bluuebunny/crossref_metadata_2025 huggingface dataset:
Low loss HEMA/EMA copolymer waveguides with a range of wetting and optical properties
Authors: Walker D. S. , Balasubramanian K. , Reichert W. M.
Published: April 2003

Homopolymers and copolymers of optical grade hydroxyethyl methacryiate (HEMA) and ethyl methacrylate (EMA) were synthesized with bulk copolymer compositions of 0, 10, 43, 75, 86, 89, and 100 mol % HEMA. Attenuated total reflection IR (ATR‐IR) and X‐ray photoelectron (XPS) spectroscopies showed an unhydrated surface composition that varied insignificantly from the bulk. Polymer surface wettability, percent swelling of the copolymers in water, and the bulk refractive index increased with increasing HEMA content. High‐quality thin‐film integrated optical waveguides (IOW) were spun cast from copolymer solutions with propagation losses of < 1 dB/cm. Waveguide refractive indices determined from coupling angle measurements agreed closely with the bulk measurements. These results show that HEMA/EMA copolymers that form transparent films produce polymer IOWs with a range of bulk swellabilities, surface wettabilities, and optical densities. © 1993 John Wiley & Sons, Inc.
Acoustic behaviour of chromium soap solutions in benzene–dimethyl formamide mixture
Authors: Mehrotra K. N. , Jain Mamta
Published: April 2003

The critical micelle concentration and various acoustic parameters of chromium soaps (myristate, palmitate, and stearate) in a mixture of benzene and dimethyl formamide (4 : 1 v/v) have been determined by ultrasonic velocity measurements. The results showed that the ultrasonic velocity, specific acoustic impedance, molar sound velocity, and molar sound compressibility increase, while intermolecular freelength, adiabatic compressibility, and available volume decrease with increasing concentration and chain length of the soap. The results show that there is a significant interaction between soap and solvent molecules in dilute solutions and the soap molecules do not aggregate appreciably in dilute solutions. © 1993 John Wiley & Sons, Inc.
Synthesis and curing behavior of diimide–diacid‐modified saturated polyester
Authors: Lee Wen‐Fu , Chen Ienwhei , Chang Chi‐Hong
Published: April 2003

The polyester and diimide–diacid‐modified polyester prepolymer have been synthesized with different molecular weights through melt polycondensation of 1, 6‐hexanediol (HD), trimethylol propane (TMP), isophthalic acid (IPA), diimide diacid, and phthalic anhydride (PA) at various molar ratios. The prepolymers were then mixed with an equivalent phenol‐blocked TDI and /or HMDI in m‐cresol in deriving the polyester urethane varnishes. The degree of crosslinkage and thermal behavior have been investigated here. © 1993 John Wiley & Sons, Inc.
Monosize polystyrene microbeads by dispersion polymerization
Authors: Tuncel Ali , Kahraman Ridvan , Pişkin Erhan
Published: April 2003

Monosize Polystyrene microbeads were prepared by dispersion polymerization in different alcohol/ water media. Azobisisobutyronitrile and polyacrylic acid were utilized as initiator and steric stabilizer, respectively. The polymerizations were performed in three kinds of dispersion media having different polarities: isopropanol/water, 1‐butanol/water, and 2‐butanol/water. The effects of initiator and stabilizer concentrations, alcohol/water ratio, and monomer/dispersion medium ratio on the size and monodispersity of the polymeric microbeads were investigated. By dispersion polymerization, polystyrene (PS) microbeads were obtained in the size range of 1.0–4.0 μm with narrow size distribution or in the monosize form. The average size and size distribution of microbeads with increasing polarity of the dispersion medium. The average size and size distribution increased with increasing initiator concentration in all dispersion media. The increase in the stabilizer concentration in homogeneous dispersion media resulted in a decrease in average size and size distribution of the microbeads. A clear increase was observed in the average size with increasing monomer/dispersion medium ratio. Isopropanol/water dispersion medium provided monosize microbeads with higher values of monomer/dispersion medium ratio. © 1993 John Wiley & Sons, Inc.
Molecular weight dependence of the heats of hydration of some oligomeric ethylene oxides and their methoxyl derivatives
Authors: Rowe R. C. , Mckillop A. G.
Published: April 2003

The molecular weight dependence of the heat of hydration of the oligomeric ethylene oxides and their monomethoxyl and dimethoxyl derivatives has been studies using microcalorimetry. In all cases the molar heat of hydration decreased rapidly at low molecular weights reaching an asymptote at molecular weights in excess of 400. Equivalent values were obtained between oligomers and blends of the same average molecular weight. The data followed the Flory relationship relating the property of a polymer to the reciprocal of its molecular weight. However, the gradient for the oligomeric ethylene oxides was different from that of the two methoxyl derivatives suggesting a change in chain configuration. © 1993 John Wiley & Sons, Inc.
A stepwise scheme for the calculation of molecular weight distribution in condensation polymers. II. Scheme for bimolecular condensation polymers
Authors: Tung L. H.
Published: April 2003

A stepwise scheme, reported recently for the calculation of molecular weight distributions in AB monomolecular condensation polymers under the condition of unequal reactivity, has been applied to the more common AA, BB bimolecular condensation polymers. In the scheme a condensation polymerization is arbitrarily subdivided into a number of steps. The polymer obtained in one step is treated as the monomer for the next step. In each of the steps, Flory's distribution for condensation polymer under equal reactivity is used as the molecular weight distribution for that step. Reactivity variances are incorporated into the calculation through the application of weighing factors on the concentrations of the reacting molecules in each of the steps. In the bimolecular case, three types of monomers, AA, BB, and AB, must be considered for the intermediate polymerization steps. The required distribution of this trimolecular condensation under equal reactivity conditions is not available and has to be derived. As expected, the application of the scheme to bimolecular condensation is more complex but numerical calculations using the scheme should still be manageable on a desktop computer with suitable memory capacity. © 1993 John Wiley & Sons, Inc.
Polyamic acids: Thermal and microwave imidization and film properties
Authors: Kishanprasad V. S. , Gedam P. H.
Published: April 2003

