Programmable Disassembly of Polymer Nanoparticles through Surfactant Interactions

Abstract

The disassembly of well-defined random copolymer nanoparticles to unimers at precise times can be programmed through the strong interaction with the surfactant, sodium dodecyl sulfate (SDS). The random copolymers consisted of thermoresponsive and self-degradable monomer units, rapidly self-assembled in water above the lower critical solution temperature of the thermoresponsive polymer component into SDS-stabilized polymer nanoparticles at a high weight fraction of polymer, a fully reversible process. Increasing the SDS concentration resulted in an increase in the nanoparticle size from ∼60 to ∼500 nm while maintaining a very narrow particle size distribution. These particles once formed were stable even under highly dilute conditions (i.e., an ∼10-fold dilution). Due to the self-catalyzed hydrolysis of the (N,N-dimethylaminoethyl acrylate) (DMAEA) to acrylic acid within the polymer, the nanoparticles rapidly disassembled back to unimers when the LCST of the hydrolyzed polymer was equal to or greater than the set solution temperature of 37 °C. The time to disassembly from nanoparticle to unimer was programmed through the amount of hydrophobic (butyl acrylate or styrene) units in the copolymer in combination with the amount of SDS. The higher hydrophopic content in the polymer resulted in longer disassembly times, while the higher SDS concentration reduced the disassembly time. Importantly, the self-catalyzed hydrolysis property of PDMAEA was not affected by SDS, allowing precise tunability of the time required for disassembly of the polymer nanoparticles. This active disassembly of nanoparticles provides a unique system that responds without an external trigger (e.g., light, heat, etc., ...) and could find applications where timed-release of compounds or timed activation of enzymes and other biocomponents is required.