bluuebunny/crossref_metadata_2025 huggingface dataset:
Synthesis and photoinitiated cationic polymerization of 1,2,3‐tris(1‐propenoxy) propane
Authors: Crivello J. V. , Bratslavsky S. A.
Published: April 2003

The synthesis of 1,2,3‐tris (1‐propenoxy) propane (GTPE) was carried out by the rearrangement of 1,2,3‐tris(2‐propenoxy) propane (glycerol triallyl ether, GTAE) and the Z: E isomer composition of the GTPE was determined using gas chromatography and 1HNMR. The photoinitiated cationic polymerization of the GTPE was studied using realtime infrared spectroscopy (RTIR). Employing the data from these studies, rates of polymerization for the respective E and Z propenyl ether double bonds were calculated. The rate of incorporation of Z‐double bonds of GTPE into the crosslinked polymer matrix is 1.6 times that of E‐double bonds. The effects of oxygen and several other free radical polymerization inhibitors were investigated. An increase in the photogel time and decrease of the gel‐content in the presence of these inhibitors implicates the involvement of free radicals in the process of the generation of propagating cationic centers when diaryliodonium salt cationic photoinitiators are used. © 1994 John Wiley & Sons, Inc.
The effects of substituent size and molecular weight on the liquid crystalline properties of poly(2‐alkyl‐1,4‐phenylene terephthalate)s
Authors: Majnusz Jerzy , Lenz Robert W.
Published: April 2003

A series of low molecular weight, thermotropic poly(2‐alkyl‐1,4‐phenylene terephthalate)s was prepared by the solution polycondensation reaction of terephthaloyl chloride and alkylhydroquinones containing n‐alkyl substituents of increasing size from methyl to dodecyl. Samples of the low molecular weight polymers so obtained were also further polycondensed in the solid state to obtain high molecular weight polymers. The liquid crystalline phase behaviors and textures were determined, and the effects of polymer structure and molecular weight on these properties are discussed. All of the polymers obtained formed thermotropic, nematic mesophases, which were less stable for the lower molecular weight polymers, as expected, than were the mesophases formed by the higher molecular weight polymers. © 1994 John Wiley & Sons, Inc.
Novel cationically polymerizable propenyl and vinyl ethers derived from renewable sources
Authors: Crivello J. V. , Bratslavsky S. A.
Published: April 2003

The preparation of several novel mono‐ and dipropenyl and divinyl ethers derived from renewable starting materials is described using simple, straightforward synthetic methods. Utilizing real‐time infrared spectroscopy, the reactivity of the monomers in photoinitiated cationic polymerization was studied employing diaryliodonium and triarylsulfonium salts as photoinitiators. The monomers were shown to undergo very rapid cationic photopolymerization. © 1994 John Wiley & Sons, Inc.
A facile synthesis of aliphatic polybenzoxazoles from a bis(o‐aminophenol) or its hydrochloride and aliphatic dinitriles
Authors: Itoya Kazuo , Sawada Hidetsugu , Kakimoto Masa‐Aki , Imai Yoshio
Published: April 2003

A facile one‐step method for the synthesis of aliphatic polybenzoxazoles has been developed. Thus, a series of aliphatic polybenzoxazoles having inherent viscosities of 0.2–0.7 dL/g in concentrated sulfuric acid were successfully synthesized by the melt polycondensation of alipatic dinitriles with 4,4′‐diamino‐3,3′‐dihydroxybiphenyl (AHB) or its hydrochloride (AHB–HCl) with the elimination of ammonia or ammonium chloride, respectively. Monomer AHB–HCl was more reactive than the parent AHB, thereby affording higher molecular weight polybenzoxazoles in a shorter reaction time. The aliphatic polybenzoxazoles having 6–10 methylene units were highly crystalline with melting temperatures in the range of 187–308°C, which were stable up to 400°C in a melt state in nitrogen. © 1994 John Wiley & Sons, Inc.
Initiation of cationic polymerization of n‐butyl vinyl ether by stable cation radicals of substituted phenothiazines
Authors: Morishima Yotaro , Nomura Shigeki , Kamachi Mikiharu
Published: April 2003

3,7‐Diethyl‐ 10‐phenylphenothiazine (DEPPT), a phenothiazine derivative whose 3,7‐ and 10‐positions are blocked, was synthesized. Potentiostatic electrolysis of DEPPT in acetonitrile (ACN) in the presence of 0.1M of LiClO4 at 0.7 V (vs. Ag/Ag/Cl) yielded the stable cation radical of DEPPT (DEPPT+·) which was characterized by cyclic voltammetry, UV‐visible spectroscopy, and ESR spectrometry. Stable cation radicals of 10‐phenylphenothiazine and 3,7‐diethyl‐10‐methylphenothiazine were also prepared. The cationic polymerization of n‐butyl vinyl ether was initiated by these cation radicals, including DEPPT·+. The electron transfer mechanism for the initiation step, which we proposed previously, was supported by the fact that DEPPT·+ was capable of initiating the polymerization; dimerization of DEPPT·+ by releasing protons is precluded because 3,7‐ and 10‐positions are all blocked. © 1994 John Wiley & Sons, Inc.
Amphiphilic networks. VII. Synthesis and characterization of pH‐sensitive poly(sulfoethyl methacrylate)‐1‐polyisobutylene networks
Authors: Keszler Balazs , Kennedy Joseph P.
Published: April 2003

