**2.1. Microwave apparatus**

can simplify operations in chemical productions [2] and seeking greener solvents that are inherently environmentally and ecologically benign [3]. In addition, a desirable green solvent should be natural [4, 5], nontoxic [6, 7], cheap and readily available with additional benefits of aiding the reaction, separation or catalyst recycling. Most of the cationic initiators used in the synthesis of polymers and copolymers are expensive. They may be poisoned by products of the reaction or impurities present in the monomer feed, and contain heavy metals, such as chromium, mercury, antimony, etc., that presents environmental disposal problems for the user. As clay catalysts, montmorillonite a class of inexpensive and non-corrosive solid acids, have been used as efficient catalysts for organic reactions. Montmorillonite catalysts are easily recovered and reused [8]. In continuation of our studies on environmentally and green methods using solid supports, we report that acid-exchanged montmorillonite Mag-H+ is a novel and efficient solid catalyst for the synthesis of anionic polyacrylamide from

acrylamide monomer. In contrast to the more usually used catalyst, maghnite-H+

tion of anionic polyacrylamide using "H2

110 Characterizations of Some Composite Materials

separated from the polymer and regenerated by heating to a temperature above 100–105°C [9]. Microwave irradiation has been widely used in the synthesis of organic–inorganic hybrid materials because of its well-known advantages over conventional synthetic route towards well defined PAm (polyacrylamide) containing polymers include living anionic [10] and group transfer [11] polymerization techniques, both operating using protected analogues of the acrylamide monomers. However, traditional polymerization techniques show some practical disadvantages (e.g. requirement for extremely pure reagents, low functional group tolerance, limited combination with other monomers or polymer segments...). It has long been known that molecules undergo excitation with electromagnetic radiation. This effect is utilized in household microwave ovens to heat up food. However, chemists have only been using microwaves as a reaction methodology for a few years. Some of the first examples gave amazing results, which led to a flood of interest in microwave accelerated synthesis. Microwave heating has been found to be particularly advantageous for reactions under "dry" media. Enormous accelerations in reaction time can be obtained if overheating is carried out in closed containers under high pressure; a reaction which takes several hours under conventional conditions can be completed in a few minutes, in addition in the absence of solvent on a solid support with or without a catalyst, it offers a certain number of advantages: the solvents are often expensive, toxic, difficult to in the case of high-boiling aprotic solvents [12]. Moreover, the absence of solvent reduces the risk of explosions when reaction takes place in a microwave oven [13]. Reactions under "dry" conditions were originally developed in the late 1980s [14]. Synthesis without solvents under microwave irradiation offers several advantages [15]. The absence of solvent reduces the risk of explosions when the reaction takes place in a closed vessel in an oven [16]. Moreover, aprotic dipolar solvents with high boiling points are expensive and difficult to remove from the reaction mixtures [17]. During microwave induction of reactions under dry conditions, the reactants adsorbed on the surface of alumina, silica gel, clay [18]. Consequently, such supported reagents efficiently induce reactions under safe and simple conditions with domestic microwave ovens instead of specialized expensive commercial microwave systems [9]. Many researchers have studied cationic copolymeriza-

O"/KPS initiator system and CH<sup>2</sup>

Frequently, these initiators require the use of very high or very low temperature and high pressures during the polymerization reaction. The separation of the initiators from the polymer is not always possible. Therefore, the presence of toxic initiators presents problems in the

manufacture of polymers used especially in medical and veterinary procedures.

Cl2

solvent [19, 20].

can be easily

Microwave irradiation was performed in a single mode focused CEM reactor (Model Discover, CEM Co., Matthew, NC) operating at 2.45 GHz with ability to control output power. Temperature in the system was measured by a fiber optic temperature sensor preventing interaction with MWs and influence on the temperature reading. The heat capacity Cp of the solution was approximated as the heat capacity of water. All experiments were done under the same conditions by keeping constant irradiation power, temperature, and initial reaction mixture volume (12 mL). With the experimental design that was used, the temperature was maintained at 160°C in all experiments. The experimental equipment of microwave irradiation taking place is shown in **Scheme 1**.
