bluuebunny/crossref_metadata_2025 huggingface dataset:
Study of synthesis and properties of tetrafluoroethylene–propylene copolymers
Authors: Kostov G. K. , Chr. Petrov P.
Published: April 2003

Bulk copolymerization of tetrafluoroethylene (TFE) with propylene (P) initiated by tert‐butyl peroxybenzoate (TBPB) in the temperature interval 323–363 K, monomer pressure from 2 to 9 MPa, and TFE and P molar ratio from 20/80 to 90/10 was carried out. The effect of these reaction conditions on the yield, molecular weight, and polymer composition of the copolymer synthesized was studied. Rubber‐like alternating copolymers in a wide range of monomer compositions of TFE and P (from 40 to 80 mol %) were obtained. The reaction proceeds in a stationary state without an induction period. Monomolecular chain transfer reaction (Cp = 5 × 10−4) to propylene takes place. The relative reactivity ratio of P and TFE (0.15 and 0.01, respectively) and apparent activation energy Eα = 75.8 kJ/mol of the reaction were determined.
The molecular weight limiting step in the ring‐opening polymerization of 1,1‐disubstituted epoxides catalyzed by bis(diisobutylaluminum)oxide
Authors: Nicholas Paul P.
Published: April 2003

The ring‐opening polymerization of 1,2‐epoxy‐4,4,4‐trifluoro‐2‐methylbutane (2) and its unfluorinated analogue, 1,2‐epoxy‐2‐methylbutane (3), gives the expected polyethers when catalyzed by bis(diisobutylaluminum)oxide. However, the molecular weights are low because of a competing deprotonation/ring‐opening of the epoxide that produces all three possible alkene end groups and their stereoisomers. With 2, deprotonation occurs mainly at the methyl group to give the terminal double bond and only minor amounts of the internal double bond. However, 3 gives the opposite regiochemistry. A model is proposed where this reaction occurs within an aluminum(polyether oxide) bound to the least hindered face of the epoxide ring. In this model, the different regiochemistries originate from a concerted and highly directed deprotonation/ring‐opening of 2 versus a step‐wise deprotonation of 3 through its ring‐opened, tertiary‐cation.
Polymer drying. V. Intramolecular‐rotor fluorescence studies of evaporation from liquid‐saturated poly(styrene‐co‐divinylbenzene)
Authors: Errede L. A. , Tiers G. V. D. , Trend J. E. , Wright B. B.
Published: April 2003

The fluorescence intensity and residual weight of poly(styrene‐co‐divinylbenzene) saturated with a < 0.003M solution of a intramolecular‐rotor‐fluorescent probe‐molecule in a volatile liquid were monitored simultaneously as the system evaporated at 23°C to virtual dryness. The “breakpoints” in the pattern for fluorescence increase coincided with the “breakpoints” in the kinetics of desorption with respect to the number, αt of residual sorbed volatile molecules per phenyl group in the polymer, showing that both time‐studies reflect the same physical changes in the system that occur reproducibly as αt decreases monotonically through α′s and α′g the compositions that signal respectively incipient elimination of volatile molecules immobilized by adsorption to polymer, and incipient transition of the system from the rubbery state to the glassy state. The fluorescence intensity attained its asymptotic limit before αt became equal to αg the composition identified earlier to be that which marks completion of the transition to the glassy state.
Polymer drying. VI. EPR spin‐probe studies on swelled poly(styrene‐co‐divinylbenzene)
Authors: Errede L. A. , Aus E. B. , Duerst R. W.
Published: April 2003

The electron paramagnetic resonance (EPR) signal and the residual number (αt) of volatile molecules per phenyl group of poly(styrene‐co‐divinylbenzene) in samples that had been swelled to saturation in a dilute solution of a nitroxide spin‐probe (TEMPO or 4‐oxo‐TEMPO), dissolved in a volatile liquid, were monitored simultaneously as the system containing excess liquid was allowed to evaporate to dryness. The results showed that the characteristic motionally narrowed three‐line EPR spectrum began to change when αt became equal to αg (the number of sorbed molecules per phenyl group of polymer at liquid‐saturation). The ratio of the intensity of the low‐field and high‐field hyperfine peaks relative to the middle peak decreased monotonically to an asymptotic limit that was attained when αt became equal to αg (the number of residual adsorbed molecules per phenyl group of polymer at completion of the transition from the rubbery state to the glassy state). The EPR hyperfine pattern, from which the rotational correlation times were estimated, changed most significantly as αt decreased from αG to αg while exhibiting inflections at about α′s and α′g the compositions that mark, respectively, incipient desorption of adsorbed molecules and incipient transition from the rubbery state to the glassy state. The pattern between these inflections points, however, varied with the affinity of the solvent for the polymer.
Polymer drying. VII. 1H‐NMR studies of evaporation from liquid saturated poly(styrene‐co‐divinylbenzene)
Authors: Errede L. A. , Newmark Richard A.
Published: April 2003

Composition‐studies were carried out in which samples of films composed of poly(styrene‐co‐divinylbenzene) particles enmeshed by poly(tetrafluoroethylene) fibers were saturated with dichloromethane and then allowed to evaporate at 23°C to virtual dryness as the 1H‐NMR signals and residual weight of sorbed liquid were monitored. The correlations, of 1H‐NMR line‐widths with the corresponding log of the number, αt of residual sorbed molecules per monomer unit show that sharp changes occur as αt passes through αG the composition that exists when all the liquid not sorbed (i.e., not present within the liquid‐saturated particles), has been eliminated, and again as αt passes through αg the composition that exists when the particles attain the rigidity characteristic of the glassy state. Correlation of the corresponding T1 relaxation times with log αt show that sharp changes occur when αt becomes equal first to α′s and then to α′g the compositions that exist respectively when, firstly, all the sorbed liquid not immobilized by adsorption to the polymer chains within the particles has been eliminated, and then when the desorption of immobilized liquid from the chains causes the composition to begin to undergo transition from its rubbery state to its glassy state.
Preparation of hindered piperidine and its copolymerization with propylene over a supported high activity ziegler–natta catalyst
Authors: Wilén Carl‐Eric , Auer Markku , Näsman Jan H.
Published: April 2003

