摘要:

AbstractThe presence of the sterically hindered Lewis acid, trimesityl boron, during the anionic polymerisation of isoprene is shown to affect the structure of the resulting polymer only marginally. This behaviour contrasts with its effect when the monomer is butadiene. The principal change is an increase in 1,4‐content at the expense of 1,2‐structure, with the proportion of 3,4‐structure remaining unaffected. These results are explained in terms of the isomeric forms of the propagating

ISSN:0007-1641    

DOI:10.1002/pi.4980160102

出版商:John Wiley&Sons, Ltd    

年代:1984

数据来源: WILEY

摘要:

AbstractTraditional methods for the quantitation ofO‐acetate ester and pyruvic acid acetal in xanthan gums require hydrolysis procedures followed by determination of acetic acid and pyruvic acid separately either by colorimetric, enzymic or chromatographic assays. Some of these assays are time‐consuming and involve many solvent extractions, and during the course of these procedures the xanthan sample is destroyed by hydrolysis. The methyl protons of bothO‐acetate ester and pyruvic acid acetal can be detected by1H n.m.r. spectroscopy, and this paper describes a method for the quantitative determination of these groups on intact polymeric xanthan using an internal integration standard dissolved within the sample. The method is non‐destructive, can be easily performed on a 60MHz spectrometer equipped with Fourier Transformation and variable temperature control, and simultaneously quantitates bothO‐acetate ester and pyruvic acid acetal with improved

ISSN:0007-1641    

DOI:10.1002/pi.4980160103

出版商:John Wiley&Sons, Ltd    

年代:1984

数据来源: WILEY

摘要:

AbstractThe supermolecular structure of crystallised molecular weight fractions of poly(hexa‐methylene oxide), covering the molecular weight range (M) 4.5. × 103to 8. 5 × 104, was studied by polarised light microscopy and small angle light scattering. Different forms were observed as a function of molecular weight and crystallisation temperatures. Perfect spherulites are formed after rapid crystallisation, and these forms deteriorate as both the molecular weight and crystallisation temperature increase. The morphology in the isothermal crystallisation region corresponds to an intermediate state which represents a transition from spherulites to hedri

ISSN:0007-1641    

DOI:10.1002/pi.4980160104

出版商:John Wiley&Sons, Ltd    

年代:1984

数据来源: WILEY

摘要:

AbstractPositron lifetime measurements are reported over a temperature range from 290 to 380K on cellulose and certain of its derivatives. The lifetime spectra were resolved into three components each attributed to a different mode of positron annihilation in the polymer. The longest lifetime component is associated with the decay ofortho‐positronium and is a function of the average cavity distribution in the sample. It is observed that significant differences exist in the lifetimes of positrons in cellulose and its derivatives which can be interpreted as evidence for changes in the free volume distribution in these materials. Comparison of positron decay in samples of cellulose acetate prepared at both room temperature and elevated temperature indicate that the phenomena of gelation in this material is accompanied by a reduction of free volume. The correlation of such observations with the dynamic properties of these polymers is discusse

ISSN:0007-1641    

DOI:10.1002/pi.4980160105

出版商:John Wiley&Sons, Ltd    

年代:1984

数据来源: WILEY

摘要:

AbstractThe13C n.m.r. spectra of the title polymers have been completely assigned for a comprehensive range ofciscontents (σc= 0–1) and head‐tail bias (HT/(HH + TT) = 1 −∞). In the unsaturated polymers (II),cisHH dyads are never found, so that all‐cispolymers are also all‐Ht, butcisTT dyads are formed incis‐transpolymers, equal to the difference betweentransHH andtransTT. The olefinic region consists of seven triplets; two each fromcisHT andtransHT, and one each fromcisTT,transTT andtransHH. In the case oftranseach triplet consists of a main centre peak due totttandctcsequences and two wing peaks due tottcandcttsequences, as defined in the text. The upfield peaks also showcc/ctortt/tcsplittings as well as HH/HT or TT/TH splittings in most cases. In the saturated polymers C6is sensitive tom/rring dyad sequences. A corrected assignment is given for the hydrogenated polymer

ISSN:0007-1641    

DOI:10.1002/pi.4980160106

出版商:John Wiley&Sons, Ltd    

年代:1984

数据来源: WILEY

摘要:

AbstractCalcium carbonate fillers react with hydrogen chloride liberated during pyrolysis of PVC to an extent depending on their particle sizes and concentrations. The effects of these and other fillers on the critical oxygen index is more complex and depends on a number of factors additional to the extent of hydrogen chloride retention, of which char formation in particular is not readily assessed numerically. Differential thermal analyses suggest that the reaction of hydrogen chloride with calcium carbonate or calcium oxide fillers proceeds rapidly upon liberation. Hydrogen chloride added to the gas stream raises the critical oxygen index to a considerably greater extent than do carbon dioxide or nitrogen. It is concluded that the exotherm due to reaction between calcium carbonate fillers and pyrolysis hydrogen chloride contributes only slightly to flammability, and that the involvement of hydrogen chloride in reducing flammability is chemical rather than physical.

ISSN:0007-1641    

DOI:10.1002/pi.4980160107

出版商:John Wiley&Sons, Ltd    

年代:1984

数据来源: WILEY

摘要:

AbstractThe syntheses of a number of acrylate and methacrylate based amphiphiles are described. One group consists essentially of quaternary ammonium salts and the other of potassium carboxylates. Two non‐ionic species based on oligoethylene oxides are also described. The critical micelle concentration of each has been determined from conductance and dye absorption data, and the values compare satisfactorily with literature data on similar non‐polymerisable molecules. The compounds readily oligomerised in bulk, and in the micellar state the dye absorption data also indicated oligomerisation initiated by a free radical sou

ISSN:0007-1641    

DOI:10.1002/pi.4980160108

出版商:John Wiley&Sons, Ltd    

年代:1984

数据来源: WILEY

ISSN:0007-1641    

DOI:10.1002/pi.4980160109

出版商:John Wiley&Sons, Ltd    

年代:1984

数据来源: WILEY

ISSN:0007-1641    

DOI:10.1002/pi.4980160111

出版商:John Wiley&Sons, Ltd    

年代:1984

数据来源: WILEY

ISSN:0007-1641    

DOI:10.1002/pi.4980160114

出版商:John Wiley&Sons, Ltd    

年代:1984

数据来源: WILEY