The complex mixture of polymers coating the spore that protects the spore from dessication and UV radiation is:

Sporopollenin

Explanation:

Sporopollenin is a biological polymer that is highly cross linked and made up of oxygen, hydrogen and carbon. It is referred to a chemically inert biopolymer because of its toughness and stability in rocks that have been in existence for over 500 million years. In other words, sporopollenin is chemically stable.

It is an important component of the outer layer or coating of pollen grains and plant spores. This protects spores from UV radiation and dessication.