Adiabatic calorimetry polymerization

The ideal addition polymerization is one in which there are no termination or transfer reactions, initiation (betaine formation) is instantaneous and kp lies between 102 and 104 1 moP1 s-1. Such polymerizations can be conveniently followed by adiabatic calorimetry. At very high initiator concentrations it should be possible to measure the rates of the first monomer additions and isolate zwitterion oligomers for study. Cyanoacrylate polymerizations initiated by phosphine satisfy all these conditions except the last. kp is 1051 mol-1 s-1 at —78°C. However, cyanoacrylates with more bulky alkyl substituents may have smaller kp s. It is possible that methylene malonate polymerizations may fulfil the above requirements. 

The kinetics of the polymerization of indene in CH2CI2 solution, initiated with cumyl methyl ether and cumyl chloride, in the presence of TiCl3Bu, at variable temperatures (0 to —62 °G), have been investigated by adiabatic calorimetry under vacuum. The results may be explained by a propagation involving ionic active centers, as in conventional carbocationic polymerization.312... 

In this section experimental results are discussed, concerned with analyses of melting and crystallization kinetics, as well as reversibility of the phase transition. The frame of the discussion is set by Fig. 3.76, which will be supported by experimental data on poly(oxyethylene). The thermal analysis tools involved are TMDSC, optical and atomic-force microscopy, DSC, adiabatic calorimetry, and dilatometry. Most of these techniques are described in more detail in Chap. 4. Results from isothermal crystallization, and reorganization are attempted to be fitted to the Avrami equation. This is followed by a short remark on crystallization regimes and finally some data are presented on the polymerization and crystallization of trioxane crystals. 

Adiabatic calorimetry, radical heterophase polymerization, data acquisition, 427 mass balances, parameter estimation... 

The thermodynamic properties of several cyanoacrylate polymers have been determined using precision adiabatic and isothermal calorimetry (52-55). The Gibbs free energy AGq estimated from the enthalpy Aifo and entropy ASq of the bulk polymerization of various monomers showed that polymerization is thermodynamically feasible over the temperature range -270 to - -160°C at standard pressure. Ceiling temperatures Tc for polymerization were derived from the thermodynamic data and represent the upper temperature limit of polymerization. 

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