An exact comb polyisoprene (PI) with three branches, with the middle branch having twice the molecular weight of the two other identical external branches, was synthesized by using anionic polymerization high vacuum techniques and appropriate chlorosilane chemistry. The synthetic approach involves (a) the selective replacement of the two chlorines of 4-(dichloromethylsilyl) diphenylethylene (DCMSDPE, key molecule) with identical PI chains by titration with PILi, (b) the addition of sec-BuLi to the double bond of DPE followed by the polymerization of isoprene from the newly created anionic site to form a 3-arm living star PI, (c) the selective replacement of the two chlorines of trichloromethylsilane with 3-arm star PI to form an H-shape intermediate, and (d) the replacement of the remaining chlorine of trichloromethylsilane by linear PI chains with double the molecular weight. All intermediate and final products were characterized via size exclusion chromatography, temperature gradient interaction chromatography and 1H-NMR spectroscopy. As expected, due to the inability to control the exact stoichiometry of the linking reactants, the main product (exact comb PI) is contaminated by a few by-products, despite the fact that anionic polymerization is the most efficient way to produce well-defined polymers. © 2013 The Royal Society of Chemistry.
Bibliographical noteKAUST Repository Item: Exported on 2020-10-01
Acknowledgements: KR is thankful to the Industrial Chemistry Laboratory of the University of Athens for providing guidance and laboratory facilities, as well as to the Marie-Curie DYNACOP (PITN-GA-2008-214627) project for financial support. TC acknowledges the supports from NRF (2008-0061892 and 2012R1A2A2A01015148).
ASJC Scopus subject areas
- Organic Chemistry
- Biomedical Engineering
- Polymers and Plastics