Synthesis and Characterization of Polylactides with Different Branched Architectures

Star-shaped and comb-like poly(L-Lactide)s (PLA) are produced by employing multifunctional initiators, and hyper-branched structure is prepared using a cyclic co-monomer with hydroxyl group. FTIR, size exclusion chromatography, and HNMR techniques are employed to characterize the synthesized polymers, validating the formation of desired structures with chain lengths above the critical length for entanglement. After characterization of the synthesized polymers, the effect of branching on PLA properties is investigated by comparing the crystallization and rheological behavior of branched PLAs to those of a linear commercial grade. Differential scanning calorimetry and optical microscopy observations reveal a remark-able improvement in PLA crystallization due to the nucleation role of branching points. Moreover, synthesized polylactides exhibit strain hardening behavior during elongational viscosity measurements by a sentmanat extension rheometer platform. Significant improvements in crystallization and elongational rheology behavior of the synthesized polymers support the achievement of branched polymer structures. (C) 2015 Wiley Periodicals, Inc.