. (2011) 'Electrospinning superhydrophobic bers using surface segregating end-functionalized polymer additives. ', Macromolecules., 44 (16). pp. 6461-6470. Further information on publisher's website:http://dx.doi.org/10.1021/ma200852zPublisher's copyright statement:This document is the Accepted Manuscript version of a Published Work that appeared in nal form in Macromolecules, copyright c 2011 American Chemical Society after peer review and technical editing by the publisher. To access the nal edited and published work see http://dx.doi.org/10.1021/ma200852z. Additional information:Use policyThe full-text may be used and/or reproduced, and given to third parties in any format or medium, without prior permission or charge, for personal research or study, educational, or not-for-prot purposes provided that:• a full bibliographic reference is made to the original source • a link is made to the metadata record in DRO • the full-text is not changed in any way The full-text must not be sold in any format or medium without the formal permission of the copyright holders.Please consult the full DRO policy for further details. RECEIVED DATE (to be automatically inserted after your manuscript is accepted if requiredaccording to the journal that you are submitting your paper to) † Chemistry Department, Faculty of Science, University of Malaya, 50603 Kuala Lumpur, Malaysia.ABSTRACT: We describe here a facile route for the in situ modification of the surface properties of fibres produced by electrospinning polystyrene containing small quantities of compatible polymer additives, end functionalized with 1-3 fluoroalkyl groups. Such additives undergo spontaneous surface segregation during the electrospinning process resulting in fibres with low surface energy, fluorine rich, superhydrophobic surfaces. Surface properties were analyzed using static contact angle measurements (with water as the contact fluid) and X-ray photoelectron spectroscopy. We report the effect of a number of parameters on the surface properties of the resulting polystyrene fibres including the molecular weight and concentration of functionalized additive, the number of fluoroalkyl groups, the effect of annealing and spinning solvent. The majority of the fibres were successfully produced using THF as the spinning 2 solvent and fibres with a contact angle of approximately 150 degrees were attainable. However, preliminary investigations using a blend of polystyrene and 4% by weight of such an additive, endfunctionalized with 3 C 8 F 17 group in a mixed solvent of DMF/THF (3:1 v/v) resulted in a mat of fibres with a superhydrophobic surface and a contact angle of 158 degrees.

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We have prepared and characterized a series of multi-fluorocarbon 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. 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 multi-fluorocarbon 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 selfstratified 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 co-crystallization with the matrix when the blended films are allowed to cool below the melting point.2

A new approach to promoting and controlling polymer surface functionalization with acidic or basic polar functional groups is demonstrated and evaluated. Blended polymer films were annealed under pH-buffered conditions, and polar end-functional groups were found to promote surface segregation of the functional polymers. Surface segregation of carboxylic acid (COOH)-functionalized polystyrene increases dramatically with increasing pH from 1.9 to 9.4, whereas the opposite behavior is seen for amine (NH2)-functionalized polystyrene. Neutron reflectometry and nuclear reaction analysis were used to obtain surface excess values for the functional polymers. Subsequent SCFT analysis of the composition versus depth profiles indicates that the affinity of each functional group for the polymer surface changes by about 3k(B)T over this pH range.