Polyamic acids were synthesized from benzophenonetetracarboxylic dianhydride and di‐amines, viz., 4,4′ ‐diaminodiphenymmethane and 4,4′ ‐diaminodiphenyl ether. The course of imidization of the polyamic acids both by thermal and microwave treatments was tracked by infrared spectroscopy. The mechanical properties, namely the tensile strength and toughness of the films of polyimides with varying degree of imidization obtained by the two treatments were compared. The effect of degree of imidization of polyimide coatings on adhesion to copper substrate was also studied. Nearly 100% imidization was achieved by the thermal process, whereas the maximum imidization that could be achieved by the microwave process was about 50%. In thermal imidization, the adhesion values of the coatings slowly increased, attaining a maximum value at 80% imidization, after which there was a decrease in adhesion. © 1993 John Wiley & Sons, Inc.
Study of the thermal degradation of poly(N‐vinyl‐2‐pyrrolidone) by thermogravimetry–FTIR
Authors: Peniche Carlos , Zaldívar Dionisio , Pazos Mercedes , Páz Senen , Bulay Anna , Román Julio San
Published: April 2003

The thermal degradation of poly(N‐vinyl‐2‐pyrrolidone) (PVP) was studied by dynamic thermogravimetric analysis (TGA) in the range 200–600°C under nitrogen and oxygen atmospheres at various heating rates. The apparent activation energy of the degradative process was determined by the application of kinetic treatments, giving an average value of 242 kj/mol in N2, whereas in the presence of oxygen, two trends may be considered: At relatively low temperatures (200–400°C) and degrees of conversion, α, lower than 0.5, we obtained an average value of 199 kj/mol, whereas in the temperature interval 400–600°C with degrees of conversion higher than 0.5, the value of Ea was 306 kj/mol. Isothermal experiments carried out in N2 in the interval 350–400°C gave an average value of Ea = 231 kj/mol, in good agreement with that obtained from dynamic treatments. The FTIR spectra of the volatile compounds evolved in degradation experiments carried out in N2 as well as in the presence of oxygen suggest that PVP is thermally degraded, predominantly, by the release of the pyrrolidone side group and the subsequent decomposition of polyenic sequences. © 1993 John Wiley & Sons, Inc.
The separation of SEC curves of HDPE into flory distributions
Authors: Vickroy V. V. , Schneider H. , Abbott R. F.
Published: April 2003

A technique is reported here whereby molecular weight distribution curves from size exclusion chromatography (SEC) obtained on high‐density polyethylene (HDPE) can be deconvolved into a series of Flory‐distribution curves using a commercially available computer software system. Our analysis has shown that five to seven individual Flory distributions describe HDPE with better than a 99.9% degree of fit. We impute from this that upon taking proper precautions, we can consider these HDPE resins to be derived from at least this number of distinct catalyst sites and, furthermore, that modification of the sites will lead to a modification of the resultant resin. © 1993 John Wiley & Sons, Inc.
Modified cyclohexanone–formaldehyde and acetophenone–formaldehyde resins
Authors: Kizilcan Nilgün , Galioğlu Oya , Akar Ahmet
Published: April 2003

Preparation of in situ‐modified cyclohexanone‐formaldehyde and acetophenone‐formaldehyde resins with compounds such as diphenols, melamine, and p‐toluene sulfonamide were studied. Modification of acetophenone‐formaldehyde resins with hydroxylamine, semicarbazide, phenylhydrazine, phthalic anhydride, and acetic anhydride was also studied. Melting points, solubilities in organic solvents, and FTIR and NMR spectra of modified resins were determined. © 1993 John Wiley & Sons, Inc.
Preparation and cured properties of novel cycloaliphatic epoxy resins
Authors: Tokizawa Makoto , Okada Hiroyoshi , Wakabayashi Nobukatsu , Kimura Tomiaki , Fukutani Hideo
Published: April 2003

Preparation and characterization of novel cycloaliphatic epoxy resins, which are derived from octadienyl compounds, were studied. From a model peracetic acid epoxidation reaction using 2,7‐octadienyl acetate‐1, the structure of the liquid resins is estimated to be mainly terminal epoxides and some amount of inner epoxide depending on the epoxide content. The epoxy resins offer lower toxicity and lower vapor pressure. The reactivity of the resin with acid anhydrides is moderate but faster than that of traditional cyclohexane epoxide‐type resins and slower than that of the glycidyl ester‐type resins. This reactivity was also examined using model compounds. The heat deflection temperature of the hexahydro‐phthalic anhydride‐cured resins is shown to be directly proportional to the number of epoxy groups in the molecules. The flexural strength of the cured resins is nearly equivalent to that of the commercial resins, although the flexural elongation of the resins is larger than that of the rigid cyclohexane epoxide‐type resins. The thermal stability of the cured resins is comparable to typical rigid cycloaliphatic resins; furthermore, high water resistance of the cured resins is suggested to be attributed to the hydrophobic character of the C8 chain by cross‐linking. © 1993 John Wiley & Sons, Inc.
Biocidal polymers active by contact. III. Ageing of biocidal polyurethane coatings in water
Authors: Nurdin N. , Helary G. , Sauvet G.
Published: April 2003

