bluuebunny/crossref_metadata_2025 huggingface dataset:
Poly(ε‐caprolactone)–Poly(oxyethylene) Multiblock Copolymers Bearing Along the Chain Regularly Spaced Pendant Amino Groups
Authors: Canciello Mariarosaria , Maglio Giovanni , Nese Giuseppe , Palumbo Rosario
Published: April 2007

Poly(ε‐caprolactone) (PCL) macromers ($\overline M _{\rm n} $ = 1.7–3.8 kDa) which contain one Z‐protected NH2 group per chain were synthesized by ring‐opening polymerization of ε‐caprolactone in the presence of Sn(oct)2 using as initiator a diamine prepared by condensation of N‐Boc‐1,6‐hexanediamine and Nα‐Boc‐Nε‐Z‐L‐Lysine. The coupling of these macromers with COCl end‐capped poly(oxyethylene) (PEO), $\overline M _{\rm n} $ = 1.0 kDa, afforded amphiphilic multiblock poly(ether ester)s (PEEs) which have, along the chain, regularly spaced pendant protected amino groups. Deprotection, accomplished without chain degradation, yielded NH2 groups available for further reactions. The molecular structure of macromers and PEEs was investigated by 1H NMR and SEC. DSC and WAXS analyses showed that macromers and copolymers were semicrystalline and their Tm increased with increase in the molecular weight of PCL segments. The inherent viscosity values (0.25–0.30 dL · g−1), together with SEC analysis results, indicated moderate polymerization degrees.

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ATPase‐Coupled Release Control from Polyion Complex Capsules Encapsulating Muscle Proteins
Authors: Sugiura Kousuke , Ohkawa Kousaku , Hirai Toshihiro , Fujii Toshihiro
Published: April 2007

In the present study, a muscle contractile protein complex, actomyosin, has been successfully encapsulated into gellan–chitosan polyion complex (PIC) capsules. The recovery of the myosin‐ATPase activity is approximately 50% and the Mg2+‐ATPase activity is stimulated by the presence of F‐actin, which implies the formation of the actomyosin complex inside the capsule. Furthermore, encapsulation could protect the myosin, F‐actin, and actomyosin inside from hydrolysis by proteases. Two small proteins, myoglobin and cytochrome c, have been used in the release tests. The release of myoglobin is not affected by the ionic strength of the external solution, while the release of cytochrome c increases with increasing ionic strength. The maximal releases are found in the external pH solution close to the isoelectric points of each protein. The Mg2+‐ATP complex itself reduces the release percentages of the small proteins from the PIC capsule. The release amounts further decrease when coexisting with Mg2+‐ATP and the encapsulated actomyosin, which indicates the release regulation by actomyosin. The present study suggests that the ATPase‐coupled sliding motion of the myosin–F‐actin filaments modifies the pore size of the polymer networks in the PIC capsule membranes.

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All‐Dry Synthesis and Coating of Methacrylic Acid Copolymers for Controlled Release
Authors: Lau Kenneth K. S. , Gleason Karen K.
Published: April 2007

Initiated chemical vapor deposition (iCVD) is presented as an all‐dry synthesis and coating method for applying methacrylic acid copolymers as pH‐responsive controlled release layers. iCVD combines the strengths of liquid‐phase chemical synthesis with a precision solvent‐free chemical vapor deposition environment. Copolymers of methacrylic acid and ethyl acrylate were confirmed by a systematic shift in the carbonyl bond stretching mode with a shift in the comonomer ratio within the copolymer and by the ability to apply the Fineman–Ross copolymerization equation to describe copolymerization kinetics. Copolymers of methacrylic acid and ethylene dimethacrylate showed pH‐dependent swelling behavior that was applied to the enteric release of fluorescein and ibuprofen.

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Uniform Biodegradable Hydrogel Microspheres Fabricated by a Surfactant‐Free Electric‐Field‐Assisted Method
Authors: Choy Young Bin , Choi Hyungsoo , Kim Kyekyoon (Kevin)
Published: April 2007

Uniform biodegradable hydrogel microspheres (HMS) with precisely controlled size have been fabricated using an electric‐field‐assisted precision particle fabrication technique. Particle agglomeration was prevented by charging the hydrogel drops and allowing Coulomb repulsion to separate them. As a result, surfactant‐free and non‐toxic particle fabrication was possible and the resulting microspheres were most suitable for biomedical and food‐related applications. Due to the size uniformity, the present HMS may serve as a convenient yet most accurate vehicle for controlled delivery of therapeutic agents and other active ingredients.

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Ferrocene Branched Chitosan for the Construction of a Reagentless Amperometric Hydrogen Peroxide Biosensor
Authors: Garcia Ariel , Peniche‐Covas Carlos , Chico Belkis , Simpson Benjamin K. , Villalonga Reynaldo
Published: April 2007

Chitosan was chemically branched with ferrocene moieties and further used as a support for the immobilization of horseradish peroxidase on a glassy carbon electrode. The reagentless biosensor device showed a linear amperometric response toward hydrogen peroxide concentrations between 35 × 10−6 M and 2.0 × 10−3 M. The biosensor reached 95% of the steady‐state current in about 20 s and its sensitivity was 28.4 × 10−3 µA · M−1. The enzyme electrode retained 94% of its initial activity after 2 weeks of storage at 4 °C in 50 × 10−3 M sodium phosphate buffer at pH 7.0.

