Health & Environmental Research Online (HERO)


Print Feedback Export to File
7340568 
Journal Article 
Novel Melt-Processable Poly[(acyloxy)aloxane] as Alumina Precursor 
Kimura, Y; Furukawa, M; Yamane, H; Kitao, T 
1989 
1 
Macromolecules
ISSN: 0024-9297
EISSN: 1520-5835 
22 
1 
79-85 
English 
A poly[(acyloxy)aloxane] with both n-dodecanoic acid (DA) and 3-ethoxypropanoic acid (EPA) ligands was prepared by the sequential reaction of triethylaluminum (TEA) with DA, water, and EPA, respectively. The hydrolytic polymerization of the first-stage product, diethyl(dodecanoato)aluminum, yielded a less soluble cross-linked oligomer of poly[(dodecanoyloxy)aloxane] (PDA). Further reaction with EPA afforded soluble thermoplastics of poly[(acyloxy)aloxane] with DA and EPA mixed ligands. The viscosity of the polymers was found to be dependent on the EPA to TEA ratio when the DA to TEA ratio was kept at unity. The maximum inherent viscosity, 0.58 dL/g, was observed at an EPA to TEA ratio of 0.8. The structure of these polymers was confirmed by 27A1 NMR, as well as other spectroscopic techniques and elemental analyses. The hexacoordination states of the aloxane, characteristic of the polymers, were due to the chelation of both the carboxylate and carboxyl groups of DA and EPA. Even for the products with less than 1.0 molar ratio of EPA per repeat unit, the ethoxy group of EPA also participates in the coordination. Since the polymers melted at ca. 200 °C, they could be melt-spun into thin fibers with a ram extruder having an orifice of 0.5 mm in diameter. Both spinnability and the quality of the filaments obtained were found to be best for the polymer with an EPA to TEA ratio of 0.8, whose molecular weight was higher than that of the other polymer samples. The as-spun fibers of this polymer were annealed at 160 °C in a flow of air and then pyrolyzed in a flow of nitrogen from 160 to 700 °C. Above 700 °C the flow was changed to air again, and the fiber was sintered up to 1400 °C. In the course of this multistep pyrolysis the fiber was subjected not only to shrinkage but also to the phase transition of alumina. Hence, the physical properties and the morphology of the fiber were greatly dependent on the pyrolysis temperature. The highest strength and modulus of the sintered fiber were 520 MPa and 48 GPa, respectively. These values ought to increase upon suppression of the abrupt phase transitions. On the bases of these data, poly[(acyloxy)aloxane] with DA and EPA mixed ligands was proven to be versatile as a melt-processable preceramic polymer for alumina. © 1989, American Chemical Society. All rights reserved. 
Alumina; Aluminum compounds; Ceramic materials--Fibers; Polymers--Mechanical Properties; Polymers--Pyrolysis; Ethoxypropanoic Acid; Melt Processing; Polyacyloxyaloxane; Preceramic Polymers; Triethylaluminum; Metallorganic polymers