ISSN:
0887-6266
Keywords:
low-density polyethylene
;
surface modification of polymers
;
scanning force microscopy
;
self-assembled monolayer of thiols
;
chemical force microscopy
;
Physics
;
Polymer and Materials Science
Source:
Wiley InterScience Backfile Collection 1832-2000
Topics:
Chemistry and Pharmacology
,
Physics
Notes:
In this article, we present the results of a study on the surface properties of chromic acid-oxidized low-density polyethylene (LDPE) by scanning force microscopy (SFM) and contact angle measurements. LDPE films were surface modified by a chromic acid treatment with subsequent annealing in argon and reconstruction in boiling water as described by Rasmussen, Stedronsky, and Whitesides [J. Am. Chem. Soc., 99, 4736 (1977)]. The LDPE oxidation in chromic acid was monitored in situ by contact mode SFM. Initially stacks of lamellae became exposed, and at later stages a granular morphology was observed. By tapping mode SFM, the sample roughness was shown to increase during the first 10 min of oxidation from initially ca. 20 nm to ca. 50 nm. Gold-coated SFM probes (tips) functionalized with self-assembled monolayers were used to determine the pull-off force characteristics in ethanol. Variations in the contact area between SFM tips and polymer surfaces that exposed sharp crystalline features were shown to obscure the results of pull-off force measurements. However, on annealed and subsequently reconstructed samples with lower roughness, the results of force measurements correlated well with the measured contact angles. Over the range of surface energies studied, the normalized pull-off force between carboxylic acid-modified tips and these smooth samples was shown to depend approximately linearly on the cosine of the contact angle. © 1998 John Wiley & Sons, Inc. J. Polym. Sci. B Polym. Phys. 36: 2483-2492, 1998
Additional Material:
10 Ill.
Type of Medium:
Electronic Resource
