Aggregate thory of polymers Experiments showed that some natural materials, such as starch, proteins, cellulose, and rubber, had incredibly high molecular masses. To explain these data, some scientists in the second half of the 19th century proposed that these materials were made of small molecules that somehow clumped together in aggregates to give the false impression of giant molecules. These materials often behaved like glue in solution, so they were called colloids, from the ancient Greek word kolla, meaning "glue." The aggregate theory of polymers pervaded through the early part of the 20th century, when it was challenged by Hermann Staudinger (1881–1965).