Monomer consumption

Solution polymers are the second most important use for acryflc monomers, accounting for about 12% of the monomer consumption. The major end use for these polymers is in coatings, primarily industrial finishes. Other uses of acryflc monomers include graft copolymers, suspension polymers, and radiation curable inks and coatings. 

The propagation rate is governed by the concentrations of growing chains [M—] and of monomers [M]. Since this is in effect the rate of monomer consumption it also becomes the overall rate of polymerisation... 

Application of a steady state approximation (that / t = / j, eq. 2) and a long chain approximation (negligible monomer consumption in the initiation or reinitiation steps) provides a number of useful relationships. ... 

If chains are very short we must include an additional term in the numerator for monomer consumption in the initiation step (eq. 30) ... 

Even in the absence of added transfer agents, all polymerizations may be complicated by transfer to initiator (Sections 3.2.10 and 3.3), solvent (Section 6.2.2.5), monomer (Section 6.2.6) or polymer (Section 6.2.7). The significance of these transfer reactions is dependent upon the particular propagating radicals involved, the reaction medium and the polymerization conditions. Thiol-ene polymerization consists of sequential chain transfer and reinitiation steps and ideally no monomer consumption by propagation (Section 7.5.3). 

The instantaneous rate of monomer consumption in binary copolymerization is then given by eq. 62 ... 

Changes of the partition coefficient with monomer consumption in the diluent phase. 

Tanlak found the following relations for the propagation reactions and monomer consumption ... 

The propagation reaction is a more mechanistic version of Equation (13.1) and accounts for most of the monomer consumption. The growth of the chain can be stopped by chain transfer, the simplest form of which is chain transfer to monomer ... 

The initiation and termination steps may also come in several varieties, but they will have little effect on overall chain composition provided the chains are long. The monomer consumption rates are... 

The polymerizations initiated by HMDS and N-TMS amines usually complete within 24 h at ambient temperature with quantitative monomer consumption. These polymerizations in general are slower than those mediated by Deming s Ni(0) or Co (0) initiators (about 30-60 min at ambient temperature) [19, 24, 25], but are much faster than those initiated by amines at low temperature or using amine hydrochloride initiators [20]. These HMDS and N-TMS amine-mediated NCA polymerizations can also be applied to the preparation of block copolypeptides of defined sequence and composition [22]. This organosilicon-mediated NCA polymerization, which was also shown by Zhang and coworkers to be useful for controlled polymerization of y-3-chloropropanyl-L-Glu NCA [43], offers an advantage for the preparation of polypeptides with defined C-terminal end-groups. 

The role of reactive centers is performed here by free radicals or ions whose reaction with double bonds in monomer molecules leads to the growth of a polymer chain. The time of its formation may be either essentially less than that of monomer consumption or comparable with it. The first case takes place in the processes of free-radical polymerization whereas the second one is peculiar to the processes of living anionic polymerization. The distinction between these two cases is the most greatly pronounced under copolymerization of two and more monomers when the change in their concentrations over the course of the synthesis induces chemical inhomogeneity of the products formed not only for size but for composition as well. 

The kinetic description of chain branching is complex, because the probability of a chain branching event depends on many things that we cannot simplify for the model we are developing. Suffice it to say that chain branching slows down the polymerization process. This is because any reaction occurring between chains does not incorporate the free monomer, leading to a reduced rate of monomer consumption. 

The detailed kinetics of the -CL polymerization showed that termination and chain transfer did not occur and the monomer consumption followed a... 

Block copolymer synthesis from living polymerization is typically carried out in batch or semi-batch processes. In the simplest case, one monomer is added, and polymerization is carried out to complete conversion, then the process is repeated with a second monomer. In batch copolymerizations, simultaneous polymerization of two or more monomers is often complicated by the different reactivities of the two monomers. This preferential monomer consumption can create a composition drift during chain growth and therefore a tapered copolymer composition. 

The usual analysis gives for the rate of monomer consumption... 

There is also here a simple calculation whereby it is shown that propagation by paired cations cannot explain the monomer consumption which is attributed by this author to propagation by the ester. 

However, the discovery with the most far-reaching consequences arose from the close scrutiny of the results of Kunitake and Takarabe on the polymerisation of styrene by trifluoromethyl sulphonic acid. It became evident to the reviewer that in these reactions an important contribution to monomer consumption must have been made by the ester, and he was able to extract from the results the corresponding propagation rate-constants, kpu, for that cationoid insertion polymerisation. This became one of the most convincing supports for the author s views on cationoid insertions. 

These results show that even at the greatest ion concentration one third of the monomer consumption is due to the ester. 

Propagation step the following equation holds under the steady state. Monomer consumption rate can be written as... 

Therefore, monomer consumption rate largely depends on kd that is, a larger kd leads to a higher polymerization rate. If kd is much larger than kdy the predicted polymerization behavior is characterized by a low initiator efficiency and a wider polydispersity. 

Using the assumptions just discussed, the rate of polymer deposition can be expressed as the rate of monomer consumption and is given by... 

In the anionic polymerization of 6-caprolactone in THF with potassium tert-butoxide, monomer consumption is very fast and monomer could not be detected in any appreciable amount in the equilibrated mixture obtained after several minutes from the initiation. Upon terminating the reaction at 6 seconds after the introduction of the initiator solution, 6% monomer remained unreacted accompanied with polymers (68%) and oligomers (26%). 

Kinetic curves of phenylglycidyl ether consumption in the reaction with aniline in the presence of dimethylbenzylamine (DMBA) are presented in Fig. 15 a. As can be seen from this figure, addition of DMBA considerably increase the rate of monomer consumption in the initial and especially in the later stages of the reaction. The amount of the monomer consumed during polycondensation and polymerization can be readily determined by a parallel determination of the aniline consumption (Fig. 15 b). 

Note that the reaction rate in the presence of the mixture of amines (Curve 4) considerably exceeds the rate of monomer consumption if the same amines are reacted separately and are involved in polycondensation (Curve 1) and polymerization (Curve 6) therefore, an obvious synergetic effect is operative. Considering the fact that the initial rate of aniline consumption (Fig. 15 b, Curve 4) is practically the... 

The rate of monomer consumption by polymerization was found to be several times larger than the estimated maximum rate of monomer diffusion through the polymer deposit. Therfore, these authors believed polymerization must occur only in the outermost regions of the polymer... 

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