Polyurethane coatings prepared from hydroxytelechelic polybutadiene with pendant qua‐ternary ammonium salts (QAS) are able to kill microorganisms, these biocidal polymers were submitted to various ageing conditions. The activity remained constant after exposure to a very high number of bacteria (Escherichia coli). Nevertheless immersion in water caused a slow decrease of activity with time whatever the QAS examined (N+R2R′ with R = Me or Bu and R′ = n‐octyl to n‐hexadecyl). The phenomenon can be analysed in two stages. The first one, short (5–10 days) and limited, is due to the diffusion of a water‐soluble synthesis residue. At the end of this period, the samples are still active and the activity is only due to a contact polymer‐bacteria. The second stage is much slower and is accompanied by a transformation of QAS in amine. This is attributed to an equilibrium between QAS, amine, and alkyl bromide slowly shifted toward the formation of amine because of a weak solubility of alkyl bromide in water. Increasing the lipophilicity and bulkiness of the QAS substituents improves the durability of the biocidal activity. Some samples still exhibit a good activity after more than 1 year of ageing in harsh conditions. © 1993 John Wiley & Sons, Inc.
Structure‐property relationships in polyurethane‐poly(styrene‐co‐acrylonitrile) blends
Authors: Z̆erjal B. , Musil V. , S̆mit I. , Jelčić Z̆. , Malavas̆Ic̆ T.
Published: April 2003

Blends of Thermoplastic polyurethane (TPU) and poly(styrene‐co‐acrylonitrile) (SAN) (34% acrylonitrile and 24% acrylonitrile) and polyurethane ionomer (PUI) with SAN (34% acrylonitrile) were prepared in the melt. The structural properties and morphology of the blends were investigated. TPU and SAN blends were immiscible in the composition range 30–70 wt % of TPU or SAN. In TPU‐rich blends, SAN propagates the separation of hard and soft segements in TPU. In SAN‐rich blends, the interaction stage depends on acrylonitrile contents. SEM measurements showed that the blends of TPU/SAN were fine dispersions and clearly showed a continuous and disperse phase, whereas the morphology of the PUI/SAN blends were different. © 1993 John Wiley & Sons, Inc.
Swelling properties of cross‐linked maxillofacial elastomers
Authors: Andreopoulos A. G. , Polyzois G. L. , Evangelatou M.
Published: April 2003

Silicone specimens cross‐linked with various amounts of cross‐linking agent were studied in terms of mechanical and swelling behavior. The measured tensile modulus allowed calculation of the average molecular weight between cross‐links (M̄c). Equilibrium swelling data were also used, in combination with the determined M̄c values, to obtain the interaction parameter χ of various silicone–solvent systems at 25°C. Part of this work was also the study of swelling of silicone samples with varying network density in selected solvents such as toluene, ethyl acetate, n‐butanol, and methyl ethyl ketone. © 1993 John Wiley & Sons, Inc.
Poly(vinyl alcohol)/poly(acrylic acid) blends: Miscibility studies by DSC and characterization of their thermally induced hydrogels
Authors: Vázquez‐Torres H. , Cauich‐Rodríguez J. V. , Cruz‐Ramos C. A.
Published: April 2003

Binary blends of poly(vinyl alcohol) (PVA) with poly(acrylic acid) (PAA) and polyacrylamide (PAAm) were characterized by differential scanning calorimetry (DSC), thermal gravimetric analysis (TGA), and infrared spectroscopy (IR). Molecular weight, blend composition, and heating time at 150°C were the variables used. Results obtained by DSC indicated that PAA/PVA blends are miscible in the full range of composition. Similarly, TGA traces showed that thermal stability was higher for blends than for pure polymers. Blends of PVA with high molecular weight PAA exhibited a hydrogel behavior after drying at relatively low temperature (100°C), whereas blends containing low molecular weight PAA behaved as hydrogels only after they were heated at 150°C. Hydrogel character was increased for these two PVA/PAA blends with the heating time at higher temperature (150°C). IR spectra revealed that esterification took place in these blends after thermally treated at this temperature. In contrast, addition of glyoxal in combination with heating was necessary to produce hydrogels from PAAm/PVA blends. Furthermore, the crosslinking degree of these hydrogels was estimated from their absorbency values by applying the Flory–Rehner equation. © 1993 John Wiley & Sons, Inc.
Characterization of fractionated LLDPE by DSC, FTIR, and SEC
Authors: Neves Claudio J. , Monteiro Elisabeth , Habert Alberto C.
Published: April 2003

Samples of ethylene / 1‐butene copolymer were fractionated according to chemical composition by preparative temperature rising elution fractionation (TREF) in the range of 27–117°C. The resulting fractions were submitted to DSC, SEC, and FTIR analyses. For each fraction, the methyl group content, melting temperature, crystallinity, average molecular weight, and molecular weight distribution were determined. From the results, it was found that the melting tempreature increased linearly with the extraction temperature in the range of low temperatures and remained constant at high temperatures. Similar behavior was observed for crystallinity. It was also verified that the first two fractions showed a higher degree of supercooling than the fractions extracted at higher temperatures. These results were explained by the existence of a heterogeneous intermolecular distribution of comonomer molecules. In a general way, the comonomer units, present at higher concentrations in the low temperature fractions, tended to destroy the crystalline order of the polymer. © 1993 John Wiley & Sons, Inc.
Conducting diblock copolymers with lonic complex/insulator lamellar microdomains
Authors: Ishizu Koji , Yamada Yoshikuni , Saito Reiko
Published: April 2003