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Macromol. Biosci. 4/2007
Authors: Choy Young Bin , Choi Hyungsoo , Kim Kyekyoon (Kevin)
Published: April 2007

Cover: The picture shows SEM images of uniform and monodisperse microspheres of various biodegradable hydrogel polymers fabricated with a novel method. The present hydrogel microspheres may provide added accuracy and control for the hydrogel microsphere‐mediated delivery of therapeutic agents and other active ingredients. Further details can be found in the article by Y. B. Choy, H. Choi,* and K. (K.) Kim* on page 423.
Macromol. Biosci. 4/2007
Authors: Bulmus Volga , Chan Yannie , Nguyen Quyen , Tran Hong L.
Published: April 2007

Back Cover: The schematic representation and the scanning electron microscope image of poly(hydroxyethyl methacrylate) microgel particles crosslinked with acetal based crosslinkers. Further details can be found in the article by V. Bulmus,* Y. Chan, Q. Nguyen, and H. L. Tran on page 446.
Thermal Behavior of Isotactic Poly(propylene)/Maleated Poly(propylene) Blends
Authors: Vîlcu Catalin , Grigoras Cristian , Vasile Cornelia
Published: April 2007

This paper analyzes the thermal and thermo‐oxidative degradation behavior, phase separation, melting, and crystallization of blends consisting of isotactic poly(propylene) (IPP) and poly(propylene) grafted with maleic anhydride (PP‐g‐MA). It has been established that, depending on the blend composition and crystallization/preparation procedure, the blends of IPP and PP‐g‐MA can either co‐crystallize or evidence phase separation. This conclusion has been attained by comparing the DSC results of crystallization under dynamic and isothermal conditions with X‐ray diffraction results. On the basis of the obtained results, the optimum mixing ratios have been established as 95–85 wt.‐% IPP/5–15 wt.‐% PP‐g‐MA. Thermo‐oxidative behavior has been studied by thermogravimetry and differential thermal analysis.

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Effect of Ultrasonic Dispersion Methods on Thermal and Mechanical Properties of Organoclay Epoxy Nanocomposites
Authors: Dean Katherine , Krstina Julia , Tian Wendy , Varley Russell J.
Published: April 2007

This report highlights the importance of nanocomposite formation and dispersion upon improvements in properties for high performance epoxy based layered silicate nanocomposites. This is achieved through the preparation of epoxy nanocomposites with varying clay concentrations using ultrasonic and solvent based fabrication and standard shear mixing procedures. Ultrasonication (combined with a solvent), in comparison to shear mixing methods, produces superior nanoscale dispersion according to SEM and TEM. As a result of the improvements in nanoscale dispersion, the corresponding improvements in fracture toughness, strength, strain to failure (compressive and flexural) and char stability are presented. TGA shows that while the initial thermal decomposition process is not affected, the stability of the char layer formed during decomposition increases with improved nanoscale dispersion as well as increasing concentration. The effect of moisture upon the dynamic mechanical thermal analysis of the epoxy nanocomposites displays some dependence upon the clay dispersion with a modest increase in plasticisation for the sonicated samples. Overall, this work shows that for a high performance epoxy anhydride resin system, significant improvements in key properties can be achieved at low levels of addition if appropriate sonicated dispersion methods can be utilised.

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The Effects of Different Plasticizers on the Properties of Thermoplastic Starch as Solid Polymer Electrolytes
Authors: Ma Xiaofei , Yu Jiugao , He Kang , Wang Ning
Published: April 2007

Plasticizers with amide groups (urea and formamide) and polyols (glycerol, glucose, and sorbitol) were used to prepare thermoplastic starch (TPS) containing NaCl salt as solid polymer electrolytes (SPE). Fourier Transform infrared (FT‐IR) spectroscopy revealed that both plasticizers and Na+ could form the interaction with starch, and plasticizers containing amide groups had stronger hydrogen bond‐forming abilities with starch than polyols. These interactions prevented starch molecules from crystallizing again, indicated by X‐ray diffraction (XRD). Scanning electron microscope (SEM) showed that starch granules were in a molten state and a continuous phase of TPS was formed. Among TPS as SPE, formamide‐plasticized TPS (FPTPS) had the largest elongation at break and lowest tensile stress. The conductance of TPS was sensitive to water. TPS plasticized by solid plasticizers had the higher sensitivity of the conductance to water contents at the low water contents (<0.1). The relationship of the conductance and water contents was in agreement with the second‐order polynomial correlation when water contents were below 0.45. FPTPS had the best conductance as a whole. At the medium water content (0.2), the conductance of FPTPS containing NaCl was about 10−3 S · cm−1.

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A High‐Throughput, Controllable, and Environmentally Benign Fabrication Process of Thermoplastic Nanofibers
Authors: Wang Dong , Sun Gang , Chiou Bor‐Sen
Published: April 2007

Continuous and uniform yarns of thermoplastic nanofibers were prepared via direct melt extrusion of immiscible blends of thermoplastic polymers with CAB and subsequent extraction removal of CAB. Ratios of thermoplastic/sacrificial polymers, melt viscosity, and interfacial tensions affect the formation of nanofibers. Dominating sacrificing polymer content in the blends and low interfacial tensions between thermoplastic polymer and CAB are two key factors. This fabrication process possesses features of high productivity, versatility of thermoplastics, controllability, and environment friendliness in manufacturing thermoplastic nanofibers.

