30 article(s) from Ritter, Helmut
- Full Research Paper
- Published 14 Nov 2016
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Figure 1: Structures of used monomers and the time-conversion plot of the corresponding free-radical polymeri...
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Scheme 1: Stereospecific propagation of chiral MLA illustrating the triade formation [15].
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Figure 2: Plot of log Pn versus log [In] of the polymerization of MLA with different mol % AIBN.
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Scheme 2: Postulated mechanism of the self-initiation of MLA.
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Figure 3: DFT-calculated C–C binding length (yellow) of (A) MLA and (B) the corresponding radical.
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Figure 4: IR spectra of (A) MLA and of (B) poly(MLA) prepared by the self-initiated polymerization at 70 °C.
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Figure 5: Conversion plot of the polymerization of MLA in 1,4-dioxane and DMF (cMLA = 1.8 mol L−1, cAIBN = 1....
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Figure 6: UV–vis spectra of the reaction mixture with DPPH radical at the beginning (violet line, 0.23 mM) of...
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Figure 7: Copolymer composition curves for the systems MLA with styrene and MMA.
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Figure 8: 1H NMR spectrum of MLA with 1 equiv of thioacetic acid and 0.15 equivalents of an inhibitor 4-metho...
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Scheme 3: Mechanism of RAFT polymerization [24].
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Figure 9: Structures of used RAFT agents examined in the polymerization of MLA.
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Figure 10: A) Kinetic plot for the RAFT copolymerization of MLA and DMA for the ratio 90/10 employing EMP. B) ...
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- Published 06 Jul 2016
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Scheme 1: Alkylation of N-VP with 1,8-dibromooctane yielding paraffin-like oligomers 2a–c.
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Figure 1: Chemical structure of water swellable network 3a and 3b. Photographs of water-swollen polymer disks...
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Scheme 2: Synthesis of the branched oligomeric dye 6: a) radical thiol–ene click reaction of 2a with 2-aminoe...
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Figure 2: UV–vis spectra of oligomers 5 (c = 0.16 g/mL, red), 6 (c = 0.63 g/mL, blue) and DFA (c = 0.016 g/mL...
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- Published 10 Feb 2016
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Figure 1: Schematic representation of a deprotection taking the relatively high polarity of the transition st...
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Scheme 1: Synthesis of Br-t-Boc-protected monomers 3a,b and homopolymers 6a,b.
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Figure 2: 300 MHz 1H NMR spectrum of 3a in CDCl3.
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Figure 3: 300 MHz 1H NMR spectrum of 3b in CDCl3.
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Scheme 2: Stability of 3 in different solvents.
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Scheme 3: Synthesized derivative monomers 3c,d.
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Scheme 4: a) Self deactivation of homopolymer 6a,b due to competing hydrogen interactions in comparison to b)...
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Figure 4: Kinetic studies of the deprotection of 3a, 6a and 7a.
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Figure 5: 300 MHz 1H NMR spectra of a) 6a in CDCl3 and b) 8a in DMSO-d6.
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- Full Research Paper
- Published 24 Oct 2014
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Scheme 1: Synthesis of N-(4-hydroxy-3-(pyridin-3-yldiazenyl)phenethyl) methacrylamide (5) and preparation of ...
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Figure 1: Color-changing effects of polymer 7 upon addition of A) CuSO4 and B) CuSO4 and γ-CD in a 50:50 vol ...
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Figure 2: UV–vis absorption spectra of (orange) the solved copolymer 7 with the induced shifts by addition of...
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Figure 3: Number average particle size distribution of 7 obtained by DLS experiments.
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- Published 25 Sep 2014
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Scheme 1: Three-step synthesis of azide-functionalized phenolphthalein derivative PP-N3. a) H2O, CH2Cl2, 0 °C...
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Scheme 2: Synthesis of the dipolarophil mPEG-prop and subsequent coupling with PP-N3.
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Figure 1: Schematic illustration of the complex formation of PEG-PP and DPE-CD.
