Compositions and method of manufacturing carboxypolysaccharides (CPS) including carboxymethyl cellulose (CMC) and polyethylene glycols (PEGs) are provided where the PEG is a PEG-epoxide covalently linked to the CPS. In certain embodiments, the PEG attaches to only one CPS, forming a decorated CPS. In other embodiments, the functional groups of a bi-functional PEG molecule (PEG diglycidyl ether) are attached to different CPSs, thereby forming a covalently cross-linked composition. Such compositions can be used as space-filling materials, load-bearing materials, anti-adhesion compositions, drug delivery vehicles, and lubricants of tissues and medical instruments.