Difference between Poplin and Twill
Poplin bears a smoother texture but similar weight to Oxford, the result of a fine yarn running one way with a thicker one interweaving it. It is soft and comfortable, and often used in more casual shirts. Colors find themselves easily at home here, and it takes sporty patterns especially well.
Meanwhile, twill, a shimmery diagonal weave, makes for richly textured shirts without sacrificing formality. In herringbone twill, the direction of the diagonals switches back and forth every quarter inch or so, giving the fabric even more depth. When occasion or whim calls for a solid shirt, twill plays the role with panache.
Poplin Polyester Blend
Both poplin and twill are available as cotton or polyester and a blend of both. Polyester blend is less expensive, however, they may not be as smooth as the cotton type. The good thing about the polyester version however is, it can be worn without ironing.