Amphiphilic block copolymer features unique properties as functional materials. The development of amphiphilic block copolymer type surfactant has drawn considerable attention due to their application potential in various industrial circumstances. Block copolymers with both hydrophobic and polyelectrolyte segment at the same time could offer advantages because of their unique structure. Among those, polyacrylic acid (PAA) is a hydrophilic polymer that widely used in amphiphilic block copolymers and demonstrates ideal property in emulsion polymerization.

A research group led by Prof. ZHANG Yagang and Prof. Wumanjiang Eli at Xinjiang Technical Institute of Physics & Chemistry (XTIPC) of Chinese Academy of Sciences designed and synthesized Gemini-like Methyl Acrylate-Acrylic Acid-Methyl Acrylate triblock copolymers surfactants by reversible addition-fragmentation chain transfer (RAFT) polymerization and investigated their behavior at the air–water interface.

Researchers obtained the amphiphilic triblock copolymers (PMA-PAA-PMA) as a gemini surfactant including two hydrophobic groups (sometimes three) and two hydrophilic groups in the polymer chain, connected by a linkage close to the hydrophilic groups. Among them, PMA was the hydrophobic group and part of the RAFT agent served as the linking group.

They employed 1H NMR spectroscopy, thermogravimetric analysis (TGA), gel permeation chromatography (GPC), transmission electron microscopy (TEM) and dynamic light scattering (DLS) separately to characterize these triblock copolymers and their common Methyl acrylate (MA) homopolymer precursor according to their compositions, molecular weights and behavior at the air-water interface. TEM study showed that PMA-PAA-PMA formed a special vesicle structure with large membrane thickness which leads to low critical micelle concentration and surface tension of water.

Compared with conventional surfactants, Gemini-like triblock copolymers surfactants by RAFT polymerization showed that one could control the interfacial properties by changing the linkage group (RAFT agent) which would induce significant property changes on the specific surfactant.

These surfactants designed and synthesized have great application potential in industrial, cosmetics as well as environmental science.

The result is published in Journal of Surfactant and Detergent. This work was financially supported by the “One Thousand Talents” Program of China, the National Natural Science Foundation of China, etc.

Figure: Graphical illustration of new Gemini-Like triblock copolymers surfactants by RAFT polymerization and investigation of their Behavior at the air–Water Interface. (Image by XTIPC)