TY - JOUR A1 - Bruzzano, S. A1 - Sieverling, N. A1 - Wieland, Ch. A1 - Jaeger, W. A1 - Thünemann, Andreas A1 - Springer, J. T1 - Cationic polymer grafted starch from nonsymmetrically substituted macroinitiators N2 - The aim of this work was the synthesis of starch macroinitiators for cationic polymer grafted starches that: (i) are free of cationic homopolymer, and (ii) display a high degree of conversion of the cationic monomer. We show that this can be achieved by a free-radical polymerization reaction using the cationic monomer N-methacryloyloxyethyl-N,N-dimethyl-N-benzylammonium chloride (MADAM-BQ) and a new starch-based macroazoinitiator. For this purpose, the acid chloride of 4-tert-butylazo-4-cyanovaleric acid was synthesized and bound covalently to starch (predominantly in the C6 position) to form a nonsymmetrically substituted macroinitiator that was used to polymerize MADAM-BQ in aqueous media. Essentially no MADAM-BQ homopolymer was formed. The initiator decomposes thermally to starch radicals of high reactivity and low-molar mass radicals that do not initiate polymerization. The reason for the different reactivities of the radicals is presumably due to the nonsymmetric constitution of the starch-bound azo groups. The graft polymerization of MADAM-BQ in aqueous solution performs according to an ideal overall kinetic. The structure of the synthesized starch-graft-poly(MADAM-BQ) products is similar to that of block copolymers because of the low radical efficiency of the starch initiators in aqueous solution. Especially, starch substrates with a higher content of azo groups did not lead to graft products with shorter graft distances because the state of solution of these macroinitiators becomes worse and aggregation occurs with an increasing degree of substitution. KW - Starch KW - Azo macroinitiators PY - 2005 U6 - https://doi.org/10.1021/ma048063f SN - 0024-9297 SN - 1520-5835 VL - 38 SP - 7251 EP - 7261 PB - American Chemical Society CY - Washington, DC AN - OPUS4-10536 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Bruzzano, S. A1 - Wieland, Christoph A1 - Laschewsky, A. A1 - Mertoglu, M. A1 - Hofe, T. A1 - Leinweber, R. A1 - Thünemann, Andreas T1 - Polycations as Reference Materials for Aqueous Size Exclusion Chromatography T2 - 18th International Symposium on Polymer Analysis and Characterization, University of Sheffield CY - Sheffield, England DA - 2005-06-20 PY - 2005 AN - OPUS4-7492 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Thünemann, Andreas A1 - Klobes, Peter A1 - Wieland, Christoph A1 - Bruzzano, S. T1 - On the nanostructure of micrometer-sized cellulose beads N2 - The analysis of the porosity of materials is an important and challenging field in analytical chemistry. The gas adsorption and mercury intrusion methods are the most established techniques for quantification of specific surface areas, but unfortunately, dry materials are mandatory for their applicability. All porous materials that contain water and other solvents in their functional state must be dried before analysis. In this process, care has to be taken since the removal of solvent bears the risk of an incalculable alteration of the pore structure, especially for soft materials. In the present paper, we report on the use of small-angle X-ray scattering (SAXS) as an alternative analysis method for the investigation of the micro and mesopores within cellulose beads in their native, i.e., water-swollen state; in this context, they represent a typical soft material. We show that even gentle removal of the bound water reduces the specific surface area dramatically from 161 to 109 m² g-1 in cellulose bead sample type MT50 and from 417 to 220 m² g-1 in MT100. Simulation of the SAXS curves with a bimodal pore size distribution model reveals that the smallest pores with radii up to 10 nm are greatly affected by drying, whereas pores with sizes in the range of 10 to 70 nm are barely affected. The SAXS results were compared with Brunauer–Emmett–Teller results from nitrogen sorption measurements and with mercury intrusion experiments. KW - Small-angle X-ray scattering KW - Cellulose KW - Mesopores KW - Micropores KW - Porosimetry PY - 2011 U6 - https://doi.org/10.1007/s00216-011-5176-z SN - 1618-2642 SN - 1618-2650 VL - 401 IS - 4 SP - 1101 EP - 1108 PB - Springer CY - Berlin AN - OPUS4-24251 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER -