摘要:

AbstractThis work describes the preparation of polypyrrole and EPDM rubber blends, PPy/EPDM, by the sorption of pyrrole (vapor phase) in an EPDM matrix containing CuCl2. We investigated the effect of the oxidant particle‐size on the sorption and polymerization equilibrium, electrical conductivity, and mechanical properties of the blends. Independently of the CuCl2concentration and polymerization time, the polypyrrole weight fraction in the blend,Xppy, increases when the oxidant particle‐size in changed from 150–250 μm to smaller than 106 μm. For blends containing 50 phr of CuCl2, obtained following 72 h of exposure to pyrrole, an increase in the Young's Modulus (from 2.2 ± 0.2 to 3.9 ± 0.6 MPa) and an increase in the electrical conductivity (from 10−9to 10−7S cm−1) was observed when the oxidant particle‐size was decreased. Infrared spectroscopy, thermogravimetric analysis, scanning differential calorimetry, and scanning electron microscopy were used in sample characterization. © 1994 Jo

ISSN:0887-624X    

DOI:10.1002/pola.1994.080320601

出版商:John Wiley&Sons, Inc.    

年代:1994

数据来源: WILEY

摘要:

AbstractMonomer partitioning in emulsion copolymerization plays a key role in determining composition drift and polymerization rates. The combination of recently developed thermodynamically based monomer partitioning relationships with mass balance equations, makes predictions of monomer partitioning in emulsion copolymerizations possible in terms of monomer mole fractions and monomer concentrations in the particle and aqueous phases. Using this approach, the effects of monomer to water ratios and polymer volumes on the monomer mole fraction within the polymer particle phase in a nonpolymerizing system at thermodynamic equilibrium can be determined. Comparison of these monomer partitioning predictions with experiments for the monomer system methyl acrylate—vinyl acetate shows good agreement. Furthermore, composition drift occurring in a polymerizing system as a function of conversion can be predicted if the assumption is made that equilibrium is maintained during reaction. Comparison of predictions with experimental results for emulsion copolymerizations of the monomer systems methyl acrylate—vinyl acetate and methyl acrylate—indene shows good agreement. © 1994 John Wiley&Son

ISSN:0887-624X    

DOI:10.1002/pola.1994.080320602

出版商:John Wiley&Sons, Inc.    

年代:1994

数据来源: WILEY

摘要:

AbstractChemical reactivity of β‐chitin isolated from squid pens has been examined in various reactions to elucidate the possibility of facile modifications in simple manners leading to the preparation of derivatives with well‐defined structures. β‐Chitin swelled in common solvents such as methanol and pyridine unlike the ordinary α‐chitin and exhibited much higher reactivity than β‐chitin. Free amino groups present in β‐chitin were easily and selectively acetylated with acetic anhydride in methanol to give chitin with a uniform structure, poly(N‐acetyl‐D‐glucosamine). When acetylation reaction was carried out in pyridine,O‐acetylation proceeded smoothly besidesN‐acetylation. In the presence of 4‐dimethylaminopyridine as the catalyst, even full acetylation was achieved under mild conditions. Tosylation was also quite efficient in pyridine without side reactions such asN‐deacetylation which is unavoidable in the tosylation of α‐chitin. β‐Chitin also enabled direct tritylation in pyridine in the presence of 4‐dimethylaminopyridine. All these reactions were quite sluggish with β‐chitin, and no reactions or only very low extents of substitution were observed, indicating the high potential of β‐chitin as a versatile starting material for facile modific

ISSN:0887-624X    

DOI:10.1002/pola.1994.080320603

出版商:John Wiley&Sons, Inc.    

年代:1994

数据来源: WILEY

摘要:

AbstractThe enhancement of the activity and productivity of heterogeneous V‐based catalysts in the presence of halogenated additives, has been investigated for high‐temperature ethylene homopolymerization (160°C). The influence of both the nature and structure of various organic halides on polymerization kinetics and on the oxidation state of vanadium derivatives has been examined in detail. Results suggest, as previously reported for lower temperature polymerizations, that the main role of the halogenated derivatives may be accounted for by their oxidizing character. It allows re‐oxidation of the reduced VIIspecies formed during the polymerization process, to valence III. The various pathways able to lead to the formation of new active species from (re‐)formed VIIIare examined and discussed. © 1994 John Wiley&

ISSN:0887-624X    

DOI:10.1002/pola.1994.080320604

出版商:John Wiley&Sons, Inc.    

年代:1994

数据来源: WILEY

摘要:

AbstractSeveral polyelectrolyte complexes were prepared by the reaction of polyalkylviologens [polyethylviologen (PEV2+), polypropylviologen (PPrV2+), and polybutylviologen (PBV2+)] with polyanions [sodium alginic (ALG), sodium polyacrylate (PAA), or sodium polystyrenesulfonate (PSS)]. These complexes were used as electron‐transfer catalysts (ETC) on the debromination of diphenyl bromomethane (Ph2CHBr) under heterophase condition [reductant: Na2S2O4, in H2O (liquid)‐polyelectrolyte complex(S)—Ph2CHBr in CH2Cl2]. The work showed that these complexes could induce the debromination of Ph2CHBr to afford tetraphenyl ethane, and different polyanions in the complexes also affected the mediating abilities. © 1994 John Wiley&Son

ISSN:0887-624X    

DOI:10.1002/pola.1994.080320605

出版商:John Wiley&Sons, Inc.    

