Internal Correlations and Stability of Polydots, Soft Conjugated Polymeric Nanoparticles

Conjugated polymers collapsed into long-lived highly luminescent nanoparticles, or polydots, have opened a new paradigm of tunable organic particles with an immense potential enhancing intracellular imaging and drug delivery. Albeit the chains are not in their equilibrium conformation and are not confined by cross-links, they remain stable over astounding long times. Using fully atomistic molecular dynamics simulations with an innovative method to controllably collapse an inherently rigid polymer, we determined for the first time the internal structure and stability of polydots made of dialkyl-para-phenylene ethynylene, immersed in water, a biological relevant medium. In contrast to natural aggregates, the aromatic rings within the polydots are uncorrelated, with little to no water in its interior. This lack of correlation explains the differences of luminescence characteristics between spontaneously aggregated conjugated polymers and polydots. Resolving the conformation and stability of these particles will enable transforming an idea to a new effective tool.