You need to change the column to NTEXT or NVARCHAR(MAX).
Collation only relates to sort order, indexing, and comparisons. If you stored only Chinese data, you can use Chinese_PRC_90_CI_AI or a related collation.
update after 1st comment:
For NVARCHAR (and NTEXT), the collation setting does not affect the way data is stored. As I stated before, it affects comparisons and sorting.
If you know that there will be Chinese data in a field, it's best to use a Chinese collation. (I just recently experienced some problems when searching for Chinese characters, as in some collations some characters equal punctuation characters)
If you know that you are searching for data in other languages, you can still change the collation using the COLLATE clause in comparisons or ORDER BYs