bluuebunny/crossref_metadata_2025 huggingface dataset:
Visible laser sensitive photopolymers initiated by dye sensitized peroxyester systems
Authors: Yamaoka Tsuguo , Nakamura Yasuo , Koseki Kenichi , Shirosaki Tsutomu
Published: April 2003

The photoinitiating systems comprising of the peroxide, 3,3′,4,4′‐tetrakis(t‐butylperoxycarbonyl)benzophenone and (keto)coumarin dyes were sensitive to visible light to give photopolymers for argon ion laser exposure. The sensitivity of the photopolymer depends on the matrix polymer, and the highest sensitivity to 488 nm light of the argon ion laser, 0.01 mJ/cm2, was obtained with a poly(N‐vinyl‐2‐pyrrolidone) matrix. The sensitization of the peroxide by the dye is due to electron transfer from the excited dye to the peroxide.
Bistable electro‐optical switching for (liquid crystalline polymer)/(low molecular weight liquid crystal) composite system
Authors: Kikuchi Hirotsugu , Moritomi Satoru , Hwang Jenn Chiu , Kajiyama Tisato
Published: April 2003

A series of thin films composed of liquid crystalline polymer (LCP) and low molecular weight liquid crystal (LMWLC) was prepared by a solvent‐casting method. LMWLC is miscible over a whole range of LCP concentrations in isotropic and mesomorphic states. The composite system formed a smectic phase in a LCP weight fraction range above 50%. Reversible and bistable electro‐optical effects based on light scattering were recognized for a smectic phase of the binary composite composed of LCP and LMWLC. A light scattering state appeared in the case of application of an a.c. electric field below a threshold frequency (fc). Furthermore, application of an a.c. field above fc made the transmission light intensity increase. Such phenomena were induced in conjunction with the two types of effect: one is an electric field effect based on the dielectric anisotropy of the mesogenic side chain; and the other is an electric current effect based on the electrohydrodynamic motion of the main chain. In the case of a smectic mesophase, the turbid and transparent states remained unchanged, even though the electric field is removed (memory effect).
Reversible alignment change of nematic liquid crystals by photochromic polymer films
Authors: Kawanishi Yuji , Seki Takahiro , Tamaki Takashi , Ichimura Kunihiro , Ikeda Mitsuhiro , Aoki Koso
Published: April 2003

The alignment of a nematic liquid crystal (LC) was changed reversibly by a photochromic reaction of vinyl‐polymer films bearing azobenzene (Az) chromophores. Photoisomerization of Az in the polymer films proceeded slower than in solution systems with an irreversible nature, due to a limited free volume of polymers and the presence of Az aggregates. Photoregulative Az films were obtained by two procedures: (i) spin‐coating followed by baking processes: and (ii) adsorption from a LC/polymer mixture onto a lecithin‐coated glass surface. Perpendicular alignment, which is achieved both in the surface Az and in the LC layer, allows a parallel interaction between them and enables the photoregulation of the LC alignment.
Anionic living polymerization of 4‐[bis(trimethylsilyl)methyl]styrene and its properties as a resist material
Authors: Kato N. , Nagasaki Y. , Kato M.
Published: April 2003

An anionic polymerization of 4‐[bis(trimethylsilyl)methyl]styrene (BSMS) proceeded homogeneously to give a polymer with a narrow molecular weight distribution (MWD; Mw/Mn = 1.06–1.07) even at 20°C. The relative lower propagating rate owing to the electron‐donating character of the para standing bis(trimethylsilyl)methyl group in BSMS (σ—π hyperconjugation) plays an important role for formation of the poly(BSMS) with a narrow MWD, even at a high polymerization temperature. Poly(BSMS) thus obtained had a high silicon content (24.1 wt%) and a fairly high glass transition temperature (140–150°C). Properties as an electron‐beam resist for poly(BSMS) were investigated. The polymer was found to be a negative‐type resist with a high contrast value (γ = 4.7) and a sensitivity about twice on high as poly(styrene). These facts may be attributable to the high Tg content, the narrow molecular weight distribution, and the characteristic structure of poly(BSMS).
Novel graft copolymers for in vivo targeting of colloidal carriers
Authors: Arshady R. , Illum L. , Davis S. S.
Published: April 2003

A series of novel graft (comb) copolymers composed of a hydrophobic backbone and hydrophilic side chain grafts are described for the in vivo targeting of colloidal carriers. The new copolymers, when coated on nanometer size particles (nanospheres, nanocapsules), substantially reduce the capture of the particles by the reticuloendothelial system (RES) and show potential for targeting to the bone marrow.
Wavelength dependence of laser polymerization of acrylic monomers
Authors: Magan John D. , Blau Werner , Woods John G.
Published: April 2003

Photopolymerization of multifunctional acrylic monomers using excimer and Nd: YAG lasers operated at five different UV wavelengths is reported. The effects of different wavelengths on the surface and bulk cure both in air and under argon are investigated and discussed.
Properties of blends containing two liquid crystalline polymers
Authors: Kenig Samuel , DeMeuse Mark T. , Jaffe Michael
Published: April 2003

Blends containing two, wholly aromatic, naphthalene‐based liquid crystalline polymers (LCPs) are studied. Experimental results show that the viscosities of the resulting blends are lower than the parent LCPs over the entire shear‐rate range investigated. The orientation development following capillary flow demonstrates, that over a defined blend composition range, some blends have higher orientability than the constituent polymers. This is further manifested in the tensile and flexural properties of injection‐molded specimens. A detailed analysis indicates that in the composition range where synergistic effects are observed in orientation development as well as in mechanical properties, only one glass transition temperature is detected. This suggests that “miscibility” is desirable for obtaining maximum properties in these blend systems.
Factors which affect the glass transition and damping capability of polymers
Authors: Sperling L. H. , Fay J. J.
Published: April 2003

