Radicals drive complex, ‘life-like’ behaviors

It exceedingly difficult to define what complex means, or to develop an absolute metric for its measure in a chemical system. But there are chemical phenomena that are driven by radicals that bear striking resemblances to living systems. The most striking example is perhaps the Belousov-Zhabotinsky (BZ) Reaction. It creates oscillatory patterns in 3D mixtures, but when reduced to a nearly flat 2D mixture, the same system generates very complex moving fronts and self-interactive wave patterns. It bears a superficial comparison to microbial growth patterns or a predator-prey relationship. Here is an example: 

Another compelling, more recent example is the RAFT (Reversible Addition Fragment chain Transfer) system combined with Polymerization Induced Self Assembly (PISA), which is also built upon the BZ system as described in a paper by Hou et al., and which is described here: