Physiological pH-triggered morphological transition of amphiphilic block copolymer self-assembly

In order to develop polymeric self-assembly with an intelligent morphological transition property under appropriate stimuli, a series of pH-sensitive amphiphilic block copolymers have been prepared via atom transfer radical polymerization (ATRP). Due to the delicately designed macromolecular structure, poly(ethylene glycol)₄₄-b-poly(2-diisopropylaminoethyl methacrylate)₁₅ (PEG₄₄-b-PDPA₁₅) could form self-assemblies with a controllable morphological transition in response to the physiological pH changes. As demonstrated by the results of dynamic light scattering (DLS) records and transmission electron microscopy (TEM) micrographs, PEG₄₄-b-PDPA₁₅ could self-assemble into toruloid aggregates arranged by several single micelles at pH 7.4, but the morphology changed into uniform single micelles at pH 6.5. With a further decrease of pH value to 5.5, PEG-b-PDPA became double hydrophilic and could not self-assemble into any nanostructure. Therefore, this block copolymer provides a feasible approach to construct a nanoscale smart self-assembly with adjustable morphologies, which exhibits its potential for biomedical applications with specific physiological pH stimuli, such as intracellular delivery and tumor therapy.