TY - JOUR
T1 - Characterization of surface microphase structures of poly(urethane urea) biomaterials by nanoscale indentation with AFM
AU - Xu, Li Chong
AU - Soman, Pranav
AU - Runt, James
AU - Siedlecki, Christopher A.
N1 - Funding Information:
The authors would like to acknowledge Dr. Aashiish Agnihotri for valuable technical discussions and Ms. Ruth A. Haldeman for technical help with the microtome. This research was supported by the Dorothy Foehr Huck and J. Lloyd Huck Institutes of the Life Sciences and by a grant from the Pennsylvania Department of Health. The Pennsylvania Department of Health specifically disclaims responsibility for any analyses, interpretations or conclusions.
PY - 2007/4
Y1 - 2007/4
N2 - Atomic force microscopy utilizing both tapping mode and force mode imaging is used to visualize the separated microphases in poly(urethane urea) films under ambient and aqueous conditions. The topography of the PUU surface changed upon hydration with the formation of nanometer-sized features on the surface. The surface becomes enriched in hard domains with hydration time and this enrichment is irreversible after dehydration. Force mode measurements were used to quantify mechanical properties as both indentation and modulus measurements. Analysis of the modulus during indentation reveals the three-dimensional nature of the structures, with the surface being covered by a 2-20-nm-thick soft segment overlayer under ambient conditions, while hydration leads to the loss of this overlayer. The force measurements also reveal the presence of regions having modulus values between those of the hard and soft phases and located spatially near the interface between the hard and soft domains. However, such regions with intermediate modulus were only rarely seen following hydration. Calculation of the Young's modulus from the compression data shows that hydration increases the modulus of the PUU surface by both enrichment of the amount of hard domain present and increasing the modulus of the individual hard and soft phases themselves. Direct visualization of the distribution of these different domains on the surface by nanoscale measurements provides an important path to characterizing the relationships between the surface properties of these materials and subsequent performance in biomedical applications.
AB - Atomic force microscopy utilizing both tapping mode and force mode imaging is used to visualize the separated microphases in poly(urethane urea) films under ambient and aqueous conditions. The topography of the PUU surface changed upon hydration with the formation of nanometer-sized features on the surface. The surface becomes enriched in hard domains with hydration time and this enrichment is irreversible after dehydration. Force mode measurements were used to quantify mechanical properties as both indentation and modulus measurements. Analysis of the modulus during indentation reveals the three-dimensional nature of the structures, with the surface being covered by a 2-20-nm-thick soft segment overlayer under ambient conditions, while hydration leads to the loss of this overlayer. The force measurements also reveal the presence of regions having modulus values between those of the hard and soft phases and located spatially near the interface between the hard and soft domains. However, such regions with intermediate modulus were only rarely seen following hydration. Calculation of the Young's modulus from the compression data shows that hydration increases the modulus of the PUU surface by both enrichment of the amount of hard domain present and increasing the modulus of the individual hard and soft phases themselves. Direct visualization of the distribution of these different domains on the surface by nanoscale measurements provides an important path to characterizing the relationships between the surface properties of these materials and subsequent performance in biomedical applications.
KW - Atomic force microscopy
KW - Nanoscale indentation
KW - Poly(urethane urea)
KW - Polyurethane
KW - Surface characterization
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U2 - 10.1163/156856207780425013
DO - 10.1163/156856207780425013
M3 - Article
C2 - 17540113
AN - SCOPUS:34347403496
SN - 0920-5063
VL - 18
SP - 353
EP - 368
JO - Journal of Biomaterials Science, Polymer Edition
JF - Journal of Biomaterials Science, Polymer Edition
IS - 4
ER -