The forming mechanism and optimizing of natural polymer foam based on magnolol extracted from Chinese herbal medicine

Magnolol is a Chinese medicinal herb that has been used for treating cough, phlegm and inflammation for a thousand years. Given its low absorption rate, which limits its use, there is a need to develop porous magnolol foams that are light weight, low density, portable while maintaining tissue integrity to expand its application. This study proposes an innovative method for creating a biocompatible foam through a one-pot process involving the reaction of magnolol with sulfhydryl compounds, using a thiol-ene click reaction to form a foam. Various foams were systematically formulated by adjusting the degrees of cross-linking, concentrations of the foaming agent 2,2'-azobis(2-methylpropionitrile) (AIBN), and the temperature and pressure conditions during the foaming. AIBN acted both as a blowing agent and initiator, triggering cross-linking in the polymer solution by releasing free radicals and nitrogen gas. This initiated rapid expansion when a critical viscosity threshold was reached, ultimately curing the foam. The optimal foaming efficiency was achieved when the molar ratio of allyl to mercapto groups was maintained at 1:1, with pentaerythritol tetrakis(3-mercapto-propionate) (PETMP) identified as the optimal sulfhydryl compound. Increasing the dosage of AIBN enhanced gas generation, further expanding foam volume, pore size and porosity. The foam is lightest when the AIBN content is 7.5%. When magnolol-based foams were prepared under sealed conditions at 100°C, without external pressure, they exhibited large, uniformly distributed pores and excellent water-absorbing properties. Moreover, the resulting foams demonstrated remarkable thermal stability and resilience.Therefore, the magnolol foam prepared in this study is expected to be combined with negative pressure drainage and applied in fields such as wound healing and hemostasis. These findings also offer a new design strategy for engineering high-performance functional magnolol foams with high biomass content.