Rihanna caught out by Chris Brown collaboration criticism

Rihanna was blindsided by the criticism fired at her for reuniting with ex-boyfriend Chris Brown in the studio - because she didn't think anyone would care that the former lovers were working together.

Brown and Rihanna recently worked on two tracks together, prompting critics to slam the Umbrella hitmaker for teaming up with the ex who left her black and blue after a pre-Grammy Awards fight in 2009.

The Kiss Kiss singer was later charged with assault and told to keep his distance from his ex.

The latter demand was dropped last year (11) allowing Brown to hit the studio with Rihanna in early 2012.

And the pretty star is still reeling from the backlash.

She tells Esquire magazine, "It never occurred to me how this was going to be a problem. I thought people were gonna be surprised that we finally did a record together, but I didn't see how people could think it was a bad thing, you know? In my mind, it was just music... I could never see anything wrong with making music."

And she insists there was nothing romantic going on behind closed doors as the former couple worked together, insisting it was "a completely professional environment".

She adds, "If I went back to him (as a girlfriend), then that's a whole different discussion... If I ever do, then that's something that y'all have to talk to me about when - if - that ever happens. Until then, look at it for what it is."

Brown and Rihanna teamed up in the studio to record the remix for her single Birthday Cake and she also agreed to sing a verse on his Turn Up the Music single.