Wettability of biodegradable surfaces |
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Authors: | E I Vargha-Butler E Kiss C N C Lam Z Keresztes E Kálmán L Zhang A W Neumann |
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Institution: | Department of Mechanical and Industrial Engineering, University of Toronto Toronto, ON, M5S 3G8, Canada e-mail: ebutler@mie.utoronto.ca Tel.: +1-416-9781270 Fax: +1-416-9787753, CA L. E?tv?s University Department of Colloid Chemistry Budapest 112 PO Box 32, 1518 Hungary, HU Department of Surface Science and Corrosion Research Chemical Research Center Hungarian Academy of Sciences PO Box 17, 1525 Hungary, HU
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Abstract: | The study of the interfacial characteristics of biodegradable polymers/copolymers is of importance from the point of view
of both surface science and pharmaceutical/cosmetic applications. Films formed from biodegradable polymers allow systematic
wettability studies on surfaces with a wide range of copolymer (chemical) compositions. The possibility of interchanging these
drug carrier polymers, if their wetting characteristics are similar, could be beneficial to diverse applications. Low-rate
dynamic contact angles on films (solvent cast on polar substrates, i.e. on silicon wafer) of poly(lactic acid), and its copolymers
with poly(glycolic acid), (with four different copolymer ratios of 85/15, 75/25, 65/35 and 50/50) were measured by axisymmetric
drop shape analysis-profile (ADSA-P) with four liquids: water, formamide, 2,2′-thiodiethanol and 3-pyridylcarbinol. The solid
surface tensions, γsv, were calculated from the advancing contact angles, θA. The surface topography of the polymer films was investigated by atomic force microscopy (AFM). The surface composition of
the polymer layers was analyzed by X-ray photoelectron spectroscopy (XPS). The advancing contact angles were found to be independent
of the composition of the copolymers, while the receding angles, θR, did decrease with increasing ratio of the polar component poly(glycolic acid)] in the copolymers. The solid surface tensions
calculated from the advancing contact angles of the liquids for all homo- and copolymers were the same within the error limit;
the mean value being γsv=35.6 ± 0.2 mJ/m2. The surface roughness, which was obtained from AFM images, increased with increasing poly(glycolic acid) ratio, without
affecting the advancing contact angles. The constancy of γsv is attributed to the effect of the surface activity of the nonpolar segments of the polymer chains, which oriented to form
the outermost layer of the film. This was confirmed by XPS analysis.
Received: 06 November 2000 Accepted: 09 May 2001 |
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Keywords: | DL-Poly(lactic acid) DL-poly(lactic/glycolic acid) copolymers Axisymmetric drop shape analysis-profile (ADSA-P) Contact angle Surface tension |
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