After two years of postdoctoral work at the University of Paris and UC Berkeley, he joined the Berkeley faculty in 1972, continuing his researches on the quantum theory of molecular spectroscopy and photochemistry. In 1975 Bill moved to UCLA, switched fields, and became a leader in the then-emerging area of "complex fluids," contributing significantly to the statistical mechanical theory of liquid crystals, surfactant solutions, polymers, colloids, and self‐assembling systems. 25 years later, he became deeply intrigued by viruses and, with Charles M. Knobler at UCLA, established a laboratory to investigate simple viruses outside their hosts and isolated in test tubes. In parallel, with Avinoam Ben-Shaul of the Hebrew University of Jerusalem, he developed — also starting around 2000 — a theoretical program for elucidating the physics of genome packaging and delivery in DNA and RNA viruses. This work, along with that of several other groups in the States and Europe, helped launch the burgeoning field of "physical virology." Most recently, he has begun to work on the in vitro reconstitution of virus-like particles as vectors for RNA gene delivery.

Bill's interdisciplinary research has been recognized by many awards, including the 1991 Lennard‐Jones Medal of the British Royal Society, a 1998 Guggenheim Fellowship, the 2001 Liquids Prize of the American Chemical Society, election to the American Academy of Arts and Sciences in 2009, and endowed lectureships at the Curie Institute (Paris), the University of Leeds (England), Case Western Reserve University, Cornell University, Carnegie Mellon University, and the University of Pittsburgh. At UCLA he won the 1996 University Distinguished Teaching Award, and served as Chair of the Department of Chemistry and Biochemistry (2000-2004).

For his current research, and recent publications, see http://virus.chem.ucla.edu.