Chain growth polymerization experimental conditions

Several numerical tools have been developed and successfully applied to model the polymer microstructure as a function of monomer conversion and process conditions. In this chapter, these tools have been reviewed and applied to model the polymer microstmcture for both radical and catalytic chain-growth polymerizations, which are mechanistically the most important polymerization processes. Attention is focused both on the accurate simulation of the CLD and the PSD, following a multiscale modeling approach. The numerical tools discussed can be applied also for step-growth polymerizations provided that the model parameters are available or can be determined experimentally. 

All polymerization reactions can be categorized into two different types chain- and step-growth polymerization, which are incompatible in terms of monomer structure, experimental conditions, reaction rates, etc. In the past years, research concerning step-growth polymerization has been oriented to the preparation of new polyester materials by the combination of condensation and free radical techniques [28], as shown in Figure 3.10. 

Ionic mechanisms for the preparation of block copolymers are a very important tool of the synthetic polymer chemist. A feature of many homogeneous anionic polymerizations in solution is that termination can be avoided by careful control of experimental conditions. In fact, an infinite life of the active chain end is theoretically possible, and this has led to the term living polymers. Polymer carbanions can resume growth after the further addition of monomer. By changing the monomer composition, block copolymerization is readily initiated, and this process can be repeated. A major advantage of this... 

In a regular free radical polymerization, the initiation, chain growth, and chain termination steps occur concomitantly and repeatedly until both the monomer and/or the initiator are totally consumed. The choice of experimental conditions—and particularly that of temperature—is determined by the necessity to favor propagation over termination in order to achieve the complete consumption of monomer within reasonable reaction times. The expression of the rates of termination and propagation given below clearly indicate the reason for a slow initiation step in a regular free radical polymerization ... 

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