Synthesis and Characterization of Self-Associative Perfluoroalkyl-End-Capped Polystyrene

Abstract

ABSTRACT:Polystyrene bearing a perfluoroalkyl group at one polymer chain end was synthesized by a "living" radical polymerization of styrene in the presence of 4-perfluoro(n-tetradecanoylamino)-2,2,6,6-tetramethylpiperidinyl-1-oxy. The "living" polymerization was evidenced by the fact that chain extension occurred upon addition of styrene to a prepolymer at an elevated temperature, i.e., the number-average molecular weight increased linearly with monomer conversion while the molecular weight distribution remained narrow independent of the conversion. The presence of the perfluoroalkyl group in the polymer was confirmed from IR and NMR ( 1 H and 13 C) spectra. A preliminary study of the associative behavior of perfluoroalkyl-end-capped polystyrene, using light scattering, spin-lattice relaxation time in 19 F NMR, and fluorescence probe techniques, indicated that self-association of terminal perfluoroalkyl groups occurred in benzene at polymer concentrations higher than ca. 30 g L −1 when weight-average molecular weight is as low as 5500.KEY WORDS 2,2,6,6-Tetramethylpiperidinyl-1-oxy (TEMPO) / Controlled Radical Polymerization / Self-Association / Perfluoroalkyl Group / Diblock copolymers form micelle-like aggregates as a result of the association of a less soluble block when the copolymers are dissolved in a solvent that is good for only one of the blocks. 1-4 For example, amphiphilic diblock copolymers form micelles in aqueous media, hydrophobic blocks constituting a core and the hydrophilic blocks forming a corona. In analogy with amphiphilic diblock copolymers, watersoluble polymers possessing a large hydrophobic substituent at one chain end form micelle-like aggregates in water. This type of end-modified polymers has been synthesized by free-radical polymerization of hydrophilic monomers using hydrophobically modified azo initiators. For example, Winnik et al. [5][6][7] synthesized poly(N-isopropylacrylamide) (PNIPAM) substituted with a dioctadecyl group at its chain end and revealed that the hydrophobe-end-modified PNI-PAM formed multipolymer micelles at temperatures below its lower critical solution temperature in water. In our previous work, we synthesized poly(sodium 2-(acrylamido)-2-methylpropanesulfonate) end-capped with a cholesterol moiety and showed that the polymer underwent multipolymeric micellization in water. 8 A complexity of free radical polymerization initiated by hydrophobically modified azo initiators is that chain termination occurs via recombination or disproportionation, yielding polymers with hydrophobic groups at † To whom correspondence should be addressed.

Fluorine polymer probes for magnetic resonance imaging: quo vadis?

“…Fluorinated copolymers are typically synthesized analogously to their nonfluorinated counterparts, i.e., by (controlled pseudo living) radical, cationic, anionic or coordination polymerization. The most commonly used controlled radical polymerization techniques involve nitroxide-mediated polymerization [66, 67], atom transfer polymerization (ATRP) [68, 69] and reversible addition fragmentation chain transfer (RAFT) polymerization [70, 71]. It is worth mentioning that if multiple fluorine atoms are in close proximity to the polymerizable moiety, then they may dramatically reduce the electron density of the moiety, greatly influencing its reactivity to polymerization.…”

Self-assembly in the solutions of poly(methyl methacrylates) end-capped with fluorophenyl groups

“…Interest to end-functionalized polymers increased in the last years due to their practical significance [11]. Oligomers end-capped with fluoroalkyl groups were shown to behave as surfactants in organic solvents, and in the super-critical CO 2 [12][13][14].…”

Novel Fluoroalkyl End-Capped Amphiphilic Diblock Copolymers with pH/Temperature Response and Self-Assembly Behavior

“…Moreover, these F-groups can easily aggregate with rather than repel one another in aqueous solution to give rise to self-assembled molecular aggregates with controlled nanometer size . Various fluoroalkyl end-capped polymers have been synthesized by a number of polymerization techniques, including the use of fluoroalkanoyl peroxide initiators, ,− esterification with perfluoroacyl chloride, , telomerizations with fluorinated mercaptan and fluorinated alky iodides, nitroxide-mediated polymerization (NMP), − atom transfer radical polymerization (ATRP), − and reversible addition fragmentation chain transfer (RAFT) polymerization. , …”

“…6 Various fluoroalkyl end-capped polymers have been synthesized by a number of polymerization techniques, 7 including the use of fluoroalkanoyl peroxide initiators, 5,[8][9][10][11] esterification with per-fluoroacyl chloride, 12,13 telomerizations with fluorinated mercaptan and fluorinated alky iodides, 14 nitroxide-mediated polymerization (NMP), [15][16][17] atom transfer radical polymerization (ATRP), [18][19][20] and reversible addition fragmentation chain transfer (RAFT) polymerization. 21,22 From the viewpoint of structures, several recent studies have been devoted mainly to the combination of end-capped fluoroalkyl groups with hydrophobic polymers 15,[19][20][21][22] or amphiphilic block copolymers. 18,23,24 Furthermore, some block copolymers consisted of a poly(fluoroalkyl methacrylate) moiety (or F-alkyl in the side chain), and common hydrocarbon segments have also been reported.…”