Solvent Controls Nanoparticle Size during Nanoprecipitation by Limiting Block Copolymer Assembly

Area of Science:

• Materials Science
• Nanotechnology
• Polymer Chemistry

Background:

• Controlling nanoparticle (NP) properties, especially size, is crucial for biomedical and engineering applications.
• Nanoprecipitation is a common method for producing polymeric NPs, involving rapid mixing of a block copolymer solution with a nonsolvent.
• The influence of solvent choice on NP size is empirically observed but mechanistically unclear.

Purpose of the Study:

• To elucidate the mechanism by which solvents control polymeric nanoparticle size during nanoprecipitation.
• To identify the role of solvent properties in limiting block copolymer assembly and NP growth.

Main Methods:

• Investigated the effect of solvent on block copolymer assembly during nanoprecipitation.
• Analyzed polymer aggregation dynamics and growth via polymer exchange.
• Developed and utilized an a priori model based on spinodal decomposition to explain size control.

Main Results:

• Solvent choice dictates NP size by limiting block copolymer assembly and subsequent growth.
• Polymer aggregates form dynamic structures that grow through polymer exchange until growth arrest.
• A solvent-specific critical water fraction determines the point of growth arrest, thereby setting the final NP size.

Conclusions:

• The solvent's critical water fraction directly controls the extent of dynamic growth, ultimately determining nanoparticle size.
• The proposed mechanism, supported by a spinodal decomposition model, allows for prediction of NP size scaling.
• This understanding facilitates more efficient engineering of polymeric nanoparticles for targeted applications.