Photoinduced Sequence-Controlled Copper-Mediated Polymerization: Synthesis of Decablock Copolymers.

Abstract

Photoinitiated copper-mediated radical polymerization offers an one-pot and time efficient method of preparing a decablock copolymer PMA-PtBA-PMA-PDEGA-PMA-PtBA-PMA-PDEGA-PnBA-PDEGA with an overall molecular weight of 8500 g·mol-1. The molecular weight is in close agreement with theoretical expectations and significantly narrow dispersities (Đ = 1.1-1.17) are achieved for the various block extensions. The tert-butyl group of the decadeblock was deprotected to form PMA-PAA-PMA-PDEGA-PMA-PAA-PMA-PDEGA-PnBA-PDEGA. The deprotection is confirmed by the disappearance of tert-butyl signal and the loss of molecular weight investigated by 1H NMR and SEC, respectively. The carboxylic group of PAA is protonated in acidic solution (water insoluble) and deprotonated in basic solution (water-soluble). This enables a conformational change of PMA-PAA-PMA-PDEGA-PMA-PAA-PMA-PDEGA-PnBA-PDEGA in water/ethanol mixture (80/20%v/v), as is demonstrated by a turbid solution at pH 2 and transparent solutions at pH 10.