Characterisation of poly(lactic acid):poly(ethyleneoxide) (PLA:PEG) nanoparticles using the self-consistent theory modelling approach

Self-consistent field (SCF) modelling studies can be used to predict the properties of poly(lactic acid):poly(ethyleneoxide) (PLA:PEG) nanoparticles using the theory developed by Scheutjens and Fleer. Good agreement in the results between experimental and modelled data has been observed previously for a series of PLA:PEG nanoparticles with a constant 5 kDa PEG block and a variable PLA block. In the present work, a comparison is performed between PLA:PEG nanoparticles having 5 and 10 kDa PEG blocks with varying PLA blocks (2–4 kDa). The calculated volume fraction profiles show that the PLA core region of the PLA:PEG 5 kDa series is larger than for the PLA:PEG 10 kDa series, whereas the PEG corona region of the PLA:PEG 10 kDa series is larger than that of the PLA:PEG 5 kDa series due to the presence of the longer PEG chain. The results indicate that the aggregation numbers of the 5 kDa series are larger than for the 10 kDa series due to steric effects associated with the PEG layer, even though the particle radii for the 10 kDa series are larger than for the 5 kDa series. The surface area available on the PLA core for each PEG chain is greater for the 10 kDa PEG series indicating that the 5 kDa PEG series has a denser PEG layer.