Multiblock Thermoplastic Elastomers Derived from Biodiesel, Poly(propylene glycol), and L-Lactide

A series of [poly(L-lactide)-poly(dimer acid methyl ester-alt-poly(propylene glycol)) poly(L-lactide)](n) (PLLA-PDP-PLLA)(n) multiblock copolymers was synthesized in a three-step procedure: PLLA-PDP-PLLA (LDPL) triblock copolymers were synthesized using ring-opening polymerization of L-lactide with PDP macroinitiators, which was prepared via step-growth melt polycondensation based on biodiesel and macro-diol, followed by chain extension of the LDPL triblock with 4,4'-methylenebis(phenyl isocyanate). Molecular characterization revealed that the synthetic procedures yielded the desired triblock and multiblock copolymers (f(PLLA) = 0.22-0.27). The relationship between thermal behavior and morphology indicated microphase separation into two domains in both the triblocks and multiblocks. Compared to previously reported triblocks with a high molar mass and PLLA hard blocks with inaccessible order-disorder transition temperature (T-ODT) values, the multiblock architectures in this study were found to become disordered at much lower temperatures (T-ODT = 82-128 degrees C). To prepare (LDPL)(n) multiblocks, coupling low-molar-mass LDPL triblocks without free-standing thin films led to dramatically enhanced tensile properties. The self-adhesive performance of the pressure-sensitive adhesive (PSA) system including the multiblocks was evaluated, showing a peel strength of 3.1 N cm(-1), a probe tack of 1.9 N, and static shear strength of >50 000 min, which are values comparable to those of current PSAs. These biodiesel-based thermoplastic elastomers hold promise for sustainability and high value-added economy.