A new polymerizable stabilizer 4‐(hex‐5‐enyl)‐2,2,6,6‐tetramethylpiperidine is prepared. This sterically hindered piperidine was copolymerized with propylene over a fourth generation TiCl4/MgCl2 Ziegler–Natta catalyst, using Al(C2H5)3 as cocatalyst and diphenyldimethoxysilane, DMS, as external electron donor. The copolymer exhibited high thermo‐oxidative stability even after exhaustive extraction with n‐heptane.
Synthesis and characterization of new thermotropic liquid crystalline polymers with paired mesogens containing azobenzene unit: Poly(malonic ester)s
Authors: Han Yang‐Kyoo , Kim Dong‐Yu , Kim Young Ha
Published: April 2003

New thermotropic liquid crystalline poly(malonic ester)s with two symmetrical mesogenic units (paired mesogens) were prepared by the polycondensation of 1,6‐dibromohexane and novel malonic ester compounds with different flexible ethyleneoxy spacer lengths linked to azobenzene group. All the prepared malonic esters and the resulting polymers exhibited monotropic liquid crystallinity with a nematic texture. The length of the spacer had influence on the temperature of phase transition of them. A possibility of application of the prepared polymers to reversible optical information storage media was also identified through a trans–cis isomerization of azobenzene by UV irradiation.
Radical copolymerization of an electron‐accepting monomer, methyl cis‐β‐cyanoacrylate, with styrene or acrylonitrile
Authors: Nagai Katsutoshi , Okada Koichi , Kido Junji
Published: April 2003

The electron‐accepting property and the radical copolymerizability of methyl cis‐β‐cyanoacrylate (MCA) were studied. The monomer was found to form a contact charge‐transfer complex with styrene (ST) in chloroform at 25°C and behaved as a weak electron acceptor. The copolymerization parameters were determined in dioxane at 50°C for systems involving ST or acrylonitrile (AN) as comonomer. The reactivity ratio of ST or AN was estimated by the Kelen–Tudös method considering both the penultimate unit effect and no homopropagation of MCA. The penultimate effect for the system ST–MCA was large compared with that for the system ST–dimethyl maleate (DMM), indicating that a polar effect is mainly responsible for the penultimate effect. The terpolymerization of ST, MCA, and maleic anhydride (MA) was also studied to compare the reactivity of MCA with that of MA.
Thermal behavior of copolyimides containing bisbenzoylamine groups
Authors: Litauszki L. , Karasz F. E. , Grünberg K. , Berger W.
Published: April 2003

In an effort to improve the processibility of full aromatic polyimides, copolybisbenzoylamine imides were synthesized. As this study is a continuation of our work on flexibilization of the polyimide main chain, the bisbenzoylamine group was introduced stepwise into the polyimide main chain. Mixtures of pyromellitic anhydride, the rigid component, and a bisbenzoylamine‐3,3′, 4,4′‐tetracarboxylic acid dianhydride, the flexible component, were polymerized with aromatic diamines in a two‐step procedure. The thermal stability of the four series of resulting copolyimides shows parallel changes that depend on the dianhydride ratio. The functional dependence of glass transition temperature (Tg) on copolymer composition differs for hydrogen or alkyl group substitution on the nitrogen in the bisbenzoylamine group. The solubility of the copolyimides in dimethylformamide changes from 0 to 33 wt %; there is a nonlinear dependence between solubility and the dianhydride ratio.
Photodegradation of polyimides. III. The effect of chemical composition, radiation source, atmosphere, and processing
Authors: Hoyle Charles E. , Anzures Edgardo T.
Published: April 2003

Polymide films made from diarylanhydrides with oxygen, carbonyl, and hexafluoroisopropylidene 6F bridging groups are photolabile when irradiated with unfiltered light from a medium‐pressure mercury lamp. The presence of oxygen is necessary to the photolytic degradation process, which results in the ultimate oxidative ablation of thin polyimide films. Films based on the 6F dianhydride containing a hexafluoroisopropylidene hinge group are the most unstable. However, photolysis of 6F dianhydride based polyimides in an inert atmosphere with either the unfiltered medium pressure mercury lamp or an electron beam results in no detectable changes even after long exposure times.
New polymer syntheses. LXI. Synthesis and alkylation of aromatic poly(pyrazine‐ether)s
Authors: Kricheldorf Hans R. , Jahnke Petra
Published: April 2003

Three poly(pyrazine‐ether)s were prepared from 2,6‐dichloropyrazine, silylated bisphenol‐A and, in two cases, 4,4′‐dichlorodiphenylsulfone. The alkylation of these poly(pyrazine‐ether) with methyl triflate, dimethyl sulfate, methyl 4‐nitrobenzenesulfonate, or γ‐propanesultone was studied by 1H‐NMR spectroscopy in nitrobenzene. Several N‐methylated poly(pyrazine‐ether)s were also isolated and characterized by elemental analyses, inherent viscosities, 1H‐NMR spectra, 15N‐NMR spectra, and DSC measurements. Furthermore, their solubilities in six different solvents were determined. Complete methylation raises the glass transition temperatures, reduces the solubility in aprotic solvents, and favors dissolution in methanol or ethanol.
Oxidations of alkenes catalyzed by a Mn(III) porphyrin and cationic polymer latexes
Authors: Zhu Weiming , Ford Warren T.
Published: April 2003