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Figure 2: Solution of PEG-PP (0.05 mg/mL) a) at pH 10, b) in presence of 16.7 equiv DPE-CD at pH 12, c) in pr...
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Figure 3: UV–vis spectra of PEG-PP solutions containing different amounts of DPE-CD and RAMEB-CD.
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- Published 21 Aug 2014
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Scheme 1: Synthesis of monomer 2-methacrylamido-caprolactam (4) and copolymers 6a–i based on 4 and N,N-dimeth...
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Figure 1: Turbidity curves upon heating and corresponding curves upon cooling of 10 mg ml−1 solution of polym...
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Figure 2: 2D NMR ROESY (300 MHz, D2O) spectrum of monomer 4CD (a), Job plot of 2 with RAMEB-CD (b).
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Figure 3: Turbidity curves upon cooling of 10 mg ml−1 solution of copolymer 6a in various n-alcohols at a coo...
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Figure 4: Turbidity curves upon cooling of 10 mg ml−1 solution of polymer 6a and 6aCD at a cooling rate of 1 ...
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Figure 5: Glass-transition temperature as a function of the amount of N,N-dimethylacrylamide (5) in the copol...
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- Published 29 Jul 2014
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Scheme 1: Synthetic route for the preparation of the thiol-functionalized bisphenols 10a and 10b.
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Scheme 2: Synthetic route for the preparation of thiol-functionalized phenol derivatives 14a–c and 17 using t...
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Figure 1: FTIR spectra of compounds 12b, 13b and 14b.
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Figure 2: Top: 1H NMR spectrum of 3,3’-(propane-2,2-diylbis(2-(3-mercaptopropoxy)-5,1-phenylene))bis(propane-...
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Scheme 3: Chemical structures of components utilized in the present study.
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Figure 3: Development of the shrinkage force as function of time of dental composites containing 39.8 wt % or...
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- Published 22 Apr 2014
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Scheme 1: Synthesis of Z-configurated model compounds 3a/b from E-benzaldoxime and acrylates 2a/b.
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Figure 1: 1H NMR spectra of 3a (300 MHz, DMSO-d6).
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Scheme 2: Proposed molecular interactions of nitron 3a and dimethyl itaconate (4).
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Scheme 3: 1,3-Dipolaric cycloaddition of nitrones 3a/b with dimethyl itaconate (4).
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Scheme 4: Synthetic route to bio-based dinitrones derived from isosorbide.
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Scheme 5: Synthesis of poly(isosorbide itaconate -co- succinate) 13 from isosorbide (6), itaconic acid (11) a...
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Figure 2: Oscillation measurements during thermal cross-linking of unsaturated polyester 13 with dinitrones 1...
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- Full Research Paper
- Published 19 Mar 2014
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Scheme 1: Synthetic route for the synthesis of thiol functionalized 4-alkylphenols.
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Scheme 2: Synthetic route for the chain transfer polymerization of N,N-diethylacrylamide (7) with CTA 6a and ...
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Figure 1: Section of the MALDI –TOF spectrum of polymer 8b, indicating the high degree of end-group functiona...
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Figure 2: 1H NMR spectrum of polymer 9b in CDCl3 (300 MHz, rt).
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Figure 3: Top left: Section of the FTIR-spectrum of polymer 8b (black line) in comparison to 8bOx (red line);...
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Figure 4: Dependency of the cloud point values on the degree of polymerization (calculated by end-group analy...
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Figure 5: Shifts of the cloud points after the oxidation of the polymers (8a–d, 9a–d) to its corresponding su...
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Figure 6: Turbidimetry measurements of polymer 8b (straight black line – heating curve; dotted black line – c...
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Figure 7: 2D NMR NOESY spectrum of polymer 8b with two equivalents RAMEB-CD in D2O (600 MHz, rt).
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Figure 8: Left: Schematic illustration of the micellar-like structures and reversibility by addition of RAMEB...
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Figure 9: Schematic illustration of the micellar-like structures, its deformation upon addition of one equiva...
