Statistical and alternating copolymers

This chapter is concerned primarily with the simultaneous polymerization of two monomers to produce statistical and alternating copolymers. The different monomers compete with each other to add to propagating centers, which can be radical or ionic. Graft and block copolymers are not synthesized by the simultaneous and competititive polymerization of two monomers. Each monomer undergoes polymerization alone. A sequence of separate, noncompetitive polymerizations is used to incorporate the different monomers into one polymer chain. The synthesis of block and graft copolymers and variations thereof (e.g., star, comb) are described in Secs. 3-15b-4, 3-15b-5, 5-4, and 9-9. 

When synthesizing random (statistical) and alternating copolymers two phenomena have to be kept in mind ... 

Polymer Blends, Statistical and Alternating Copolymers, Graft and Block Copolymers. 147... 

Statistical and Alternating Copolymers The different types of copolymers are listed below ... 

The present chapter is primarily concerned with the simultaneous polymerization of two monomers to produce random, statistical, and alternating copolymers. Graft copolymers and block copolymers are not synthesized by the simultaneous polymerization of two monomers. These are generally... 

Show the structures of statistical and alternating copolymers of vinyl chloride and ethyl acrylate. 

This study has been extended to copolymers of a-fluorostyrene with methyl acrylate because of our interest in the cotacticity of statistical and alternating copolymers of styrene and substituted styrenes with acrylates and methacrylates. The present paper covers the 300 MHz 20 MHz C- and 282 MHz F-NMR studies of... 

Alternating, statistical, and random copolymers are named by following the prefix poly with the names of the two repeating units. The specific type of copolymer is noted by inserting -alt-, -stat-, or -ran- in between the names of the two repeating units with -co- used when the type of copolymer is not specified, for example, poly(styrene-ofi-acrylonitrile), poly(styrene-i fat-acrylonitrile), poly(styrene-ran-acrylonitrile), and poly(styrene-co-acrylonitrile) [Wilks,... 

Metallocene catalysts show low r values, which allows easy incorporation of bulky cycloolefins into the growing copolymer chain. Surprisingly, the ethylene reactivity ratio in copolymerisation with cyclopentene in the presence of a (ThindCH2)2ZrCl2-based catalyst (r = 2.2) and in copolymerisation with norbornene in the presence of catalysts characterised by Cs and Ci symmetry (ri 3.4 and 3.1 respectively) is considerably lower than that for the copolymerisation of ethylene with propylene (r = 6.6 at 37 °C). Various catalysts produce copolymers of structures that are between statistical and alternating [468]. 

Statistical, random and alternating copolymers generally have properties which are intermediate to those of the corresponding homopolymers. Thus by preparing such copolymers it is possible to combine the desirable properties of the homopolymers into a single material. This is not normally possible by blending because most homopolymers are immiscible with each other. 

The molecular weight can be controlled by the ratio of the initator to the monomer, the molecular weight distribution by the type of polymerization (discontinuous or continuous) and the modality by single or multiple initiation. Sequential addition of different monomers leads to block copolymers with sharp or tapered transitions. In the presence of Lewis bases, statistical or alternating copolymers can be obtained. 

The properties of statistical, random, and alternating copolymers generally are intermediate to those of the parent homopolymers. 

Klumperman, B., 2012. Controlled composition statistical, gradient, and alternating copolymers. In Matyjaszewski. K., Moller, M. (Eds.), Polymer Science A Comprehensive Reference, vol. 6. Elsevier, Amsterdam, pp. 433-453. 

Composition and Functionality I Controlled Composition Statistical, Gradient, and Alternating Copolymers... 

In this section, some peculiarities of copolymerization conducted in CRP systems will initially be discussed and then examples of various types of copolymers will be provided. They will include statistical, gradient, and alternating copolymers, as well as block and graft copolymers. Some special systems will be also presented and they will include preparation of stereoblock copolymers, and various hybrid materials formed by either mechanistic transformation or by growing well-defined polymers from flat, colloidal, or irregular surfaces. 

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). 

The statistical, random, and alternating copolymers above describe sequence lengths of one, two, three, or at most several mers. This section treats cases where whole polymer chains are linked together to form still larger polymer structures (ll).lTiese structures have been variously named polymer alloys, or polymer blends, but the term multicomponent polymers is used here to describe this general class of materials. 

The product ri V2 shows whether statistical insertion (ri r2) or alternating one (n j"2 = 0) has occurred. The different catalysts produce copolymers with structures that are between statistical and alternating. 

The morphology of copolymers of two or more monomers with a statistical and alternating configuration of the different monomers is determined by the morphology of the related homopolymers. Occasionally, they can reveal a weak phase separation between the components. One example is SAN if the composition does not follow the azeotropic composition (76 mol% S, 24 mol% AN) see Fig. 1.3 and also Fig. 1.55 in Part 11. 

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