Preparation and end-linking of hydroxyl-terminated polystyrene star macromolecules
✍ Scribed by Max Weißmüller; Walther Burchard
- Publisher
- John Wiley and Sons
- Year
- 1999
- Tongue
- English
- Weight
- 136 KB
- Volume
- 200
- Category
- Article
- ISSN
- 1022-1352
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✦ Synopsis
An up-scale synthesis of 3-arm hydroxyl-terminated polystyrene (PS) star polymers is reported. Subsequent end-linking of these hydroxyl-terminated star polymers with 2,4-toluene diisocyanate gave branched polymers. The extent of reacted groups was measured by UV spectroscopy. The quenched samples were characterized by static-dynamic light scattering. The experimental gel point (critical hydroxyl conversion, p OH, cr = 0.65) is shifted significantly from the theoretically predicted gel point (p OH,cr = 0.50), indicating extensive ring formation during the end-linking process. Analysis of the shrinking factors (g h , g s ) and the molar mass dependencies of the radii of gyration R g , hydrodynamic radii R h , and the second osmotic virial coefficient A 2 gave qualitative agreement with crosslinking theories. The deviations are discussed to arise from the large non-uniformity in the size distribution and from a cross-over of mean field to percolation behavior, as was previously found from the quantitative analysis of molar mass distributions.