Calcium alginate is a water-insoluble, gelatinous, cream coloured substance that can be created through the addition of aqueous calcium chloride to aqueous sodium alginate.
In molecular terms, alginate consists of a family of unbranched binary copolymers of(1+4)-linked p-D-mannuronic acid (M) and a+guluronicacid (G) of widely varying composition and sequentialstructure (4). Alginates are true block copolymers composedof homopolymeric regions of M and G, termedMM and GG blocks, respectively, interspersed with regionsof alternating structure (MG blocks) (5). In solution,alginates behave like flexible coils.
When sodium alginate is put into a solution of calcium ions, the calcium ions replace the sodium ions in the polymer. Each calcium ion can attach to two of the polymer strands. This is called
cross-linking and can be represented like this: