Block Copolymers of “PE-Like” Poly(pentadecalactone) and Poly(l-lactide): Synthesis, Properties, and Compatibilization of Polyethylene/Poly(l-lactide) Blends

Abstract

Block copolymers consisting of a polyethylene block and a polar polymer block are interesting structures for the compatibilization of polyethylene/polar polymer blends or polyethylene-based composites. Since the synthesis of polyethylene-based block copolymers is an elaborate process, diblock copolymers consisting of “polyethylene-like” poly­(pentadecalactone) (PPDL) and poly­(l-lactide) (PLLA) were synthesized using a one-pot, sequential-feed ring-opening polymerization of pentadecalactone (PDL) and l-lactide (LLA). The peculiar activity of the used aluminum salen catalysts yielded a block copolymer consisting of two blocks with both a high dispersity, as a result of intrablock transesterification. Interestingly, interblock transesterification was effectively suppressed. The obtained poly­(PDL-block-LLA) of various block lengths showed coincidental crystallization of the two blocks with an associated microphase-separated morphology, in which PLLA spheres with a high dispersity are distributed within the PPDL matrix. The complex morphologies is believed to arise from the presence of a whole range of block sizes as a consequence of the large dispersity of both blocks. The application of these block copolymers as compatibilizers for high density polyethylene (HDPE)/PLLA blends led to a clear change in blend morphology and a steep decrease in particle size of the dispersed phase. Furthermore, addition of the block copolymers to blends of linear low density polyethylene (LLDPE) and PLLA led to a significant increase in adhesion between the two phases. For both HDPE/PLLA and LLDPE/PLLA blends, the compatibilization efficiency of the poly­(PDL-block-LLA) increased when the length of the PPDL block was increased. The presented results clearly show that PPDL can function as a substituent for various types of polyethylene, which opens up a new method for compatibilizing polyethylene with polar polymers using easy attainable “PE-like” block copolymers.

Tuning the thermal properties of poly(ethylene)‐like poly(esters) by copolymerization of ε‐caprolactone with macrolactones, in the presence of a pyridylamidozinc(II) complex

“…In comparison to the step‐growth polycondensation processes, the chain‐growth ROP of large lactones enables the achievement of a high degree of control over molecular weight and their dispersity, end‐group fidelity, regio‐ and stereoselectivity, and architecture . More importantly, the ROP should enable the copolymerization of different monomers and allow to modulate carefully composition and topology (block, cyclic, star, and so forth) thus opening the scenario to different and programmed polymeric architectures . A further added value is the “green” origin of macrolactones, being derived from renewable resources, mostly isolated from plant oil, often used in the fragrance industries.…”

Copolymacrolactones Grafted with l-Glutamic Acid: Synthesis, Structure, and Nanocarrier Properties

“…The possibilities of PDL as monomer has been widely explored along the last two decades for the synthesis of aliphatic polyesters and copolyesters with high potential as biodegradable and bioresorbable medical materials, whereas such interest for Gl has been moderate. Copolymerization by ROP of PDL with other lactones constitutes the major approach applied for the design of highly hydrophobic polyesters with adjusted thermal and mechanical properties [8][9][10][11][12][13][14][15][16]. A substantial limitation of the polyesters made of PDL is, however, their lack of chemical functionality other than that associated to chain ends.…”

Recent progress in block copolymer crystallization

“…Often, materials are incompatible as blends, but block copolymers are used as compatibilizers to broaden the scope of possible blend compositions. Pepels et al . studied BCPs consisting of a PE‐like block [poly(pentadecalactone), PPDL] and polar block for the compatibilization of PE/polar polymer blends or PE based composites.…”

“…SEM images of the morphology of cryogenically fractured PLLA/HDPE blends with PPDL‐ b ‐PLLA compatibilizer added at (A‐C) 0% and (D‐F) 5%. (Reproduced from with permission from the American Chemical Society)…”