The Outermost Atomic Layer of Thin Films of Fluorinated Polymethacrylates

Abstract

In this paper, we investigate the surface properties of a series of copolymers of perfluoroalkyl methacrylate (CH2 = C(CH3)COOCH2CnF(2n + 1), n = 1, 6, or 10) and methyl methacrylate (MMA) and of blends of perfluorooctyl-end-capped poly(methyl methacrylate) (PMMA) and pure PMMA. The introduction of perfluoroalkyl groups significantly lowers the polymer surface energy as determined by the acid-base approach. X-ray photoelectron spectroscopy (XPS) confirms a higher fluorine concentration in the surface region (the outer 3.8 nm) as compared to in the bulk. The fluorine density in the outermost atomic layer is quantitatively determined by low-energy ion scattering (LEIS). A linear relationship is found between the fluorine density in the outermost atomic layer and the surface energy of the partially fluorinated polymethacrylates, irrespective of the length of the perfluoroalkyl chain. This linearity confirms Langmuir's "principle of independent surface action". Deviation from this linear relationship exists for both highly and sparsely fluorinated polymethacrylates and can be ascribed to the local (surface) ordering of the fluorinated tails and MMA units, respectively. This study may offer one further step toward a deeper understanding of the correlations between macroscopic surface properties and microscopic surface chemical composition.

Mechanical and thermal properties of perfluoroalkyl ethyl methacrylate–methyl methacrylate statistical copolymers synthesized in supercritical carbon dioxide

“…It is well-known that the molecular weights of the perfluoro acrylic copolymers synthesized in CO 2 medium were higher than the copolymers obtained in polar organic solvents [6,10,39]. DeSimone et al reported that the copolymer molecular weight of FOA with MMA in scCO 2 were more than 270,000 g/mol [10], whereas other researchers reported that the solution copolymerization of perfluoro alkyl methacrylate with MMA in MEK [39] and in BuOAc [6] resulted in much lower molecular weights which were in the range of 20,000-25,000 g/mol.…”

“…In general, fluoropolymers are categorized as main-chain and side-chain fluoropolymers, and most of the side-chain fluoropolymers are synthesized from the polymerization reaction of the fluorinated methacrylate monomers [4]. The introduction of the pendant fluorinated groups through the acrylic monomers which have perfluoroalkyl side groups, decreases the surface tension of the obtained copolymer films [5,6]. Fluoro methacrylate (FMA) copolymers have been used increasingly in a wide range of applications including surface coatings for textile, paper and leather industries, biomaterials, microelectronics and antifouling [7,8].…”

“…Another important parameter affecting the Y mod of polymers is the free volume of the copolymer. This property also alters the T g of the copolymer [6,9,[18][19][20][21]. Choi et al, synthesized MMA-trifluoro Poly(methyl methacrylate-ran-perfluoroalkyl ethyl methacrylate) copolymers having varying perfluoroalkyl ethyl methacrylate ester (Zonyl-TM) contents were synthesized in supercritical CO 2 .…”

Molecular basis for solvent dependent morphologies observed on electrosprayed surfaces

“…However, for surface applications focusing on hydrophobicity, copolymers of fluorinated and conventional monomers can be effectively employed since the fluorinated groups segregate at the solid-air interface to decrease surface energy. 1,[7][8][9] In addition, self-assembly of fluorinated block copolymers in various environments has been successfully utilized to fabricate nano-structures having a wide range of morphologies which have found applications in emerging technologies such as nano-optics, nano-electronics and nanobiotechnology. 10,11 Low surface energy of the fluorinated polymers is commonly utilized in the area of superhydrophobicity, a subject that became popular when the naturally micro-textured surface of the non-wettable lotus leaves was discovered.…”

Surface segregation of fluorinated moieties on poly(methyl methacrylate-ran-2-perfluorooctylethyl methacrylate) films during film formation: Entropic or enthalpic influences

“…It was reported that the chain shapes or the conformations of polymers in solutions could affect the structures and properties of the polymers in bulk [22,23]. The influence of the preparation methods on the surface properties of fluorinated polymers has been reported in several publications [21,[24][25][26][27][28][29] and it was found that various surface structures can be obtained by controlling film-formation conditions such as the solvent species and preparation methods. When methyl methacrylate (MMA) and 2-perfluorooctylethyl methacrylate (FMA) block copolymer (PMMA-b-PFMA) film was prepared from its micelle solution with PMMA block as micelle corona and PFMA block as 0021-9797/$ -see front matter Ó 2010 Elsevier Inc. All rights reserved.…”