Inclusion complexes polymer chain

Homopolymerization of the olefin occurred if its basicity was higher than that of 2-furaldehyde, i.e. the initiator displacement from the complex was strong and thereafter only occasional inclusion of aldehyde in the growing polymer chain took place 2-furaldehyde units in the products were less than 5%. This situation was observed with acenaphthylene and N-vinylcarbazole. 

The inability of y-CD to complex with POx under the same conditions as for / -CD indicates the failure of POx to meet the prerequisite for inclusion complex formation that the polymer chain fits well into the CD cavity and is hydrophobic enough to stabilize the complex. 

The aqueous solubility of CD also enables their potential application as poly-rotaxane-based drug carriers. Yui and coworkers incorporated CD onto PEO chains in polypseudorotaxanes and polyrotaxanes [92-94], The releasing kinetics of CD from the polymer chain were studied. The release was governed by the inclusion complexation equilibrium. Biodegradation to cleave the BG units was shown to cause the release of the CD from the polyrotaxanes. 

Inclusion properties of molecular nanotubes composed of crosslinked a-cyclodextrin was investigated [47], Induced circular dichroism was used to probe the formation and dissociation of complexes between the nanotubes and azobenzene modified polyethylene glycol), either with or without a hydrophobic alkyl chain. The inclusion complex between the nanotubes and polymers formed at room temperature, and the polymers dissociated from the nanotubes with increasing temperature. 

Potential use of complexes of y - CD with organic compounds, including polymers, was also reviewed by Szejtli [6, 12, 13], y - CD are able to incorporate metal ions as ligands to prepare magnetic nano - particles [7,14], Harada and Ka-machi [8,15] first found that poly (ethylene oxide) (PEO) thread a- CD rings to form polymer - cyclodextrin complex. Since their finding of inclusion complex formation of polymer chains with a- CD, a large number of studies on inclusion complexes of... 

Figure 4.6 shows the schematic diagrams of ciclodextrins, polyaniline with emeraldine base, and inclusion complex formation of cyclodextrins and a conducting polymer chain insulated molecular wire. 

The driving forces of complex formation were thought to be the geometric compatibility or fit and intermolecular interaction between hosts and guests. It has been reported that many linear polymeric guests could form inclusion complexes with CDs resulting in main-chain pseudopolyrotaxanes. When the polymers were added into the CD solutions and then sonicated, crystalline inclusion complexes precipitated. As the result of X- ray diffraction study, all crystalline inclusion complexes between CDs and polymeric guests are columnar in structure [27,43],... 

As Tonelli et al. [44,45] have pointed out, the study of crystalline inclusion complexes provides an approach to investigate the behaviors of single polymer chains in isolated and well - defined environments. Then, it is helpful in understanding the mechanism of molecular recognition between hosts and polymeric guests. 

Molecular model studies have shown that PMVE, PEVE, and PnPVE chains are capable to penetrate y -CD cavities. Model studies further indicate that the single cavity can accommodate three monomer units. The inclusion complex formation of polymers with cyclodextrins is entropically unfavorable. However, formation of the complexes is thought to be promoted by hydrogen bond formation between cyclodextrins. Therefore, the head - to - head and tail - to - tail arrangement, which results in a more effective formation of hydrogen bonds between cyclodextrins, is thought to be the most probable structure. This structure was proved by X-ray studies on a single crystal of the complex between y -CD and 1-propanol. 

Crystalline inclusion complexes (IC s) have been also formed between polymers and another small-molecules, host clathrated provide a unique environment for observing the solid - state behavior of isolated polymer chains. In their IC s with small-molecule, host clathrates, such as urea (U) [1] and perhydrotriphenylene (PHTP) [57], the included polymer chains are confined to occupy narrow channels (ca. 5.4 A in diameter) where they are extended and separated from neighboring chains by the channel walls, which are composed exclusively of the host clathrate, crystalline matrix. Choi et al. [58] have been studied the behavior of isolated, extended polymer chains included in their IC s with U and PHTP by a combination of molecular modeling [59,60] and experimental observations in an effort to determine their conformations and mobilities in these well-defined, containing environments. 

Ritter et al. [147-155] have been studying side chain poiyrotaxanes. They synthesized side chain poiyrotaxanes by amide coupling of polymer-carrying carboxylic acid moieties with various semirotaxanes of methylated /l-CD(s) and an axle bearing an amine group at one end [147-154]. These works have been reviewed in an excellent review by Raymo and Stoddard [78]. Ritter et al. [155] reported recently a new type of side chain polyrotaxane. They polymerized inclusion complexes of di(meth)acrylates of butan-l,4-diol and hexan-l,6-diol with a-CD and with methylated /1-CD using a redox initiator system in aqueous media, and characterized the polyrotaxane structure by IR and glass-transition temperature measurements. 

Steady-State fluorescence and circular dichroism (cd) spectroscopies [157]. (l-Naphthyl)methyl and (2-naphthyl)methyl side chains interacted most considerably with j6-CD. Cd spectra indicated that P-CD included polymercarrying INp groups shallowly, but it included deep polymer-carrying 2Np groups to form inclusion complexes, in which the longer axis of the 2Np group is rather parallel to the rotation axis of P-CD. 

It was found meanwhile that nearly every slim unbranched polymer chain, such as poly(trimethylene oxide) [224], poly(l,3-dioxolane) [225], poly(tetramethylene oxide) [226], polyethylene imine) [227], poly(3-hydroxy propionate), poly (4-hydroxybutyrate) and poly(6-hydroxyhexanoate) [228,229], poly(butylene succinate) [229], polyadipates [230], nylon-6 [231], and even oligomers of polyethylene [232], form a-CD ICs with channel structures. In all of these cases, inclusion is a heterogeneous process, since the guest polymer and its CD complex are almost insoluble in water. Therefore, extensive sonication had to be applied to accelerate the diffusion process. The polymer was also dissolved in an organic solvent, e.g., nylon-6 in formic acid, and this solution was added to the solution of a-CD [231], Alternatively, a monomer, such as 11-aminoundecanoic acid, was included in a-CD and polymerized to nylon-11 by solid state polycondensation within the channels of the IC. Thus, the IC of nylon-11 was formed under conservation of the crystal packing [233-235],... 

The overwhelming interest on the developments of CD inclusion polymers arose since the discovery of a-CD inclusion complexes with PEO of different molecular weights [16] and the subsequent synthesis of the polyrotaxanes composed of multiple a-CD rings threaded and entrapped on a polymer chain (Fig. 2) [17,18], So far, a large number of reports have been published on the CD-based polypseudorotaxanes and polyrotaxanes [12,18 19] and their applications in biomaterials [50-58],... 

The advances in the studies on the inclusion complexes of CDs threading onto polymer chains have led to interesting development of supramolecular hydrogels with many different molecular and supramolecular structures. Both physical and chemical hydrogels of many different types were developed based on the CD-based polypseudorotaxanes and polyrotaxanes. 

Poly(benzimidazole) can be used as the reactive polymer for the preparation of side chain-type polyrotaxane via the alkylation on nitrogen. Osakada et al. showed that deprotonation of poly(benzimidazole) followed by N-alkylation with alkyl bromide-terminated pseudorotaxane consisting of 2,3,6-trimethyl-/1-cyclodextrin gave a novel side chain-type polyrotaxane (Scheme 38) [206]. Poly(benzimidazole) having a long -hydroxyalkyl group as the side chain can form an inclusion complex with 2,3,6-trimethyl-/l-cy-... 

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