Propagation continuous

The propagation continues till the chain growth is stopped by the free-radical site being killed by some impurities or by a sheer termination process, or till there is no further monomer left for attack. 

AM propagation continues in a similar manner with nucleophilic attack hy hydroxyl end groups of polymer on protonated monomer (Eq. 7-32). Cyclic oligomer is minimized hy... 

It is believed that polymerization of hydrophobic monomers is initiated by free radicals in the aqueous phase and that the surface-active oligomers produced migrate to the interior of the emulsifier micelles where propagation continues. Monomer molecules dispersed in the water phase also solubilize by diffusing —to the expanding lamellar micelles. These micelles disappear as the polymerization continues and the rate may be measured by noting the increase in surface tension of llie system. 

Several mechanisms for NCA polymerization have been proposed. NCAs may undergo nucleophilic attack at the amino acid carbonyl with loss of carbon dioxide to provide an amino acid derivative, which subsequently reacts with a second NCA to give dimer 1 and carbon dioxide. Dimer 1 then reacts with a third NCA and propagation continues until a high molecular weight polymer 2 is obtained.15-81 This mechanism is frequently referred to as normal NCA polymerization (Scheme 1). 

The slow rate of copolymerization in acetone was related to the ease of termination of macroradicals by coupling. This coupling was hindered by the coiling of the macroradical chains in benzene, but propagation continued to take place since the monomers were able to pene-... 

Prior to nucleation the free radicals generated in the continuous phase propagate by reaction with dissolved monomer. Propagation continues stepwise until the radicals have reached the critical chain length for nucleation, jcr, at which point... 

Propagation continues until the radical is terminated. Termination occurs when two radical species meet and react either by coupling or by disproportionation as shown in Fig. 15.12. 

Another example of the matrix effect can be demonstrated by methyl methacrylate polymerization. Orlova et al. [65] postulated association of the growing radical with a molecule of the poly(methylmethacrylate) matrix. Propagation continues along the matrix at a reduced rate [66], yielding a... 

Propagation continues until the free radical reacts to form an inactive covalent bond. This can occur when the concentration of free radicals is high or when chain transfer agents are present. Termination can occur in many ways (i) the interaction... 

This process of propagation continues until another process intervenes and destroys the reactive center, resulting in the termination of the polymer growth. There may be several termination reactions depending on the type of the reactive center and the reaction conditions. For example, two growing radicals may combine to annihilate each other s growth activity and form an inactive polymer molecule this is called termination by combination or coupling ... 

ICM cells isolated by immunosurgery and plated on the MEF feeder layer were used to generate the ES lines (B). The resulting colonies were propagated and expanded. Following establishment of the hES lines, they can be propagated continuously in the undifferentiated state when grown on top of the MEF feeder layer (B, top). When re-... 

Convection cannot be fully suppressed in our experiment. In the direction of convection the diffusive transport of ions is sustained by a flow of the electrolyte and the front propagates continuously. Perpendicular to this direction (indicated by the red line in Fig. 8.8A, second panel) the ions are spread only by diffusion. Thus after initial homogeneous front spreading, an asymmetry in growth occurs. 

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