Polymer blends, copolymers compatibilization

Macromonomers afford a powerful means of designing a vast variety of well-defined graft copolymers. These species are particularly useful in the field of polymer blends as compatibilizers and/or stabilizers (surfactants). When macromonomer itself is an amphiphilic polymer, then its polymerization in water usually occurs rapidly as a result of organization into micelles. In copolymerizations, important factors for macromonomer reactivity are the thermodynamic repulsion or incompatibility between the macromonomer and the trunk polymer and its partitioning between the continuous phase and the polymer particles [4,5]. 

Polymer blends and compatibilizing agents historically have been the subject of a wide variety of studies and an extensive body of literature on these materials exists. Without specific chenucal interactions between dissimilar polymers, most polymer mixtures tend to phase separate due to the unfavorable entropy of mixing between the polymer chains. Efforts to control or retard the phase separation process have led to the research and development of compatibilizing agents for polymer blends. For a variety of systems the dispersed phase particle size has been found to decrease with increasing copolymer concentration. Above a critical concentration of copolymer, the size of the dispersed phase remains constant. 

Grading systems, for flax fiber, 77 617 Gradual failures, 26 981 Graduate students, role in facilitating research partnerships, 24 383 Graft copolymerization, 20 327. See also Graft polymerization Graft copolymers, 7 650-654 20 391 compatibilization efficiency of, 20 338 formation of, 23 395 in polymer blends, 20 324—325 in reactive compatibilization,... 

In general, graft copolymers play often a role as compatibilizer in polymer blends (see Sect. 5.5). 

Short block copolymers with well defined number of units in the blocks could be applied as selective absorbents, compatibilizers for polymer blends, components for polymeric membranes, etc. 

Compatibilizer Polymers. ABS copolymers that are functionalized may act as a compatibilizer for other polymer blends. These types are grafted in the same way as polymers dealt with above. 

This exponential dependence leads to the dramatic compatibilization effect of block copolymers in immiscible polymer blends. Leibler (1988) noted that for strongly incompatible systems, the exponential increase of Ay with h only occurs for small c. At larger copolymer content, the reduction in interfacial area per block causes a slower increase in Ay (i.e. reduction in y). 

An important group of surface-active nonionic synthetic polymers (nonionic emulsifiers) are ethylene oxide (block) (co)polymers. They have been widely researched and some interesting results on their behavior in water have been obtained [33]. Amphiphilic PEO copolymers are currently of interest in such applications as polymer emulsifiers, rheology modifiers, drug carriers, polymer blend compatibilizers, and phase transfer catalysts. Examples are block copolymers of EO and styrene, graft or block copolymers with PEO branches anchored to a hydrophilic backbone, and star-shaped macromolecules with PEO arms attached to a hydrophobic core. One of the most interesting findings is that some block micelle systems in fact exists in two populations, i.e., a bimodal size distribution. 

PMMA backbone, which can control the segmental dispersion of PMMA and EPR segments in the range from 1 nm to 100 nm (Fig. 23). Moreover, it was clearly demonstrated that the PMMA-g-EPR graft copolymer with 38.1 wt% of EPR content worked efficiently as a compatibilizer for an EPR/PMMA polymer blend (Fig. 24). DSC analysis revealed the effect of the EPR branch on the Tg value of the PMMA backbone and a little incorporation of an EPR branch caused a large deviation of the Tg value from the homo-PMMA. 

Chain functionalized polymers or graft copolymers are of great technological importance. They are used as compatibilizing agents for immiscible polymer blends (8) and adhesive layers between polymer-polymer co-extruded surfaces (8). Currently, of all polymers sold, about 30% are in the form of compatibilized immiscible blends (9-12). Next we discuss a few examples of chain functionalization. 

Marie M, Macosko CW (2002) Block copolymer compatibilizers for polystyr-ene/poly(dimethylsiloxane) blends. J Polym Sci Part B Polym Phys 40(4) 346-357... 

SCFT today is one of the most commonly used tools in polymer science. SCFT is based on de Gennes-Edwards description of a polymer molecule as a flexible Gaussian chain combined with the Flory-Huggins "local" treatment of intermolecular interactions. Applications of SCFT include thermodynamics of block copolymers (Bates and Fredrickson, 1999 Matsen and Bates, 1996), adsorption of polymer chains on solid surfaces (Scheutjens and Fleer, 1979,1980), and calculation of interfacial tension in binary polymer blends compatibilized by block copolymers (Lyatskaya et al., 1996), among others. 

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