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Preparation and Properties of Natural Sand Particles Reinforced Epoxy Composites
Authors: Sui Gang , Jana Soumen , Salehi‐khojin Amin , Neema Sanjay , Zhong Wei‐Hong , Chen Hui , Huo Qun
Published: April 2007

An epoxy composite using Cancun natural hydrophobic sand particle as filler material was fabricated in this study. Three point bending tests demonstrated an enhancement of 7.5 and 8.7% in flexural strength and flexural modulus, respectively, of epoxy composite containing 1 wt.‐% sand particles without any chemical treatment involved, compared to the pristine epoxy. Scanning electron microscopy (SEM) studies revealed that the fracture toughness of the epoxy matrix was enhanced owing to the presence of sand particles in an epoxy/sand composite. Through dynamic mechanical analysis (DMA) and thermal mechanical analysis (TMA) methods, it was found that the storage modulus (E′), glass transition temperature (Tg) and dimensional stability of the sand particles/epoxy composites were increased compared to the pristine epoxy. The friction behavior of epoxy/sand system reflected that the microstructure of epoxy composites was steady. These experimental results suggest that Cancun sand, as a freshly found natural micron porous material, may find promising applications in composite materials.

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Macromol. Mater. Eng. 4/2007
Authors: Wang Dong , Sun Gang , Chiou Bor‐Sen
Published: April 2007

Cover: The pictures on the cover show the novel fabrication of thermoplastics nanofibers in the form of continuous yarns. (a) Dispersion of thermoplastics in CAB matrix into micelles, (b) Deformation and elongation of micelles into ellipsoids, (c) Elongation and coalescence of ellipsoids, (d) CAB/Thermoplastics composite fibers, (e) Thermoplastic nanofibers. Further details can be found in the article by D. Wang, G. Sun,* and B.‐S. Chiou on page 407.
Distinct distribution of autosomal dominant spinocerebellar ataxia in the Mexican population
Authors: Alonso Elisa , Martínez‐Ruano Leticia , De Biase Irene , Mader Christopher , Ochoa Adriana , Yescas Petra , Gutiérrez Roxana , White Misti , Ruano Luís , Fragoso‐Benítez Marcela , Ashizawa Tetsuo , Bidichandani Sanjay I. , Rasmussen Astrid
Published: April 2007

Dominant ataxias show wide geographic variation. We analyzed 108 dominant families and 123 sporadic ataxia patients from Mexico for mutations causing SCA1–3, 6–8, 10, 12, 17 and DRPLA. Only 18.5% of dominant families remained undiagnosed; SCA2 accounted for half (45.4%), followed by SCA10 (13.9%), SCA3 (12%), SCA7 (7.4%), and SCA17 (2.8%). None had SCA1, 6, 8, 12 or DRPLA. Among sporadic cases, 6 had SCA2 (4.9%), and 2 had SCA17 (1.6%). In the SCA2 patients we identified 6 individuals with the rare (CAG)33allele, 2 of whom showed early onset ataxia. The distribution of dominant ataxia mutations in Mexicans is distinct from other populations. © 2007 Movement Disorder Society
Myocardial sympathetic degeneration correlates with clinical phenotype of Parkinson's disease
Authors: Spiegel Jörg , Hellwig Dirk , Farmakis Georgios , Jost Wolfgang H. , Samnick Samuel , Fassbender Klaus , Kirsch Carl‐Martin , Dillmann Ulrich
Published: April 2007

In idiopathic Parkinson's disease (PD), different clinical subtypes are distinguished due to predominant motor symptoms: a tremor‐dominant type (TDT), an akinetic rigid type (ART), and a mixed type (MT). We compared myocardial sympathetic innervation, measured by MIBG scintigraphy, in different subtypes of PD at early and advanced stages of PD. We applied MIBG scintigraphy in 102 patients with PD. About 57 patients were at Hoehn and Yahr (H&Y) stage 1, 22 at H&Y stage 2, and 23 at H&Y stages 3 and 4. For quantification of myocardial MIBG uptake, the heart‐to‐mediastinum (H/M) count‐ratio was calculated. At all H&Y stages, myocardial MIBG uptake was significantly higher in TDT patients than in ART or MT patients (P < 0.05; ANOVA). Furthermore, at each H&Y stage, myocardial MIBG uptake correlated significantly with severity of hypokinesia (P < 0.05; Spearman's correlation) and rigidity (P < 0.05), but not with severity of resting or postural tremor. The significant correlation between myocardial sympathetic degeneration and severity of hypokinesia and rigidity suggests that myocardial sympathetic degeneration and hypokinetic‐rigid symptoms develop in a closely coupled manner in early as well as advanced PD. No such correlation can be found between myocardial sympathetic degeneration and parkinsonian tremor. © 2007 Movement Disorder Society
Effect of coffee Melanoidin on human hepatoma HepG2 cells. Protection against oxidative stress induced by tert‐butylhydroperoxide
Authors: Goya Luis , Delgado‐Andrade Cristina , Rufián‐Henares José A. , Bravo Laura , Morales Francisco J.
Published: April 2007

Soluble high‐molecular weight fraction (named melanoidin) from coffee brew was isolated by ultrafiltration, subsequently digested by simulating a gastric plus pancreatic digestive condition and partly characterized by CZE, gel‐filtration and browning. The objective of the present study was to investigate the potential protective effect of the coffee melanoidin submitted to gastrointestinal digestion on cell viability (lactate dehydrogenase leakage) and redox status of cultured human hepatoma HepG2 cells submitted to oxidative stress induced by tert‐butylhydroperoxide (t‐BOOH). Concentration of reduced glutathione (GSH) and malondialdehyde (MDA), generation of reactive oxygen species (ROS) and activity of antioxidant enzymes glutathione peroxidase (GPx) and reductase (GR) were used as markers of cellular oxidative status. Pretreatment of cultured HepG2 cells with 0.5–10 μg/mL digested coffee melanoidin (DCM) for 2 or 20 h completely prevented the increase in cell damage and GR and partly prevented the decrease of GSH and the increase of MDA and GPx evoked by t‐BOOH in HepG2 cells. In contrast, increased ROS generation induced by t‐BOOH was not prevented when cells were pretreated with DCM. The results show that treatment of HepG2 cells with concentrations of DCM within the expected physiological range confers the cells a significant protection against an oxidative insult.
Birth of cloned miniature pigs derived from somatic cell nuclear transferred embryos activated by ultrasound treatment
Authors: Miyoshi Kazuchika , Inoue Sumiko , Himaki Takehiro , Mikawa Satoshi , Yoshida Mitsutoshi
Published: April 2007

