Polymerization in the Gas Phase and under Pressure

If polymerization is carried out in the gas phase in the presence of heated metal surfaces, then even such unlikely monomers as hexachloro-butadiene can be polymerized to films on the metal surface. In this process, chlorine, among other products, is produced, and the chlorine/carbon ratio rises to 1 2. Therefore, the product cannot contain the same monomeric unit as the monomer. In a procedurally similar polymerization of tetra-fluoroethylene, for example, CF3 groups were found in the polymer. 

If the pressure is increased in a gas-phase polymerization, then the concentration is raised. Only after this step is the polymerization of many monomers thermodynamically possible (see Section 16.3.3). In order to obtain any noticeable effect, pressures of several hundred atmospheres are usually necessary. 

on the other hand, liquids are used, added pressure will not give any substantial increase in concentration, because of the limited compressibility. In order to influence the polymerization, pressures of at least several thousand atmospheres must be used with liquids. The following effects may be anticipated in different ranges of pressure (1 kbar 1000 atm)  

1-10 kbar Intermolecular forces are overcome (crystallization, increase in viscosity, etc.). 

10-100 kbar Changes in molecular and electronic structure, displacement of isomer equilibria. 

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