Aliphatic polyesters
are widely studied due to their excellent
properties and low-cost production and also because, in many cases,
they are biodegradable and/or recyclable. Therefore, expanding the
range of available aliphatic polyesters is highly desirable. This
paper reports the synthesis, morphology, and crystallization kinetics
of a scarcely studied polyester, polyheptalactone (PHL). First, we
synthesized the η-heptalactone monomer by the Baeyer–Villiger
oxidation of cycloheptanone before several polyheptalactones of different
molecular weights (in the range between 2 and 12 kDa), and low dispersities
were prepared by ring-opening polymerization (ROP). The influence
of molecular weight on primary nucleation rate, spherulitic growth
rate, and overall crystallization rate was studied for the first time.
All of these rates increased with PHL molecular weight, and they approached
a plateau for the highest molecular weight samples employed here.
Single crystals of PHLs were prepared for the first time, and hexagonal-shaped
flat single crystals were obtained. The study of the crystallization
and morphology of PHL revealed strong similarities with PCL, making
PHLs very promising materials, considering their potential biodegradable
character.