# Sulfonation Treatment of Polyether-Ether-Ketone for Dental Implant Uses
## 4 Discussion  
Acetone rinsing was the cleaning method used in this study in order to remove the sulfuric acid's residues in the porous network structure without affecting the surface shape or the chemical composition of the sulfonated PEEK since acetone does not dissolve sulfonated PEEK [19]. Since PEEK is a crystalline polymer with a melt transition temperature of approximately 343 degrees Celsius and a semicrystalline thermoplastic polymer with a glass transition temperature of about 143 degrees Celsius [18], the hydrothermal treatment at a temperature of 120 degrees Celsius can only remove the sulfuric acid that is left behind. This indicates that neither its physical structure nor its chemical composition can be altered by the hydrothermal treatment that is being applied. The residual sulfuric acid on the sulfonated PEEK seeped from the pores into the alkaline solution, and after immersion in the NaOH solution, the solutions were neutralized by each other; the pores' structure was not impacted in the slightest. After being sulfonated, PEEK should be treated with one of the following three procedures: washing with acetone, immersing in NaOH, or heating with heat. Any of these three processes is recommended as an effective PEEK process treatment since it may eliminate any residual sulfuric acid. As the time of immersion extended, the porous structure increasingly became more evident as well as more sophisticated. At first, the porous structure on the surface of the sulfonated PEEK was just superficial and straightforward, but as the time increased, it gradually became more complex. After undergoing sulfonation in concentrated H\({}_{2}\)SO\({}_{4}\), the surface of the sulfonated PEEK exhibited a three-dimensional nano- to micro-porous network. Additionally, sulfonated functional groups were discovered on the surface of the sulfonated PEEK. When the sample was removed from the sulfuric acid, there was a trace amount of H\({}_{2}\)SO\({}_{4}\) that was left on the surface of the porous material. On the other hand, if the duration of the immersion was prolonged for an excessive amount of time, the porous structure that was produced on the surface layer had a tendency to be damaged and destroyed. According to the findings of this research project, as the amount of time spent sulfonating increased, the structure of the porous network became more apparent. In a previous work, [20] found that increasing the immersion duration resulted in the improved formation of nanostructures and porous materials. The findings of this investigation are in agreement with the findings of previous investigations. The findings demonstrated that the sulfur element was incorporated into the polymer chains of PEEK through the process of sulfonation. In terms of hydrophilicity, the untreated PEEK's water contact angle was found to range from 70 to 90 degrees in previous research [20], which is comparable to our findings. According to the findings of earlier research conducted by [21], the PEEK's water contact angle was measured as 78.6, whereas the sulfonated PEEK's water contact angle was measured as 67.2. Although hydrophilic SO\({}_{3}\)H groups were added to the surface, the findings of this study suggest that the morphology of the surface with a nanostructured network and 3D porosity plays a crucial role in diminishing the hydrophilicity of the surface. This was the conclusion drawn from this study. According to [5; 20], the bioactivity and osseointegration of a bone implant interface are significantly improved when the bone implant interface possesses hydrophilicity and nano-topography. The sulfonation of PEEK results in a considerable reduction in the material's surface hydrophilicity; yet, the 3D nano- to micro-porous structure that is created as a result of sulfonation is thought to be favorable for increasing the bioactivity. However, contrary findings were found in other research [22]. These findings concerned an increase in the contact angle following sulfonation.