Functional and smart surfaces by segregation of hyperbranched polymers from polyolefin matrices
(2005)
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- Authors
- Supervisors
- Bailly, Christian
- Abstract
- There is an ever-growing interest for polymers with controlled surface characteristics. Surface properties are determined by the composition and morphology of the polymer extreme surface. Apart from well-known chemical and physical post-treatments, one promising way to modify surface properties consists in adding small amounts of a hyperbranched polymer (HBP) to a polymeric matrix. Indeed, the hyperbranched polymer tends to localize at the matrix surface. The exact mechanism responsible for the HBP surface segregation, surface organization and mobility were however poorly understood at the onset of this thesis. Amphiphilic hyperbranched polymers possessing a polar core and apolar alkyl end-groups were first prepared. This was achieved by esterification by stearic acid of the HBP hydroxyl end-groups. The modified HBP polymers were next blended in polyethylene. Through XPS and ToF-SIMS analyses performed on extruded films containing a few percent HBP, we observed a significant surface enrichment by the HBP polymers. Moreover AFM imaging showed a surface morphology composed of HBP islands dispersed through the polyethylene matrix. Apart from the clear role played by the viscosity difference between the hyperbranched additive and the polyethylene matrix during processing, washing/annealing experiments as well as surface energy measurements (virgin polyethylene, hydroxyl-ended and amphiphilic HBPs) allowed us to evidence an enthalpic dominance for surface segregation. Dynamic contact angle analysis revealed a surface able to reorganize depending on the contacting medium. The film surface behaved in a more hydrophilic manner after conditioning in hot water and the initial hydrophobicity was recovered by subsequent heating in air. The presence of a HBP-rich surface layer, the HBP surface reorientation ability and the "molecular container" property of HBP's were finally combined to favour the uptake of metallic species (Ag, ) at the surface of polyethylene films, this approach being motivated by the idea to impart antibacterial properties to the polymer.
- Affiliations
Citations
Terreur, V. (2005). Functional and smart surfaces by segregation of hyperbranched polymers from polyolefin matrices. https://hdl.handle.net/2078.5/124167