Pentafluorostyrene Research Articles

Metal‐free synthesis of responsive polymers: Cloud point tuning by controlled “click” reaction

AbstractNitroxide‐mediated radical polymerization has been used for the preparation of pentafluorostyrene (PFS) homopolymers and random copolymers of PFS and oligo(ethyleneglycol) methacrylate (OEGMA8.5). The poly(pentafluorostyrene) homopolymers were reacted with thiophenol at different ratios at room temperature in the presence of triethylamine. The “clicked” polymers were characterized by 1H and 19F NMR spectroscopy and size exclusion chromatography. Moreover, the copolymerization kinetics of the PFS and OEGMA8.5 copolymers was followed, and the phase transition behavior of random copolymers with different compositions was discussed. Furthermore, copolymers of PFS and 2‐(dimethylamino) ethyl methacrylate (DMAEMA) were prepared at various mole ratios, and the copolymer with a 10:90 ratio, respectively, was soluble in water at room temperature. Turbidimetry measurements were performed for PFS and OEGMA8.5 or DMAEMA copolymers to determine their cloud points. Finally, the PFS and OEGMA8.5 copolymer with a mole ratio of 60:40 was reacted further with thiophenol to increase the hydrophobic part in the copolymer. The cloud points of the obtained copolymers could be tuned from 87 to 33 °C by using not only the controlled radical polymerization but also the “click” reaction in a controlled fashion. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 1278–1286, 2010

Clicking Pentafluorostyrene Copolymers: Synthesis, Nanoprecipitation, and Glycosylation

Glycopolymers consisting of styrene (St) and pentafluorostyrene (PFS) were synthesized by a combination of nitroxide-mediated polymerization and “click” chemistry. A series of well-defined homopolymers as well as block and random copolymers of St and PFS were obtained with different ratios by using Bloc Builder as an alkoxyamine initiator. Some copolymers showed self-assembly behavior into regular nanospheres with diameters ranging from 70 to 720 nm by applying the nanoprecipitation technique. In addition, a thiol−glycoside (2,3,4,6-tetra-O-acetyl-1-thio-β-d-glucopyranose) was reacted under ambient conditions with PFS moieties on the polymeric backbone utilizing a thiol−para fluoro “click” reaction. This nucleophilic substitution reaction was performed with high yields, and the reaction kinetic was monitored online with 19F NMR spectroscopy. Finally, the deacetylation of the protected glucose moieties was carried out to yield well-defined glycopolymers. The polymers were characterized in detail by 1H, 13C, and 19F NMR spectroscopy, size exclusion chromatography, and MALDI TOF-MS.

RAFT polymerization of activated 4‐vinylbenzoates

AbstractThe reversible addition fragmentation chain transfer (RAFT) polymerization of five active ester monomers based on 4‐vinylbenzoic acid had been investigated. Pentafluorophenyl 4‐vinylbenzoate could be polymerized under RAFT conditions yielding polymers with very good control over molecular weight and narrow molecular weight distributions. Following the synthesis of diblock copolymers consisting of polystyrene, polypentafluorostyrene, poly(4‐octylstyrene), or poly(4‐acetoxystyrene) as an inert block and poly(pentafluorophenyl 4‐vinylbenzoate) as a reactive block was successfully performed. The diblock copolymer poly(pentafluoro styrene)‐block‐poly(pentafluorophenyl 4‐vinylbenzoate) had been analyzed by 19F NMR spectroscopy in solution, demonstrating the synthetic potential of pentafluorophenyl 4‐vinylbenzoate as an extremely valuable monomer for the synthesis of highly functionalized polymeric architectures. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 1696–1705, 2009

Synthesis of Poly(glycidyl methacrylate)‐block‐Poly(pentafluorostyrene) by RAFT: Precursor to Novel Amphiphilic Poly(glyceryl methacrylate)‐block‐Poly(pentafluorostyrene)

AbstractPoly(glycidyl methacrylate) (PGMA) was synthesized by the RAFT method in the presence of 2‐cyanoprop‐2‐yl dithiobenzoate (CPDB) chain transfer agent using different [GMA]/[CPDB] molar ratios. The living radical polymerization resulted in controlled molecular weights and narrow polydispersity indices (PDI) of ≈1.1. The polymerization of pentafluorostyrene (PFS) with PGMA as the macro‐RAFT agent yielded narrow PDIs of ≤1.2 at 60 °C and ≤1.5 at 80 °C. The epoxy groups of the PGMA block were hydrolyzed to obtain novel amphiphilic copolymer, poly(glyceryl methacrylate)‐block‐poly(pentafluorostyrene) [PGMA(OH)‐b‐PPFS]. The PGMA epoxy group hydrolysis was confirmed by 1H NMR and FTIR spectroscopy. DSC investigation revealed that the PGMA‐b‐PPFS polymer was amorphous while the PGMA(OH)‐b‐PPFS displayed a high degree of crystallinity.magnified image

Well-Defined Polymers Bearing Pendent Alkene Functionalities via Selective RAFT Polymerization.

