Fast synthesis of optically active polyamides containing L-methionine linkages in ionic liquid via a microwave-assisted process

Colloid and Polymer Science (Impact Factor: 1.87). 09/2009; 287(9):1111-1116. DOI: 10.1007/s00396-009-2080-6


Several optically active aromatic polyamides have been synthesized via direct polycondensation of chiral diacid monomer 1 containing l-methionine moiety with diverse aromatic diamines 2a–2h in a green medium, namely 1,3-dipropylimidazolium bromide as a room temperature ionic liquid. In order to evaluate the advantages
of microwave promotion of these polymerization reactions, we compared microwave irradiation (method I) with conventional oil
bath heating (method II) by means of reaction rates, conversions, and inherent viscosities. The inherent viscosities of resulting
polymers were ranging between 0.47–0.65 and 0.35–0.57dL/g in methods I and II, respectively. These polymers were characterized by means of 1H-NMR, FT-IR, elemental, organosolubility, differential scanning calorimetry, and thermal gravimetric analysis techniques.
The obtained polymers show thermal stability up to 273 °C under nitrogen atmosphere and good solubility in polar organic solvents.
Polymerization reactions proceeded in higher yields and moderate inherent viscosities under microwave irradiation conditions
besides the dramatically shorter reaction times and achieving the more pure products.

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    • "One of the main principles of green chemistry is to mature an alternative reaction medium , which is the basis for the advancement of numerous cleaner chemical technologies. In particular, the use of ionic liquids (ILs) to replace organic solvents has recently generated a lot of interest as possibly environmentally safe in wide variety of polymerisation reactions [12] [13] [14] [15] [16]. ILs encompass interesting properties, such as outstanding microwave absorbance , wide liquid temperature range, designable structures, negligible volatility, elevated ionic conductivity, non-flammability, recyclability, good dissolving ability, and good thermal stability [17] [18] [19] [20]. "
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