bluuebunny/crossref_metadata_2025 huggingface dataset:
Polymeric biodegradable lipospheres™ as vaccine delivery systems
Authors: Amselem Shimon , Alving Carl R. , Domb Abraham J.
Published: April 2003

This study describes the preparation and use of polymeric lipospheresTM as a potential vehicle for the controlled‐release of vaccines. Lipospheres are a new encapsulation technology for parenteral drug delivery that have been also used successfully as carriers of vaccines. A recombinant malaria antigen, R32NS1, derived from the circumsporozoite protein of Plasmodium falciparum, was incorporated in biodegradable polymeric lipospheres in the absence or presence of lipid A as an adjuvant. The immunogenicity of polymeric lipospheres composed of polylactide (PLD) or polycaprolactone (PCL) was tested in rabbits after intramuscular injection of the formulations. High levels of specific IgG antibodies were observed in the sera of the immunized rabbits up to 12 weeks after primary immunization, using a solid phase ELISA assay. PCL lipospheres containing the malaria antigen were able to induce sustained antibody activity after one single injection in the absence of immunomodulators. PCL lipospheres showed superior immunogenicity compared to PLD lipospheres, the difference being attributed to the different biodegradation rates of the polymers. Biodegradable polymeric lipospheres represent a pharmaceutically acceptable vaccine delivery system with immunopotentiating activity for humoral antibody responses. The high permeability to many therapeutic drugs, and a lack of toxicity, has made PCL and its derivatives well suited for controlled drug delivery. The results obtained in this study are very promising, with the expectation that the use of biodegradable polymeric lipospheres might be very useful in the conversion of multiple‐dose vaccines to single‐dose vaccination, avoiding the need for repeated immunizations.
Osteoblast culture on bioerodible polymers: studies of initial cell adhesion and spread
Authors: Laurencin Cato T. , Morris Carol D. , Pierre‐Jacques Henri , Schwartz Edith R. , Keaton Altorous R. , Zou Ligan
Published: April 2003

The development of systems for the growth of osteoblasts on bioerodible polymeric matrices was explored. Three classes of bioerodible polymers were studied as possible matrix supports for osteoblast growth: the poly(anhydrides), poly(phosphazenes) and poly(lactic acid/glycolic acid) copolymers. Neonatal calvarial cells from Sprague–Dawley rats were seeded onto polymer disks at a density of 1 × 104 cells/cm2. Initial attachment and spreading, rate of growth and morphology were determined, and retention of osteoblast‐like phenotype was assessed through measurements of alkaline phosphatase activity in the presence and absence of 1,25(OH)2 vitamin D3. All results were considered relative to tissue culture polystyrene.

Cells were found to attach to all polymers at 8 hr post‐seeding. By 24 hr, cell numbers on all polymers were found to be decreased, except for poly(lactic acid/glycolic acid). Rat calvarial osteoblasts seeded on poly‐(lactic acid/glycolic acid) reached confluency and retained their phenotype.

Successful construction of viable osteoblast–bioerodible polymer composite materials, as presented in our study, may find their usefulness as grafts for atrophic non‐unions of bone, for healing craniofacial and other defects and for use as prosthetic implants or coatings. Composite systems of osteoblast cultures may also find their usefulness in furthering our understanding of bone differentiation, maturation and metabolism in a matrix environment.
Miscibility and crystallization kinetics in blends of poly(ethylene terephtalate) and thermotropic liquid crystal polyesters
Authors: Mélot Denis , MacKnight William J.
Published: April 2003

Binary blends of poly(ethylene terephtalate) (PET) and thermotropic liquid crystal polyester (TLCP) have been prepared by both solution and melt blending methods. The TLCPs utilized were Vectra (Hoechst Celanese), TR‐4, a TLCP synthesized in our laboratory, and a block copolymer consisting of three TR‐4 units followed by three PET units. The phase behavior of the blends was studied by differential scanning calorimetry (DSC), dynamic mechanical thermal analysis (DMTA) and optical microscopy. The results show that none of the blends is miscible, but significant interactions exist between the PET phase and the TLCP phase in the case of TR‐4 and TR‐4 block copolymer blends. These interactions lead to a different nucleation mechanism in these blends compared to that in PET/Vectra.
Formation of PPy/Ta2O5/Ta structure by electropolymerization
Authors: Park Young‐Seo , Takeoka Shinji , Yamamoto Kimihisa , Tsuchida Eishun
Published: April 2003

Electropolymerization of pyrrole on tantalum (Ta) electrodes was carried out in buffer solutions (0.04 M phosphoric acid, 0.04 M acetic acid, 0.04 M boric acid and 0.2 M sodium hydroxide) containing 0.1 M sodium ptoluenesulfonate (TsONa) under galvanostatic conditions and it was found that a polypyrrole (PPy) and a tantalum oxide (Ta2O5) layer are formed on a Ta electrode by an electrochemical oxidation process. The conditions of this simultaneous formation were studied in respect to current density (id), pyrrole concentration ([Py]), pH and the amount of electricity. Under certain conditions ([Py] = 0.25 M, pH = 1.8, id = 10–20 mA cm−2, the amount of electricity = 1 C), 6–8 μm thick PPy films were efficiently formed on homogeneous 30–50 nm thick Ta2O5 layers. The PPy film showed a high electrical conductivity (110 s cm−1), adhered well and covered the Ta2O5 layer. The resulting PPy/Ta2O5/Ta system is therefore proved to have excellent properties as a capacitor.
Sulfur‐containing polymers by the reaction of diphenyl sulfide with sulfur chlorides
Authors: Miyatake Kenji , Jikei Mitsutoshi , Yamamoto Kimihisa , Nishide Hiroyuki , Tsuchida Eishun
Published: April 2003

