Capsules are primarily made of lipopolysaccharides, while slime layers are composed of peptidoglycan

Both capsules and slime layers are primarily composed of polysaccharides, but capsules may also include polypeptides

Capsules consist exclusively of polypeptides, while slime layers are made of polysaccharides

Slime layers are more likely to be composed of nucleic acids, whereas capsules contain glycoproteins