Composite droplet phase

Heterogeneous Copolymerization. When copolymer is prepared in a homogeneous solution, kineiic expressions can be used to predict copolymer composition Bulk and dispersion polymerization are somewhat different since the reaction medium is heterogeneous and polymeri/aiion occurs simultaneously in separate loci. In bulk polymerization, for example, the monomer swollen polymer particles support polymerization within the particle core us well as on the particle surface, lit aqueous dispersion or emulsion polymeri/aiion the monomer is actually dispersed in two or three distinct phases a continuous aqueous phase, a monomer droplet phase, and a phase consisting of polymer particles swollen at Ihe surface with monomer. This affect the ultimate polymer composition because llie monomers are partitioned such that the monomer mixture in the aqueous phase is richer in the more water-soluble monomers than the two organic phases. 

Non-Aqueous Processes. Dispersions of composite particles in non-aqueous media (12) have been prepared. The particles were sterically stabilised to prevent flocculation and aggregation. This was achieved by physical absorption of amphipathic graft or block copolymer (13,14) or by covalent attachment of diluent-soluble oligomer or polymer chains (15) at the particle surface so that by definition different polymers were situated at the surface and in the bulk of the particles, even for single-polymer particles. Composite particles were prepared by slow addition of the second monomer which was fully miscible with the diluent phase, obviating a monomer droplet phase further monomer-soluble initiation and amphipathic graft stabiliser was included as appropriate so that the process comprised continued dispersion... 

Figure 9-1 Schematic phase diagram of a binary fluid mixture of small molecules. The two-phase region lies under the binodal line, the apex of which defines the critical temperature Tc and critical composition Between the binodal and the spinodal lines, phase separation is by nucleation and growth (NG), while under the spinodal line it is by spinodal decomposition (SD). Within the region of spinodal decomposition, near the compositional symmetry line, there is a region where the morphology is initially bicontinu-ous. Outside of this region, one of the phases is a discontinuous droplet phase. Eventually,...

While a great deal of information has been pubhshed over the years on the theoretical and practical aspects of emulsion formation and stabilization, until recently little has been said about more complex systems generally referred to as multiple emulsions. Multiple emulsions, as the name implies, are composed of droplets of one liquid dispersed in larger droplets of a second liquid, which is then dispersed in a final continuous phase. Typically, the internal droplet phase will be miscible with or identical to the final continuous phase. Such systems may be w/o/w emulsions as indicated in Figure 11.13, where the internal and external phases are aqueous or o/w/o, which have the reverse composition. Although known for almost a century, such systems have only recently become of practical interest for possible use in cosmetics,... 

Fig. 3.71 Correlation between the fraction of POM droplets in POM/HaV blends with a composite-like phase morphology and the intensity of the homogeneous crystallization peak (Everaert et al. 2000)...

The emulsifying effects of a small quantity of a block copolymer, A-B, added to immiscible blend of homopolymers A and B, were examined by Leibler (1988). The theory predicted the reduction of the interfacial tension coefficient, Vi2, caused by equilibrium adsorption of a copolymer at the interface. For well-chosen compositions and molecular weights of the copolymer, low values of Vj2 are to be expected. This suggests a possible existence of thermodynamically controlled stable droplet phase, in which the minor phase homopolymer drops are protected by an interfacial film of the copolymer, interfacing the matrix polymer. The size distribution of the droplets is expected to depend on the rigidity and spontaneous radius of curvature of the interfacial film that can be controlled by molecular structure of the copolymer. 

KAlSi20g represents the glassy droplet phase, having near leucite composition. 

There exist in polymer blends two or three major types of phase morphologies, depending on whether the encapsulated structures (composite droplets) are considered as a class apart. The most common is the droplet-in-matrix (as, for example, Figure 1.3), the (droplet-in-droplet)-in-matrix (as, for example. Figure 1.4), and the cocontinuous phase morphology where both phases are mutually interconnected throughout the whole volume of the blend (as, for example. Figures 1.5 and 1.6). 

SEM photomicrographs of blend 1 having HDPE as a matrix in which are dispersed the two minor phases (low-Mw polystyrene/low-Mw PMMA) at 2 min (A) and 15 min (B) of mixing time. PS is extracted by cyclohexane. A stable composite droplet morphology is obtained within 2 min of mixing. The white scale bar denotes 1 pm. (From J. Reignier, B. D. Favis, and M.-Cl. Heuzey, Polymer 44,49-59,2003. With permission.)... 

Nonionic surfactants of the type of CjEj show a strongly temperature-dependent phase behavior. In the present chapter we restrict ourselves to mixtures of water, octane (Merck, Darmstadt, Germany), and C12E5 (Nikko Chemicals, Tokyo, Japan). These intensively smdied mixtures show extended droplet phases [10,11,31,54,58,60], Sample compositions are given by the volume fractions of water ( ) , octane ( )o, and surfactant ( )s. 

From the numerical simulation point of view the encapsulation process consists of (see Fig. 13.1) the components (1) a concentric nozzle being responsible for contacting of the core and shell phases, (2) a modulator being able to introduce modulation disturbances into the system so to enable the controlled breakup and the (3) laminar jet itself being broken into preferably monodisperse composite droplets. 

Metal matrix composite (MMC) particles can be fabricated through mixing solid particles and atomized liquid droplets in a spray atomization and co-injection process [4, 5, 30, 31, 52]. The process is characterized by a three-phase spray flow (gas/droplets/ particles). Solid particles (usually at least one order of magnitude smaller than atomized droplets), conveyed by the atomization gas or via a separate gas-assisted delivery system, are injected into the droplet spray and likely to be incorporated into the droplets or captured by the droplets surface during frequent impingements, forming composite droplets which are subsequently solid-ifled as composite particles. 

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