Tactic and stereoselective polymerizations are traditionally catalyzed by metal-organic complexes. Topochemical polymerization provides an additional choice. In addition, by changing the alignment of the monomer within the crystal, the tacticity/stereochemistry of the polymer product could be easily controlled. An intuitive example is shown in the figure. In topochemical polymerization of 1,3-diene carboxylic acid derivatives, polymers with four different configurations can be prepared. Their structural relationships with the monomer packing are also shown in the figure.