The shape of the glass transition plays a critical role in the engineering performance of polymers in sound and vibration damping, as well as other applications. The transition may be affected by fillers, plasticizers, blending, IPN formation, etc. A collection of data, both original and literature, is presented which illustrates how the phenomenon works. Emphasis is placed on the role of the area under the linear loss modulus–temperature curve, which may be evaluated in a fashion similar to other spectroscopic techniques. In addition, the loss area can be significantly affected by morphological factors.
Real‐time X‐ray scattering study during heating of oriented injection‐molded polyethylene
Authors: Rueda D. R. , Ania F. , López‐Cabarcos E. , Baltá‐Calleja F. J. , Zachmann H. G. , Bayer R. K.
Published: April 2003

Highly oriented linear polyethylene was prepared by elongational flow injection molding. The changes in crystal orientation were investigated as a function of temperature by real‐time wide‐angle X‐ray diffraction. Additionally, the influence of molecular weight upon the microstructure and the changes in orientation, during heating near the melting point, and after cooling have been examined. A shish‐kebab structure is inferred for the high molecular weight samples (Mw≥105) from SAXS observations, while for samples with Mw<105 only an oriented lamellar structure is found. Consequently, a higher thermal stability is shown by the higher molecular weight samples. Furthermore, a recovery of crystal orientation on rapid cooling of the samples from the melt is only observed for samples with Mw≥105. The results are discussed in terms of a preferential recrystallization of chain‐folded lamellae, on cooling, onto the shish fibrils which survive at high temperature.
POE incorporation into ionic clusters of ionomer and ion‐conduction behaviors
Authors: Takeoka S. , Sakai H. , Shin H. , Ohta T. , Tsuchida E.
Published: April 2003

Poly(oxyethylene) (POE) was incorporated into the ionic clusters of ionomers, ethylene and methacrylic acid (7.2% neutralized with KOH) copolymer membrane. The changes of properties were studied from SAXS, DSC, IR and ionic conductivity. The IR study suggested that the coordinated structures in ionic clusters of the membrane were destroyed by POE incorporation, and also SAXS suggested that ionic clusters were swollen by POE incorporation. The ionic conductivity, a carrier being K+ in this system, increases from 10−16 S/cm to 10−9 S/cm at 30°C by the incorporation of POE (20.5 wt%). On the other hand, a large amount of POE (63 wt%) could be incorporated into ionomer membrane by the esterification of methacrylic acid groups (93%) with POE. When LiClO4 was added, ionic conduction occurred in the phase‐separated POE domain, which had a low glass transition temperature (−55.2°C), showing an ionic conductivity 2.6 × 10−6 S/cm at 25°C.
Preparation of polymer nanocomposites with “ultrahigh” refractive index
Authors: Weibel M. , Caseri W. , Suter U. W. , Kiess H. , Wehrli E.
Published: April 2003

Nanocomposites of lead sulfide and several polymers, especially poly(ethyleneoxide), were prepared by coprecipitation of lead sulfide and polymer, followed by a drying and pressing procedure. Such nanocomposites consist of ca. 90% w/w (or ca. 50% v/v) lead sulfide, of particle dimensions of 2–40 nm. The refractive index of these materials is on the order of 3 and therefore, to the authors' best knowledge, is the highest reported for any polymer composite.
Design of high‐capacity, reversible polymeric adsorbents for acidic gases
Authors: Andreopoulos A. G. , Economy J.
Published: April 2003

Polyethyleneimine (PEIM) samples crosslinked by a commercial epoxy resin (Epon 828) were prepared, and their adsorption capacity for acidic gases was studied. The swelling and deswelling characteristics of the crosslinked samples were also examined as part of this program. Reactivation of these adsorbents could be carried out by heat, or by a combination of heat and treatment in dilute alkalies.
Polystyrene microspheres with narrow particle size distribution
Authors: Wang Shen‐guo , Zhang Xiao‐qin
Published: April 2003

Crosslinked polystyrene microspheres of a diameter of the order of more than 2 μm and a narrow particle diameter distribution were synthesized by emulsifier‐free emulsion polymerization. The dependence of various parameters such as an electrolyte (NaCl), an initiator (K2S2O8), the phase volume ratio, the reaction temperature and time on the diameter and the particle size distribution has been discussed.
Copolymerization of methacrylic acid alkali metal salts and polyether‐containing monomers in solid polymer electrolytes
Authors: Ohno Hiroyuki , Ito Kaori
Published: April 2003

Copolymerization of methacrylic acid alkali metal salts (MAAM; M = Li, Na, K, Rb or Cs) and oligo(oxyethylene) methacrylate (MEO) was carried out in bulk or in poly(oligo(oxyethylene) methacrylate) (PMEO) at 60°C. The copolymers of MAAM and MEO which were obtained by bulk polymerization showed a cation conductivity of around 1 × 10−7 S/cm at room temperature. On the other hand, the copolymers obtained by radical polymerization in PMEO, showed a higher cation conductivity (10−6–10−5 S/cm). Furthermore, higher cation conductivity was observed for the copolymer systems containing alkali metal cations with a larger ion radius. This tendency was explained by the strength of the bond between alkali metal cation and ether oxygens. The degree of dissociation had little effect on this difference in the conductivity. The effective dissociation of methacrylic salts was enhanced in the copolymer compared to the homopolymer because of the suppression of the adjacent dissociative carboxylic acid groups. Arrhenius plots for ionic conductivity show the migration of ions along with the segmental motion of the polymer matrix.
Durability of polyurethanes elastomers
Authors: Buchman Alisa , Holdengraber Yitzhak , Dodiuk Hanna , Kenig Shmuel
Published: April 2003