Three types of cationic polymer latexes were prepared by emulsion copolymerization of vinylbenzyl chloride, divinylbenzene and a third monomer, vinyl octadecyl ether, styrene, or n‐decyl methacrylate, followed by quaternization with trimethylamine. The latexes had 44–71 nm diam and polydispersity indices of 1.06–1.10. Vinyl octadecyl ether did not copolymerize but hydrolyzed under the polymerization conditions to produce 1‐octadecanol, which as a coemulsifier gave highly viscous latexes. The tetraanion 5,10,15,20‐tetrakis‐(2,6‐dichloro‐3‐sulfonatophenyl) porphinatomanganese (III) chloride bound irreversibly to the cationic latexes and was an active catalyst for oxidations of alkenes by sodium hypochlorite and potassium peroxymonosulfate in the absence of added organic solvent. The porphyrin catalyst in the latexes was more active than in solution. Porphyrin catalysis gave epoxides concurrently with competing uncatalyzed hypochlorous acid oxidations to complex mixtures of allylic chlorides, allylic alcohols, α,β‐unsaturated ketones, and chlorohydrins.
The synthesis of a mesogenic poly(azine‐ether) by polyetherification via cesium diphenoxides and α,ω‐dibromoalkanes
Authors: Cimecioglu A. L. , Weiss R. A.
Published: April 2003

The synthesis of a poly(azine–ether) via Williamson etherification using the cesium salt of 4–hydroxyacetophenone azine and 1,10–dibromodecane was carried out in N‐methyl–2–pyrrolidone. The heterogeneous reaction proceeded readily at temperatures from ambient to 150°C. Polymers of varying molecular weight with essentially alkyl bromide end groups were produced either by changing the polymerization temperature or by using an excess of the organic substrate. The thermal stability of the polymers was molecular weight dependent and those with the highest DPn exhibited monotropic nematic mesomorphism.
A fluorine‐containing hydrophobically associating polymer. I. Synthesis and solution properties of copolymers of acrylamide and fluorine‐containing acrylates or methacrylates
Authors: Zhang Y.‐X. , Da A.‐H. , Butler G. B. , Hogen‐Esch T. E.
Published: April 2003

Fluorine‐containing hydrophobically associating polymers have been synthesized by copolymerization of acrylamide with a small amount of an acrylate or methacrylate having a fluorocarbon containing ester group. It was found that hydrophobic associations occurring between these fluorocarbon chains was stronger than the interactions of the corresponding hydrocarbon comonomers and depend on the length of the fluorocarbon chain. The rheological properties of the copolymer solutions were studied. The solutions were found to be highly pseudoplastic but the viscosity loss was completely reversible upon removal of shear. Evidence for hydrophobic association of the fluorocarbon groups was obtained by the dependence of the Brookfield viscosity on temperature, the addition of NaCl, and the addition of organic solvents, urea, and surfactants.
Perfluorinated anion exchange membranes: Preparation and preliminary tests of dialysis
Authors: Elmidaoui Azzeddine , Belcadi Said , Houdus Yves , Cohen Thierry , Gavach Claude
Published: April 2003

Using the preirradiation technique a kinetic study of the grafting of the 4‐vinyl pyridine (V4P) and an aliphatic ammonium monomer (ALAM) onto the copolymer film of ethylene–tetrafluoroethylene (ETFE) has been performed. The influence of dose, temperature, and concentration of monomer, reticular agent, and inhibitor were investigated. The results are discussed on the basis of the interactions between monomer diffusibility and viscosity of the medium. The characteristics of some membranes were determined. Their applicability to the recovery of acid by dialysis is demonstrated.
On the behavior of organophosphorus lactam derivatives during anionic polymerization of ε‐caprolactam
Authors: Mateva R. , Dencheva N.
Published: April 2003

This article deals with the anionic polymerization of ε‐caprolactam in the presence of N‐substituted phosphorus‐containing derivatives of ε‐caprolactam: diethyl‐(N‐caprolactam)‐phosphonite (PL1); diethyl‐(N‐caprolactam)‐phosphonate (PL2), and 2,5‐dichlorophenyl‐bis‐(N‐caprolactam)‐phosphinate (PL3). It has been found out that PL1 and PL3 had an accelerating effect on the anionic polymerization of ε‐caprolactam. The polymerization runs at high velocity and high degree of conversion. PL2 does not accelerate the anionic polymerization of ε‐caprolactam, but when the polymerization is activated by a strong activator of acyl lactam type, and the PL2 concentration is commensurate with that of the activator, the process runs at a slightly lower rate and at a relatively high degree of conversion. The kinetics of the anionic polymerization in the presence of the three compounds was investigated. Equations describing the effect of the reagents on the polymerization rate were suggested. The activating energy of the polymerization was found out. The different actions of PL1, PL2, and PL3 during the anionic polymerization of ε‐caprolactam were explained by their structural differences.
Melt‐polymerizable bisimido‐bisphthalonitriles containing silicon, fluoro, and ether groups: Synthesis, characterization, and NMR study
Authors: Kumar Devendra , Razdan Uday , Gupta Alka D.
Published: April 2003

Various melt‐polymerizable bisimido‐bisphthalonitrile polymer precursors were synthesized by the reaction of 4‐aminophthalonitrile (4‐APN) with bis(3,4‐dicarboxyphenyl) dimethylsilane dianhydride (SIDA), 4,4′‐hexafluoroisopropylidene diphthalic anhydride (6FDA), bis(3,4‐dicarboxyphenyl)ether dianhydride (ODPA), and 3,3′, 4,4′‐tetracarboxylichenzophen+ne dianhydride (BTDA) in an aprotic solvent. The synthesized monomers showed crystalline melting at 269 and 271°C. Elemental analysis, differential thermal analysis (DTA), infrared (IR), nuclear magnetic resonance (1H‐NMR) and mass spectral studies were carried out to characterize the synthesized monomers. Thermogravimetric analysis (TGA) of the synthesized monomers showed their thermal stability at 410–400°C. A detailed study and NMR investigation of the first step of condensation reaction was carried out and indicated the formation of a transient charge transfer complex. Thermal cyclization of the formed intermediate, however, gave the required monomers. A preliminary study demonstrated that melt‐polymerization of the synthesized monomers gave thermallystable, tough polymers.
Preparation of poly(2,4‐dichloro‐6‐vinyl‐1,3,5‐triazine‐co‐styrene)s as polymer supports containing two replaceable groups in monomer unit
Authors: Kondo Shuji , Yamamoto Takashi , Mase Masahito , Kunisada Hideo , Yuki Yasuo
Published: April 2003

