High‐viscosity polyesters from secondary alicyclic 1,4‐cyclohexanedicarboxylic acids and hydroquinones with thionyl chloride/pyridine condensing agent

High‐viscosity polyesters can be prepared by the polycondensation of secondary aliphatic trans‐cyclohexanedicarboxylic acid (t‐CHDC) and hydroquinones using SOCl₂/pyridine condensing agent at 80°C. Incorporation of its cis‐isomer significantly affected η_inh and the thermal property of the resulting copolymers. The copolymers of t‐CHDC, hydroquinones, and p‐hydroxybenzoic acid having different monomer sequences were prepared by changing the order of introduction of monomers.     

Random copolyamides of terephthalic acid,p‐phenylenediamine and p‐aminobenzoic acid soluble in N‐methylpyrrolidone/CaCl2

Moderate‐molecular‐weight copolyamides soluble in N‐methylpyrrolidone (NMP) containing dissolved CaCl₂ can be obtained by polycondensation of terephthalic acid (TPA), p‐phenylenediamine (PPD), and p‐aminobenzoic acid (PABA) with triphenyl phosphite/pyridine in NMP. The randomly copolymerized polymers contain more than 40 mol‐% of PABA and are easily soluble in NMP.     

Modification of polycondensation of isophthalic and terephthalic acids and bisphenols with tosyl chloride/dimethylformamide/pyridine by the presence of additives

In copolycondensation with 2,2‐bis(4‐hydroxyphenyl)propane (BPP) and bisphenols (BPs) containing various alkylidene linkages, the associative interactions between BP moieties in the resulting oligomers most likely affected the reaction. To modify the interactions to favorably control the reaction, several additives were examined in a two‐stage polycondensation of an equimolar mixture of isophthalic acid and terephthalic acid, first with BPP (50 mol %) and next with additional BPP. Of additives used, diphenylmethane of an equivalent to BPP in the preformed oligomers was most effective. The results are discussed in terms of the distributions of resulting oligomers prepared at 70% extent of reaction. Better results were obtained when the distributions showed profiles similar to the theoretical one calculated on the basis that the reactivity of the oligomers is the same independent of their chain lengths. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 41: 970–975, 2003     

High-molecular-weight polyterephthalamide by direct polycondensation reaction in the presence of poly(ethylene oxide)

Polyterephthalamides of high molecular weight (η_inh up to 1.9) were obtained by the direct polycondensation reaction of terephthalic acid and aromatic diamines in the presence of poly(ethylene oxide) (PEO) with triphenyl phosphite in a N-methylpyrrolidone (NMP)–pyridine solution that contained lithium chloride. The molecular weights of the polymers produced varied with the amount and molecular weight of PEO, which showed maximum values when PEO with a molecular weight of 2.0 × 10⁴?5.0 × 10⁵ was used in a concentration of about 0.5 wt % in the solvent. The polycondensation reaction was significantly affected by the level of pyridine in a mixed solvent of NMP and pyridine and by the concentration of the lithium chloride added.     

A new organic semiconducting polymer from Cu2+ chelate of poly(vinyl alcohol)and iodine

A new, easily processed, organic semiconductor was prepared from poly(vinyl alcohol) (PVA). The Cu²⁺ chelate of PVA exhibited excellent surface resistivity around 10³ Ω cm^?2 when modified with iodine. Favorable conditions for preparing the chelate effective for the conduction were investigated. The resistivity was significantly affected by the amounts of cupric salts and iodine, satisfactory results being given by more than 15 wt% of cupric salts and about 4 wt% of iodine. Effects of molecular weight of PVA and the chelate structure were also studied.     

Preparation of aromatic polyesters by the direct polycondensation reaction with diphenyl chlorophosphate in pyridine

The direct polycondensation reaction of diphenyl chlorophosphate (DPCP) as a new condensing agent in pyridine was used for the preparation of polyarylene esters. High-molecular-weight polymers can be prepared by reacting a pyridine solution of dicarboxylic acids and DPCP in the presence of LiCl, followed by treating with a pyridine solution of bisphenols. About an equivalent of LiCl, and 30 mol % excess of DPCP were most favorably added. Effects of the initial reaction of the acids and DPCP, and of dropwise addition of bisphenols on the polycondensation were investigated. Polycondensations of several hydroxybenzoic acids were also carried out with limited success.     

Preparation of high molecular weight polyhydrazides from hydrazine monohydrochloride using phenylphosphonic dichloride and phosphorus compounds as additives

Significantly high molecular weight poly(isophthalic dihydrazide) of inherent viscosity up to 1.6 (DMSO) was prepared by the reaction of isophthalic acid and hydrazine monohydrochloride using phenylphosphonic dichloride in the presence of phosphorus compounds such as phosphine oxides. The phosphorus compounds used as additives were assumed to be involved in the reaction through a complexation with the monohydrochloride, enhancing the reactivity of the hydrazine. It was attempted to prepare copoly(hydrazide-amides) with different monomer sequences by changing the relative reactivity between diamines and the hydrazine using the phosphorus compounds. The copoly(hydrazide-amide)s were studied in terms of the dehydration reaction of hydrazide groups into 1,3,4-oxadiazole groups. © 1993 John Wiley & Sons, Inc.     

Strain induced grain boundary premelting in bulk copper bicrystals

In bulk bicrystals strain induced grain boundary premelting (SIGBPM) occurs when heavy screw dislocation pileup can be held up to a certain high temperature, approximately 0.6T _M, where T _M is the melting point of bulk material in Kelvin. SIGBPM occurs at grain boundaries to which new twist component is added due to the rotation of both component crystals toward opposite direction about the axis perpendicular to the grain boundary plane. At the original grain boundary, grain boundary sliding takes place due to this relative rotation. In f.c.c. metals with relatively low stacking fault energies such as copper, nickel, brass(30Zn) and silver, dislocations dissociate into partials. Therefore high density tangled dislocations introduced during plastic deformation hardly loose. If these dislocations can be held to high temperatures, SIGBPM is promoted. Formation of static or dynamic recrystallized grains suppresses SIGBPM itself and the propagation of grain boundary cracks formed by SIGBPM.