The effect of thermal aging on three different elastomeric polyurethane adhesives was studied. Consequently, an attempt was made to predict the polyurethanes' service lifetimes from the changes in tensile properties, hardness of bulk specimens and adhesion strength properties (lap shear and butt joints) of polycarbonate bonded joints. Aging temperatures ranged from ambient to 70 °C (at 50% relative humidity) for durations from 20 days to 18 months.

Experimental results were analyzed according to a kinetic rate theory and using limit values for the various properties. Consequently, service lifetimes were determined and compared to results from actual service life. Predictions of long‐term performance from accelerated tests proved to be reasonable for the properties and materials studied.
Study of the carbon fiber–Poly(Ether–Ether–Ketone) (PEEK) interfaces, 3: influence and properties of interphases
Authors: Nardin M. , Asloun E. M. , Muller F. , Schultz J.
Published: April 2003

The aim of this third part is to analyze the structure and properties of the interfacial region between carbon fibers and PEEK as a function of different thermal conditioning treatments. First, it is shown by means of optical microscopy that the interfacial zone is not different from the bulk matrix when standard cooling conditions are used. On the contrary, a transcrystalline interphase is formed near the carbon fiber surface in systems that have been subjected to isothermal treatments. By comparison with previous results concerning the mechanical properties of the fiber–matrix interface, it appears that the interfacial shear strength decreases in the presence of a transcrystalline interphase or when the crystallization rate of PEEK increases. Moreover, it seems that the “constraint state” of the amorphous phase of PEEK near the fiber surface could also play a role in the interfacial shear strength. Secondly, a method is proposed in order to estimate the elastic modulus of crystalline interphases. It seems that this modulus is strongly dependent on the crystallization rate of the polymer. Finally, the determination of the stress‐free temperature, defined as the temperature at which a longitudinal compressive stress just appears on the carbon fiber during the processing of the composites, is performed by recording the acoustic events corresponding to the fragmentation process in single‐fiber composites. The results confirm that the crystallization rate and the “constraint state” of the amorphous phase of the matrix play an important role in the mechanical behavior of carbon fiber–PEEK interfaces.
Improvements in aluminum adhesion and breakdown voltages of polyvinylidene fluoride films following exposure to gas plasmas
Authors: Mammone Robert J. , Wade William L. , Binder Michael
Published: April 2003

Changes in water wettability, improvement in adhesion of vapor deposited aluminum and increases in dielectric breakdown voltage in thin, 12 micron PVDF films were observed following brief exposure of these films to low‐temperature gas plasmas.
Polyelectrolyte‐like behavior of polyethylene oxide/LiClO4 mixture in chloroform or chloroform/dimethylformamide mixed solvent
Authors: Ohno Hiroyuki , Ito Yasushi , Yamaguchi Natsue
Published: April 2003

Lithium perchlorate (LiClO4) was dissolved in dehydrated chloroform with polyethylene oxides (PEO) having different molecular weights. The mixing ratio of ether oxygen unit (O) of PEO to cation (Li+) was set to 20:1. The solution viscosity of the PEO/LiClO4 mixtures was measured using an Ubbelohde viscometer at 30.0°C. The concentration dependence of the reduced viscosity was analyzed by diluting the initial PEO/LiClO4 mixed solution with pure chloroform to keep the ratio of Oto Li+ constant. The increase in the reduced viscosity for a dilute solution was found in every mixture system, but not in the PEO solution without salt. Similar experiments were also carried out in chloroform/dimethylformamide (DMF) mixed solvent (4:1 by volume). These results were analyzed using the Fuoss equation, which was applied for the analysis of a polyelectrolyte aqueous solution. Linear relations are depicted in the Fuoss plots, suggesting that the PEO/LiClO4 mixture shows polyelectrolyte‐like behavior in chloroform or in chloroform/DMF mixed solvent. This is attributed to the intramolecular electrostatic repulsion of lithium cations which are trapped by the PEO chains through ion–dipole interaction.
Thermal dimensional stability of isotropic polyoxymethylene
Authors: Zahran Rouchdy R. , Abolmagd Abir A.
Published: April 2003

A parametric mapping analysis of the effect of various structural and morphological parameters on the thermal dimensional stability of polyoxymethylene is highlighted. The molecular composites model is found to describe adequately the expansional behavior of isotropic polyoxymethylene. The thermal expansivity is highly sensitive to the level of crystallinity followed by the transverse dimension of the crystallites. The longitudinal dimension of the crystallites, however, is not effective in altering the expansion behavior of isotropic polyoxymethylene. When comparing the model calculations with experimentally published data, an agreement of better than 15% is observed.
Quinone‐modified polymers as electron transfer relay systems in amperometric glucose sensors
Authors: Karan H. I. , Hale P. D. , Lan H. L. , Lee H. S. , Liu L. F. , Skotheim T. A. , Okamoto Y.
Published: April 2003

