Direct Route to Colloidal UHMWPE by Including LLDPE in Solution during Homogeneous Polymerization of Ethylene

The usual aggregation and precipitation driven by crystallization of nascent PE during homogeneous polymerization of ultra-high molecular weight polyethylene (UHMWPE) is inhibited by including linear low-density polyethylene (LLDPE) in the catalyst solution prior to addition of ethylene monomer. Co-crystallization of newly formed PE and dissolved LLDPE creates a polymer brush on the fold surfaces of the nascent crystallites. Consequently, aggregation is inhibited by steric stabilization. Scanning electron microscopy (SEM) images show that individual lamellae (approximately 10-20 nm thick) typically have lateral dimensions of 0.5 μm × 3.5 μm and form "bowtie" shaped stacks that are approximately 200-500 nm thick. This simple method for stabilizing nascent crystals against precipitation is enabling fundamental studies of their metastable "disentangled" state and may open scalable routes to compounding UHMWPE.