The electrophilic reaction of sulfur dichloride with diphenyl sulfide proceeds efficiently at room temperature to yield oligo(phenylene sulfide) in the presence of a catalytic amount of Fe powder. Sulfur dichloride shows higher reactivity than sulfur monochloride. The reaction is promoted through the activation of sulfur dichloride by Fe powder. The polymeric product contains a linear structure linked by disulfide and sulfide bonds.
A lithium secondary battery using a thin film of polymer electrolyte as a separator
Authors: Ohta Tomoyuki , Takeoka Shinji , Tsuchida Eishun , Feng Han Yu , Fu Zheng Sheng , Wang Yun Pu
Published: April 2003

Ion‐conductive polymer which shows an ionic conductivity (σi) of 1.4 × 10−4S/cm at 25°C when mixed with LiClO4 (molar ratio in Li/OE = 0.05) was used as a separator of electrodes in a lithium secondary battery. The effect of high ionic conductivity on the performance of the battery was studied. The polymer structure was $$ \left[ {\rm H}\rlap{-} ({\rm CH}_2 {\rm CHR}\rlap{-} )_{\rm n} {\rm H},{\rm R} = - {\rm CH}_2 ({\rm OCH}_{\rm 2} {\rm CH}_{\rm 2} )_6 {\rm OCH}_3 \right],$$ and the cathode was comprised of poly(1,3,4‐thiadiazole disulfide), graphite powder and the polymer electrolyte. The cell [(−)Li/polymer electrolyte/graphite–poly(disulfide) (+)] had an open circuit voltage (Voc) of 3.25 V, a plateau voltage of 2.75 V, a discharge density (id) of 0.05 mA/cm2 with the cathode utilization of 63%, and achieved over several tens of cycles at 25°C.
Cellulose–polyacrylonitrile blends, 1: thermodynamic interaction parameters and phase diagram in dimethylacetamide–LiCl
Authors: Marsano Enrico , Tamagno Monica , Bianchi Estella , Terbojevich Maria , Cosani Alessandro
Published: April 2003

The phase diagram of ternary mixtures composed of cellulose, polyacrylonitrile and dimethylacetamide–7% LiCl was determined at room temperature. Homogeneous solutions were observed at low polymer concentrations. Two demixing areas were experimentally evidenced when the concentration increased: the first corresponds to an equilibrium between isotropic phases, while the second represents the coexistence of a cellulose mesophase with an isotropic phase. The diagram is discussed in terms of the interaction parameters, determined via light scattering.
Synthesis of a novel polysiloxane‐based polymer electrolyte and its ionic conductivity
Authors: Ni Jianlong , Lin Yunqing , Wang Fosong
Published: April 2003

Graft copolymers were synthesized by means of hydrosilylation from poly[hydromethylsiloxane)‐co‐dimethylsiloxane)] and allylether of poly(ethylene oxide)‐co‐(propyleneoxide)] (poly(EO‐CO‐PO)). Network polymer electrolyte complexes were made from the graft copolymers and alkali metal salt by solvent‐casting from acetone and the tetraethyl orthosilicate crosslinking method. The influence of composition of the polyether side chains, and the species and concentration of inorganic salts on the ionic conductivity were investigated. The temperature dependence of the ionic conductivity of the network film was also studied. It is shown that the complexes of the network polymers with alkali metal salt exhibit a very high ionic conductivity of about 5 × 10−5 S/cm at 25°C and have the characteristic of a typical noncrystalline solid electrolyte.
Ionic conductors based on modified poly(p‐phenylene terephthalamide)
Authors: Foo Conrad , McBreen James , Xu Zhe‐Sheng , Okamoto Yoshiyuki
Published: April 2003

Ionic conductors based on N‐substituted oligo(ethylene oxide) poly(p‐phenylene terephthalamide) (PPTA) were investigated. Two different PPTAs (Mv = 12,000 and 3600) were grafted with tri(ethylene oxide) and hexa(ethylene oxide). These modified PPTAs were found to be soluble in organic solvents such as dimethyl acetamide and dimethyl sulfoxide and were miscible with various concentrations of oligo(ethylene oxide). The resulting blends formed complexes with lithium trifluoromethanesulfonate (LiSO3CF3). The thermal and ionic conductive properties of the blends were investigated. The conductivities of some of the blends were in the range of 0.5–5.0 × 10−5 S/cm at 25°C and 0.5–5.0 × 10−4 S/cm at 100°C. The profile of conductivity at various temperatures followed the Vogel–Tammann–Fulcher (VTF) plots and it suggested that the major ionic transport took place in the amorphous phase.
Photoresponse in ionic conductivity for poly[(ω‐hydroxy)oligo(oxyethylene) methacrylate‐co‐butyl methacrylate] doped with spiropyran derivative and LiClO4
Authors: Kubo N. , Yoshii T. , Kobayashi N. , Ikeda K. , Hirohashi R.
Published: April 2003

Photoresponse in ionic conductivity has been realized in the solid polymer electrolytes, consisting of poly[(ω‐hydroxy) oligo(oxyethylene) methacrylate] [P(MEO)OH] or poly[(MEO)OH‐co‐butyl methacrylate] (PBMA), spiropyran derivative (SP) and LiClO4. SP showed reversible isomerization upon photoirradiation in these films. The ionic conductivity in these films decreased upon ultraviolet light (UV) irradiation and subsequently increased upon visible light (Vis) irradiation. The interaction between photoisomerized merocyanine form (PMC form) and the hydroxyl group on the polymer side chain was confirmed by an IR shift assignable to OH stretching vibration. From DSC thermograms, the change of ionic conductivity was revealed to be considerably affected by this interaction and attributed to reversible photoisomerization of SP. Reversibility of ionic conductivity was improved in copolymer P[(MEO)OH‐co‐BMA] in comparison with that in P(MEO)OH.
A Raman study of ion solvation and association in polymer electrolytes
Authors: Torell Lena M. , Jacobsson Per , Petersen Greger
Published: April 2003

