Aliphatic long-chain polyesters (ALCPEs) were synthesized using the ring-opening metathesis copolymerization of ambrettolide and cis-cyclooctene followed by exhaustive hydrogenation, yielding saturated ALCPEs with methylene-toester ratios (M/E) varying from 15 to 223 and ∞ (polyethylene), of which the ester groups were pseudo randomly distributed over the backbone of the polymer. The melting temperature of these ALCPEs showed an inverse proportional trend with respect to the amount of ester groups in the polymer structure, ranging from 132.1 °C (M/E = ∞) to 91.5 °C (M/E = 15), of which the former is comparable to the melting temperature of high-density polyethylene. The crystallinity and the orthorhombic unit cell of the polymers did not significantly change with increasing M/E. Solid-state NMR was used to show the uniform partitioning of the ester groups over the crystalline and amorphous phase. Even though the lamellar thickness showed a decrease with increasing amount of ester groups, this did only partly explain the decrease in melting temperature. The main factor determining the decrease in melting temperature is the inclusion of ester groups in the crystal lattice, which causes the crystal lattice to be less stable.

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.

Xanthates ([1-(O-ethylxanthyl)ethyl]benzene (CTA1) and [1-(O-trifluoroethylxanthyl)ethyl]benzene (CTA2)) have the capacity to control the molecular weight distribution in emulsion polymerizations to produce very small nanoparticles below 20 nm. We form stable translucent polystyrene latexes using surfactant (sodium dodecyl sulfate, SDS) and a small amount of pentanol as cosurfactant. The high CTA concentration results in a greater retardation in rate until consumption of all the RAFT agent. With an increase in CTA1 the particle size decreases from 38 to 8 nm and the particle number concentration N c increases from 2 Â 10 18 to 2 Â 10 20 particles/L. Although an increase in N c should in principle lead to a faster rate of polymerization, we observe a greater retardation in rate with increasing CTA. The higher C tr,RAFT of CTA2 results in a greater initial retardation until consumption of all the RAFT agent and particle diameters lower than 5 nm and at high concentrations of CTA2 diameters that are not measurable. Kinetic simulations solving the Smith-Ewart equations explain the anomaly between R • (formed from the fragmentation of the R group from the RAFT agent) acting to nucleate micelles and terminate radicals within particles. The small and mobile R • radicals can exit particles, re-enter micelles or other particles, re-exit until they either nucleate micelles, or terminate with propagating polymeric chains. This process of exit and re-entry is similar to limit 3 in a conventional emulsion polymerization. The higher micelle nucleation rate through initiation within micelles by R • radicals results in smaller and a greater number of particles. Exit is the dominant mechanism for greater nucleation and retardation.

We report on the morphology and performance of meltdrawn poly(ω-pentadecalactone) (PPDL) fibers reinforced with a vanillic acid-based thermotropic liquid crystalline polyester (LCP). The in situ reinforced PPDL/LCP fibers developed in this work are considered to be renewable in nature, given the fact that the feedstock for both polymers can be obtained from natural resources. To prepare these fibers, the polymers were mixed in a small scale twin-screw extruder, followed by melt-drawing of the extrudate. It is demonstrated that the tensile modulus and tensile strength of the fibers increase with increasing LCP orientation and concentration. Despite the brittle nature of the pure LCP component, melt-spun PPDL/LCP fibers maintain their ductile deformation for fibers containing up to 30 wt % LCP. The improved stiffness and strength of these PPDL/LCP fibers in combination with their ductile nature ensure improved energy absorption during deformation and effectively increases their toughness compared to the pure PPDL material. A further increase of the LCP content to 40 wt % and higher results in a poor control over the blend morphology, and brittle failure of the fibers is observed after the application of 2−3% strain. Smallangle X-ray scattering data indicate that after processing transcrystallization of PPDL occurs on the surface of the oriented LCP phase. According to DSC analysis, this transcrystallization on the oriented LCP fibrils is accompanied by an increase in the crystallization temperature. These findings have been confirmed through morphological analysis using transmission electron microscopy. It is anticipated that this interfacial crystallization strengthens the PPDL/LCP interface and allows delocalization of stress during deformation.

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