Microporous materials that include thermoplastic organic polyolefin polymer (e.g., ultrahigh molecular weight polyolefin, such as polyethylene), particulate filler (e.g., precipitated silica), and a network of interconnecting pores, are described. The microporous materials of the present invention possess controlled volatile material transfer properties. The microporous materials can have a density of at least 0.8 g/cm3; and a volatile material transfer rate, from the volatile material contact surface to the vapor release surface of the microporous material, of from 0.04 to 0.6 mg/(hour*cm2). In addition, when volatile material is transferred from the volatile material contact surface to the vapor release surface, the vapor release surface is substantially free of volatile material in liquid form.