Multiphase polymers copolymers

In general, block copolymers are heterogeneous (multiphase) polymer systems, because the different blocks from which they are built are incompatible with each other, as for example, in diene/styrene-block copolymers. This incompatibility, however, does not lead to a complete phase separation because the polystyrene segments can aggregate with each other to form hard domains that hold the polydiene segments together. As a result, block copolymers often combine the properties of the relevant homopolymers. This holds in particular for block copolymers of two monomers A and B. 

In general, there is a paucity of information on the relationship between polymer structure and degradation kinetics. This becomes especially critical in multiphase polymers like heterophasic copolymers, thermoplastic elastomers and blends. This review should stimulate research in this important area, which could ultimately lead to polymers with better photo-thermal and radiation resistance as well as more effective stabilizers. 

With better understanding of the mechanism of degradation and stabilization, there undoubtedly will be an increased effort to produce polymers with greater photothermal/radiation resistance and also more effective stabilizers to achieve this end. Thus, the study of degradation and stabilization aspects of ethylene-propylene copolymers and their blends (and generally of multiphase polymer blends) appears to be both intellectually stimulating and of practical importance. 

This review has illustrated various properties of multiphase polymer systems obtained from computer simulation. Three modeling techniques - atomistic, coarse-grained, and atomistic-continuum modeling - are applied to miscibility of homopolymer/copolymer and homopolymer/homopolymer blends, compat-ibilizing effect of block copolymers, and mechanical properties of semicrystalline polymers, respectively. 

As an example of atomistic modeling for multiphase polymer systems, miscibility of PEO/SAA and PS/PVME blends are investigated. For PEO/SAA blends, the effect of sequence distribution of copolymer on the miscibility of blends is analyzed by calculating the interaction energy parameters. It is observed that both the sequence distribution and the composition significantly affect the degree of miscibility. For a fixed composition, there exists an optimal range of sequence distribution for which the blend system is miscible. The sequence distri-... 

The interfaces in multiphase segmented copolymers are diffuse. Furthermore, in the case of the purified polymer systems being studied, there is no evidence for a differentiable trapping mechanism in the interfacial regions. The frequency-dependent complex permittivity e is calculated from (26) ... 

Colloidal and Morphological Behavior of Block and Graft Copolymers" Molau, G. E., Ed. Plenum Press New York, 1971. "Multiphase Polymers" Cooper, S. L. Estes, G. M., Eds. ADVANCES IN CHEMISTRY SERIES No. 176, American Chemical Society Washington, D.C., 1979. 

Homogeneous single-phase polyblends are very rare. Liquid-liquid phase separation of optically homogeneous polyblends of a styrene/acrylonitrile copolymer with poly (methyl methacrylate) has been studied by L. P. McMaster. A quantitative test method of the dynamic mechanical properties of multiphase polymer systems was developed by L. Bohn. He was able to demonstrate the correlation between shear modulus and gel volume of brittle polymers... 

Interfacial effects on multiphase polymer systems have been of interest to polymer scientists. Apphcation of this strategy to commercially important polyolefin multiphase systems to produce tuned and/or stabilized morphologies is certainly attractive. Recently, polyolefin block copolymers have been introduced commercially and may be effective in controlling the morphology of related multiphase polyolefin systems, such as hiPP and TPO. 

Adhesion of thermodynamically incompatible polymers is of current interest because of its implications for developing new multiphase polymer materials and for recycling of mixed plastic wastes. Many elegant experiments have been reported in which various types of copolymer are introduced at the interface as putative compatibilizers. The interface may be strengthened as a result of interdiffusion and roughening on a nanoscale. 

Compatibilisers are intentional additives, incorporated into multi-component, multiphase polymer systems. They are usually block copolymers, whose segments are soluble in different components of the mixture. Compatibilisers can be reactive (if they form bonds with one of the polymers in the mixture) with reactive groups like acrylic or methacrylic, maleic anhydride, or glycidyl methacrylate), or non-reactive. The main classes of compatibilisers are (a) modified PE and polypropylene-styrene containing polymers, (b) macromonomers, (c) silane-modified materials. 

Multiphase polymer blends are of major economic importance in the polymer industry. The most common examples involve the impact modification of a thermoplastic by the microdispersion of a rubber into a brittle polymer matrix. Most commercial blends consist of two polymers combined with small amounts of a third, compatibilizing polymer, typically a block or graft copolymer. 

Most utility polymeric articles available today contain multiphase polymeric systems comprised of semi-crystalline polymers, copolymers, polymers in solution with low molar mass compounds, physical laminates or blends. The primary aim of using multicomponent systems is to mould the properties available from a single polymer to another set of desirable material properties. The property development process is complex and depends not only on the properties of the polymer(s) and other components but also on the formation process of the system which determines the developed microstmcture, and component interaction after formation. Moreover, the process of polymer composite formation and the stability of the composite is a function of environmental parameters, e.g., temperature, presence of other species etc. The chemical composition and some insight into the microscopic structure of constituents in a polymer composite can be directly obtained using Infrared (IR) spectroscopy. In addition, a variety of instrumental and sampling configurations for spectroscopic measurements combine to make irrfra-red spectroscopy a versatile characterization technique for the analysis of the formation processes of polymeric systems, their local structure and/or dynamics to relate to property development under different environmental conditions. In particular, Fourier transform infrared (FTIR) spectroscopy is a well-established technique to characterize polymers [1, 2]. 

Multiphase or multicomponent polymers can clearly be more complex structurally than single phase materials, for there is the distribution of the various phases to describe as well as their internal structure. Most polymer blends, block and graft copolymers and interpenetrating networks are multiphase systems. A major commercial set of multiphase polymer systems are the toughened, high impact or impact modified polymers. These are combinations of polymers with dispersed elastomer (rubber) particles in a continuous matrix. Most commonly the matrix is a glassy amorphous thermoplastic, but it can also be crystalline or a thermoset. The impact modified materials may be blends, block or graft copolymers or even all of these at once. 

Many of the studies of multiphase polymers are conducted on unsaturated rubbers which are adequately stained by osmium tetroxide, which reveals the nature of the dispersed phase domains. Polymers with activated aromatic groups have been selectively stained by reaction with mercuric trifluoroacetate (Section 4.4.8). Hobbs [262] has successfully used this technique to provide contrast in blends of poIy(2,6-dimethyl-l,4-phenylene oxide) and Kraton G (SBS block copolymer). Although this stain is effective in enhancing contrast, a drawback of the method is that the material is not hardened or fixed by the stain. 

Suresh I. Kattimuttathu, Sitaramam S. Bhamidipalli, and Raju V. S. N. Kothapally. Effect of copolymer composition on the dynamic mechanical and thermal behaviour of butyl acrylate-acrylonitrile copolymer. Macromol. Mater. Eng. 288 no. 12 (2003) 980-983. Thomas Sabu, Boudenne Abderrahim, Ibos Laurent, and Candeau Yves. Physical, thermophysical and interfacial properties of multiphase polymer systems State of art, new challenges and opportunities. In Handbook of multiphase polymer systems, Abderrahim Boudenne, Laurent Ibos, Yves Candau, and Sabu Thomas (eds.), 1-12. Chichester, UK Wiley, 2011. 

Multiphase Polymer Systems Micro- to Nano structural Evolution in Advanced Technologies is a fundamental reference work on copolymers, polymer blends, polymer composites, interpenetrating polymers, and layered polymer/metal structures, covering aspects of science, engineering, technology, and application. 

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