Copolymerization statistical

Statistical copolymers are formed when mixtures of two or more monomers are polymerized by a radical process. Many reviews on the kinetics and mechanism of statistical copolymerization have appeared1 9 and some detail can be found in most text books on polymerization. The term random copolymer, often used to describe these materials, is generally not appropriate since the incorporation of monomer units is seldom a purely random process. The... 

State Correlation Diagram (SCO) approach 27-8 statistical copolymerization see copolymerization statistical copolymers sea also copolymers definition 333... 

In this paper, the pseudo-kinetic rate constant method in which the kinetic treatment of a multicomponent polymerization reduces to that of a hcmopolymerization is extensively applied for the statistical copolymerization of vinyl/divinyl monomers and applications to the pre- and post-gelation periods are illustrated. 

Crosslihkinq Density Distribution. Let us consider the statistical copolymerization of vinyl/divinyl monomers without chain transfer to polymer for simplicity. In this case the crosslinking density p is defined as follows. 

Statistical copolymerization of ethylene glycol and 1,4-butanediol with dimethyl ter-ephthalate results in products with improved crystallization and processing rates compared to poly(ethylene terephthalate). Polyarylates (trade names Ardel, Arylon, Durel), copolymers of bisphenol A with iso- and terephthalate units, combine the toughness, clarity, and proce-sibility of polycarbonate with the chemical and heat resistance of poly(ethylene terephthalate). The homopolymer containing only terephthalate units is crystalline, insoluble, sometimes infusible, and difficult to process. The more useful copolymers, containing both tere- and isophthalate units, are amorphous, clear, and easy to process. Polyarylates are used in automotive and appliance hardware and printed-circuit boards. Similar considerations in the copolymerization of iso- and terephthalates with 1,4-cyclohexanedimethanol or hexa-methylene diamine yield clear, amorphous, easy-to-process copolyesters or copolyamides,... 

Statistical copolymerization occurs among ethylene and various a-olefins [Baldwin and Ver Strate, 1972 Cooper, 1976 Pasquon et al., 1967 Randall, 1978]. The reactivities of monomers in copolymerization generally parallel their homopolymerization behavior ethylene > propene > 1-butene > 1-hexene [Soga et al., 1989]. Table 8-7 shows monomer reactivity ratios for several comonomer pairs. 

Statistical copolymerization of SCLC-monomers with non-liquid crystalline monomers leads to dilution of the mesogenic units in the polymer, and (below a critical value) to the loss of the LC behavior of the polymer [47]. 

Kinsinger, J. B., and D. Colton A graphical synopsis of pair and triplet sequences in binary statistical copolymerization. Polymer Letters 3, 797 (196S). 

Methacrylates with pendant oxyethylene units (FM-19) were polymerized in a controlled way with metal catalysts in the bulk or in water. The catalytic systems include a bromide initiator coupled with Ni-2 for n = 2 (bulk, 80 °C)319 and CuCl for n = 7-8.246-320 The latter polymerization proceeded very fast in aqueous media at 20 °C to reach 95% conversion in 30 min and gave very narrow MWDs (MJMn =1.1 — 1.3). The fast reaction is attributed to the formation of a highly active, monomeric copper species com-plexed by the oxyethylene units. A statistical copolymerization of FM-19 (n = 7—8) and FM-20, a methacrylate with a oligo (propylene oxide) pendant group, led to hydrophilic/hydrophobic copolymers with narrow MWDs (MwIMn = 1.2).320... 

Scheme 7. Statistical copolymerization of St with NVC mediated by TEMPO [110]...

Table 1. Summary of statistical copolymerizations performed in the presence of various TEMPO derivatives ...

In simple cases of statistical copolymerizations, FjFj intersequence bonds occur per single intermonomer bond. The difference of the products H,i F, and us a measure of the... 

The large variation in polymerization rates among the various 2-oxazoline monomers has been exploited for the preparation of quasi-diblock copolymers, namely, gradient copolymers with a narrow and steep monomer gradient, by statistical copolymerization of selected monomer combinations exhibiting large differences in reactivity. Such a one-pot quasi-diblock copolymer synthesis was first demonstrated for the statistical copolymerization of 2-phenyl-2-oxazoline and a much less reactive 2-perfluoroalkyl-2-oxazoline [174]. This living CROP (in nitromethane at 120 °C initiated by methyl p-nitrobenzenesulfonate) revealed complete consumption of the 2-phenyl-2-oxazoline after 2 min with only minor incorporation of the fluorinated monomer. Continuation of the polymerization for another 40 h led to full conversion of the fluorinated monomer. The... 

It is amply evident that statistical copolymerization, both free radical and ionic, cannot produce an ideal network because of the unequal reactive ability of the comonomers in their competition for interaction with the active functional end of the growing polymer chain. However, using the so-caUed living anionic polymerization, it is possible to eliminate the competition between the comonomers by separating the stages of the formation of chain precursors and the formation of network per se, that is, chain crosslinking. Such an approach may be realized in two subsequent stages via anionic stepwise block polymerization of first styrene and then DVB. 

For example, monomer reactivity ratios for styime and methyl methacrylate in a free-radical copolymerization are r, = 0.5, rj = 0.44. This represents a statistical copolymerization. Contrast this with the anionic reaction, where r = 0.12 and 2 = 6.4, or the cationic reaction where r = 10.5 and Z2 = 0.1. Obviously, the propagation rates are no longer similar, and this is represented in Figure 5.3, where it can be seen that the anionic technique produces a copolymer rich in methyl methacrylate, whereas the cationic system leads to a copolymer with a high styrene content. 

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