Influence of Type of Initiation on Thiol-Ene “Click” Chemistry

Influence of Type of Initiation on Thiol-Ene “Click” Chemistry, M. Uygun, M. A. Tasdelen, Y. Yagci, Macromol. Chem. Phys., 211, 103-110 (2010) DOI: 10.1002/macp.200900442


Thermally and photochemically initiated thiol–ene click reactions using thiol- and allyl- end
functionalized linear polystyrenes with various enes (allyl bromide, methyl acrylate, and
methyl methacrylate) and thiol (3-mercaptopropionic acid) have been investigated. Allyl- and
thiol-end-capped polystyrenes with controlled molecular weight and low polydispersity were
prepared by atom transfer radical polymerization (ATRP) of styrene using functional initiator
and end group modification approaches, respectively. Thiol–ene reactions can be initiated by
both cleavage type photoinitiators such as (2,4,6-trimethylbenzoyl)diphenylphosphine oxide
(TMDPO) and 2,2-dimethoxy-2-phenyl acetophenone (DMPA) and H-abstraction type photoinitiators
such as benzophenone (BP), thioxanthone (TX), camphorquinone (CQ), and classical
thermal initiator, 2,20-azobis(isobutyronitrile) (AIBN) at 80 8C. The kinetics of the reactions was
monitored online with a real time ATR-FTIR monitoring system and the conversions were
determined by 1H NMR spectroscopy. A comparison of click efficiencies of the studied initiator systems was
performed. Compare to the thermal initiators and Habstraction type photoinitiators, cleavage type photoinitiators
were found to induce thiol–ene click reactions with higher efficiency.