Tuning the polarity of ADMET derived star-shaped polymers via thiol-ene chemistry

The synthesis of defined star-shaped polymers via head-to-tail acyclic diene metathesis (ADMET) polymerization is described, whereby di(trimethylolpropane)tetraacrylate (4-arm) and dipentaerythritol hexaacrylate (6-arm) served as core units and fatty acid derived 10-undecenyl acrylate as unsymmetric α,ω-diene monomer. The core-first approach was applied to synthesize stars having arms of ten or twenty monomer units exhibiting an α,β-unsaturated ester backbone. Subsequent post-polymerization modification of the α,β-unsaturated esters via base-catalyzed thia-Michael addition is demonstrated. For this, five different thiols were used in a simple and efficient procedure, without observing degradation of the polymer backbone. The polarity of these star-shaped polymers could thus be tuned by choosing different thiols for this modification, as it was shown by determining the octanol water partition coefficients of these polymers by high performance liquid chromatography (HPLC).