title: Surface modification of polyethylene with multi-end-functional polyethylene additives.
abstract: We have prepared and characterized a series of multifluorocarbon end-functional polyethylene additives, which when blended with polyethylene matrices increase surface hydrophobicity and lipophobicity. Water contact angles of >112° were observed on spin-cast blended film surfaces containing less than 1% fluorocarbon in the bulk, compared to ~98° in the absence of any additive. Crystallinity in these films gives rise to surface roughness that is an order of magnitude greater than is typical for amorphous spin-cast films but is too little to give rise to superhydrophobicity. X-ray photoelectron spectroscopy (XPS) confirms the enrichment of the multifluorocarbon additives at the air surface by up to 80 times the bulk concentration. Ion beam analysis was used to quantify the surface excess of the additives as a function of composition, functionality, and molecular weight of either blend component. In some cases, an excess of the additives was also found at the substrate interface, indicating phase separation into self-stratified layers. The combination of neutron reflectometry and ion beam analysis allowed the surface excess to be quantified above and below the melting point of the blended films. In these films, where the melting temperatures of the additive and matrix components are relatively similar (within 15 °C), the surface excess is almost independent of whether the blended film is semicrystalline or molten, suggesting that the additive undergoes cocrystallization with the matrix when the blended films are allowed to cool below the melting point.
authors.affiliation: Department of Chemistry, Science Site, Durham Centre for Soft Matter, Durham, UK.
authors.forename: Sarah J
authors.initials: SJ
authors.lastname: Hardman
authors.forename: Lian R
authors.initials: LR
authors.lastname: Hutchings
authors.forename: Nigel
authors.initials: N
authors.lastname: Clarke
authors.forename: Solomon M
authors.initials: SM
authors.lastname: Kimani
authors.forename: Laura L E
authors.initials: LL
authors.lastname: Mears
authors.forename: Emily F
authors.initials: EF
authors.lastname: Smith
authors.forename: John R P
authors.initials: JR
authors.lastname: Webster
authors.forename: Richard L
authors.initials: RL
authors.lastname: Thompson