Kinetics of microphase separation in polymer systems: Theory and computer simulation

Thesis/Dissertation · Fri Jan 01 04:00:00 EST 1993

OSTI ID:7243179

Glotzer, S C

Many experiments have focused on the interesting and industrially important phenomenon of microphase separation in such systems as gelatin and atactic polystyrene in poor solvents, chemically-crosslinked homopolymer/copolymer mixtures, and multiblock copolymers in selective solvents. A common feature of these systems is the existence of competing interactions that dramatically change the kinetics of phase separation from the usual kinetics of spinodal decomposition observed in, e.g., binary fluids or homopolymer solutions. In phase-separating polymer solutions in which spinodal decomposition and gelation occur simultaneously, competition arises due to the different interaction energies present in the system. In particular, a recent experiment showed that this competition produces a [open quotes]pinning[close quotes] of the phase-separating mixture. In an effort to elucidate the effect of competing interactions on the kinetics of spinodal decomposition in such systems, a microscopic model containing two disparate energies is proposed, and results of Monte Carlo computer simulations are presented to show that this model exhibits many of the important features observed in experiments, particularly the phenomenon of pinning during phase separation. A scaling theory is proposed to explain certain power-law behavior associated with the pinning, and is consistent with the usual scaling theory of ordinary spinodal decomposition. A preliminary theory is developed for the pinning mechanism, providing a framework in which to understand the effect of the competing interaction energies and allowing the accurate prediction of the pinning exponents observed in the simulations. Finally, Monte Carlo simulation results of microphase separation in diblock and multiblock copolymers are presented, and the phenomenon of network formation is discussed. In this context, the applicability of models of multiblock copolymers to physical gels is examined.

• Research Organization: Boston Univ., MA (United States)
• OSTI ID: 7243179
• Country of Publication: United States
• Language: English

Related Subjects

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY
400105* -- Separation Procedures
CALCULATION METHODS
COMPUTERIZED SIMULATION
KINETICS
MATHEMATICAL MODELS
MONTE CARLO METHOD
PHASE STUDIES
POLYMERS
REACTION KINETICS
SEPARATION PROCESSES
SIMULATION
STATISTICAL MODELS