Poly(styrene‐b‐2‐vinylpyridine) diblock copolymer films with horizontally oriented lamellar microdomains were obtained by the casting method. Poly(2‐vinylpyridine) (P2VP) microdomains were not only quaternized, but were also crosslinked with 1,4‐diiodobutane vapor. Subsequently, ionic complex phases were constructed by an ion‐exchange reaction of quaternized P2VP phases with lithium perchlorate. The element (chlorine and iodine atoms) distributions on the vertical section of the modified films were measured by means of an energy dispersive X‐ray spectrometer. These materials had highly anisotropic conductivity with approximately 6 orders of magnitude. © 1993 John Wiley & Sons, Inc.
Crystal size and minimum enthalpy of crossbreed silk fibers annealed at various temperatures
Authors: Somashekar R. , Urs R. Gopal Krishne
Published: April 2003

Wide‐angle X‐ray diffraction studies of crossbreed silk fibers and fibers annealed at various temperatures for different periods of time were carried out to evaluate the crystal size and lattice distortion parameters, as these determine the properties of silk fibers. Also, minimum enthalpy for the formation of these fibers has been estimated and compared. © 1993 John Wiley & Sons, Inc.
Determination of diffusion coefficient of water in polymer films by TGA
Authors: Ogawa Toshio , Nagata Toshio , Hamada Yoshikazu
Published: April 2003

This study is concerned with the determination of the diffusion coefficient of water into polymer films using a thermogravimetric analyzer (TGA). First, the sample film in the sample chamber was dried completely by N2 gas supplied by a cylinder. Next, the mixture of air and N2 gas having a given humidity was introduced into the sample chamber of the TGA. The sample weight was recorded as a function of time. The diffusion coefficient was calculated from the initial slope of weight vs. the square root of the time curve. The results were consistent with those obtained using Prager and Long's method. © 1993 John Wiley & Sons, Inc.
New method for measuring poisson's ratio in polymer gels
Authors: Li Yong , Hu Zhibing , Li Chunfang
Published: April 2003

A new method for measuring the Poisson's ratio of polymer gels has been proposed and has been experimentally demonstrated. The method is based on different swelling behaviors of free and constrained gels. The Poisson's ratio of polyacrylamide gel, as a function of crosslinker concentration, has been measured using this method and has been found to be sensitive to the amount of polymerization initiator. The results are compared with results determined by other methods. © 1993 John Wiley & Sons, Inc.
Development of a new advanced process for manufacturing polyacetal resins. Part III. End‐capping during polymerization for manufacturing acetal homopolymer and copolymer
Authors: Masamoto J. , Matsuzaki K. , Iwaisako T. , Yoshida K. , Kagawa K. , Nagahara H.
Published: April 2003

Conventionally, acetal homopolymer or copolymer is obtained by the polymerization of formaldehyde or trioxane, following the end‐capping using acetic anhydride or unzipping of the unstable polymer end fraction. First, Asahi Chemical developed a new process to obtain an end‐capped polymer during polymerization of highly purified formaldehyde using acetic anhydride as the chain‐transfer agent. Use of highly purified formaldehyde and endcapping during polymerization using acetic anhydride as a chain‐transfer agent or an endcapping agent will provide a simple process for manufacturing acetal homopolymer. The polymerization mechanism was confirmed by infrared spectroscopy analysis and proton NMR analysis of the polymer obtained. Second, for the acetal copolymer, purified trioxane was copolymerized with ethylene oxide in the presence of methylal, which gave an endcapped polymer with high thermal stability. Two new intermediates from the initiation reaction of the copolymerization, 1,3,5,7‐tetraoxacyclononane (TOCN) and 1,3,5,7,10‐pentaoxacyclododecane (POCD), were isolated and a new initiation mechanism was proposed. © 1993 John Wiley & Sons, Inc.
Mechanical scission of perfluoropolyethers
Authors: Karis T. E. , Novotny V. J. , Johnson R. D.
Published: April 2003

Mechanical scission of two typical perfluoropolyethers was investigated: Y, a copolymer of CF(CF3)CF2O, CF2O, and CF(CF3)O, and Z, a copolymer of (CF2)nO, with n = 1,2,3,4. Undiluted polymers were subjected to prolonged shearing in a media mill with ZrO2 particles. A chemical extraction of the polar ZrO2 particles was carried out to collect adsorbed polar scission products. Mechanochemical scission products from both the Y and Z fluorocarbon polymers were identified by 19F‐NMR. A significant amount of CF3CO2− was present after the milling and the primary functional groups formed at scissioned chain ends were CO. A hydrodynamic expression was derived and the maximum extension rate was estimated to be in the range of 5 × 106 s−1. Initial degrees of polymerization were between 20 and 200, well below levels for which flow‐induced scission is expected to occur. Final degrees of polymerization were less than 10, and the scission was noncentral and nonrandom in both polymers. © 1993 John Wiley & Sons, Inc.
Inhibition of bovine serum albumin adsorption by poly(ethylene glycol) soft segment in biodegradable poly(ethylene glycol)/poly(L‐lactide) copolymers
Authors: Hu David Shiaw‐Guang , Liu Hsin‐Jiant , Pan I‐Lung
Published: April 2003

The objective of this study was to investigate the effects of the incorporation of ether linkages into polylactide (PLLA) chains and the time of biodegradation on the behavior of protein adsorption. The content of poly(ethylene glycol) (PEG) in PLLA/PEG copolymers is from 4.4 to 18.3 wt %, and the length of the PEG soft segment is 1000, 2000, and 6000 daltons. The bovine serum albumin (BSA) adsorption onto the biodegradable PLLA/PEG copolymers was carried out using ultraviolet spectroscopy. The surface tension of PLLA and PLLA/PEG was measured using a contact angle. The data show that the incorporation of PEG segments makes the copolymer more polar and, therefore, leads to a reduction of protein adsorption. As the hydrolysis of polymers proceeds, both PLLA and PLLA/PEG turn out to be more polar. However, the initial compositions of degraded PLLA/PEG have a weak influence on the protein adsorption onto its hydrolyzed surface with a substantially long duration of hydrolysis. This phenomenon is attributed to the hydrophobic interaction between polar PLLA/PEG and BSA. © 1993 John Wiley & Sons, Inc.
Investigation of the properties of polyacrylamide‐polyaniline composite and its application as a battery electrode
Authors: Bhat N. V. , Joshi N. V.
Published: April 2003