Poly(2,4‐dichloro‐6‐vinyl‐1,3,5‐triazine‐co‐styrene)s were prepared by the reaction of poly(2,4‐diamino‐6‐vinyl‐1,3,5‐triazine‐co‐styrene)s with hydrochloric acid, and followed by treatment with thionyl chloride and N,N‐dimethylformamide. The chlorine atoms in the resulted polymers were replaced readily by several nucleophiles such as amide, alkoxide, and mercaptide to afford the corresponding polymers in moderate yields. Among these, polymers containing oligo (oxyethylene) groups at both 2 and 4 positions of 1,3,5‐triazine ring worked effectively as phase transfer catalysts for the reaction of n‐octyl bromide with alkali metal thiocyanates in toluene–water systems. However, polystyrenes containing only one oligo (oxyethylene) group in monomer unit scarcely exhibited the activity under these conditions although the degree of loading of the functional group was almost the same. The activity depended on the number of oxyethylene units, and the selectivity to alkali metal ions was also observed. © 1992 John Wiley & Sons, Inc.
Synthesis and characterization of graft copolymers of methacrylonitrile/methacrylate mixtures onto amylomaize by the ceric ion method
Authors: Vázquez B. , Goñi I. , Gurruchaga M. , Valero M. , Guzmán G. Martín
Published: April 2003

Graft polymerizations of mixtures of methacrylonitrile with n‐alkyl methacrylales onto amylomaize were carried out. The graft copolymers were characterized by both IR and 13C‐NMR spectroscopies. The influence of the monomer feed on the grafting parameters has been studied. The variation of these parameters with the mole fraction of methacrylate in the feed for the first three systems studied, MAN/MMA, MAN/EMA and MAN/BMA, was similar: thus, percent grafting (%G, percent weight of grafted polymer with respect to grafted amylomaize), percent grafted amylomaize (%GA, percent weight of grafted amylomaize with respect to initial amylomaize), percent grafting conversion (%Cg, percent weight of grafted polymer with respect to initial monomer), and percent total conversion (%Ct, percent weight of total acrylic polymer with respect to initial monomer) were increased, but percent grafting efficiency (%GE, percent weight of graft copolymer with respect to total polymer) decreased. The system MAN/HMA presented values of grafting parameters lower than those of the previous systems. The optimum values were obtained at 0.6 HMA mole fraction in the monomer feed. When the number of carbon atoms of the n‐alkyl group rises from 1 to 4, the increase of the n‐alkyl group length gives rise to increases of the %G %Cg and %Ct values and decreases of the %GE and %GA values. For the largest methacrylate, the grafting reaction appears to be controlled by the lesser accessibility of the monomer to the active sites of the carbohydrate. © 1992 John Wiley & Sons, Inc.
Chemical reactions and reactivity of primary, secondary, and tertiary diamines with acid functionalized polymers
Authors: Song Zhiqiang , Baker Warren E.
Published: April 2003

Reactive melt processing of different types of diamines with polyethylene containing carboxylic acid groups and polystyrene containing anhydride groups was carried out. The reactivity of primary, secondary, and tertiary diamines with these acid polymers was determined using various techniques. Molecular weight increases due to crosslinking were observed through (1) changes in the torque during the reactive processing, (2) decrease in melt flow indices, and (3) decrease in solubility of the reaction products. The chemical compositions of the reaction products were examined by Fourier transform infrared (FTIR) spectroscopy. Thermal analysis using differential scanning calorimetry (DSC) was carried out to determine the crystallization behavior, glass transition temperatures, and thermal stabilities of the reaction products. Results show that the primary amine is the most reactive towards carboxylic acid or anhydride groups followed by the secondary and then the tertiary amine. Anhydride groups on polymers are of higher activity towards secondary or primary amino groups than carboxylic acid groups in the nucleophilic acyl substitution reactions. Reaction products crosslinked with the primary diamine are less stable than their parent acidic polymers. On the other hand, crosslinking with the secondary or tertiary diamine gives products with higher thermal stability than the parent acidic polymers. The formation of reversible and irreversible crosslinks with different types of diamines is also reported. © 1992 John Wiley & Sons, Inc.
The kinetics of polyolefin oxidation in aqueous media
Authors: Henry Jacqueline L. , Ruaya Ascencion L. , Garton Andrew
Published: April 2003

The thermal oxidation, at 75–92°C, of antioxidant‐free low‐density polyethylene (LDPE) is faster in most aqueous environments than in air. The accelerative environments include water, solutions of sodium salts, and a basic buffer. However, an acidic buffer retards oxidation. Transition metal salts are not examined here since their catalytic effect is wellknown. The acceleration is predominantly a surface phenomenon, and so is most obvious in thin polymer films. For antioxidant‐containing polyolefins, complications arise because of the possibility of extraction of stabilizers, but the trend in oxidative lifetime is similar to that of the antioxidant‐free specimens, and the antioxidants are observed to react chemically during the aging process. For example, a commercial crosslinked polyethylene (XLPE) shows a reduction in thermo‐oxidative lifetime of at least a factor of two in aqueous environments compared to air. High‐density polyethylene (HDPE) and polypropylene (PP) show similar behavior, but the magnitude of the effect of aqueous environments is less. This phenomenon is discussed in terms of nucleophilic attack by peroxy anions on hydroperoxides.
Amphiphilic gels for peptide synthesis
Authors: Arshady Reza , Fallah Fereidoon
Published: April 2003