年代:1994

数据来源: WILEY

摘要:

AbstractFormation of SiO2–B2O3gel fibers and oxides was investigated by the sol‐gel method using tetraacetoxysilane (TAS) and boron tri‐n‐butoxide (BTB). Low molecular weight borosiloxanes (BS) were formed by the reaction of TAS with BTB in THF. Partial alkoxylation and hydrolysis of BS followed by further condensation of the resulting polymer (PBS) solutions led to the formation of highly polymerized polyborosiloxanes (HPBS) with good spinnability. Gel fibers were obtained by dry spinning of HPBS. The compositions of PBS and gels were not consistent with that in feed. Heat treatment of the gels, however, provided SiO2–B2O3oxides with compositions almost compatible with those of the gels. © 1994 John Wiley

ISSN:0887-624X    

DOI:10.1002/pola.1994.080320606

出版商:John Wiley&Sons, Inc.    

年代:1994

数据来源: WILEY

摘要:

AbstractA new tetraphenylated heterocylic diol, 2,5‐bis(4‐hydroxyphenyl)‐3,4‐diphenylpyrrole, was synthesized in three steps starting from 4‐methoxydeoxybenzoin. The tetraphenylpyrrole‐containing polyarylates having inherent viscosities of 0.28–0.88 dL/g were prepared from the diol and various aromatic dicarboxylic acid chlorides by both phase transfer catalyzed two‐phase polycondensation and high temperature solution polymerization methods. All the polyarylates were semi‐crystalline, and were readily soluble in a variety of solvents includingN‐methyl‐2‐pyrrolidone,mcresol, pyridine, and 1,4‐dioxane. These polymers had glass transition temperatures in the range of 223–279°C, with no weight loss below 400°C in both air and nitrogen atmospheres

ISSN:0887-624X    

DOI:10.1002/pola.1994.080320607

出版商:John Wiley&Sons, Inc.    

年代:1994

数据来源: WILEY

摘要:

AbstractGlycine/glycolic acid based biodegradable copolymers have been prepared by ring‐opening homopolymerization of morpholine‐2,5‐dione, and ring‐opening copolymerization of morpholine‐2,5‐dione and glycolide. The homopolymerization of morpholine‐2,5‐dione was carried out in the melt at 200°C for 3 min using stannous octoate as an initiator, and continued at lower reaction temperatures (100–160°C) for 2–48 h. The highest yields (60%) and intrinsic viscosities ([η] = 0.50 dL/g; DMSO, 25°C) were obtained after 3 min reaction at 200°C and 17 h at 130°C using a molar ratio of monomer and initiator of 1000. The polymer prepared by homopolymerization of morpholine‐2,5‐dione was composed of alternating glycine and glycolic acid residues, and had a glass transition temperature of 67°C and a melting temperature of 199°C. Random copolymers of glycine and glycolic acid were synthesized by copolymerization of morpholine‐2,5‐dione and glycolide in the melt at 200°C, followed by 17 h reaction at 130°C using stannous octoate as an initiator. The morphology of the copolymers varied from semi‐crystalline to amorphous, depending on the mole fraction of glycolic acid residues in

ISSN:0887-624X    

DOI:10.1002/pola.1994.080320608

出版商:John Wiley&Sons, Inc.    

年代:1994

数据来源: WILEY

摘要:

AbstractThe poly(arylene ether)s were prepared by the nucleophillic aromatic substitution polymerization of phenolphthalin and its derivatives with activated aromatic difluorides. The polymers had glass transition temperatures ranging from 210 to 240°C. Though the monomers have no fluorescence, the resulting polymers fluoresced a light green color in solid and solution states. The maximum excitation and emission wavelengths are 420 nm and 470 nm, respectively. In the polymer solutions, the fluorescence intensity decreased gradually, but the intensity was recovered by heating the polymer at 220°C for a few minutes. The fluorescent polymer had a stable radical. A model compound having the same repeating unit of the polymer was also prepared. The fluorescence properties of this model were almost the same as those of the polymers. © 1994 John Wiley&Sons, I

ISSN:0887-624X    

DOI:10.1002/pola.1994.080320609

出版商:John Wiley&Sons, Inc.    

年代:1994

数据来源: WILEY

摘要:

AbstractThe synthesis and characterization of nine polymethacrylates containing 4‐alkoxy‐4′‐trifluoromethyltolane, 4‐alkoxy‐4′‐cyanotolane, and 4‐alkoxy‐4′‐nitrotolane side groups were described in this study. The phase behavior of the prepared monomers and polymers was characterized by differential scanning calorimetry, optical polarizing microscopy, and x‐ray diffraction. All of the obtained monomers exhibit no mesophase, while most of the synthesized polymers reveal enantiotropic mesomorphism. The polymethacrylate containing 4‐propanyloxy‐4′‐nitrotolane side groups was the only one which shows no mesomorphic behavior. Both the spacer length and the nature of terminal groups have profound influence on the phase transition temperatures and thermal stability of the mesophase. The polymers with longer spacers tend to form a more ordered mesophase with a wider temperature range. Among three polymers with the same spacer length, the polymer with a trifluoromethyl terminal end group is inclined to form a more ordered mesophase than the other two polymers. No side chain crystallization occurred for all obtained poly

ISSN:0887-624X    

DOI:10.1002/pola.1994.080320610

出版商:John Wiley&Sons, Inc.    

年代:1994

数据来源: WILEY