I've used tons of poly cotton...sure you can use it. But there is a difference between it and cotton.
Some of the poly cotton I've used doesn't iron well. Other irons just fine.
Poly double knit is VERY, very hard to FMQ on a domestic machine. Yikes...I was given some quilt tops to finish that were double knit. I will gently refuse any more. They don't move easily and weigh a ton.
(And I hate touching the stuff!)
However...poly cotton I will use and probably will continur to use. Not all poly cotton pills, but some does.
Given for all the negatives about the double knit--it will last forever, so to speak. All have been quickly chosen (as charity quilts here in Poland - I give recipients a choice from at leat 10 quilts--sometimes as many as 50 to choose from).