A polysiloxane and an acrylonitrile–ethylene copolymer with covalently attached p‐hydroquinone/benzoquinone moieties were prepared and tested as electron transfer relay systems in amperometric glucose biosensors. Using experiments involving cyclic voltammetry and stationary potential measurements, it was shown that the polysiloxane relay system can efficiently mediate electron transfer from reduced glucose oxidase to a conventional carbon‐paste electrode. Sensors containing this polymeric relay system and glucose oxidase respond rapidly to low (<0.1 mm) glucose concentrations, with steady state current responses achieved in less than 1 min. The acrylonitrile–ethylene copolymer was found to be less efficient than the polysiloxane system at mediating the electron transfer from reduced glucose oxidase to the electrode. The dependence of the sensor response on the nature of the polymer backbone is discussed.
Resolution of lymphocyte subpopulations derived from rat spleen by polyamine‐graft‐PHEMA copolymer
Authors: Kikuchi Akihiko , Mizutani Shinji , Kataoka Kazunori , Tsuruta Teiji
Published: April 2003

The retention behavior of lymphocyte subpopulations, B cell, T cell and null cell, derived from rat spleen to polyamine‐graft‐poly(2‐hydroxyethyl methacrylate) copolymer (HA) surface was investigated, focusing on the conformational transition of the polyamine side chain as well as the protonation of amino groups in the polyamine grafts. Furthermore, the availability of HA was discussed as a column adsorbent for separation of lymphocyte subpopulations derived from spleen. The conformational transition of polyamine grafts significantly influenced the mode of retention of lymphocyte subpopulations. When polyamine grafts existed in an aggregated conformation (protonatin degree α < 0.5), the retention of lymphocyte subpopulations was decreased in the order B cell> null cell> T cell. On the other hand, when polyamine existed in an extended conformation into the aqueous interior from the matrix interface (α > 0.5), T cell retention became greater than null cell retention, resulting in a decreased B cell> T cell> null cell order. These results indicate that the differential retention of spleen lymphocyte subpopulations is attributed to their differential responses to the change in matrix interface accompanied by the protonation of amino groups. Furthermore, spleen lymphocytes were compared with lymph node lymphocytes in terms of resolution efficacy by an HA copolymer column.
Effect of the incorporation of amino groups in a glucose‐responsive polymer complex having phenylboronic acid moieties
Authors: Kitano Shigeru , Hisamitsu Issei , Koyama Yoshiyuki , Kataoka Kazunori , Okano Teruo , Sakurai Yasuhisa
Published: April 2003

A novel polymer complex system sensitive to glucose was studied as a candidate material for formulating a chemically regulated insulin release system. A ternary copolymer of N‐vinyl‐2‐pyrrolidone (NVP), 3‐acrylamidophenylboronic acid (AAm‐PBA) and N,N‐dimethylaminopropylacrylamide (DMAPAA) (poly(NVP‐co‐PBA‐co‐DMAPAA)) was synthesized by radical copolymerization. The phenylboronic acid group in this copolymer serves as a glucose sensor moiety. Poly(NVP‐co‐PBA‐co‐DMAPAA) was soluble in water in the pH range of 3–12, in sharp contrast to a binary copolymer of NVP and AAm‐PBA (poly(NVP‐co‐PBA)) which showed solubility only under alkaline aqueous conditions, where the boronic acid group is in a tetrahedral ionized form. The protonated amino group in poly(NVP‐co‐PBA‐DMAPAA) contributed to increase the solubility of the polymer under physiological and acidic aqueous conditions. Furthermore, poly(NVP‐co‐PBA‐co‐DMAPAA) formed a stable polymer complex gel with poly(vinyl alcohol) (PVA) in pH 7.4 phosphate buffered solution due to the formation of a covalent linkage between the boronic acid groups in ternary copolymer and diol units in PVA. The release of myoglobin as model protein from the complex gel was increased immediately after the addition of glucose, due to the transition of gel into sol state, indicating the feasibility of this complex gel as a candidate material for a glucose‐responsive delivery system for insulin.
Miscibility of poly(vinyl chloride) with poly(methyl‐co‐hexyl acrylate) and poly(methyl‐co‐2 ethyl hexyl acrylate)
Authors: Jin Byung Suk , Kim Sung Chul
Published: April 2003

The miscibility and phase behavior in blends of PVC with poly(methyl‐co‐hexyl acrylate)[MHA] and poly(methyl‐co‐2 ethyl hexyl acrylate)[MEH] were studied. It was found that PVC is miscible with MHA copolymers having a HA volume fraction from 0.30 to 0.92 and MEH copolymers having an EH volume fraction from 0.30 to 0.83 at 100°C. By applying the mean field theory to the phase diagrams of these blend systems, segmental interaction parameters which represent the binary interaction between different monomer units were estimated. The calculated values reflect the fact that the miscibility window observed for PVC/MHA and PVC/MEH blend systems was attributed to the effect of repulsion between different monomer units within the copolymer. To investigate the effect of specific interaction on the miscibility for these blend systems, an attempt was also made to describe the blend interaction parameter as a function of polar group concentration in the acrylate copolymer. The blend interaction parameter values exhibit a u‐shaped curve as a function of the weight fraction of CO group in the copolymer, and the lowest blend interaction parameter value appears at about 0.24 CO weight fraction.
Novel processable aromatic thermoplastic polyimides: Films, adhesives, moldings, and graphite composites
Authors: Kumar Devendra , Gupta Alka D.
Published: April 2003