A new class of “amphiphilic” copoly(styrene‐acrylamide)s of potential interest for peptide synthesis is described. As examples of the new polymers, those carrying nitrophenol or piperazine functionality were used for model reactions in peptide synthesis, and were found to be substantially more efficient than similar reagents derived from polystyrene, polydimethylacrylamide or silica gel. Due to their amphiphilic structure, the new resins have general substrate compatibility and are permeated by all of the commonly used solvents, including toluene and ethyl acetate on the one hand, through dimethylformamide, to dimethylsulfoxide and water on the other. The improved performance of the new polymers is attributed to their alternating amphiphilic structure and favorable polymer–solvent–substrate interactions. © 1992 John Wiley & Sons, Inc.
Metal arene complexation of polybenzyl: Preparation and methylation
Authors: Baumberger Thomas R. , Woolsey Neil F.
Published: April 2003

Polybenzyl has been complexed with the chromium tricarbonyl moiety by thermal treatment with chromium hexacarbonyl. The aryl rings of the product were complexed with the chromium tricarbonyl moiety to the extent of 41–63%. Assessment of the degree of complexation was satisfactorily carried out by elemental chromium analysis or by 13C‐NMR methods which agreed within 5%. GPC was less satisfactory. TGA analysis of the complexed polymers suggested the possibility of cross‐linking on thermal treatment. The benzylic groups of the polymer complex were methylated with base and methyl iodide in up to 88% of the complexed arene activated methylene groups. © 1992 John Wiley & Sons, Inc.
Poly(3,3′‐dimethoxy‐2,2′‐bithiophene): Synthesis and comparison with poly(3‐methoxythiophene)
Authors: Hasik Magdalena , Laska Jadwiga Ewa , Pron Adam , Kulszewicz‐Bajer Irena , Koziel Krzysztof , Lapkowski Mieczyslaw
Published: April 2003

A new electroactive polymer, namely poly(3,3′‐dimethoxy‐2,2′‐bithiophene) has been prepared by voltammetric polymerization of 3,3′‐dimethoxy‐2,2′‐bithiophene. Due to a different coupling pattern (equivalent to “head‐to‐head,” and “tail‐to‐tail” coupled alkoxythiophene rings), poly(3,3′‐dimethoxy‐2,2′‐bithiophene) exhibits different voltammetric properties than the corresponding “head‐to‐tail” coupled polymer, i.e., poly(3‐methoxythiophene). Poly(3,3′‐dimethoxy‐2,2′‐bithiophene) gives very sharp oxidation and reduction peaks indicating an abrupt insulator to conductor transition. This hypothesis was corroborated by the studies of relative resistance as a function of electrode potential. Sharper and better‐defined redox peaks may indicate better stereoregularity of poly(3,3′‐dimethoxy‐2,2′‐bithiophene) as compared to poly(3‐methoxythiophene) since in this compound the 5,5′‐coupling positions are geometrically equivalent and no coupling defects are expected. © 1992 John Wiley & Sons, Inc.
The mechanical and magnetic alignment of liquid crystalline epoxy thermosets
Authors: Barclay G. G. , McNamee S. G. , Ober C. K. , Papathomas K. I. , Wang D. W.
Published: April 2003

The processing of a new series of liquid crystalline (LC) epoxy networks was evaluated. Above the glass transition temperature, the low crosslink density networks could be mechanically aligned. The mechanically oriented networks readily lost orientation upon heating. Highly anisotropic liquid crystalline (LC) epoxy networks were also prepared by aligning the mesophase of the prepolymer during the curing process under the influence of a magnetic field. Orientation parameters (f) of 0.13 to 0.57 were achieved by these processes as determined by x‐ray diffraction analysis. The ability of the magnetically aligned networks to retain their orientation above the glass transition temperature was determined by time‐resolved x‐ray diffraction. The stability of the alignment of these networks was found to depend on crosslink density. The effect of the anisotropy of these networks was investigated by measuring the coefficient of thermal expansion (CTE). In the aligned networks, there was a substantial reduction in CTE parallel to the direction of the applied field compared to the randomly oriented networks. © 1992 John Wiley & Sons, Inc.
New poly(amide‐imide)s syntheses. I. Soluble high‐temperature poly(amide‐imide)s derived from 2,5‐bis(4‐trimellitimidophenyl)‐3,4‐diphenylthiophene and various aromatic diamines
Authors: Yang Chin‐Ping , Yen Yung‐Yu
Published: April 2003

Novel aromatic poly(amide‐imide)s with high inherent viscosities were prepared by direct polycondensation reaction of 2,5‐bis(4‐trimellitimidophenyl)‐3,4‐diphenylthiophene (IV) and aromatic diamines using triphenyl phosphite in the N‐methyl–2‐pyrrolidone (NMP)/pyridine solution containing dissolved CaCl2. The diimide‐diacid IV was readily obtained by the condensation reaction of 2,5‐bis(4‐aminophenyl)‐3,4‐diphenylthiophene (III1) with trimellitic anhydride. The obtained poly(amide‐imide)s showed high thermostability. Their decomposition temperatures at 10% weight loss in nitrogen atmospheres were above 550°C and the anaerobic char yield at 800°C ranged from 48 to 68%. Almost all the poly(amide‐imide)s showed high glass transition temperatures above 300°C by differential scanning calorimetry (DSC) measurements. These polymers were readily soluble in various organic solvents and could be cast into transparent, tough, and flexible films. Their casting films showed obvious yield points in the stress‐strain curves and had strength at break up to 74.2 MPa, elongation to break up to 70.1%, and initial modulus up to 4.56 GPa. The factors affecting the reaction of diimide‐diacid IV and 4,4′‐oxydianiline in view of monomer concentration, reaction temperature, and amount of CaCl2 were also investigated. © 1992 John Wiley & Sons, Inc.
Characterization of conducting copolymers of 2,2′‐bithiophene and pyrrole by cyclic voltammetry and UV/visible spectroscopy
Authors: Peters Eric M. , Van Dyke John D.
Published: April 2003

