Abstract
An atom-efficient, wholly aqueous one-pot synthesis of zwitterionic diblock copolymers has been devised. Such copolymers can serve as highly effective aqueous dispersants for nano-sized transparent yellow iron oxide particles.
Highlights
Zwitterionic polymers, known as polyampholytes, contain both cationic and anionic monomer repeat units.[1,2,3,4,5,6,7] they differ from polybetaines, which possess anionic and cationic groups within the same repeat unit.[8,9,10,11] Unlike polybetaines – and zwitterionic statistical copolymers12 – many zwitterionic diblock copolymers, sometimes known as ‘block polyampholytes’, exhibit an isoelectric point (IEP) in aqueous solution owing to charge compensation
Aqueous electrophoresis studies indicate that the isoelectric point (IEP) exhibited by such zwitterionic diblock copolymers in aqueous solution can be tuned by varying the relative proportions of the anionic and cationic comonomers
A one-pot protocol utilizing poly(2-(dimethylamino)ethyl methacrylate) (PDMA) as the first block was optimized as follows: firstly, a PDMA50 precursor was prepared at 40% w/w solids by reversible addition–fragmentation chain transfer (RAFT) aqueous solution polymerization of DMA at 44 °C using PETTC and VA-044 initiator, see Scheme 1
Summary
Efficient stabilization was achieved at just 0.3% dispersant relative to the mass of pigment. A typical protocol for the synthesis of a PMAA50-PDMA50 (target DP) zwitterionic diblock copolymer was conducted as follows: MAA (1.0 g, 11.6 mmol), PETTC (78.9 mg, 0.23 mmol), ACVA (13 mg, 46.4 μmol) and deionized water (6.19 g) were added to a 50 mL two-necked round-bottomed flask. This aqueous reaction mixture was purged for 30 min with nitrogen and heated to 70 °C. TEM images were recorded using a Philips CM100 instrument operating at 100 kV and equipped with a Gatan 1k CCCD camera
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