Phase separation copolymerization with

Copolymerizations of benzvalene with norhornene have been used to prepare block copolymers that are more stable and more soluble than the polybenzvalene (32). Upon conversion to (CH), some phase separation of nonconverted polynorhornene occurs. Other copolymerizations of acetylene with a variety of monomers and carrier polymers have been employed in the preparation of soluble polyacetylenes. Direct copolymeriza tion of acetylene with other monomers (33—39), and various techniques for grafting polyacetylene side chains onto solubilized carrier polymers (40—43), have been studied. In most cases, the resulting copolymers exhibit poorer electrical properties as solubiUty increases. 

In contrast to ionic chain polymerizations, free radical polymerizations offer a facile route to copolymers ([9] p. 459). The ability of monomers to undergo copolymerization is described by the reactivity ratios, which have been tabulated for many monomer systems for a tabulation of reactivity ratios, see Section 11/154 in Brandrup and Immergut [14]. These tabulations must be used with care, however, as reactivity ratios are not always calculated in an optimum manner [15]. Systems in which one reactivity ratio is much greater than one (1) and the other is much less than one indicate poor copolymerization. Such systems form a mixture of homopolymers rather than a copolymer. Uncontrolled phase separation may take place, and mechanical properties can suffer. An important ramification of the ease of forming copolymers will be discussed in Section 3.1. 

The formation mechanism of structure of the crosslinked copolymer in the presence of solvents described on the basis of the Flory-Huggins theory of polymer solutions has been considered by Dusek [1,2]. In accordance with the proposed thermodynamic model [3], the main factors affecting phase separation in the course of heterophase crosslinking polymerization are the thermodynamic quality of the solvent determined by Huggins constant x for the polymer-solvent system and the quantity of the crosslinking agent introduced (polyvinyl comonomers). The theory makes it possible to determine the critical degree of copolymerization at which phase separation takes place. The study of this phenomenon is complex also because the comonomers act as diluents. 

A detailed description of AA, BB, CC step-growth copolymerization with phase separation is an involved task. Generally, the system we are attempting to model is a polymerization which proceeds homogeneously until some critical point when phase separation occurs into what we will call hard and soft domains. Each chemical species present is assumed to distribute itself between the two phases at the instant of phase separation as dictated by equilibrium thermodynamics. The polymerization proceeds now in the separate domains, perhaps at differen-rates. The monomers continue to distribute themselves between the phases, according to thermodynamic dictates, insofar as the time scales of diffusion and reaction will allow. Newly-formed polymer goes to one or the other phase, also dictated by the thermodynamic preference of its built-in chain micro — architecture. 

Equations for Step-Growth Copolymerization with Phase Separation... 

An example of this case is a vinyl (A2 ) - divinyl (A4) polymerization. The assumption of an ideal polymerization means that we consider equal initial reactivities, absence of substitution effects, no intramolecular cycles in finite species, and no phase separation in polymer- and monomer-rich phases. These restrictions are so strong that it is almost impossible to give an actual example of a system exhibiting an ideal behavior. An A2 + A4 copolymerization with a very low concentration of A4 may exhibit a behavior that is close to the ideal one. But, in any case, the example developed in this section will show some of the characteristic features of network formation by a chainwise polymerization. 

The competition between the phase separation and crosslinking processes opens up the possibility of controlling pattern formation and the structure of the resulting material by varying the reaction temperature and the blend composition. There is considerable effort to modify the useful properties of elastomers by introducing a coagent that is copolymerized with the elastomer and contributes positively... 

N-isopropylacrylamide 1 is added to the polymerization mixture to increase hydro-phobicity of the monolith required for the separations in reversed phase mode. Vinylsulfonic acid 12 provides the chargeable functionalities that afford electroosmo-tic flow. Since the gelation occurs rapidly already at the room temperature, the filling of the channel must proceed immediately after the complete polymerization mixture is prepared. The methacryloyl moieties attached to the wall copolymerize with the monomers in the liquid mixture. Therefore, the continuous bed fills the channel volume completely and does not shrink even after all solvents are removed. Fig. 6.8 also shows scanning electron micrograph of the dry monolithic structure that exhibits features typical of macroporous polymers [34],... 

Alkylene 4,4 -Biphenyldicarboxylate/PTME 4,4 -Biphenyldicarbox-ylate Copolymers. Tetramethylene 4,4 -biphenyldicarboxylate/PTME 4,4 -biphenyldicarboxylate copolymers containing 20 and 30% tetra-methylene 4,4 -biphenyldicarboxylate were prepared without incident (Table VI). Attempts to prepare similar copolymers containing 40 and 50% tetramethylene 4,4 -biphenyldicarboxylate led to problems with phase separation in the melt during the copolymerizations. 

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