摘要:

AbstractThe effect of the thermally initiated frontal polymerization of acrylamide complexes of transition metal nitrates such as those of Mn(II), Co(II), Ni(II), and Zn(II) was disclosed. The rate of the polymerization front propagation was found to be 2−9 × 10−2cm/c, depending appreciably on sample diameter and density, as well as the presence of radical inhibitor additives. The rate was found to decrease in the series: Co(II)>Ni(II)>Mn(II)>Zn(II). Polymerization was shown to occur directly in the melting region of a complex at 80–100°C to give three‐dimensional polymers. A mechanism of the polymerization being initiated with the products of the partial nitrate group decomposition was proposed. © 1994 John Wiley

ISSN:0887-624X    

DOI:10.1002/pola.1994.080320701

出版商:John Wiley&Sons, Inc.    

年代:1994

数据来源: WILEY

摘要:

AbstractThe aqueous swelling kinetics of a series of crosslinked chitosan (cr‐CS) with glutaraldehyde (GA) interpenetrating polyether hydrogels have been studied as functions of pH, theN‐deacetylation degree of chitosan, the amount of crosslinking agent, the electrolyte composition in solution, temperature, and gel composition. Based on these results, the swelling mechanism of the hydrogels was discussed. The release profiles of chlorhexidini acetas from the semi‐IPN were also investigated. © 1994 John Wiley&Son

ISSN:0887-624X    

DOI:10.1002/pola.1994.080320702

出版商:John Wiley&Sons, Inc.    

年代:1994

数据来源: WILEY

摘要:

AbstractDegradation of polyvinylchloride has been reexamined in the light of its DT‐DSC‐TG analytical behavior up to a temperature of 1000°C in an inert atmosphere. Four distinct stages of degradation have been identified. The first stage is almost eventless with no change in weight for untreated PVC samples. The second stage is almost exclusively dehydrochlorination. The third stage appears to be a structural reorganization involving such processes ascis‐transisomerization, aromatization, and crosslinking. The fourth stage appears to be a structural degradation and is associated with the evolution of hydrocarbons. The role of liberated hydrogen chloride has been better appreciated in catalyzing the above secondary reactions on the polyene residue obtained on partial or total dehydrochlorination. The effect of the particle dimension and chemical and physical pretreatments of the samples, such as low temperature dehydrochlorination by an alkali and vacuum heat treatment, respectively, on the degradation pattern has been studied. © 1994 John Wiley&So

ISSN:0887-624X    

DOI:10.1002/pola.1994.080320703

出版商:John Wiley&Sons, Inc.    

年代:1994

数据来源: WILEY

摘要:

AbstractThis study investigated the effect produced by the preparation procedure of a 2‐component lanthanide catalytic system and by the nature of organoaluminium compound on 1) the molecular characteristics of 1,4‐cis‐polybutadiene (PB), 2) the regularities of its average molecular weight (MW), and 3) molecular weight distribution (MWD). The kinetic parameters of the polymerization process were calculated. The principal regularities of variations in PB molecular characteristics with respect to the polymerization conditions, i.e., OAC and monomer concentrations and temperature, are retained with different procedures of the lanthanide catalytic system, and those present distinctive features of the catalytic complexes studied in this article. But as for differences in MW and its patterns of dependence on monomer conversion rate and OAC nature, these are due to changes in kinetic parameters of the polymerization, which occur with the use of the catalyst prepared by a different procedure. © 1994 John Wiley&Son

ISSN:0887-624X    

DOI:10.1002/pola.1994.080320704

出版商:John Wiley&Sons, Inc.    

年代:1994

数据来源: WILEY

摘要:

AbstractA vinyl monomer containing the pendant tetraphenylporphyrin (TPP) group, 4‐vinyltetraphenylporphyrin (VTPP), was synthesized. A homopolymer (PVTPP) which is insoluble in water, and three water‐soluble polymers were obtained by radical polymerization. The water‐soluble polymers are two anionic polymers (PVPTSPP and PVTPP‐StSO3) and a cationic polymer (PVTPP‐VPyM). PVPTSPP has sulfonic acid groups in a TPP group and very high charge density. PVTPP‐StSO3was obtained by copolymerization of VTPP and sodium 4‐styrenesulfonate. PVTPP‐VPyM was obtained by quarternarization of a copolymer of VTPP and 4‐vinylpyridine. Polymeric manganese(III) complexes (PMn‐VTPP, PMnVPTSPP, PMnVTPP‐StSO3, and PMnVTPP‐VPyM) were prepared from the polymers and manganese acetate. The acetate ligand in PMnVTPP can be easily substituted by another ligand such as Cl−, AcO−, OH−, and SCN−. The substitution reaction occurs in the interface between water and chloroform. The sulfonated homopolymer, PMnVPTSPP, cannot incorporate with anionic ligands because of the strong electrostatic repulsion. In the anionic copolymer, PMnVTPP‐StSO3, the ligand substitution reaction with SCN ligand needs activation energy of 53 kJ/mol. In the cationic polymer complex, PMnVTPP‐VPyM, the OH ligand can be easily substituted with the SCN ligand and the equilibrium constant of the reaction was estimated at 1.38

ISSN:0887-624X    

DOI:10.1002/pola.1994.080320705

出版商:John Wiley&Sons, Inc.    

