Hydrophobically Modified Sulfobetaine Copolymers with Tunable Aqueous UCST through Postpolymerization Modification of Poly(pentafluorophenyl acrylate)

Polysulfobetaines, polymers carrying highly polar zwitterionic side chains, present a promising research field by virtue of their antifouling properties, hemocompatibility, and stimulus-responsive behavior. However, limited synthetic approaches exist to produce sulfobetaine copolymers comprising hydrophobic components. Postpolymerization modification of an activated ester precursor, poly(pentafluorophenyl acrylate), employing a zwitterionic amine, 3-((3-aminopropyl)dimethylammonio)propane-1-sulfonate, ADPS, is presented as a novel, one-step synthetic concept toward sulfobetaine (co)polymers. Modifications were performed in homogeneous solution using propylene carbonate as solvent with mixtures of ADPS and pentylamine, benzylamine, and dodecylamine producing a series of well-defined statistical acrylamido sulfobetaine copolymers containing hydrophobic pentyl, benzyl, or dodecylacrylamide comonomers with well-controllable molar composition as evidenced by NMR and FT-IR spectroscopy and size exclusion chromatography.This synthetic strategy was exploited to investigate, for the first time, the influence of hydrophobic modification on the upper critical solution temperature (UCST) of sulfobetaine copolymers in aqueous solution. Surprisingly, incorporation of pentyl groups was found to increase solubility over a wide composition range, whereas benzyl groups decreased solubility—an effect attributed to different entropic and enthalpic contributions of both functional groups. While UCST transitions of polysulfobetaines are typically limited to higher molar mass samples, incorporation of 0–65 mol % of benzyl groups into copolymers with molar masses of 25.5–34.5 kg/mol enabled sharp, reversible transitions from 6 to 82 °C in solutions containing up to 76 mM NaCl, as observed by optical transmittance and dynamic light scattering. Both synthesis and systematic UCST increase of sulfobetaine copolymers presented here are expected to expand the scope and applicability of these smart materials

Bildung und Struktur vernetzter temperaturstabiler polymerer Materialien

SIGLEAvailable from: http://sundoc.bibliothek.uni-halle.de/diss-online/00/00H072/habil.pdf / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekDEGerman

Investigation of lignin obtained by processing of Betula pendula with ionic liquids

Imidazolium-based ionic liquids bearing chloride, acetate, mesylate, and tosylate as anion were investigated for the treatment of birch (Betula pendula) bark to extract lignin. Although birch bark was previously extracted with methanol to remove low molecular weight organic compounds, various fatty acids and ferulic acid esters were analyzed in the lignin fraction using UPLC/ESI(â)-QTOFMS. GPC analysis shows differences in the molecular weight of the lignin samples obtained by treating bark with 1-butyl-3-methylimidazolium acetate and 1-ethyl-3-methylimidazolium tosylate. The use of 1-butyl-3-methylimidazolium chloride or 1-ethyl-3-methylimidazolium mesylate for the extraction of bark resulted in aromatic oligomers that are not fully soluble in the eluent used for GPC analysis. Therefore, the molecular weight as determined by GPC is only representative for the soluble part of these samples and not for the entire sample. Results obtained by investigation of the lignin samples extracted from bark using GPC and UPLC/ESI(â)-QTOFMS let us conclude that 1-butyl-3-methylimidazolium acetate is the most efficient ionic liquid among the solvents investigated for the extraction of lignin from bark. The high efficiency may be attributed to a high catalytic function of this ionic liquid in bound cleavage on the one hand and an active contribution of the acetate ion to trans-esterifications on the other hand

One- and two-photon photochemistry and photophysics of poly(arylenevinylene)s containing a biphenyl moiety

Photochemical and photophysical properties were investigated for poly(arylenevinylene)s containing a flexible biphenyl "hinge" unit by applying one-photon (OP) and two-photon (TP) excitation to explore excited-state properties. The poly(arylenevinylene)s were poly[(2,5-dihexyloxy-p-phenylenevinylene)-alt-(4,4'-dihexyloxy-3,3'-biph enylenevinylene)] (1), poly[(2,5-dihexyloxy-p-phenylenevinylene)-alt-(2,2'-dihexyloxy-3,3'-biph enylenevinylene)] (2), and poly[(2,5-dihexyloxy-p-phenylenevinylene)-alt-(2,2'-biphenylene-vinylene )] (3). Effective emission quantum yields and related photonic properties were evaluated on a realistic per-chromophore basis using effective conjugation lengths based on the Strickler-Berg relationship. intramolecular photocyclization was deduced to occur in the one case where the biphenyl molecular connectivity permitted the reaction, based on matrix-assisted loser desorption/ionization time-of-flight (MALDI-TOF), heteronuclear multiple-quantum coherence (HMQC)-NMR, and gel-permeation chromatography (GPC) results. The various photoprocesses could be induced by either OP or TP excitation, though the first excited singlet state is the photoactive state. The higher excitation energy 1 of the TP excited state favors indirect population of the S, state by electronic coupling between the TP and OP excited states [lambda(max)(TPE) (nm): 726; delta (GM)([9]): 1 = 229, 2 = 215, 3 = 109). Photochemical processes occurring from the lowest OP excited state (S-1) could therefore also be indirectly induced by TP excitation

Effect of arrangement of the styryl fragment on the optical properties and complexation of mono-and bis(styryl)-substituted N-methylpyridinium perchlorates containing benzo-15-crown-5 ether moieties

Using 1H NMR spectroscopy and steady-state and time-resolved electronic spectroscopy, the optical properties of mono-and bis(styryl) pyridinium perchlorates and their complexes with Mg2+, Ba 2+ cations were studied. The stability constants of the complexes were determined using spectrophotometric titration. The formation of inclusion complexes for Mg2+ and sandwich type complexes for Ba2+ results in fluorescence enhancement and increases the lifetimes of the excited states of the initial bis-styryl ligands. The variation of position of the styryl fragment in the pyridinium aromatic ring gives rise to photochromic crown ethers with different optical and photophysical characteristics and is also an easy route to bis(crown-ethers) of symmetrical and unsymmetrical structure