Fate and Transport of Nanomaterials in Aquatic Environments - Nanotechnologies for Water Environment Applications - page 539

copolymers (see Fig. 15.7) using the atom transfer radical polymerization (ATRP)
technique (Saleh et al., 2005). The hydrophobic terminal group may allow for easier
swelling in the vicinity of DNAPL whereas gradient and random hydrophobicity may
enhance affinity for DNAPL/water interface.
Figure 15.7 (Left) Block co-polymer chemistry PMAA-PMMA-PSS (anchoring-
hydrophobic-hydrophilic). (Right) Three architectures altering position and distribution
of hydrophobic PMMA block (adapted from Saleh, 2008).
The synthesis method of Saleh et al. (2005) for producing the triblock copolymer
structure is quite slow and sensitive to impurities and oxygen. In addition, catalyst
residues can be difficult to remove. To address the problems, Krajangpan et al. (2008)
synthesized a series of amphiphilic polysiloxane graft copolymers (APGCs) using a
process that consisted of hydrosilylation of tert-butylacrylate and monoallyl-functional
PEG to a polysiloxane copolymer containing hydride groups and subsequent hydrolysis
of the ferf-butylester groups. Treatment of NZVI with APGCs was found to enhance
NP's colloidal stability in water, and the magnitude of the enhancement was a function
of APGC chemical composition. The APGC possessing the highest concentration of
carboxylic acid anchoring groups provided the highest colloidal stability. In addition, the
hydrophobicity of the polysiloxane polymer backbone can protect the NZVI from
excessive oxidation by creating a barrier to water while also creating an affinity of the
coated NPs for the water/contaminant interface (Krajangpan et al., 2008).
Considerable research has been conducted for the development of NMs for
biomedical and biotechnological applications, with ^NMs as one of the major focuses.
Water-soluble /-CNTs interact with mammalian cells, leading to their cytoplasmic
translocation. Ammonium-functionalized cationic nanotubes condense and deliver
plasmid DNA (pDNA) intracellularly, leading to enhanced marker gene expression.
Other studies indicate that CNTs coated with proteins, polymers and single-stranded
DNA also interact with mammalian cells; the intracellular translocation of these
macromolecules are reported (Kostarelos et al., 2007). These studies demonstrate that it