Poplin has long been the choice pajama fabric for men in the know. Plain woven cotton yarns make a smooth and comfortable fabric that s lightweight and breathable. Buttondown pajama shirts are harder to find these days, but we appreciate their classic look. Thoughtful details include piping, a comfortable rounded placket and a clean-finished back neck seam, while functional convenience comes from a handy hanger loop in back, a chest pocket and secure cross-stitched buttons..