Why can't you create a balloon that doesn't deflate?

I've been looking it up and balloons deflate because rubber's got gaps and air escapes through the gaps, to balance the pressure from within the balloon with the pressure from outside the balloon.

I've found durable balloons and reusable balloons, but nothing about permanent balloons that prevent deflation.

If the biggest gas molecules were contained within a balloon made from a material that can inflate, would the gaps still be big enough for the gas to escape?