Initiator end groups

Park and Skene [65] found that the effectiveness of the initiator end groups for causing dehydrochlorination was in the ratio lauroyl peroxide-isopropyl peroxidi-carbonate-benzoyl peroxide-azoisobutyronitrile = 9.7 5.8 4.4 1.6. These values were obtained at 220°C, and the degradation rates were taken as the mean value for 0-20% dehydrochlorination. 

Because some of the macromolecules were initiated by the primary radicals to form macromolecules with initiator end groups, the functionality of ST HPMA polymers could be improved by using an initiator containing the same functional group as the chain transfer agent. 

Radical initiation is an intermediate way involving many kinds of telogens but sometimes it occurs with the formation of by-products coming from the presence of initiator end-group. 

Although there have been two different uses of the prime notation when dealing with polymers, because this usage is limited to the monomer part of the name there should not be confusion with the occasional use of the prime symbol as part of the initial end group... 

We can deduce from this that the 2-ferrocenylphenyl group gains maximum distance from the initiator end group (-CMe2Ph) at the expense of steric inter-... 

The result Is an alternating block copolymer or A(BA) Instead of ABA which would occur If caprolactam polymerization occurred only from the acyllactam Initiating end groups. The structure Is presented more clearly In schematic. See page 147. 

For initial end-group depolymerization followed by complete unzipping... 

The direct synthesis of block copoljmiers by radical polymerization is an alternative to using preformed blocks with functional endgroups. Polymers with initiator end-groups (3a,3b), with end groups accessible to radical activation polyinitiators (6, 7.)... 

Among the methods mentioned, NMR offers the most versatility as initiator residues incorporated into polymer chains can be distinguished from unchanged initiator, end groups... 

The most widely used theory of the stability of electrostatically stabilized spherical colloids was developed by Deryaguin, Landau, Verwey, and Overbeek (DLVO), based on the Poisson-Boltzmann equation, the model of the diffuse electrical double layer (Gouy-Chapman theory), and the van der Waals attraction [60,61]. One of the key features of this theory is the effective range of the electrical potential around the particles, as shown in Figure 25.7. Charges at the latex particles surface can be either covalently bound or adsorbed, while ionic initiator end groups and ionic comonomers serve as the main sources of covalently attached permanent charges. 

According to the transformation procedure, the population balance equations in terms of discrete variables (chain length, number of branch points) are transformed into a set of equations in z. The transformed set is solved and subsequently inverted to the original discrete variable domain. This process makes use of some interesting properties of certain mathematical expressions as transformed into the z-domain. Transformations and inversions are tabulated in textbooks [3). As an example we take linear AB step polymerization in a batch reactor with equal initial end group concentration Po ... 

There are many other industrial examples such as acrylic fibers made from polyacrylonitrile (with 7% vinyl acetate). The monomer is fairly water soluble at about 5% and the polymerization occurs in the aqueous phase. However, the polymer is insoluble in water. The primary particles precipitate and agglomerate, forming larger particles that are stabilized by ionic initiator end groups. Butyl rubber (isobutylene+ < 5% isoprene) is produced by cationic polymerization with aluminum trichloride catalyst in methyl chloride at about -100 °C. The polymer precipitates as fine polymer particles from the reaction medium. 

A number of parameters are reported to affect the overall rate of SSP and to define the relevant rate-determining step. Reaction temperature, initial end-group concentration, particle geometry, gas flow rate, crystallinity, and catalysts are listed as the most important and their effect on the controlling mechanism is presented briefly in Table 1, assuming negligible gas-phase resistance. ... 

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