Complex sentence: In the spring of 1930, Carothers and his team had already synthesized two new polymers, one of which was neoprene, a synthetic rubber greatly used during the war and a white elastic but strong paste that would later become nylon.
Split into simpler sentences: In the spring of 1930, Carothers and his team had already synthesized two new polymers. The other was a white elastic but strong paste that would later become nylon.