Ion–polymer and ion–ion interactions in polymer electrolytes have been investigated at different temperatures and pressures, and for different polymer molecular weights. Salt–polymer complexes of various triflate salts, M(CF3SO3)x (M = Li+, Na+, Ca2+, Cu2+ and Nd3+), in low molecular weight polyethers (PEO and PPO) have been studied using Raman and Brillouin scattering. It is found that anions coordinated to the OH end groups of the polyethers are more stable than cations forming crosslinks between oxygens of adjacent chains, which in turn are more stable than cations coordinated to single chains. We have observed that the number of ion pairs increases as the polymer molecular weight increases. Furthermore, the ion–ion interaction is strongly temperature‐dependent and shows widely different behavior in different systems. In the case of Li+‐, Na+‐ and Ca2+‐containing polyether complexes the ion association increases with increasing T. It is constant in Cu2+–triflate complexes, while it decreases for complexes containing trivalent Nd3+ cations. Pressure observations in LiCF3SO3–PPO complexes reveal increasing solubility and fewer ion pairs as pressure increases. It is shown that theories which consider volume changes in the salt dissociation process can qualitatively explain the effects of molecular weight, temperature and pressure using entropy considerations. The entropy effect includes contributions due to free‐volume dissimilarities between the solvated ions and the macromolecules, structural ordering induced via cationic crosslinking of adjacent chains and electrostriction. Comparing the spectroscopic data with conductivity data, it is found that differences in the “free” solvated ion concentration can account for differences in conductivity.
Softening behavior and conductivity in ionene polymer glasses
Authors: Rietz Ralf‐R. , Meyer Wolfgang H.
Published: April 2003

Ionene glasses are considered as being a new class of materials. Their properties have been investigated in detail by thermoanalytical, solid state NMR, and dielectric techniques. The segmental dynamics of these cationic polyelectrolytes, labeled in chosen positions, have been studied with solid state 2H‐NMR. Below the glass transition the quaternized ammonium groups in the polymer backbone are essentially static, due to strong Coulomb interactions. The glass transition in these materials is characterized by the softening of a network formed by the N+‐cations. However, both the low molecular weight counterions and the organic chain segments linking the ammonium groups are already mobile below Tg. The dynamics of the organic segments in the glassy state can be described as motion between fixed ends. Ionic conductivity in the glassy state is based on thermally activated anion transport. The influence of the flexibility of the organic chain segments and of the type of the anion on the conductivity are discussed. A simple analytic expression is proposed to describe the conductivity behavior in the low frequency limit.
NMR studies of ion mobility and association in polyether‐based polymer electrolytes
Authors: Greenbaum Steven G.
Published: April 2003

The results of several investigations of polyether‐based polymer electrolytes by nuclear magnetic resonance (NMR) spectroscopy conducted in the author's laboratory and by other groups are reviewed. For both 7Li and 23Na NMR, the onset of motional line‐narrowing occurs at about the glass transition temperature, illustrating the importance of polymer segmental motion to ion transport. Examples of the ability of NMR to probe cationanion interactions are discussed. These include chemical shift variations corresponding to different Li+ environments and nuclear quadrupole coupling and relaxation behavior as a probe of Na+ environment.
Paper form copper ion conductive solid electrolyte
Authors: Hara T. , Yasuda N. , Nagata M. , Kondo S. , Sotomura T.
Published: April 2003

A paper form solid electrolyte (PFSE) with good conductivity and flexibility was developed. PFSE is made of an inorganic–organic composite consisting of a copper ion conductive solid electrolyte of Rb4Cu16I7Cl13 (SE) and a polymer binder embedded in a synthetic fibre network. A PFSE with styrene–butadiene based synthetic rubber (SB) was found to give the highest conductivity among the binding materials that we examined. The SB content was changed from 10 vol% to 90 vol% in the PFSE, and the electrical properties and the damp resistance of PFSE were evaluated. Electrical conductivity decreased slightly with an SB content below 70 vol% and abruptly above 70 vol%. The damp resistance of PFSE improved with the increase of the SB content and was superior to that of the raw powder. The PFSE with 65 vol% SB showed relatively high conductivity, 3 × 10−3 S/cm, which was sufficient for battery use, and good damp resistance.
Development and commercialization of ionic‐type photosensitive polyimides
Authors: Asano Masaya , Eguchi Masuichi , Kusano Kazutaka , Niwa Katsuhiro
Published: April 2003

Toray's ionic‐type photosensitive polyimide, “Photoneece”, is widely used as an interdielectric and as a protection layer for microelectronics, because of its properties, such as the removal of photoreactive groups at low temperature, excellent thermal, mechanical and electrical film properties and excellent adhesion to various substrates. Toray has developed a new type of “Photoneece”, UR‐5100, which is a low‐stress photosensitive polyimide. In addition to a low thermal expansion coefficient (25 ppm/°C), “Photoneece” UR‐5100 also features high resolution with an aspect ratio of more than 2.0 in 40 μm imaged film, and excellent mechanical properties in the cured film such as high elongation (>20%) and tensile strength (>200 MPa), even after 60 hr heat treatment at 350°C. “Photoneece” UR‐5100 can be applied in multichip modules (MCMs), hybrid circuits, ICs and LSIs. In this paper the characterization and processing of this “Photoneece” UR‐5100 are described.
Negative‐type photosensitive polyimide precursors developable with aqueous alkaline solutions
Authors: Kikkawa H. , Shoji F. , Tanaka J. , Kataoka F. , Satou H.
Published: April 2003

