Maarten Krupers

Formation of rigid polyurethane foams with semi-fluorinated diblock copolymeric surfactants

Abstract Semi-fluorinated diblock copolymers were employed as surfactants in the formation of water-blown closed cell rigid polyurethane foams by the ‘tube’-foam method. These fluorosurfactants consisted of a poly(methyl methacrylate) block and a poly[(1H,1H,2H,2H-perfluoroalkyl) methacrylate] block in which the perfluoroalkyl groups were either butyl or hexyl. As references, model foams were prepared with commercially applied siloxane surfactant, inert silica, and no surfactant. Foams based on the fluorosurfactants contained many small cells while the others showed larger and markedly more irregular cells. Scanning electron microscopy (SEM) and the average foam height (AFH) were used for characterization. SEM revealed that foam cell diameters as small as 100 μm could be realized when using fluorosurfactants in contrast to very large cell sizes and irregular shapes when a commercially available siloxane surfactant, an inert inorganic solid, or no surfactant at all were used. Furthermore, relatively large AFH-values were observed when only a semi-fluorinated diblock copolymer was used. However, the combination of siloxane surfactant with a fluorine-containing surfactant resulted in unparalleled high AFHs.

Surface studies of partially fluorinated polymethacrylates: a combined XPS and LEIS analysis

Thin films of copolymers of 1,1-dihydroperfluoroheptyl methacrylate (FHMA) and methyl methacrylate (MMA) were investigated with respect to both their molecular and macroscopic surface properties. Introduction of FHMA entities in copolymer decreases the surface energy to a large extent. Angle resolved X-ray photoelectron spectroscopy (XPS) measurements show an increased average fluorine concentration in a surface layer thickness of a few nanometers, when compared to the fluorine concentration in the bulk. Static LEIS experiments, which selectively probe the outermost atomic layer, show an even stronger enrichment of fluorine atoms.

SYNTHESIS AND CHARACTERIZATION OF SEMIFLUORINATED POLYMERS VIA GROUP TRANSFER POLYMERIZATION

Abstract Group transfer polymerization (GTP) was used to prepare semifluorinated polymers based on acrylic and methacrylic monomers. In the first case, electrophilic catalyzed GTP was applied with l-methoxy-2-methyl-l-trimethylsilyloxy-1-propene (MMTP) as initiator, zinc iodide as catalyst and 1H,1H,2H,2H-perfluorooctyl acrylate as monomer. In this way it has been possible to obtain oligomers. Higher molecular weight polymers were prepared by means of the nucleophilic tetrabutylammonium benzoate as catalyst. With MMTP as initiator, 1H,1H,2H,2H-perfluoroalkyl methacrylates, F(CF 2 ) m (CH 2 ) 2 OCOC(CH 3 )=CH 2 , were polymerized to molecular weights>4.5 kg mol −1 . The polydispersity was found to depend strongly on the length of the perfuoroalkyl side chain, i.e. M w / M n decreases with increasing m .