Initial deposition of calcium phosphate ceramic on polyethylene and polydimethylsiloxane by rf magnetron sputtering deposition: the interface chemistry

Calcium phosphate (CaP) coatings are well known for their bioactive nature. CaP coated polymeric materials can be used as implant material. For this, a strong adhesion between the coating and substrate is necessary. Because the chemical structure of the interface plays an important role in the coating adhesion, we studied the interface between CaP and the polymers polyethylene (PE) and polydimethylsiloxane (PDMS/silicone rubber). Both untreated and plasma pretreated polymers were used. On PE, a low Ca/P ratio nearby the interface and a high amount of C–O bonds were found on both untreated and plasma pretreated PE. This is the result of phosphate–like groups that are able to bind to the carbon of the PE. PDMS reacts towards the plasma pretreatment by losing CH3 side groups. Compared to PE, a low amount of C–O bonds is found nearby the interface. Besides, a low Ca/P ratio is found nearby the interface. This is the result of phosphate groups that connect to Si atoms of the PDMS, thereby replacing the CH3 side groups. The bombardment by negatively charged oxygen ions that are accelerated from the target during the deposition process makes the chemical interaction between the coating and the substrates possible.