New photosensitive polyimide precursors developable with aqueous alkaline solutions were synthesized. Among diamine monomers having a photofunctional group, 2′‐(methacryloyloxy)ethyl 3,5‐diaminobenzoate yields high molecular weight polyamic acid. A photosensitive polymer composition consisting of Michler's ketone and a thermally stable peroxide, 3,3′,4,4′‐tetrakis(t‐butyldioxycarbonyl)benzophenone, results in a high photosensitivity of 200 J/m2. The photosensitive coating of the composition is soluble in aqueous alkaline solutions as well as in organic aprotic polar solvents, and both solvents can be used as developers. However, the resolution of patterns is quite different, especially in thick films. Solvent developers results in poor resolution, whereas aqueous alkaline developers give patterns of high aspect ratio even in thick films. This is probably due to the difference in the diffusion efficiency and swelling properties of the polymer compared to the developers.
Polyimides for electronics applications
Authors: Mukerji Prosanto K. , Demet George
Published: April 2003

A variety of options exists for lithographically defining polyimides for microelectronics applications. The two investigated here, photosensitive polyimide and wet etching of low‐stress polyimides, offer lower cost, higher throughput solutions compared with dry etch processes. Via sizes of less than 25 μm and film thicknesses of greater than 14 μm are difficult to process using these techniques: however, for applications such as interlayer dielectrics for high‐density packaging or solder masks for flip chip die attachment, these limitations may not be insurmountable. Photosensitive polyimide can be patterned with fewer steps, but the overall quality of the film in terms of surface planarity and residual stress is not as good as wet etching of conventional polyimide.
Oxidation of a PPy‐modified tantalum electrode
Authors: Park Young‐Seo , Yamamoto Kimihisa , Takeoka Shinji , Ohta Tomoyuki , Tsuchida Eishun
Published: April 2003

A tantalum electrode on which polypyrrole (PPy) had been previously formed by electropolymerization was galvanostatically electrolyzed in an aqueous solution of 0.01 wt% phosphoric acid. This process contains the irreversible oxidation of a PPy film, the decomposition of solvent, and the formation of Ta2O5 by the reaction of OH− coming through the PPy film, with Ta electrodes. A three layer‐structure (PPy/Ta2O5/Ta) was confirmed by electron spectroscopy for chemical analysis (ESCA). A PPy film containing CIO4− as dopant [PPy(CIO4−)] was significantly deteriorated in comparison with PPy(TsO−) at the electrolysis. Therefore, the (PPy(TsO−)/Ta2O5/Ta) system showed better electrical characteristics as a capacitor than the (PPy(CIO4−)/Ta2O5/Ta) system showed better electrical characteristics as a capacitor than the (PPy(ClO4−)/Ta2O5/Ta) system.
Antistatic applications of conducting polyaniline
Authors: Trivedi Dinesh Chandra , Dhawan Sundeep Kumar
Published: April 2003

A method is described to impart flexibility and mechanical strength to conducting polyaniline by polymerizing aniline on fabrics and on cellulose papers. The study indicates that these conducting fabrics offer 16–18 dB of shielding effectiveness for the control of electromagnetic interference (EMI) up to a frequency of 103 MHz.
Radiation‐induced crosslinking and grafting of two polyphosphazene elastomers
Authors: Grune G. L. , Stannett V. T. , Chern R. T. , Harada J.
Published: April 2003

The radiation‐induced crosslinking and grafting of two aryloxy‐substituted elastomeric polyphosphazenes have been carried out by both gamma and electron beam irradiation. The classic Charlesby–Pinner [1] plus a simpler approach were used to determine the G(X) values for the crosslinked elastomeric polymers. The apparent G(X) value for the same polymer depended on whether the gamma‐ray or the E‐beam results were used. The presence of 8.5% repeat units with allylic groups in the side chain increased the G(X) value by an order of magnitude when the irradiation was performed under vacuum with the gamma source. The extent of acrylic acid grafting was also higher for the polymer containing the allylic group. Nearly all the grafted polyphosphazene films were insoluble in THF, a good solvent for the ungrafted samples.
Phase separation behavior of epoxy resin modified with crosslinked rubber
Authors: Kim Dae Su , Kim Sung Chul
Published: April 2003

Low molecular weight liquid rubber (ATBN = amine terminated butadiene acrylonitrile copolymer or CTBN = carboxyl terminated butadiene acrylonitrile copolymer)–DGEBA (diglycidyl ether of bisphenol A) blends indicated upper critical solution temperature (UCST) behavior. The phase separation behavior of the neat and crosslinked rubber (ATBN, CTBN)–epoxy blends was analyzed by a laser light scattering experiment. Lauryl peroxide (LPO) was employed to crosslink the rubber during the initial annealing stage. The onset point of the phase separation in the crosslinked ATBN–epoxy system occurred later than in the case of the neat ATBN–epoxy system. However, the onset point of the phase separation process started earlier in the case of the crosslinked CTBN–epoxy system. The domain correlation length of the crosslinked rubber‐added system was smaller than that of the neat rubber‐added system.
Ethylene/propylene copolymers with vanadium‐based catalysts: Cocatalyst effect
Authors: Dall'Occo Tiziano , Galimberti Maurizio , Balbontin Giulio
Published: April 2003

Ethylene/propylene copolymers were obtained with vanadium‐based catalysts. Different aluminium alkyls were employed as cocatalyst: Al(C2H5)2Cl/promoter, Al(i‐C4H9)3, Al(n‐C6H13)3. and Al(n‐C8H17)3. The influence of the cocatalyst on the molecular weight, the molecular weight distribution and the microstructure of the copolymers was investigated through GPC, DSC, 13C–NMR analysis and fractionation.