Several polymers have been prepared by electropolymerization of mixtures of pyrrole (PY) and 2,2′‐bithiophene (BT). Cyclic voltammetry on prepared polymer films shows three anodic oxidation peaks, two of which match the oxidation potentials of homopolymeric PY and BT, and a third which is intermediate. UV/visible spectroscopy displays a unique spectrum for each of the reduced and oxidized forms of these polymers. Nernstian plots from UV/visible data exhibit three well‐defined redox couples in polymer films produced at 1.3 V. Overall, the data strongly support the formation of a copolymer, consisting of three distinct oxidizable units. Two of these can be attributed to short blocks of either PY or BT, and a third to random and alternate groupings of PY and BT. The polymers produced are electrically conductive, but the conductivity drops rapidly as BT units are introduced into a homopolymer of PY. © 1992 John Wiley & Sons, Inc.
Autoxidation of 2‐mercaptoethanol catalyzed by cobalt(II) phthalocyaninetetrasulfonate on colloidal particles
Authors: Babu Sunkara Hari , Ford Warren T.
Published: April 2003

Cobalt(II) phthalocyaninetetrasulfonate (CoPcTS) is a highly active catalyst in aqueous media for the autoxidation of thiols to disulfides, and cationic polymers further enhance the activity. In this work we tested a variety of cationic polymer supports for the CoPcTS‐catalyzed autoxidation of 2‐mercaptoethanol in aqueous dispersions at 25°C. The order of activities is cationic polyelectrolytes > cationic polymer colloids > cationic colloidal silica > aqueous solution > ion exchange resins. Spectroscopic studies indicate that the high activity of the polyelectrolytes correlates with their ability to aggregate the CoPcTS. © 1992 John Wiley & Sons, Inc.
Mechanism of anionic polymerization of phenylacetylene
Authors: Kobryanskii V. M.
Published: April 2003

Anionic polymerization of phenylacetylene in the presence of butyllithium has been studied. It was shown that the process of polymerization is accompanied by the appearance and growth of the ESR signal with pronounced superfine structure. The model of polymerization was suggested according to which formation of low molecular polyphenylacetylene is caused the destruction of the active centers by means of electron transfer from the active center to the conjugated chain. This type of electron transfer may also be the fundamental reaction limiting the chain length in cationic polymerization of acetylene monomers. © 1992 John Wiley & Sons, Inc.
Optically clear simultaneous interpenetrating polymer networks based on poly(ethylene glycol) diacrylate and epoxy. I. Preparation and characterization
Authors: Lin Mu‐Shih , Jeng Kuen‐Tay
Published: April 2003

Poly(ethylene glycol) diacrylate was synthesized from poly(ethylene glycol) of molecular weight 600 with acryloyl chloride in a molar ratio of 1:2. Poly(ethylene glycol) diacrylate (PEGDA) was then blended with diglycidyl ether of bisphenol A (DGEBA) in various ratios, followed by curing with 2,2′‐azobisisobutyronitrile (AIBN) and isophronediamine (IPDA) simultaneously. Viscosity changes before and during IPN formation were examined with a Brookfield viscometer. Formation of H‐bonding and functional group changes were investigated with FTIR. Exothermic curing thermograms were recorded with dynamic DSC. Optically clear IPNs thus obtained were characterized with rheometric dynamic spectroscopy (RDS) and scanning electron microscopy (SEM) to check possible compatibility of the two networks. Experimental results revealed that during IPN formation hydrogen bonds between PEGDA and DGEBA and interlock of networks had profound effect on viscosity change and pot‐life. Complete compatibility of the IPNs was found as DGEBA content was higher than 50% by weight. The compatibility between PEGDA and DGEBA networks was evidenced from inner shift of a single damping peak in RDS. In the meantime, SEM micrographs confirmed the coincidence with the result of RDS © 1992 John Wiley &Sons, Inc.
N‐alkoxy‐pyridinium and N‐alkoxy‐quinolinium salts as initiators for cationic photopolymerizations
Authors: Yaḡci Y. , Kornowski A. , Schnabel W.
Published: April 2003

The polymerization of n‐butyl vinyl ether (BVE), cyclohexene oxide (CHO) and 3,4‐epoxycyclohexyl(methyl)‐3′,4′‐epoxycyclohexane carboxylate (EEC) was initiated upon UV irradiation (λinc > 300 nm) of dichloromethane solutions containing N‐ethoxy‐2‐methylpyridinium (V), N‐ethoxy‐4‐phenyl‐pyridinium (VI) or N‐ethoxy‐isoquinolinium hexafluorophosphate (VII). Whereas the bifunctional EEC was converted into an insoluble gel, BVE and CHO formed polymers of molar mass: Mw = 2 X 104−2 X 105 (PCHO) and Mw ≈ 2 X 104 (PBVE). Protons are formed with a rather high quantum yield [ø(H+) = 0.48 on irradiating VII in dichloromethane; titration with sodium p‐nitrophenolate] and it is, therefore, assumed that the polymerization is initiated by photochemically generated protons. © 1992 John Wiley & Sons, Inc.
Synthesis of aromatic poly(thioether ketone)
Authors: Ueda Mitsuru , Abe Tetsuya , Oda Mitsuo
Published: April 2003

