Stability, morphological

Paine et al. [99] tried different stabilizers [i.e., hydroxy propylcellulose, poly(N-vinylpyrollidone), and poly(acrylic acid)] in the dispersion polymerization of styrene initiated with AIBN in the ethanol medium. The direct observation of the stained thin sections of the particles by transmission electron microscopy showed the existence of stabilizer layer in 10-20 nm thickness on the surface of the polystyrene particles. When the polystyrene latexes were dissolved in dioxane and precipitated with methanol, new latex particles with a similar surface stabilizer morphology were obtained. These results supported the grafting mechanism of stabilization during dispersion polymerization of styrene in polar solvents. 

Note Compatibilizers usually stabilize morphologies over distances of the order of micrometers or less. 

Features - polymerization takes place in "solution" - catalyst residence time short (minutes) - catalyst and cocatalyst must show reasonably good high temperature stability - morphology and psd of catalyst are less important than in other processes - wide range of comonomers may be used... 

POLYMER ALLOYS - a sub-class of PB reserved for polymeric mixtures with stabilized morphologies ... 

Another approach to preparing model catalysts is the preparation of inverse supported catalysts . In this approach, the catalytically active metal (usually single crystal) is used as a substrate upon which an oxide is deposited, presumably leaving patches of exposed metal. This approach has been used to study reduction of ceria, and methanation kinetics on Rh as promoted by deposited ceria, and chemisorption of various molecules. As stated above, it is generally assumed that thick enough ceria layers will continuously cover the metal substrate, placing a limit on the thickness of the ceria islands that can be achieved for an inverse supported catalyst. The different procedures used for the inverse and metal particle on bulk oxide model catalysts is expected to produce differences in thermal stability, morphology and surface structure which may have consequences for the reactivity of the model catalyst. 

First, the copolymer is automatically formed at the interface between the two immiscible polymers where it is needed to stabilize morphology. In contrast, when a compatibilizing copolymer is added as a separate entity to a polymer blend, it must diffuse to the polymer-polymer interface to be effective for promoting morphology stabilization and interphase adhesion. However, the added copolymer may prefer to form micelles as a separate phase that is useless for compatibilization. 

The application of this strategy to commercially important polyolefin multiphase systems to produce tuned and/or stabilized morphologies is certainly attractive. However, the required interfacial agents for this purpose have... 

The investigation of the compatibilization and crystallization of blends of polyolefins with a semiflexible LCP leads to the following conclusions the compatibilization of polyolefin/LCP blends has been realized successfully by the addition of ad hoc synthesized polyolefin-g-LCP copolymers. The compatibilization results into materials, characterized by a stabilized morphology, improved crystallization kinetics under nonisothermal and isothermal conditions, and enhanced mechanical properties. Moreover, polyolefin processability has been enhanced by the addition of LCP, even in the presence of compatibilizers. New high quality materials with improved processability have been produced by technologies, which are economic, friendly to the environment, and socially acceptable. 

Compatibilizers are utilized in polymer chemistry to improve the mechanical properties of multicomponent polymer blends. The process of compatibilization is meant to reduce polymer particle interfacial tension, facilitate chain dispersion, stabilize morphology against severe melt processing conditions, and enhance adhesion between two phases [93]. 

T (2003), The first lithium zeoUtic inorganic-organic polymer electrolyte based on PEG600, Li2PdCl4 and Li3Fe(CN)e, Part II, thermal stability, morphology and ion conduction mechanism , Electrochim Acta, 48,2227-2237. 

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