A facile synthetic approach for the preparation of well-defined (co)polymers bearing pendent alkene functionalities was established by selective reversible addition-fragmentation chain transfer (RAFT) (co)polymerization. A divinyl monomer 4-(3'-buten-1'-oxy)-2,3,5,6-tetrafluorostyrene (1) with a styrenyl group and a pendent alkene group was synthesized. Due to a very high reactivity of the styrenyl group relative to the alkene group in 1, functional fluoro(co)polymers with both well-defined structures and pendent alkene groups were prepared by RAFT polymerizations of 1 and copolymerization of 1 with pentafluorostyrene (PFS). Alkene-functionalized diblock copolymers were also prepared by RAFT copolymerization of 1 with PFS or styrene, extending from a poly(styrene-alt-maleic anhydride) macro-chain transfer agent. Hydrolysis and ammonolysis of these copolymers resulted in amphiphilic diblock fluorocopolymers with alkene-functionalized hydrophobic segments, which were shown to form internally-functionalized micelles in THF-water.

Nanoporous, Ultralow‐Dielectric‐ Constant Fluoropolymer Films from Agglomerated and Crosslinked Hollow Nanospheres of Poly(pentafluorostyrene)‐block‐Poly(divinylbenzene)

Nanoporous fluoropolymer films with dielectric constants below 2 are prepared via consecutive surface-initiated atom transfer radical polymerizations of pentafluorostyrene (PFS) and divinylbenzene (DVB) on silica nanospheres. After agglomeration of the nanospheres, crosslinking of the nanospheres by UV, and removal of the silica cores (see Figure), a nanoporous fluoropolymer film with a dielectric constant as low as 1.7 is formed.

Branched fluoropolymer-Si hybrids via surface-initiated ATRP of pentafluorostyrene on hydrogen-terminated Si(100) surfaces.

Linear, branched, and arborescent fluoropolymer-Si hybrids were prepared via surface-initiated atom transfer radical polymerization (ATRP) from the 4-vinylbenzyl chloride (VBC) inimer and ClSO(3)H-modified VBC that were immobilized on hydrogen-terminated Si(100), or Si-H, surfaces. The simple approach of UV-induced coupling of VBC with the Si-H surface provided a stable, Si-C bonded monolayer of "monofunctional" ATRP initiators (the Si-VBC surface). The aromatic rings of the Si-VBC surface were then sulfonated by ClSO(3)H to introduce sulfonyl chloride (-SO(2)Cl) groups and to give rise to a monolayer of "bifunctional" ATRP initiators. Kinetics study indicated that the chain growth of poly(pentafluorostyrene) from the functionalized silicon surfaces was consistent with a "controlled" or "living" process. The chemical composition and functionality of the silicon surface were tailored by the well-defined linear and branched fluoropolymer brushes. Atomic force microscopy images revealed that the surface-initiated ATRP of pentafluorostyrene (PFS) had proceeded uniformly on the Si-VBC surface to give rise to a dense and molecularly flat surface coverage of the linear brushes. The uniformity of surfaces with branched brushes was controlled by varying the feed ratio of the monomer and inimer (VBC in the present case). The living chain ends on the functionalized silicon surfaces were used as the macroinitiators for the synthesis of diblock copolymer brushes, consisting of the PFS and methyl methacrylate polymer blocks.

Enhancement of Electrical Stability of Polyaniline Films in Aqueous Media by Surface Graft Copolymerization with Hydrophobic Monomers

Surface modification of free-standing polyaniline (PANi) films and PANi coating on low density polyethylene (LDPE) substrates via UV-induced graft copolymerization with hydrophobic monomers was carried out. Pentafluorostyrene (PFS) and styrene were successfully graft copolymerized on the PANi surfaces, rendering them hydrophobic. The effects of UV graft copolymerization time, graft copolymerization temperature, and monomer concentration on the graft concentration were investigated. The pristine and graft-modified films were characterized using both surface and bulk analytical techniques. For the pristine PANi films, the loss of counterions from the surface region of the film occurs very rapidly in deionized water. This loss is very effectively retarded by surface graft copolymerization with PFS, hence preserving the PANi's conductivity even upon prolonged immersion in deionized water. This enhancement in the electrical stability of the PANi film was also achieved in moderately basic aqueous medium.

Vapor deposition polymerization of 4-fluorostyrene and pentafluorostyrene

Solventless deposition of thin, uniform dielectric films is of considerable interest and importance in the microelectronics industry due to environmental concerns and increasing wafer sizes. This work demonstrates a solvent-free method for atmospheric pressure chemical vapor deposition polymerization of thin films on a variety of substrates, including silicon, molybdenum, platinum and copper. Polymerization of 4-fluorostyrene (4FS) and pentafluorostyrene (PFS) is used as a model system. Depth profiling is performed using x-ray photoelectron spectroscopy, ellipsometry, and step profilometry. Film growth is found to be independent of substrate, and proceeds with activation energies of 14±1 and 15±1 kcal/mol, respectively, for 4FS and PFS deposition between 425 and 550 K. Films are shown by gel permeation chromatography to consist of low molecular weight polymer and oligimer species (between 3 and ∼140 repeat units). Atomic force microscopy analysis of films grown by this method indicates that the root mean square thickness variation along the surface is about 2.5%.