Novel hot‐melt type flexible, tough, thermally stable, processable, thermoplastic, aromatic polyimides have been synthesized involving reaction of a keto‐ether containing diamine with hinged aromatic dianhydrides followed by thermal and chemical cyclodehydration. Inherent viscosity in DMAC at 35°C of the synthesized polymers ranged 1.02 to 1.4 dl/g (0.5% solution). The polymers showed a glass transition temperature (Tg) of 250°C to 180°C as determined by differential scanning calorimetry (DSC) and thermomechanical analysis (TMA). Thermogravimetric analysis showed polymer stability up to 510°C, in both air and nitrogen atmospheres. All the polymers have shown good melt‐flow. Films of 1.5–2.8 ml thickness were made and tested for mechanical properties at room temperature, 177°C and 210°C. The developed films are suitable for adhesion of Ti/Ti specimens and showed a lap shear strength of 5575 psi. Melt‐fusion of the polymers gave tough moldings. Graphite cloth composites have been made and tested for mechanical properties.
Blends of poly(carbonate) with poly(styrene) and poly(methylmethacrylate): phase morphology, mechanical, and thermal properties
Authors: Butzbach G. , Wendorff J. H.
Published: April 2003

This paper is concerned with the dependence of mechanical and thermal properties of heterogeneous blends of poly(carbonate) (PC) with poly(methyl‐methacrylate) (PMMA) and with poly(styrene) (PS) on the concentration of the components. PS displays a very weak phase coupling in blends with PC, whereas PMMA is characterized by a strong coupling to PC. Experimental results as well as predictions based on composite theories are reported.

The general finding is that mechanical properties, such as the tensile modulus and the dynamic shear modulus, as well as thermal properties, such as thermal expansion, are (i) only weakly affected by the occurrence of a phase inversion and of a continuous phase morphology, (ii) vary continuously with the concentration of the components, and (iii) are rather insensitive to the strength of the phase coupling. The theoretical predictions on the concentration—property relationship for these properties, based on a self‐consistent approach, agree very well with those observed experimentally. The elongation at break as well as the yield stress, on the other hand, are strongly influenced by the nature of the phase coupling: a discontinuous variation of these properties with the composition is observed for PS/PC blends but not for PMMA/PC blends. The general conclusion is that a set of mechanical and thermal properties of heterogeneous blends can satisfactorily be predicted on the basis of rather simple composite theories.
Properties of block and graft copolymers of polybutadiene with small complexed poly(4‐vinylpyridine) segments
Authors: Janah Hakim , Favier Jean‐Claude , Sigwalt Pierre , Jačovič Mihaïlo S.
Published: April 2003

Various diblocks, triblocks and a graft copolymer of butadiene with 4‐vinylpyridine short blocks have been prepared. They were complexed with ZnCl2 to give ionomer‐like materials. For all copolymers, the Tg of the elastomeric block (−84°C to −91°C) was unchanged by complexation. For all diblocks and triblocks with short blocks (DPn ∼ 3) the storage modulus was only slightly increased by comparison with uncomplexed materials. For the graft copolymer even with short blocks the material is less sensitive to temperature after complexation. For triblocks, when the DPn of the vinylpyridine blocks was high enough (15 units), complexes were associated in multiplets of large size and the elastomeric properties were retained up to 200°C.
The thermal properties of poly(pivalolactone)
Authors: Grebowicz Janusz , Varma‐Nair Manika , Wunderlich Bernhard
Published: April 2003

Quantitative thermal analysis was carried out for poly‐(pivalolactone) (PPVL), including heat capacity determinations from 140 to 550 K. The experimental Cp below the glass transition temperature was fitted to an approximate vibrational spectrum and the ATHAS computation scheme was used to compute the “vibration only” heat capacities from 0.1 to 1000 K. The liquid Cp was derived from an empirical addition scheme and found to agree with the experimental Cp with an RMS of ±2.8% from 240 K to 550 K. A glass transition, Tg, could be detected at 260 K, and the change in heat capacity for 100% amorphous PPVL was calculated to be 38.8 J/(K mol). Above Tg, semicrystalline samples seem to show a rigid amorphous fraction that does not contribute to the increase in heat capacity at Tg. Using the ATHAS recommended heat capacities, the various thermodynamic functions (enthalpy, entropy, and Gibbs function) were derived. The residual entropy at 0 K for the amorphous PPVL was calculated to be 5.2 J/(K mol) per mobile bead, and was comparable to that obtained for a series of linear, aliphatic polyesters analyzed earlier.
Ion transport in copolymers of oligo(oxyethylene) methacrylates with monomers having polar group
Authors: Xu Kang , Wan Guoxiang , Tsuchida Eishun
Published: April 2003

Copolymers of oligo(oxyethylene) methacrylates and a series of polar comonomers, i.e. acrylamide, acrylonitrile and maleic anhydride, were synthesized as media for dual‐ or single‐ion conduction, and correlation between polymer structure and properties was established through detailed studies on polymer morphology, mechanical property and the ion transport process. Polar groups in the polymer chain sequence were found to enhance matrix polarity and to retard oligoether crystallization, as well as to raise chain rigidity. Therefore, both novel dual‐ and single‐ion conduction are realized, with a simultaneous improvement in the mechanical properties of polymer materials. An investigation about the effect of matrix polarity on the ion transport process is also carried out, making use of the concepts concerning polymer segmental relaxation. Hence the enhanced matrix polarity is found to contribute to the improvement in ion conduction, mainly through its promotion of salt dissociation. However, at high temperature this facilitation is counteracted due to the “anomalous” temperature‐dependence of salt dissociation in the polymer matrix, and the higher the matrix polarity, the more drastic is the drop in carrier number with rising temperature.
The alignment of LC side‐chain polymers in directing electric fields: theory and practice
Authors: Nazemi Ali , Williams Graham , Attard George S. , Karasz Frank E.
Published: April 2003

