There is no material that will not bend light. All materials, to some degree, will bend light. This bending of light is called refraction.

Here's why:

* Light interacts with matter: When light passes from one medium to another (like from air to water), it changes speed. This change in speed causes the light to bend, or refract.

* Index of refraction: Each material has a different index of refraction, which measures how much light bends when it enters that material. A higher index means more bending.

* Vacuum is the exception: The only medium where light doesn't bend is a perfect vacuum, which contains no matter. In a vacuum, light travels at its maximum speed, the speed of light.

So, while some materials might bend light very little, there's no material that completely avoids refraction.