Preparation of New Optically Active Polyamides Containing a L-Phenylalanine, Phthalimide Side-Chain via the Diisocyanate Route by Microwave Energy: Comparison With Conventional Heating

Abstract

Phthalic anhydride was reacted with L-phenylalanine in N,N-dimethylformamide solution at refluxing temperature, which led to the formation of imide acid. Treatment of this imide acid with excess thionyl chloride gave acid chloride in high yield, which further reacted with 5-aminoisophthalic acid to yield (2S)-5-(3-phenyl-2-phthalimidylpropanoylamino)isophthalic acid as a bulky chiral aromatic diacid monomer. The polycondensation reaction of this diacid with different aromatic and aliphatic diisocyanates such as 4,4 -methylene bis(4-phenylisocyanate), toluylene-2,4-diisocyanate, hexamethylene diisocyanate and isophorone diisocyanate was developed by two different methods: microwave-assisted and classical heating in the presence of N-methyl-2-pyrrolidone as a solvent. The polymerization reactions proceeded fast and produced a series of new optically active polyamides (PAs) with good yield and moderate inherent viscosity of 0.25-0.46 dl/g. The resulting PAs are optically active and thermally stable. All of the above compounds were fully characterized by means of FT-IR spectroscopy and specific rotation techniques and typical ones by 1 H-NMR, elemental analysis and thermogravimetric analysis.

Advances in synthetic optically active condensation polymers - A review

“…PAs derived from carbohydrates are the object of current attention, because they are not only optically active, but also for its potential as biodegradable and biocompatible materials [72][73][74][75][76][77]. Mallakpour and coworkers [78][79][80] have investigated the synthesis of PAs from the polycondensation reaction of chiral 5-(4-methyl-2-phthalimidylpentanoylamino)isophthalic acid, (2S)-5-(3-phenyl-2-phthalimidylpro-panoylamino)iso-phthalic acid and 5-(3-methyl-2-phthalimidylpentanoylamino) isophthalic acid with several aromatic and aliphatic diisocyanates such as 4,4!-diphenylmethane diisocyanate (MDI), toluylene-2,4-diisocyanate (TDI), isophorone diisocyanate (IPDI) and hexamethylene diisocyanate (HDI) under microwave irradiation as well as conventional technique (Figure 2). The resulting aromatic PAs were optically active and soluble in various organic solvents and have good thermal stability.…”

One Decade of Microwave‐Assisted Polymerizations: Quo vadis?

“…They prepared polymers containing L-phenylalanine, phthalimide, and L-leucin sidechains from the reaction of bisfunctional acids like (2S)-5-(3-phenyl-2-phthalimidylpropanoylamino)-isophthalic acid with bisfunctional isocyanates, comprising 4,4 0 -methylene bis(4-phenylisocyanate), toluene-2,4-diisocyanate, hexamethylene diisocyanate, and isophorone diisocyanate. [61][62][63] The authors stated that the polymerization rate was higher in microwave-assisted reactions that were performed in a domestic microwave oven at 900 W compared to CH. Mallakpour and Taghavi also used ionic liquids such as tetrabutylammonium bromide (TBAB) as reaction media in combination with microwave-assisted heating for the abovementioned polymerizations.…”

Microwave-Assisted Polyester and Polyamide Synthesis

“…Mallakpour et al have used microwave heating to synthesize polyamide [20,[26][27][28][29][30]. Mallakpour et al have used microwave heating to synthesize polyamide [20,[26][27][28][29][30].…”