Defect-group functionalization

Fig. 1.3 Functionalization pathways for SWNTs (a) defect-group functionalization, (b) covalent side-wall functionalization, (c) noncovalent exohedral functionalization with surfactants, (d) noncovalent exohedral functionalization with polymers, and (e) endohedral functionalization with, for example, C60. For methods (b)-(e), the tubes are drawn in idealized fashion, but defects are found in real situations. From [103] with kind permission of Wiley.

Fig. 1.2 Different possibilities for the functionalization of SWCNTs (a) noncovalent exohedral functionalization with polymers (b) defect-group functionalization (c) non-...

Newkome-type dendrons were attached to the carbon scaffold of SWCNTs and MWCNTs by defect group functionalization [108], First- and second-generation amine dendrons such as those depicted in Fig. 1.5 were condensed with the carboxyl groups of purified and opened SWCNTs and MWCNTs according to the car-bodiimide technique [108], These CNTderivatives can be expected to combine the characteristics of carbon nanotubes with those of dendrimers, potential building blocks for supramolecular, self-assembling and interphase systems. 

It is thus evident that the characteristics of nanocarbons (conductivity, local structure, presence of defects and functional groups, morphology, etc.) are critical to determining the properties of the hybrid nanomaterial with the semiconductor. However, most of the literature studies put emphasis on the analysis of semiconductor characteristics, while often nanocarbons are only described in generic terms (CNT, for example). Yet, it is well known how the properties of nanocarbons can be considerably different from case to case (depending on details in preparation), even if the structure is formally the same (MWCNT, for example). 

Adhesion between the reinforcing agent and matrix is important. Some matrix materials do not adhere well with certain fibers. This is partially overcome through introduction of defects or functional groups onto the nanomaterials that act as hooks to anchor them to the matrix material. 

Figure 2. Variation of the number of SiO- defect groups, as a function of the number of A1 atoms per unit cell of Nu-10 (numbers refer to the composition given in Table II).

The relative intensities of the different configurations so obtained are listed in Table VI. The number of SiOH groups at defect lattice sites per extracted Al atom is shown as a function of the number of extracted Al atoms per unit cell (Figure 15). In the beginning of dealuminaiion up to four SiOH defect groups per extracted Al atom are generated in the structure (56). 

Depending on the nmnber of pieces of equipment defect in functional group n, we incur downtime costs. For i 6 1,... pieces of defective equipment in group n we assmne that downtime costs of > 0 per time unit are incurred. These downtime costs will be estimated in the RCM study. Note that we are interested in the marginal costs of having a unit of extra downtime, the fixed repair costs should be excluded from c i since they are not affected by the number of spares. 

Figure 12.2 Several possible functionalization with polymers, (c) defect-group mechanisms for CNTs. (a) endohedral functionalization, (d) covalent sidewall...

Conversely, dramatic amounts of induced defects throughout functionalization hamper the intrinsic mobUily of carriers along CNTs, which is not desirable in any case (Naeimi et al. 2009 Liu et al. 2011 Zhong et al. 2011). The carboxylation technique not only functionalizes the CNTs exterior with COOH groups, but also leaves behind unfavorable stractures, thus hampering their potential for practical purposes (Zhong et al. 2011). This in turn compromises the mechanical properties of CNTs. Moreover the concentrated acids or strong oxidants often used for CNTs functionalization are environmental unfriendly (Liu et al. 2011). 

In termination, unsaturated and saturated ends are formed when the propagating species undergo disproportionation, head-to-head linkages when they combine, and other functional groups may be introduced by reactions with inhibitors or transfer agents (Scheme 1.2). In-chain defect structures (within the polymer molecule) can also arise by copolymerization of the unsaturated byproducts of initiation or termination. 

Minor (by amount) functionality is introduced into polymers as a consequence of the initiation, termination and chain transfer processes (Chapters 3, 5 and 6 respectively). These groups may either be at the chain ends (as a result of initiation, disproportionation, or chain transfer,) or they may be part of the backbone (as a consequence of termination by combination or the copolymerization of byproducts or impurities). In Section 8.2 wc consider three polymers (PS, PMMA and PVC) and discuss the types of defect structure that may be present, their origin and influence on polymer properties, and the prospects for controlling these properties through appropriate selection of polymerization conditions. 

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