What characteristic defined the fundamental shift in material science from Celluloid to Bakelite?

The transition from semi-synthetic materials based on natural polymers to fully synthetic materials.

The development of plastics shows a distinct chemical progression marked by increasing synthetic complexity. Parkesine and Celluloid are categorized as semi-synthetics because their base structure is cellulose, a naturally occurring polymer found in plants. While these materials were chemically altered (modified), their foundation remained tied to natural resources. The introduction of Bakelite marked the genuine synthetic leap. Leo Baekeland engineered a polymer entirely from non-naturally occurring components—phenol and formaldehyde. This meant chemists gained mastery over molecular bonding without relying on the structural limitations of natural precursors, ushering in the age of truly synthetic polymers.