A series of environmentally sensitive amphiphilic networks consisting of 2‐sulfoethyl methacrylate (SEMA) chains linked by methacrylate‐ditelechelic polyisobutylene (MA–PIB–MA) chains have been prepared and characterized. Network composition was determined after sequential solvent extraction by elemental analysis. These networks are two‐phase microheterogeneous systems containing hydrophobic rubbery PIB domains (Tg ∼ −60°C) and hydrophilic poly(2‐sulfoethyl methacrylate) domains (Tg ∼ −15°C). They exhibit large contact‐angle hysteresis in water which is due to surface segmental mobility and microheterogeneity. By increasing the SEMA content of the networks the contact‐angle hysteresis increases. This phenomenon is due to an increase in the advancing contact angle most likely caused by the migration of the nonpolar PIB domains toward the surface and concomitant decrease of the receding contact angle. These amphiphilic networks exhibit non‐Fickian swelling in n‐heptane, as well as in water, and show pH‐sensitive swelling in aqueous media. They rapidly and reversibly swell and deswell in response to increasing or decreasing the pH of the media (cycling between pH = 2 and 12). © 1994 John Wiley & Sons, Inc.
The structures of low molecular weight glycerin propoxylates: An experimental, semi‐empirical, and Monte Carlo study
Authors: Cooper Charles F. , Polley Charles W.
Published: April 2003

A simple Monte Carlo model has been developed for calculating the structural features and properties of low molecular weight triols produced by the base‐catalyzed propoxylation of glycerin. The model computes the probability of a reaction to a specific oligomer from the local site reactivities of model compounds with an adjustment for the molecular weight of the reacting oligomer. The resulting product array is then used to calculate typical polymer properties such as average molecular weight, polydispersity, and average chain length. Trial rate constants were estimated from the activation energies of MNDO‐PM3 semi‐empirical molecular orbital theory. For the compounds used to model the oligomer chain end groups, the activation enthalpies were found to be within the ranges reported for experimental values. Although the predicted enthalpies of activation were significantly higher for the alkoxylation directly at glycerin, this was found to be attributable to intramolecular hydrogen bonding in the reactants that was disrupted in the transition states. Although the hydrogen bonding energies were higher than what are normally considered typical, comparison tests showed that the calculated energies agreed well with experimental values of alkoxide anion–alcohol systems. The PM3 rate constants, when used to calculate Monte Carlo probabilities, predicted the isomer distribution of the four isomeric monopropoxylates with a error of 4%. Optimization of the model reduced this to 0.5%. However, to accurately predict the oligomer distribution of higher molecular weight adducts and other properties, the correction term (M0/Mi)b had to be included, where M0/Mi is the ratio of the molecular weight of glycerin to the molecular weight of the oligomer undergoing alkoxylation, and b is assigned the value 0.7. Although b is empirical, it is consistent with a simple molecular mechanics (MM2) conformational study of the relative availability of the reactive end groups. When the final model was used to simulate the propoxylation of glycerin for a variety of PO/glycerin ratios, it was found to accurately reproduce properties such as primary hydroxyl content, polydispersity, oligomer distribution, and change in the monopropoxylate isomer ratio as a function of bulk PO/glycerin ratio. © 1995 John Wiley & Sons, Inc.
Molecular structure of polymerization product containing phenyl‐ and diphenylsiloxy units
Authors: Hayashida Shoichi , Imamura Saburo
Published: April 2003

The molecular structure of the hydrolyzate, and of the prepolymers and polymerization products of phenyltrichlorosilane and diphenyldichlorosilane are investigated.29Si‐NMR measurements reveal the kinds of component units and their ratio in each synthesis step. The molecular structure of the prepolymer chain end and the polymerization product are also discussed in relation to the change in the NMR spectra. © 1995 John Wiley & Sons, Inc.
Chemical reactions between immiscible polymers in the melt: Transesterification of poly(ethylene‐co‐methyl acrylate) with mono‐hydroxylated polystyrenes
Authors: Hu Guo‐Hua , Lambla Morand
Published: April 2003

This article presents a unique example dealing with how chemical reactions between immiscible polymers in the melt behave differently than they would do in solution. Specifically, a model reaction was chosen: the transesterification between poly(ethylene‐co‐methyl acrylate) (EMA) and polystyrene mono‐hydroxylated at the chain end (PSOH). It was carried out in the melt in a batch mixer. The overall rate of this reaction has a similar dependence of temperature, composition of reactants, and the nature and concentration of catalyst as in solution. The reactivity of PSOH decreases drastically with increasing molecular weight, and it becomes very weak when the molecular weight exceeds 8000 g/mol. As opposed to a reaction in solution or in a homogeneous melt, mechanical mixing increases the reaction rate since it generates interfacial area and reduces the diffusion length. The EMA‐g‐PS graft copolymer formed at the interfaces reduces the interfacial tension, and increases the miscibility of the reaction mixture. However, its occupation of the interfaces reduces contact between the reactive moieties, thus decreasing the overall reactivity. More importantly and much to our surprise, adding 1 to 2 wt % of an inert solvent increased greatly the overall reaction rate. While an increased interfacial mixing and diffusion by the presence of minor amounts of solvent are thought to be the major factors contributing to the drastic increase in reactivity, numerous questions still remain. Nevertheless, this study clearly showed that as opposed to a reaction in solution, mechanical mixing and the presence of minor amounts of solvent are two additional and critical means to control chemical reactions between immiscible polymer melts. © 1995 John Wiley & Sons, Inc.
Photochemistry of amphiphilic copolymers: Fluorescence spectra of copolymers of 1‐(2‐naphthyl)ethyl methacrylate and sodium 2‐acrylamido‐2‐methylpropanesulfonate in solution
Authors: Itoh Yoshihiro , Yamashita Osamu , Hachimori Akira , Kojima Masanobu , Suzuki Satoshi
Published: April 2003

