Low molar mass polybutadiene made crosslinkable by silane moities introduced via addition of thiol to double bond: 3. Synthesis and kinetic study

• Published in: Polymer (Guilford) Vol. 39; no. 20; pp. 4955 - 4962
• Main Authors: Schapman, F., Couvercelle, J.P., Bunel, C.
• Format: Journal Article
• Language: English
• Published: Oxford Elsevier Ltd 1998; Elsevier
• Subjects: Applied sciences; Chemical modifications; Chemical reactions and properties; Exact sciences and technology; modification; Organic polymers; Physicochemistry of polymers; polybutadiene; silane; silane; polybutadiene; modification; Thiol; Butadiene derivative polymer; Organic silane; Experimental study; Free radical reaction; Chemical modification; Functionalization; Preparation; Addition reaction; Reaction mechanism; Sulfur containing polymer; Kinetics; Butadiene(hydroxy) polymer; Silicon polymer
• ISSN: 0032-3861; 1873-2291
• DOI: 10.1016/S0032-3861(97)10244-0

Low molar mass polybutadiene was made crosslinkable under moisture by the addition of mercapto propyl triethoxy silane to double bonds. The reaction was carried out at 75°C in the presence of AIBN as initiator. AIBN concentration and time showed that triethoxy silane groups were introduced quantitatively in the range of 1.05 to 7.9 per chain. A 1H n.m.r. study showed clearly that only vinylic units reacted at low modification rates. Volumetric titration of the remaining thiol was used to follow the reaction. A new mechanism is proposed here to lead to a kinetic relation, similar to the one already used by several authors, but kinetically provable. Moreover, it has been pointed out that there is probably an evolution of kinetic constants with the progress of the reaction due to, among other reasons, a local steric hindrance at the level of vinyl sequences and/or a variation in chain conformation.