Synthesis and characterization of cross-linked poly(acrylic acid)-poly(styrene-alt-maleic anhydride) core-shell microcapsule absorbents for cement mortar

We synthesized core-shell microcapsule absorbents with cPAA (cross-linked poly(acrylic acid)) as the core and PSMA (poly(styrene-alt-maleic anhydride)) as the shell by precipitation polymerization, where the shell served to delay the absorption of excess water in cement mortars. To control shell thickness, the cPAA-PSMA capsules were synthesized with core monomer mass to shell monomer mass ratios of 1/0.5, 1/1, and 1/1.5. We observed the hydrolysis of the PSMA polymer in a cement-saturated aqueous solution by Fourier transform infrared (FT-IR) spectroscopy. Furthermore, core-shell structures were observed for 1/1 (cPAA-PSMA #3) and 1/1.5 (cPAA-PSMA #4) core/shell monomer mass ratios, whereas no core-shell structures were observed for the 1/0.5 (cPAA-PSMA #2) microcapsules by transmission electron microscopy (TEM).