Phase Separation of Poly(methyl methacrylate)/Poly(styrene-co-acrylonitrile) Blends with Controlled Distribution of Silica Nanoparticles

Abstract

Effects of selective location of silica nanoparticles on the phase separation of poly(methyl methacrylate)/poly(styrene-coacrylonitrile) (PMMA/SAN) blends were investigated via combination of rheological method and optical microscopy. Through grafting polystyrene chain to the surface of silica nanoparticles, the silica nanoparticles were controlled to selectively locate at interfaces or in the PMMA-rich domains. Power-law analysis of the moduli and shifted Cole−Cole plots were applied to determine rheological transition temperature (apparent binodal temperature) of blend with near-critical and off-critical compositions for both neat blends and particle-filled blends. The particle location had significant influence on the rheological transition temperature but little impact on optically determined binodal temperature. This discrepancy was discussed through morphology observation via transmission electron microscopy (TEM) for blends under different phase separation conditions. It was found that nanoparticles retard coarsening of morphology during phase separation. The most striking slowdown was found in off-critical blends with nanoparticles located on the interface. On the other hand, nanoparticles preferentially locating in the minor phase could act as nucleation sites but decreased the total number of nuclei. The difference in the rheological transition temperatures is ascribed to the effect of nanoparticles on the components' viscoelasticity and the morphology during phase separation.

Evolution of concentration fluctuation during phase separation in polymer blends with viscoelastic asymmetry

“…Previous study has shown that PMMA/SAN blends have a LCST-type phase diagram with the critical temperature about 155 C at critical composition 70/30 [33].…”

Effect of multiwall carbon nanotubes on the phase separation of concentrated blends of poly[(α-methyl styrene)-co-acrylonitrile] and poly(methyl methacrylate) as studied by melt rheology and conductivity spectroscopy

“…In addition, nanoparticles can impart intriguing properties to the blends such as morphological stability, electrical conductivity, structural integrity etc. Hence, the effect of nanoparticles on the compatibility and the phase separation process has been the subject of several experimental studies and simulations [1][2][3][4][5][6][7][8][9][10][11][12][13][14]. For example, Balazs and co-workers [9] found numerically that hard mobile nanoparticles with a preferential affinity for one of the components, slow down the coarsening of the domains in the late stages of spinodal decomposition whereas particles with no preferential adsorption do not affect the phase separation kinetics.…”

“…in absence of adsorption of polymer chains depletion forces become dominant and could lead to particle-particle aggregation and hence induce phase separation. In addition, the effect of nanoparticles on phase separation characteristics such as critical temperatures, kinetics and morphology development was reported to depend on the particle size, concentration and the interaction between the particle and the host matrix [2,3,4,12,15]. Hence, assessing the interaction between the nanoparticles and the components is essential to gain a thorough understanding of the thermodynamics and kinetics of phase separation.…”

“…Kim et al [26] observed that both the storage and loss modulus increase initially, followed by a decrease at longer time scales due to the coarsening of the cocontinuous structures. Particularly in the case of particle-filled blends for which optical techniques can often not be used, rheological techniques can provide essential information about the phase separation characteristics [8,[10][11][12][13][14]. However, in the case of dynamically symmetric blends, rheology can only pick up signals when the correlation length of the concentration fluctuations is large enough [10,13].…”

Morphology evolution, conductive and viscoelastic behaviors of chemically reduced graphene oxide filled poly(methyl methacrylate)/poly(styrene-co-acrylonitrile) nanocomposites during annealing

“…Hence, T s s can be also obtained by isothermal dynamic frequency sweep tests and independent on the heating rate. The gel-like behavior or long-range continuity has been observed in the unfilled or nanofillers-filled polymer blends with the co-continuous morphology formed at the early stage of spinodal decomposition (SD) phase separation [53,57,59,60] . The critical gel-like behavior refers to the phenomenon at low frequencies(s) which is shown mathematically by Eq.…”