The present study was carried out to determine (1) the optimal duty cycle of ultrasound for activation of pig oocytes and cloned embryos derived from miniature pig fetal fibroblasts and (2) whether cloned embryos can develop to term following activation by ultrasound stimulation. When oocytes were exposed to ultrasound with 20% or 30% duty cycle, the blastocyst formation rates were significantly (P < 0.05) higher than that of oocytes exposed to ultrasound with 10% duty cycle. In contrast, the blastocyst formation rate of cloned embryos decreased as the duty cycle of ultrasound increased; the value of embryos exposed to ultrasound with 10% duty cycle was significantly (P < 0.05) higher than that of embryos exposed to ultrasound with 50% duty cycle. When cloned embryos exposed to ultrasound with 10% duty cycle were transferred into the oviducts of two recipient gilts to assess their development in vivo, the pregnancy of one of the gilts was maintained to term and two piglets were delivered via Cesarean section. The results of the present study showed that (1) although the duty cycle of ultrasound affects in vitro development after activation of both pig oocytes and miniature pig cloned embryos, the optimal duty cycle is different between them and (2) miniature pig cloned embryos have the ability to develop into piglets after activation by ultrasound stimulation. Mol. Reprod. Dev. 74: 1568–1574, 2007. © 2007 Wiley‐Liss, Inc.
Pathogenesis of apical periodontal cysts: guidelines for diagnosis in palaeopathology
Authors: Dias G. J. , Prasad K. , Santos A. L.
Published: April 2007

Apical periodontal cysts are benign lesions developing in relation to the apices of non‐vital teeth due to inflammatory response from the infective pulp. These are epithelium‐lined bony cavities containing fluid. Despite being widely reported in medical/dental literature, this common condition is poorly diagnosed and documented in the archaeological literature. We aim to clarify the correct terminology, demonstrate bony manifestations at different stages of pathogenesis of chronic periapical dental lesions into granuloma and apical periodontal cysts, and to describe diagnostic criteria which would provide practical guidelines for the diagnosis of these conditions.

Three identified skulls from the International Exchange Collection, housed in the Anthropological Museum at the University of Coimbra, are used to identify the progression of this condition from a small periapical granuloma to a large apical periodontal cyst with expansion of alveolar and facial bones. The pathogenesis of this condition is described, together with its surgical management in the early 20th century in Portugal, which is the period in which these individuals lived. Confusion resulting from the different terminologies can be avoided if the term periapical granuloma is used to define apical bony lesions smaller than 3 mm at their maximum intra‐bony diameter, and the term apical periodontal cysts for the larger lesions. We recommend that these terminologies and parameters be used as a standard in future studies. This will make inter‐observer and inter‐population comparisons more accurate. Copyright © 2007 John Wiley & Sons, Ltd.
Polyisobutylene‐block‐polyoxyethylene‐block‐polyisobutylene as stabilizer in aqueous polymerization of styrene, methyl methacrylate, and vinyl acetate
Authors: Piirma Irja , Sar Bidulata
Published: April 2007

Amphipathic triblock copolymers of polyisobutylene‐block‐polyoxy‐ethylene‐block‐polyisobutylene were synthesized by a coupling technique. Seven triblock copolymers were prepared by varying their hydrophobic and hydrophilic chain lengths. The stabilizing effectiveness of these polymeric surfactants was studied as a function of structural variations of the block copolymers in aqueous polymerizations of styrene, methyl methacrylate, and vinyl acetate.
Preparation and biochemical and biomedical applications of new monosized polymer particles
Authors: Ugelstad John , Mørk Preben C. , Schmid Ruth , Ellingsen Turid , Berge Arvid
Published: April 2007

The method for preparation of monodisperse polymer particles by activated swelling was first presented 12 years ago. Since then the principle of activated swelling has resulted in procedures for the production of a number of monodisperse systems with particle sizes and compositions that were unattainable by previous methods. It has also formed the basis for several new applications of polymer particles. A short review of the basic theoretical principles which have been used in the development of the new processes is given. Methods for preparation of monosized polymer particles are described, and the most important biochemical and biomedical applications of various types of particles, including magnetic particles, are given.
Crosslinking kinetics in emulsion polymerization
Authors: Tobita Hidetaka , Hamielec Archie E.
Published: April 2007

Network formation in free‐radical polymerization is investigated both from experimental and theoretical points of view. In a bulk free‐radical crosslinking copolymerization, the radical concentration increases significantly due to a decrease in the bimolecular termination rate. Some fraction of radicals is trapped during the course of network formation, and the reactivity of the radicals in liquid state is completely different from that in solid state (trapped radicals) in terms of both propagation and termination.