AIR3 afforded a polymerization activity that was much higher with respect to Al(C2H5)2Cl/nBPCC, but with the latter cocatalyst system copolymers were obtained with a more homogeneous distribution of the monomers and the absence of crystallinity. A comparison with ethylene/propylene copolymers obtained with a V(Acac)3/Al(C2H5)2Cl/promoter and with a high‐yield Ti‐based catalyst is also presented.
Ethylene–styrene thermoplastic copolymers prepared with supported Ziegler–Natta catalysts
Authors: Masson P. , Spitz R. , Pasquet V.
Published: April 2003

The magnesium chloride supported Ziegler–Natta catalysts are able to copolymerize ethylene and styrene in conditions of high activity. Different parameters, including catalyst type, monomer ratio, temperature and Lewis bases, allow variation of the activity and reactivity ratio. The incorporation of styrene in the copolymer remains always rather limited in moles. The products obtained contain less than 20% styrene in weight, and seem very similar in structure to linear low‐density polyethylenes (LLDPE) obtained with the same catalyst: the melting temperature is only about 5°C lower than that of pure polyethylene. The polymer can be fractionated by solvents in a similar manner to LLDPE, and contains a styrene‐enriched fraction, but homopolystyrene production has never been observed.
Copolymerization of propene‐nonconjugated dienes: Derivatization through hydroboration and epoxydation
Authors: Dassaud Jean Philippe , Guyot Alain , Spitz Roger
Published: April 2003

Copolymerization of propylene and nonconjugated dienes such as 1–9 decadiene (α–ω symmetric) and 7‐methyl‐1,6 octadiene (asymmetric) is carried out in the presence of highly active isospecific catalysts for propene polymerization. The incorporation of the diene is random and does not affect the isospecificity of the catalytic system. For a low amount of diene, whatever its structure, an activation effect is observed. For the symmetric diene, the reactivity of the second double bond gives rise to crosslinking.

Derivatization through hydroboration or epoxydation is carried out in suspension, using a toluenetetrahydrofuran solvent mixture that is able to swell the polypropylene and dissolve the reactants. After hydroboration the copolymer is transformed into hydroxylated polymer through oxidation in a phase transfer condition. The epoxydized copolymer shows excellent adhesive properties on anodized stainless steel.
Reactive blending of polypropylene/polyamide‐6 in the presence of tailor‐made succinic anhydride‐terminated oligopropene compatibilizers
Authors: Mülhaupt Rolf , Duschek Thomas , Rösch Joachim
Published: April 2003

Various anhydride‐terminated isotactic and atactic oligopropenes of number average molecular weights ranging between 1,000 and 10,000 g/mole, prepared by maleinating vinylidene‐terminated propene oligomers obtained with isospecific and nonstereospecific metallocene‐based Ziegler–Natta catalysts, have been evaluated as blend compatibilizers of polypropylene/polyamide‐6 (70 vol%/30 vol%) blends to study the role of blend compatibilizer molecular architecture. When added during processing, as shown by IR spectroscopic analysis, the anhydride‐terminated oligopropenes react with the amine‐terminated polyamide‐6 to yield polypropylene‐block‐polyamide‐6 in situ. Such block copolymers are efficient dispersing agents. While the polyamide dispersion in the polypropylene continuous phase is not affected by blend compatibilizer stereoregularities, both stiffness and yield stress as well as notched Charpy impact strength increase with increasing stereoregularities and molecular weights. With oligopropene molecular weights exceeding 1,150 g/mole, the average size of the dispersed polyamide microphases correlates with the volume fraction of the oligopropene‐block‐polyamide‐6 blend compatibilizer and the dicarboxylic acid anhydride/amine molar ratio.
Mechanical behavior and tensile fractography of compatible vinylchloride–vinylacetate–maleic acid terpolymer and nitrocellulose blends
Authors: Chattopadhyay Saumya , Banerjee Amar Nath
Published: April 2003

Vinylchloride–vinylacetate–maleic acid terpolymer (VMCH) and nitrocellulose (NC) were blended at 10% (W/V) concentration is cyclohexanone at different weight fractions. Compatible blends were obtained at all weight fractions. This paper reports the mechanical behavior of solvent cast blend films of VMCH and NC. The films were prepared by solution blending and subsequent casting on a mercury surface. Depending on the composition, the tensile behavior ranged from brittle to ductile. The effect of the blend ratio on the properties shows that within the Hookeian region the modulus and strength have a positive deviation from linearity, whereas the elongation has a negative deviation. The effect of the blend ratio on the ultimate properties of the materials shows a positive deviation in strength up to 63 wt% VMCH composition and a negative deviation in elongation and toughness. The tensile fractography of the pure VMCH and VMCH/NC blends shows the presence of peaks, foldings of fibrils along with cavities or voids, which indicate a ductile mode of failure with craze‐initiated fracture. Fractography of the pure NC Indicates a brittle mode of failure wit
h craze‐initiated fracturing.
Properties of tetra‐N‐glycidyl‐4,4′‐diamino diphenyl methane (TGDDM) cured thick films
Authors: Soni H. K. , Patel R. G. , Patel V. S.
Published: April 2003

Thick films of tetra‐N‐glycidyl epoxy resin of p,p′‐diaminodiphenyl methane (TGDDM) were prepared using p,p′‐diaminodiphenyl methane (DDM), p,p′‐diaminodiphenyl sulfone (DDS) and diethylene triamine (DETA) as curing agent with or without the epoxy fortifiers PGEHA and VCDRC (at 20 phr level). These thick films were used to evaluate various physical, mechanical, chemical resistant and dielectric properties.
Molecular composites in thermosets
Authors: Kwei T. K. , Levon Kalle , Tesoro Giuliana , Liu Frank , Mey‐Marom Abraham , Munukutla Surya
Published: April 2003

