Block copolymers, nomenclature

The nomenclature system used here is that suggested by Ceresa (/) and adopted in the Encyclopedia of Polymer Science and Technology. A block copolymer can be represented by ... 

Let us now turn to the stateof the art of nomenclature in multi-component polymers (2-7). Many simple materials already have precise names. For example, poly(butadiene-b-styrene) is represented by the structure in Equation 1, where A stands for the butadiene mer and B represents the styrene mer in block copolymer arrangement, as indicated by the small -b-. 

Block Copolymers. As illustrated in Figure 3, block copolymers represent a special kind of graft copolymer, i.e., polymer n + 1 is always attached at the end of polymer n. This mode of attachment will be designated as a line (L) junction. (The writer is indebted to Charles E. Rogers of Case Western Reserve University for suggesting L-junction nomenclature.) A simple, two-component block copolymer can then be represented by ... 

Various blocks may even be statistical or periodical copolymers. Block copolymers are also formed by the combination of suitable end groups of homopolymers of various monomers. This may occur either by direct combination or by means of a bonding group. According to the IUPAC nomenclature [3] these copolymers are designated as polyMl-A/or/ -polyM2-/>/c>cA --polyMj-6/ocfc-polyM... 

Graft copolymers like 1-27 are named aspoly(A-g-B) with the backbone polymer mentioned before the branch polymer. Examples are poly(ethylene- -styrene) or starch-g-polystyrene. In block copolymer nomenclature b is used in place of g and the polymers are named from an end of the species. Thus the triblock macromolecule 1-53... 

I. .5.4 Block Copolymer Molecular Architecture Thermoplastics and Thermosets Hlasioniers, Fibers, and Plastics Miscellaneous Terms Polymer Nomenclature... 

Experiments have been carried out on essentially monodisperse polystyrene, either homopolymers (normal or deuterated) or isotopically-labelled block-copolymers. These materials have been used alone or blended. Sample nomenclature and average molecular weights, as determined by SEC, are presented in Tables 1 and 2. Isotopically-labelled block copolymers, either linear or 6-arm stars, synthesized by anionic polymerization, were kindly provided by Dr. L. J. Fetters (Exxon Research and Engineering Company). 

Graft copolymers of A and B monomers are named poly(A-g-B) or poly -graft-po y B with the backbone polymer -(-A-) - mentioned before the branch polymer. Some examples are poly(ethylene-g-styrene) or polyethylene-gra/it-polystyrene and starch-gra/ir-polystyrene. In the nomenclature of block copolymers, b or block is used in place of g or graft, e.g. poly(A-b-B) or poly A-block-poly B, poly(A-6-B-6-A) or poly A-6/ocik-poly B-blocic-po y A, poly(A-b-B-6-C) or poly A-6/ock-poly B-block-po y C), and so on. Thus the triblock polymer (XXIV) is called poly(styrene-6-butadiene-b-styrene) or polystyrene-6/ocA -polybutadiene-6/ock -polystyrene. When such polymers are articles of commerce they are usually designated by the monomer initials thus, structure (XXIV) would be named SBS block copolymer. 

The International Union of Pure and Applied Chemistry (lUPAC) formed a Subcommission on Nomenclature of Macromolecules in 1952 and has proceeded to study various topics related to cyclic polymers, blends, composites, cross-linked polymers, block copolymers, etc. lUPAC periodically reports its decisions regarding nomenclature (1, 7, and ). Even so, these rules have not been generally accepted for common polymers by the majority of those in polymer science. 

The nomenclature poly (M1-6-M2) is used where Mj and M2 are the monomer names for example poly (styrene-b-butadiene). To make block copolymers, the polymer chains must have the ability to propagate [living polymers) when the first monomer is replaced by the second. In conventional addition polymerisation the chain termination and transfer processes make the lifetime of a growing polymer chain too short. Consequently, special ionic polymerisation catalysts were developed. A fixed number of di-anions such as [C6H5CHCH2CH2CHC6H5] are introduced into an inert solvent. These propagate from both ends if a suitable monomer is introduced. As there are no termination or transfer reactions, once the first monomer has been consumed, a second monomer can be introduced to produce a triblock copolymer such as styrene-butadiene-styrene. Each block has a precisely defined molecular weight. These materials undergo phase separation (Chapter 4) and act as thermoplastic rubbers. 

