摘要:

AbstractLithium diisopropylamide, in the presence of diisopropylamine, initiates the polymerization of isoprene to form oligomers having one diisopropylamino end group. These oligomers1 a, formed in the early stages of the reaction, are considered to carry out the chain termination (or metalation) reaction. Results of mechanistic studies of the chain termination (or metalation) reaction in isoprene oligomerization in the presence of various types of allylamine homologues, as low molecular weight model compounds for1 aare presented. The presence of acis‐methyl group with respect to the amino methylene group was found to be essential for the low molecular weight model compounds to exhibit large reactivity in the chain transfer reaction. Oligomers with amino end groups neither have to possess acis‐methyl group nor an allylamine structure to be active. A number of results showed that the driving force for the metalation reaction of oligomers with amino end groups is different in nature from that of the lowmolecular‐weight allylamine homologues. A possible mechanism for the metalation reaction of these oligomers is discussed in terms of a hydrophobic interaction with the growing

ISSN:0025-116X    

DOI:10.1002/macp.1985.021860701

出版商:Hüthig&Wepf Verlag    

年代:1985

数据来源: WILEY

摘要:

AbstractThe reaction ofsec‐butyllithium with 1,1‐bis(4‐isopropenylphenyl)‐1‐phenyltridecane (3) yields carbanionic species which are soluble in a non‐polar solvent. The long hydrocarbon “tail” of the molecule and the tendency of the organolithium compounds to associate may be the reason for the high solubility, possibly due to micel‐formation. In the absence of any sidereaction, the addition reaction should lead to a difunctional organolithium compound. However, UV spectrometric measurements and characterization by size exclusion chromatography of the species obtained after protonation of the anionic sites, show that oligomerization accompanies the di‐addition reaction with formation of principally dimeric and a small fraction of trimeric molecules. This implies the existence of di‐, tri‐ and tetracarbanionic species in the

ISSN:0025-116X    

DOI:10.1002/macp.1985.021860702

出版商:Hüthig&Wepf Verlag    

年代:1985

数据来源: WILEY

摘要:

AbstractHydrogen peroxide, thermally cleaved into hydroxyl radicals, was used as initiator of butadiene‐vinylferrocene copolymerization. The influence of different parameters like temperature, pressure, proportion of hydrogen peroxyde and addition of a solvent with weak transfer capability was studie

ISSN:0025-116X    

DOI:10.1002/macp.1985.021860703

出版商:Hüthig&Wepf Verlag    

年代:1985

数据来源: WILEY

摘要:

AbstractChlorinated and brominated butyl rubbers (CIIR and BIIR) were each compounded with 3‐aminopropyltriethoxysilane (APS) and dibutyltin dilaurate on a two‐roll mill, and were pressed at 150°C for 20 min. The resulting sheets were cured by soaking them in water. The progress of the moisture‐cure was followed by determining the network‐chain density (νs). The rate of the moisture‐cure was found to depend on the soaking temperature. The resulting maximumvswas, however, independent of the soaking temperature. The kinetic study of the reactions of CIIR and BIIR with APS in toluene revealed that the maximum replacement of the halogen atoms with APS (m) was ≈ 40% in CIIR and ≈ 70% in BIIR. Thus, the apparent cross‐linking efficiency of the moisture‐cure was e

ISSN:0025-116X    

DOI:10.1002/macp.1985.021860704

出版商:Hüthig&Wepf Verlag    

年代:1985

数据来源: WILEY

摘要:

Abstract5,11,17,23‐Tetra‐tert‐butyl‐25,26,27,28‐tetrahydroxy‐2‐oxocalix[4]arene (4a), 5,11,17,23,29,35‐hexa‐tert‐butyl‐37,38,39,40,41,42‐hexahydroxy‐2‐oxocalix[6]arene (4b), and octa‐tert‐butyl‐octahydroxy‐trioxocalix[8]arene (4c) were synthesized via 4‐tert‐butylcalix[4]‐, [6]‐ and [8]arenes from 4‐tert‐butylphenol as a starting material. 5,5′‐Di‐tert‐butyl‐2,2′‐dihydroxybenzophenone (7) was synthesized via 5,5′‐di‐tert‐butyl‐2,2′‐dimethoxybenzophenone (6) from bis(5‐tert‐butyl‐2‐methoxyphenyl)methane (5). 1,4‐Dioxane solutions of4a,4b,4c,6, and7were irradiated. The photostabilities of4band4cwere found to be better than those of4a,6, and7. A poly(vinyl chloride)

