DETERMINATION OF BRANCHING IN POLYBUTADIENES, POLY(1,3-BUTADIENE-CO-1-OCTENE) AND POLY(1,3-BUTADIENE-CO-1-DODECENE)

Autor(en): MAHNER, C
KAULBACH, R
LECHNER, MD
NORDMEIER, EH
GEHRKE, K
Stichwörter: Polymer Science
Erscheinungsdatum: 1995
Herausgeber: HUTHIG & WEPF VERLAG
Journal: ANGEWANDTE MAKROMOLEKULARE CHEMIE
Volumen: 233
Startseite: 167
Seitenende: 182
Zusammenfassung: 
This paper deals with the determination of long-chain branching in polybutadienes, poly(1,3-butadiene-co-1-octene), and poly(1,3-butadiene-co-1-dodecene). These polymers were synthesized by polymerization using a neodym and aluminium-based catalyst system. Short-chain branches were introduced by incorporating olefins into the polybutadienes, leading to an improvement of their mechanical properties. The polymers were examined by static and dynamic light scattering, viscosimetry, and gel permeation chromatography. These measurements yield the g-, h-, and g(eta)-factors. The olefin incorporation was performed to increase the degree of branching. But this could not be shown clearly. It is also possible that the degree of branching increases because the polymer molar mass or the width of polymer molar mass distribution (MMD) increases. Thus, branching due to the olefin incorporation may be simulated. To analyse the influence of olefines on the degree of branching more exactly, one would need polymers having identical molar mass and MMD. Moreover, it is possible, depending on whether octene and dodecene chains are long enough, that they can be detected by means of long-chain branching (LCB) analysis. A decrease of the Lewis acid concentration in the catalyst system changes the MMD and the degree of branching. If the system contains two active centres the MMD is bimodal, whereas if there is only one active centre the MMD is unimodal. In addition, a reduction in Lewis acid concentration leads to an excess of Al(i-But)(3) in the catalyst system. Since Al(i-But)(3) is a carrier for branching reactions the degree of branching increases.
ISSN: 00033146
DOI: 10.1002/apmc.1995.052330114

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