TY  - JOUR
A1  - Herfurth, Christoph
A1  - de Molina, Paula Malo
A1  - Wieland, Christoph
A1  - Rogers, Sarah
A1  - Gradzielski, Michael
A1  - Laschewsky, André
T1  - One-step RAFT synthesis of well-defined amphiphilic star polymers and their self-assembly in aqueous solution
JF  - Polymer Chemistry
N2  - Multifunctional chain transfer agents for RAFT polymerisation were designed for the one-step synthesis of amphiphilic star polymers. Thus, hydrophobically end-capped 3- and 4-arm star polymers, as well as linear ones for reference, were made of the hydrophilic monomer N,N-dimethylacrylamide (DMA) in high yield with molar masses up to 150 000 g mol(-1), narrow molar mass distribution (PDI <= 1.2) and high end group functionality (similar to 90%). The associative telechelic polymers form transient networks of interconnected aggregates in aqueous solution, thus acting as efficient viscosity enhancers and rheology modifiers, eventually forming hydrogels. The combination of dynamic light scattering (DLS), small angle neutron scattering (SANS) and rheology experiments revealed that several molecular parameters control the structure and therefore the physical properties of the aggregates. In addition to the size of the hydrophilic block (maximum length for connection) and the length of the hydrophobic alkyl chain ends (stickiness), the number of arms (functionality) proved to be a key parameter.
Y1  - 2012
U6  - https://doi.org/10.1039/c2py20126g
SN  - 1759-9954
VL  - 3
IS  - 6
SP  - 1606
EP  - 1617
PB  - Royal Society of Chemistry
CY  - Cambridge
ER  - 
TY  - CHAP
A1  - Laschewsky, André
A1  - Herfurth, Christoph
A1  - Miasnikova, Anna
A1  - Wieland, Christoph
A1  - Wischerhoff, Erik
A1  - Gradzielski, Michael
A1  - de Molina, Paula Malo
A1  - Weiss, Jan
T1  - Stars and blocks tailoring polymeric rheology modifiers for aqueous media by controlled free radical polymerization
T2  - Abstracts of papers : joint conference / The Chemical Institute of Cananda, CIC, American Chemical Society, ACS
Y1  - 2012
SN  - 0065-7727
VL  - 244
PB  - American Chemical Society
CY  - Washington
ER  - 
TY  - JOUR
A1  - Thuenemann, Andreas F.
A1  - Klobes, Peter
A1  - Wieland, Christoph
A1  - Bruzzano, Stefano
T1  - On the nanostructure of micrometer-sized cellulose beads
JF  - Analytical & bioanalytical chemistry
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 m(2) g(-1) in cellulose bead sample type MT50 and from 417 to 220 m(2) 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
Y1  - 2011
U6  - https://doi.org/10.1007/s00216-011-5176-z
SN  - 1618-2642
VL  - 401
IS  - 4
SP  - 1101
EP  - 1108
PB  - Springer
CY  - Heidelberg
ER  -