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- Published 09 Dec 2013
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Scheme 1: Synthesis of sulfonamide 3, N-alkylation of 3 in organic solution and of CD-complex (3β) in aqueous...
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Figure 1: 2D NMR ROESY spectrum of the complex of 3 with β-CD in D2O, displaying the interaction of the tosyl...
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Scheme 2: Cyclization of L-(+)-lysine monohydrochloride to give racemate 8.
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Figure 2: Oscillatory rheological measurements of an equimolar mixture of 6 and 8 at 50 °C. Illustrated is th...
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- Published 05 Dec 2013
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Scheme 1: Synthesis of the monomers 5 and 7, as well as the chemical structure of the diepoxide 8, comprising...
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Figure 1: Heating curves of the LCST measurements of 9, the complex of 9 with RAMEB-CD 9β, and of 9 with RAME...
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Figure 2: LCST measurements of 10 with illustrated heating and cooling curve, as well as the heating curve af...
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Figure 3: 2D NMR ROESY (300 MHz, D2O) spectrum of the complex of 5 with RAMEB-CD (a), displaying the correlat...
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Figure 4: Oscillatory rheological measurements of the curing of 9 and 10, respectively at 25 °C. Illustrated ...
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Figure 5: Illustration of the viscosity of a mixture of 5 and 8 (a), respectively 7 and 8 (c) before curing a...
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Figure 6: Comparison of the FTIR spectra of the monomer mixture of 5 and 8 and of the cured product 9 after 2...
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- Published 13 Aug 2013
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Scheme 1: (a) Synthesis of a polycationic cross-linked hydrogel containing disulfide groups. (b) Reductive cl...
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Figure 1: Release of enclosed dyes from polycationic networks containing disulfide bonds after treatment with...
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Figure 2: (a) Behavior of poly(DEAAm-co-DMAEMA) (left) and cross-linked poly(DEAAm-co-DMAEMA) (right) in dist...
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Scheme 2: Synthesis of poly(DEAAm-co-DMAEMA) discs. (a) Cross-linked discs with CL 1. (b) Cross-linked discs ...
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Figure 3: Storage modulus G’ as function of applied shear stress τ for samples 4 and 5 containing different a...
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Figure 4: Storage modulus G’ of samples 6 immersed in water (full symbols) or DTT solution (empty symbols) co...
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Figure 5: Storage modulus G’ of a polymer disc 6c containing 5.0 mol % CL 1 and 5.0 mol % CL 2 after being im...
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Figure 6: Swelling degree Q of polymer discs 4–6 as a function of the amount and type of containing cross-lin...
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- Published 01 Jul 2013
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Scheme 1: Hydrosilylation of Si–H terminated poly(dimethylsiloxanes) 1 and 2 with mono-((6-N-(allylamino)-6-d...
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Figure 1: IR spectra of (a) H-terminated disiloxane (1), (b) α-CD-terminated disiloxane (α-CD-disiloxane) (4)...
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Figure 2: 1H NMR spectra of ferrocene (A), complex of α-CD-disiloxane (α-CD-DS) 4 with ferrocene (B) and comp...
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Figure 3: 2D ROESY NMR spectra of the complex of α-CD-disiloxane (α-CD-DS) 4 with ferrocene.
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Figure 4: 2D ROESY NMR spectra of the complex of α-CD-polydimethylsiloxane (α-CD-PDMS) 5 with ferrocene.
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Figure 5: TEM images of α-CD-disiloxane 4 (A) and the supramolecular formation of α-CD-disiloxane 4 with ferr...
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Figure 6: DLS measurements of α-CD-disiloxane 4 (A) (dashed line) and the supramolecular formation of α-CD-di...
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- Full Research Paper
- Published 29 Apr 2013
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Scheme 1: Synthesis of fluorescent cyclodextrin 3 by click-chemistry.
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Figure 1: 1H NMR-ROESY spectrum of the modified CD 3.
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Figure 2: UV–vis spectrum of 3 (4 × 10−4 M) with and without a 10-fold excess of potassium adamantane-1-carbo...