The synthesis of molecular composites where rigid polymer molecules are reinforcing elements in a thermoset bisimide matrix has been investigated. The approach has been designed to avoid phase separation by selecting systems where reaction of amine‐terminated rigid and semiflexible oligomers with maleimide unsaturation occurs prior to crosslinking of the thermoset. This objective has been met for some compositions. The concentration and molecular weight of the rigid oligomers have been varied. The structure of the reinforcing polymer, the reactivity of the maleimide and the conditions for composite synthesis are variables of critical importance, and further work must determine the promise and limitations of this approach.
The effect of bridge group on the thermal stability of nitro‐substituted aromatic polyamides
Authors: Oh Sang Yeol , Pearce Eli M.
Published: April 2003

The effect of introducing a bridge group into the diamine moiety on the thermal stability of aromatic polyamides substituted with a nitro group in the diamine ring at the ortho position to the amide group was studied. Our present work showed that the bridge group, whether it was electron withdrawing or releasing, did not have a significant effect on the activity of the nitro group for the intramolecular cyclization reaction to poly(benzoxazole)s.
Contribution of size exclusion chromatography and thermal analysis methods in the study of the radiochemical behavior of plastic materials
Authors: Yagoubi N. , Baillet A. , Mur C. , Legendre B. , Pellerin F. , Ferrier D. Baylocq
Published: April 2003

Sterilization by irradiation techniques is considered to be an improved method to treat polluted products of human consumption. Secondary effects, that may be generated in the components of packaging materials, could induce organoleptic damage and some physico‐chemical modifications, observed especially in plastic materials. In order to demonstrate any such secondary changes, we have investigated the effects of beta‐irradiation (a treatment which could induce either a reticulation or a cleavage in a polymeric sequence) on three polymers; namely, low density polyethylene, polystyrene and polyvinyl chloride. The techniques used to identify irradiation‐induced modifications of these polymers were size exclusion chromatography and thermal analysis. Thermal analysis showed a decrease in the percentage of crystallinity of polyethylene after its radiosterilization. Exclusion chromatography highlighted a reticulation for irradiated polyvinyl chloride and polystyrene.
Resist performances and structure of phenolic resins using multi‐substituted phenols
Authors: Kajita Toru , Ota Toshiyuki , Tsuji Akira
Published: April 2003

Positive photoresist systems comprising phenolic resin and quinonediazide are studied in detail. The structure of several novolak resins, which were synthesized from multi‐substituted phenols, are analyzed with 13C‐NMR. It is proved that these phenols are useful for the structural control of novolak resins. Phenols with two methyl substituents at meta‐positions especially show a remarkable structural effect to control methylene bond types of novolak resins.

The alkaline dissolution rate is also investigated on novolak resins synthesized from multi‐substituted phenols to understand both the dissolution inhibition effect and the dissolution promotion effect. Key‐structure of novolak resins for realizing high resolution is elucidated.

In addition, the molecular design concept of novolak resin is clarified from several standpoints. Unsubstituted aromatic carbon of resin, hydrophobic effect of methyl substitutent and suitable structure of low Mw parts of novolak resin are also explored.

Furthermore, it is proposed that a resist using a resin, which is based on the molecular design concept, has enough potential to produce critical dimensions of 0.2 μm or less taking advantage of phase‐shifting technology.
193 nm resists and lithography
Authors: Kunz Roderick R. , Allen Robert D. , Hartney Mark A. , Hinsberg William D. , Horn Mark W. , Keast Craig L. , Rothschild Mordechai , Shaver David C. , Wallraff Gregory M.
Published: April 2003

A review of recent efforts to develop photoresist materials and processes for 193 nm (ArF excimer laser) photolithography is reported. Three categories of resist processes are discussed: (1) conventional single layer, (2) bilayer and (3) surface‐imaged resist processes. To date, materials have been developed for each process which exhibit resolution to less than 0.25 μm with sensitivities of less than 50 mJ/cm2.
Lithographic performance of isomeric hydroxystyrene polymers
Authors: Dammel R. , Rahman M. D. , Lu P. H. , Elango V.
Published: April 2003

The synthesis and lithographic characterization of the three positional isomers of polyhydroxystyrene is described. Large differences in dissolution rates are found as a function of the position of the hydroxy group, which are explained in terms of intra‐ vs. intermolecular hydrogen bonding and steric shielding of the hydroxy group by the polymer backbone. In plots of log (dissolution rate) vs. developer strength, linear plots are observed for the 2‐ and 4‐isomers, while for poly(3‐hydroxystyrene), a break occurs in the plot, leading to two linear regions. While the 2‐hydroxy isomer is too slow and the 4‐hydroxy isomer too fast for use in conventional dissolution inhibition systems, the copolymerization of both allows any dissolution rate between these extremes to be chosen ( “dial a dissolution rate” copolymers). Determination of the copolymerization parameters of the corresponding 4‐ and 2‐acetoxystyrene precursors by the method of Kelen and Tüdös shows the polymerization to be nearly ideal and azeotropic (r1 = 0.76, r2 = 0.94). Analysis of the dissolution rates as a function of developer strength according to the Huang–Reiser–Kwei equation shows that the critical concentrations c* are a linear function of copolymer composition, whereas the penetration exponents in show a minimum near unity in the region of the 1 : 1 copolymer, down from the values of 3.2–3.3 observed for all three homopolymers. The 1 : 1 copolymer shows a dissolution rate comparable to novolak resins, and when formulated into a photoresist together with a diazonaphthoquinone sensitizer resolved 0.4μm features at a dose of 340 mJ/cm2. The thermal flow resistance of the resist was found to be improved over that of novolak resists although not to the degree expected from the increased Tg of the 1:1 copolymer.
Functionalized polymers for high‐resolution photolithography
Authors: Sebald Michael , Ahne Hellmut , Leuschner Rainer , Sezi Recai
Published: April 2003

