Poly(2,5-benzoxazole)/carbon nanotube composites via in situ polymerization of 3-amino-4-hydroxybenzoic acid hydrochloride in a mild poly(phosphoric acid)

Poly(2,5-benzoxzole) (ABPBO)/carbon nanotube (CNT) composites were prepared via in situ polycondensation of “protonated” AB monomer, 3-amino-4-hydroxybenzoic acid hydrochloride, in a mildly acidic poly(phosphoric acid) medium. In situ generated hydrochloric acid during the dehydrochlorination process provided additional acidity to the reaction medium. The enhanced acidity was advantageous for both the purification and dispersion of CNTs. Specifically, it was evident for the purification of as-received single-walled carbon nanotube (SWCNT), which was contained a large portion of impurity (60-70 wt%). On the basis of the data obtained from elemental analysis (EA), thermogravimetric analysis (TGA), infrared spectroscopy (FT-IR), and X-ray diffraction (XRD) as well as scanning electron microscopy (SEM) and transmission electron microscopy (TEM), the resultant composites implicated that individual tube of multi-walled carbon nanotube (MWCNT) and bundles of SWCNT were homogeneously dispersed into the ABPBO matrix. After in situ polymerization in harsh temperature at 175 °C and subsequent work-up processes, CNTs were remained structurally intact in a mild reaction medium. Thus, the PPA medium is indeed viable for the preparation of composite.