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Figure 3: Fluorescence spectrum of 3 (4 × 10−4 M) with and without a 10-fold excess of 1-adamantanecarboxylic...
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Figure 4: DLS measurement of 3 with and without a 10-fold excess of potassium adamantane-1-carboxylate; black...
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Figure 5: AF4 elution diagram of 3.
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- Full Research Paper
- Published 28 Feb 2013
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Scheme 1: Synthesis of red (9, 12, 15), blue (6, 10) and green (2) polymerizable dyes.
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Figure 1: Visible spectra of the polymerizable dyes green 1/2 (a) and blue 6 (b).
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Figure 2: Visible spectra of red 9 and blue 10.
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Figure 3: Sharpened blank of polymerized red 9 and blue 10 with HEMA, THFMA and EGDMA (left, right).
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Figure 4: Sun-test results of 6.
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Figure 5: Broad spectrum of colors, created by mixing of green 2, blue 6 and red 15.
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- Published 13 Dec 2012
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Figure 1: Chemical structure of Triton® X-100 (1).
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Figure 2: Solubility in water of 0.2 wt % Triton® X-100 (1) and its different assumed complexes with RAMEB-CD...
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Scheme 1: Idealized reaction of the complexation of the (meth)acrylic monomer derived from Triton® (2 and 3) ...
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Scheme 2: Homopolymerization of the uncomplexed monomers 2 and 3 to the polymers 8 and 9 in DMF with AIBN as ...
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Scheme 3: Polymerization of the RAMEB-CD complexed monomers 4, 5, 6 and 7 to the homopolymers 10, 11, 12 and ...
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Figure 3: Transmittance [%] and zero-shear-viscosity [Pas] as a function of temperature for a 50 wt % solutio...
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- Published 04 Dec 2012
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Scheme 1: Synthetic pathway to the desired polymer 7.
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Figure 1: Cyclic voltammetry results of (A) clicked copolymer 7, (B) clicked copolymer 7 with Ad-COOK (
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Figure 2: DLS measurement of compound 2 with β-cyclodextrin (— •), alkylated polyphenol 4 (- -), product 7 (—...
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- Published 14 Nov 2012
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Scheme 1: CTP of 1 and end-group functionalization with 5 yielding the azo-dye-end-group-labeled polymer 6.
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Figure 1: Absorption spectra of 6 in water in a pH range from 7 to 2 (A). Absorption spectra of 6 in water de...
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Figure 2: LCST measurements of 6, the complex of 6 and RAMEB-CD, and in comparison to pure PNIPAM.
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Figure 3: Hydrodynamic diameters of 6, 7 and 8 (1 mg/mL) at 20 °C.
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Figure 4: z-Average diameter (DZ) of the complex 8 in water as a function of temperature (0.5 mg/mL, heating ...
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- Published 13 Sep 2012
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Scheme 1: Mechanism of free radical ring-opening polymerization of 2-VCPs (In: initiator) [29-31].
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Scheme 2: Synthesis of diethyl 2-vinyl-1,1-cyclopropanedicarboxylate [33].
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Scheme 3: Two-step synthesis of the macromonomer 5 (In: Initiator, TEA: triethylamine).
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Figure 1: MALDI-TOF MS of amino-terminated poly(NiPAAm) 3.
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Figure 2: Optical transmittance of aqueous solutions (c = 20 mg/mL) of 3, 6 und 8 during heating.
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Figure 3: 2D ROESY NMR spectrum of a 5/Me2-β-CD deuterated water solution.
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Figure 4: Temperature-dependent transparency measurements of aqueous solution of the supramolecular complex 7...
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Scheme 4: Homo- and copolymerization of macromonomer 5.
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- Full Research Paper
- Published 13 Mar 2012
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Scheme 1: Reaction of p-bromanil (1) with 1-butylimidazole (2).
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Figure 1: 1H NMR spectrum of mesomeric betaine 3.
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Figure 2: 13C NMR spectrum of dipole 3.
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Figure 3: Solid-state molecular structure of compound 3. Selected bond distances [Å]: O(1)–C 1.228(4), O(2)–C...
