title: Experimental investigation of interfaces in hydroxyapatite/polyacrylic acid/polycaprolactone composites using photoacoustic FTIR spectroscopy.
abstract: Molecular interactions in hydroxyapatite (HAP) polymer composites have been studied using photoacoustic spectroscopy. HAP is mineralized by wet precipitation under two conditions: first is in the absence of polyacrylic acid (PAAc) (ex-situ HAP) and second in the presence of PAAc (in-situ HAP). Porous and solid composites of ex-situ and in-situ HAP with polycaprolactone (PCL) have also been made to evaluate their applicability as bone scaffolds. Photoacoustic Fourier transform infrared (PA-FTIR) spectroscopy studies indicate that both in-situ and ex-situ HAP have HPO4 (2-) in their structure, which leads to Ca2+ deficiency. During crystallization of in-situ HAP, PAAc dissociates to form carboxylate ions, which binds to calcium ions and act as suitable site for nucleation for HAP crystallization. PA-FTIR spectra of porous and solid composites indicate that porous composites adsorb more water, which is hydrogen bonded with carbonyl of PCL. Mechanical tests on solid samples indicate that ex-situ HAP/PCL composites have higher elastic modulus than in-situ HAP/PCL composites. However, in case of porous composites, in-situ HAP/PCL composites are found to have higher elastic modulus. In-situ HAP is chemically and structurally different from ex-situ HAP. This modified HAP causes variation in microstructure of porous composite and hence alteration of its load transfer mechanisms and hence mechanical properties.
authors.affiliation: Department of Civil Engineering and Construction Management, North Dakota State University, Fargo, North Dakota 58105, USA.
authors.forename: Devendra
authors.initials: D
authors.lastname: Verma
authors.forename: Kalpana
authors.initials: K
authors.lastname: Katti
authors.forename: Dinesh
authors.initials: D
authors.lastname: Katti
mesh_terms: D000180:Acrylic Resins / Q000737:chemistry*; D001672:Biocompatible Materials / Q000737:chemistry* / Q000378:metabolism; D002118:Calcium / Q000378:metabolism; D003460:Crystallization; D003764:Dental Materials / Q000737:chemistry; D004548:Elasticity; D006882:Hydroxyapatites / Q000737:chemistry*; D008422:Materials Testing; D015394:Molecular Structure; D010710:Phosphates / Q000737:chemistry / Q000378:metabolism; D011091:Polyesters / Q000737:chemistry*; D011108:Polymers / Q000737:chemistry*; D017550:Spectroscopy, Fourier Transform Infrared / Q000379:methods*; D013057:Spectrum Analysis / Q000379:methods*; D013499:Surface Properties; D023822:Tissue Engineering
chemical_list: D000180:Acrylic Resins; D001672:Biocompatible Materials; D003764:Dental Materials; D006882:Hydroxyapatites; D010710:Phosphates; D011091:Polyesters; D011108:Polymers; C016240:polycaprolactone; C006903:carbopol 940; D002118:Calcium