Aromatic poly(thioether ketone)s were prepared by the direct polycondensation of aromatic dicarboxylic acids with aryl compounds containing ether or sulfide structures using phosphorus pentoxide/methanesulfonic acid (PPMA) as a condensing agent and solvent. Polycondensation proceeded smoothly and produced aromatic poly(thioether ketone)s with inherent viscosities up to 0.73 dL/g. The synthesis of substituted aryl ketones by the reaction of substituted benzoic acids with aryl compounds in PMMA was studied in detail to demonstrate the feasibility of the reaction for polymer formation. The thermogravimetry of the aromatic poly(thioether ketone)s showed a 10% weight loss in air and nitrogen at around 450 and 460°C, respectively. © 1992 John Wiley & Sons, Inc.
Chlorothioxanthone‐Onium salts: Efficient photoinitiators of cationic polymerization
Authors: Manivannan G. , Fouassier J. P. , Crivello J. V.
Published: April 2003

The interaction of iodonium, sulphonium, phosphonium, arsonium, selenonium, and heterocyclic nitrogen salts with the excited triplet state of 2‐chlorothioxanthone (CTX) has been studied through time‐resolved laser spectroscopy. Bimolecular quenching rate constants (ke) have been measured for the first time. Measuring of the rate constants (kq) of the quenching reaction by monomers permits the calculation of charge transfer (øCT) quantum yields. © 1992 John Wiley & Sons, Inc.
Plasma polymerization of cyano compounds
Authors: Inagaki N. , Tasaka S. , Yamada Y.
Published: April 2003

Plasma polymerizations of three cyano compounds—acrylonitrile (AN), 1,2‐dicyanoethylene (FN), and tetracyanoethylene (TCE)—were investigated by FT IR and XPS, and the transforamtion of cyano groups during the plasma polymerization was discussed. The results pointed out an aspect of the preparation of plasma films with cyano groups. Plasma polymerizations of AN, FN, and TCE deposited brown or dark brown films that contained carbon, nitrogen, and oxygen. The elemental composition of the plasma films, especially N/C atomic ratio, showed a monomer dependence but no rf power dependence. The plasma films contained amide and amino groups, and ketene‐imine and conjugated — C = N — structures as well as cyano groups as nitrogen functionalities, and carbonyl and carboxyl groups as oxygen functionalities. For the preparation of plasma films with cyano groups, compounds with more than two cyano groups themselves are not suitable as monomers. The operation of plasma polymerization under mild plasma conditions at low rf power and in no oxygen atmosphere is favorable for the preparation of plasma films with cyano groups. © 1992 John Wiley & Sons, Inc.
Kinetics and mechanism of emulsifier‐free emulsion polymerization. III. Particle growth mechanism of seeded styrene/potassium persulfate system
Authors: Chen Show‐An , Chang Herng‐Show
Published: April 2003

For seeded emulsifier‐free emulsion polymerizations of styrene/potassium persulfate (KPS)/water system using the three sizes of seeds: 1020, 1620, and 1923 Å, analysis on the data of conversion and MWD suggests a shell region polymerization mechanism for the particle growth period as the particle diameter is larger than about 1500–2000 Å. The shell region has thickness of about 100 Å. The occurrence of shell region polymerization is attributed to the higher average number of radicals per particle (n ≑ 2−7) for the large particle, causing the polymer radicals (with the sulfate ends anchoring on the particle surface) to be terminated by combination at lower MW. Thus, the radical ends have no chance to arrive at the core of the particles. As the smallest seed is used, the rate of polymerization is of zero order, the same as in the conventional emulsion polymerization. MW of the polymer produced in the cases, in which the shell region polymerization occurs, increases with conversion in the entire process, different from the conventional case in which the MW increases first up to about 60% conversion and then decreases. © 1992 John Wiley & Sons, Inc.
Model reactions of amine curing of glycidylamine epoxy resins: Homopolymerization of N‐methylglycidylaniline
Authors: Matĕjka Libor , Podzimek S˘tĕpán , Simonsick William J. , S̆pac̆ek Pavel , Dus̆ek Karel
Published: April 2003

The kinetics of homopolymerization of the monofunctional epoxide N‐methylglycidylaniline in the presence of a tertiary amine or an amino alcohol has been followed by reversed phase high performance liquid chromatography and size exclusion chromatography. The reaction products were identified by mass spectrometry using potassium ionization of desorbed species (K+IDS). 1,3‐Di‐N‐methylanilino‐2‐propanol (P) was the main reaction product and low molecular weight oligomers with Mn > 600 were also formed. The molecular weight and fraction of oligomers decrease with increasing concentration of the initiator. The suggested complex reaction mechanism involves formation of four stable oligomeric series initiated by reaction of the epoxide with either an OH group of (a) the amino alcohol, (b) product P, (c) traces of water, or (d) the tertiary amine to form ionic species resulting in the ionic propagation. Regeneration of the initiator and formation of new initiating centers during the polymerization are the causes of low molecular weights of oligomers. © 1992 John Wiley & Sons, Inc.
Synthesis and characterization of thermally reversible macroporous poly(N‐isopropylacrylamide) hydrogels
Authors: Wu Xue Shen , Hoffman Allan S. , Yager Paul
Published: April 2003

