Usage Note: Unaware, followed by a prepositional phrase with of (expressed or implied), is the usual adjectival form modifying a noun or pronoun or following a linking verb: Unaware of the difficulty, I went ahead. She plunged into a dangerous situation wholly unaware. He was unaware of my presence. Unawares is the usual adverbial form: The rain caught them unawares (without warning). They came upon it unawares (without design or plan).
The American Heritage® Dictionary of the English Language, Fourth Edition