Amphiphilic copolymers containing 1‐(2‐naphthyl)ethyl ester groups were prepared and their fluorescence properties were examined. The fluorescnce spectra of the copolymers with a higher naphthyl content showed predominantly a broad monomer emission with λmax at 340 nm in methanol, whereas a structured emission with λmax at 344 and 362 nm was observed in aqueous solution. The former spectra changed rapidly to the latter ones upon UV irradiation. Photolysis of the copolymers and the monomeric model compound in methanol gave 2‐vinylnaphthalene, whose fluorescence agreed with those of copolymers in water, together with methyl ether, alkylnaphthalenes, and other products. These results indicate that the copolymers hold vinylnaphthalene‐like traps, which may emit preferentially in water because of efficient sensitization. © 1995 John Wiley & Sons, Inc.
Microgel formation in the free radical crosslinking polymerization of ethylene glycol dimethacrylate (EGDMA). II. Simulation
Authors: Chiu Y. Y. , Lee L. James
Published: April 2003

The simulation of free radical crosslinking polymerizations of multifunctional monomer by a percolation model was performed on a two‐dimensional lattice with periodical boundaries. The model was formulated in such a way that a variety of monomers, translational diffusion of monomer and polymer molecules, segmental diffusion of polymer, shielding effects, microgel formation, and unequal reactivities of vinylene bonds can be considered. Simulation results of the 2‐D model agreed well with those of a 3‐D model. The percolation model was able to qualitatively verify several experimental results. © 1995 John Wiley & Sons, Inc.
Dispersion copolymerization of styrene and divinylbenzene: Synthesis of monodisperse, uniformly crosslinked particles
Authors: Thomson B. , Rudin A. , Lajoie G.
Published: April 2003

Monodisperse, crosslinked polystyrene latexes were prepared by the dispersion technique. Some general observations regarding the effect of initial reagent concentrations on final particle size and size distribution are offered, in addition to a detailed discussion concerning the problems encountered with the use of the crosslinker divinylbenzene (DVB) in latex preparation. Particles synthesized in very polar media were found to reach their growth plateau sooner than those made in less polar surroundings. This trend was proposed to be the result of more effective nucleation in polar environments, which increases available surface area, thereby allowing the rapid replacement of monomer consumed within the particle phase during the polymerization. Attempts to favorably influence the growth rate and size distribution of particles during the reaction were unsuccessful, underlining the importance of the nucleation period in defining particle size characteristics. Up to 1% DVB was successfully incorporated in the synthesis of coagulum‐free, monodisperse, 5 μm beads, by controlling the entry of the crosslinker into the particle phase during the major particle growth period. Latex stability is proposed to be largely dependent on the mobility of the adsorbed steric stabilizer. © 1995 John Wiley & Sons, Inc.
LC‐Polyimides. XIX. Chiral and thermotropic poly(esterimide)s based on N‐(4′‐caboxyphenyl)trimellitimide and novel chiral spacers
Authors: Kricheldorf Hans R. , Berghahn Matthias
Published: April 2003

Starting from commercial S‐ or R‐3‐bromo‐2‐methylpropanol, several new spacer diols were prepared. These spacers were polycondensed with the acid chloride of N‐(4′‐carboxyphenyl)trimellitimide. The resulting poly(ester‐imide)s were characterized by elemental analyses, viscosity measurements, 1H‐NMR spectroscopy, DSC‐ and WAXD‐measurements and optical microscopy. The poly(ester‐imide)s derived from chiral, aliphatic spacers form layer structures in the solid state, but no liquid crystalline phase. With nonsymmetrical, nonchiral semialiphatic spacers, poly(ester‐imide)s were obtained, which form a smectic E or H phase in the solid state, a smectic‐A or ‐C phase in the melt, and a nematic phase, when the spacer possesses an odd number of CH2 groups. The polycondensation of a chiral semialiphatic spacer yielded thermotropic poly(ester‐imide)s with either S‐ or R‐configuration. WAXD patterns measured with synchrotron radiation at various temperatures proved that a layer structure exists in the solid state (smectic‐E* or H*) and a chiral smectic‐A* or ‐C* phase plus a cholesteric phase in the melt. A 1 : 1 blend of the S‐ and R‐polyesters was also studied, but did not show unusual features. © 1995 John Wiley & Sons, Inc.
Solid‐state polymerization of diacetylene: 1,11,13,23‐tetracosatetrayne
Authors: Nezu S. , Lando J. B.
Published: April 2003

The solid‐state polymerization of a diacetylene, 1,11,13,23‐tetracosatetrayne, was studied using x‐ray powder diffraction and electron diffraction. It is shown that the material exhibits polymorphism. Thermochromic transitions, which are generally observed for diacetylenes, are related to the particular crystalline phase using x‐ray powder diffraction. The unit cell dimensions and space group of one polymorph were determined by electron diffraction analysis: a = 20.83 Å, b = 4.84 Å, c = 10.08 Å, β = 92.4°, space group: P21/n. © 1995 John Wiley & Sons, Inc.
Synthesis and radical polymerization of α‐ethyl β‐hexafluoroisopropyl itaconate
Authors: Sato Tsuneyuki , Hirose Yuichiro , Seno Makiko , Tanaka Hitoshi
Published: April 2003

