A new class of optically active poly(amide imide urethane)s (PAIUs) was synthesized via a two-step diisocyanate route. In the first step, 4,4 0 -methylenebis(phenyl isocyanate) (MDI) was reacted with different diacids to produce an isocyanate-terminated oligo(amide imide). The chain extension of the previous hard segment with poly (ethylene glycol) diols with a molecular weight of 400 was the second step for furnishing a series of new PAIUs. N-Trimellitylimido-L-leucine was used as a diacid monomer for polycondensation reactions. Polymerization reactions were performed without any catalysts or with pyridine or dibutyltin dilaurate as a catalyst. The optimized reaction conditions were used for the reaction of N-trimellitylimido-L-isoleucine, N-trimellitylimido-L-methionine, N-trimellitylimido-S-valine, and N-trimellitylimido-L-phenylalanine as diacid monomers with MDI. The resulting multiblock copolymers had inherent viscosities of 0.25-0.78 dL/g. These multiblock copolymers were optically active, thermally stable, and soluble in amide-type solvents. All these polymers were fully characterized with Fourier transform infrared spectroscopy, 1 H-NMR and ultraviolet-visible spectroscopy, specific rotation measurements, and thermal analyses. Some structural characteristics and physical properties of these new optically active PAIUs were examined.
Poly(amide-imide)s (PAI)s as engineering materials have received more attention owing to their high thermal and chemical stability. Therefore, organic/ inorganic nanocomposite (NC) of these materials has been widely studied in the last few decades. Here, we present PAI-NCs preparation containing surface modified TiO 2 nanoparticles (NP)s by employing silane coupling agent under ultrasonic process. Optically active nanostructure PAI was prepared from 5-(2-benzimidazole)-1,3-phenylenediamine (4) and chiral diacid monomer N-trimellitylimido-L-leucine (5) using molten salt tetrabuthylammonium bromide as an activating medium. A considerable improvement of properties can be achieved by inserting NPs into the polymer matrix. The results of field emission scanning electron microscopy and transmission electron microscopy indicated that there is a little aggregation of a large quantity of particles. Thermogravimetric analysis confirmed that the heat stability of the polymer NCs in the temperature range of 400-800 ºC was enhanced.
A number of chiral wholly aromatic polyesters (PEs) with phthalimido and flexible chiral unit in the backbone were prepared from a chiral synthesized diacid monomer, 5-(3-methyl-2-phthalimidylpentanoylamino)isophthalic acid (1), and various aromatic diols via the polyesterification reaction. The tosyl chloride/pyridine/N,N-dimethylformamide (DMF) system was used as a condensing agent. All of the these polymers having bulky phthalimido and amino acid functionalities in the side chain showed excellent solubility and readily dissolved in various solvents such as N-methyl-2-pyrrolidinone, N,N-dimethylacetamide and DMF. Since, these chiral polymers have natural amino acids in the polymer architecture, they are expected to be biodegradable and therefore may be classified under eco-friendly polymers. They had useful levels of thermal stability associated with excellent solubility. Thermogravimetric analysis (TGA) showed that the obtained PEs are rather thermally stable, 10% weight loss temperatures in excess of 317 degrees C, and char yields at 700 degrees C in the nitrogen atmosphere higher than 24%. The resulting polymers were obtained in good yields with inherent viscosities ranging between 0.22 and 0.56 dL/g and were characterized with FT-IR, 1H-NMR, elemental and TGA techniques.
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