Mesh renderer - more than one material in submeshes

I'm using 3d Quad object to make infinite, scrolling, parallax background in my 2D unity game. I have a 4 submeshes in my mesh renderer. There are 3 materials (I have added an animation to it) in submesh number two.

To make parallax effect I'm using materials[i].mainTextureOffset

Everything works perfectly with only one material in submesh, but it doesn't work with animation.

Offset is changing when player is moving:

 offset[i] = new Vector2(playerPosition.x / (1000 / parallaxspeed[i]), rendererTextures.materials[i].mainTextureOffset.y);
 rendererTextures.materials[i].mainTextureOffset = offset[i];