The synthesis of α‐ethyl β‐hexafluoroisopropyl itaconate (EFiPI) was performed. The polymerization of EFiPI initiated with dimethyl 2,2′‐azobisisobutyrate (MAIB) was investigated kinetically in benzene. The polymerization rate (Rp) was expressed by Rp = k[MAIB]0.5[EFiPI]2.0 at 50°C. The overall activation energy of the polymerization was calculated to be a low value of 57.38 kJ/mol. Rate constants of propagation (kp) and termination (kt) were estimated under different polymerization conditions, using the ESR‐determined concentrations of the propagating polymer radical. The increase in kp value (3.3‐6.0 L/mol s) and the decrease in kt value (0.94‐3.7 × 105 L/mol s) with monomer concentration are mainly responsible for the high dependence of Rp on the monomer concentration. Activation energies of initiation (Ei), propagation (Ep), and termination (Et) were also determined: Ei = 130.7 kJ/mol, Ep = 18.0 kJ/mol, Et = 57.4 kJ/mol. The large apparent activation energy of termination is a main origin of low overall activation energy of the polymerization. Thermal behavior of the resulting poly(EFiPI) was investigated by differential scanning calorimetry (DSC) and dynamic thermogravimetry (TG). Copolymerization of EFiPI (M1) with St (M2) was also examined at 50°C in benzene. The following copolymerization parameters were obtained according to the curve‐fitting method: r1 = 0.05, r2 = 0.46, Q = 0.46, e = +1.14. Using these results, the rate constants of cross propagations in the copolymerization were estimated. © 1995 John Wiley & Sons, Inc.
Preparation and properties of novel soluble poly(aryl ether)s bearing covalently bound tetrapyrazinoporphyrazine units
Authors: Yang Haixin , Sargent Jonathan R. , Hay Allan S.
Published: April 2003

Thermooxidatively stable amorphous poly(dicyanopyrazine ether)s with high glass transition temperatures are synthesized and converted into poly(aryl ether)s bearing covalently bound zinc(II) 2,3,9,10,16,17,23,24‐octaphenyltetrapyrazinoporphyrazine units. They are soluble in common organic solvents and can be cast into strong and flexible films. The maximum absorption wavelength of the poly(aryl ether)s bearing zinc (II) 2,3,9,10,16,17,23,24‐octaphenyltetrapyrazinoporphyrazine units in chloroform is 654 nm. © 1995 John Wiley & Sons, Inc.
Soluble polymer‐supported catalysts containing pendant quaternary onium salts for the addition reaction of oxiranes with carbon dioxide
Authors: Nishikubo Tadatomi , Kameyama Atsushi , Yamashita Jun , Fukumitsu Takahiro , Maejima Chika , Tomoi Masao
Published: April 2003

The addition reaction of oxiranes (15a‐d) with carbon dioxide (CO2) was carried out using 1 mol % of soluble polymer‐supported quaternary onium salts as catalysts under atmospheric pressure. The reaction of 15a‐d with CO2 proceeded very smoothly to give the corresponding five‐membered cyclic carbonates (16a‐d) in high yields at 90‐100°C. The catalytic activity of the soluble polymer‐supported quaternary onium salts was strongly affected by the following factors: kind of reaction solvent, degree of introduction of the pendant onium salt residues in the polymer chain, and type of alkyl group on the onium salts due to the balance between lipophilicity and steric hindrance of the onium salt residue. Furthermore, these soluble polymer‐supported quaternary onium salts were found ordinarily to have higher catalytic activity than low molecular weight quaternary onium salts under the same reaction conditions. It was also found that the rate of reaction was proportional both to catalyst concentration and to oxirane concentration. © 1995 John Wiley & Sons, Inc.
Alternating copolymers consisting of arylalkyl methacrylates. I. Fluorescence properties of poly(arylalkyl methacrylate‐alt‐styrene) in organic solution
Authors: Itoh Yoshihiro , Inoue Masamitsu , Takahashi Tomoko , Hachimori Akira , Suzuki Satoshi
Published: April 2003

Alternating and random copolymers of 9‐phenanthrylmethyl methacrylate or 2‐(9‐carbazolyl)ethyl methacrylate with styrene were synthesized and their fluorescence properties were examined. There was no noticeable difference in the spectral features of the alternating and random copolymers in tetrahydrofuran (THF), demonstrating that this type of polymers have no quenching sites in the polymer chains. The fluorescence quenching studies indicated that the alternating copolymers permitted singlet‐state energy migration as efficiently as the corresponding random copolymers but less efficiently than the random copolymers with higher chromophore contents. These results strongly suggest that to be chromophores close to each other is most important for facilitation of an intramolecular energy migration. © 1995 John Wiley & Sons, Inc.
Growth of poly(methyl methacrylate) particles in three‐component cationic microemulsions
Authors: Gan L. M. , Lee K. C. , Chew C. H. , Tok E. S. , Ng S. C.
Published: April 2003

Polymerization of methyl methacrylate (MMA) has been studied in ternary microemulsions which were stabilized by tetradecyltrimethylammonium bromide (TTAB) or stearyltrimethylammonium chloride (STAC). The sizes of MMA‐swollen polymer particles (Rh) increased continuously during polymerization. This is in contrast to that of the styrene system, where Rh increased very rapidly to a maximum and then decreased continuously towards a constant value. The continuous growth of PMMA particles at 60°C are discussed. The stability of PMMA latexes increased with increasing the hydrophobic chain length of the cationic surfactant used. Traces of the coagulations of PMMA particles in the TTAB system can be seen from TEM. © 1995 John Wiley & Sons, Inc.
Study of the reaction between 1,5‐naphtalene diisocyanate and polycaprolactone in different solvents
Authors: Lesar Meta , Žigon Majda , Malavašič Tatjana
Published: April 2003