The factors that control the alignment of LC side‐chain polymers in directing a.c. and d.c. electric fields are critically reviewed. The principles involved when alignment is attempted by cooling from the melt in the presence of an electric field or by direct application of the field to a material in its liquid‐crystalline (LC) state are outlined, and the difficulties which may be encountered in practice are described and evaluated. An “electrical cleaning” method whereby the low‐frequency conductance losses in a sample may be reduced is described and is applied to LC polymer materials. Experimental dielectric data are presented and analysed for two LC polymers which contain azo‐groups in the side chains.
Polymers for electrical and optical data storage
Authors: Kämpf Günther , Freitag Dieter , Fengler Gerd , Sommer Klaus
Published: April 2003

Polymers possess great significance in data storage technology. Taking as an example electrical and optical data storage, the state of development, properties required and opportunities for application of selected polymers are discussed, namely: (i) ferroelectric polymers with low switching voltages and extremely short switching times for electric data storage; and (ii) transparent polymers with low birefringence and high thermal stability for optical data storage.

In the area of electrical data storage devices/memories, ferroelectric polymers have not been able to establish themselves up to now due to their long switching time and limited thermal stability. However, recent investigations show that suitable copolymers based on PVDF/TrFE copolymers in ultra‐thin layers can achieve switching times of ≤100 ns. Nevertheless, the limited thermal stability of PVDF/TrFE copolymers prevent them from being integrated into the usual manufacturing process for Si‐based data storage devices (D‐RAM resp. S‐RAM) and thereby frustrates the desired objective of producing nonvolatile random access memories (NV‐RAMs).

In the area of optical data storage technology, polycarbonate (PC) has established itself due to its favorable combination of properties. Thus, audio compact disks (CDs) are manufactured exclusively of PC, while high‐flow PC types of high optical purity are clearly the preferred substrate material for optical data storage disks. The increasingly stringent requirements to be met in terms of lower birefringence and better thermal stability mean that the development of suitable modified or substituted polycarbonates is required. The development work being carried out worldwide in this area is reviewed here, and new suitable substituted polycarbonates with lower birefringence and significantly increased thermal stability up to glass temperatures of 238°C are presented.

In addition, we deduce structure—property relationships for the above‐mentioned structurally modified polycarbonates, specifically considering rotation potentials along the polymer backbone.
The change of the superstructure of semicrystalline polymers during deformation: results from small‐angle scattering with synchrotron radiation
Authors: Wilke Wolfgang , Bratrich Michael , Heise Bernd , Peichel Gerhard
Published: April 2003

The change of the superstructure of different polyethylenes during uniaxial deformation is investigated. The method used is small‐angle scattering with synchrotron radiation. For branched polyethylene (Lupolen 1840D) the whole deformation range is analyzed. Beginning with superstructure of the lamellar cluster type, the superstructure partly disappears on a time scale of a few minutes and the fibrillar structure is built up. The degree of destruction and rebuilding depends on the drawing temperature. For very high molecular weight polyethylene (GUR) a reversible change of the superstructure at higher deformation ratios and at different temperatures is observed. The superstructure of (ethylene—hexene) copolymers (TIPELIN) at high draw ratios depends on the drawing temperature and is almost independent of the side group content. Interfibrillar microcracks parallel to the draw direction are produced in samples with a low side group content for draw ratios λ ≥ 1.5.
Mesomorphic and ferroelectric properties of FLCP/FLC binary mixtures
Authors: Dumon M. , Nguyen H. T.
Published: April 2003

We have prepared several ferroelectric polysiloxanes with two and three benzenic ring moieties. The siloxane backbone is favorable to ferroelectric S phase formation, and the chiral S phase is observed in all of the polymers. Some of the spontaneous polarizations are very high, more than 100 nC/cm2 (10−3 C/m2) and the response times are less than 1 ms near the I‐S or Sa–SS transition. Several binary mixtures between FLC copoly‐siloxanes and different low molar mass LC have been studied, and have shown the complete miscibility of these two components and richer mesomorphic sequences than for the polymers alone; for example, an N*–Sa sequence.
Electro‐optical properties of ferroelectric liquid crystalline polymers
Authors: Yuasa Kimihiro , Uchida Shunji , Sekiya Takashi , Hashimoto Kenji , Kawasaki Kenji
Published: April 2003

Ferroelectric liquid crystalline polymers (FLCPs) were synthesized. These ferroelectricities were confirmed directly by measuring polarization reversal currents and other electro‐optical properties. The smectic layer structure of FLCP was also studied. A chevron structure similar to that of low molecular weight FLC was observed even in an FLCP cell; but the zigzag defects were not so sharp, which means that it is easy to obtain a good orientation even in large‐area displays.
Polymeric liquid crystals: structural basis for ferroelectric and nonlinear optical properties
Authors: Zentel R. , Poths H. , Kremer F. , Schönfeld A. , Jungbauer D. , Twieg R. , Willson C. G. , Yoon D.
Published: April 2003

