JaJuan Johnson spent the final 4:54 of the first half on the bench with two fouls.
But it didn't matter for No. 8 Purdue.
Ryne Smith, Terone Johnson and E'Twaun Moore were enough in that stretch to give the Boilermakers a 41-31 lead at halftime.
IU scored a pair of points off JaJuan Johnson's second foul to pull with 28-27.
But then Smith made a three-pointer from the wing, Terone Johnson made back-to-back three-pointers and Moore scored the team's final four points of the half to take a 41-31 lead.
Purdue shot 61 percent in the half.