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Molar mass distributions of end-linked polystyrene star macromolecules

✍ Scribed by Weissmüller, Max; Burchard, Walther

Publisher
John Wiley and Sons
Year
1997
Tongue
English
Weight
578 KB
Volume
44
Category
Article
ISSN
0959-8103

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✦ Synopsis

Polystyrene three-arm star molecules with OH tips were prepared by living anionic polymerization using an acetal-protected lithium initiator followed by coupling with 1,3,5-triallyl-oxy-2,4,6-triazine and ensuing cleavage of the acetol groups. The functionalized star molecules were end-crosslinked by toluene-2,4-diisocyanate. Randomly branched samples with various extents of crosslinking were prepared under conditions of full conversion of the isocyanate groups. The samples were fractionated analytically by SEC in on-line combination with LALLS and a viscosity detector. The mass fraction molar mass distributions could be well Ðtted by the FloryÈStockmayer distribution if the degree of crosslinking was X ¹ 6. A broad region of crossover to percolation behaviour followed and the system reached its asymptotic region for X [ 200. Power-law behaviour was already obtained at X B 70, but the exponent q exp \ 2É36 was found to lie between for the mean Ðeld approximation and q FS \ 2É5 for the percolation prediction. q perc \ 2É2

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