The reaction between polycaprolactone and 1,5‐naphtalene diisocyanate has been investigated in solvents with different dielectric constants and hydrogen bonding powers (toluene, ethyl acetate, ethyl methyl ketone), and in the same solvents with the addition of a catalytic amount of dimethyl sulfoxide (DMSO). The reaction was considered to proceed over two steps, the reaction of the first NCO group being faster. The course of the reaction was measured by titration of the unreacted NCO groups, 1H‐ and 13C‐NMR spectroscopy, and size exclusion chromatography. By titration only the overall reaction order and reaction rate constants could be determined. DMSO accelerated the reaction in all three solvents, which was explained by the stabilization of the activation complex by DMSO. Both steps of the reaction could be specified by NMR spectroscopy. The ratio between the reaction rate constants for the first and the second step decreased with the increased hydrogen bonding strength of the solvent and with DMSO. By SEC only the reaction of the first NCO group could be determined due to the low resolution for higher molar mass reaction products with a broad distribution. The values obtained for the first step reaction rate constants were in good agreement with NMR values. © 1995 John Wiley & Sons, Inc.
Solvation effect in thermal decomposition of 2,2′‐azoisobutyronitrile on the N,N‐dimethylformamide/methyl methacrylate system
Authors: Szafko J. , Feist W.
Published: April 2003

The thermal decomposition rate constant of AIBN (𝓀d) in N,N‐dimethylformamide (DMF)/methyl methacrylate (MM) mixtures of various compositions at 60°C is studied. The 𝓀d value is 6.45 × 10−4min−1 for pure DMF and 7.20 × 10−1 min−1 for pure methyl methacrylate. The 𝓀d values of DMF/MM mixtures were found to be dependent on the mixture composition. This dependence is not a linear function of the monomer mole fraction, but has a minimum at ca. 20 30 mol% of MM. The relationship between the AIBN decomposition rate constant and the monomer mole fraction was interpreted on the basis of solvation of the initiator molecules. © 1995 John Wiley & Sons, Inc.
Visible light photopolymerization: Synthesis of new fluorone dyes and photopolymerization of acrylic monomers using them
Authors: Tanabe Takayoshi , Torres‐Filho Afranio , Neckers D. C.
Published: April 2003

Several 3‐alkoxy‐5, 7‐diiodo‐6‐fluorones (λmax ≈ 470 nm) have been synthesized and evaluated as initiators for photopolymerization triggered with the 515.5 nm line of an Ar+ laser. 2‐Acyl‐ and 2‐alkyl‐4,5,7‐triiodo‐3‐hydroxy‐6‐fluorones were also tested at 515.5 nm. 9‐Cyano‐2‐Acyl‐ and 9‐cyano‐2‐alkyl‐4,5,7‐triiodo‐3‐hydroxy‐6‐fluorones were studied and could be excited with the 632 nm line of a He–Ne laser. Dyes with long linear carbon chain alkoxy groups at C‐6 showed larger molar extinction coefficients and formed polymers with better mechanical properties than did compounds with shorter carbon chains, or did the corresponding C‐6 phenols. The optimum side chain length of the C‐6 ether alkyl group is between 4–7 carbon atoms. With longer carbon chain alkoxy groups at C‐8, e.g., octyl, the mechanical properties of the formed polymers are inferior to systems formed with the butyl isomer as photoinitiator. In the case of alkoxy groups with branched alkyl groups (e.g., 2‐ethylbutyl), the relationship between dye structure and the properties of the polymers formed is less straightforward. Though the dyes react from their triplet state, the fluorescence quantum yields of the dyes and the performance of the dyes as photoinitiators appear directly related. © 1995 John Wiley & Sons, Inc.
Temperature‐sensitive luminescence of tris (β‐diketone) europium chelates for monitoring high‐speed cationic photopolymerizations
Authors: Crofcheck C. L. , Nelson E. W. , Jacobs J. L. , Scranton A. B.
Published: April 2003

The temperature‐dependent luminescence of tris (β‐diketone) chelates of europium was used for in situ temperature measurements during cationic photopolymerizations of vinyl ethers. These molecular‐level luminescent probes provided a real‐time, noninvasive method for monitoring temperature during these high‐speed polymerizations. Two specific probes, tris (benzoyl‐1, 1, 1‐trifluoroacetone) europium and tris (1,1,1,5,5,5,‐hexafluoroacetylacetone) europium, met several stringent spectral and performance requirements for application in our system. The luminescence from these probes exhibits a reproducible temperature dependence over a wide temperature range and is not sensitive to changes in viscosity. In situ temperature profiles obtained using this novel technique verified the importance of thermal effects during these highly exothermic photopolymerizations. These studies have demonstrated the utility of the tris(β‐diketone) europium chelates for characterizing the temperature during high‐speed photopolymerizations that cannot be monitored using conventional techniques. © 1995 John Wiley & Sons, Inc.
Polynucleotide analogues. VI. Synthesis and characterization of alternating copolymers of maleic anhydride and dihydropyran containing guanine derivatives
Authors: Han Man Jung , Cho Nam Shik , Cho Tae Joon , Chang Ji Young
Published: April 2003

