Equilibrium particle morphologies

Particle dynamics are a critical component of animal viruses and appear to fall into two broad categories fluctuations about an equilibrium point and large-scale dynamics that lead to a change in particle morphology. The former are essential for virus interactions with a cell and its uncoating. The latter are necessary for complex virus structures that cannot directly assemble into the final functional form. 

The first observations clearly show that polyols modify the equilibrium morphology of boehmite particles, as it has been reported in the case of gibbsite crystallization [20, 21]. The use of polyols allows to obtain departures of the diamond shaped morphology observed at pH ll. If boehmite particles synthesized in presence of C2 to C4 polyols are always diamond shaped, the proportion of (101) and (010) planes is modified (table 1). The highest proportion of (101) face is reached for boehmite synthesis in presence of mesoerythritol (C4). Xylitol (C5) causes much important changes as the particle morphology is isotropic in this case. 

The presence of chain transfer agents during the second-stage polymerization will produce a decrease in the molar mass of the shell polymer, which will result in more chain mobility and fieedom to achieve the equilibrium morphology, even under conditions where kinetically controUed particle morphologies (i.e. semi-continuous monomer addition) would normally dominate [57,67]. 

Chen et al. [39] and Jonsson et al. 140,41] independently proved that the composite particle morphology could be brought towards the equilibrium morphology predicted by the thermodynamic model by a post-polymerization swelling treatment of the composite latexes with solvents. 

The shape or form of the particles is referred to as the particle morphology. Particles may be uniformly spherical, have core-shell morphologies (51, 263), be hemispherical (382), have domains or inclusions (349), be nonspherical or irregular in shape, or may be inverted (in which the core and shell compositions are reversed). Figure 5 illustrates some of the possible particle morphologies. The particular morphology is determined by thermodynamic (equilibrium) (67,101) and kinetic (rate of phase separation versus rate of polymerisahon) considerations. In some cases, latex... 

As in the case of emulsion polymerization, particle morphology is ruled by the interplay between thermodynamics and kinetics. Equilibrium morphologies are reached when the internal viscosity of the polymer particle is low. Thus, due to the plasticizing effect of the alkyd resin, equilibrium morphologies are usually reached for alkyd/acrylic systems [96]. The equilibrium morphology is affected by the presence of graft copolymer that reduces the interfacial tension between the polymer phases in the particle. Methods to calculate the equilibrium morphology of multiphase polymer particles are available [43]. 

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