The composite films of polyacrylamide and polyaniline were prepared by polymerizing aniline using ammonium persulfate as an initiator in an aqueous solution containing polyacrylamide. A film was then cast from this solution. The structural, dynamic mechanical, electrical, and thermal properties of these films have been studied. The infrared spectrum shows the presence of polyacrylamide as well as polyaniline in the composite film. The thermal analysis shows that the composite degrades slower than does the polyacrylamide alone. The dynamic mechanical analysis indicates that there is an increase in the glass transition temperature after the composite formation. The electrical conductivity has been found to increase by more than eight orders of magnitude. These composite films have also been suitably used as electrodes in secondary batteries. © 1993 John Wiley & Sons, Inc.
Photoconductivity and photovoltaic effect of charge‐transfer complex of poly[4‐phenyl‐2,6‐(p‐phenoxy) quinoline] and 2,3‐dichloro‐5,6‐dicyano‐1,4‐benzoquinone
Authors: Choi Donghoon , Lee Eun Ju , Kim Kyeong‐Ah , Park Soo Young , Kim Nakjoong
Published: April 2003

A new polymer containing a heterocyclic quinoline unit in the main chain, poly[4‐phenyl‐2,6‐(p‐phenoxy) quinoline] (PQ), was synthesized by an acid‐catalyzed self‐condensation reaction. We have found that PQ, which is generally a good insulator itself, can show photoconductivity when doped with an electron acceptor. From the UV‐VIS absorption spectra, we found that PQ can form a charge‐transfer (CT) complex with an electron acceptor, 2,3‐dichloro‐5,6‐dicyano‐1,4‐benzoquinone (DDQ). The CT complex of the PQ‐DDQ mixture showed distinct photoconductivity. Employing the DDQ composition ranging from 5 to 10 wt %, the ratio of dark and photoconductivity was calculated to be about 1 : 100 at an applied electric field of 105 V/cm. Additionally, the bilayer sample of PQ/DDQ exhibited a significant photovoltaic effect. The photovoltaic current increased with increasing photointensity. The open‐circuit voltage was measured ranging from 0.4 to 0.7 V and the photovoltaic conversion efficiency was calculated to be 10−3−10−2%. The PQ film treated with DDQ vapor showed a relatively higher photovoltaic effect than that of the sample treated with DDQ solution. © 1993 John Wiley & Sons, Inc.
Water‐sorption and transport properties of Nafion 117 H
Authors: Morris David R. , Sun Xiaodong
Published: April 2003

The density and dimensional changes of Nafion 117 H have been measured as a function of the water content. Swelling of Nafion commences at N (≡ mol ratio water to hydrogen ion) ∼ 1.9. Some anisotropy of dimensional changes was observed. Water‐sorption isotherms obey Henry's Law with a nonzero intercept indicating some water retention. The diffusion coefficient of water in Nafion and the electrical conductivity of Nafion are strong functions of the water content. The latter is exploited for the development of a humidity sensor. © 1993 John Wiley & Sons, Inc.
Preparation and thermal kinetics of poly(imide‐siloxanes)
Authors: Moon Yoon Duk , Lee Young Moo
Published: April 2003

Thermoplastic poly(imide‐siloxanes) (PISILs) were synthesized from hexafluoroisopro‐pylidene‐2,2‐bis(phthalic acid anhydride) (6FDA), 3,3',4,4'‐benzophenonetetracarboxylic dianhydride (BTDA), pyromellitic dianhydride (PMDA), and amine‐terminated poly(dimethyl siloxanes) (PDMS) having different molecular weights. Glass transition temperatures of fully cured PISILs ranged from −91 to −48°C. Various kinetic parameters for the thermal decomposition reaction of PISILs were examined by dynamic thermogravimetric analysis (DTGA) at four different heating rates. The degradation path was a kinetically first‐order reaction for PISILs (abbreviated 6FDA‐860, BTDA‐860, and PMDA‐860, respectively) from 6FDA, BTDA, PMDA, and PDMS (Mn = 860 g/mol). The reaction rate constant times the half‐life (k × t1/2) was approximately 0.693. The activation energies for decomposition were in the following order: 6FDA‐860 <BTDA‐860 <PMDA‐860. The lifetime of the highest heat‐resistant PMDA‐860 at about 200°C and at the conversion level of 10% was 6.5 × 105 h or 74 years. Other kinetic factors were also calculated. © 1993 John Wiley & Sons, Inc.
Microstructural effects and the toughening of thermoplastic modified epoxy resins
Authors: Min B.‐G. , Stachurski Z. H. , Hodgkin J. H.
Published: April 2003

