Aliphatic polyester block polymers as compostable tough plastics and resilient elastomers*

Aliphatic polyester block polymers can be prepared from straightforward sequential ring-opening transesterification polymerizations of cyclic esters. Poly(lactide) is an attractive hard block for these materials because of its ready availability, renewable origins, relatively high glass transition temperature, ability to crystallize in the isotactic form, and the capacity to be industrially composted. We have focused our work on the development of suitable low glass transition temperature, non-crystalline, soft midblocks that can also be synthesized from renewable resources and that are compostable. To that end, we have focused our attention on poly(4-methyl caprolactone). The monomer, 4-methyl caprolactone, can be prepared from cresols, which in turn can come from renewable lignin, in an economical manner and the corresponding polymer is industrially compostable. In this presentation I will discuss our recent efforts to prepare block polymers from these hard and soft components and focus on architecture control (e.g., triblocks, star blocks, graft blocks, sterocomplexes), the influence of tacticity in the poly(lactide) segments, the ultimate properties of these materials as tough plastics or resilient elastomers, and the environmental fate in soils and compost.