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  • Polymer and Materials Science  (18)
  • Analytical Chemistry and Spectroscopy  (5)
  • elongation  (2)
  • 1980-1984  (25)
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  • 1
    Digitale Medien
    Digitale Medien
    A two-step method for the immobilization of stationary phases in GC capillary columns (1984)
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 7 (1984), S. 44-45 
    Details
    ISSN: 0935-6304
    Schlagwort(e): Gas Chromatography ; Capillary columns ; Immobilized polyethyleneglycol (Carbowax 20M) phase ; Chemistry ; Analytical Chemistry and Spectroscopy
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Zusätzliches Material: 1 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/jhrc.1240070110
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  • 2
    Digitale Medien
    Digitale Medien
    Copolymerization of β-pinene with styrene oxide and N-vinylpyrrolidone (1982)
    New York : Wiley-Blackwell
    Journal of Polymer Science: Polymer Chemistry Edition 20 (1982), S. 1279-1285 
    Details
    ISSN: 0360-6376
    Schlagwort(e): Physics ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: The copolymerization of β-pinene with styrene oxide (SO) and β-pinene with N-vinylpyrrolidone (VP) was investigated by using SnCl4 in dichloromethane diluent at low temperature. Monomer reactivity ratios were evaluated for both copolymers at -80°C; these are r1(SO) = 2.979 and r2(β-pinene) = 0.002 and r1(VP) = 0.096 and r2(β-pinene) = 0.294.
    Zusätzliches Material: 1 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/pol.1982.170200511
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  • 3
    Digitale Medien
    Digitale Medien
    Gibberellin-induced ethylene production and its effect on cowpea epicotyl elongation (1984)
    Springer
    Plant growth regulation 2 (1984), S. 209-216 
    Details
    ISSN: 1573-5087
    Schlagwort(e): Auxin ; cowpea ; elongation ; ethylene ; gibberellin ; Vigna sinensis
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Land- und Forstwirtschaft, Gartenbau, Fischereiwirtschaft, Hauswirtschaft
    Notizen: Abstract The effect of gibberellin A1 (GA1) on production of ethylene by cowpea (Vigna sinensis cv Blackeye pea no. 5) epicotyl explants and its relationship to epicotyl elongation was investigated. The explants were placed upright in water and incubated in sealed culture tubes or in large jars. GA, and IAA in ethanol solution were injected into the subapical tissues of the decapitated epicotyls. Cowpea epicotyl explants elongated after GA but not after IAA treatment, and they were very sensitive to exogenous ethylene. As little as 0.14 μ1/1 ethylene reduced significantly GA1-induced epicotyl elongation. Treatment with GA1 induced the production of ethylene which began 10 h after GA application, showed a peak at about 22 h and then declined. The yield of ethylene was proportional to the amount of GA, injected. The inhibition of epicotyl elongation in closed tubes was avoided by absorbing ethylene released with Hg(Cl04)2 , or by adding AVG to the incubation solution to inhibit ethylene production. Treatment with IAA elicited a rapid production of ethylene which ceased about 10 h after application. The effects of IAA and GA1 on ethylene production were additive.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00124769
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  • 4
    Digitale Medien
    Digitale Medien
    Physiology of gibberellin-induced elongation of epicotyl explants from Vigna sinensis (1984)
    Springer
    Plant growth regulation 2 (1984), S. 197-208 
    Details
    ISSN: 1573-5087
    Schlagwort(e): Cowpea ; elongation ; epicotyl ; gibberellins ; Vigna sinensis
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Land- und Forstwirtschaft, Gartenbau, Fischereiwirtschaft, Hauswirtschaft
    Notizen: Abstract The physiological characteristics of the response of excised cowpea (Vigna sinensis cv Blackeye pea No. 5) epicotyls to gibberellins (GAs) were studied. Epicotyl explants, retaining the petioles and a 2-cm portion of hypocotyl, were placed upright in small vials containing water. Plant growth substances were injected into the subapical tissues as ethanol solutions. Epicotyl elongation resulting from treatment with 0.5 μg of GA ranged between 5 and 13 times that of the control, depending on the GA applied. With GA1, no differences were obtained with explants prepared from 5 to 9-day-old seedlings. The increase in elongation could be detected within 6 h of treatment, and the stimulus of a single application lasted at least 4 days. Final elongation was proportional to the logarithm of the amount of GA, applied, 0.01 to lug. The response to GA treatment was limited to the upper part, the most sensitive zone being located between 2 to 4 mm below the apex of the epicotyl; this effect was entirely due to cell elongation. The induction of epicotyl elongation by GAs seems to be specific and independent of the effect of auxin. IAA had no effect on elongation and 4-chloro-phenoxyisobutyric acid (PCIB) did not affect the response to GA1
