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Abstract
A new thermothickening aqueous system was presented based on mixtures of hydrophobically-modified acrylamide copolymer (HMPAM), poly(N-isopropylacryl-amide) (PNIPAM) and sodium dodecyl benzene sulfonate (SDBS). Unique in the thermothickening system, a maximum viscosity and the temperature (T max) when reaching such viscocity change independently, reflects the presence of intermolecular interactions. The T max of the new system suggests that its thermothickening behavior is correlated to the cloud point temperature (T c) of PNIPAM, which can be easily adjusted to desired values by the addition of SDBS. The experimental data also indicate that the temperature between the rheological transition temperature (T t) and T max in HMPAM+PNIPAM+SDBS is within the range of 35–65°C, and the thermothickening behavior originates from the reinforcement of the association network between HMPAM, PNIPAM and SDBS. Consequently, the viscosity over the corresponding thermosensitive range upon cooling is higher than that upon heating.
Acknowledgements
This work is financially supported by the National High Technology Research and Development Program of China (No. 2007AA090701-5).
Notes
a. Elemental analysis
b. in 0.1 M NaCl solution at 25°C