Polylactide-Grafted Metal-Alginate Aerogels

Τhis work describes the synthesis of PLA-grafted M-alginate (g-M-alginate; M: Ca²⁺, Co²⁺, Ni²⁺, Cu²⁺) aerogels. DL-lactide (LA) was attached on the surface of preformed M-alginate beads and was polymerized, using stannous octoate as catalyst and the -OH groups of the alginate backbone as initiators/points of attachment. The material properties of g-M-alginate aerogels were not affected much by grafting, because the linear PLA chains grew on the M-alginate framework like a brush and did not bridge their points of attachment as in polyurea-crosslinked M-alginate aerogels. Thus, all g-M-alginate aerogels retained the fibrous morphology of their parent M-alginate aerogels, and they were lightweight (bulk densities up to 0.24 g cm^-3), macroporous/mesoporous materials with high porosities (up to 96% v/v). The BET surface areas were in the range of 154-542 m² g^-1, depending on the metal, the nature of the alginate framework and the PLA content. The latter was found at about 15% w/w for Ca- and Ni-based materials and at about 29% w/w for Co- and Cu-based materials. Overall, we have demonstrated a new methodology for the functionalization of alginate aerogels that opens the way to the synthesis of polylactide-crosslinked alginate aerogels with the use of multifunctional monomers.