摘要:

AbstractNylon 66 [poly(hexamethylene adipamide)] and Nomex [poly(m‐phenylene isophthalamide)] were metalated by using solutions of sodium in liquid ammonia. Metalation of the Nomex polymer was also carried out by using sodium naphthalene in tetrahydrofuran. The metalated polymers were then reacted with acrylonitrile monomer to yield the corresponding anionic graft copolymers. The heterogeneous nature of these reactions is discussed in relation to the structure of the graft copolymer

ISSN:0360-6376    

DOI:10.1002/pol.1978.170160301

出版商:John Wiley&Sons, Inc.    

年代:1978

数据来源: WILEY

摘要:

AbstractRandom copolymers of ethylene, propylene, and 1,4‐hexadiene (EPDM) were carboxylated by reaction with thioglycolic acid or with maleic anhydride. Treatment of these polymers in tetrahydrofuran solution with tetrabutylammonium hydroxide generated carboxylate anions, which initiated the graft polymerization of pivalolactone. Conversion and grafting efficiencies approached 100%. Polypivalolactone chains had an estimatedDPnof 3 to 20 and the average distance between graft sites varied from 3000 to 7700 molecular weight units. On cooling from the melt, highly crystalline domains of polypivalolactone formed, which melted at 120–200°C depending onDPn. Electron microscopy and x‐ray analysis verified the presence of these domains, which serve as reinforcing tiepoints for thermally reversible network formation. The resultant thermoplastic elastomers have excellent elasticity and strength, and their compression set resistance is equivalent to that of conventionally cured and reinforced EPDM. This paper details the synthesis, morphology, and structure–property relationships of these el

ISSN:0360-6376    

DOI:10.1002/pol.1978.170160302

出版商:John Wiley&Sons, Inc.    

年代:1978

数据来源: WILEY

摘要:

AbstractThe triphenylmethyl hexafluoroarsenate‐initiated cationic polymerization of 1,2‐butylene oxide in dichloroethane between −25 and +25°C and its sodium‐initiated anionic polymerization in bulk at 20°C have been carried out. Gel permeation chromatography (GPC) molecular weight distribution curves of the reaction products are multinodal. Nuclear magnetic resonance (NMR) and infrared (IR) analyses show that the cationically prepared polymers are composed of cyclic oligomers and linear high‐molecular‐weight products, while the anionically prepared polymers contain only linear products some of which include double bonds. NMR analyses further reveal that the cationically prepared polymers consist of monomer repeat units, while the anionically prepared polymers are essentially made of side products originating from the reaction of 1,2‐butylene oxide with the sodium mirror used as the an

ISSN:0360-6376    

DOI:10.1002/pol.1978.170160303

出版商:John Wiley&Sons, Inc.    

年代:1978

数据来源: WILEY

摘要:

AbstractThe tripeptides Phe‐Gly‐Gly, β‐Ala‐Gly‐Gly, and ϵ‐Aca‐Gly‐Gly as well as the peptide derivatives δ‐isothiocyanatovaleroyl‐Gly‐Gly and ϵ‐isothiocyanatocaproyl‐Gly‐Gly were synthesized by using known methods so that the peptide nitrogen between the two glycyl residues was isotopically enriched in15N to a level of 0.8–0.9%. These monomer units were then used to produce the sequence polymers (Phe‐Gly‐Gly)n, (β‐Ala‐Gly‐Gly)n, (δ‐Ava‐Gly‐Gly)n, and (ϵ‐Aca‐Gly‐Gly)n. The 18.24 MHz15N‐NMR spectra of the oligo‐ and polypeptides were obtained by using trifluoroacetic acid as solvent, since the solutions have relatively low viscosity and exhibit a strong negative nuclear Overhauser enhancement of the15N signals. For comparison,15N‐NMR spectra of the homopolymers (Gly)n, (β‐Ala)n, (γ‐Abu)n, (δ‐Ava)n, and (ϵ‐Aca)nwere also recorded. The15N signals from the ω‐aminoacyl residues in the sequence polymers appear up to 11 ppm upfield of the signals observed for the homopolyamides. The15N signals from the two glycyl residues are separated by 3–7 ppm. Comparison with the13C‐NMR spectra of the same polymers indicates that15N‐NMR is be

ISSN:0360-6376    

DOI:10.1002/pol.1978.170160304

出版商:John Wiley&Sons, Inc.    

年代:1978

数据来源: WILEY

摘要:

AbstractPreviously reported studies on crosslinked castable poly(dimethylsiloxanes) have been extended. A series of dimethylsiloxane difumarates were copolymerized with styrene, and some of their rheological properties were determined. Investigation of these and previously prepared polymers has shown that segregation on a microscale can take place in two‐component crosslinked systems with relatively short network chains. This may occur even if one of the components is a nonpolymeric species involved in crosslinking. Microheterogeneity was observed in systems made up of prepolymer chains of a single type, when these were short enough to expose a specific structure of the crosslinking site. It seems that microheterogeneity can be expected in crosslinked polymers when the size of the crosslinking site is significant in comparison with the network chain length and when its cohesive energy density differs considerably from that of the main network chains. Additional factors affecting microphase separation include the existence of physical interactions between chemical groups, steric positioning of interacting groups during the process of crosslinking, and physical effects of the degree of crosslinking leading to local differences in the density of the syste

ISSN:0360-6376    

DOI:10.1002/pol.1978.170160305

出版商:John Wiley&Sons, Inc.    

