Calcium carbonate deposition on layer-by-layer systems assembled from star polymers

Layer-by-layer (LbL) systems constructed via electrostatic attraction or other forces can be used as templates in biomimetic mineralization. In this work, 21-arm star poly(acrylic acid) (star-PAA) and 21-arm star poly[2-(dimethylamino)ethyl methacrylate] (star-PDMAEMA) were successfully synthesized from a cyclodextrin core via atom transfer radical polymerization (ATRP). The star polymers were used to construct three kinds of LbL systems: negatively charged star-PAA with positively charged chitosan (CHI) as a model of unconfined space for mineralization, and positively charged star-PDMAEMA with negatively charged poly(styrene sulfonic acid) sodium salt (PSS), which had acid-etched holes or constructed within a porous polycarbonate filters, as two different models of confined space for mineralization. Different crystal forms of calcium carbonate were obtained using the three systems, so these LbL systems assembled from star polymers could be new tools for developing functional materials and investigating fundamental aspects of the mineralization process.