In emulsion crosslinking polymerization, the crosslinking density tends to be fairly high even from the start of the polymerization. The crosslinking density development is substantially different from that in bulk and solution polymerizations, in which the crosslinking density increases with time, at least in the earlier stages of polymerization. Due to the elastic contribution of free energy change, the monomer concentration in the polymer particles is lower than for linear emulsion polymerizations as long as the monomer droplets exist, resulting in an enhanced tendency toward crosslinking reactions.
Control of network structure in emulsion crosslinking copolymerization
Authors: Tobita Hidetaka , Hamielec Archie E.
Published: April 2007

A kinetic model for network structure development during crosslinking copolymerization of vinyl and divinyl monomer is proposed. The model calculations suggest that polymer networks synthesized by free‐radical copolymerization are, in general, inhomogeneous at least on a microscopic scale. By application of the same kinetic parameters as those for bulk polymerizations, it was found that the crosslinking density of the polymers formed in the earlier stages of polymerization is very high in emulsion polymerizations and polymer networks tend to be highly heterogeneous. Homogeneous networks cannot be formed even under Flory's simplifying assumptions for vinyl/divinyl copolymerization in emulsion polymerizations. The present kinetic model can be used to find semi‐batch policies to control the network structure, and semi‐batch policies were used to illustrate the synthesis of homogeneous polymer networks.
Monodisperse ellipsoidal polystyrene latex particles: Preparation and characterisation
Authors: Ho C. C. , Ottewill R. H. , Keller A. , Odell J. A.
Published: April 2007

An improved version of a novel method first employed by Nagy & Keller for the preparation of monodisperse ellipsoidal polystyrene latex particles is described. The method involves embedding monodisperse spherical polystyrene latex particles as starting material in a deformable polymer matrix such as poly(vinyl alcohol) and deforming these mechanically to various predetermined macroscopic draw ratios to give ellipsoids of various axial ratios. Ellipsoids with lengths ranging from about 350 to 12250nm were prepared. Stable aqueous dispersions of these were recovered and characterised with respect to particle size and axial ratio distributions and surface morphology using electron microscopy. Axial ratios ranging from 2.0 to 5.65 were obtained for the resulting ellipsoids. Various factors influencing the monodispersity of the resulting ellipsoids in the preparation method are discussed.
Triboelectric charge control of polymer microspheres by surface modification using heterocoagulation
Authors: Shiozaki M. , Tokuno T.
Published: April 2007

A new technique to control the triboelectric charge (TEC) of polymer microspheres is proposed. Polymer microspheres (PMs) were prepared by three‐component suspension copolymerization of styrene (S), 2‐ethylhexyl methacrylate (EHMA) and dimethylaminoethyl methacrylate (DM). Emulsion particles (EPs) for surface modification were prepared by emulsifier‐free three‐component emulsion copolymerization of S, EHMA and sodium styrene sulfonate (NaSS). PMs were covered with EPs by a process similar to the ‘stepwise heterocoagulation technique’ (Okubo, M., He, Y. & Ichikawa, K., Colloid Polym. Sci., 269 (1991) 125). The value of TEC of modified microspheres varied from ‐ 30 μC/g to ‐ 60 μC/g with increasing NaSS content of EPs from 3wt% to 6wt%, though unmodified particles had small values of TEC. This fact suggests that the surface modification used can lead to the preparation of particles having a desired TEC.
Dielectric spectroscopic characterization of a weak‐acid polystyrene colloid
Authors: Su Lao Sou , Jayasuriya Sunil , Fitch Robert M.
Published: April 2007

A commercially available aqueous polystyrene colloid with surface ‐COOH groups was purified by exhaustive dialysis. This was then investigated for dielectric frequency response in the low frequency domain (0.01‐100 Hz), as a function of pH, ionic strength and the chemical nature of the counterions in the electrical double layer. In previous work on strong‐acid (sulfonate) colloids it had been shown that a plot of the imaginary part of the complex impedance as a function of the real part gave semicircles whose radii were a direct function of the surface charge density. In this work, surface charge is a function of pH. The degree of counterion binding was a function of hydrated ion size, as determined from an analysis of titration data and ionic strength of the continuous phase, which in turn was determined from the phase angle and the characteristic relaxation frequency. Dielectric spectroscopy is thus a powerful non‐invasive tool for quantitative analysis of the properties of the electrical double layer in these systems.
Fluorescence analysis for thermo‐sensitive hydrogel microspheres
Authors: Fujimoto K. , Nakajima Y. , Kashiwabara M. , Kawaguchi H.
Published: April 2007

Poly(N‐isopropylacrylamide) (PNIPAM) hydrogel microspheres were prepared by precipitation polymerization above the polymer's lower critical solution temperature (LCST) in water. The hydrodynamic size of PNIPAM microspheres exhibited a thermo‐sensitive change around the LCST. In order to obtain information about the interface of the hydrogels, contact angle measurement, protein adsorption, and fluorescence analysis were performed. Contact angle measurement and protein adsorption showed a gradual change around the LCST similar to the change of the hydrodynamic size. However, fluorescence study exhibited a sharp change at the LCST. In addition, a quenching experiment was employed to elucidate the location of the fluorescent probes. In the PNIPAM latex, the probes were located where they were less quenchable as compared to the PNIPAM solution. It seems probable that the probes can penetrate into the crosslinked PNIPAM hydrogel and might reflect the inner environment of the hydrogel. The effect of salt on thermo‐sensitive behaviour was also detected by fluorescence analysis. On the other hand, the hydrogel microsphere prepared from poly(acryloyl pyrrolidine) (PAPr) showed a gradual change in fluorescence with temperature.
Emulsion polymerization and copolymerization in continuous reactor systems
Authors: Poehlein Gary W.
Published: April 2007

