Carbon nanotubes functionalizing esterification

Acyl chloride-functionalized SWCNTs are also susceptible to reactions with other nucleophiles, e.g. alcohols. Haddorfs group reported the preparation of soluble ester-functionalized carbon nanotubes SWCNT-COO(CH2)17CH3 (Fig. 1.6a) obtained by esterification with octadecanol [134]. The syntheses of soluble polymer-bound and dendritic ester-functionalized SWCNTs have been reported by Riggs et al. by attaching poly(vinyl acetate-co-vinyl alcohol) (Fig. 1.6b) [135] and hydrophilic and lipophilic dendron-type benzyl alcohols [119], respectively, to SWCNT-COC1 (Fig. 1.6c). These functional groups could be removed under basic and acidic hydrolysis conditions and thus additional evidence for the nature of the attachment was provided [119, 136]. 

One of the first examples of the grafting to approach was published by Sun et al. in 2001 [32]. In this work carboxylic acid groups on the nanotube surface were converted into acyl chlorides by refluxing the samples in thionyl chloride. Then the acid chloride functionalized carbon nanotubes were reacted with hydroxyl groups of dendritic PEG polymers via esterification reactions. Similarly, many polymers terminated with amino or hydroxyl moieties have been used in amidation and esterification reactions with acid chloride modified NTs poly(propionylethylenimine-co-ethylenimine) (PPEI-EI) [33], poly(styrene-co-aminomethylstyrene) (PSN) [34], poly-(amic acid) containing bithiazole rings [35], monoamine-terminated poly(ethylene oxide) (PEO) [36], poly(styrene-co-hydroxymethylstyrene) (PSA) [37], poly(styrene-co-p-[4-(4 -vinylphenyl)-3-oxabutanol]) (PSV) [38], poly(vinyl alcohol) (PVA) [39], poly(vinyl acetate-co-vinyl alcohol) (PVA-VA) [40] or poly[3-(2-hydroxyethyl)-2,5-thienylene] (PHET) [41]. 

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