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  • 1
    Electronic Resource
    Electronic Resource
    Heterogeneous percolation-to-cluster transition in phase separation of an off-critical polymer mixture (1999)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 110 (1999), S. 3612-3620 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Phase separation kinetics of an off-critical polymer mixture involving percolation-to-cluster transition (PCT) was investigated by time-resolved light scattering and by transmission optical and electron microscopies. The process involving a splitting of a single peak in the light scattering profile into a double peak was observed for the first time after the onset of PCT. Each peak changes with time (t) according to different evolution modes, e.g., the first peak wave number qm,1 evolved according to the power law of percolated structures (qm∼t−α; α=0.9), while the time evolution of the second peak wave number qm,2 is very slow, which corresponds to the growth of cluster of the droplets after PCT. Furthermore, the real space pictures and the light scattering analysis reveal that a cluster of the small spherical droplets and the locally percolating domains coexist for a very long time. The percolating domains are larger than the small droplets, minor in volume fraction, and formed in bulk and they are developed into sheet-like grains with their surfaces parallel to the glass surface. © 1999 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.478229
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  • 2
    Electronic Resource
    Electronic Resource
    Intermittency of droplet growth in phase separation of off-critical polymer mixtures (1998)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 108 (1998), S. 1225-1233 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Kinetics of the phase separation in binary off-critical mixtures of polybutadiene (PB) and polyisoprene (PI) was investigated as a function of quench depth and composition by using time-resolved light scattering. The kinetics for the off-critical mixtures is much slower than that for the critical mixture. The scattering maximum for the off-critical mixtures is very broad relative to that for the critical mixture. For the off-critical mixtures, the domain growth follows the same power law (qm∼t−α, Im∼tβ: α=0.25–0.33, β=0.75–1) in the long time limit covered in our experiments, independent of quench depth and composition. However, the domain growth became very slow before the long time limit under a certain condition (intermittency of the domain growth). In the regime where the intermittency was observed, the scaling exponents α and β depend on quench depth. The shallower the quench, the smaller the values of α and β and the longer the intermittent regime. These behaviors are largely different from those for the critical mixture for which the scaling exponents show almost the same value in the late stage for different quenches and the Langer–Bar-on–Miller or Chou–Goldburg scaling postulate is fulfilled. Scaled structure factor in the late stage of phase separation process was found to depend on quench depth, becoming broader as quench is shallower. © 1998 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.475484
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  • 3
    Electronic Resource
    Electronic Resource
    Crossover of domain-growth behavior from percolation to cluster regime in phase separation of an off-critical polymer mixture (1997)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 107 (1997), S. 1634-1644 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Time-resolved light scattering has been used to investigate phase-separation dynamics for off-critical mixtures of polybutadiene (PB) and polyisoprene (PI) with a well defined phase diagram. Percolation-to-cluster transition (PCT) occurs in the course of the phase separation process for an off-critical mixture of the PB and the PI in the shallow quenches covered in this work. Before the onset of PCT occurs, the phase separation dynamics is fast, typically obeying qm∼t−0.9 and Im∼t2.7 ("percolation regime"), where qm is the scattering vector at the maximum scattered intensity Im. After the onset of PCT the time changes in qm and Im become very slow, and the phase separation process might appear to stop, if we observe the dynamics in a short time scale after the onset of PCT. The behavior corresponds to the results which Hashimoto et al. reported for the off-critical mixtures of poly(styrene-ran-butadiene) (SBR) and PB, and SBR and PI (spontaneous pinning of the domain growth) [J. Chem. Phys. 97, 679 (1992)]. However, it is shown in this paper that the droplets formed after PCT eventually grow according to the scaling law of qm∼t−n and Im∼t3n with n=1/4 to 1/3 ("cluster regime"), if we keep observing the phase separation process in the much longer time scale, beyond the time period over which the domain growth appeared to be pinned. To our knowledge, it is for the first time that such crossover of domain-growth behavior from percolation to cluster regime was observed via the intermittent time period over which the growth kinetics are apparently pinned. © 1997 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.474515
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    Paper (German National Licenses)
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