Single-Walled Carbon Nanotubes and Multiwalled Carbon Nanotubes Functionalized with Poly(l-lactic acid): a Comparative Study

Abstract

Spectroscopic (Raman) and gravimetric (acid titration, TGA) techniques were compared to determine the functionalization degree of multiwalled carbon nanotubes (MWNTs) and single-walled carbon nanotubes (SWNTs) with poly(L-lactic acid) (PLLA), following a two-step oxidation/esterification process. After oxidation with HNO 3 , carbon nanotubes (CNTs) were activated with thionyl chloride to the corresponding acid chlorides and then grafted with PLLA. FTIR spectroscopy confirmed the formation of very similarly grafted CNT-PLLA materials for both SWNT and MWNT. But, according to chemical titration and TGA results, oxidized and esterified SWNT showed a significantly higher degree of functionalization than their MWNT counterparts. Contrary to these observations, the increase of the Raman I D /I G ratio was higher for MWNT-derived materials than for the SWNT counterparts. Therefore, it was concluded that this spectroscopic technique is unsuitable for the quantitative determination of the degree of functionalization when MWNT and SWNT are compared.

New strategies for the chemical characterization of multi-walled carbon nanotubes and their derivatives

“…In some cases, however, it led to contradictory results. [44] The experimental setup of the Raman experiment might have an influence on the finally obtained spectrum. For example, increasing the laser power density leads to annealing of the structure defects of single-wall carbon nanotubes.…”

Functionalization of Carbon Materials using the Diels‐Alder Reaction

“…thionyl chloride). [18][19][20] Single step reactions like the in-situ polymerization in the presence of carbon nanofillers or the "grafting to" of functionalized polymers at the carbon nanofillers are the easiest alternatives for the preparation of nanocomposites, however, the control of the extent of functionalization of the nanofillers [21] and their dispersion in the polymer matrix are arduous. [22][23][24] Therefore, the development of simple methods for the controlled functionalization of carbon nanofillers and the posterior compounding with polymer using conventional mixing methods (e.g.…”

One-pot noncovalent method to functionalize multi-walled carbon nanotubes using cyclomatrix-type polyphosphazenes

“…4 But these polymers usually possess a linear or branched structure, which may lead to relatively unstable dispersions because of the intrinsically weak nature of the interactions between the coating polymer and the CNT. 5 In comparison with a linear or branched structure, a covalently cross-linked structure is a more effective approach to achieving good stability. However, research of using cross-linked polymers as coating layers of CNTs has only rarely been reported.…”