Macroporous hydrogels are characterized by large pore sizes, high pore volumes, and high specific surface area. Besides these characteristics, macroporous hydrogels based on thermally reversible polymers respond to temperature changes much faster than hydrogels prepared by a conventional method. Crosslinked poly(N‐isopropylacrylamide) (polyNIPAAm) forms a thermally reversible hydrogel which shows a lower critical solution temperature (LCST) ca. 33°C in aqueous solutions. We have synthesized thermally reversible polyNIPAAm hydrogels having macroporous structures by a new method. These macroporous hydrogels have large pore volumes, large average pore sizes, and faster macromolecule permeation rates in comparison to conventional polyNIPAAm hydrogels synthesized by a conventional method. Compared with conventional polyNIPAAm hydrogels, the macroporous polyNIPAAm hydrogels have higher swelling ratios at temperatures below the LCST and exhibit faster deswelling and reswelling rates. The deswelling rates are especially rapid. These thermally reversible macroporous hydrogels may be very useful in controlled active agent delivery and toxin removal, as well as dewatering of solutions. Peptides or proteins may behave as if they were in bulk solution within the large aqueous pores, and this may reduce their inactivation when such gels are used for their storage and later release. The gels may also be useful in microrobotic devices due to their fast response to temperature. © 1992 John Wiley & Sons, Inc.
Characterization of the changes in the initial morphology for MgCl2‐supported Ziegler‐Natta polymerization catalysts
Authors: Ferrero M. A. , Koffi E. , Sommer R. , Conner W. C.
Published: April 2003

Recently considerable detail has become available on the initial morphology and the morphological changes that occur for silica based Cr catalysts for ethylene polymerization. These catalysts are produced as a dry powder and may be employed either in gas phase or in slurry processes. MgCl2‐supported Ziegler‐Natta polymerization catalysts are often prepared and employed as slurries. They usually are never dried and thus few studies have employed the spectra of physical techniques common to the characterization of pore structure. In the current study, we have carefully removed the solvent for both ball‐milled and precipitated MgCl2‐supported catalysts. These catalysts are characterized by physical sorption, mercury porosimetry, and electron microscopy both as prepared and during the initial stages of polymerization (to ∼ 100 g of polymer/g of catalyst). We find that the initial catalyst may be represented by a complex agglomerate of small crystallites as contrasted with the branched pore network found in Cr/silica catalysts. As a result, it is concluded that the initial fragmentation of the MgCl2 based systems is more uniform as contrasted with the progressive fragmentation of the silica‐based system. This fragmentation mechanism facilitates the retention of greater polymer/catalyst surface during the initial stages of the polymerization. © 1992 John Wiley & Sons, Inc.
Preparation of copolymer microspheres of diethylene glycol dimethacrylate
Authors: Naka Yukihiko , Yamamoto Yukio
Published: April 2003

Preparation of copolymer microspheres of diethylene glycol dimethacrylate (2G) with several comonomers by radiation‐induced radical polymerization is described. Ethyl methacrylate (EMA), acrylamide, maleic anhydride, and styrene gave microspheres successively. The copolymerization resulted in gelation more easily than the 2G homopolymerization. The allowed ratio of copolymerization is up to about 0.4 as the mole fraction of comonomer for the solution containing 10 vol % 2G monomer. Copolymerization affected the size of microspheres by keeping its narrow distribution. The size of microspheres was increased by the copolymerization with EMA and styrene and, was decreased with acrylamide. The formation of microsphere strongly depends on the crosslinking ability of monomers. The crosslinking ability and reactivity in the copolymerization cause the change of the size of the microspheres. © 1992 John Wiley & Sons, Inc.
Free‐radical copolymerization of styrene with N‐phenyl maleimide initiated by thiol
Authors: Cheng Haitao , Zhao Guoqiang , Yan Deyue
Published: April 2003

2‐Methyl–2‐undecanethiol was found efficient to initiate the free‐radical copolymerization of styrene (St) with N‐phenyl maleimide (NPMI) at 40°C. The initial copolymerization rate increases with the increasing of thiol concentration at first, then keeps constant with the further increasing of the thiol concentration. The charge‐transfer complex (CTC) formed between St and NPMI was investigated in different solvents by using 1H‐NMR. There is no definite correlation between CTC equilibrium constant, K, and the polarity of the solvent. With the increasing of CTC concentration, both the copolymerization rate and NPMI content in copolymer enhances, indicating the participation of CTC in both initiation and propagation. The monomer reactivity ratios were calculated to be rNPMI = 0.052 and rSt − 0.166, showing an alternating tendency for the copolymerization of St with NPMI. The molecular weight approach has shown again the effect of CTC. The function of thiol as a regulator is mitigated due to the involvement of CTC. © 1992 John Wiley & Sons, Inc.
Para‐Xylylenes and analogues by base‐induced elimination from 1,4‐bis‐(dialkylsulfoniomethyl)arene salts in poly(1,4‐arylene vinylene) synthesis by the wessling soluble precursor method
Authors: Denton Frank R. , Sarker Ananda , Lahti Paul M. , Garay Raul O. , Karasz Frank E.
Published: April 2003

para‐Xylylenes are generated by treatment of various 1,4‐bis(dialkylsulfoniomethyl)arene dihalides with base in water, methanol, and aqueous acetonitrile, as shown by UV‐Vis spectroscopy. This procedure allows the monitoring of the transient xylylene monomers that yield polyelectrolyte precursor polymers for poly(arylene vinylene)s, formed by variations of the chemistry developed originally by Wessling and co‐workers. Alkoxy, alkyl, and halogen ring substituents on the sulfonium salt precursors do not greatly affect the ability to generate and observe the growth and decay of steady‐state concentrations of the para‐xylylene intermediates. Use of strong resonance‐acceptor substituents—such as cyano or nitro—on the ring reduces production of a strong para‐xylylene absorption, possibly due to reluctance of the ylides initially formed from the bis‐sulfonium salts to eliminate to the xylylenes. By variation of UV‐Vis conditions, it was found that use of 20% aqueous acetonitrile rather than water allowed formation of low to modest molecular weight polyelectrolytes in cyano‐substituted cases (Mw = 8000–37,000). Use of UV‐Vis test experiments should be useful for screening of bis sulfonium salt precursors that may be expected to give high molecular weight polyelectrolytes—in cases where para‐xylylene formation is easy—as well as for finding reaction conditions that will optimize polymer formation. © 1992 John Wiley & Sons, Inc.