2‐Amino‐6‐chloropurine was reacted with 2‐(tosyloxymethyl)‐2,3‐dihydro‐2H‐pyran to give 2‐(2‐amino‐6‐chloropurin‐9‐ylmethyl)‐2,3‐dihydro‐2H‐pyran (3) and its N7‐isomer (4), which were treated with 5% aqueous trimethylamine to result in 2‐(guanin‐9‐ylmethyl)‐2,3‐dihydro‐2H‐pyran (5) and its N7‐isomer (6), respectively. 2‐(N2‐Acetylguanin‐9‐yl‐methyl)‐3,4‐dihydro‐2H‐pyran (7) and 2‐(N2‐acetylguanin‐7‐ylmethyl)‐3,4‐dihydro‐2H‐pyran (8), obtained by acetylation of compounds 5 and 6, were copolymerized with maleic anhydride to give the alternating copolymers 9 and 10, and they were hydrolyzed to result in poly[ {2‐(guanin‐9‐ylmethyl)tetrahydropyran‐5,6‐diyl} {1,2‐dicarboxyethylene}] (11) and poly[ {2‐(guanin‐7‐ylmethyl)tetrahydropyran‐5,6‐diyl} {1,2‐dicarboxyethylene}] (12), re‐spectively. Polymer 11 showed hypochromicity whereas 12 exhibited hyperchromicity in aqueous solutions. Polymers 11 and 12 in aqueous solutions showed very strong excimer fluorescence with the maximum intensities at 432 and 446 nm, respectively, at room tem‐perature. The two polymers showed polyelectrolyte effects, e.g., very high GPC molecular weights as well as reduced viscosities at low concentrations in water. Normal behavior was retained by addition of inorganic salts. Sodium salts of polymers 11 and 12 migrated to the anode by electrophoresis and both showed two bands. © 1995 John Wiley & Sons, Inc.
Emulsion polymerization of supermicron, monodisperse acrylic copolymer particles with core‐shell structures
Authors: O'Callaghan K. J. , Paine A. J. , Rudin A.
Published: April 2003

The emulsion polymerization of large MMA/BA copolymer particles with narrow particle size distributions and core‐shell structure is described. A series of sequential seeded growth emulsion polymerizations were used to obtain monodisperse particles with diameters of at least 3 μm, at 30% solids contents. Because the core and shell polymers used here were chemically similar, core‐shell structures could not be verified by differential staining tech‐niques. Core‐shell structure was demonstrated by minimum film‐forming temperature studies and by scanning electron microscopy in conjunction with energy dispersive x‐ray analysis, using chlorine‐labeled core polymers. © 1995 John Wiley & Sons, Inc.
Simultaneous polymerization and formation of polyphenylacetylene film by Nd(P204)3–Fe (AA)3–Al(i‐Bu)3 combined catalyst system
Authors: Yang Mujie , Zhan Xiaowei , Zhao Jian , Shen Zhiquan
Published: April 2003

The simultaneous polymerization and formation of polyphenylacetylene film by Nd(P204)3–Fe(AA)3–Al(i‐Bu)3 catalyst system have been investigated. The combined catalytic effects between rare earth phosphonates with MT(naph)x or Fe(AA)3 systems are first proposed and compared. The polymerization features and kinetic behaviors with Nd(P204)3–Fe(AA)3‐Al(i‐Bu)3 system are described and discussed. The combined catalytic effects have the following order, respectively: Fe ≫ Co > Cr > Mn‐Ni, Nd(P204)3‐Nd(P507)3 > Nd(P350)3 and Tb > Sm > Yb > Ho > Lu > Dy > Nd‐Er‐Pr > Y‐Tm > Ce > Gd > La. The overall polymerization activation energy was found to be 20.8 kJ/mol showing coordination‐anionic polymerization characteristic. PPA films so obtained are very similar to the rare earth ones. © 1995 John Wiley & Sons, Inc.
Thianthrene‐containing polyimides with monomer formation via nucleophilic aromatic substitution
Authors: Yoneyama Masaru , Johnson Randy A. , Mathias Lon J.
Published: April 2003

Thianthrene‐2,3,7,8‐tetracarboxylic dianhydride was synthesized via nucleophilic aromatic substitution of N‐phenyle‐4,5‐dichlorophthalimide with thiobenzamide, thioacetamide, and sodium sulfide. This monomer was then polymerized with aromatic diamines by the con‐ventional low temperature technique in N,N‐dimethylacetamide (DMAc) to yield soluble poly(amic acid)s. Polyimides were obtained by thermal cyclization of the poly(amic acid) films. Polymers obtained formed creasable thin films and had excellent thermal stability in air and nitrogen. The bent thianthrene structure limited crystallization and chain packing, as indicated by x‐ray analysis. The amorphous thianthrene‐containing polyimides were only soluble in H2SO4. © 1995 John Wiley & Sons, Inc.
Vacuum‐ultraviolet induced oxidation of the polymers polyethylene and polypropylene
Authors: Holländer A. , Klemberg‐Sapieha J. E. , Wertheimer M. R.
Published: April 2003

The emission from low‐pressure microwave plasmas in the vacuum‐ultraviolet (VUV) region (λ < 200 nm) was investigated in order to use these plasmas as light sources for the study of the VUV photochemistry of polyethylene (PE) and polypropylene (PP) as part of the study of plasma‐polymer interaction. These polymers, immersed in low‐presure oxygen, were exposed to radiation with wavelengths down to 112 nm, the cut off of magnesium fluoride used as a window to separate the polymer specimen from the plasma light source. Total oxygen incorporation in the surface [O], and the formation of hydroxyl, carbonyl, and carboxyl groups were measured using XPS in combination with chemical derivatizations, particularly their dependence upon the radiation spectrum and the oxygen pressure around the sample. In most experiments the surface oxygen concentration [O] attained a constant value that appears to be related to the initial oxidation rate; this suggests a competition between oxygen incorporation and chain scission reactions, followed by the removal of volatile oxidation products. PE is usually oxidized to a higher level than PP, the latter appearing to be more susceptible to reaction with atomic oxygen than PE. A general initiation mechanism for the VUV experiments is proposed that allows us to explain the observed differences in behavior between PE and PP, and the results obtained under different irradiation conditions. The nature of oxidation products is in both cases very similar to what is observed after direct plasma treatment of the polymers. We conclude that short wavelength radiation contributes very appreciably to the observed surface modification effects during plasma treatment of PE and PP. © 1995 John Wiley & Sons, Inc.
Synthesis and properties of a poly(diphenylacetylene) containing carbazolyl groups
Authors: Tachimori Hiroshi , Masuda Toshio
Published: April 2003

