Mixing contracted and uncontracted phrases in the same sentence

Is there anything wrong with mixing contracted with uncontracted phrases in the same sentence?

Examples:

I'm not sure it is possible.

("I'm" is contracted, but "it is" is not).

I am not sure it's possible.

("I am" is not contracted, but "it's" is).

I know that it is not grammatically incorrect. But is it not recommended? Or is there any other reason to not use it?

Solution 1:

Is there anything wrong with mixing contracted with uncontracted phrases in the same sentence?

No, there isn't. You can freely write a word contracting it, and write another one without to contract it. As reported by Mr. Shiny and New, sometimes a word is written without to contract it to put emphasize on it.

Solution 2:

One valid use is when you want to emphasize one word:

I am NOT sure it's possible