Thermochemically initiated polymerisation

Although the generation of free radicals may be faster by photolytic homolysis the propagation rate should be slower due to the low temperature of polymerisation ( — 20 to -l-15°C as compared to ca. 60°C when using thermochemical initiation). 

Fig. 2.13. Separation factor (a) versus column temperature in the chromatographic resolution of D,L-PA on L-PA imprinted polymers prepared by thermochemical initiation at 60/ 90/120°C (24 h at each temperature) using acetonitrile as porogen and photochemical initiation at 15°C for 24 h using dichloromethane as porogen. For the thermochemically polymerised material the mobile phase was 5% acetic acid in acetonitrile and for the photochemically polymerised material the mobile phase was acetonitrile/water/acetic acid 92.5/2.5/5 (v/v/v). From Sellergren et al. [27] and Sellergren and Shea [13].

Fig. 5.18. Effect of polymerisation and elution temperature on the enantiomer separation factor (a) in the separation of D- and L-PA on L-PA imprinted polymers. Polymers were prepared by thermochemical initiation at either 60 or 40°C using AIBN or ABDV respectively as initiators. The samples consisted of ca. 20 nmol of each of D- and L-PA and BOC-L-PA as void marker. Flow rate 0.5 mL/min. Mobile phase MeCN/acetic acid 95/5 (v/v). The columns were thermostatted by immersing them in a circulating water bath at the indicated temperature. From O Shannessy et al. [8].

Polymerisation technique. Thermochemical initiation at elevated temperatures or UV-photochemical initiation at low temperature. 

Thermochemical Aspects of the Initiation of Cationic Polymerisations by Organic Cations. Conflation of Two Unpublished Conference Contributions (1999)... 

Whilst it is rather hazardous to make any absolute conclusions on this basis, the method is useful for making comparative estimates, taking into account the effects of changes in conditions such as the polarity of the solvent. For example, by means of the thermochemical analysis corresponding to reaction (III) we can find an explanation of the well-known fact that EtsO+ does not initiate the polymerisation of alkenes. 

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