Therefore, the ratio between volumes of interface material to the volume of the particle (Vinterface/Vparticle) increases with the decrease of particle size. The aspect ratio (the ratio of the diameter (2r) to the length (L)) determines the morphology of the polymers. Based on the aspect ratio, the morphology can be a plate, sphere, and rod with an aspect ratio of < 1, 1, and >1, respectively (Figure ). Figure . The morphology of polymers particles and their aspect ratio. R is the radius, L is length, and h is the height.