年代:1978

数据来源: WILEY

摘要:

AbstractThe structure of polymers obtained by polymerization of methoxyallene and ethoxyallene with transition‐metal catalysts depends on the catalyst employed. Rapid polymerization at 0°C through the unsubstituted double bond occurred with π‐allylnickel halides, NiCl2/AlEt3and CoCl2/AlEt3, yielding polymers with the structureTypical Ziegler–Natta catalysts (TiCl4, VOCl3or FeCl3with AIEt3) gave polymers mainly with the structurealthough some of the structural units were probably present as well. Polymers having conjugated double bondswere prepared with PdCl2, [(π‐allyl)PdCl]2, and PdCl2(C6H5CN)2as catalysts. Palladium iodide produced polymers with all three of the above structural units present. Polymerization occurred more slowly with these palladium catalysts. A preliminary examination of the effect of variation of solvent, ligand, co‐catalyst, and temperature on the rate and structure of the polymers obtained with the palladium catalysts

ISSN:0360-6376    

DOI:10.1002/pol.1978.170160306

出版商:John Wiley&Sons, Inc.    

年代:1978

数据来源: WILEY

摘要:

AbstractA general one‐step reduction ring closure ofo‐nitroacetanalides is applied to the synthesis of 5(6)‐acetylbenzimidazole and 5(6)‐acetyl‐2‐methylbenzimidazole in good yield. The former is readily converted to the vinyl monomer by reduction and dehydration. Polymerization of this monomer with free‐radical initiation under a variety of conditions gives polymers with essentially identical nuclear magnetic resonance (NMR) spectra, implying no basic change in poly

ISSN:0360-6376    

DOI:10.1002/pol.1978.170160307

出版商:John Wiley&Sons, Inc.    

年代:1978

数据来源: WILEY

摘要:

AbstractIodine monobromide easily induces photopolymerization of methyl methacrylate (MMA) at 40°C under visible light. Initiator exponent and monomer exponent values were found to be 0.5 and 2, respectively, at low initiator concentrations, while the corresponding values at high initiator concentration conditions were zero and 3. The chain transfer constant of IBr at 40°C was found to be 13.0. Kinetic and other data indicate a radical polymerization mechanism involving complexation of monomer molecules with iodine monobromide prior to radical generation, and termination is believed to take place biomolecularly at low IBr concentrations and unimolecularly, involving reaction with the initiator, at high IBr concentrations (initiator termination

ISSN:0360-6376    

DOI:10.1002/pol.1978.170160308

出版商:John Wiley&Sons, Inc.    

年代:1978

数据来源: WILEY

摘要:

AbstractVinyl chloride was polymerized at 59–92% of saturation pressure in a water‐suspended system at 45–65°C with an emulsion poly(vinyl chloride) (PVC) latex as a seed. A water‐soluble initiator was used in various concentrations. The monomer was continuously charged as vapor from a storage vessel kept at lower temperature. Characterization included determination of molecular‐weight distribution and degree of long‐chain branching by gel permeation chromatography (GPC) and viscometry, thermal dehydrochlorination, and microscopy. The polymerization rate decreases with decreasing pressure but is reasonable even at the lowest pressure. The molecular weight decreases with decreasing pressure and increasing initiator concentration and also with increasing polymerization temperature, if the initiator concentrations are chosen to give a constant initiator radical concentration. The degree of long‐chain branching increases with increasing initiator concentration and decreasing monomer pressure but is unaffected by the polymerization temperature, if the initiator radical concentration is kept constant. The thermal stability decreases with decreasingMn, while the degree of long‐chain branching has only a minor influence. The most important factor in the system influencing the molecular parameter is the monom

ISSN:0360-6376    

DOI:10.1002/pol.1978.170160309

出版商:John Wiley&Sons, Inc.    

年代:1978

数据来源: WILEY

摘要:

AbstractRotational isomeric‐state chain‐configurational calculations have been applied to the novolac phenol–formaldehyde structure. Steric interference allows the chain to be considered with a twofold potential energy barrier model. Computations that fit the observed dipole‐moment data over a range of molecular weights indicate that the conformational angle is near ±80°, with theg±g=states on the average being 155 cal/mole below theg±g±states. The limiting dipole‐moment ratio is computed to be 1.47, compared to the experimental value of 1.48. A negative temperature coefficient agrees in sign with the experimental value, and the characteristic ratio of the end‐to‐end molecular dimensions is calculated to be 3.27, as compared to the experime

ISSN:0360-6376    

DOI:10.1002/pol.1978.170160310

出版商:John Wiley&Sons, Inc.    

年代:1978

数据来源: WILEY