年代:1994

数据来源: WILEY

摘要:

AbstractTriethyl‐2,3‐propanediolammonium chloride (TPC) was prepared and used for the preparation of polyester and copolyesters having quaternary ammonium groups in the side chains. The polycondensation of isophthaloyl dichloride with TPC and other dihydroxy compounds was performed by the organic phase/organic phase interfacial polycondensation method usingN,N‐dimethylacetamide/n‐heptane or trimethyl phosphate/n‐heptane as reaction media in the presence of tetramethyl ethylenediamine. Blend films were prepared from these polyesters and poly(vinyl alcohol) by casting from aqueous or aqueous NaOH solution. The electrical conductivity of the blend films is remarkably affected by the moisture content and in the order of 10−5∼ 10−8S/cm in the presence of moisture. © 1994 John

ISSN:0887-624X    

DOI:10.1002/pola.1994.080320706

出版商:John Wiley&Sons, Inc.    

年代:1994

数据来源: WILEY

摘要:

AbstractMethacrylonitrile was copolymerized withp‐methylstyrene in methyl ethyl ketone at 80°C initiated by azobisisobutyronitrile. Monomer reactivity ratios of methacrylonitrile andp‐methylstyrene were found to be 0.205 and 0.377, respectively, using the Kelen‐Tüdos method. Triad fractions and monomer sequence lengths of three copolymers were determined from13C‐NMR spectra and were found to be in good agreement with those calculated from reactivity ratios. © 1994 John Wiley

ISSN:0887-624X    

DOI:10.1002/pola.1994.080320707

出版商:John Wiley&Sons, Inc.    

年代:1994

数据来源: WILEY

摘要:

AbstractA group of new, water‐soluble poly(ether‐urethane)s, derived from poly(ethylene glycol) and the amino acidL‐lysine, provide pendent carboxylic acid groups along the polymer backbone at regular intervals. The carboxylic acid groups were utilized for the attachment of acrylate and methacrylate pendent chains (hydroxyethyl acrylate, hydroxyethyl methacrylate, aminoethyl methacrylate, and aminoethyl methacrylamide), leading to functionalized polymers. The pendent chains were attached via ester and/or amide bonds having different degrees of hydrolytic stability. The attachment reactions proceeded with high yields (up to 95%). The functionalized polymers were subsequently photopolymerized (UV irradiation) to obtain crosslinked hydrogels. Crosslinked membranes with the highest degree of mechanical strength were obtained when the crosslinking reaction was performed in dioxane with benzoin methyl ether (0.1 wt %) as the initiator. the crystallinity, thermomechanical properties, and hydrolytic stability of the crosslinked membranes were studied. All membranes were transparent and highly swellable (equilibrium water content: 64–88%). The tensile strength in the swollen state ranged from 0.15 to 1.09 MPa. Under physiological conditions (phosphate buffered water, 0.1M, pH 7.4, 37°C) the hydrolytic stability of the hydrogels varied depending on the bonds used in the attachment of the acrylate pendent chains: Hydrogels with hydroxyethyl acrylate pendent chains dissolved within 30 days, while hydrogels containing aminoethyl methacrylamide pendent chains remained unchanged throughout a 30 day period. Using high molecular weight FITC‐dextrans as model compounds, complete release from the swollen hydrogels required between 60 and 150 h. Overall, the evaluation of poly(ethylene glycol)‐lysine derived, photocrosslinked hydrogels indicated that these materials provide a range of potentially useful properties. © 1994 John Wi

ISSN:0887-624X    

DOI:10.1002/pola.1994.080320708

出版商:John Wiley&Sons, Inc.    

年代:1994

数据来源: WILEY

摘要:

AbstractA number of TiCl4catalysts supported on MgCl2which was activated by the recrystallization method using different alcohols were prepared with ethyl benzoate or dibutyl phthalate as the internal electron donor. All the catalysts were characterized by BET, x‐ray diffraction, and hydrolysis–GC analysis. Kinetics of polymerization of 1‐octene was studied with three of the above catalysts (having different internal electron donors) activated by AlEt3. The rate of polymerization increased linearly with increasing temperature, and catalyst and monomer concentrations. From the Arrhenius plot, the overall activation energies of polymerization were determined and the dependence of rate on the AlEt3concentration could be explained by the Langmuir‐Hinshelwood mechanism.13C‐NMR was used to study the effect of internal electron donors on the % isotacticity of poly(1‐octene). The catalytic activities of all the catalysts were compared in 1‐octene polymerization. © 1994 John W

ISSN:0887-624X    

DOI:10.1002/pola.1994.080320709

出版商:John Wiley&Sons, Inc.    

年代:1994

数据来源: WILEY

摘要:

AbstractThe transesterification of dimethyl naphthalate (DMN) with ethylene glycol (EG) was kinetically investigated in the presence of various catalysts at 185°C. The transesterification was assumed to obey first‐order kinetics with respect to DMN and EG, and a rate equation was derived. The rate constant of transesterification which was calculated from the quantity of methanol which distilled from the reaction vessel was used to evaluate the activity of each metal compound. The first‐order dependence on the catalyst concentration is valid below a critical concentration which was found to be dependent on the catalyst type. The order of decreasing catalytic activity of various metal ions was found to be: Pb ≥ Zn>Co>Mg>Ni ≥ Sb, but in the case of highly basic metal salts, the rate constants were found to be extremely large at the initial stage of the reaction, and then rapidly decreased with the progress of the reaction. Effects of reaction temperature were also discussed. The activation energies for zinc acetate and lead acetate were 97.84 and 108.8 kJ/mol, respectively, which were calculated from the Arrhenius equation. © 1994 John Wiley&

ISSN:0887-624X    

DOI:10.1002/pola.1994.080320710

出版商:John Wiley&Sons, Inc.    

年代:1994

数据来源: WILEY