PEGylation rate constants

Figure 24.7 shows an example of the nse of the model prediction for optimizing the PEGylation step. With the rate constants shown, the PEG/GHA molar ratio was varied from 7 to 11 and the total amonnt of PEG-GHA(4-6) was compnted as a fnnction of time. As can be seen, the overall yield to the desired PEG-GHA species (in mole% of total) increases significantly from molar ratio of 7 to abont 9 but not mnch after that. Also for the molar ratio of 9 and higher, the reaction is essentially complete in 90 minntes. 

Figure 9.19 Use of Damkholer number (Da, ratio of mixing and process characteristic time) for correlation of data. As the pseudo-first order constant used to model the particle formation rate, is not always known, but is obviously the same for each polymer, (Da/ly) is used to correlate the different sets of data (referring to particles produced using different mixing intensity and different initial polymer concentration in the same mixer) quench volumetric ratio = 0.2. Upper graph PEGylated copolymer in acetone at different inlet concentrations and mixing intensities in Tee mixer (d. = 1 mm). Lower graph comparison of different polymers and solvents (fiUed symbols, acetone open symbols, THF) in CIJ mixer (dj = 1 mm) > PCL = 80,000 , PCL = 14,000 A, PEGylated copolymer O, PHDCA (symbols as in Figure 9.6).

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