Copolymer multicomponent

Just as it is not necessary for polymer chains to be linear, it is also not necessary for all repeat units to be the same. We have already mentioned molecules like proteins where a wide variety of different repeat units are present. Among synthetic polymers, those in which a single kind of repeat unit are involved are called homopolymers, and those containing more than one kind of repeat unit are copolymers. Note that these definitions are based on the repeat unit, not the monomer. An ordinary polyester is not a copolymer, even though two different monomers, acids and alcohols, are its monomers. By contrast, copolymers result when different monomers bond together in the same way to produce a chain in which each kind of monomer retains its respective substituents in the polymer molecule. The unmodified term copolymer is generally used to designate the case where two different repeat units are involved. Where three kinds of repeat units are present, the system is called a terpolymer where there are more than three, the system is called a multicomponent copolymer. The copolymers we discuss in this book will be primarily two-component molecules. We shall discuss copolymers in Chap. 7, so the present remarks are simply for purposes of orientation. 

There are a number of physical properties of copolymers that are directly related to the multicomponent character of these materials and which an... 

Copolymer composition can be predicted for copolymerizations with two or more components, such as those employing acrylonitrile plus a neutral monomer and an ionic dye receptor. These equations are derived by assuming that the component reactions involve only the terminal monomer unit of the chain radical. The theory of multicomponent polymerization kinetics has been treated (35,36). 

EXA (exact) search retrieves the input stmcture and its stereoisomers, homopolymers, ions, radicals, and isotopicaHy labeled compounds. EAM (family) search retrieves the same stmctures as EXA, plus multicomponent compounds, copolymers, addition compounds, mixtures, and salts. SSS (substmcture) search uses a range of possible substituents and bonds in the input stmcture. CSS (closed substmcture) search is a more restrictive... 

As more complex multicomponent blends are being developed for commercial appHcations, new approaches are needed for morphology characterization. Often, the use of RuO staining is effective, as it is sensitive to small variations in the chemical composition of the component polymers. For instance PS, PC, and styrene—ethylene/butylene—styrene block copolymers (SEES) are readily stained, SAN is stained to a lesser degree, and PET and nylons are not stained (158,225—228). 

Synthetic polymers have become extremely important as materials over the past 50 years and have replaced other materials because they possess high strength-to-weight ratios, easy processabiUty, and other desirable features. Used in appHcations previously dominated by metals, ceramics, and natural fibers, polymers make up much of the sales in the automotive, durables, and clothing markets. In these appHcations, polymers possess desired attributes, often at a much lower cost than the materials they replace. The emphasis in research has shifted from developing new synthetic macromolecules toward preparation of cost-effective multicomponent systems (ie, copolymers, polymer blends, and composites) rather than preparation of new and frequendy more expensive homopolymers. These multicomponent systems can be "tuned" to achieve the desired properties (within limits, of course) much easier than through the total synthesis of new macromolecules. 

Thirdly, the multicomponent model was applied to the case of crystallization of a random A-B copolymer by Helfand and Lauritzen [127]. Their main result is that the composition of, 4 s and B s in the crystal is determined by kinetic, rather than equilibrium considerations the inclusion of excess B increases with growth rate. 

The interest in this type of copolymers is still very strong due to their large volume applications as emulsifiers and stabilizers in many different systems 43,260,261). However, little is known about the structure-property relationships of these systems 262) and the specific interactions of different segments in these copolymers with other components in a particular multicomponent system. Sometimes, minor chemical modifications in the PDMS-PEO copolymer backbone structures can lead to dramatic changes in its properties, e.g. from a foam stabilizer to an antifoam. Therefore, recent studies are usually directed towards the modification of polymer structures and block lengths in order to optimize the overall structure-property-performance characteristics of these systems 262). 

Surfactants used as lubricants are added to polymer resins to improve the flow characteristics of the plastic during processing they also stabilise the cells of polyurethane foams during the foaming process. Surfactants are either nonionic (e.g. fatty amides and alcohols), cationic, anionic (dominating class e.g. alkylbenzene sulfonates), zwitterionic, hetero-element or polymeric (e.g. EO-PO block copolymers). Fluorinated anionic surfactants or super surfactants enable a variety of surfaces normally regarded as difficult to wet. These include PE and PP any product required to wet the surface of these polymers will benefit from inclusion of fluorosurfactants. Surfactants are frequently multicomponent formulations, based on petro- or oleochemicals. 

As a first member of multicomponent multiblock copolymers with more than three different blocks, a PS- -PI- -PDMS- -P2VP copolymer was synthesized by Takahashi et al. [91]. As the constituents have different contrasts, the... 

SCHEME 2.57 Suzuki synthesis of multicomponent copolymers for RGB PLED display. (From Muller, C.D., Falcou, A., Reckefuss, N., Rojahn, M., Widerhirn, V., Rudati, P., Frohne, H., Nuyken, O.,... 

Most copolymers are heterogeneous in both molecular weight and composition. The latter of these arises from the mechanism of the copolymerisation (particularly at high conversion) and individual copolymer molecules differ slightly in their value of WA. Solutions of heterogeneous copolymers constitute multicomponent systems... 

A multicomponent dynamic RPA for incompressible diblock copolymer mixtures was developed by Akcasu [270]. The details of the approach may be found in the above reference. Here we recall some basic ideas dealing with the calculation of the dynamic structure factor S Q,t) for Rouse chains. 

We consider an incompressible (m-l-1) multicomponent mixture of polymers consisting of m different types of polymer chains within a matrix referred to as 0 . Components may be either homopolymers of a given chemical species or, e.g. homopolymer sections in block copolymers. Hydrogenated and deuterated species of the same homopolymer are considered as different components. In this context a diblock copolymer is a two-component polymer system. A mixture of partially protonated diblock chains hA-dB with deuterated diblock chains is consequently regarded as a four-component system. 

A variant of the zero average contrast method has been applied on a solution of a symmetric diblock copolymer of dPS and hPS in benzene [331]. The dynamic scattering of multicomponent solutions in the framework of the RPA approximation [324] yields the sum of two decay modes, which are represented by exponentials valid in the short time limit. For a symmetric diblock the results for the observable scattering intensity yields conditions for the cancellation of either of these modes. In particular the zero average contrast condition, i.e. a solvent scattering length density that equals the average of both... 

The two monomers enter into the copolymer in overall amounts determined by their relative concentrations and reactivities. The simultaneous chain polymerization of different monomers can also be carried out with mixtures of three or more monomers. Such polymerizations are generally referred to as multicomponent copolymerizations the term terpolymerization is specifically used for systems of three monomers. 

Kriesel JW, Sander MS, et al (2001) Block copolymer-assisted synthesis of mesoporous, multicomponent oxides by nonhydrolytic, thermolytic decomposition of molecular precursors in nonpolar media. Chemistry of Materials 13(10), 3554-3563... 

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