摘要:

AbstractThe anionic polymerization of 1.3‐cyclohexadiene (1.3‐CHD) was investigated in temperatures that ranged from 25 to −77°C. Initiation by lithium naphthalene (N−·,Li+) in tetrahydrofuran at −20°C yields polymers with fairly narrow molecular weight distribution. The M̄wof these polymers so prepared is ca. 20,000. Polymerization of 1.3‐CHD conducted at room temperature is accompanied by the dehydrogenation and disproportionation of the monomer, especially when N−·,K+acts as initiator. Oligomers are formed when hexamethylphosphoramide is used as a solvent. The mechanism of the initiation of the polymerization of 1.3‐CHD by N−·,Li+was elucidated and the rate constants at −20°C in tetrahydrofuran of the elementary reactions were determined. It was established that the dianions formed by disproportionation of N−·,Li+act as effective initiators for 1.3‐CHD. The adducts formed constitute the cyclohexanyl and naphthyl carbanionic groups. The former carbanions (λmax∼ 275 nm) propagate the polymerization. The initially formed dimeric adducts are stabilized by the separation of the carbanionic end groups by the additional monomer units. Chain transfer to the monomer limits the growth of the polymers. The isomerization of the cyclohexadienyl anions, formed as result of chain transfer, may be followed by the elimination of lithium hydride. The latter reaction represents a termination step. Addition of 1.4‐CHD to the reaction mixture enhances th

ISSN:0360-6376    

DOI:10.1002/pol.1982.170200401

出版商:John Wiley&Sons, Inc.    

年代:1982

数据来源: WILEY

摘要:

AbstractCalcium cation complexing by polymetaphosphate anions was studied by direct potentiometric measurements with a calcium‐ion‐sensitive electrode. The moderately stable neutral chelate (Ca2P4O 120)nis formed in (CaP2O6)nsolutions according to the equilibrialogK12values for complexing with polyanions ofMav≃ 1200 and 2500 (at C P 2O 6= 0.0003M) were 5.86 and 6.26, respectively; theK12values then decreased with increasing polyanion concentration and were reduced by addition of equivalent sodium chloride. The very stable chelate anion (CaP4O 122−)nis then formed in (Na2CaP4O12)nsolutions according to the equilibriumlogK14values for complexing with polyanions ofMav≃ 1200 and 2500 (at C P 4O 12= 0.0003M) were 7.48 and 8.08, respectively; theseK14values also decreased with polyanion concentration. A less stable complex anion (CaP6O 184−)nis formed in more concentrated

ISSN:0360-6376    

DOI:10.1002/pol.1982.170200402

出版商:John Wiley&Sons, Inc.    

年代:1982

数据来源: WILEY

摘要:

AbstractStudies of the effect of aqueous Br2solution on the fine structure of cellulose have shown that the accessibility of the cellulose is a complex function of the duration of treatment. Following immersion of rayon‐cellulose in the Br2solution, its accessibility is observed to increase until a peak is reached, after which the accessibility decreases with time. For higher temperatures and greater concentrations of Br2, a sharper peak and faster rates of increase and decrease of accessibility are obtained. In order to explain this behavior, a mathematical model of the kinetics is postulated involving two opposing first‐order processes occurring simultaneously. One process describes the decrystallization of crystalline regions within the cellulose by opening intermediate linkages due to Van‐der‐Waals forces involved. The second process relates to the crystallization of the less‐ordered regions. The rate constants for these processes are determined by fitting experimental curves to the postulated analytical expression with the aid of a digital computer program. Experiments carried out on high‐modulus rayon showed that for this type of cellulose, the effect described above was very pronounced. From the calculated rate constants, the activation energies of the crystallization and decrystallization reactions were determined. The plots of the rate constants versus 1/Tshowed that a break occurs at 25°C, corresponding to a second‐order transition point of cellulose. The energies of activation of the crystallization process are in the range of 7–9 and 10–13 kcal/mol in the temperature ranges 10–25 and 25–40°C, respectively. The activation energies of the decrystallization process are 13 and 18–24 kcal/mol in

ISSN:0360-6376    

DOI:10.1002/pol.1982.170200403

出版商:John Wiley&Sons, Inc.    

年代:1982

数据来源: WILEY

摘要:

AbstractThe grafting of styrene and acrylamide, from both their binary and unitary systems, on cellulose acetate film was studied by means of the cobalt‐60 postirradiation grafting technique. The extent of grafting was found to be dependent on preirradiation dose, reaction time, and temperature, and the optimum conditions were evaluated. The effect of solvents, e.g., water, methanol, ethanol, isopropanol, andt‐butanol were studied. The composition of the binary mixture as well as the nature of the alcohol used as the solvent were found to have a strong influence in modifying the course of grafting. Each component of the binary monomer mixture was found to sensitize the grafting of the other, when the former is present in relatively large concentration. The observed results are discussed in detail in terms of relative molecular reactivity and reactivity rat

ISSN:0360-6376    

DOI:10.1002/pol.1982.170200404

出版商:John Wiley&Sons, Inc.    

