Polyethylene-poly(methyl acrylate) Block Copolymers from PACE-SARA ATRP: Utilizing Polyolefin Active Ester Exchange-Based Macroinitiators in Atom Transfer Radical Polymerization

Accessing a facile pathway to prepare polyolefin-polar
block copolymers
with low dispersity and high control remains a challenge due to the
distinct polymerization pathways of the composing blocks. This study
utilized the polyolefin active ester exchange, the PACE approach,
as a viable solution. The PACE approach, using palladium-catalyst-based
coordination-insertion polymerization, was combined with SARA ATRP
(supplemental activator/reducing agent atom transfer radical polymerization).
A single-chain-end active ester functionalized polyethylene (PE) was
produced from an α-diimine Pd(II) hexafluoroisopropyl ester
chelate complex, which facilitated a living polymerization of ethylene.
Transesterification with 2-hydroxyethyl α-bromoisobutyrate (HOBIB)
or 2-hydroxyethyl α-bromoisobutyramide (HOBIBA) formed α-bromoisobutyrate
or α-bromoisobutyramide chain-end-functionalized polyethylene.
The approach resulted in controlled synthesis of polymers with low
dispersity (Đ), high initiation efficiency,
and high reproducibility. Both the amide-linked and ester-linked macroinitiators
showed >90% initiation efficiency and Đ values
of block copolymers as low as 1.05. This work demonstrated a successful
combination of two living polymerization techniques, an insertion
and controlled radical polymerization, unified in PACE-SARA ATRP,
offering access to polyolefin-containing block copolymers with chemically
distinct structures.