Dear Shen Su, solubility parameters such as Hildbrand, Hoy, and Hansen are all derived based on the Cohesive Energy Density (CED), which is in the case of polymers a function of chain length or molecular weight (MW). So, differences of values of the solubility parameter for the same polymer are due mainly to two reasons :

- differences in the characteristics of the polymer mainly MW and chain architecture (linear, branches, ...)

- differences due to the different techniques used to get the solubility parameter.

My Regards

Dear Shen,

I agree with you that HSP of PLA, PBS, PBAT and PCL can be very distinct, and this can be assumed by considering firstly the physicochemical differences between these biopolyesters.

The problem is more complicated, where the literature is given different values regarding the solubility parameters for the same polymer, e.g., let’s go to consider the case of PLA.

Firstly, I would recommend to use the official site Hansen Solubility Parameters (HSP) to obtain more information (https://www.hansen-solubility.com/ ). Regarding the PLA (https://www.hansen-solubility.com/HSP-examples/pla.php ): “However, with a few solubility data points from an academic journal it was possible to estimate the HSP of PLA via the Sphere fit. Although this particular fit gives HSP of [19, 10, 6] some further sanity checking gave a value of around [18.5, 8, 7].”

For instance, between the most cited values ​​(δd, δp and δH) are respectively 18.6, 9.9 and 6.0 (see as reference the book: Poly(lactic acid) Science and Technology. Proccesing, Properties, Additives and Applications (2014): Royal Society of Chemistry, Editors: Alfonso Jiménez, et al.; or as previous reference, S. J. Abbott, in Poly(lactic acid): Synthesis, Structures, Properties, Processing, and Applications, Wiley, 2010, pp. 83–93).

On the other hand, please consider that the different grades of PLA could show different behavior in traditional solvents (THF, DCM, CHCl3, etc.) point of view solubility. I believe that the molecular weights of PLA and especially the isomer purity (L- or D- isomer) in connection to the degree of crystallinity could influence (more or less) the solubility parameters, but unfortunately, for the moment these aspects are less considered in the studies realized up to now…

Good luck in finding the most helpful information,

Marius

Dear Shen,

Please consider bellow some selected references that could be of help for more information.

Good luck and best regards,

Marius

Selected references:

Sato, S., Gondo, D., Wada, T., Kanehashi, S. and Nagai, K. (2013), Effects of various liquid organic solvents on solvent‐induced crystallization of amorphous poly(lactic acid) film. J. Appl. Polym. Sci., 129: 1607-1617. doi:10.1002/app.38833

https://onlinelibrary.wiley.com/doi/10.1002/app.38833

K.Adamska et al., The solubility parameter for biomedical polymers—Application of inverse gas chromatography, Journal of Pharmaceutical and Biomedical Analysis 127 (2016) 202–206

https://www.sciencedirect.com/science/article/abs/pii/S073170851630200X?via%3Dihub

C. Bordes, et al., Determination of poly(ɛ-caprolactone) solubility parameters: Application to solvent substitution in a microencapsulation process, International Journal of Pharmaceutics, Volume 383, Issues 1–2, 2010, Pages 236-243, https://doi.org/10.1016/j.ijpharm.2009.09.023