DowDuPont Inc., created from the merger of the largest U.S. chemical companies, is learning from Chief Executive Officer Ed Breen that one way to make more money is to abandon more research.

The company has ended its most ambitious research and development projects—what he calls “moonshots”—because they are expensive, require years of work, and sometimes have poor prospects for investment returns, the CEO said May 31. Instead, DowDuPont is focused on smaller projects that cost no more than $30...