hydrolysis of block copolymers at the water-oil interface*

Understanding the behavior of polymer chains at interfaces and the effects of polymer composition and architecture on interfacial behavior is critical in designing novel polymer emulsifiers. In this work, a series of linear and bottlebrush block copolymers of poly(styrene-b-solketal methacrylate) (PS-b-PSM) have been used to investigate and in-situ hydrolysis, where the hydrophobic PSM block is converted into a hydrophilic glycerol monomethacrylate (PGM) block. The In-situ interfacial tension was measured to monitor the evolution of the conversion brought about by the interfacial reaction. PS-b-PSM adopts a Janus-type behavior at the interface activity even before conversion, due to preferential affinity of PSM to aqueous water phase. As interfacial hydrolysis proceeds, the PSM block becomes more polar, significantly increasing the amphiphilicity of the block copolymer, along with a corresponding reduction in the interfacial tension. The Janus character of PS-b-PSM were also changed by varying the molecular weight, volume fraction, end groups and architecture to investigate the influence of these parameters on the interfacial evolution behavior through the in-situ hydrolysis.