Synthesis of Block Copolymers containing Chain-Controlled Aramid and Fluoroethylene Segments Arata Korematsu, Tsutomu Furuzono,* Akio Kishida Department of Biomedical Engineering, National Cardiovascular Center Research Institute, 5-7-1, Fujishirodai, Suita, Osaka 565-8565, Japan Fax: þ81-6-6872-8090; E-mail: furuzono@ri.ncvc.go.jp Received: July 22, 2004; Revised: September 28, 2004; Accepted: October 13, 2004; DOI: 10.1002/mame.200400188 Keywords: aramid; block copolymers; chain-control; fluoroethylene; polycondensation Introduction Aromatic polyamides (aramids) have received considerable attention with regard to the production of high-performance materials, due to their outstanding thermal stability, chem- ical resistance, low flammability, and mechanical proper- ties. [1,2] However, the poor solubility and high softening or melting temperature caused by the high crystallinity and high stiffness of these polymer backbones leads to difficult processability. Many approaches to increasing solubility and processability, therefore, have been made. The intro- duction of the fluorine atom into the aramid is one of these approaches. It is well known that the fluorine atom has peculiar properties such as high electron negativity, large C–F bond energy, and low intermolecular cohesive energy. The incorporation of the fluorine-containing component into the aramid, consequently, has already been design- ed. [3–7] While these polymers contained fluorine substitu- ents in benzene or hexafluoroisopropylidene groups in the main chain, or perfluoroalkyl groups in the side chains, there are very few examples of aramids containing fluoro- ethylene segments in the main chains. It is expected that block copolymers containing aramid and fluoroethylene segments would be novel polymers by which the proces- sability is improved compared with aramid, without impair- ing the thermal and mechanical properties of aramid, and that they would be suitable for functional material. Steinhauser and Mu ¨lhaupt reported the synthesis of aramids derived from diamine-terminated oligo(tetraflur- orethene)s. [8] Although these polymers were soluble in polar solvents, such as N,N-dimethylformamide, N,N- dimethylacetamide, and dimethyl sulfoxide, solubility in regard to other solvents was not clarified. In an earlier publication, we demonstrated the synthesis of fluoroethy- lene-aramid block copolymer soluble in tetrahydrofuran and acetone, and not just in polar solvents. [9] The number- average molecular weight of this copolymer, however, is 1.7  10 4 . We decided as our next target, therefore, to syn- thesize a copolymer having a larger molecular weight and in order to realize it, we judged that the chain of the aramid segment needs to be extended, expecting that this would bring about the production of a copolymer with a larger molecular weight than our previous one and lead to the development of material with high functionality. Summary: Novel block copolymers containing aromatic polyamide (aramid) and fluoroethylene segments were syn- thesized by a two-step solution polycondensation. This synthetic method could control the chain-length of aramid segments and these copolymers could have high structural regularity. The number-average molecular weight ( M n ) of one of these polymers is over 2.0  10 4 . Incorporating fluoro- ethylene segments improves the solubility of the resulting polymer compared with conventional aramids. The synthesis of the fluoroethylene-aramid block copolymers. Macromol. Mater. Eng. 2005, 290, 66–71 DOI: 10.1002/mame.200400188 ß 2005 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim 66 Communication