ISSN:0025-116X    

DOI:10.1002/macp.1985.021860705

出版商:Hüthig&Wepf Verlag    

年代:1985

数据来源: WILEY

摘要:

AbstractCore‐shell latex of poly(methyl methacrylate‐co‐acrylic acid) with surface containing functional carboxylic acids, was prepared by seed polymerization and characterized. α‐Chymotrypsin was immobilized on the surface of these latex particles by chemical bonding in aqueous medium, using a water soluble carbodiimide as coupling agent. The latex particles size before and after the attachment of the enzyme was determined using photon correlation spectroscopy. The activities of free and immobilized enzyme were studied as a function of temperature, reusability and pH. The activity for the immobilized enzyme was highest at a pH slightly higher than the optimum pH of free enzyme, which could be explained due to the polyanionic matrix as well as due to the variation in the size of latex at higher pH, which provided more mobility to the enzyme, and thus a higher

ISSN:0025-116X    

DOI:10.1002/macp.1985.021860706

出版商:Hüthig&Wepf Verlag    

年代:1985

数据来源: WILEY

摘要:

AbstractThe interface reaction of a THF solution of a vinylidene chloride copolymer with an aqueous alkaline solution in the presence of a quaternary ammonium halide as a phase transfer catalyst affords a dehydrochlorinated polymer film with conjugated polyene structure. The degree of the reaction is dependent on the catalyst structure, and tetrabutylammonium bromide is the best among those used. KOH was found to be more effective than NaOH. The effects of the base and polymer concentration and of the nature of the solvent were also studied. The results are discussed in terms of the change of the rate of formation of ammonium hydroxide at the interface and of its diffusion in the organic phase. The doping of the obtained films with iodine vapor increases the electric conductivity up to 7 · 10−4S · c

ISSN:0025-116X    

DOI:10.1002/macp.1985.021860707

出版商:Hüthig&Wepf Verlag    

年代:1985

数据来源: WILEY

摘要:

AbstractThe initial stages of phase separation in the formation of semi‐interpenetrating polymer networks (semi‐IPN's) based on copolymer from styrene with divinylbenzene (DVB)/poly(butyl methacrylate) (PBMA) were studied using an optical laser diffractometer. It was found that phase separation obeys the mechanism of spinodal decomposition. The peculiarity of phase separation in the system studied is due to the existence of a two‐stage process. Each stage exhibits different interdiffusion coefficients, sizes of microheterogeneity areas and activation ene

ISSN:0025-116X    

DOI:10.1002/macp.1985.021860708

出版商:Hüthig&Wepf Verlag    

年代:1985

数据来源: WILEY

摘要:

AbstractThe oxidation of a polypropylene (PP) film was studied with respect to activation for volume grafting. To attain the content of peroxides adequate for an intended graft level, the five oxidation variables: temperature, time, oxygen pressure and concentrations of initiator and surfactant were optimized. For a statistical analysis, the experiments were planned according to a hyper‐graeco‐latin square. The relation between the reaction variables and the ratio of peroxides and hydroperoxides within the polymer was determined. The distribution of the oxygencontaining products inside the peroxidized PP film was monitored by transmission and attenuated total reflection in the infrared region. The optimum variables enable an oxidation of PP to a desired degree, with peroxide groups uniformly distributed throughout the film, and at minor disturbance of the mechanical characteristics of the mater

ISSN:0025-116X    

DOI:10.1002/macp.1985.021860709

出版商:Hüthig&Wepf Verlag    

年代:1985

数据来源: WILEY

摘要:

AbstractGrafting of acrylic acid onto a pre‐activated polypropylene film was investigated, varying the concentrations of monomer and Fe2+‐ions, the polymerization time and temperature. Experiments were planned according to a scheme of a latin square, and statistical analyses were performed for the optimization of the grafting variables. The concentration of ferrous ions was found to be the most significant variable for the graft level. At low concentration, ferrous ions act as activator of grafting but no grafting takes place at relatively high concentrations. The distribution of grafted poly(acrylic acid) within a PP film was examined by microphotometry of the coloured slides of the film. The grafted layer of PP reaches the center only at about 30% of grafted poly(acrylic acid) and up to 70% the distribution of grafted poly(acrylic acid) is still non‐uniform with a decreasing amount of the polyacid from the surface to the center. The film samples containing 30% of grafted poly(acrylic acid) already show conductivity in alkaline media and are interesting ion conducting mate

ISSN:0025-116X    

DOI:10.1002/macp.1985.021860710

出版商:Hüthig&Wepf Verlag    

年代:1985

数据来源: WILEY