Rushbrooke's research career began as a graduate student of Ralph Fowler at Cambridge University, where they investigated solutions in which one component is a dimer. After his graduate work he was appointed as a research assistant at Bristol University and from there moved to research and teaching fellowships at Dundee; it was at Dundee that he met with Charles Coulson, with whom he developed a lifelong friendship and collaborated on many topics in theoretical and physical chemistry.
1944 saw Rushbrooke's appointment to a lectureship at Leeds University, where he lectured on statistical mechanics to final year honours chemistry students. These lectures became the basis of his book Introduction to Statistical Mechanics (1949). Rushbrooke's book managed to show how much statistical mechanics was possible using only elementary mathematics, contrary to the vogue at the time. 1949 was also significant as the year in which Rushbrooke married Thelma Barbara Cox.
Rushbrooke's next appointment was as a senior lecturer in theoretical physics at Oxford University, from whence he moved to the newly created chair of Theoretical Physics at the University of Newcastle in 1951.
As a researcher into statistical mechanics Rushbrooke made contributions to the equilibrium theory of fluids (where he emphasized the role of the pair-correltation function), but is probably best remembered for his work on inequalities in critical exponents (which he established on thermodynamic grounds) which laid the foundations from which the modern theory of critical phenomena emerged.
Rushbrooke retired in 1980 to become emeritus professor, and was a familiar face in the Physics Department until weeks before his death in 1995.
C. Domb, Stanley Rushbrooke 1915-95, Physics World, April 1996, 62-63.