Solarcoin was listed on Poloniex back in 2014 for a while, but it got removed due to extremely low volume. Main exchange at the beginning was Allcrypt (which was hacked btw and closed after that).

I wouldn't count on Poloniex adding Solarcoin before they officially announce it on Twitter. They do add coins from time to time, but trading volume needs to be quite high for a while on other exchanges.

Btw. mining rig rentals pointed at Solarcoin from 2014 seem to be paying themselves back slowly, too bad that I didn't hold all of the mined coins