Electrical degradation of homo‐ and copolymers of styrenes and of styrene/2‐vinylnaphthalene

AbstractA variety of different styrene monomers [styrene (S), p‐fluorostyrene (p‐FS), pentafluorostyrene (PFS), p‐chlorostyrene (p‐ClS), p‐bromostyrene (p‐BrS), p‐methylstyrene (p‐MS), p‐tert‐butylstyrene (p‐tBS), p‐methoxystyrene (p‐MOS), p‐ethoxystyrene (p‐EOS), and p‐propoxystyrene (p‐POS)] have been polymerized by radical and cationic mechanisms. Copolymers of S/PFS, S/p‐ClS, S/2‐vinyl‐naphthalene (2‐VN), and S/p‐phenylstyrene (p‐PhS) were prepared by radical polymerization. All polymers were fully amorphous and transparent and exhibited only one glass transition temperature in the temperature range 77 to 141°C. Thin films of the polymers were subjected to external electrical partial discharges (PD). Typically, 20 PD experiments were conducted for each polymer and the data for the time to breakdown were adapted to the two‐parameter Weibull distribution function. The resistance towards PD of the various polymers was found to depend strongly on the monomeric structure. Complementary PD experiments on a series of narrow molecular mass polystyrenes confirmed that the minor variation in molecular mass between the different styrene polymers is of no importance for the PD resistance. The PD resistance of the homopolymers decreased in the following order: PS ≈︁ P(p‐MS) > P(p‐tBS) ≈︁ P(p‐BrS) > P(p‐POS) > P(p‐ClS) ≈︁ P(p‐MOS) > P(p‐EOS) ≈︁ P(p‐FS) > P(PFS). The time to breakdown for copolymers of S and PFS decreased monotonously with increasing PFS content. Styrene copolymers with low molar contents of 2‐ VN and p‐PhS exhibited a higher resistance towards PD than PS. The results are discussed with reference to various properties of the studied polymers, such as segmental mobility, ionization potential, resonance stabilization, and reactivity of the radicals formed.

Anionic Polymerization of 2,3,4,5,6-Pentafluorostyrene

The anionic polymerization reactivity of pentafluorostyrene (PFS) is found to be higher than that of styrene though apparent yields of polymers are relatively low. The anionic copolymerization of PFS with styrene seems to be largely controlled by the reactivities of both monomers and polymer anions as the cross-propagations are tend to take place

The reactions of hydrosilanes with trifluoropropene and pentafluorostyrene catalyzed by ruthenium, rhodium and palladium complexes

The reactions of hydrosilanes with trifluoropropene (TFP) and pentafluorostyrene (PFS) catalyzed by Ru 3(CO) 12 or RhCl(PPh 3) 3 give β-R f-vinylsilane ( 1) and/or β-R f-ethylsilane ( 2) (R f = perfluorocarbon group). The 1/2 ratio is highly dependent on the nature of hydrosilane used. The ruthenium catalyst favors the formation of 1 compared with the rhodium catalyst. Neither α-R f-vinylsilane nor α-R f-ethyl-silane was formed at all. Possible mechanisms which can accommodate characteristic features of these reactions are discussed. The hydrosilylation of TFP with dichloro-methylsilane catalyzed by PdCl 2(PhCN) 2/2PPh 3 gives the α-adduct ( 9a) exclusively, and this is transformed to the corresponding dialkoxysilanes, silane diol, oligosilane diols and cyclic oligosiloxanes.

Monomer and Polymer Grafting on Nylon Film Using Cobalt-60 Radiation

Abstract Rates of γ-ray-induced grafting on nylon 6 film were compared for pentafluorostyrene (PFS) and trifluoroethyl-methacrylate (TFEM). The logarithm of the measured rate of PFS grafting on nylon 5, plotted against reciprocal temperature, gave a straight-line Arrhenius plot between 23 and 80°C, the slope indicating an activation energy of 6.5 kcal mole. The addition of methanol accelerated the room temperature grafting of both PFS and TFEM on nylon 6, the rate passing through a maximum at 40 and 30 vol% methanol, respectively. The grafting of PFS on nylon 6 takes place most probably by a free radical mechanism. as indicated by the value of the energy of activation and by the fact that the reaction is not inhibited by water. Some work was done co extend the quantitative aspects of the theory of cocross-linking, and certain analogies with the theory of copoiymerization were demonstrated. Radiation-induced cocross-linking between a 5% solution of polyvinyl alcohol and a nylon film surface was shown, the ...