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摘要
Colloid-polymer mixtures may undergo either fluid-fluid phase separation or gelation. This depends on the depth of the quench (polymer concentration) and the polymer-colloid size ratio. We present a real-space study of dynamics in phase separating colloid-polymer mixtures with medium- to long-range attractions (polymer-colloid size ratio q(R) = 0.45-0.89), with the aim of understanding the mechanism of gelation as the range of attraction is changed. In contrast to previous studies of short-range attractive systems, where gelation occurs shortly after crossing the equilibrium phase boundary, we find a substantial region of fluid-fluid phase separation. Upon quenching deeper, the system undergoes a continuous crossover to gel formation. We identify two regimes, %26apos;classical%26apos; phase separation, where single particle relaxation is much faster than the dynamics of phase separation, and %26apos;viscoelastic%26apos; phase separation, where demixing is slowed down appreciably due to slow dynamics in the colloid-rich phase. Particles at the surface of the strands of the network exhibit significantly greater mobility than those buried inside the gel strand which presents a method for coarsening.
- 出版日期2013
