Nanocomposites Derived from Carbon Nanofibers and a Hyperbranched Poly(Ether-Ketone): In Situ Polymerization, Chain-End Modification, and Properties (Preprint)

摘要

5-Phenoxyisophthalic acid, an A2B monomer, was easily polymerized via a Friedel-Crafts acylation in poly(phosphoric acid)/phosphorus pentoxide (PPA/P2O5; 1:4 w/w) medium to form a CO2H-terminated hyperbranched poly(ether- ketone), HPB-PEK. Thus, the polymerization of 5-phenoxyisophthalic acid, in the presence of various amounts (1, 2, 5, 10, 20, 30 and 40 wt%) of vapor-grown carbon nanofibers (VGCNF) was performed under similar reaction conditions. The resulting (HPB-PEK)-g-VGCNF nanocomposites were insoluble in dichlorobenzene or toluene, but showed greatly improved solubility in polar solvents such as NMP, DMF, DMAc, ethanol, and even higher solubility in ethanol/triethylamine mixture or in aqueous ammonia solution, apparently stemming from the ionization of the numerous peripheral CO2H groups. This is in contrast to our previous result that the nanocomposites derived from VGCNF similarly grafted with a linear meta- poly(ether-ketone), mPEK, with 1-30 wt% VGCNF content had much lower solubility in these polar solvents but are more soluble in methanesulfonic acid. As a way to determine both the ease in perfoming chemical transformation on the periphery of the hyperbranched component of the resulting (HPB-PEK)-g-VGCNF nanocomposites and the endgroup effect on some of their physical properties, the 10wt% (HPB-PEK)-g-VGCNF bearing carboxylic-acid endgroups were converted to benzothiazole, dodecyl ester and amine endgroups. For example, the dodecyl- terminated nanocomposite displayed an excellent solubility in chloroform and a much lower Tg than the CO2H-terminated analog. The overall evidence was based on the data from elemental analysis, thermogravimetric analysis (TGA), Fourier- transform infrared spectroscopy (FT-IR), nuclear magnetic resonance (NMR), scanning electron microscopy (SEM) as well as transmission electron microscopy (TEM).