This paper describes the rational design and structure–property relations in three different types of polar LC polymers with interesting material properties, as follows. (i) Chiral LC polymers, which are functionalized with crosslinkable groups, can be converted into LC elastomers with chiral smectic C* phases. The mechanical orientability of these elastomers leads to new piezoelectric materials. (ii) The curing (dense crosslinking) of a polymer matrix provides one possibility of stabilizing the polar order of dye molecules, which is necessary for frequency doubling. Additionally, LC phases can help to stabilize this polar structure, which leads to large and stable nonlinear optical coefficients. (iii) Polymer analogous esterifications offer a convenient method for the synthesis of chiral smectic C* polymers with large ferrolectric polarizations.
Antiferroelectric behavior in a liquid crystalline polymer
Authors: Skarp Kent , Andersson Gunnar , Gouda Fathi , Lagerwall Sven T. , Poths Holger , Zentel Rudolf
Published: April 2003

Electro‐optic and polarization reversal measurements were performed on a side‐chain polymer exhibiting a chiral smectic phase. Based on the observed electro‐optic and current responses, we discuss the possibility of an antiferroelectric structure in the polymer. In order to establish a model for the observed behavior, a detailed comparison with the properties of the low molar mass antiferroelectric substance MHPOBC was made. The birefringence modulation in the chiral smectic polymer, originating from the field‐induced antiferroelectric‐to‐ferroelectric transition, is analyzed for the case of a randomly oriented sample. The result shows that the coincidence of birefringence modulation and polarization current peaks is strong evidence for the existence of antiferroelectric order in the smectic layers. Such coincidence was observed both for MHPOBC and the chiral side‐chain polyacrylate.
SAXS investigations on chiral liquid crystalline polymers: antiferroelectric and ferrielectric structures?
Authors: Mensinger Hildegard , Biswas Amit
Published: April 2003

The structure and phase behavior of liquid crystalline polymers (LCPs) having a common chiral side chain mesogen but different main chain structures have been investigated using small‐angle X‐ray scattering (SAXS). While the low molecular weight chiral side chain mesogen by itself exhibits ferroelectricity, the SAXS data of the side chain LCP with a flexible polyacrylate backbone contains a bilayered superstructure peak that is indicative of antiferroelectric order. The combined LCP with a nonpolar main chain mesogen also has a bilayered superstructure, but has a different structural organization in the proposed antiferroelectric phase compared to the side chain LCP. Further changes in the phase behavior and structural organization occur when a polar group is introduced into the main chain mesogen. A ferrielectric phase has been proposed to explain the observation of a trilayered superstructure in the corresponding SAXS data. The influence of the chemical structure and connectivity on the phase behavior and superstructure formation in the chiral LCPs is discussed.
Electromechanical effects in ferroelectric liquid crystalline polymers
Authors: Jákli Antal , Éber Nándor , Bata Lajos
Published: April 2003

Electric fields can induce mechanical vibrations in planar aligned sandwich cells of ferroelectric liquid crystals. Measurements on a polysiloxane and a polyacrylate side chain polymer proved that the electromechanical effect also exists in ferroelectric liquid crystalline polymers. The main characteristics of the electromechanical responses of these polymers are described and compared to the response of low molecular weight ferroelectric liquid crystals. According to the proposed interpretation, the vibrations in the direction parallel to both the smectic layers and cell substrates are due to coupling between the director rotation and the flow, while the resonances in the vibrations normal to the plates are connected to layer deformations.
Degradable polymers for site‐specific drug delivery
Authors: Domb Abraham , Amselem Shimon , Shah Jaymin , Maniar Manoj
Published: April 2003

The present article was aimed to review the properties and applications of the actually available biodegradable polymers that have been used as targetable drug carriers and site‐specific delivery systems. We have mainly focused on microparticulate or carrier‐based drug delivery systems with little emphasis on implants as site‐specific delivery systems.

The review was divided into two major sections. The first section includes a brief description of the properties and applications of the existing biodegradable polymers for site‐specific drug delivery classified in two main categories: synthetic biopolymers (as polyesters, polyanhydrides, polyorthoesters, polyphosphazenes, polycaprolactones), and natural biomaterials (as collagen, albumin and gelatin), which still remains an active area of research in spite of the extensive development of new biodegradable polymers.

The second section discusses the mechanistic approaches for the selection of polymeric carriers. General guidelines for the ideal drug carrier complex were summarized. The importance of knowing and understanding the physicochemical properties of the polymer for the optimization of the final formulation and its eventual application were emphasized. The factors governing the effective drug concentration at the specific target site were reviewed. Some of the equations describing the release kinetics of a drug from a polymeric matrix were also examined.

The last section of the review describes the preparation and use of polymeric macromolecular prodrugs. A diagrammatic representation of possible polymeric prodrug systems for use in site‐specific delivery was described. The basic requirements from a polymeric prodrug system were also discussed. Finally, clinical applications of polymeric prodrugs as for cancer therapy and colonic delivery were considered.
Site‐specific drug delivery to the lung
Authors: Auerbach Robert , Erdman Boyd , Kubai Louis
Published: April 2003

Investigations were undertaken to determine whether anti‐cancer drugs introduced locally into the lung using bioerodible polyanhydride microspheres as carriers would demonstrate both efficacy and reduced toxicity.

BCNU (carmustine) and CDDP (cisplatin), loaded in polyanhydride microspheres, were administered to mice bearing either of two tumors selected for their affinity for the lung: the B16F10 melanoma and the recently established GL26F4 glioma. Following intravenous inoculation of these tumor cells, the number of metastatic foci formed in the lung follows a predictable time course and can readily be determined. Comparisons were made between the efficacy of microspheres introduced into the lung by intratracheal intubation (IT) and of those administered by intraperitoneal injection (IP). Administration of microspheres loaded either with BCNU or cisplatin reduced the detectable metastatic foci by 25–90% depending on the tumor load, both when administered IP and IT.