Polymers obtained by radical polymerization of maleic anhydride with different monomers are used in bilayer photoresists for the CARL (Chemical Amplification of Resist Lines) process. Aqueous‐based silylation of resist patterns with bisaminopropyl‐oligodimethylsiloxane enhances oxygen–plasma etch resistance and creates widened structures. Thus, the resolution capability of optical exposure tools can be used to the full extent and even structures beyond the optical resolution limit become accessible. Copolymerization of maleic anhydride with tBOC‐maleimide or methacrylic acid t‐butylester yields polymers for highly sensitive acid‐catalyzed deep UV resists. With the use of a KrF excimer‐laser stepper 0.25 μm structures are resolved.
The 1.4 and 248 nm radiation response of chemically amplified resists containing arylmethyl sulfone photoacid generators
Authors: Hanson J. E. , Pingor D. A. , Novembre A. E. , Mixon D. A. , Bohrer M. P. , Kometani J. M. , Tai W. W.
Published: April 2003

The X‐ray (1.4 nm) and deep UV (248 nm) radiation responses of chemically amplified photoresists incorporating arylmethyl sulfone photoacid generators were evaluated. The arylmethyl sulfones were primarily derivatives of benzyl phenyl sulfone, selected to reveal the importance of desulfonylation and internal abstraction with regard to the photochemical efficiency of acid generation. At 1.4 nm, benzyl phenyl sulfone gave a much more sensitive resist than dibenzyl sulfone, while the methyl derivatives of benzyl phenyl sulfone did not give much improvement over the parent compound. This suggests that desulfonylation is more important than internal abstraction for increased photochemical efficiency. At 248 nm, similar trends were observed, but with some modifications arising from the variation in extinction coefficient among the sulfones. Sensitivities at or below 20 mJ/cm2 were obtained for both wavelength ranges.
Excited state properties of a new photoinitiating system for laser imaging applications
Authors: Morlet‐Savary F. , Fouassier J. P. , Matsumoto T. , Inomata K.
Published: April 2003

The design of an efficient photosenzitizer/photoinitiator combination is partly governed by a better understanding of the excited state processes involved. In the present paper, the photochemistry of a thiopyrylium salt (TP) as photosensitizer and of a tetraperester of benzophenone, tetra t‐butyl peroxycarbonylbenzophenone (BTTB) as initiator, used in laser imaging applications has been investigated. The reactivity of the triplet states of both compounds BTTB and TP was studied by time‐resolved laser absorption spectroscopy. The laser excitation of TP leads to a long‐lived triplet state (lifetime 20–25 μsec) and a second species arising from the triplet state which cannot yet be characterized. Under laser excitation, BTTB gives a longlived transient arising from the cleavage of the peroxy bond. The short‐lived triplet state cannot be observed on the nanosecond timescale. The triplet state lifetime has been evaluated from quenching experiments and found to be about 1 ns in acetonitrile. The deactivation of the TP triplet state by BTTP was considered, the deactivation constant was found to be equal to 6.6 × 107 m−1/sec in acetonitrile. The initiation mechanism is discussed.
Progress in the chemistry of organosilicon resists
Authors: Gozdz Antoni S.
Published: April 2003

Recent developments in the chemistry of organosilicon polymers for use as oxygen plasma‐resistant imaging materials in microlithography are reviewed. Various classes of resists, grouped according to molecular structure, are described with special emphasis on properties critical in microlithographic applications. In addition, several silylation schemes involving selective silylation of a non‐silicon‐containing resist material following patternwise exposure to actinic radiation are also described.
A novel UV‐sensitive photopolymerization system with microgel matrix
Authors: Sasa Nobumasa , Yamaoka Tsuguo
Published: April 2003

A series of crosslinked microgels with quaternary ammonium ions on the surface was prepared by quaternization with N,N‐dimethylbenzylamine in the presence of microgel particles prepared by emulsion copolymerization of styrene (St), chloromethylstyrene (CMS) and divinylbenzene (DVB). Microgels with diameters in the range of 15–100 nm were successfully dispersed in organic solvents such as 2‐methoxyethanol and 2‐ethoxyethanol without an emulsifier. A photosensitive layer was formed by coating a photosensitive solution on a grained aluminum plate. The solution was comprised of the microgels, the multifunctional monomer and standard ultraviolet (UV) photoinitiators, such as 2,4‐diethyl thioxanthone (DETX)/ethyl p‐di‐ethylaminobenzoate (EPA). This gave a heterogeneous photosensitive layer which produced good polymer patterns after exposure to UV light followed by development in tap water. A typical polymer layer, consisting of the microgels (poly(styrene‐co‐N,N‐dimethylbenzylvinyl‐benzylammonium chloride‐co‐divinylbenzene)), DETX/EPA, and the multifunctional acrylate monomers, exhibited photosensitivity of 0.06 mJ/cm2 for UV light. This sensitivity is much higher than the homogeneous photopolymerization system with an analogous composition.
Synthesis and blending behavior of an oligoarylenevinylene. Design towards processable materials for LED applications
Authors: Oberski Josef , Bolle Babett , Schaper Andreas , Greiner Andreas
Published: April 2003