年代:1982

数据来源: WILEY

摘要:

AbstractA new method for the preparation of exactly alternating silarylene–siloxane polymers by the low temperature step‐growth condensation polymerization reaction of arylenedisilanols and bisurei‐dosilanes in chlorobenzene was investigated. To obtain high molecular weight products1H NMR spectroscopy and gel permeation chromatography were used to monitor the polymerization reaction. By using these procedures 12 different polymers were prepared from 1,4‐bis(dimethylhydroxysilyl)‐benzene, 4,4′‐bis(dimethylhydroxysilyl)phenyl ether, bis(1,1‐tetramethylene‐3‐phenylureido)‐dimethylsilane, and bis(1,1‐tetramethylene‐3‐phenylureido)‐methylvinylsilane monomers. The polymers were obtained in high yields, pu

ISSN:0360-6376    

DOI:10.1002/pol.1982.170200405

出版商:John Wiley&Sons, Inc.    

年代:1982

数据来源: WILEY

摘要:

AbstractTo study the possibility of obtaining aliphatic‐aromatic polycarbonates the reactions of CO2, dipotassium 4,4′‐isopropylidenediphenolate, and different α,ω‐dihalo compounds were studied in polar aprotic solvents in the presence of various catalysts. It was shown that in addition to the crown ethers already in use as catalysts in this type of polycondensation reaction cryptates and polyglyme exhibit similar catalytic activity. The influence of temperature, CO2pressure, solvent, and structure of the α,ω‐dihalo compound on the yield of the polymer formed was established. A relationship between the type and amount of catalyst used, especially crown ether, on the reaction yield was revealed, and some physicochemical properties of the polymers obtained were determined. Studies of the model reaction between CO2, potassium phenolate, and different α,ω‐dihalo compounds under conditions analogous to those of the studied reaction were carried out. On the basis of the results obtained attempts were made to explain the r

ISSN:0360-6376    

DOI:10.1002/pol.1982.170200406

出版商:John Wiley&Sons, Inc.    

年代:1982

数据来源: WILEY

摘要:

AbstractAlternating copolymers of α‐methylstyrene (α‐MeSt) and maleic anhydride (MAn) were prepared by free‐radical‐initiated polymerization in bulk, benzene, or butanone as solvents. By applying the generalized model described by Shirota and co‐workers, the reactivity ratiosk1c/k12andk2c/k21were calculated from the change of copolymerization rate with monomer feed at constant total monomer concentration. From the equationRp=Rp(f) +Rp(CT) were calculatedRp(f) andRp(CT), and it was found that in benzene the reaction proceeds predominantly by the addition of CT‐complex monomers, while in butanone, cross propagation of free monomers predominates. Termination occurs predominantly by homotermination of α‐MeSt macro free radicals,kt22, although the cross terminationkt21i

ISSN:0360-6376    

DOI:10.1002/pol.1982.170200407

出版商:John Wiley&Sons, Inc.    

年代:1982

数据来源: WILEY

摘要:

AbstractFour new substituted styrene derivatives carrying lactam rings (2‐pyrrolidone or 2‐piperidone) in para position have been synthesized, namely 4‐(2‐oxo‐3‐methylene‐pyrrolidinyl)styrene, 4‐(2‐oxo‐3‐methylene‐piperidinyl)styrene, 4‐(p‐styryl)‐2‐pyrrolidone, and 4‐(p‐styryl)‐2‐piperidone. Their homopolymerization and copolymerization with styrene, methyl methacrylate, and acrylic acid have been considered. By ring opening of the side lactam groups, the homopolymers are transformed into the c

ISSN:0360-6376    

DOI:10.1002/pol.1982.170200408

出版商:John Wiley&Sons, Inc.    

年代:1982

数据来源: WILEY

摘要:

AbstractThe synthesis of amylose–polyester block copolymers is described. 2,3,6‐Tri‐0‐allyl amylose was synthesized by amylose alkoxide and allyl bromide and hydrolyzed by hydronium ions to give an hydroxyl‐terminated allyl amylose oligomer (HTAA). The allyl groups were isomerized witht‐BuoK to yield the prop‐1‐enyl isomer (HTPA). The HTPA was capped with a diisocyanate. The HTPA prepolymer was reacted with hydroxy‐terminated poly(ethylene‐co‐propylene adipate) and poly‐(ethylene terephthalate) to form block terpolymers. Block terpolymer formation was demonstrated by intrinsic viscosity increases, gel permeation chromatographic results, and infrared (IR) and PMR spectroscopy. The products were depropenylated by HgCl2to yield amylose block terpolymers. These polymers were readil

ISSN:0360-6376    

DOI:10.1002/pol.1982.170200409

出版商:John Wiley&Sons, Inc.    

年代:1982

数据来源: WILEY

摘要:

AbstractThe characteristics of the photoinduced electron transfer reaction from polystyrene pendant tris(2,2′‐bipyridyl)ruthenium (II) complex [Ru(bpy) 32+] to methylviologen (MV2+) were studied. The rate constantk1from the excited state of the complex, Ru(bpy) 32+*, to MV2+were determined for both the polymeric and monomeric complexes from the lifetime τ of Ru(bpy) 32+*and the quenching rate of Ru(bpy) 32+*by MV2+. The polymer pendant Ru(bpy) 32+*showed three kinds of τ components ranging from 7 to 474 ns, in contrast to the monomeric complex, which showed one component of 350 ns. Thek1values for both complexes were almost the same, on the order of 108L/mol s. The photoinduced electron transfer from solid‐phase Ru(bpy) 32+to liquid‐phase MV2+was realized by utilizing the polymer complex, and the solid–liquid interphase react

ISSN:0360-6376    

DOI:10.1002/pol.1982.170200410

出版商:John Wiley&Sons, Inc.    

年代:1982

数据来源: WILEY