They Will Come.” Bioprocessing as an industry has been waiting for someone to step up to the plate and build a large business, based on the technology. The large business was necessary to bring about a revolution to move the Chemical and Plastics Industries towards a new business model, based on more sustainable practices. By providing a unique combination of properties in fiber and packaging applications, PLA was the obvious first choice for companies looking to make bioprocessing a commercial reality.
Microbial degradation of aliphatic polyesters
Authors: Tokiwa Yutaka , Jarerat Amnat
Published: October 2003

Polyester‐degrading ability of actinomycetes obtained from culture collections was investigated by the formation of clear zones on polyester‐emulsified agar plates. Using 41 genera (43 strains) of actinomycetes with phylogenetic affiliations based on 16S rRNA sequences, poly(L‐lactide) (PLA)‐degraders were found to be limited to members of family Pseudonocardiaceae and related genera. On the other hand, poly(β‐hydroxybutyrate) (PHB)‐, polycaprolactone (PCL)‐, and poly(butylene succinate) (PBS)‐degraders were widely distributed in many families.
Trends in industrial polymer research
Authors: Warzelhan Volker , Brandstetter Franz
Published: October 2003

In the past decades a shift in paradigm took place in industrial polymer research for structural materials. Only a few new polymers based on new monomeric building blocks were developed. The main focus is now on tailoring improved “old polymers” with well‐defined structure and properties based on a set of low cost “old” monomers using controlled polymerization mechanisms.
Efficient and tailored polymerization of olefins and styrene by metallocene catalysts
Authors: Kaminsky Walter , Hopf Andreas , Arndt‐Rosenau Michael
Published: October 2003

Different optimised new cs‐symmetric ansa zirconocenes were used for the homopolymerization of propene ‐ activated by methylaluminoxane (MAO) with an Al : Zr molar ratio of 2000. In a series of experiments, the polymerisation temperature was varied in a range from 0 to 60°C. The obtained syndiotactic polypropenes show highly isotacticities up to rrrr pentads of 98% and melting points of 150°C. Stereoselectivities are sensitive to the monomer concentration, showing decreasing syndiotacticities with decreasing propene concentration due to increasing amount of skipped insertion which is demonstrated for the zirconium catalyst.
Polyolefin: changing supply‐demand framework and new technology
Authors: Kitano Kissho , Sugawara Makoto , Matsuura Mitsuyuki
Published: October 2003

Polyolefin industry is now under a remarkable change of international supply‐demand framework and its market is splitting into commodity and high performance products. It is getting more important for a material being harmless and comfortable, while the “life cycle cost”, which includes the cost during use and the recycle cost after use, is regarded as more important to evaluate a material. Those changes are accelerating the inter‐material penetration. Several examples of the material design and production technologies, which responded to the changing market needs and developed new applications of polyolefin, are discussed.
Grafting of polyolefins with maleic anhydride: alchemy or technology?
Authors: van Duin Martin
Published: October 2003

Nowadays, the process of maleic anhydride (MA) grafting and the application of MA‐grafted polyolefins are viewed as mature technologies. The chemistry and technology of modifying apolar polyolefins with the polar and reactive MA either in solution or in the melt were already explored as far back as the 1950s. Commercial applications exploit the improved adhesion of polyolefins to polar materials, both at the macroscopic scale and on the microscopic scale. However, it is hardly recognised that, from a scientific point of view, grafting has still a strong resemblance to alchemy. Both process and application technologies have been developed in a trial and error fashion. Only in the last decade the structure of MA‐grafted polyolefins has been elucidated and attempts to “look” inside the extruder during grafting were only recently successful. The first steps towards the development of sound chemical models are currently made. An overview will be given of the progress made in the various areas mentioned.
Novel copolymers via nitroxide mediated controlled free radical polymerization of vinyl chloride
Authors: Wannemacher Thomas , Braun Dietrich , Pfaendner Rudolf
Published: October 2003

Controlled free radical polymerization (CFRP) of vinyl chloride (VCM) and copolymerization with several comonomers have been studied in aqueous suspension. Therefore di‐tert‐butylnitroxide and three novel nitroxyl radicals were used as mediating agents. Copolymerization of VCM with styrene, partly combined with acrylonitrile, maleic acid anhydride and maleic acid imide as well as methyl methacrylate, n‐butyl methacrylate, butyl acrylate and butadiene have been achieved, demonstrating an efficient route for novel vinyl chloride copolymer architecture.