We have studied an epoxy resin formulation consisting of the diglycidyl ether of bisphenol‐A (DGEBA), modified with phenolic hydroxyl‐terminated polysulfone (PSF) and cured with an aromatic amine curing agent, diaminodiphenyl sulfone (DDS). A range of microstructures and fracture properties have been obtained by controlling the formulation cure conditions (cure temperature and cure cycle in an isothermal mode). The chemical conversion of the cured resins has been monitored by near‐infrared spectroscopy (NIR). Although only a single material formulation was used, three distinct types of microstructure were identified by scanning electron microscope (SEM) observations on samples prepared at different cure temperatures. Surprisingly, the thermal and fracture properties of the cured samples did not vary noticeably, in spite of the significant microstructure variations. The consistency of these fracture toughness results with cure temperature changes was an unexpected result in the light of our earlier observations of a strong dependence of fracture toughness on cure temperature in neat resin systems. The difference in behavior between neat and modified resins reveals that the fracture toughness of the latter is dependent on a combination of the microstructure and the matrix resin properties. This hypothesis was also supported by an observation of high fracture thoughness in a sample cured in a two‐step process, which we believe is due to the optimum microstructure and matrix resin properties, being achieved separately during precure and postcure, respectively. The increase in fracture toughness values caused by the modification (ΔGIC) was calculated from the fracture toughness values of neat and modified resins, prepared under the same cure conditions, using a proposed theoretical equation. © 1993 John Wiley & Sons, Inc.
Crosslinkable, nonlinear optical copolymers: Processing, corona poling, and second harmonic generation studies
Authors: Kawatsuki Nobuhiro , Schmidt Hans‐Werner , Pakbaz Khashayer
Published: April 2003

Polymethacrylate copolymers, containing nonlinear optically active 4′‐dialkylamino‐4‐nitroazobenzene side groups and crosslinkable 2‐butenyl side groups were synthesized and characterized. Films of these copolymers can be thermally crosslinked at elevated temperatures and photochemically crosslinked by exposure with UV light. Both methods allow the control of the crosslinking density. A precrosslinking step, prior to the corona‐poling step, can be applied to optimize alignment and relaxation of the chromophores. During corona‐poling, the temperature dependence of the second harmonic generation (SHG) of an Nd‐YAG laser (1.064 μm) was studied for films with different degrees of precrosslinking. Depending on the conditions of precrosslinking, the SHG signal intensity and the alignment stability can be maximized. © 1993 John Wiley & Sons, Inc.
Solid‐phase modification of chitosan hydrogel membranes and permeability properties of modified chitosan membranes
Authors: Kubota Naoji , Kikuchi Yasuo , Mizuhara Yukako , Ishihara Tatsumi , Takita Yusaku
Published: April 2003

A novel preparation method for modified chitosan membranes was developed. Chitosan hydrogel membranes were prepared by immersing an aqueous acetic acid solution of chitosan in KOH solution and modified with 3,3′‐dithiodipropionic acid (DTPA), which has a functional group that causes the thiol ⟷ disulfide transition through a redox reaction. It was smoothly modified with DTPA even in a solid‐phase modification when carbodiimides were used as the condensing reagents. The chitosan membrane modified with DTPA was reduced with tri‐n‐butyl phosphine (MSH membrane) and then oxidized with iodine (MSS membrane). Permeabilities of KCl, sucrose, and urea through these modified chitosan membranes were investigated. The permeability of urea was quite high and followed by KCl and sucrose in that order. The permeabilities of KCl and sucrose through the MSS membrane showed a decrease compared to those through the MSH membrane. The thiol ⟷ disulfide transition was responsible for changes in the permeabilities of KCl and sucrose. The permeability of urea was almost the same for both membrane systems, i.e., permeation of urea was not affected by the thiol ⟷ disulfide transition, probably due to the break of hydrogen bonding in the membranes. © 1993 John Wiley & Sons, Inc.
A compatibility study of waste poly(ethylene‐terephthalate) with poly(vinylchloride)
Authors: Akovali G. , Aslan S.
Published: April 2003

Mixtures of PET and PVC were prepared in three different compositions by a solution blending technique. A plasma surface modification method was applied to PET powder surfaces in order to enhance the miscibility of both components because of their mutual insolubility. The intrinsic viscosities of blends were measured in a phenol/tetrachloroethanemixed solvent system. The degree of compatibility of blends was characterized by the use of the parameter Δb, as derived by Krigbaum and Wall. © 1993 John Wiley & Sons, Inc.
Tetrabutylammonium benzoate‐initiated polymerization of propylene oxide
Authors: Chen Xuemin , Van De Mark M. R.
Published: April 2003

The polymerization of propylene oxide by the benzoate anion was aided through the use of the tetrabutylammonium counterion. The effect of the tetrabutylammonium ion was to increase the solubility of the salt and to increase the ion separation. The polymerization was carried out in a pressure reactor at temperatures from 40 to 108°C, producing polymer yields of 2–78%. The study addressed the general effects of solvent, temperature, and ratio of initiator to monomer. © 1993 John Wiley & Sons, Inc.
Star‐shaped condensation polymers: Synthesis, characterization, and blend properties
Authors: Gorda K. R. , Peiffer D. G.
Published: April 2003

A series of ϵ‐caprolactone linear and star polymers were prepared and characterized in order to determine the effect of the star architecture (i.e., star number and arm length) on the morphology of these semicrystalline polymers. A spherulitic morphology was found in all the polymers investigated. However, for six arm stars containing low degrees of polymerization, it appears that the star core dominates its morphological behavior (presumably due to its relatively high volume fraction). The star core effects, however, are markedly reduced in star polymers were the arms contain higher degrees of polymerization.

