Petr S. Vlasov

Design and synthesis of new anionic “polymeric ionic liquids” with high charge delocalization

Three novel ionic monomers having highly delocalized anions and electrochemically stable mobile cations, namely, 1-butyl-1-methylpyrrolidinium 1-[3-(methacryloyloxy)propylsulfonyl]-1-(trifluoromethane-sulfonyl)imide, 1-butyl-1-methylpyrrolidinium 1,1-dicyano-1-[(3-(methacryloyloxy)propylsulfonyl)]methanide and 1-butyl-1-methylpyrrolidinium 1-cyano-1-[(3-(methacryloyloxy)propylsulfonyl)]imide were synthesized and characterized. The structure of these monomers was designed to be a mimic of the most highly conductive bis(trifluoromethylsulfonyl)imide, tricyanomethanide and dicyanamide anions. By radical polymerization procedure a series of new anionic “polymeric ionic liquids” (PILs) were prepared. The solubility of these linear PILs, thermal stability, glass transition temperatures, molar masses and ionic conductivities were estimated. An advantage of the novel PILs was demonstrated by the comparison of their ionic conductivity at 25 °C (2.0 × 10−8 ÷ 1.6 × 10−7 S cm−1) with the unmodified poly(1-ethyl-1-methylpyrrolidinium 3-(methacryloyloxy)propane-1-sulfonate) analog. The increase in ionic conductivity is as high as three orders of magnitude and was found to depend on the size of the attached anion. The new ionic monomers were subsequently copolymerized with poly(ethylene glycol) dimethacrylate and poly(ethylene glycol) methyl ether methacrylate. The investigation of the copolymers properties revealed further improvement of the conductivity in approximately two orders of magnitude and the achievement of σ = 4.8 ÷ 6.8 × 10−6 S cm−1) at 40 °C.

Turning into poly(ionic liquid)s as a tool for polyimide modification: synthesis, characterization and CO2 separation properties

In an attempt to improve the mechanical and thermal properties of poly(ionic liquid)s (PILs), a new synthetic method for the modification of polyimides is reported here for the first time. The proposed methodology consists of the transformation of polyimides into their ionic forms via subsequent N-alkylation and quaternization of benzimidazole or quinuclidine moieties. Finally, an ion exchange reaction was also carried out in order to prepare polymers bearing the bis(trifluoromethylsulfonyl)imide anion. The elaboration of optimal conditions for the reactions afforded the preparation of high molecular weight (Mn = 2.2–9.7 × 104) cationic polyelectrolytes with a degree of quaternization as high as 96%. Among the unique features of these new PILs are the preservation of excellent mechanical and thermal properties inherent in polyimides, the adjustable surface wettability with variable water contact angles from 70.5 to 94.3°, the enhanced hydrolytic stability (up to 9 h in boiling water) and improved gas transport properties (CO2 permeability up to 28.9 Barrer for a neat film and 85.0 Barrer for a filled membrane at 20 °C and 100 kPa).

Synthesis and properties of polymeric analogs of ionic liquids

A number of methacrylate ionic monomers with different structures and mobilities of ionic centers were synthesized. The free-radical polymerization of these monomers in solution affords high-molecular-mass (M sD = 0.5 to 2.5 × 106) thermally stable (T dec > 170°C) polyelectrolytes or cationic or anionic “polymeric ionic liquids.” The conductivities of polycation- and polyanion-derived coatings are (7.4 × 10−10)−(7.6 × 10−7) and (4.9 × 10−10)-(1.6 × 10−7) S/cm (25°C), respectively. As exemplified by poly(1-[3-(methacryloyloxy)propyl]-3-methylimidazolium bis[(trifluoromethanesulfonyl)imide]), the molecular mass and glasstransition temperature of the polymer affect the ionic conductivity of the film coating. The transition from linear polyelectrolytes to crosslinked systems based on ionic monomers and poly(ethylene glycol dimethacrylate) 750 leads to the formation of elastic films featuring satisfactory strength, reduced glass-transition temperatures (−8 to +15°C), and increased ionic conductivity (up to 3.2 × 10−6 S/cm (25°C)).

