polyisophthalates

Polyisophthalates are a class of polymers derived from isophthalic acid. Isophthalic acid is an aromatic dicarboxylic acid with the formula C6H4(CO2H)2, where the carboxyl groups are in the meta (1,3) positions on the benzene ring. When polymerized with diols or other difunctional monomers, polyisophthalates are formed. The specific properties of polyisophthalates depend heavily on the co-monomers used in the polymerization process.

These polymers are often employed as polyester resins, particularly in applications where enhanced thermal stability, chemical resistance, and mechanical strength are desired compared to their terephthalate counterparts. For example, incorporating isophthalate units into polyethylene terephthalate (PET) can create modified PET (PETG or PETT) with improved clarity and toughness. Polyisophthalates can also be found in coatings, adhesives, and fibers. Their aromatic structure contributes to rigidity and a higher glass transition temperature. The meta linkage of isophthalic acid tends to disrupt chain packing compared to the para linkage in terephthalic acid, which can lead to increased solubility and a lower melting point in some cases, offering processing advantages.