1‐(p‐N‐Carbazolylphenyl)‐2‐phenylacetylene (p‐CzDPA) was polymerized by TaCl5–co‐catalyst systems (cocatalysts: n‐Bu1Sn, Et3SiH, and 9BBN) to produce acetone‐insoluble polymers in about 60‐70% yields. Poly(p‐CzDPA) was a yellowish‐orange solid, most part of which was soluble in toluene, chloroform, etc., and its weight‐average molecular weights were around 4×105. This polymer formed a tough film by solution casting, and was thermally very stable (the onset temperature of weight loss in TGA in air 470°C). The oxygen per‐meability coefficient of the polymer at 25°C was lower than two barrers. The present polymer showed photoconductivity and redox activity. © 1995 John Wiley & Sons, Inc.
Synthesis and properties of aromatic polyamides derived from 1,2‐bis(4‐aminophenoxy)benzene and aromatic dicarboxylic acids
Authors: Yang Chin‐Ping , Cherng Jeng‐Jieh
Published: April 2003

1,2‐Bis(4‐aminophenoxy)benzene was synthesized in two steps by the preparation of 1,2‐bis(4‐itrophenoxy)benzene from 1,2‐dihydroxybenzene (catechol) and p‐chloronitrobenzene and subsequent reduction with a 10% Pd‐C catalyst and hydrazine hydrate. Aromatic polyamides with an inherent viscosity in the range of 1.08–2.00 dL/g were prepared by the direct polycondensation of this diamine with various aromatic dicarboxylic acids in N‐methyl‐2‐pyrrolidone (NMP) using triphenyl phosphite and pyridine as condensing agents. Most of the polymers formed were soluble in aprotic solvents such as NMP and N,N‐methylacetamide (DMAc), and afforded transparent, flexible, and tough films upon casting from DMAc solutions. Most of the cast films showed obvious yield points in their stress‐strain curves and had tensile strength among 64–89 MPa, elongation at break among 5–23%, and initial modulus in 1.7–2.5 GPa. The glass transition temperatures (Tg) of these polymers were in the range of 207–278°C, and the 10% weight loss temperatures were recorded above 475°C in nitrogen and above 452°C in air. © 1995 John Wiley & Sons, Inc.
Propylene polymerization through supported metallocene/ MAO catalysts: Kinetic analysis and modelling
Authors: Bonini F. , Fraaije V. , Fink G.
Published: April 2003

Several propylene polymerizations are carried out with supported metallocene catalyst, prepared by reaction of silica gel with methylaluminoxane and then with rac‐dimethylsi‐lanediylbis(indenyl)zirconiumdichloride. The rate–time curves obtained are analyzed to understand the influence of support and triisobutylaluminium on the reaction. As a first attempt to model this system we developed a partially new praticle growth model, based on a shell by shell fragmentation hypothesis (gradual break‐up from the outside to the inside of the particle), and a final multigrain structure of the particle. A kinetic scheme including the TIBA interaction with the supported catalyst is also presented. The model prediction and the experimental data are compared for the rate–time curves and polymer properties. © 1995 John Wiley & Sons, Inc.
High‐pressure synthesis of cyclic phenylacetylene oligomer
Authors: Kojima Yoshitsugu , Matsuoka Takaaki , Sato Norio , Takahashi Hideroh
Published: April 2003

New conjugated oligomers were prepared by reacting phenylacetylene under high pressure of 0.11 to 0.92 GPa at 100–200°C for 0–5 h. The number‐average molecular weight M̄n, the weight‐average molecular weight M̄w, and the oligomer yield increased with pressure, tem‐perature, and time. The average molecular weight of the oligomer showed the maximum value (M̄n: 830, M̄w: 2400) under 0.92 GPa, the maximum pressure, where phenylacetylene was oligomerized at a constant temperature. The structure of the oligomer was investigated from ESR, infrared, UV–VIS, field desorption mass (FDMS) spectra, and 13C NMR spec‐trum. Analysis of the FDMS spectrum revealed that the molecular weight of the oligomer was multiple of the monomer. 13C NMR spectrum of the oligomer showed the absence of sp‐carbon (C). We found that the oligomer had a cyclic structure. The cyclic oligomers of pentamer or more were new compounds. © 1995 John Wiley & Sons, Inc.
Social consequences of mining and present day solutions—Region II in Chile highlighted
Authors: Newbold Jane
Published: April 2003

Chile has been a highly successful mining country for over two centuries. Huge sums of money are generated but only a small proportion of the revenue is being directed back into the region whose natural resources are being depleted. Mining companies may not be in control of the way central government spends these funds but they have a responsibility towards the communities they impact. The environmental problems associated with mining practices have attracted most attention but the impact on the communities is proving to be a far greater challenge. This paper focuses on the social consequences and the evolving response of the mining companies to these problems and the future sustainability of the region. Copyright © 2003 John Wiley & Sons, Ltd. and ERP Environment
New Zealand fisheries management: changes in property rights structure and implications for sustainability
Authors: Stewart James M. , Callagher Peter D.
Published: April 2003

Participation in the New Zealand fishing industry exists on two levels: quota holding and quota ownership. This study is motivated by the desire to establish whether changes in the number and concentration of quota ownerships and quota holdings have had any impact on the sustainability of fishery in New Zealand.

Of the 294 marine species commercially harvested in New Zealand the top 15 by volume and/or value are considered in this paper. Findings indicate that quota ownership and holding have become more concentrated since the inception of the individual transferable quota (ITQ) regime, with the concentration ratios CR4, CR10 and CR20 all increasing. This suggests that the introduction of the ITQ has not encouraged the entry of new market participants; rather the industry has moved toward a single ownership model.