A bisstyrenebenzene with improved solubility can be obtained by a lateral phenyl substituent on the phenylene ring. The phenyl substituted bisstyrenebenzene (PBSB) was synthesized by Pd‐catalyzed coupling of 2,5‐dibromobiphenyl and styrene. PBSB exhibits blue fluorescence in solution. Blends of PBSB and polystyrene or polycarbonate are homogeneous over a wide concentration range of PBSB, based on differential scanning calorimetry (DSC) and scanning electron microscopy (SEM). The results were compared with the blending behavior of unsubstituted bisstyrenebenzene.
A synthetic hydrogel with thermoreversible gelation, III: an NMR study of the sol–gel transition
Authors: Yoshioka Hiroshi , Mori Yuichi , Cushman James A.
Published: April 2003

The sol–gel transition mechanism of a thermoreversible hydrogel composed of a copolymer comprising poly(N‐isopropylacrylamide) and poly(ethylene glycol) (PNIPAAm–PEG) was studied by NMR. The 1H– and 13C–NMR spectra measured on a PNIPAAm–PEG solution in 99.9% D2O showed a remarkable line width broadening of the PNIPAAm block of more than that of the PEG block, during thermally induced hydrogel formation. This result suggested that the mobility of the PNIPAAm block is more restricted than that of the PEG block during gelation. A crosslinked polymer network formation was ascertained by a sudden reduction in the spin‐lattice relaxation time (T1) of the residual HDO proton during gelation. The temperature dependency of the T1 values for the PNIPAAm and PEG blocks revealed that the microscopic condition of the PNIPAAm block in water was drastically changed during gelation, while that of the PEG block was unchanged. The experimental results from NMR supported the following gelation mechanism; that an aggregation of PNIPAAm blocks in the separate copolymers caused by hydrophobic interaction forms crosslinking points to give an infinite three‐dimensional network structure. The hydrated PEG chains in the copolymers provide the network with a swelling property in water, and prevent the aggregation from causing a macroscopic phase separation.
Charge transfer complexes and salts of ionenes
Authors: Kryszewski M. , Pȩcherz J.
Published: April 2003

A review of the synthesis and properties of ionenes is presented. Particular attention is paid to the electrical and related properties of conductive teteracyano‐p‐quinodimethane (TCNQ) complex salts of ionenes containing ammonium or sulfonium groups in the main chain and to their chemical stability. The recent work on preparation of such ionenes with inorganic and organic counterions which show interesting linear and nonlinear optical properties is also discussed.

It is shown that in the solid state ionenes act as a kind of a matrix fixing, in a chemically controlled way, positions and distribution of different kinds of counterions. Because the reaction of counterion exchange is easy in the case of ionenes it provides a convenient way to prepare a broad class of polyelectrolytes with many different properties.
Nonlinear optical properties of complexes of π‐conjugated polymers
Authors: Yang Chen‐Jen , Jenekhe Samson A. , Meth S. Jeffrey , Vanherzeele Herman
Published: April 2003

Novel host–guest complexes of conjugated polyimines with gallium chloride have been proposed and studied as an approach to enhance the third‐order nonlinear optical properties of the host conjugated polymers. The third‐order nonlinear optical susceptibility χ(3) (–3ω;ω,ω,ω) of two conjugated polyimines and their GaCl3 complexes, measured by third harmonic generation spectroscopy in the wavelength range 0.9 ∼ 2.4 μm, shows that χ(3) is enhanced in the nonresonant region, whereas it is reduced in the resonant region due to complexation. These results are explained by complexation mediated modifiction of the electronic structure of the host polymers. Two theoretical models consisting of four electronic energy levels were found to give a good description of the frequency dispersion and resonances in the χ(3) (–3ω;ω,ω,ω) spectrum of the host–guest complexes. The resulting fitting parameters were used to predict the degenerate four wave mixing χ(3) (–ω;ω,–ω,ω) spectrum for the new materials. The results of the present study suggest that host–guest complexation is a promising approach for improving the third‐order nonli‐near optical properties of conjugated polymers.
X‐ray photoelectron spectroscopic studies of charge transfer interactions in electroactive polyaniline
Authors: Tan K. L. , Kang E. T. , Neoh K. G.
Published: April 2003

Four modes of charge transfer interactions in polyaniline (PAN), viz. acid protonation, self‐doping, charge transfer interactions with organic acceptors, and charge transfer interactions with surface grafted functional polymers have been studied by X‐ray photoelectron spectroscopy (XPS). In the case of acid protonation, the protonation behavior of volatile and non‐volatile acid differs. The structures of sulfonated leucomeraldine (LM) and nigraniline (NA) are similar to those of sulfonated and self‐protonated emeraldine (EM). A substantially higher degree of charge transfer interaction with the organic acceptors is observed for EM film that has been subjected to one cycle of acid/base treatment. The charge transfer interactions with the organic acceptors have proceeded further than the pure formation of molecular complexes. Both pristine and Ar plasma or O3 pretreated EM films are susceptible to surface modifications by graft copolymerization. The protonic acid functional groups of the graft readily give rise to a self‐protonated EM surface.
Continuous, single‐component, crystalline networks in polymer matrix and their vapor doping
Authors: Jeszka Jeremiasz K.
Published: April 2003

It is shown, for the first time, that single‐component continuous networks of a low molecular weight electron acceptor additive can be grown in a polymer matrix. Such networks can be doped using, e.g., iodine vapor and converted into conductive CT complexes without losing continuity, thereby making the polymer film conductive. Polyethylene films with tetrathiotetracene networks are obtained, and their doping with iodine vapor in air is investigated by means of conductivity and spectrophotometry in the visible range. It is concluded that doping of the surface layer of the microcrystallites is sufficient to observe a significant increase in the film conductivity, which makes possible the use of such systems as sensors.