Development and relative comparison of polypyrrole-calcium phosphate composite coatings with differential concentration of chlorophyll functionalized polymer particle achieved through pulsed electro deposition

• Published in: Surface & coatings technology 2019-04, Vol.363, p.221-235
• Main Authors: Chakraborty, Rajib, Manna, Jhimli Sarkar, Saha, Partha
• Format: Article
• Language: English
• Subjects: Apatite; Aqueous electrolytes; Bio functional coating; Biocompatibility; Biomedical materials; Bond energy; Calcium; Calcium phosphates; Ceramic bonding; Ceramic coatings; Chlorophyll; Chlorophyll functionalized polypyrrole; Comparative studies; Corrosion resistance; Crystal growth; Deposition; Electrochemical corrosion; Electrolytic cells; Honeycomb structures; Hydroxyapatite; Magnesium; Nano-polymer-ceramic composite coating; Polymer matrix composites; Polymerization; Polymers; Polypyrroles; Protective coatings; Proteins; Pulsed electro-deposition
• ISSN: 0257-8972; 1879-3347
• DOI: 10.1016/j.surfcoat.2019.02.025

Polypyrrole-calcium orthophosphate-hydroxyapatite functional composite coating is synthesized over the metallic implant surfaces through pulsed electrochemical deposition. Polypyrrole particles are photo-functionalized with the help of chlorophyll during polymerization for their dispersion in the aqueous electrolyte bath. In-situ formation of calcium phosphate phases along with co-deposition of chlorophyll functionalized-polypyrrole particles lead to formation of a ceramic-polymer composite coating. Concentration of chlorophyll molecule in the solution greatly affects the polymerization reaction and subsequent incorporation of functionalized polymer in final coating. Thus, various types of composites structures are developed based on differential amount of polypyrrole presence through varying concentration of chlorophyll, for a detailed comparative study. The polymer chain length and formation bond energy significantly influence the in-situ formation mechanism along with crystal growth direction and rate of formation of various calcium phosphate phases. At low concentration, polymer reinforced hydroxyapatite flakes are formed. High concentration of chlorophyll lead to formation of both the individual polymer phase along with polymer reinforced calcium phosphate phase. While at very high concentration, a polymer layer is formed reinforced with nanocrystalline hydroxyapatite particles. Reinforced coating exhibits three fold higher electrochemical corrosion resistances as compared to bare hydroxyapatite coating. All the coating surfaces display superior osteoconduction capabilities through the formation of stoichiometric hydroxyapatite spherical particles within 7 to 14 days of contact. During osteoconduction, a unique nano porous honeycomb structure over the formed apatite surface enriched with sodium and magnesium ions are formed which would help to ensure higher protein absorption along with a better bonding of cells over the coating surface. Thus, this ceramic-polymer composite developed for the first time through chlorophyll functionalization, can act as one of the potential materials for improvement of both bio-functionalities and corrosion resistance of metallic implant surfaces. •Synthesis and functionalization of polypyrrole in aqueous medium through chlorophyll•Electrochemical co-deposition of calcium phosphate-PPy reinforced composite.•Amount of polymer presence influences surface characteristics and osteoconduction.•Composite exhibits improved you