Toxicity was assessed by flow cytometric analysis of bone marrow cellularity as well as by determination of mortality rates. Intratracheal administration of either cisplatin or BCNU reduced the deleterious systemic effects observed when the drug was administered by IP injection. This was seen at high drug levels, where significant mortality occurred only in animals given drug injections IP; and at lower levels where IP injection led to a reduction of bone marrow blast cells, while IT administration caused no detectable effect on marrow cellularity.

Since local delivery of BCNU or cisplatin through bioerodible polyanhydride microspheres induces significantly less systemic damage while demonstrating efficacy equal to or exceeding that of IP injection, this mode of drug delivery warrants further and more detailed exploration. Moreover, the method may be applicable to the treatment of other chronic pulmonary pathologies.
Sustained release of acetylcholine in rat hippocampus using a polyanhydride drug‐delivery system
Authors: Mayberg Marc R. , Gross Alan S. , Mathiowitz Edith , Langer Robert
Published: April 2003

A biodegradable polymer drug‐delivery system has been developed for the selective localized application of agents to brain parenchyma. The copolymer of poly[bis(p‐carboxyphenoxy)propane] anhydride and sebacic acid (PCPP–SA) was impregnated with [3H]‐acetylcholine (ACh) to form 1–5 μm microspheres. Drug‐loaded microspheres were implanted into hippocampus bilaterally in 25 rats, and brain sections processed for autoradiography in groups of five animals at 2, 5, 10, 20 and 40 days, respectively. By densitometric analysis, the concentration of radiolabelled ACh in polymer and adjacent hippocampus rapidly decreased between 2 and 5 days, after which a gradual decrease in [3H]‐ACh was observed up to 40 days. Between 2 and 40 days the concentration of radiolabelled ACh was reduced by 25.8% in polymer matrix and 40.1% in hippocampus. The spread of [3H]‐label into adjacent brain parenchyma showed a similar temporal relationship, with initially wider dispersion at 2 days (44±3 μm), then a linear decrease in dispersion over the remaining period (10±0.9 μxm at 40 days), suggesting bulk flow of the radiolabel into hippocampus. Brain parenchyma showed only a minimal inflammatory reaction to the polyanhydride implants over all time periods. Polyanhydrides can provide localized continuous release of ACh to brain parenchyma, and may potentially be used to deliver various agents to brain in a number of clinical and experimental applications.
Local release polymeric‐controlled immunotherapy of cardiac transplants in rats
Authors: Bolling Steven F. , Lin Hua , Ning Xue‐han , Levy Robert J.
Published: April 2003

Systemic immunosuppression frequently results in severe side effects. To evaluate a method of limiting the adverse effects of immunosuppression, we implanted controlled release matrices containing cyclosporine‐A (Cy) embedded (0.2 or 1 mg/kg/day released), steroid embedded (2%, 0.2% and 0.02% dexamethasone, Dex) or both (Cy 0.2 mg and Dex 0.2%) locally around the transplanted heart at the time of rat heterotopic (neck) heart transplants. Controls received empty (non‐drug) matrix implants. To elucidate a local effect, additional groups received Cy (0.2 mg) or Dex (0.2%) matrix implanted in a subdermal distal leg pouch at the time of heart transplant, without a local neck implant. Rejection was determined by the lack of transplanted heart contractions. Recipient animals received no other form of immunosuppression.

The Cy (0.2 mg) animals had whole‐blood Cy levels monitored for 6 weeks following transplantation. Cy levels peaked at 7–10 days after transplant (119 ± 26 ng/ml) and decayed to <50 ng/ml by day 42. At no time did whole‐blood Cy levels reach clinically significant levels. Additional animals had whole‐blood, heart and kidney Cy levels measured at day 6 post‐transplant. Both doses of local Cy demonstrated good survival benefit and were well absorbed locally, resulting in high Cy levels in heart tissue (>9,000 ng/mg). Furthermore, while low‐dose Cy (0.2 mg) demonstrated significant survival benefit, these animals had clinically negligible blood Cy levels on day 6 (<100 ng/ml) and very low kidney Cy levels. Interestingly, the lowest dose of Dex demonstrated no survival benefit, while the mid‐ and high‐Dex doses demonstrated good survival benefit: however, the high‐Dex dose had poor wound healing. Cy and Dex combination did not increase efficacy, perhaps due to release problems from physicochemical interactions.

Local immunosuppression with a controlled release matrix resulted in a significant survival advantage and was effective in delaying rejection. This approach may prove advantageous clinically, in extending transplantation and lessening immunosuppression side effects.
Preparation of polyimides utilizing the Diels–Alder reaction, II: Bis[N‐(butadienyl‐2‐methyl)] amino arylenes with bismaleimides
Authors: Smith J. G. , Ottenbrite R. M.
Published: April 2003

Four new bisdienes were prepared from 2‐bromomethyl‐1,3‐butadiene and N,N‐diethyl benzidine; bis[4‐(N‐ethyl) aminophenyl]‐p‐diisopropylbenzene, 1,4‐diamino‐2,3,5,6‐tetramethylbenzene and α,α′ bis(4‐amino‐3,5‐dimethyl phenyl)‐p‐diisopropyl benzene. Polyimides were synthesized by the Diels–Alder reaction of these bisdienes and bis(4‐maleimidylphenyl)methane and bis(3‐maleimidylphenyl) sulfone. The polymers were soluble in m‐cresol, dimethyl sulfoxide and chlorinated hydrocarbon solvents. Moderate thermal stability was observed by thermogravimetric analysis in air and nitrogen.