Absorption of monomer

Clearly, unless monomer is the intended photoinitiator, it is important to choose an initiator that absorbs in a region of the UV-visible spectrum clear from the absorptions of monomer and other components of the polymerization medium. Ideally, one should choose a monochromatic light source that, is specific for the chromophorc of the photoinitiator or photosensitizer. It is also important in many experiments that the total amount of light absorbed by the sample is small. Otherwise the rate of initiation will vary with the depth of light penetration into the sample. 

Due to the reduced absorption of monomers and the low rate of polymerization in the micelles, the diffusion of monomer molecules from droplets to the growing particles is limited. Correspondingly, the probability of polymerization in the droplets increases. 

Template. A polynucleotide chain that serves as a surface for the absorption of monomers of a growing polymer and thereby dictates the sequence of the monomers in the growing chain. 

After the complete absorption of monomer existing as monomer droplets in the water phase, the following relationship holds ... 

For gaseous monomers measurements of equilibrium monomer pressure permits the determination of [M]e. As pointed out, however, absorption of monomer in the condensed phase may lead to serious errors 24). 

Absorption of monomer onto the catalyst surface, that is, complex formation, can be described by a Langmuir-Hinshelwood isotherm. The fraction of surface /mon occupied by monomer is consequently... 

Another example of template polycondensation was described by Ogata and co-workers (82-85). Polycondensation of dimethyl tartrate or dimethyl muconate with hexamethylenediamine was increased by the presence of poly(vinylpyrrolidinone) and poly(vinyl alcohol). It was also foimd that polysaccharides increase the polycondensation rate. It seems that hydroxyl groups play a substantial role in the absorption of monomers onto the template. 

There are some requirements for monomers used for the emulsion polymerization. The primary requirement for monomers is that they must have a limited water solubility and be soluble in the formed polymer. However, the solubility in water should not be too high, otherwise this monomer would tend to polymerize in the water phase. In the mechanism for emulsion polymerization one of the driving forces is the absorption of monomer into the polymeric particles if the monomer and polymer are not mutually soluble then this process will not be efficient. Many different vinyl monomers are currently used in practical emulsion polymerization, including acrylates, methacrylates, St, AN (in copolymers), VAc, isoprene, and 1,3-butadiene. In addition, the monomers would not react with water, surfactants and other additives. Table 11.6 presents the propagation rate coefficients of various monomers examined in emulsion polymerization. 

II Particle growth, by absorption of monomer and conversion to polymer ending with the complete consumption of the monomer phase. 

In a precipitation polymerization, the system initially is in a homogeneous phase, because monomer and initiator are completely soluble in the initial reaction medium, but, upon initiation, the formed polymer precipitates as soon as it forms. After precipitation, the polymerization proceeds by absorption of monomer and initiator into the polymer particles. Bulk polymerization of vinyl chloride and solution polymerization of acrylonitrile in water are examples of precipitation polymerization. Precipitation polymerizations are often referred to as powder or granular polymerizations because of the forms in which the final polymer products are obtained. 

The next case, when absorption of monomer is strong and polymerization occurs according to the zip mechanism is illustrated in Scheme 3. 

The next case, where absorption of monomer is strong and polymerization occurs according to the zip mechanism, can be observed in the system examined by Blumstein and Kakivaya. Low-molecular-weight ionenes are used as a template for template polymerization of strong acidic monomers. 

In the 1960s there were studies of absorption of monomers by clays [116, 117]. In more recent years, monomers such as caprolactam were absorbed into organo clays and were subsequently polymerized. The most important of these efforts involved Toyota researchers [118 to 125] using caprolactam. These products were called nanocomposites and seem to contain polyamide intercalated between silicate layers or had exfoliated structures. Other monomers have also been absorbed into montmorillonite and polymerized. These include the formation of polyimides [126], epoxy resins [127], and polylactones [128]. 

Continual absorption of monomer into growing polymer-monomer (swollen) particles leads to the disappearance of the monomer droplets as a separate phase. This happens after micellar soap has disappeared, and the system therefore only consists of monomer-swollen polymer particles. 

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