Evaluation of thiol‐ene click chemistry in functionalized polysiloxanes. Issue 8 (28th January 2013)

• Record Type: Journal Article
• Authors: Cole, Megan A.; Bowman, Christopher N.
• Is Part Of: Journal of polymer science. Volume 51:Issue 8(2013:Apr.)
• Page Start: 1749
• Page End: 1757
• Publication Date: 2013-01-28
• Subjects: 547
• DOI: 10.1002/pola.26551
• Languages: English
• ISSNs: 0887-624X

Abstract

<abstract abstract-type="main" xml:lang="en"> <title>Abstract</title> <p>Polysiloxanes are commonly used in a myriad of applications, and the "click" nature of the thiol‐ene reaction is well suited for introducing alternative functionalities or for crosslinking these ubiquitous polymers. As such, understanding of the thiol‐ene reaction in the presence of silicones is valuable and would lead to enhanced methodologies for modification and crosslinking. Here, the thiol‐ene reaction kinetics were investigated in functionalized oligosiloxanes having varying degrees of thiol functionalization (SH), π–π interactions (from diphenyls, DP), and ene types (CC). In the ene‐functionalized oligomers, π–π interactions were controlled through the use of dioctyl repeats (DO). The polymerization rate and rate‐limiting steps were determined for all systems containing an allyl‐functionalized oligomer, and rates ranging from 0.10 to 0.54 mol L<sup>−1</sup> min<sup>−1</sup> were seen. The rate‐limiting step varied with the oligomer composition; examples of rate‐limited propagation (5:3:2 CC:DP:DO/1:1 SH:DP) or chain transfer (5:3:2 CC:DP:DO/3:1 SH:DP) were found in addition to cases with similar reaction rate constants (5:2:3 CC:DP:DO/1:1 SH:DP). None of the siloxanes were found to exhibit autoacceleration despite their relatively high viscosities. Instead, the allyl‐, vinyl‐, and acrylate‐functionalized siloxanes were all found to undergo unimolecular termination based on their high α scaling values (0.98, 0.95, and 0.82, respectively) in the relation <italic>R</italic><sub>p</sub> ∝ <italic>R<sub>i</sub><sup>α</sup></italic>. © 2013 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2013</p> </abstract>