Polymer phase homogeneous

Pure amorphous polymers, being homogeneous materials, are transparent. Atactic polystyrene is a good example. The crystalline syndiotactic form is not transparent. Alack of transparency does not necessarily indicate crystallinity, however. It can also be caused by inorganic fillers, pigments, gas bubbles (as in a foam), a second polymer phase, etc. 

Intermolecular forces also play an important role in determining the compatibility of two or more polymers in a polymer blend or polymer alloy. Although the distinction between a polymer blend and a polymer alloy is still the subject of some debate, we will use the convention that a polymer alloy is a single-phase, homogeneous material (much as for a metal), whereas a blend has two or more distinct phases as a result of polymer-polymer immiscibility (cf. Section 2.3.3). In general, polymers are... 

Two types of viscous fermentations exist (a) Mycelial fermentations viscosity is due to microbial network structure dispersed in a continuous phase, (b) Polysaccharide fermentation viscosity is due to polymer in an aqueous phase-homogeneous viscous liquid. 

Claverie et al. [325] have polymerized norbornene via ROMP using a conventional emulsion polymerization route. In this case the catalyst was water-soluble. Particle nucleation was found to be primarily via homogenous nuclea-tion, and each particle in the final latex was made up of an agglomeration of smaller particles. This is probably due to the fact that, unlike in free radical polymerization with water-soluble initiators, the catalyst never entered the polymer particle. Homogeneous nucleation can lead to a less controllable process than droplet nucleation (miniemulsion polymerization). This system would not work for less strained monomers, and so, in order to use a more active (and strongly hydrophobic) catalyst, Claverie employed a modified miniemulsion process. The hydrophobic catalyst was dissolved in toluene, and subsequently, a miniemulsion was created. Monomer was added to swell the toluene droplets. Reaction rates and monomer conversion were low, presumably because of the proximity of the catalyst to the aqueous phase due to the small droplet size. 

Polymerization in a single-phase homogeneous solution in THF/water mixtures (2 1) has also been reported [235]. Such reactions allowed for the preparation of a poly (p-phenylene) with sulfonate ester and dodecyl side groups [Eq. (10)]. By comparison to the aforementioned biphasic polymerizations, the synthesis of polymers with higher degrees of polymerization was reported in the solution procedure. 

For a non-phase-separated blend of P H B/ P LA, the visual image of the elongated polymer appears homogeneous and has a uniform thickness [53]. This observation is also reflected in the images derived from the PHB- and PLA-specific absorption bands. Furthermore, the orientation function of the PHB and PLA absorption bands is, over the whole area, negative and positive, respectively. 

Figure 2. Two mechanisms of the transition from monomer to polymer phase (a) heterogeneous, (b) homogeneous growth of polymer chains.

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