Modifying and managing the surface properties of polymers

An ongoing challenge in polymer science is the preparation of materials with bespoke surface properties which differ from that of the bulk, for example hydrophobicity, wettability, chemical resistance, adhesion or biocompatibility. We highlight here recent efforts in the design, development and application of (multi)endfunctionalized polymers as additives for the efficient modification of polymer surface properties. Aryl-ether moieties bearing up to eight functional groups have been used as initiators for the controlled polymerization of both styrene and methyl methacrylate by atom transfer radical polymerization (ATRP) and of lactide by ring opening polymerization (ROP). The resulting polymers have been used as additives to modify the surfaces of the corresponding bulk polymers. Fluorinated polymer surfaces are particularly appealing in terms of their liquid repellence, chemical inertness and low coefficient of friction. When an additive consisting of a low molecular weight polystyrene chain, end-capped with four C8F17 groups, is present in a matrix of polystyrene at levels as low as 0.1%, near polytetrafluoroethylene-like surface properties result

Recoverable surface modification using dendritically fluorocarbon-functionalized poly(methyl methacrylate)

Dendritically fluorocarbon-functionalized poly(methyl methacrylate) (PMMA) has been explored as a robust surface-modifying additive in PMMA blends. These functionalized materials, denoted FxPMMAy, where x is the number of C8F17 fluorocarbon groups per dendron connected to a PMMA chain of y kg/mol, have been synthesized by living radical polymerization. These materials adsorb efficiently to the surfaces of their blends with unfunctionalized PMMA, resulting in increased hydrophobicity and lipophobicity. Contact-angle goniometry has indicated a substantial reduction in the surface energy toward polytetrafluoroethylene- like surface properties in the case of pure F4PMMA8.6 and substantial, but incomplete fluorocarbon surface coverage at a lower FxPMMAy concentration. The partial coverage has been confirmed by Rutherford backscattering and, together with the weak dependence of the surface modification on the FxPMMAy structure, indicates incomplete equilibrium of the surface adsorption. The modified surfaces are quite durable with respect to abrasion under water but are progressively eroded when the double-wipe test is carried out with acetone. FxPMMAy, dispersed in the remaining film, acts as a reservoir of spare functional groups, from which the damaged surface may be replenished, leading to the recovery of the modified surface properties

pH responsive surfaces with nanoscale topography

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