Collocations for unconcerned - adj.

act, appear, be, look, seem, sound
I tried to act unconcerned.

remain

completely, quite, totally, utterly
blissfully, blithely
remarkably
largely, relatively
apparently, seemingly

about
They appeared completely unconcerned about what they had done.

by
He was apparently unconcerned by his failure to get the job.

with
Bennett is unconcerned with such matters.