Monomer synthesis intercalation

In spite of the considerable number of thermoplastic PCNs synthesized by in-situ polymerization in the last 10 years, the area of rubber nanocomposites is not exhausted by far. To date, only a few number of reports have been published on the synthesis of 1,3-butadiene-based PNs. Specifically, as we have pointed out in this chapter, most of the work on the in-situ polymerization concerned with the anionic polymerization or copolymerization of 1,3-dienes by using the n-BuLi initiator. According to this technique, the monomer is intercalated in between the clay galleries and converts into polymer by in-situ addition of the anionic initiator. 

The topochemical polymerization of 1,3-diene monomers based on polymer crystal engineering can be used not only for tacticity but also for the other chain structures such as molecular weight [ 102], ladder [84] or sheet [ 103] structures, and also polymer layer structures using intercalation reactions [ 104-107]. Some mechanical and structural properties have already been revealed with well-defined and highly or partly crystalline polymers [ 108-111 ]. A totally solvent-free system for the synthesis of layered polymer crystals was also reported [112]. 

Fig. 10 Synthesis of a mixed brush may be accomplished by two strategies (a) A free radical initiator with low efficiency is used. This guarantees that some of the initiator is left after deposition of the first brnsh. Immersion into a second monomer yields a mixed brush where the two polymers are intercalated between each other, (b) A mixed monolayer could be used whereby A and B may be initiated independently (e.g. one is a photoinitiator and the other is a thermal initiator)...

Emulsion polymerization intercalation is an alternative method of PCN synthesis. This method is similar to in situ polymerization, but has several differences and limitations. In the emulsion polymerization method, micelle helps the polymer to be monodisperse, yet the micelles are limited in their ability to penetrate into the layer. Nonetheless, this method is attractive because of its use of a micelle as a targeted material, which helps the monomer or prepolymer to penetrate into the silicate layers. 

The general idea underlying the preparation of layered clay-polymer intercalates follows the simple rules of ion exchange. In most cases, the synthesis involves either intercalation of a polymer from solution or a suitable monomer followed by subsequent polymerization. But for more technologically important polymers, both approaches are limited since neither a suitable monomer nor a compatible polymer host solvent system is always available. 

Ternary composites with electroactive components were also discussed by Gomez-Romero and coworkers in one of their recent publications [48]. The ternary composites consisted of doped-polyaniline (PANI) or doped-polypyrrole (Ppy) intercalated into V2O5 xerogels. The dopant anion for the conducting polymers was [Fe(CN)g] (HCF), derived from H3Fe(CN)6. More specifically, the synthesis of Ppy/HCF/V205 and PANI/HCFA 20s was carried out by treating the monomer (aniline or pyrrole)... 

It was the pioneering work of Toyota researchers toward the development of polymeric nanocomposites in the early 90s [1, 2], in which electrostahcally held 1-nm-thick layers of the layered aluminosilicates were dispersed in the polyamide matrix on a nanometer level, which led to an exponenhal growth in the research in these layered silicate nanocomposites. These nanocomposites were based on the in-situ synthesis approach in which monomer or monomer solution was used to swell the filler interlayers followed by polymerizahon. Subsequently, GianneUs and CO workers [3, 4] also reported the route of melt intercalation for the synthesis of polymer nanocomposites. 

In-situ intercalation method was reported by Toyota researchers for the synthesis of polyamide nanocomposites that led to the exponential growth in the nanocomposites research. For generation of polymer nanocomposites by this method, the layered silicate mineral is swollen in monomer. After swelling, the polymerization of the monomer is initiated. As monomer is present in and out of the filler interlayers, therefore, the generated stmcture is exfoUated or significantly intercalated. As the rate or mechanism of polymerization in and out of the filler interlayers... 

Zhang and coworkers [27] reported the synthesis of SBR/clay nanocomposites by anionic polymerization, as shown in Scheme 11.2. The clay used is an OC modified by the intercalation of a quaternary long ammonium salt The fiUer is stirred into a 51 polymerization kettle filled with both styrene and butadiene monomer, THF, and cyclohexane. After stirring for 3 h, n-BuLi (THF/n-BuLi = 25) was added and the polymerization was carried out at 50 °C for 3 h. The authors found that the addition of the inorganic filler to the reaction mixture did not change the total conversion of both monomers, leading to the synthesis of SBR nano-composites with almost the same polymer composition as that of the materials... 

Boc- and Fmoc-terminated fluorescent fluorescein PNA monomer units were synthesized by means of solid-phase synthesis, and the products had photophysical properties comparable to nonmodifled fluorescein conjugates. 2-Aminopurine (2-ap) was the first fluorophore incorporated into a PNA strand for the purpose of examining PNA-DNA complexation via fluctuation in fluorescence emission. A more sophisticated sensing design was introduced by Seitz et al. that utilized the intercalator dye thiazole orange, termed a forced intercalation probe (FIT probe), for the determination of base pair mismatches within a duplex. ... 

The model illustrated in Figure 2 summarizes the overall mechanism for formation of epoxy polymer - clay nanocomposites. Upon solvation of the organoclay by the epoxide monomers, the gallery cations reorient from their initial monolayer, lateral bilayer, or inclined paraffin structure to a perpendicular orientation with epoxy molecules inserted between the onium ions. A related reorientation of alkylammonium ions has been observed previously for e-caprolactam intercalated clay intermediates formed in the synthesis of Nylon-6 -exfoliated clay nanocomposites (9). Thus, the ability of the onium ion chains to reorient into a vertical position in order to optimize solvation interactions with the monomer may be a general prerequisite for pre-loading the clay galleries with sufficient monomer to achieve layer exfoliation upon intragallery polymerization. 

This system does not increase the carbon monoxide or soot produced during the combustion, as many commercial FRs do [233]. Other polymer silicate nanocomposites based on a variety of polymers, such as polystyrene, epoxy and polyesters, have been prepared recently by melt intercalation [236]. A direct synthesis of PVA-clay (hectorite) complexes in water solution (hydrothermal crystallization) was reported [237]. It was assumed that the driving force of this phenomenon, at least kinetically, can be described in terms of a simple diffusion reaction of polymers/monomers into clay-layered structures. 

Polymer nanocomposites are synthesized by a variety of methods, which include in situ polymerization, solution polymerization, and melt intercalation. The route for nanocomposite synthesis suggested by Toyota researchers was also based on in situ monomer polymerization in the presence of filler. Subsequently, Giannelis and co-workers [28, 29]... 

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