The impact of the star core was further explored by investigating several poly(ϵ‐caprolactone) (PCL):styrene–acrylontrile copolymers (SAN) blends. In all instances, miscible blends were the result because a single compositionally dependent glass‐transition temperature (Tg) was observed. A moderate elevation in the Tg of the star‐shaped polymers does occur, however, compared to their linear analogs. This effect is presumably due to the inability of the SAN chains to completely mix with all segments of star structure. © 1993 John Wiley & Sons, Inc.
Swelling of poly[methacrylic acid‐co‐poly(oxytetramethylene) dimethacrylate]s
Authors: Kojima Takakazu , Masuda Kazuhisa , Taco Kazuaki
Published: April 2003

An equation of swelling equilibrium is derived for crosslinked copolymer including incomplete network structures, to be applied to the swelling data on copolymer of poly(oxytetramethylene) dimethacrylate (POTMDM) with methacrylic acid (MAA). Poly(MAA‐co‐POTMDM)s with various monomer contents, is prepared by copolymerization in N,N‐dimethylformamide (DMF). The equation shows good applicability to the swelling behaviors of poly(MAA‐co‐POTMDM) for tetrahydrofuran (THF) and DMF systems. A difference in polymer‐polymer interaction parameter between THF and DMF systems, derived from the results of curve fitting is explained in terms of dependence of polymer‐solvent interaction parameter on crosslink density. © I993 John Wiley & Sons, Inc.
Alkaline PF resins linear extension by urea condensation with hydroxybenzylalcohol groups
Authors: Pizzi A. , Stephanou A. , Antunes I. , De Beer G.
Published: April 2003

The linear increase of phenol–formaldehyde (PF) resins by reaction under alkaline conditions of the ortho‐ and para‐hydroxybenzylalcohol groups of the PF resin with small molar percentages of urea was followed by model compounds reactions. Apparent rate constants of the reactions of urea with o‐and p‐hydroxybenzylalcohols were obtained. Both the ortho‐ and para‐isomerides appeared to react faster with urea than for their autocondensation. The ortho‐isomeride appears to react faster with urea than the para‐isomeride, under alkaline conditions. Autocondensation under alkaline conditions instead appears to be faster in the case of p‐hydroxybenzylalcohol. The properties of PF resins prepared with the addition of small amounts of urea appear to be consistent with what is observed in the model compounds reactions: Their gel times become faster and viscosity increases with increasing amounts of urea addition. © 1993 John Wiley & Sons, Inc.
Mass transfer effects in emulsion polymerization systems. I. Diffusional behavior of chain transfer agents in the emulsion polymerization of styrene
Authors: Nomura M. , Suzuki H. , Tokunaga H. , Fujita K.
Published: April 2003

On the basis of the so‐called two‐films theory for mass transfer, a mathematical model for transfer of chain transfer agents from monomer droplets to polymer particles, where chain transfer agent molecules are consumed by the chain transfer reaction, is developed for an emulsion polymerization system. It is shown by the model that the concentration of chain transfer agent in the polymer particles during the polymerization is decreased to a value much less than that which would be attained if thermodynamic equilibrium for chain transfer agent were reached between the polymer particles and the monomer droplets, due mainly to the resistance to transfer of chain transfer agent molecules across the diffusion films at the interface between the monomer droplets and the water phase. The validity and utility of the model developed for predicting the diffusion and consumption rates for chain transfer agent are demonstrated experimentally using five normal aliphatic mercaptans from n‐C7 to n‐C12 as chain transfer agents in the seeded emulsion polymerization of styrene. © 1994 John Wiley & Sons, Inc.
Critical parameters for heat transfer and chemical reactions in thermosetting materials
Authors: Gebart B. Rikard
Published: April 2003

The equations of one‐dimensional heat transfer with chemical reactions with isothermal initial conditions and constant wall temperature are solved approximately for all types of kinetic models. The general solution is valid for low exothermal peaks and it is characterized explicitly by two dimensionless parameters. The first parameter is the ratio between the time scale for heat conduction and that for the chemical reaction; the second parameter is the ratio between the processing temperature and the adiabatic temperature rise. The number of additional parameters depends on the particular choice of kinetic model. The maximum temperature in the solution always occur at the center line and its magnitude is proportional to the maximum rate of reaction. For a second‐order autocatalytic kinetic model, closed from results can be obtained. The solution is in this case characterized by two additional dimensionless parameters. The analytical solution agrees excellently with numerical solutions for small exothermal temperature peaks (<10% of the adiabatic temperature rise), but the qualitative agreement is very good also for cases with significant exothermal peaks. The general solution can be used also for the case when the kinetic model is unknown and only experimental DSC results are available. © 1994 John Wiley & Sons, Inc.
The interaction of sulfenamide accelerators with sulfur, ZNO, and stearic acid in the absence of rubber
Authors: Gradwell M. H. S. , Mcgill W. J.
Published: April 2003

The interaction of sulfur, ZnO, stearic acid, and the three sulfenamide accelerators N‐cyclohexylbenzothiazole sulfenamide (CBS), 2‐(4‐morpholinothio) benzothiazole (MOR), and 2‐t‐butylaminobenzothiazole sulfenamide (TBBS) were investigated by differential scanning calorimetry in the absence of rubber. In the presence of sulfur, the same product spectrum is formed as in its absence, but at lower temperatures. Thus, CBS gives N‐cyclohexylamino‐2‐benzothiazole polysulfides (CBP), 2‐bisbenzothiazole‐2,2′‐disulfide (MBTS), 2‐bisbenzothiazole‐2,2′‐polysulfides (MBTP), and 2‐bisbenzothiazole‐2,2′‐monosulfide (MBTP), 2‐mercaptobenzothiazole (MBT), and 2‐N‐cyclohexylaminobenzothiazole (CB). In the presence of sulfur, the amount of polysulfides formed initially is higher but the polysulfides are unstable, and on prolonged heating, only MBT and CB remain. MOR and TBBS form analogous product spectra. The sulfenamides do not react with ZnO or zinc stearate. The MBT–amine complex prevents MBT, formed on decomposition, from reacting to give zinc mercaptobenzothiazole (ZHBT). Reaction mechanisms are proposed to account for the formation of the products. © 1994 John Wiley & Sons, Inc.
Effect of viscosity ratio and processing conditions on the morphology of blends of liquid crystalline polymer and polypropylene
Authors: Heino Markku T. , Hietaoja Pirjo T. , Vainio Tommi P. , Seppälä Jukka V.
Published: April 2003