The prefix g describes graft copolymers and the prefix b describes block copolymers. In this system of nomenclature, the first polymer segment corresponds to the homopolymer or copolymer that was formed during the first stage of the synthesis. Should this be a graft copolymer then this will represent the backbone polymer. For instance, if polystyrene is graft copolymerized with polyethylene, the product is called poly(ethylene-g-styrene). A more complex example can be poly (butadiene-co-styrene-g-acrylonitrile-co-vinylidine chloride). Similarly, examples of block copolymers would be poly(acrylonitrile- -methyl methacrylate) or poly(methyl methacry late- -acry lonitrile). 

The nomenclature prevalent in the literature refers to segmented polyurethanes, rather than block copolymer urethanes. Not all types of polyurethanes form segmented, and hence block-copolymer-type structures, however. 

The most convenient polymeric surfactants are those of the block and graft copolymer type. A block copolymer is a linear arrangement of blocks of variable monomer composition. The nomenclature for a diblock is poly-A-block-poly-B, and for a triblock it is poly-A-block-poly-B-poly-A. One of the most widely used triblock polymeric surfactants are the Pluronics (BASF, Germany) or Synperordc PE (ICI, U.K.), which consists of two poly-A blocks of poly(ethylene oxide) (PEO) and one block of poly(propylene oxide) (PPO). Several chain lengths of PEO and PPO are available. More recently, triblocks of PPO-PEO-PPO (inverse Pluronics) became available for some specific applications. 

As polyurethane intermediates react rapidly and stoichiometrically with each other, a system of nomenclature is widely used to describe the structure of individual block copolymers. Suppose, for example, a typical polyurethane consisted of polycaprolactone,4,4 -diphenylmethane diisocyanate, and 1,4-butane diol, present in the molar ratio 1 3 2, then such a polymer is reported as a 1 3 2 block copolymer and this represents a simple, convenient and rapid method of identifying the basic urethane polymer structure. The ratio of each component in the block copolymer has a dramatic effect on its properties, as shown by the data in Table 2.2. 

The previous two chapters briefly described a number of two-polymer combinations polymer blends, blocks, grafts, and IPNs. A few somewhat more complicated systems were alluded to blends of a homopolymer with a block copolymer, or a mixture of a graft copolymer with one or both homopolymers. This chapter will explore some of the more complex (and interesting) structures, and provide a nomenclature scheme where one now does not exist. ... 

The nomenclature of the block copolsrmers is as follows A ByCz is a block copolymer composed of the blocks A, B, and C, where subscripts denote the weight fraction (%) and M is the number-averaged overall molecular weight (kg/mol). Heteroarm star terpolymers are indicated by an asterisk (A ByCz ). The morphological schemes are presented in such a way that the typical colors found in tern images of correspondingly stained samples are used (Table 1). 

The new system also provides a structure-based alternative to source-based nomenclature for copolymers. Irregular polymers, oligomers, or blocks are named by placing the prefix poly before the structure-based names of the constitutional units the latter are collectively enclosed in parentheses, with the names of the component constitutional units separated by solidi (oblique strokes). 

The classi cation of copolymers according to structural types and the nomenclature for copolymers have been described previously in Chapter 1. The present chapter is primarily concerned with the simultaneous polymerization of two monomers by free-radical mechanism to produce random, statistical, and alternating eopolymers. Copolymers having completely random distribution of the different monomer units along the copolymer chain are referred to as random copolymers. Statistical copolymers are those in which the distribution of the two monomers in the chain is essentially random but in uenced by the individual monomer reactivities. The other types of copolymers, namely, graft and block copolymers, are not synthesized by the simultaneous polymerization of two monomers. These are generally obtained by other types of reactions (see Section 7.6). 

Fig. 10.1 Nomenclature for linear and branched block copolymer architectures of diblock and...

In the international nomenclature, -co-, -alt-, -b-, -g- are often inserted between two monomers to represent random copolymerization, alternating copolymerization, block copolymerization, and graft copolymerization, respectively. In random copolymer names, the former is the main monomer, and the latter is the secondary monomer. In block copolymer names, the order of monomers represents the order of polymerization, whereas in graft copolymer names, the former is the main chain and the latter is the branched chain. 

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