Yayoi Yoshioka

Structural change in the Brill transition of Nylon m/n (2) conformational disordering as viewed from the temperature-dependent infrared spectral measurements

Abstract The structural changes in the Brill transition of aliphatic Nylons m / n have been investigated by carrying out the temperature-dependent infrared spectral measurement for Nylon 6/10 –[–NH–(CH 2 ) 6 –NHCO–(CH 2 ) 8 –CO–] n –, Nylon 6/12 –[–NH–(CH 2 ) 6 –NHCO–(CH 2 ) 10 –CO–] n – and Nylon 10/10 –[–NH–(CH 2 ) 10 –NHCO–(CH 2 ) 8 –CO–] n –. They took the crystal structure of α-form at room temperature. By heating the samples up to the Brill transition temperature region, the conformation of the methylene segments was found to change remarkably from the all trans -zigzag form to the disordered conformation constructed by shorter trans -zigzag segments combined with some gauche bonds. At the same time, the twisting motion was found to occur around the CH 2 –amide bonds. During this order-to-disorder transition of molecular conformation, the intermolecular hydrogen bonds were kept alive although they were weaker gradually with increasing temperature. The methylene segments sandwiched by NH groups [NH(CH 2 ) m NH] were found to be disordered more remarkably than those of CO(CH 2 ) n CO sequence due to the difference in torsional energy barriers around the CH 2 –NH and CH 2 –CO bonds.

Analysis and Characterization of Aromatic Polyamide Copolymer Particles with Trifluoromethyl and Amino Groups

Nano-sized aromatic polyamide copolymer particles with trifluoromethyl (CF3) and amino (NH2) groups were prepared by copolymerizing 4,4′-diphenyldicarbonyl chloride (DPE) with 2,2-bis(4-aminophenyl) hexafluoropropane (BAHFP) and bis(3,4-diaminophenyl) ether (BDAPE). They were spherical particles with diameters of 150–320 nm. The diameter varied depending on the monomer ratio. The copolymer compositions of the products were characterized by FT-IR and Thermogravimetric analysis (TGA) measurements and found to be in close agreement with the monomer ratios. In addition, all of the products containing BDAPE were found to have a partially cross-linked structure. The amount of CF3 and NH2 groups attached to the particles changed depending on the monomer ratio.

Preparation of aromatic polyamide nanoparticles with multiple functional groups in mixed solvent solutions via a one-step precipitation polymerization

AbstractAromatic polyamide nanoparticles with carbonyl chloride (COCl) and carboxyl (COOH) groups are prepared in a one-step precipitation polymerization process using a diamine and a diacid chloride, employing a combination of various solvents. The morphology, number of COCl groups introduced and molecular weight of the resulting particles are found to be greatly affected by the composition of the reaction solution. Pyridine acts primarily as a catalyst and also reduces the particle size and affects the incorporation of COCl groups. These groups originates from the diacid chloride and are present at the ends of polymeric chains. The solubility of the particles in the reaction solution is closely correlated with the time required for precipitation and significantly influences the particle formation mechanism. This in turn affects the molecular weight and the number of COCl groups. Graphical abstractScheme of formation of aromatic polyamide nanoparticles with multiple functional groups

Structural changes of aromatic polyamide nanofibers upon annealing treatment

ABSTRACT Aromatic polyamide nanofibers with trifluoromethyl groups prepared using a precipitation polymerization method were annealed at various temperatures. The X-ray diffraction patterns and infrared spectra of the annealed products depended strongly on the annealing temperature. There was a transition in the temperature region of 250–300°C, where the conformation and the mobility of molecular chains changed significantly. Furthermore, the intermolecular hydrogen bonding increased, resulting in a higher degree of crystallinity. However, the morphology was unchanged. Meanwhile, the molecular structure and degree of crystallinity depended on the reaction period. However, those obtained by the annealing treatments above 250°C were the same.

Characterization of Aromatic Polyamide Particles Containing Carboxylic Acid and Carboxylic Acid Chloride Groups and Their Modification in Water

Two types of aromatic polyamide particles were prepared from 4,4′-diphenyldicarbonyl chloride and 3,5-diaminobenzoic acid in a reaction solution containing water or pyridine. Particles obtained using water (PA-water) were coarse spheres containing COOH groups with a diameter of 1 µm. Particles obtained using pyridine (PA-pyridine) were smooth spheres containing COOH and COCl groups with a diameter of 80 nm. The molecular weight of PA-pyridine was less than that of PA-water. During modification of PA-pyridine using 4′-aminobenzo-15-crown-5-ether, the COCl groups reacted with NH2 groups of the crown ether in water, resulting in attachment of the crown ether to the particle surface.