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Comparison of irreversible and reversible cluster formation
Author(s) -
Weißmüller Max,
Merkle Gerhard,
Burchard Walther
Publication year - 1995
Publication title -
macromolecular symposia
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.257
H-Index - 76
eISSN - 1521-3900
pISSN - 1022-1360
DOI - 10.1002/masy.19950930136
Subject(s) - polymer , adipate , gel point , covalent bond , polymer chemistry , ring (chemistry) , cluster (spacecraft) , dynamic light scattering , materials science , chemistry , percolation (cognitive psychology) , organic chemistry , nanotechnology , computer science , nanoparticle , programming language , neuroscience , biology
Covalent and reversible cluster molecules were synthesized by an A 3 B 2 type gelation. Crosslinking of three‐arm hydroxyl‐terminated star polymers with 2,4‐toluenediisocyanate gave branched polymers, while the reversible analogue was made by crosslinking of tertiary amine‐terminated star polymers with bis(4‐hydroxy‐3,5‐dinitrophenyl) adipate. Gelation process was followed by static and dynamic light scattering. The extent of reacted groups was measured with UV spectroscopy. Growth of the covalent clusters could be described in terms of percolation scaling laws. The experimental gel point (P OH, cr = 0.70) was shifted significantly from the theoretical predicted gel point (P OH, cr = 0.50), indicating extensive ring formation during the gelation. The reversible endlinking reaction gave no macroscopic gelation, though increase of the cluster dimensions was observed. Ring formation proved to be an important side reaction in both cases; however, the ring formation ability seems to change in a different manner during the course of a gelation.