Summary of main observation and conclusion
Physical encapsulation of drugs into polymer micelles is a common method of loading hydrophobic drugs. Methoxy polyethylene glycol‐poly(D,L‐lactide) (mPEG‐PDLLA) is one of the most commonly used drug carrier. At present, whether a carrier is suitable for the loading of a certain drug is determined by drug loading experiments. This process costs a lot of time. Therefore, an efficient predicting method to avoid time‐consuming tests is critical. In this study, we prepared mPEG5k‐PDLLA5k and used it to load a series of drugs. Three parameters were used to test the miscibility of mPEG5k‐PDLLA5k with drugs, including absolute difference in Hildebrand solubility parameters (|Δδ|), Flory–Huggins interaction parameter (χ) and the distance (D value) calculated from the two‐dimensional solubility parameters. We found the two‐dimensional solubility parameters obtained from JB2013 group contribution (GC) method was useful. By comparing the drug loading content (DLC) with the D value, we found that when the D value was less than 5.0 (MJ/m3)1/2, the miscibility of drug and mPEG5k‐PDLLA5k was good and drug loading capability was high; when the D value was more than 8.0 (MJ/m3)1/2, the drug was barely loaded. Thus, this work provided a rationale to qualitatively predict the loading capability of mPEG5k‐PDLLA5k for hydrophobic drugs.