Influence of diverse MgCl_x/R’_nCl_mAl_y(OR)_z activators/supports in tailoring of entangled state of UHMWPE

Heterogeneous MgCl_x/Et_nAl_y(2-ethyl-1-hexoxide)_z dual activator/support, together with bis[N-(3‑tert-butylsalicylidene)pentafluoroanilinato] titanium(IV) dichloride complex, has demonstrated its potential in the synthesis of low entangled UHMWPE under controlled polymerization conditions. The work was corroborated with the solid-state processed uniaxial tapes having ultimate mechanical properties, which were found at par with the polymer synthesized using homogeneous catalysis with the edge to govern nascent polymer morphology. The activator/support is tuned depending on the combination of aluminum-alkyls and alcohols employed in the synthesis. Herein, a series of alcohols (2-ethyl-1-hexanol, 3-methyl-1-butanol, n-butanol, n-pentanol, n-octanol, cyclohexanol, and benzyl alcohol) and phenol are employed in the formation of the MgCl₂/ROH adduct followed by reaction with different aluminum-alkyls (TEA, DEAC, TiBAl, and TMA) to form a diverse class of MgCl_x/R’_nCl_mAl_y(OR)_z activators/supports. The diverse activators are employed in the synthesis of low-entangled UHMWPE, the resultant polymers display controlled fine particle morphology without any reactor fouling/wall sheeting. The characteristics of the synthesized polymers are studied using SEM, DSC, melt rheology, high-temperature NMR, and FT-IR. All the synthesized polymers are found to be linear UHMWPE having a reduced number of entanglement, making them suitable (with exceptions) for solvent-free solid-state processing to produce high-strength and modulus tapes. An attempt is made to illustrate the varying entanglement state by correlating the nascent UHMWPE characteristics (such as particle morphology, particulate density, single crystal lamellae structures, storage modulus build-up, and advanced thermal analysis) with the solid-state processing. The resultant catalytic systems of the type Cat. 1/MgCl_x/R’_nCl_mAl_y(OR)_z are found to form unique nano dual activator/support, crucial for the supporting of a small number of active sites, thus reducing chain overlap during the polymer synthesis. The developed catalytic systems allow tailoring the molecular weight from 3 to 43 million g/mol and Ð from 3.3 to 38 of the synthesized polymers. The mechanical properties are found to be ∼ 4 N/tex of specific strength and > 200 N/tex of specific modulus.