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The development of highly effective bio‐lubricant coatings for arthritis treatment is extremely demanded. Herein, inspired by the efficient lubrication of articular cartilage, acrylic acid (AA) with (3‐(methacryloylamino) propyl) dimethyl (3‐sulfopropyl) ammonium hydroxide (MPDSAH) hydrogel coatings containing nanoparticles on Ti6Al4V substrate were designed and fabricated via UV grafting technology. SiO2 and SiO2 grafted with PAA polymer brushes (SiO2‐g‐PAA) were separately doped into the PAA‐PMPDSAH hydrogel. The PAA‐PMPDSAH/SiO2‐g‐PAA exhibits good tensile and compressive properties compared with PAA‐PMPDSAH/SiO2 hydrogel, with an enhancement of 183.4% in tensile modulus and 60.8% in compressive modulus. The PAA‐PMPDSAH/SiO2‐g‐PAA hydrogel coatings exhibit a low wear volume, 2.9 ± 0.16 × 106 μm3, representing a decline of 32.1% and 61.3% compared with the PAA‐PMPDSAH and PAA‐PMPDSAH/SiO2 hydrogel coatings, respectively. The antiwear performance has obviously improved. The hydrophilic PAA polymer brushes prevent the agglomeration of nanoparticles and promote homogeneously dispersion within the hydrogel. The three‐dimensional crosslinked network structure of hydrogel effectively protects the structural integrity of the polymer brushes, thereby facilitating enduring lubrication properties. This work provides a strategy for promising artificial joint lubrication in biomedical fields. [ABSTRACT FROM AUTHOR]

To achieve an efficient lubricated interface on titanium alloy (Ti6Al4V) alloy, polyelectrolyte multilayer (PEM) polymer coatings, based on poly(ethyleneimine)/poly(acrylic acid) (PEI/PAA), were fabricated on the surface of Ti6Al4V alloy substrates using the layer‐by‐layer (LbL) assembly technique. Their composition and morphology were confirmed by Fourier‐transform infrared/attenuated total reflectance (FTIR/ATR) spectroscopy, X‐ray photoelectron spectroscopy, and scanning electron microscopy. The tribological properties were investigated by a ball‐on‐disk rotating tribometer using deionized water, saline, and calf serum. The results exhibit that (PEI/PAA)*n coatings have the internal cross‐linked network and porous structure on the surface. The surface of PEI/PAA coatings‐modified Ti6Al4V shows the sufficient wettability. The polymer‐bearing interface of (PEI/PAA)*10 exhibits a low friction coefficient, 0.059, for 2 hr, and represents an 88% decline compared with bare Ti6Al4V. Moreover, the wear track on the polymer‐bearing interface is superlow. There is no obvious wear volume, which indicates effective wear resistance. The hydrated layer, the cross‐linked network structure, and the porous structure of PEM coatings are the main factors for efficient tribological properties. The multilayer PEI/PAA coating shows the potential uses of developing the lubricated‐bearing interface on Ti6Al4V alloy. [ABSTRACT FROM AUTHOR]

Natural joints have the hierarchical structure of bone and cartilage, providing excellent lubrication and load-carrying capacity. In our research, the hierarchical structure artificial joints of Poly Acrylic Acid (PAA)- Poly Acrylamide (PAAm) hydrogel coating and Ti6Al4V substrate were formed using a simple yet versatile method by mimicking the hierarchical structure of natural joints. The efficient lubrication at friction interfaces was achieved. The composition and microstructure were confirmed by Fourier-transform infrared (FTIR), X-ray photoelectron spectroscopy (XPS), Scanning electron microscopy (SEM). The hydrogel coatings were successfully prepared on the surface of Ti6Al4V substrate through the adsorption of the charged group. This hierarchical structure material exhibits the lower dynamic friction, approximately 0.085, which is much lower than bare Ti6Al4V, about 0.429. The wear on the surfaces after the tribological experiment is super-shallow and has no significant fracture area around the scratch. The PAA-PAAm hydrogel has a more uniform and compact cross-linked network porous structure, and the porous size is much smaller than PAA hydrogel. The cross-linked network porous structure is the main factor accounting for the low dynamic friction. This hierarchical structure of soft and hard improve the load-carrying ability and has the potential uses in artificial joints. [ABSTRACT FROM AUTHOR]

Osteolysis caused by wear particles from polyethylene in the artificial hip joints is a serious issue. In order to endow the low friction and wear of the bearing surface of ultra-high molecular weight polyethylene (UHMWPE) artificial joint for a longer term, hydrophilic acrylic acid (AA) was grafted on UHMWPE powders with the method of ultraviolet irradiation and then the modified powders were hot pressed. The tribological properties of modified UHMWPE sliding against CoCrMo metallic plate on reciprocating tribometer under calf serum, saline and distilled water lubrication during a long-term friction were investigated. The measurement of Fourier-transform infrared spectroscopy indicates that AA is successfully grafted on the surface of UHMWPE powders by photo-induced graft polymerization. Contact angles of UHMWPE are decreased from 83° to 35° by grafting and the surface wettability is effectively improved. The tensile strength of modified sample decreases. The friction coefficient and wear rate of UHMWPE-g-PAA under calf serum, saline and distilled water lubrication are lower than that of untreated UHMWPE. With the increase of grafting ratio, the wear rate of UHMWPE-g-PAA decreases firstly and then increases. The modified UHMWPE with grafting ratio of 3.5 % has the lowest wear rate, which is just quarter of the untreated UHMWPE. The hydrated PAA polymer brushes enclosed in the UHMWPE bulk material provide continuous lubrication during long term sliding. [ABSTRACT FROM AUTHOR]