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00124768
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  • 5
    Digitale Medien
    Digitale Medien
    The use of chromatographic profiles for the identification of yeast genera (1980)
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 3 (1980), S. 528-530 
    Details
    ISSN: 0935-6304
    Schlagwort(e): Gas chromatography ; Two-phase derivatization technique ; Yeast ; Splitless injection ; Chemistry ; Analytical Chemistry and Spectroscopy
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Zusätzliches Material: 2 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/jhrc.1240031011
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  • 6
    Digitale Medien
    Digitale Medien
    Influence of tacticity on thermal degradation of PVC. V. Relation between the nature of labile conformations and the polyene distribution in the degraded polymer (1983)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 28 (1983), S. 33-43 
    Details
    ISSN: 0021-8995
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Maschinenbau , Physik
    Notizen: Four poly(vinyl chloride) (PVC) samples, 1, 2, 3, and 4, were prepared in bulk using 2,2′-azodiisobutyronitrile at 90°C and 60°C and the same initiator together with UV irradiation at 0°C and -50°C, respectively. Fractions were obtained from samples 2,3, and 4 by extracting with acetone, sample 1 being completely soluble in this solvent. The whole PVC's as well as their acetone soluble and insoluble fractions, were characterized by determining the intrinsic viscosity, the osmometric molecular weight, and the tacticity; then they were thermally degraded up to conversion of 0.3% in powder state. The values of degradation rate for both the insoluble fractions and the whole PVC's were in agreement with some prior results on the influence of syndiotactic sequences on propagation step. The soluble fractions proved to be very unstable in comparison with the insoluble, which, despite the lower molecular weight of the former, seems to obey their higher content of isotactic conformations. The fine polyene distribution in the degraded polymers was carried out by UV-visible spectroscopy. The results reveal the occurrence of two different polyene distributions, and allow for the peculiar one of the soluble fractions to be related to polyenes consisting of two sequences of trans conjugated double bonds separated by a single cis double bond. The results clearly shows that there are two mechanisms for initiation of the PVC degradation, depending on whether it occurs by random unstable structures or by the normal GTTG isotactic or TTTG heterotactic triads. Moreover, these two initiation processes are proved to give rise to different types of polyenes, which accounts for the occurrence of two unlike mechanisms of propagation.
    Zusätzliches Material: 6 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/app.1983.070280104
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  • 7
    Digitale Medien
    Digitale Medien
    Influence of tacticity on the thermal degradation of PVC. VI. New advances in the degradation process through the behavior of modified PVC samples (1984)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 29 (1984), S. 1735-1741 
    Details
    ISSN: 0021-8995
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Maschinenbau , Physik
    Notizen: Three PVC samples having different tacticities, as well as the products resulting from their reaction with sodium thiophenate, which was previously found to occur selectively by some definite isotactic conformations, were degraded at 180°C in solid state up to 0.3%. In agreement with prior works, the stability of the substituted polymers was shown to be higher as the substitution extent increased up to a definite value, which depends on the overall isotactic content of the starting materials. On the other hand, the found changes in polyene distribution for the degraded samples with the substitution extent, as followed by UV-visible spectroscopy, demonstrate that the specific bands at 393, 416, and 437 nm, which are known to be characteristic for the most unstable PVCs, arise from the lability of some chlorine atoms located at GTTG′ (or TTTG) conformations, as prior results suggested. On the basis of the so-obtained correlation between the content of some isotactic triads (especially the GTTG′) and both the thermal instability and the formation of the above-indicated specific polyenes, new advances in the degradation mechanism are proposed.
