Effect of molecular weight on the physical properties of poly(ethylene brassylate) homopolymers.

Poly(ethylene brassylate) (PEB) is a biodegradable polyester that nowadays is of particular interest owing to its poly(ε-caprolactone)-like properties (with a T g at −30 °C and a T m at 70 °C) and the low-cost of its monomer. However, it is not simple to achieve high molar masses with conventional catalysts. In this work, high molar mass PEBs, characterized by SEC-MALS, were successfully synthesized using triphenyl bismuth (Ph 3 Bi) as catalyst. Then, with the aim of evaluating the impact of the molecular weight on the physical properties, several PEBs ranging from 27 to 247 kg mol −1 were prepared. It was demonstrated that above a M w of 90 Kg mol −1 , PEB behaved in a constant manner. PEBs with lower molecular weight (<46 Kg mol −1 ) showed lower values of T g (~(−35 °C)) and presented a melting peak that was split into three or four different peaks while their crystallites started to melt earlier (at ~30 °C). In addition, these PEBs were more sensitive to thermal degradation (two additional stages of degradation were observed) and, what is more important, were found to be prone to brittle fracture. As the M w rose, the PEB samples became more ductile and those PEBs with a molecular weight above 90 Kg mol −1 possessed deformation at break values higher than 800%, secant modulus in the 296–324 range and ultimate tensile strength of >20 MPa. [ABSTRACT FROM AUTHOR]