Surface Properties and Metathesis Synthesis of Block Copolymers Including Perfluoroalkyl-Ended Polyethylenes

Abstract

Linear polyethylene with fluoroalkyl end groups has been prepared by ring-opening metathesis polymerization of cyclododecene in the presence of partially fluorinated acyclic olefins (chain transfer agents), followed by reduction of the double bonds in the backbone. Melt surface tensions (γ) were obtained for samples with one or both ends terminated by F(CF2)10 or F(CF2)4 groups at different molecular weights (MWs) of the hydrocarbon segments down to oligomeric sizes. The polyethylenes with two perfluorinated ends, i.e., PE(C10F21)2, were the most effective at lowering γ. At only 10% atomic F in the bulk, values of γ were obtained which were even lower than those for pure poly(tetrafluoroethylene). The surfaces of films of selected fluoroalkyl-terminated polymers were also characterized by advancing and receding contact angle measurements and angle dependent X-ray photoelectron spectroscopy (XPS). Advancing contact angles in hexadecane were as high as 70°, indicating a high surface concentration of perfluorinated species. Comparison with model systems indicate that much of the surface is covered by close-packed CF3 groups. XPS profiling quantified the ratio of fluorocarbon to hydrocarbon in the surface regions and also indicated a strong surface excess of oriented chain ends. The hexadecane contact angles of fluoroalkyl-ended metathesis polymers [PE(C10F21)2] decrease substantially as the molecular weight increases above ca. 40 000. In that range, the bulk concentration of chain ends becomes quite low and surface concentration of fluorocarbon chain ends at the surface is sharply reduced because of configurational entropic reasons. The surface properties of blends of a lower MW PE(C10F21)2 copolymer with a PE homopolymer were evaluated and compared to the series of pure PE(C10F21)2 copolymers where the high MW limit of the polyethylene center is approached. At similar bulk F levels in the blends and pure copolymer, the surface fluorocarbon content in the blends is significantly enhanced.

Comb-like polymer blends of poly(oxyethylene)s with CH3-terminated and CF3-terminated alkylsulfonylmethyl side chains: Effect of terminal CF3 moiety on the surface properties of the blends

“…If the side chain is well oriented, as would be expected from the NEXAFS results, then the surface of the CF 3 -10SE domain would be mostly covered by CF 3 -terminal groups and the F/C ratios obtained from the XPS results should be larger than the theoretical bulk composition of CF 3 -10SE. The F/C ratios obtained at a take-off angle of 30°are larger than those obtained at a take-off angle of 90°because the smaller angle XPS experiment provides information on the thinner regions [44][45][46]. Similar results for other polymer systems having fluorinated groups in the polymer structures were reported by others, such as a smaller increase of the F/C ratio values when the content of the fluorinated part exceeds a certain value and larger F/C ratio values in the smaller angle XPS experiments [47][48][49].…”

Comparative investigation on radical polymerization of methyl and ethyl methacrylate under multi-site phase-transfer catalytic conditions

“…because of their surface-free energy properties and water/ oil repellence, etc. [1,2]. Synthesis of acrylates polymers with controlled molecular weight distributions and low polydispersity index (PDI) is one of the key parameters to realize any kind of applications and synthesis of such acrylates polymers has attracted remarkable attention between polymer chemists and industrial community.…”

SAFT-γ force field for the simulation of molecular fluids: 8. Hetero-segmented coarse-grained models of perfluoroalkylalkanes assessed with new vapour–liquid interfacial tension data

“…The surface tension, in particular, is a key property in the recently suggested use of PFAAs as liquid ventilation excipients for nebulized drug delivery [15]. Surface tensions have, however, only been experimentally determined for some relatively long PFAAs, which are solids at ambient temperature [13][14][15][16]. A systematic study of this property as a function of the relative length of the hydrogenated and fluorinated segments is therefore very timely.…”