**6.4. Proposed mechanism**

In general, the anionic polymerization like in other vinyl polymerization methods consists of three main reactions: (a) initiation, (b) propagation, and (c) termination, as described in **Figure 13**. However, termination is brought about intentionally using a suitable electrophile, which can be useful for end group modification [49]. The initiation reaction is generally fast and is not reflected in the overall rate of the polymerization [57]. The kinetics of the polymerization is predominantly controlled by the propagation step [58].

The interaction of propagating ion pairs with functional groups of the vinyl monomer or the polymer chain can affect the propagation rate and in some cases induces side reactions that can cease the polymerization [49]. In a side reaction-free anionic vinyl polymerization; the termination is a simple rapid reaction wherein anions are quenched through acidic hydrogen or another suitable electrophile [45]. Hence, it is important to match the reactivity of the initiator with the propagating species in order to have fast and homogeneous initiation [44]. For example, the reaction of sodium metal generates a radical anion in polar solvent, which can be used as initiator for the anionic polymerization [59]. The anionic polymerization of acrylamide in free solvent and under microwave irradiation was first studied using the maghnite-Na+ as catalyst. The proposed anionic polymerization mechanism as shown in **Figure 13**. The high reactivity of the methylene group of double bond in acrylamide, involves Synthesis and Characterization of Polymeric Material Consisting on Acrylamide Catalyzed… http://dx.doi.org/10.5772/intechopen.80033 123


**Table 7.** Mechanical properties of APAm/maghnite samples.

**6.3. Mechanical properties**

122 Characterizations of Some Composite Materials

literature [56].

the maghnite-Na+

**6.4. Proposed mechanism**

To evaluate the effect of maghnite (Algerian MMT) catalyst in APAm, we prepared five samples with the same procedure. Tensile tests were conducted using a LLoyd LR/10KN Universal

Compared with PAm prepared by other catalyst such as Lewis acid and under conventional method, the Young's modulus and yield strength are greatly enhanced as shown in (**Table 7**).

The tensile test was carried out to evaluate the tensile properties of the various samples compositions in order to determine the influence of the addition of the clay on the tensile properties of the virgin matrix. Young modulus, tensile strength and elongation at break were evaluated as a function of the mass fraction of clay in all series of samples. The test pieces are maintained during the test by pneumatic jaws preventing any sliding of the test

it can be deduced that the incorporation of the clay into the APAm matrix, with different percentages, has significantly improved all of its tensile properties. Thus Young's modulus increased in compositions with the highest clay contents, (1–12 w%). The composition of clay (5 w%) in APAm has the highest tensile values. This is attributed to the interactions between the polymer chains and the nanometric layers of the clay with a decrease in the value of the Young's modulus. This composition is the most tensile resistant with a maximum stress of 57.55 MPa, the most flexible (E = 1.89 GPa) and the most ductile (ε<sup>r</sup> = 54.03%). This result confirms the exfoliation of maghnite clay in polymer (APAm) which is in agreement with the

In general, the anionic polymerization like in other vinyl polymerization methods consists of three main reactions: (a) initiation, (b) propagation, and (c) termination, as described in **Figure 13**. However, termination is brought about intentionally using a suitable electrophile, which can be useful for end group modification [49]. The initiation reaction is generally fast and is not reflected in the overall rate of the polymerization [57]. The kinetics of the polymer-

The interaction of propagating ion pairs with functional groups of the vinyl monomer or the polymer chain can affect the propagation rate and in some cases induces side reactions that can cease the polymerization [49]. In a side reaction-free anionic vinyl polymerization; the termination is a simple rapid reaction wherein anions are quenched through acidic hydrogen or another suitable electrophile [45]. Hence, it is important to match the reactivity of the initiator with the propagating species in order to have fast and homogeneous initiation [44]. For example, the reaction of sodium metal generates a radical anion in polar solvent, which can be used as initiator for the anionic polymerization [59]. The anionic polymerization of acrylamide in free solvent and under microwave irradiation was first studied using

**Figure 13**. The high reactivity of the methylene group of double bond in acrylamide, involves

as catalyst. The proposed anionic polymerization mechanism as shown in

for the determination of

. From these results,

Machine at room temperature and crosshead speed of 50 mm min−<sup>1</sup>

It shows that the mechanical properties depend on amount of catalyst.

piece during the traction. The initial strain rate was set at 5 mm min−<sup>1</sup>

ization is predominantly controlled by the propagation step [58].

tensile modulus and yield strength, according to the standard ASTM D638.

**Figure 13.** Proposed mechanism for obtained anionic polyacrylamide catalyzed by maghnite-Na<sup>+</sup> .

the formation of a strong proton donor by the reaction of the maghnite-Na+ , followed by the protonation of the acrylamide molecule, whose ensuing carbenium ion rearranges to form a carbocation responsible for the propagation reaction [60] . This process is extremely rapid and exothermic. In order to obtain polymers with viable molecular weights of a few thousand, the polymerization temperature must be particularly low and around of −160°C [61], to reduce the relative kinetic contribution of the transfer reaction with respect to chain propagation. The driving forces for the reaction are the high reactivity of the l double bond of monomer and the high reactivity of catalyst [62, 63, 64, 65].

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