Ladder Polymers of Intrinsic Microporosity ( PIM s)

This chapter focuses on the description of the synthesis of polymers of intrinsic microporosity (PIMs) and their application in material chemistry. One of the most important characteristics of this relatively novel class of ladder polymers is their high porosity, which is induced by the rigidity and contortion of the monomers that prevents the efficient packing of the molecular chains in the solid state. This structural arrangement generates a large amount of internal free volume (IFV) that can be exploited for very important applications. The concept of microporosity, the type of monomer, and the assessment of the porosity are discussed in the first part of the chapter. The second part focuses on the description of different types of ladder PIMs, starting from polybenzodioxanes and PIM-1, which is considered the archetypal member of this class. The modification of the main monomers that constitute the category of polybenzodioxanes is thoroughly discussed, including the formation of co-polymers and postpolymerization modifications of the backbone. A second polymerization pathway that forms successful PIMs involves the formation of Tröger's base core (TB-PIMs) and is discussed in the third part. Also in this case, modification of the main monomers and alteration of the polymeric structures that compose this class of PIMs are meticulously analyzed. The last part of the chapter describes targeted applications that make PIMs very interesting microporous materials. Particular focus is given to their use as membranes for gas separation, followed by gas storage, catalysis and electrochemistry, pervaporation and nanofiltration, and finishing with the use of PIMs as ion exchange membranes.