Polycondensation Approach

3 MWNT-g-HPGI 4 MWNT-g-HPG2 5 MWNT-g-HPG3 6 MWNT-g-HPG4  

1 free HPG1 2 free HPG2 3 free HPG3 4 free HPG4 5 free HPG5 6 free HPG6 

Wang and co-workers synthesized hyperbranched poly(amido amine) (PAMAM)-grafted MWCNTs via a step-by-step divergent methodology from amino-functionalized CNTs. The resulting adduct was well dispersible in polar solvents. Further modification of grafted PAMAM with fluorescein 

Baek and co-workers grafted hyperbranched poly(ether ketone)s (HPEKs) on to MWCNTs through an in situ polycondensation of A3 (trimesic acid) and B2 (phenyl ether) monomers in the presence of poly(phosphoric acid) and P2O5. Due to the globular molecular architecture of HPs, the morphology of the nanocomposites resembled mushroom-like clusters on MWCNT stalks . The HPEK-g-MWCNT nanocomposites were soluble in polar aprotic 

The HP-functionalized CNTs possess a high density of functional groups on their surfaces and afford a versatile platform for multifunctional integration. 

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As the synthetic approach to polydichlorophosphazene put forward by R. De Jaeger has been already described in several recent review articles [10,38,57, 172], in this paper we will illustrate only the polycondensation approach proposed by I. Manners and H. R. Allcock, together with the consequences of this reaction on the preparation of chain phosphazene copolymers (block copolymers) [220,223,224,232-234,240], and star polymers [222]. 

Generally speaking, we should note that the synthetic potentials of the polycondensation approach for the preparation of protein-like copolymers are only now beginning to be explored. Nonetheless, even the first results show promising directions for future synthetic developments that can hardly be reached through the polymerization processes. 

The principle of the second synthetic approach to polycatenanes, i.e. stepwise polycondensation, has been proposed by Shaffer and Tsay, but not experimentally demonstrated [42, 43], This approach has the advantage over multifunctional polycondensation that a linear polymer is formed before cyclization (Scheme 7). However, the second step, which consists of the cyclization of n macrocycles along the polymer chain 19, is likely, again, to give rise to an undefined network, containing some rotaxane and catenane units 21, similar to the multifunctional polycondensation approach. 

An experimental attempt towards polycatenanes 9, based on a strategy related to the stepwise polycondensation approach, was reported in the seventies. Karagoumis et al. took advantage of the interface between a nonpolar phase (air, CC14) and a polar phase (H2O, Hg) to orient alkanes a,oj-disubstituted with polar groups (Scheme 9) [45], The successive addition of macrocycles of ring sizes 15-60 atoms and of difunctional species, susceptible to reaction with the a,o>disubstituted al-... 

An interesting variant of the polycondensation approach involved the use of fluorescent dyes as the difunctional organic monomers. Thus, soluble, high molecular weight titanium polydyes (e.g., 4/ = 5.3 x 10 by lightscattering measurements for the titanium polymer derived from the diphenol monomer bromophenol blue) were synthesized in yields that depended on the reaction conditions and the dye used. Structural characterization was... 

In 2001, an efficient step-growth polycondensation approach, reminiscent of that used to prepare metal-metal-bonded polymers 217 and 218, was successfully developed to yield polyurethanes 225 with Mo2lt2 clusters in the backbone. " Well-characterized polymers with molecular weights of up to 136,000 (PDI = 3.1), which correspond to a number average of around 30 clusters per polymer chain, were obtained by means of this method. It involved treatment of a diol of the Mo2lt2 cluster with the diisocyanate OCN-R-NGO (R = aliphatic or aromatic spacer) in the presence of a tin catalyst. The unusual optical properties of organometallic clusters will drive applications-oriented work on these materials. " ... 

The thermal reaction of cobalt polymers 4.28 with isocyanates at 120 °C leads to 2-pyridone-containing polymers such as 4.30 [70]. Well-characterized, yellow polyesters 4.31 containing skeletal (cyclobutadiene)cobalt moieties in the main chain have been prepared by interfacial polycondensation approaches [73]. The use of solubilizing alkoxy substituents R afforded materials with Mn = 5,400-16,300 (PDI = 1.3-1.8). Analogous materials to 4.31 with a 1,3-disposition of the main-chain substituents on the cyclobutadiene ligands have also been studied [73, 74]. Thermotropic liquid crystallinity was detected by polarizing microscopy, with, in some cases, mesophases stable over the temperature range from about 110 to >250°C. 

Using a polycondensation approach, Ajayaghoh et al. [63] prepared water-soluble squaraine oligomers by condensation of squaric acid with... 

Polyamide 6/graphite nanocomposites with markedly low percolation threshold value were recently prepared using an in-situ polycondensation approach. Based on transmission electron microscopy (TEM) results, the thickness of EG filler incorporated in the polymer matrices was found to vary from 10 to 50 nm, and the aspect ratios (diameter to thickness) can be estimated as high as 100-300. The graphite used by Pan et al. is termed foliated graphite (FG). FG can... 

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