Fun fact: cellulose (in wood) and chitin (in insect exoskeletons, fish scales, fungus cell-walls, etc.) are also polymers of glucose-derived sugars. Both are biodegradable, although humans can only digest the latter of the two.

Other fun fact: before the invention of entirely-synthetic plastics, we had phenolic sheets: layers of plain cellulose laminated together, originally using natural resin (tree sap), then later using synthetic resins, like Bakelite. These didn't have all the properties of synthetic plastics—you couldn't bend them, for example—but you could form them into shapes and introduce pigments, etc., while manufacturing. The earliest Printed Circuit Boards were Bakelite phenolic boards. (And even today, PCB insulator material is effectively a "synthetic phenolic board": it's fibre-reinforced plastic, which uses plastic itself in place of resin—and various synthetic fibres in place of cellulose—to achieve the same properties phenolic sheets have.)