Estimation of Hydrophile-Lipophile Balance for mPEG-PLA by Group Contribution Method

HLB (Hydrophile-Lipophile Balance) values of methoxy poly (ethylene glycol)-poly (lactic acid) (mPEG-PLA) samples were measured by water number method.A linear relationship was showed between the HLB values and the volume fraction of mPEG (φ_EO) in its molecule.The Gamma probability density function (PDF) was used to describe the contribution of single PLA group to HLB,and the effective chain length of PLA chain could be calculated by integrating Gamma PDF.Therefore,HLB of mPEG-PLA can be estimated by group contribution method,and the average absolute error is less than 0.97,which is better than the results calculated by Griffin's method.