Ionic semi-interpenetrating networks as a new approach for highly conductive and stretchable polymer materials

The synthesis and characterization of ionically conductive polymer films with high stretchability and good elasticity based on ionic semi-interpenetrating polymer networks (semi-IPNs) are discussed. Such innovative semi-IPN materials were prepared by radical copolymerization of an ionic monomer, namely, (N-[2-(2-(2-(methacryloyloxy)ethoxy)ethoxy)ethyl]-N-methylpyrrolidinium bis(fluorosulfonyl)imide) with poly(ethylene glycol)(di)methacrylates in the presence of the dissolved nitrile butadiene rubber, ionic liquid and lithium salt, using a simple one-step process. The suggested approach allows for simultaneous imparting of high ionic conductivity (1.3 × 10−4 S cm−1 at 25 °C) and excellent mechanical properties (tensile strength up to 80 kPa, elongation up to 60%) to a single polymer material. Ionic semi-IPNs, possessing unusual “Emmentaler cheese” like structure, exhibit a wide electrochemical stability window (4.9 V) and acceptable time-stable interfacial properties in contact with metallic lithium. Preliminary battery tests have shown that Li/LiFePO4 solid-state cells are capable to deliver a 77 mA h g−1 average specific capacity at 40 °C during 75 charge/discharge cycles.

Novel thermosensitive telechelic PEGs with antioxidant activity: synthesis, molecular properties and conformational behaviour

We report on the synthesis and solution properties of novel tailor-made polymer conjugates, which are highly compelling for biomedical applications due to their antioxidant activity and the potential to fine-tune their thermosensitive properties. These conjugates consist of polyethylene glycol (PEG) polymers containing antioxidant moieties, namely 3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate or 2-benzamido-3-(3,5-di-tert-butyl-4-hydroxyphenyl)acrylate, as end groups that differ in activity and hydrophobicity. It was shown that all of the synthesized conjugates have low critical solution temperatures (LCSTs) characteristic of type II polymers on a phase diagram. By simply varying the PEG molecular weight, the solution properties, including the LCST value, could be easily tuned across a broad temperature range of 20–90 °C, providing an ideal method for the creation of thermosensitive polymers. It was also established that the LCST value and the polymer conjugate conformation depend on the antioxidant structure. From dynamic light scattering and small-angle X-ray scattering data, we were able to construct a complete sequence diagram of the conformational phase behaviour of the polymers with increasing temperature. It was observed that the conjugate conformation changes are the result of water shifting from a thermodynamically favourable solvent to an unfavourable one. This process then leads to compaction of the conjugate, followed by its aggregation.

Supramolecular ionic networks with superior thermal and transport properties based on novel delocalized di-anionic compounds

Supramolecular ionic networks based on highly delocalized dianions having (trifluoromethane-sulfonyl)imide, (propylsulfonyl)methanide and (cyano-propylsulfonyl)imide groups were developed and their physical properties were examined in detail. Most of the synthesized compounds were semi-crystalline possessing Tm values close to 100 °C; however, amorphous networks were also obtained using aromatic asymmetric dianions. Rheological measurements in temperature sweep tests at a constant frequency confirmed two different behaviors: a fast melting close to the Tm for semi-crystalline materials and a thermoreversible network for liquid transition for the amorphous supramolecular ionic networks. It was found that the amorphous ionic networks showed significantly higher ionic conductivity (10−3 S cm−1 at 100 °C) than the crystalline ionic networks (10−6 S cm−1) and previously reported amorphous citrate ionic networks (10−5 S cm−1). The supramolecular ionic networks containing hydrophobic (trifluoromethanesulfonyl)imide groups demonstrated improved water stability and higher thermal stability than the previously synthesized carboxylate ones. Noticeably, the obtained amorphous supramolecular ionic networks combine not only high ionic conductivity and thermal stability, but also self-healing properties into the same material.