The effect of viscosity ratio and processing conditions on LCP/PP blend morphology was studied. The viscosity ratio (ηLCP/ηPP) was varied from 0.1 to 3.6 by using five different polypropylene grades as the matrix and two LCPs as the dispersed phase (20 wt %). The most spontaneous fiber formation was achieved when the viscosity ratio was between 0.5 and 1. In addition to shear forces, elongational forces are important in achieving a highly fibrillar structure and significant mechanical reinforcement. The lubricating effect induced by the low viscosity of LCP was most pronounced for the blends exhibiting a fibrillar morphology. The morphologies of blends produced by different mixing equipment differed only slightly. The greatest variation in the mixing efficiency was found for blends whose components had totally dissimilar melt viscosities. The slight differences in morphology due to melt blending in dissimilar equipment were decreased after injection molding, whereas the differences in morphology due to dissimilar viscosity ratios were still evident in the injection molded blends. Thus, the viscosity ratio at processing in the actual processing conditions is of great importance. © 1994 John Wiley & Sons, Inc.
Polymer dissolution. I. On the dissolution behavior of copolymers of methyl methacrylate and methacrylic acid
Authors: Reinhardt M. , Pfeiffer K. , Lorkowski H.‐J.
Published: April 2003

Copolymers of methyl methacrylate with methacrylic acid [P(MMA/MA)] are interesting resist materials for microlithography. At moderate baking temperatures, these copolymers undergo an intramolecular cyclization, yielding terpolymers containing anhydride moieties. This process has striking consequences for the dissolution behavior and results in higher ketone solubilities. The dissolution rates in methyl ethyl ketone (MEK) and in mixtures with ethyl glycol (EG) correlate in an Arrhenius‐like manner with the reciprocal baking temperatures. Two distinct temperature ranges with different slopes between 130–180°C and 180–230°C are found. This is in good agreement with other findings, indicating a different mechanism of anhydride formation in these temperature regions. The activation energies for the dissolution of P(MMA/MA) in EG or EG/MEK mixtures are about 17 kcal/mol and those of the thermally treated material in MEK or MEK/EG or mixtures of MEK with methyl isobutyl ketone (MIBK) are in the range of 20–30 kcal/mol. For the investigation of the Mn dependence, γ‐irradiated probes of the copolymer were used. We obtained the usual exponential Mn dependence with an exponent of 0.7–0.8 in MIBK and 0.3–0.4 in EG. Our findings are in agreement with a “relaxation‐controlled” dissolution behavior, especially for the anhydride‐containing terpolymer. No residual layers or pronounced inhibition periods indicative for gel‐layer formation, however, could be found. We suggest a normal dissolution process with a very small gel layer. For the copolymer in an alcohol‐containing solvent, a stress‐driven dissolution behaviour is more likely. © 1994 John Wiley & Sons, Inc.
Radiochemical graft copolymerization of methacrylonitrile and binary mixture of methacrylonitrile with 4‐vinylpyridine onto isotactic polypropylene fiber
Authors: Kaur Inderjeet , Barsola Raghuvir , Misra B. N.
Published: April 2003

Graft copolymerization of methacrylonitrile (MAN) and its binary mixture with 4‐vinylpyridine (4‐VP) onto isotactic polypropylene (IPP) fiber has been studied in aqueous medium by the preirradiation method. Optimum conditions for obtaining the maximum percentage of grafting have been evaluated. Rate of grafting (Rg) has been determined as a function of total initial monomer concentration. The graft copolymers are characterized by IR spectroscopy, by thermogravimetric analysis, and by isolating the polymer from the graft copolymer. The effect of MAN, an acceptor monomer, on percentage of grafting of 4‐VP, a donor monomer, has been discussed in the light of the mechanism proposed for grafting by the radiochemical method. © 1994 John Wiley & Sons, Inc.
Investigation of ethylene/1‐octene copolymerization models by carbon‐13 NMR
Authors: Bailey A. L. , Kale L. T. , Tchir W. J.
Published: April 2003

Statistical reaction models have been used to fit C‐NMR spectra for ethylene/1‐octene copolymers and to describe the polymerization reaction probabilities. Ten models ranging in complexity from a one‐site Bernoulli probability to multiple site second‐order Markov systems were studied. Model parameters were determined by fitting the experimental integrations of replicated spectra using a maximum likelihood method. The best fit to the experimental NMR spectra was obtained with a two‐site model, one site producing mainly high‐density polymer following a Bernoulli probability model, while the second site allows more incorporation of octene following a chain‐end controlled probability described by first‐order Markov statistics. © 1994 John Wiley & Sons, Inc.
Preparation and application of low molecular weight poly(vinyl chloride). IV. Preparation and characteristics of poly(vinyl chloride) with broad molecular weight distribution
Authors: Yamamoto Kikuo , Maehara Takashi , Mitani Katsuo , Mizutani Yukio
Published: April 2003

Poly(vinyl chloride) (PVC) with a broad molecular weight distribution (BMD‐PVC) was prepared by suspension polymerization in the presence of PVC with relatively lower molecular weight (LMW‐PVC), which was prepared by suspension polymerization in the presence of 2‐mercaptoethanol as a chain‐transfer agent. It is elucidated using porosity measurement, scanning electron microscopy (SEM), and energy dispersion X‐ray microscopy (EDXM) that the resultant BMD‐PVC grains have an interesting internal structure at the level of primary particles. Discoloration time and fusion time of the BMD‐PVC was studied. Discoloration time and fusion time of BMD‐PVC is particularly dependent on the polymerization degree (Pw) of LMW‐PVC and LMW‐PVC content in the BMD‐PVC samples. © 1994 John Wiley & Sons, Inc.