Polymers with Aromatic Hydrocarbon Backbone

Polymers with aromatic hydrocarbon backbone include polymers containing in their chain aromatic hydrocarbon rings, or alternating aromatic rings and aliphatic carbon groups. Thermosetting phenolic resins can be included in this class. 

The single-monomer route (eq. (5)) is preferred, as it gives more para-linked repeat units and therefore a straighter backbone than the two-monomer route. Other sulfone-based polymers can be similarly produced from sulfonyl halides with aromatic hydrocarbons. The key step in these polymerizations is the formation of the carbon-sulfur bond. High polymers are achievable via this synthesis route although the resulting polymers are not always completely linear. 

Hydrocarbon polymers with aromatic rings in the backbone have high melting temperatures due to the extended chain conformations that approach those of liquid crystals. For example, poly(p-xylene) based on the repeat unit... 

Nearly all of the polymers produced by step-growth polymerization contain heteroatoms and/or aromatic rings in the backbone. One exception is polymers produced from acyclic diene metathesis (ADMET) polymerization.22 Hydrocarbon polymers with carbon-carbon double bonds are readily produced using ADMET polymerization techniques. Polyesters, polycarbonates, polyamides, and polyurethanes can be produced from aliphatic monomers with appropriate functional groups (Fig. 1.1). In these aliphatic polymers, the concentration of the linking groups (ester, carbonate, amide, or urethane) in the backbone greatly influences the physical properties. 

Phosphonated polymers with fluorinated backbones have been obtained by reacting fluorinated poly(atylene ether)s with a H-phosphonate diester in the presence of Pd(PPh3)4 (Scheme 13.3d). Using fluorinated aromatic polymers as the backbone can be expected to improve the dimensional stability of the membranes compared to aromatic polymers with hydrocarbon backbones because of the increased hydrophobicity induced by the presence of the fluorocarbon. The phosphonated polymers with fluorinated aromatic backbones reached a conductivity of 6 mS cm at 95% RH at 80 °C and 2.6 mS cm in water at room temperature, which was below that of Nafion 117. 

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