Assessing the Role of Poly(ethylene glycol-bl-propylene sulfide) (PEG-PPS) Block Copolymers in the Preparation of Carbon Nanotube Biocompatible Dispersions

Abstract

Amphiphilic block copolymers based on hydrophobic polysulfides (poly(propylene sulfide), PPS) and hydrophilic polyethers (poly(ethylene glycol), PEG) have been used to solubilize and disperse single-walled carbon nanotubes (SWNTs). The obtained highly concentrated aqueous dispersions are stable for months. The factors that affect the dispersant activity of the studied block copolymers have been characterized, and comparisons with the much more investigated oxygen analogues (Pluronics) are reported. The biocompatibility and the stability after dilution of the most representative suspensions have been investigated as prospective drug carriers.

Non-covalent and reversible functionalization of carbon nanotubes

“…The wrapping of the SWCNTs by water-soluble polymers is a thermodynamically driven phenomenon because the free energy cost of forcing the polymer into a regular wrapping around the nanotube appears to be well counterbalanced by the reduction of the hydrophobic penalty consequent to the contact of CNT hydrophobic surface with the surrounding aqueous medium. Also in the case of polymers and similarly to what has already been underlined for classical surfactant molecules, we have demonstrated [ 70 ] that polymeric micelles concentration is not related to the formation of stable SWCNT dispersions, the outmost requirement in order to obtain a stable CNTs dispersion being the adsorption degree, up to an almost complete saturation, of the nanotube surface with proper dispersant molecules. Molecular dynamic simulations allowed us to highlight that the SWCNT surface coverage is systematically ensured by the hydrophobic domain of the amphiphilic dispersant.…”

pH responsive MWCNT–star terpolymer nanohybrids

“…Solubilization of CNTs by micelle encapsulation has been accomplished using a PS-b-PAA copolymer. 28 The ability of block copolymers to wrap CNTs has been exhibited by triblock copolymers like PNIPAM-b-PS-b-PNIPAM, 70 poly(ethylene-cobutylene)-b-poly(methyl methacrylate-co-pyrene methyl 2-methyl-2-propenoate) diblocks 71 and amphiphilic pluronic PEO-b-PPO-b-PEO 33,34 (where PPO: poly(propylene oxide)) and poly(ethylene glycol)-b-poly(propylene sulde) 35 copolymers. Physical adsorption of a PS-b-PMAA copolymer on CNTs was realized by a non-wrapping mechanism.…”

“…Several reports have been published including non-covalent functionalization of CNTs with either positively or negatively charged polyelectrolytes, 22 polymers such as poly(acrylic acid) (PAA), 23 poly(ethylene oxide) (PEO), 24 polyethers, 25 as well as amphiphilic random 26,27 or block copolymers. [28][29][30][31][32][33][34][35] Fewer are the studies on the utilization of stimuli responsive polymers to disperse CNTs. Common pH responsive weak polyelectrolytes such as PAA, poly(methacrylic acid) (PMAA) and poly(allylamine) (PAAm) were used to prepare pH tunable SWCNT-polymer dispersions that depend on the degree of ionization of the polymeric chain.…”

Biocompatible dispersions of carbon nanotubes: a potential tool for intracellular transport of anticancer drugs

“…It has been previously demonstrated 7 that the amphiphilic block copolymers poly(ethylene glycol-b-propylene sulfide) [PEG-PPS] favour a better disentanglement and dispersion of single-walled carbon nanotubes (SWNTs) in aqueous solution than can be obtained with the widely investigated Pluronics. The good suspendability of SWNTs in PEG-PPS was attributed to the steric stabilization brought about by the PEG chains that flank the adsorbing hydrophobic PPS block.…”

“…The good suspendability of SWNTs in PEG-PPS was attributed to the steric stabilization brought about by the PEG chains that flank the adsorbing hydrophobic PPS block. 7,8 Furthermore, cytotoxicity studies highlighted the biocompatibility of PEG-PPS coated SWNT suspensions up to a nanotube concentration of 50 mg mL À1 , a concentration comparable to that of hydrophilically functionalized CNTs. 9 The presence of PEG chains into the block copolymer endows CNTs with a hydrophilic coating, which also reduces protein adsorption and phagocytosis, thus lengthening their blood circulation time.…”