Copolymers, Including lonomers

As one of the blocks becomes polar relative to the other, the Krause theory (Section 4.7.1) predicts that phase separation will occur with shorter block lengths. Given the shorter block lengths, we are required to consider multiblock polymers of the form ABABAB in order to maintain high molecular weight and concomitant polymer properties. This chapter will consider two important classes of multiblock copolymers, the polyurethanes and the ionomers. 

Differences in polarity are carried to the extreme in the ionomers, which feature several percent of salt-containing mers distributed randomly along an otherwise nonpolar, hydrocarbon chain. Although ionomers are actually a subclass of the random copolymers, phase separation and toughening resulting from domains of high salt concentration allow classification of these materials with the block copolymers. In this case, the hard blocks are reduced to but a single mer. 

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Table 2.5 Interfacial Tensions between Polymer Melt Pairs Including Compatibilizing Agents. MAH-PP Maleic Anhydride Grafted Polypropylene SEES Hydrogenated Triblock Copolymer of Styrene and Butadiene MAH-g-SEBS Maleic Anhydride Grafted SEES PEMA-Zn Poly(ethylene-co-methacrylic Acid) lonomer Neutralized by Zinc.

The term ionomer is used to describe a variety of copolymers consisting primarily of hydrocarbon backbones to which are attached a relatively small number of ionizable branches. This family of polymers includes two groups that are ethylene-based, one based on ethylene-co-methaciylic acid copolymer and the other on sulfonated ethylene-propylene-diene terpolymer. The latter is an essentially noncrystalline mbber that is beyond the scope of the semicrystalline materials covered in this work (the synthesis, properties, and structure of sulfonate ionomers are reviewed in Ref 90). lonomers based on partially or completely... 

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