Change Material per frame

My goal is to change the material per frame so that when I render the first 15 frames I get a different material each frame. Here's what I have so far:

animate on
(
 for i=1 to 14 by 1 do
 (
  at time i
  (
   meditMaterials[i].DirectX_Manager.enabled = off
   $.material = meditMaterials[i]
  )
 )
)

it appears to go through all of the materials, but, when I try to render I only get the last material every frame.