Continuous reactors are important for commercial production of latex products and they can be useful tools for fundamental polymerization kinetics studies. Results are presented for four projects: (i) elimination of conversion oscillations in continuous stirred‐tank reactors (CSTR) by use of a tubular prereactor; (ii) use of a seed‐fed CSTR to measure free radical transport from monomer‐swollen latex particles; (iii) development of a continuous process as an alternative to a commercial batch process; and (iv) determination of copolymerization kinetic parameters with a steady‐state CSTR system.
Modification of polyvinyl chloride‐vinyl acetate latex by seed emulsion polymerization of acrylic monomers
Authors: Omi Shinzo , Shiiyama Eisuke , Sakurai Ken'Ichi , Yoshimoto Hiroyuki , Iso Mamoru , Nakano Akira , Nakamura Mamoru
Published: April 2007

Fundamental studies were carried out to modify the thermal properties of polyvinyl chloride (PVC)‐based latices. General features of composite PVC‐vinyl acetate (VAc) copolymer latices synthesized from the seed emulsion polymerization of acrylic monomers are reported, in particular, the observation of particle morphology and the measurements of minimum film formation temperature (MFT) and DSC spectra. Acrylic monomers used as modifiers were methyl methacrylate (MMA), n‐butyl methacrylate (BMA), methyl acrylate (MA), ethyl acrylate (EA), n‐butyl acrylate (nBA), and MMA‐nBA 75:25,50:50 and 25:75 wt%. Styrene whose polymer is incompatible with PVC‐VAc was used as a counterpart of compatible PMMA. Compatibility between seed and modifier polymer and the mode of operation, either batch (flooded and pre‐swollen) or semi‐batch (starved and no swelling), induced morphology differences, and consequently variations of thermal properties.
Castor‐oil‐modified epoxy resins as model systems of rubber‐modified thermosets. 2: Influence of cure conditions on morphologies generated
Authors: Ruseckaite Roxana A. , Hu Lijiang , Riccardi Carmen C. , Williams Roberto J. J.
Published: April 2007

Phase separation during polymerization was studied in a model system consisting of a diepoxide based on the diglycidyl ether of bisphenol A (DGEBA), ethylenediamine (EDA) and variable amounts of castor oil (CO). Different events taking place during cure, i.e. phase separation, gelation and vitrification, are described in temperature versus time transformation diagrams (TTT), and conversion versus temperature phase diagrams. Thevconcentration (P) and average size (D̄) of dispersed‐phase particles followed opposite trends, i.e. one increased while the other decreased, when varying the castor oil concentration and the cure temperature. This is explained by assuming that the competition between nucleation and growth is determined by the viscosity at the cloud point, ηcp. Low values of ηcp favour growth over nucleation while the opposite is observed for conditions leading to high values of ηcp. The greater the conversion range between the cloud point and gelation, the broader the particle‐size distribution.
Castor‐oil‐modified epoxy resins as model systems of rubber‐modified thermosets. 3: Use of nucleating agent to modify the particle‐size distribution
Authors: Ruseckaite Roxana A. , Fasce Diana P. , Williams Roberto J. J.
Published: April 2007

Phase separation during polymerization was produced in a model system consisting of a diepoxide based on the diglycidyl ether of bisphenol A (DGEBA), ethylenediamine (EDA), and a 15% mass fraction of either pure castor oil (CO) or a 95:5 mass ratio of CO and a polyester (PE) based on CO and oxalic acid. PE acted as a nucleating agent, leading to a significant decrease in the concentration of dispersed‐phase particles and the appearance of a fraction of large particles. Unimodal particle‐size distributions turned into bimodal distributions when adding PE, but the total volume fraction of dispersed phase remained constant. The addition of nucleating agents may be useful to develop formulations with optimum particle‐size distributions for toughening purposes.
Drop stabilisation by inorganic solids in suspension polymerisation: Effect of inorganic particle size using a wax model
Authors: Zhiping Wang , Brooks B. W.
Published: April 2007

Inorganic solids can be used for drop stabilisation in suspension polymerisation and, in some cases, the particle size can affect the drop stability significantly. Three theoretical models, each based on different theories for this drop stabilisation by inorganic solids, have been formulated. Experiments have been carried out using a wax model. These experiments were similar to those described previously [Brooks, B. W., Bygate. F. & Lane, A. C,Brit. Polym. J.,20(1988) 19‐24; Brooks, B. W.,Trans. I. Chem. E.,57(1979) 210‐12]. Particulate calcium phosphate, in different sizes, was used as the stabiliser. The theoretical models have been compared with the experimental results and it was found that two of the models bore some resemblance to the experimental results.
Synthesis and characterization of polyamides containing arylene sulfide‐sulfone groups
Authors: Joseph K. Abraham , Srinivasan M.
Published: April 2007

Polyamides containing arylene sulfide as well as arylene sulfide‐sulfone linkages were prepared from bis(4‐phenylthio)dibenzoyl chloride (BPCl), 4,4′‐[sulfonylbis(4‐phenylthio)]dibenzoyl chloride (SPCl) and aromatic diamines both by solution and interfacial polymerization techniques. In the solution polymerization the effect of two different acid acceptors, lithium chloride and triethylamine, on inherent viscosity of the polyamides was studied. The effect of aromatic sulfone ether diamines and conventional aromatic diamines on viscosity and thermal properties of polyamides was also investigated. The polyamides prepared were characterized by IR, 1H NMR, elemental analysis, solution viscosity, thermogravi‐metry, differential scanning calorimetry and X‐ray diffraction. Thermal and physical properties of polyamides prepared from BPCl and SPCl were compared.
Monolayers of amylose ester derivatives
Authors: Itoh Takahiro , Matsumoto Mutsuo , Miyamoto Takeaki , Suzuki Hidematsu
Published: April 2007

