Vollmer was third at the turn and hit the wall in 55.98 seconds to shave 0.08 off the previous mark set by Sarah Sjostrom of Sweden at the 2009 world championships in Rome.
Vollmer had set an Olympic record in Saturday morning's heats. She missed qualifying for the 2008 Beijing Games.
Lu Ying of China touched second in 56.87 and Alicia Coutts of Australia finished third in 56.94.
Sjostrom was fourth.