A new class of thermoplastic elastomers based on polypivalolactone graft systems

Ring‐opening graft polymerization of pivalolactone, initiated by carboxylate anion which is randomly located on suitable polymeric substrates, affords high quality thermoplastic elastomers. When processed from the melt, poly(privalolactone) segments readily crystallize into discontinuous domains which serve as reinforcing network tiepoints and melt at 120–225°C according to the average degree of polymerization (P̄n = 4–90) of the graft segments. Transmission electron microscopy shows domain size to be 5–100 nm. Poly([ethylene‐co‐propylene‐co‐1,4‐hexadiene]‐g‐pivalolactone) (from carboxylated base polymer) and poly([ethyl acrylate]‐g‐pivalolactone) were evaluated in detail and have physical properties similar to conventionally cured and reinforced base polymers. The effects of structural variables on morphology and properties are discussed.