TY - JOUR A1 - de Molina, Paula Malo A1 - Herfurth, Christoph A1 - Laschewsky, André A1 - Gradzielski, Michael T1 - Structure and dynamics of networks in mixtures of hydrophobically modified telechelic multiarm polymers and oil in water microemulsions JF - Langmuir N2 - The structural and dynamical properties of oil-in-water (O/W) microemulsions (MEs) modified with telechelic polymers of different functionality (e.g., number of hydrophobically modified arms, f) were studied by means of dynamic light scattering (DLS), small-angle neutron scattering (SANS), and high frequency rheology measurements as a function of the polymer architecture and the amount of added polymer. For this purpose, we employed tailor-made hydrophobically end-capped poly(N,N-dimethylacrylamide) star polymers of a variable number of endcaps, f, of different alkyl chain lengths, synthesized by the reversible addition-fragmentation chain transfer method. The addition of the different end-capped polymers to an uncharged ME of O/W droplets leads to a large enhancement of the viscosity of the systems. SANS experiments show that the O/W ME droplets are not changed upon the addition of the polymer, and its presence only changes the interdroplet interactions. The viscosity increases largely upon addition of a polymer, and this enhancement depends pronouncedly on the alkyl length of the hydrophobic sticker as it controls the residence time in a ME droplet. Similarly, the high frequency modulus G(0) depends on the amount of added polymer but not on the sticker length. G(0) was found to be directly proportional to f - 1. The onset of network formation is shifted to a lower number of stickers per ME droplet with increasing f, and the network formation becomes more effective. Thus, the dynamics of network formation are controlled by the polymer architecture. The effect on the dynamics seen by DLS is even more pronounced. Upon increasing the polymer concentration, slower relaxation modes appear that become especially pronounced with increasing number of arms. The relaxation dynamics are correlated to the rheological relaxation, and both are controlled by the polymer architecture. Y1 - 2012 U6 - https://doi.org/10.1021/la303673a SN - 0743-7463 VL - 28 IS - 45 SP - 15994 EP - 16006 PB - American Chemical Society CY - Washington ER - 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 -