Synthesis of Well-Defined Figure-of-Eight-Shaped Polymers by a Combination of ATRP and Click Chemistry

Well-defined figure-of-eight-shaped (8-shaped) polystyrene (PS) with controlled molecular weight and narrow polydispersities has been prepared by the combination of atom transfer radical polymerization (ATRP) and click chemistry. The synthesis involves two steps: 1) Preparation of a linear tetrafunctional PS with two azido groups, one at each end of the polymer chain, and two acetylene groups at the middle of the chain. 2) Intramolecular cyclization of the linear tetrafunctional PS at a very low concentration by a click reaction to produce the 8-shaped polystyrenes. The resulting intermediates and the target polymers were characterized by 1 H NMR and FT-IR spectroscopy, and gel permeation chromatography. The glass transition temperatures (T g s) were determined by differential scanning calorimetry and it was found that the decrease in chain mobility by cyclization resulted in higher T g s for 8-shaped polystyrenes as compared to their corresponding precursors.