Dr. Asa Breed
Asa is the vice president of the Research Laboratory at General Forge. Dr. Breed takes John on a tour of the facility and lets John interview him about Dr. Felix Hoenikker—until he becomes angry about John's supposed bias against science and ends the interview abruptly.
So what does Dr. Breed do for us?
1) He gives us exposition. Basically, he tells John, and the reader, what we need to know to understand what ice-nine is and what it does. Although Breed believes it's all theoretical, when ice-nine turns out to exist, it works exactly as Breed describes it.
2) Breed's character provides a few of the novel's jabs against scientific culture. Dr. Breed says he is "sick of people misunderstanding what a scientist is, what a scientist does" (18.14). He claims a true scientist works for research only, meaning he attempts "to increase knowledge, to work toward no end but that" (18.20). Commercial and military concerns don't play into "real" science for Breed.
But Vonnegut seems to think they should. During the ice-nine discussion, Breed gets angry when John considers the ramifications of the polymorph, because he believes ice-nine to be nothing more than a thought experiment. But we later learn that ice-nine does exist—with disastrous consequences. In short, the novel paints Breed's view of science as glorified but also very shortsighted concerning that minor thing we call reality.