Solid-state electrolytes based on ionic network polymers

Interpenetrating and semiinterpenetrating polymer networks are synthesized with the use of cationic and anionic ionic monomers: N�(3�(methacryloyloxy)propyl)� Nmethylpyrrolidinium bis(trifluoromethane� sulfonyl)imide, N�(2�(2�(2�(methacryloyloxy)ethoxy)ethoxy)ethyl)� Nmethylpyrrolidinium bis(fluorosulfo� nyl)imide, and (NbutylNmethylpyrrolidinium 1�(3�(methacryloyloxy)propylsulfonyl) (trifluoromethanesulfo� nyl) imide. Their ionic conductivities, electrochemical stabilities, heat resistances, thermal stabilities, and mechanical properties and the swelling of the films in ionic liquid/lithium salt mixtures were studied. The copoly� merization of N�(2�(2�(2�(methacryloyloxy)ethoxy)ethoxy)ethyl)� Nmethylpyrrolidinium bis(fluorosulfo� nyl)imide and poly(ethylene glycol dimethacrylate) and poly(ethylene glycol methacrylate) in the presence of butadiene-acrylonitrile rubber and a solution of Li(CF3SO2)2N in N�(methoxymethyl)� Nmethylpyrrolidinium bis(fluorosulfonyl)imide yielded a solidstate electrolyte wi th a set of properties optimum among the studied films: an ionic conductivity of 1.3 × 10 -4 S/cm (25°C), a tensile strength of 80 kPa, and an elongation at break of 60%.

Molecular Properties of the Copolymers of N,N-Diallyl-N,N-Dimethylammonium Chloride and Maleic Acid

The hydrodynamic and conformational properties of molecules of poly(N,N-diallyl-N,N-dimethylammonium chloride) and N,N-diallyl-N,N-dimethylammonium chloride-maleic acid copolymers of different compositions in solutions with various ionic-strength and pH values, as well as of the polyelectrolyte complex based on the copolymer with dodecyl sulfate anions in chloroform, are studied. For poly(N,N-diallyl-N,N-dimethylammonium chloride) molecules in a 1 M NaCl solution, the Kuhn segment length and the hydrodynamic diameter of the chain are estimated as A = 3.9 nm and d = 0.48 nm, respectively. In acidic solutions with pH 3.5, the copolymers demonstrate behavior typical for polyelectrolytes. In an alkaline solution with pH 13, when 1 M NaCl is added to the solution of the copolymer containing 29 mol % maleic acid units, there is an antipolyelectrolyte effect that manifests itself as an increase in the intrinsic viscosity of the copolymer and in the hydrodynamic radius of its molecules. It is found that an increase in the fraction of maleic acid units in the copolymer from 12 to 42 mol % brings about a reduction in the equilibrium rigidity of its macromolecules from 4.1 to 2.2 nm. The equilibrium rigidity of polyelectrolyte-complex molecules is higher than that of initial copolymer molecules owing to steric interactions arising between the aliphatic chains of dodecyl sulfate anions. In an electric field, the molecules of the complex are oriented owing to the induced dipole moment resulting from the displacement of dodecyl sulfate anions along the chain contour.

Hyperbranched pyridylphenylene polymers based on the first-generation dendrimer as a multifunctional monomer

An A6 + B2 approach was applied for the first time to synthesize novel hyperbranched pyridylphenylene polymers by Diels–Alder cyclocondensation reaction. For this, the first-generation pyridylphenylene dendrimer with six ethynyl functionalities (A6) was used as a branching core for the molecule growth. The phenyl-substituted bis(cyclopentadienone)s (B2) of different structures were used as co-monomer in the reaction. A careful choice of reaction conditions allowed us to obtain high molecular weight polymers without undesirable gelation. The molecular weight of the polymers varied in the range of 10 800–80 100 with a polydispersity degree of 1.69 to 4.07 according to SEC analysis. The 1H and inverse-gated decoupling 13C NMR combined with heteronuclear single quantum correlation and heteronuclear multiple bond correlation measurements were used to estimate the branching degree of the polymers synthesized.

MACROMOLECULAR ANTIOXIDANTS BASED ON POLYSACCHARIDES AND 2,6-DIISOBORNYL-4-METHYLPHENOL DERIVATIVES

New macromolecular antioxidants that were conjugates of dextran or hydroxyethylated starch with functionalized derivatives synthesized from 2,6-diisobornyl-4-methylphenol were prepared. Their antiradical activity compared with derivatives of 2,6-di-tert-butyl-4-methylphenol was studied in a model reaction with 2,2-diphenyl-1-picrylhydrazyl. The studied conjugates exhibited greater activity than sterically hindered phenols not bonded to a polymer chain. The synthesized isobornyl derivatives were more active than previously studied tert-butyl analogs.