Regulation Mechanism of Special Functional Groups Contained in Polymer Molecular Chains on the Tribological Properties of Modified Ti6Al4V

Abstract

Polymer coatings can effectively improve the surface tribological properties of human implant materials, thereby increasing their service life. In this study, poly(vinylsulfonic acid, sodium salt) (PVS), poly(acrylic acid) (PAA) and poly(vinylphosphonic acid) (PVPA) were used to modify Ti6Al4V surfaces. Experimental analyses were combined with molecular simulation to explore the regulation mechanism of special functional groups contained in polymer molecular chains on the tribological properties of modified surfaces. In addition, the bearing capacities and velocity dependence of different polymer modified surfaces during friction were also explored. The PVS coating, due to physical adsorption, can have an anti-friction effect under NaCl solution lubrication, but is not durable under long-term or repeated usage. Both PAA and PVPA molecular chains can form chemical bonds with Ti6Al4V. Phosphate acid groups can firmly bind to the substrate, and the adsorption of salt ions and water molecules can form a hydrated layer on the PVPA coating surface, achieving ultra-low friction and wear. The adsorption of salt ions would aggravate the surface wear of the PAA-modified Ti6Al4V due to the unfirm binding of carboxyl groups to the substrate, resulting in a high friction coefficient. This study can provide effective guidance for the design of modified polymer coatings on metals.

All-atom molecular dynamics simulations of polymer and polyelectrolyte brushes

“…While there is a lot of flexibility in synthesizing PE brushes for a specific application, it remains a challenge to predict its exact behavior in each setting due to a large number of microscopic and environmental variables that regulate such behavior. These variables include the molecular weight of the polymer chains, polydispersity, 41 chemical composition of the chains, solvent type, 42 solvent–monomer interactions, 43 screening counterion valence, 44 counterion structure, the position of the functional group in the chain (side chain or main chain 45,46 ), pH of the solution, 47 temperature of the system, concentration and type of the added salt (in addition to the screening counterions), etc. Moreover, additional complexities arise due to the highly non-linear inter-dependence of these different variables.…”