Functional grafting techniques

Because the grafting techniques described in Section 3.5.1.2 lead to rather low loading, it is of interest to incorporate functional groups directly and in large amounts into a material via a sol-gel process. Open and patent literature report colloidal silicas [23], aerogels [24] and xerogels [14] with 3-mercaptopropyl, 2-phenylethyl, or benzyl functional groups. These materials are valuable precursors to sulfonated polysiloxanes (Section 3.3). 

During this work, we analyzed the organization, the morphology, and the preferential adsorption of these copolymers and how these properties would be influenced by the interfacial interactions that could be established between the polymer and the chemical functionalities grafted onto the adsorption substrate. Our results were mainly based on two surface techniques polarization-modulation infrared reflection-absorption spectroscopy (PM-IRRAS) and atomic force microscopy (AFM). 

Polymer Grafting of Carbon Nanotubes by Con-trolled/Living Radical Polymerization Polymer grafting techniques that use direct covalent functionalization methods, such as radical reactions, have been developed in order to avoid the problems associated with the functionalization of CNTs using acids. These grafting techniques eliminate the need for nanotube pretreatment before the functionalization and allow attachment of polymer molecules to pristine tubes without altering their original structure. 

Mochalin et al modified their procedure for linking octadecylamine to NDs via amide bonds [53] to link ethylenediamine to the surface of purified carboxylated NDs and to produce covalently bonded ND-epoxy composites [54,55]. Alkyl chains or polymers can be grafted onto NDs via the reaction of esterification or silanization [25,56-60]. Zhang et al. employed an approach for grafting polyimides from ND surface via acyl chloride functionalization. This technique provided a superior dispersion... 

In the same context, a critical review discusses the recent advances in graft polymerization techniques involving cellulose and its derivatives [137]. The study summarizes some of the features of cellulose structure and cellulose reactivity and describes the various techniques for grafting synthetic polymers from the cellulosic substrate. In addition to the traditional grafting techniques, the recent developments in polymer synthesis that allow increased control over the grafting process and permit the production of functional celluloses with improved physical and chemical properties, are highlighted. 

Spite of the simplicity of the copolymerization process, more tunable properties of the functionalized material can be achieved using grafting techniques, as they allow the independent tuning of the support characteristics and of the grafting points. Moreover, the control over the density of the grafted brushes can also be achieved by tuning the initial density of the initiator on the grafting surface. 

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