ABSTRACT:A series of aromatic polyamides of high molecular weight was synthesized by low-temperature solution polycondensation of 2,5-bis[( carboxyethyl)thio ]-1,4-phenylenediamine with aromatic dicarboxylic acid chlorides. The aromatic polyamides having reactive pendent (carboxyethyl)thio groups had inherent viscosities in the range of0.57 and 1.66 di g-1 . The precursor polyamides were subjected to thermal cyclization to the corresponding polybenzothiazoles along with the elimination of acrylic acid and water, which were detected by GC-MS analysis of the polyamides. The resulting polymers were characterized as high temperature aromatic polymers.KEY WORDS New Synthetic Method / Two-Step Synthesis / Thermal Cyclization / Polyamides with Reactive Pendants / Polybenzothiazoles / Currently, polybenzothiazoles have drawn attention not only to the research for fibers, films, and molecular composites as their excellent thermal and mechanical properties, 1 -9 but also to that for functional polymers such as third-order nonlinear optical materials due to their conjugated structures. 10 -16 Aromatic polybenzothizoles, which were introduced in the field of heteroaromatic thermally stable polymers in 1965, 17 -19 were prepared directly by using polyphosphoric acid, which acts as both reaction medium and condensing agent. Since aromtic polybenzothiazoles are insoluble in common organic solvents, the potential utility of the polybenzothiazoles had been restricted in spite of many potential applications.We have focused on new soluble precursor polyamides which could be converted to the polybenzothiazoles through thermal cyclization to improve the difficulty of processing of the polybenzothiazoles. A series of precursor t To whom all correspondence should be addressed.
930polyamides having pendant groups 20 -22 was synthesized and characterized in order to achieve good solubility of the polyamides in organic solvents and to reduce the temperature for the conversion to the corresponding polybenzothizoles. Now, we have designed a new 2,5-dimercapto-1,4-phenylenediamine derivative, 2,5-bis-[ ( carboxyethyl)thio ]-1,4-phenylenediamine, for the synthesis of precursor polyamides having reactive (carboxyethyl)thio groups. The pendant (carboxyethyl)thio groups would be expected to give the precursor polyamides enough flexibility during the thermal cyclizations, and to reduce the temperaure for conversion to the corresponding polybenzothiazoles.The polyamides, which are soluble in organic solvents and readily converted to the corresponding polybenzothiazoles by thermal treatments, should also have a special potential of constructing films with nanometer thickness by
ABSTRACT:A new method so called polymerization blending of polyamic acids was carried out in the solution of the precursor polyamide for rigid-rod polybenzothiazole (PBZT) as reinforcement, leading to the formation of PBZT-polyimide blend films. The morphology of the transparent films, obtained by the polymerization blending, casting, coagulation, and thermal treatment, was observed by scanning electron microscopy (SEM) in order to investigate the state of dispersion of the PBZT in the films. The SEM photographs showed that the PBZT was well dispersed at micro-level. Mechanical properties of the films were improved in modulus and tensile strength, which were corresponded well with the morphology of the films; furthermore, dynamic mechanical. analysis was also performed to characterize the films consisted of respective polyimides as a matrix. The method of polymerization blending leads to an effective way to achieve the micro-composites consisted of the PBZT and the polyimides with ideal dispersion of the reinforcement and hence having excellent mechanical properties.KEY WORDS Polymerization Blending/ Blend Films/ Micro-Composites/ Polybenzothiazole / Polyimides / Precursor Polyamides / Mechanical Properties / Aromatic polybenzothiazoles have been known as a class of rigid-rod heterocyclic polymers 1 -3 and have been taken great interest because these polymers have potential for fabrication into high-strength and high-modulus fibers and films. 4 -8 Recently, we have developed a new series of soluble precursor aromatic polyamides (aramids) having protected thiol groups, which could be converted by thermal treatment to the corresponding polybenzothiazoles. 9 -12 In this connection, we have aimed to prepare high performance micro-composites consisted of polyimides as matrices and the polymer (PBZT) as reinforcement through the new precursor polyamide derived from 2,5-bis-[[(methoxycarbonyl)ethyl]thio ]-1 ,4-phenylenediamine and 2-chloroterephthaloyl chloride. In order to obtain the high performance composites with excellent mechanical properties, the reinforcing polymer should be dispersed in the matrix polymer as fine as possible; thus, the extreme concept of molecular composites, where the reinforcing polymer such as rigid-rod polybenzothiazole or aramid was finely dispersed in matrix polymers at molecular level, have been proposed and materialized as new types of composites. 13 -16 Since reinforcing polymers and flexible-coil t To whom all correspondence should be addressed.
395T. HATTORI et al. polymers as matrix are generally incompatible in nature leading to ready phase separation, the above named polymerization blending or the in-situ direct polycondensation is a suitable method to achieve good compatibility and fine dispersion in the composites. 1 7 -21 We have developed here a new method of polymerization blending where polyamic acid was synthesized in the polymer solution consisted of an organic solvent and the precursor polyamide for the PBZT as reinforcement, followed by conversion of the precu...
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