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Figure 4: Formation of molecular layers in the crystal packing.
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Figure 5: Higuchi–Connors phase diagram of 3/m-β-CD complex.
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Scheme 2: Mechanism of molecular association of the complex.
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Figure 6: Classification of betaine 3.
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Scheme 3: Synthesis of polymer 6 and oligomer 7 based on imidazolium-enolate structures.
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Figure 7: Thermogravimetric analyses of polymer networks 6a–c and oligomers 7a,b.
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- Published 10 Nov 2011
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Scheme 1: Synthetic pathway to the desired β-cyclodextrin-comprising copolymer and its supramolecular system.
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Figure 1: 2-D ROESY NMR spectrum of complexed β-CD with (+)-ephedrine.
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Figure 2: Turbidity measurement showing different cloud points for the CD-comprising copolymer 1 (32 °C) and ...
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Figure 3: DLS measurement showing hydrodynamic diameters for (a) the CD-comprising polymer and (b) for supram...
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- Full Research Paper
- Published 18 Aug 2011
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Scheme 1: Preparation of salts and/or complexes 4, 5 and 6.
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Figure 1: UV–vis spectra of complex 4 in basic solution (pH 10, t = 0 (blue line), t = 24 h (red line), t = 4...
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Figure 2: UV–vis spectra of complex 5 in solution before heating (solid line) and after 30 min of heating at ...
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Figure 3: UV–vis spectra of complex 6 in solution (pH 6) before heating (solid line) and after 30 min heating...
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Figure 4: UV–vis spectra of complex 6 in basic solution (pH 10) before heating (solid line), after 24 h witho...
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- Published 14 Feb 2011
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Scheme 1: Synthesis of copolymers 3D, 3L and CD-complexes 4D, 4L.
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Figure 1: 2D NMR ROESY spectrum of monomer 2D with RAMEB-CD.
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Figure 2: 2D NMR ROESY experiment showing the correlation between protons of the phenyl moiety of 4D with the...
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Figure 3: NMR shifts of the complexed monomer 2D.
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Figure 4: Comparison of 1H NMR spectra of 2D and 2L complexed with β-CD.
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Figure 5: Complex formation with phenolphthalein and phenylalanine as competitor.
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Figure 6: Hydrodynamic diameters of the copolymers and their corresponding complexes with RAMEB-CD a) L-pheny...
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- Published 01 Oct 2010
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Scheme 1: One-pot synthesis of epoxide-amine adducts via MW-assisted transfer hydrogenation.
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Figure 1: 13C NMR spectra of 4, measured in CDCl3.
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Figure 2: MALDI-TOF MS spectra (linear mode) of epoxide-amine product 4.
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Figure 3: GPC curve of epoxide-amine product 4 detected by UV absorption.
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Figure 4: Number-average hydrodynamic diameters of compound 4 prepared via the one-pot (continuous line) and ...
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Scheme 2: Ring-opening polymerization of ε-CL using alcohol units as initiator.
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Figure 5: GPC curves of the new formed graft copolymer 6 detected by UV absorption (continuous line) and RI (...
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Figure 6: Number-average hydrodynamic diameters of compounds 4 (left) and 6 (right).
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- Full Research Paper
- Published 01 Jun 2010
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Scheme 1: Homopolymerization of vinylferrocene 1.
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Figure 1: Dynamic light scattering of methyl-β-CD 2 (solid line), vinylferrocene 1 complexed with methyl-β-CD...
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Figure 2: The cyclic voltammetry for the complexed PVFc/PVFc+-system 3/6: 1.0 × 10−3 M substance in Na2SO4 | ...
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Figure 3: Redox behaviour of PVFc 3: (a) the complexed PVFc 3 mixed with aqueous hydrogen peroxide solution w...
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Scheme 2: Copolymerization of vinylferrocene 1 with NiPAAM 5 (1:20).
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Figure 4: Lower critical solution temperature of PVFc-co-P(NiPAAM) 7 (1:20) (solid line): 17 °C and complexed...
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