ISSN:0449-296X    

DOI:10.1002/pol.1969.150070101

出版商:John Wiley&Sons, Inc.    

年代:1969

数据来源: WILEY

摘要:

AbstractA mixture of homopolymer and graft copolymer was obtained by adding the monomer at 0°C to the polylithiodiene solution. Styrene, methyl methacrylate, and acrylonitrile were used as the monomers. Polylithiodienes were prepared by the metalation of diene polymers, i.e., polybutadiene or polyisoprene, with the use ofn‐butyllithium in the presence of a tertiary amine (N,N,N′,N′‐tetramethylethylenediamine) inn‐heptane. The graft copolymers were separated by solvent extraction and were confirmed by turbidimetric titration and elementary analysis. Oxidation of the polybutadiene–styrene grafts revealed that the molecular weight of the side chains was the same as the molecular weight of the free polystyrene formed. The grafting efficiency and grafting percentage were studied for polybutadiene–styrene graft copolymers prepared under vari

ISSN:0449-296X    

DOI:10.1002/pol.1969.150070102

出版商:John Wiley&Sons, Inc.    

年代:1969

数据来源: WILEY

摘要:

AbstractAromatic hydrogen atoms in thermostable polymers can be surprisingly labile at relatively low temperatures and may participate extensively in degradative reactions. If hydrogen were eliminated from the polymer chain, a number of degradative pathways would be excluded. Replacement of hydrogen with other pendent groups such as fluoride or trifluoromethyl still leaves a potential “handle” to enter into unwanted reactions, therefore, all bonds not required to create the chain were eliminated. The polyimide devoid of hydrogen from pyrazinetetracarboxylic dianhydride and 2,5‐diamino‐1,3,4‐thiadiazole was synthesized. This polymer exhibits extraordinary high temperatureoxidation stability. Films of this composition support weight in air up to 592°C, and rupture at this temperature is accompanied by no charring whatever. By comparison, the corresponding polymer from pyromellitic dianhydride, with two hydrogen atoms per repeating unit begins to cha

ISSN:0449-296X    

DOI:10.1002/pol.1969.150070103

出版商:John Wiley&Sons, Inc.    

年代:1969

数据来源: WILEY

摘要:

AbstractThe sequence distributions of monomer units in a series of high‐pressure, bulk ethylene–vinyl chloride copolymers have been determined by high‐resolution NMR spectroscopy. The concentrations of EE, VV, and EV (VE) monomer pairs or diads were used with NMR‐determined compositions to calculate, in addition to the sequence distribution parameters, the reactivity ratio product for the system. Inclusion of feed data allowed the calculation of individual reactivity ratios. Well within experimental error, the reactivity ratio product (r1r2= 0.7) determined from microstructure analysis—independent of monomer feed data—was equal to that determined by the standard Fineman‐Ross technique. Terminal monomer unit effects on the copolymerization were observed. The nonrandom structures result from a copolymerization described by first‐order Markof

ISSN:0449-296X    

DOI:10.1002/pol.1969.150070104

出版商:John Wiley&Sons, Inc.    

年代:1969

数据来源: WILEY

摘要:

AbstractThe syntheses ofN,N′‐divinylureas and some related compounds are reported. Polymerization of these monomers and determination of the structures of the resulting polymers are described. Evidence is presented which supports the tendency of vinylureas to react through their tautomeric f

ISSN:0449-296X    

DOI:10.1002/pol.1969.150070105

出版商:John Wiley&Sons, Inc.    

年代:1969

数据来源: WILEY

摘要:

AbstractAmine–halogen redox systems are very efficient initiators of polymerization of a number of vinyl monomers in benzene media and are rather inefficient initiators in aqueous media. A large number of aliphatic amines and a few aromatic amines have been used. Among the halogens, chlorine and bromine are very effective. Iodine initiates with a few amines only. Endgroups incorporated are halogen and amine totalling an average of nearly one per chain in the case of polymerization in benzene media and 0.5–0.7 per chain in polymerization in aqueous media. In the light of endgroup results, a mechanism of initiation through halogen and amine radicals has been sugges

ISSN:0449-296X    

DOI:10.1002/pol.1969.150070106

出版商:John Wiley&Sons, Inc.    

年代:1969

数据来源: WILEY

摘要:

AbstractNew, bifunctional, bridgehead‐substituted triptycenes were synthesized and used to prepare a series of triptycene polymers, including polyesters, polyamides, polyurethanes, and a polyoxadiazole. Certain of these partially aliphatic polymers were thermally stable. Clear and colorless films were obtained in some instance

ISSN:0449-296X    

DOI:10.1002/pol.1969.150070107

出版商:John Wiley&Sons, Inc.    

年代:1969

数据来源: WILEY

摘要:

Abstract4‐Vinylbiphenyl–isoprene ABA block copolymers were prepared by initiating 4‐vinylbiphenyl withn‐butyllithium in benzene, adding isoprene, and coupling the resulting AB anion with phosgene. Preliminary coupling experiments with a polyisoprene anion have shown that virtually quantitative coupling could be achieved provided the phosgene was added extremely slowly. The block copolymers could be quantitatively analyzed by gel‐permeation chromatography from a knowledge of the ratio of the refractive index increments of the two homopolymers and the overall co

ISSN:0449-296X    

DOI:10.1002/pol.1969.150070108

出版商:John Wiley&Sons, Inc.    

年代:1969

数据来源: WILEY

摘要:

AbstractThe trapping of electrons and styrene cations and anions has been studied in a methylcyclohexane glass by the techniques of deferred luminescence.Radiothermoluminescencecurves consist of two peaks, at 90 and 95°K, in this matrix. The second peak increases linearly with styrene concentration up to 2 × 10−2Mwhen it reaches a constant value, whereas the first peak increases from 10−4to 10−3Mand then decreases at higher concentrations and is not discernible at concentrations above 10−2M. We propose two mechanisms which are qualitatively consistent with this behavior and are based essentially on the recombination of styrene cations with thermally detrapped electrons in the first peak and with anions in the second peak.Photothermoluminescence(i.e., thermoluminescence after photoionization with ultraviolet light) similarly consists of the 90 and 95°K peaks for a 10−3Msolution and of the 95° peak alone for a 10−dMsolution.Radiophotoluminescenceexcitation spectra at 77°K, corresponding to absorption spectra of trapped electrons and styrene anions, show that anions are the predominant negative species in 10−2molar solution, and trapped electrons in 10−3molar solution.Spectral analysisof radiothermoluminescenece shows the presence of two emission bands, one of which is identical with styrene fluorescence excited by the 254 Nm mercury line (λmax= 292, 302, 307, and 317 Nm). The other band has three fairly poorly resolved maxima at 474, 486 and 496 nm and seems to correspond to the fluorescence of C6H5ĊH‐CH3radicals

ISSN:0449-296X    

DOI:10.1002/pol.1969.150070109

出版商:John Wiley&Sons, Inc.    

年代:1969

数据来源: WILEY

摘要:

AbstractThe effect of hydrostatic pressure applied to a solution on one side of a membrane on the steady‐state concentration distribution of permeating solvent inside the membrane has been examined with a view to distinguishing between different mechanisms of permeation in reverse osmosis. The concentration gradients found experimentally in stacks of cellulose acetate films support the view that permeation takes place by diffusion in a nonporous membran

ISSN:0449-296X    

DOI:10.1002/pol.1969.150070110

出版商:John Wiley&Sons, Inc.    

年代:1969

数据来源: WILEY