Amphiphilic polymers of amylose tri(n‐decanoate) (C10AS) and amylose tri(n‐octadecanoate) (C18AS) were prepared and examined with respect to their ability to form monolayers at the air‐water interface. The surface pressure‐area isotherm of C10AS was found to have a plateau region, indicating a monolayer‐to‐bilayer transition, while the isotherm for C18AS had no such plateau. Transmission electron microscopic observations of the transferred films revealed that C10AS formed a homogeneous monolayer film at a particular point of the π‐A isotherm, while C18AS gave no homogeneous film at any point of the isotherm. These results are different from those derived from the corresponding cellulose esters. The differences in the isotherms and fine structures of the transferred films are discussed in terms of the difference in chemical structure between amylose and cellulose.
Influence of sepiolite on spherulite growth rate in polyvinylidene fluoride‐based polyblends
Authors: Herrero Consuelo R. , Morales Enrique , Acosta Jose Luis
Published: April 2007

This work reports on the effects exerted by polymethylmethacrylate, polystyrene and sepiolite on several factors which affect spherulite growth of polyvinylidene fluoride, such as growth rate, nucleation factor and nucleation density. Interpretation of the data obtained will support the discussion on miscibility of binary polyvinylidene fluoride/polymethylmethacrylate and poly‐vinylidene fluoride/polystyrene, as well as the miscibilizing effect of sepiolite on both systems.
Crosslinking of atactic polypropylene by the system peroxide‐pentaerythritol tetraallyl ether
Authors: Borsig Eberhard , Lazár Milan , Malcherová Elena
Published: April 2007

The influence of the concentration of peroxide (mainly dicumyl peroxide) and pentaerythritol tetraallyl ether as coagent and the effect of temperature on the crosslinking of atactic polypropylene (a‐PP) with molar mass 12 000g/mol were investigated. Using this system, crosslinking of 40mass% of a‐PP at 160°C was obtained. The problems associated with the mechanism for crosslinking of a‐PP are discussed.
Poly(1,5‐hexadiyne) films prepared using rhodium(i) catalysts
Authors: Cataldo Franco
Published: April 2007

Bis(1,5‐cyclooctadiene)dirhodium(I)dichloride and bis(norbornadiene)‐dirhodium(I)dichloride are effective catalysts for polymerization of 1,5‐hexadiyne. The structure of the polymer obtained and its behaviour towards oxidation and oxidizing agents has been elucidated by means of infrared and ultraviolet spectroscopy. It is proposed that polymerization proceeds with formation of a polymer having a five‐membered ring in each of its monomeric units. The polymer is highly conjugated and can be obtained directly during polymerization as film, which has a metallic lustre, is insoluble in common solvents, and shows good resistance to oxidation in air, if sufficiently thick.
Solid state polymerization of bis(trichlorophenoxo) cobalt(ii) complex to give poly(dichlorophenylene oxide)
Authors: Baştürkmen Meray , Işçi Hüseyin , Kisakürek Duygu
Published: April 2007

Synthesis of four‐coordinated (tetrahedral) trichlorophenol cobalt(II) complex with neutral ligand pyridine was achieved from the aqueous solution and its characterization was performed by UV‐visible, IR spectral and CHN analysis. Solid state thermal polymerization of the complex was accomplished first at constant temperature employing different time intervals and secondly at constant decomposition time. The poly(dichlorophenylene oxide)s so synthesized were characterized by IR, 1H NMR and 13C NMR spectral analysis, Tg determination, as well as measurement of molecular weight by a viscometric method.
Sedimentation velocity studies of poly (sodium styrenesulfonate‐co‐2‐ vinylnaphthalene)
Authors: White Brian , Johnson Paley , Guillet James E.
Published: April 2007

Sedimentation velocity measurements have been employed to investigate the molecular conformation of poly(sodium styrenesulfonate‐co‐2‐vinylnaphtha‐lene) (PSSS‐VN) in aqueous solution. Single symmetrical boundaries were observed in the molecular weight range of 7‐2‐33‐6 104, indicating that PSSS‐VN exists as a single macromolecular coil and not as an aggregate in aqueous solution. Based on the value of the exponent in the power law which describes the dependence of the weight‐average molar mass on the sedimentation coefficient (S), PSSS‐VN behaves as a Gaussian coil dissolved in a solvent of moderate quality. Solubilization of eight molecules of 9‐methylanthracene within the core of PSSS‐VN produced no detectable change in the value of the sedimentation coefficient.
Influence of two‐step process and of different stoichiometric ratios on morphologies generated in castor oil epoxy resins
Authors: Sanchez Jorge L. , Riccardi Carmen C.
Published: April 2007

Phase separation during polymerization was studied in a model system consisting of a diepoxide based on diglycidyl ether of bisphenol A (DGEBA), variable amounts of ethylenediamine (EDA) and the mass of castor oil (CO) necessary to obtain a mass fraction equal to 0‐15 in a final system where the stoichiometric ratio of amine to epoxy equivalents, r, was equal to 1. A two‐step polymerization process was performed by curing first a system with r = 0‐5, during variable times before phase separation, and then carrying the system to r = 1. Thermodynamic analysis of samples with different r values led to a linear relationship between the Flory‐Huggins interaction parameter and r. The concentration (P) and average size (D̄) of dispersed‐phase particles followed opposite trends, i.e. P increased while D̄ decreased, when either r was increased or the time of curing in the first step of a two‐step process was decreased. This was explained by assuming that the competition between nucleation and growth was determined by the viscosity at the cloud point, ηcp. Low values of ηcp favoured growth over nucleation and led to fewer but larger particles.
Water vapour permeability, diffusion and solubility in latex films
Authors: Richard Joél , Mignaud Catherine , Wong Kenneth
Published: April 2007