    Zusätzliches Material: 3 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/app.1984.070290526
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  • 8
    Digitale Medien
    Digitale Medien
    Anionic and radical polymerization of p-triphenyl- and p-tributylgermyl-styrenes (1983)
    New York : Wiley-Blackwell
    Die Makromolekulare Chemie 184 (1983), S. 961-967 
    Details
    ISSN: 0025-116X
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Physik
    Notizen: Anionic polymerization of p-triphenylgermylstyrene (1a) and p-tributylgermylstyrene (1b) were investigated under high vacuum conditions (≈10-6 mbar). Both 1a and 1b were readily polymerized with sodium naphthalide, potassium naphthalide, or α-methylstyrylsodium oligomers to form “living polymers”. The addition of α-methylstyrene to these living systems gave the triblock copolymer, poly(α-methylstyrene-b-p-triphenylgermylstyrene-b-α-methylstyrene). Both monomers were also polymerized radically with AIBN as initiator. Some physical properties of the resulting polymers were examined.
    Zusätzliches Material: 2 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/macp.1983.021840508
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  • 9
    Digitale Medien
    Digitale Medien
    Polyene sequence distribution in modified poly(vinyl chloride) after thermal degradation (1984)
    New York : Wiley-Blackwell
    Die Makromolekulare Chemie 185 (1984), S. 1277-1284 
    Details
    ISSN: 0025-116X
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Physik
    Notizen: The products resulting from the reaction of PVC with sodium benzenethiolate were degraded to 0,3% at 180°C in the solid state and at 160°C in solution in trichlorobenzene. The polyene distribution of the polymers after degradation was studied by both UV-visible and resonance Raman spectroscopies, as a function of the degree of substitution. The results show that there are two types of behaviour: that of the PVC sample prior to the substitution reaction together with the samples modified up to a definite degree of substitution which depends on the starting isotactic content, and that of samples with higher degrees of substitution. The former group exhibits not only a steady improvement in thermal stability but also a preferential formation of polyenes of 7 - 9 double bonds whose concentration decreases with increasing degree of substitution. Conversely, for the second group of samples the thermal stability decreases with the degree of substitution and no specific absorption bands are observed. On the basis of earlier work on the selective substitution of the isotactic GTTG and heterotactic TTTG triads during the first stage of the reaction, the present results show that the bands at 393, 416, and 437 nm are related to specific polyenes which result from initiation by the above quoted conformations in PVC, a conclusion for which confirmatory evidence was obtained by resonance Raman spectroscopic examination of the samples. There is, therefore, clear evidence for the occurrence of two distinct degradation mechanisms, one involving initiation by the unstable triad conformations and the other via random initiation at stable and normal structures. To this may be added the initiation by defect structures, which have been extensively documented in the literature.
    Zusätzliches Material: 5 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/macp.1984.021850701
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  • 10
    Digitale Medien
    Digitale Medien
    The cationic polymerization of 2-alkenylfurans, 2Part 1: cf.5. A side reaction leading to polyunsaturated products (1982)
    New York : Wiley-Blackwell
    Die Makromolekulare Chemie 183 (1982), S. 2399-2413 
    Details
    ISSN: 0025-116X
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Physik
    Notizen: A spectroscopic and conductimetric study of the cationic polymerization of 2-vinylfuran (1) and 2-methyl-5-venylfuran (2) showed the existence of an important side reaction originating from a hydride-ion shift from an unsaturated polymer molecule to an active species. The resulting allylic carbocation, in equilibrium with a doubly unsaturated polymer molecule, can react further and the repetition of the mechanism on progressively more conjugated species leads to the formation of a series of highly charge-delocalized carbenium ions absorbing throughout the visible region of the spectrum (and giving high electrical conductivity) and of neutral polyconjugated polymer molecules. Since the hydride-ion abstraction occurs from the tertiary carbon atom of the vinylic chain, vinylidene polymers of monomers such as 2-isopropenylfuran (3) and 2-isopropenyl-5-methylfuran (4) are not susceptible to it. Indeed, their cationic polymerization proceeds without colour formation and conductivity increase.
    Zusätzliches Material: 7 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/macp.1982.021831010
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