Emotional vulnerability is extremely sexually arousing to me.
I can't think of a single larger turn-on for me than when I make myself emotionally vulnerable to a woman, and she reciprocates it kindly. It's more sexually arousing to me than many "directly" sexual things. Deeling emotionally "safe" with someone is just that important to me with regards to attraction.
The sexual arousal can occur without the conversation material having anything to do with sex; it can be about completely non-sexual topics, but I'll inadvertently pop a boner and begin to heavily fantasize about to her if the subject matter is personal and her response is positive.
On a related note, my sex drive is highly conditional upon my emotional state and whether or not I have a romantic crush or partner that I feel "open" with. My sex drive is very low when I'm single or when crushes are unrequited, but it shoots through the roof otherwise.
For what it's worth, I am a heterosexual male in my mid-twenties.