Water vapour diffusion D, solubility S and permeability P coefficients have been determined for films obtained from carboxylated styrene‐butadiene (SB) copolymer latexes. The experimental method is water vapour sorption performed in the range 30–60d̀C. Using the small angle neutron scattering (SANS) method and a selective labelling with D2O vapour, it has been shown that water molecules mainly diffuse in the films through the particle‐particle interfaces, which consist of a polar carboxyl‐rich copolymer. It has been shown that the degree of cross‐linking of the particles does not significantly affect the values of D and S. Moreover, the effect of neutralization conditions, regarding both the pH value of the initial latex and the nature of the neutralizing agent, has also been investigated. It has been found that D does not depend on these parameters, whereas S appears to be very sensitive to them. The results have been interpreted on the basis of the structural modifications of the films induced by neutralization. Finally, the hydrophilicity (or hydrophobicity) of the neutralizing agent has been identified as one of the key features for controlling the affinity of the latex film for water vapour and hence its permeability properties.
Submicron particle size and polymerization excess surfactant analysis by capillary hydrodynamic fractionation (CHDF)
Authors: Dos Ramos Jose G. , Silebi Cesar A.
Published: April 2007

The particle size distribution of a blend of two polymer latex monodisperse standards, 86 and 238 nm, has been measured by capillary hydrodynamic fractionation (CHDF). The particle size distributions obtained agreed well with the expected particle diameters. The relative amounts of the two standards in the blends were accurately measured at different blend ratios. The particle size distribution of a parenteral lipid sample was successfully measured. A soluble species was fractionated from latex standards smaller than 100nm. This soluble species appears to be excess surfactant used in the preparation of small size monodisperse latexes. The amount of excess surfactant increases as the particle diameter of the standard decreases.
The role of polyvinyl alcohol in emulsion polymerization
Authors: Yuki Ken , Sato Toshiaki , Maruyama Hitoshi , Yamauchi Junnosuke , Okaya Takuji
Published: April 2007

Emulsion polymerization of styrene (St) and vinyl acetate (VAc) in the presence of conventional polyvinyl alcohol (PVA), PVA modified with a terminal alkyl group or PVA modified with a terminal thiol group (HS‐PVA) was compared. Whereas stable PVAc latexes were obtained, a stable PSt latex was obtained only in the case of HS‐PVA. From the adsorption isotherms of these PVAs on the surface of PVAc and PSt latex particles, as well as the grafting efficiencies of VAc and St onto HS‐PVA in relation to the stability of the polymerization process, the role of PVA in the emulsion polymerization was discussed.
Intramolecularly crosslinked macromolecules—Formation and structure, characterization and particle properties
Authors: Funke Werner , Bauer Harald , Joos Betina , Kaczun Jürgen , Kleiner Birgit , Leibelt Ulrich , Okay Oguz
Published: April 2007

Reactive intramolecularly crosslinked macromolecules (RICM) (reactive microgels) have been synthesized by emulsion copolymerization. Besides 1,4‐divinylbenzene (1,4‐DVB), self‐emulsifying unsaturated polyesters (EUP) were used. In copolymerization of EUP and comonomers the diffusion rate of the latter influences the copolymerization rate of the growing species, if the initiator concentration is high and the water solubility of the difunctional comonomer is low. The compact structure of RICM is indicated by low slopes of log [\eta]/logw. Values of [\eta] of RICM are low and their molar masses high. [\eta] depends on the structure of RICM, e.g. pendent chains and crosslink density. Structures with pendent EUP chains could be confirmed by hydrolytic degradation. RICM may be stabilized electrostatically or sterically. Network chains of RICM from 1,4‐DVB are immobile.
Determination of the distribution of interparticle contact angle in the binary mixture of microgels
Authors: Ma Guang Hui , Fukutomi Takashi
Published: April 2007

The films of the binary mixtures composed of poly(4‐vinylpyridine) (P4VP) and polystyrene (PSt) microgels were prepared by casting the deionized aqueous solutions of mixtures at room temperature. The regularity of the particle arrangement was evaluated from the distribution of interparticle contact angle (ICA) formed by three nearest neighbouring particles by using scanning electron micrographs (SEM). It was found that the particles showed hexagonal closed packing, and formed interesting alternating structures when the diameters of two compositions were almost the same. On the other hand, it was found from the distribution of ICA that the arrangements among the particles of same compositions (among P4VP microgels or among PSt microgels) became more ordered as the ratio of the diameters (large particle to small one) became larger while those among the particles of different compositions (among P4VP and PSt microgels) were relatively ordered and the effect of the ratio of the diameters was not so apparent.
Superlong‐range interactions of colloids
Authors: Yoshino Shigeo
Published: April 2007

Colloid particles have superlong‐range attractive and repulsive forces. The distance between the secondary minimum of the potential energy of the interaction and the surface of the colloid is of the order of several μm and several tens of μm. These interactions clearly appear in the distribution of order‐solution phase coexistence, in gathering particles to the ordered phase and in spontaneous pair formation. A new ‘Dynamic electrical multipole model and resonance effect’ is given. From this model, it is predicted that pairs will form in a shear field even in highly concentrated salt solution. Pair formation was observed after 24 hours as predicted.