TY  - JOUR
AU  - Puig-Rigall, Joan
AU  - Obregon-Gomez, Ines
AU  - Monreal-Pérez, Pablo
AU  - Radulescu, Aurel
AU  - Blanco-Prieto, María J.
AU  - Dreiss, Cécile A.
AU  - González-Gaitano, Gustavo
TI  - Phase behaviour, micellar structure and linear rheology of tetrablock copolymer Tetronic 908
JO  - Journal of colloid and interface science
VL  - 524
SN  - 0021-9797
CY  - Amsterdam [u.a.]
PB  - Elsevier
M1  - FZJ-2018-02268
SP  - 42 - 51
PY  - 2018
AB  - Tetronics are X-shaped block-copolymers of polyethylene oxide and polypropylene oxide, which self-assemble into micelles and can undergo a sol-gel transition; these transitions are dependent on temperature, concentration but also pH, due to the central diamine group of the tetrablock. We report the nanoscale morphologies underlying these different phases and the rheology of the systems for a very large, highly hydrophilic block copolymer, Tetronic 908, through the combined use of oscillatory rheology, steadyblock-state and time-resolved fluorescence, small-angle neutron scattering (SANS), dynamic light scattering (DLS) and Fourier transform infrared attenuated total reflectance (FTIR-ATR). At low concentrations, SANS reveal core-shell micelles of ca. 10 nm radius, presenting a dehydrated core and a highly hydrated shell, with relatively small aggregation numbers (Nagg ≈ 13). The micelles are notably affected by the pH, due to the protonation of the central amine spacer at low pH (pH ≈ 2), which shifts micellization to higher temperature, with smaller micelles than at natural pH. In the intermediate concentration regime (10–15%), micelles become smaller (Nagg ≈ 5), and present a higher hydration of the core. In the high concentration regime, Tetronic 908 undergoes a sol-gel transition above a threshold temperature, which is fully inhibited at acidic pH. SANS data from the gel phase reveal a BCC order of tightly packed spheres. Temperature sweeps in oscillatory rheology show a shift of the onset of gelation towards lower temperatures as concentration increases, an increase in the elastic modulus G′ and an expansion of gel region over a larger range of temperatures. SANS and rheology reveal that at pH below the natural pH (ca. 8), gelation is shifted to higher temperatures, but the morphology of the gels is similar, while under highly acidic conditions the gelation is fully suppresed.
LB  - PUB:(DE-HGF)16
C6  - pmid:29631218
UR  - <Go to ISI:>//WOS:000434494400006
DO  - DOI:10.1016/j.jcis.2018.03.096
UR  - https://juser.fz-juelich.de/record/844926
ER  -