Polymerization nucleation period during

NUCLEATION. The polymer self-assembly theory of Oosawa and KasaP treats nucleation as a highly cooperative and unfavorable event. Their kinetic theory for nucleation permits one to obtain information about the size of the polymerization nuclei, provided that two basic assumptions can be satisfied experimentally. First, the rate of nuclei formation is assumed to be proportional to the ioth power of the protomer concentration, with io representing the number of protomers required to create the nucleus. Second, the treatment deals only with that period during which the polymerization rate greatly exceeds the rate of protomer loss from the polymers (i.e., the initial stage of polymerization when the protomer concentration is the highest). 

Polymerization of G-actin in vitro Is marked by a lag period during which nucleation occurs. Eventually, a polymerization reaction reaches a steady state In which the rates of addition and loss of subunits are equal (see Figure 19-10). 

In the semibatch experiments, the particle size distributions of the final latexes were affected by the residual surfactant in the seed latex, which tended to facilitate homogeneous nucleation during the entire feed period. The monomer feedrate determined the polymerization rate and had little effect on copolymer composition. The polymer compositions for the runs with different monomer feeding modes tended to be identical at very low feedrate. 

Regarding N, it has been reported [116] that this parameter reaches a maximum during the nucleation stage if the polymerization is performed below the CMC, because the low availability of surfactant causes limited coagulation. On the other hand, N tends to increase in this stage when the surfactant concentration is above the CMC. During interval II, N is typically assumed to be constant, but some authors have reported that this parameter increases in this period [138, 150-152]. The subject is still a matter of debate due to the limitations of certain particle sizing techniques [125, 129, 130]. 

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