Chemical engineers will apply chemistry knowledge to the process of converting chemicals or raw materials into viable products for human use. They run large scale chemical reactions, and focus on processes to get molecules to react with one another at scale and with a desired process yield.
A materials scientist translates between what the chemists and physicists are working on, to what the engineering researchers are working on. They are responsible for the research, design, and development of materials, and will focus on how the physical structure of a certain material will affect the property of the material. They are essentially applied condensed matter physicists.