Zur definition eines nichtganzzahligen Kopplungsgrades für Gemische ein- und zweikettiger Polymermoleküle

✍ Scribed by Olaj, Oskar Friedrich ;Gleixner, Günther

• Publisher: Wiley (John Wiley & Sons)
• Year: 1979
• Weight: 313 KB
• Volume: 180
• Category: Article
• ISSN: 0025-116X
• DOI: 10.1002/macp.1979.021801214

✦ Synopsis

Abstract

In free radical polymerization the polymers usually represent a mixture consisting of molecules from one (degree of coupling k = 1) and two (k = 2) independently grown chains. In case the chain lengths at the moment of stabilization obey the same most probable Schulz‐Flory distribution over the total conversion interval (as e.g. at low conversions) the molecular weight distribution (m. w. d.) is a superposition of two Schulz distributions with degrees of coupling k = 1, and k = 2, respectively. Frequently, however, this m. w. d. has been described by a Schulz distribution with a non‐integer k. It is pointed out that the deviations of such a representation of the m. w. d. from the correct one may not always be negligible. Furthermore, there is no unique way to ascribe a degree of coupling k to such an m. w. d. Thus, the use of a non‐integer k should be avoided for the characterization of these polymers, especially when the interrelations between the m. w. d. and the kinetic parameters are to be discussed.