The poly(L-lactide) (PLLA) is a biocompatible polymer widely studied because is hard. How hard? Well, hard enough to think of it as a possible bone replacement.
Recently, I was involved in a collaboration to study how PLLA crystallizes when confined into thin films: a bidimensional polymer layer, thin enough to be comparable to the size of a single PLLA crystal. An Atomic Force Microscopy image of the PLLA confined into this geometry is shown below. The shape of the crystal, resembling a tree leaf, is called a dendritic one, and it relates to the way the polymer chains arrange with respecto to the surface. In this case, this is a “flat-on” organization, which is the expected one for these ultrathin systems (more on the subject here).
The whole results on this work have been published in Soft Matter Journal, and can be accessed here (paywall).