title: NaOH treatment of chitosan films: Impact on macromolecular structure and film properties.
abstract: In this paper, we examine the significance of treatment with NaOH on chitosan (CH) film structure to obtain biodegradable materials for several applications. In order to determine the structure of the films, an analysis based on SEM, FTIR spectroscopy and X-ray diffraction data was performed. In addition, the consequences of this treatment were evaluated by swelling index measurements and mechanical testing. As result of FTIR and X-ray analysis, three effects were identified: the deprotonation and phosphate extraction, which allowed new hydrogen bonds to form, and a higher CH deacetylation. These studies also revealed that two hydrated and anhydrous polymorphs were present in the CH-NaOH films. Moreover, the new hydrogen bond and the reduction of N-acetyl groups produced films with a more compact and disordered structure, reducing their swelling characteristics and increasing their brittleness. The introduction of a mild NaOH treatment is a versatile tool to obtain chitosan films with interesting and tunable properties.
authors.affiliation: Instituto de Física Aplicada (INFAP), Departamento de Química-Universidad Nacional de San Luis, CONICET, Chacabuco 917, CP: 5700 San Luis, Argentina.
authors.forename: E A
authors.initials: EA
authors.lastname: Takara
authors.affiliation: Instituto de Física Aplicada (INFAP), Departamento de Química-Universidad Nacional de San Luis, CONICET, Chacabuco 917, CP: 5700 San Luis, Argentina.
authors.forename: J
authors.initials: J
authors.lastname: Marchese
authors.affiliation: Instituto de Física Aplicada (INFAP), Departamento de Química-Universidad Nacional de San Luis, CONICET, Chacabuco 917, CP: 5700 San Luis, Argentina. Electronic address: aochoa@unsl.edu.ar.
authors.forename: N A
authors.initials: NA
authors.lastname: Ochoa
mesh_terms: D000107:Acetylation; D048271:Chitosan / Q000737:chemistry*; D010710:Phosphates / Q000302:isolation & purification; D011522:Protons; D012972:Sodium Hydroxide / Q000737:chemistry*; D017550:Spectroscopy, Fourier Transform Infrared; D014961:X-Ray Diffraction
chemical_list: D010710:Phosphates; D011522:Protons; D012972:Sodium Hydroxide; D048271:Chitosan
keywords: Chitosan; Deacetylation; Deprotonation; Polymorphs