Perfluorinated block

Dendrons attached as side chains on linear polymer chains behave different from free dendrimers and dendrons. Block copolymers, poly(3,5-bis(3,5-bis (benzyloxy)benzyloxy)-benzyl methacrylate-random-methacrylic acid)-block-poly(2-perfluorooctylethyl acrylate), possess poly(benzylether) dendrons and perfluorinated alkyl chains in their side chains (Fig. 4) [85], While an LB film of a copolymer with a medium substitution fraction of poly(benzylether) dendron side chain in poly(methacrylic acid) displays flat surface, a copolymer with high fraction of poly(benzylether) dendron side chains produces the zone texture. Dendron rich blocks are hydrophobic and oleophilic but perfluorinated blocks are solvophobic. Therefore, in this case, the solvophobicity-to-solvophilicity balance must be considered. As a result, copolymers with medium fraction of dendron are laid on solid substrate, but dendron blocks of copolymers with high fraction prefer to arrange at air side of air/ water interface and the fluorocarbon blocks are enforced to exist close to water subphase, resulting in the zone texture [86]. These situations of molecular arrangements at air/water interface are kept even after transfer on solid substrate. By contrast, when perfluorooctadecanoic acids are mixed with block copolymers with high dendron fraction, the flat monolayers are visualized as terrace [87], The monolayers are hierarchized into carboxyl, per-fluoroalkyl, and dendron layers, that is, hydrophilic, solvophobic, and oleophilic layers. In this case, perfluorooctadecanoic acids play a role for ordering of block copolymers. 

A triblock copolymer consisting of one central perfluorinated block and terminal polysulfide blocks was synthesized by the procedure shown in Fig. 35. 

Figure 35 Synthesis of block copolymer with central perfluorinated block and terminal PPS blocks. (From Ref. 125.)...

Fig. 11 Monomers used for the preparation of partially perfluorinated block copolymers...

Figure 9.9 Scanning electron micrographs of PS-b-PFDA copolymer solid dense film. Reprinted from J.A.R. Ruiz, E. Cloutet, M. Dumon, Investigation of the nanoceUnlar foaming of polystyrene in supercritical CO2 by adding a C02-philic perfluorinated block copolymer, Journal of Applied Polymer Science, 126 (1) (2012) 38-45 with permission from John Wiley and Sons.

Grignard B, VaiUant A, de Coninck J, Piens M, Jonas AM, Detrembleur C, Jerome C (2011) Electrospinning of a functional perfluorinated block copolymer as a powerfiil route for imparting superhydrophobidty and corrosion resistance to tiluminum substrates. Langmuir 27(l) 335-342. doi 10.1021/lal02808w... 

The above data prove that the polystyrene-h-polybutadiene prepolymer is quantitatively transformed into block copolymers with perfluorinated side chains. The narrow molecular-weight distribution (I) = MW/MN) of the prepolymers is maintained by the described reaction sequence. 

Fig. 20 Cryo-TEM image of isolated micelles and segmented rods made from miktoarm ABC block copolymers containing PEO, PB and perfluorinated polyether blocks (scale bar is 50 nm). A schematic representation of the stacking of block copolymer chains in segmented worms is also shown. Reprinted with permission from [284], Copyright (2004) American Association for the Advancement of Science...

M. Kotrebai, J. F. Tyson, E. Block, P. C. Uden, High performance liquid chromatography of selenium compounds utilising perfluorinated carboxylic acid ion pairing agents and inductively coupled plasma and electrospray ionisation mass spectrometric detection, J. Chromatogr. A, 866 (2000), 51-63. 

Dielectrophilic species are 1,4-diketones, certain 1,3-dienes, a,B-unsaturated isocyanates, isothiocyanates, cyanates, and thiocyanates bearing electron-withdrawing (e.g., polyfluorinated and perfluorinated) substituents the most frequently used 1,1-dinucleophiles are water, potassium sulfide, primary amines, and ammonia. From this repertoire of building blocks many combinations are possible. Tetrakis(trifluoro-methyl)furans, thiophenes, and pyrroles have been synthesized from per-fluoro-3,4-dimethylhexa-2,4-diene on addition of water, potassium sulfide, or aniline (90CC1127) (Scheme 39). 

The 1,4-dinucleophilic building blocks used most are 1,2-disubstituted ethanes of the type HXCHiCHjYH, semicarbazides, thiosemicarbazides, hydroxamic acid amides, amidrazones, and 1,2-disubstituted aromatic and heteroaromatic compounds. 1,1-Dielectrophilic building blocks preferentially used are perfluorinated carboxylic acids and their derivatives, such as acid halides, anhydrides, imidoesters, nitriles, perfluoroalkyl chlorosul-... 

The introduction of perfluorinated groups generally favors microphase separation due to the immiscibility of fluorocarbons with hydrocarbons [66]. Norbornene derivatives with perfluorinated endgroups in the side chain were prepared by Wewerka et al. [67]. Monomer XII contained a relatively long (CF2)8-chain, separated via a long spacer (11 methylene-groups) from the norbornene, whereas monomer XIII has two relatively short (CH2)2(CF2)4-side chains (Fig. 11). Homopolymers and block copolymers were synthesized with one fluorinated monomer (XII or XIII) and one non-fluorinated non-liquid crystalline monomer (NBDE or COEN) with the Schrock-type initiators 4 and 5, respectively, leading to microphase-separated block copolymers. Table 9 and Table 10 summarize the physico-chemical properties of the homopolymers and block copolymers. 

On the other hand, tertiary phosphanes react with fiuorinated alkenes to form either vinyl-phosphoranes in the case of perfluorinated alk-l-enes, or ylides when perfluorinated alk-2-enes are used as starting materials. The latter lead to useful building blocks for Wittig-type reactions. 

Further NMR analysis of chain-end groups of PPs produced with similar catalysts provided additional evidence for the prevailingly secondary propylene propagation with this class of catalyst. In fact, it was shown that the main chain-release reaction is /3-H elimination, and that propylene insertion into the Ti-H bond in the initiation step is almost exclusively primary. 1 Moreover, NMR analysis of a co-polymer of propylene with a small amount (< 2 mol%) of l-13C-ethylene, obtained with the perfluorinated catalyst (137), showed that the large majority of ethylene units in the co-polymer was present as two methylene units (see Scheme 40). This clearly indicated that ethylene units bridge blocks of propylene units with opposite regiochemistry, which is consistent with and further supports the whole mechanistic scenario.161... 

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