There are, but new characters are not introduced into the language to represent them. Since there are over 10,000 characters in use (over 30,000 in total), old characters are chosen to represent the writing of new slang.

So, as the language grows with new words, the writing of these new words uses old known characters, no new characters are ever introduced.

For example:

"No way" is represented by "没门", two known characters, pronounced "mei men", that mean "not/no" and "door/entrance/gate" respectively.