Second, this paper establishes trends in the level of total allocable commercial catch (TACC) over the study period (August 1986–June 2000). Findings suggest that, with one or two interesting exceptions, catch levels have remained remarkably constant. Prima facie, there appears to have been no adverse impact from structural change on the overall resource sustainability based on TACC. Copyright © 2003 John Wiley & Sons, Ltd. and ERP Environment
Regulating traffic with land use planning
Authors: Herala Nina
Published: April 2003

This article deals with integrating land use planning and traffic planning to promote sustainable development: how land use planning may be used as one of the means to reduce problems caused by traffic. The growth in car‐borne traffic has increased rapidly and consumes more and more land because of land‐extensive structure of cities and the traffic demand between human activities (home, work, services). Planning solutions emphasizing the separation of urban functions, in order to avoid health problems, have, together with the availability of inexpensive land on the outskirts of urban areas, contributed to the current generation of environmental problems, primarily from increased dependency on private cars. The OECD and EU have developed principles of sustainable transport and sustainable traffic to tackle the growth of traffic. Urban form and location of activities together with economic incentives and well organized public transport has a significant impact on traffic flows. There is not yet a general political agreement on how the reduction of traffic demand should be legally regulated, but some criteria are suggested to measure sustainable mobility in land use planning. Copyright © 2003 John Wiley & Sons, Ltd. and ERP Environment
County waste minimization programmes: a case study from Northamptonshire, UK
Authors: Phillips Paul S. , Clarkson Paul , Adams Julie , Read Adam D. , Coggins P. Chris
Published: April 2003

The UK Sustainable Development Strategy requires that society strive to make prudent use of natural resources so as to protect the environment and maintain high and stable levels of economic growth and employment. The Waste Strategy for England and Wales emphasizes the need to reduce the amount of waste produced through the adoption of waste minimization methodology. Waste minimization clubs have been a key element in the UK programme to introduce more sustainable practice into industry and commerce. Northamptonshire, a county in the East Midlands of England, has benefited from 14 waste minimization/resource efficiency projects, within a county programme, that have run between 1998 and 2001. This is the largest number in any county in England. This has been possible because of the formation of a large and inclusive partnership that contains all the key local and regional players. Performance indicators have been developed to direct the county programme as it strives to introduce more sustainable waste management practice. The Northamptonshire model has led to a catalysed uptake of sustainable waste management practice and has resulted in greatly improved competitiveness in some 270 companies, thereby contributing to the maintenance of stable levels of economic activity. Copyright © 2003 John Wiley & Sons, Ltd. and ERP Environment
Social interaction and the use of analogy: An analysis of preservice teachers' talk during physics inquiry lessons
Authors: Yerrick Randy K. , Doster Elizabeth , Nugent Jeffrey S. , Parke Helen M. , Crawley Frank E.
Published: April 2003

Analogies have been argued to be central in the process of establishing conceptual growth, making overt connections and carryover into an intended cognitive domain, and providing a generative venue for developing conceptual understanding inherent in constructivist learning. However, students' specific uses of analogies for constructing arguments are not well understood. Specifically, the results of preservice teachers' knowledge gains are not widely studied. Although we would hope that engaging preservice science teachers in exemplary lessons would assist them in using and generating analogies more expertly, it is not clear whether or how such curricula would affect their learning or teaching. This study presents an existence proof of how preservice science teachers used analogies embedded in their course materials Physics by Inquiry. This fine‐grained analysis of small group discourse revealed three distinct roles of analogies including the development of: (a) cognitive process skills, (b) scientific conceptual understanding, and (c) social contexts for problem solving. Results suggest that preservice teachers tend to overgeneralize the analogies inserted by curriculum materials, map irrelevant features of analogies into collaborative problem solving, and generate personal analogies, which counter scientific concept development. Although the authors agree with the importance of collaborative problem solving and the insertion of analogies for preservice teachers' conceptual development, we believe much more needs to be understood before teachers can be expected to construct and sustain effective learning environments that rely on using analogies expertly. Implications for teacher preparation are also discussed. © 2003 Wiley Periodicals, Inc. J Res Sci Teach 40: 443–463, 2003
Investigation of secondary school, undergraduate, and graduate learners' mental models of ionic bonding
Authors: Coll Richard K. , Treagust David F.
Published: April 2003

Secondary school, undergraduate, and graduate level learners' mental models of bonding in ionic substances were explored using an interview protocol that involved the use of physical substances and a focus card containing depictions of ionic bonding and structure. Teachers and faculty from the teaching institutions were interviewed to contextualize teaching models within the educational setting for the inquiry. These data resulted in two socially negotiated consensus teaching models and a series of criterial attributes for these models: the essential qualities, all of which must be negotiated, if the model is used in a way that is acceptable to scientists. The secondary school learners see ionic bonding as consisting of attraction of oppositely charged species that arise from the transfer of electrons driven by the desire of atoms to obtain an octet of electrons. The undergraduates see the lattice structure as a key component of ionic substances and quickly identified specific ionic lattices for the physical prompts used as probes. The graduates also identified strongly with ionic lattices, were less likely to focus on particular ionic structures, and had a stronger appreciation for the notion of the ionic‐covalent continuum. The research findings suggest that learners at all educational levels harbor a number of alternative conceptions and prefer to use simple mental models. These findings suggest that teachers and university faculty need to provide stronger links between the detailed nature of a model and its intended purpose. © 2003 Wiley Periodicals, Inc. J Res Sci Teach 40: 464–486, 2003