Article (Scientific journals)
Triblock copolymer based thermoreversible gels. 2. Analysis of the sol-gel transition
Yu, Jian Ming; Dubois, Philippe; Teyssié, Philippe et al.
1996In Macromolecules, 29 (16), p. 5384-5391
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Keywords :
thermoplastic elastomer
Abstract :
[en] Syndiotactic poly(methyl methacrylate) (sPMMA)−polybutadiene (PBD)−sPMMA triblock copolymers of various chemical compositions and different molecular weights have been studied in the presence of o-xylene, which is a selective solvent for the central PBD block. Thermoreversible gels can be formed in a suitable curing temperature range (<35 °C) and at a high enough concentration (>1 wt %). The time dependence of the storage (G‘) and the loss (G‘‘) moduli has been measured in a frequency range of 0.08−1 Hz. The static and dynamic properties of the gels have been discussed on the basis of the scaling theory. At the gel point, where the loss angle (tan δc = G‘‘/G‘) is independent of frequency, typical power laws G‘(ω) G‘‘(ω) ωΔ have been observed. The scaling exponent Δ has been found equal to 0.70 ± 0.02 independently of the PBD and PMMA molecular weight, i.e., 36 000 < Mn (PBD) < 100 000 and 20 000 < Mn (PMMA) < 51 000. This exponent is also independent of the copolymer concentration and temperature in the investigated range, i.e., 2−7 wt % and 8−24 °C, respectively. This value of Δ agrees with theoretical predictions as well as with experimental values reported for some chemical gels; it is however different from the experimental values published for most physical gels. A PBD−PMMA diblock copolymer also forms a gel in o-xylene, although at higher concentration and lower temperature compared to the parent triblock copolymer. The scaling exponent Δ is then somewhat smaller, i.e., 0.61.
Research center :
Center for Education and Research on Macromolecules (CERM)
Disciplines :
Materials science & engineering
Chemistry
Author, co-author :
Yu, Jian Ming;  Université de Liège - ULiège > Department of Chemistry > Center for Education and Research on Macromolecules (CERM)
Dubois, Philippe ;  Université de Liège - ULiège > Department of Chemistry > Center for Education and Research on Macromolecules (CERM)
Teyssié, Philippe ;  Université de Liège - ULiège > Department of Chemistry > Center for Education and Research on Macromolecules (CERM)
Jérôme, Robert ;  Université de Liège - ULiège > Centre d'études et de rech. sur les macromolécules (CERM)
Blacher, Silvia ;  Université de Liège - ULiège > Département des sciences cliniques > Labo de biologie des tumeurs et du développement
Brouers, François ;  Université de Liège - ULiège > Relations académiques et scientifiques (Sciences appliquées)
L'Homme, Guy ;  Université de Liège - ULiège > Services généraux (Faculté des sciences appliquées) > Relations académiques et scientifiques (Sciences appliquées)
Language :
English
Title :
Triblock copolymer based thermoreversible gels. 2. Analysis of the sol-gel transition
Publication date :
29 July 1996
Journal title :
Macromolecules
ISSN :
0024-9297
eISSN :
1520-5835
Publisher :
Amer Chemical Soc, Washington, United States - Washington
Volume :
29
Issue :
16
Pages :
5384-5391
Peer reviewed :
Peer Reviewed verified by ORBi
Funders :
IWT - Flemish Institute for the Promotion of Science-Technological Research in Industry [BE]
BELSPO - Politique scientifique fédérale [BE]
F.R.S.-FNRS - Fonds de la Recherche Scientifique [BE]
KU Leuven - Katholieke Universiteit Leuven [BE]
Funding text :
The IWT (Flemish Institute for the Promotion of Science-Technological Research in Industry) for the financial support of a joint research program with Raychem N.V. (Kessel-Lo, Belgium) and the Katholieke Universiteit Leuven (Prof. H. Berghmans and H. Reynaers)
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