Adamantane polymer structures

The value of characterises the polymer chain statistical flexibility and the degree of macromolecular coil compactness [25]. In Figure 5.5 the dependences CJcJ for modified EP are adduced. As follows from the data of Figure 5.5, more intense raising of is observed for EP-4 than for EP-3, which is due to the differences in the structures of these epoxy polymers. In the EP-4 case the adamantane fragment is built by two bonds into the network or partly forms a card polymer structure. For EP-3 the card polymer structure with one bond at the adamantane fragment is the most probable. Therefore, for macromolecular coil card elements of EP-4 chain structure are more effective in the role of steric hindrances. They do not allow to achieve the same degree of macromolecular coil compactness as do non-modifled EP-1 and EP-2 or EP-3. 

Compound 3 is an example of a star polymer with benzoxazole arms. The three dimensional rigid-rod polymer was obtained from the polycondensation of 4-[5-amino-6-hydroxybenzoxazol-2-yl]benzoic acid (ABA) with l,3,5,7-tetrakis(4-carboxylatophenyl)adamantane (TCBA) in polyphosphoric acid (PPA). Polymer structures were confirmed by FTIR and elemental analysis, although the extent of attachment of PBO arms to the adamantane core was not confirmed. In addition, stir opalescence was observed indicating lyotropic-like behavior. However, the more compact star structure resulted in intrinsic viscosities that were significantly less than linear PBO s obtained under identical conditions. The onset for weight loss under TGA in air occurred at 500 C for both linear and star polymers and no transitions were observed by DSC. 

Hexamethylenetetramine is a co-polymer (oligomer really such as those we met in Chapter 52) of formaldehyde and ammonia containing six formaldehyde and four ammonia molecules. It has a beautifully symmetrical cage structure belonging to the adamantane series. 

Cinnamoyl- 6-CD (6-CiO-/3-CD) was sparingly soluble in water, although most 6-substituted 6-CDs are soluble. However, 6-CiO-/3-CD was solubilized in water on the addition of adamantane carboxylic acid or p-iodoaniline which could be included in a 6-CD cavity. These results suggest that 6-CiO-/l-CD formed supramolecular polymers in the solid state, as shown in the proposed structure in Fig. 17. The X-ray powder pattern of 6-CiO-/l-CD was similar to that of the complex between p-CD and ethyl cinnamate, in which /3-CDs formed a layer structure. The crystal structure of 6-aminocinnamoyl-/3-CD (6-aminoCiO-/l-CD) is shown in Fig. 12 and we discussed the relationship between crystal packing and the substituent group in Sect. 2.8. 

CHART 12.5 Structures of monomers and polymers employed in photolithography in 193 nm optical lithography. Most polymers are co-, ter-, and AVra-polymers of norbomenes bearing various substituents, /er Abutoxy ac ry I ales, adamantane, and maleimide. 

An obvious approach to render these rigid-rod polymers colorless is to synthetically alter their molecular structures so as to disrupt their conjugation systems. This modification is, of course, predicated on imposing little or no adverse effects on the other important properties of the polymers, for example, environmental survivability. Cage-like, aliphatic hydrocarbon molecules, such as adamantane, diamantane, cubane, etc., are thermally stable, and non-chromophoric due to the lack of 7t-electrons. Some of these cage molecules can be synthesized as difiinctionalized monomers that also satisfy the all-para molecular geometry requirement of rigid-rod macromolecules. 

Last, weak guest—host interactions, such as those between adamantane and P-cyclodextrin (Rodell et al., 2013), are also reversible by exposure to shear stresses. They can be used to create bioinks that are a gel while in the cartridge, but they are fluid when extruded through a needle before returning to their gel state upon deposition onto a substrate. Polymers that exhibit reversible gelation behavior are mostly used in printing applications as transient structures such as sacrificial molds (Muller et al.,... 

It is known that the introduction of adamantane fragments in epoxy polymers exercises an essential influence on their characteristics. In papers [19,20] the effect of such network structures is examined in the example of EP modified by adamantane acids. The interpretation of the results obtained in [19, 20] within the frameworks of the cluster model of the amorphous state structure of polymers [5, 6] allows to suppose availability of two types of clusters in the studied EP stable ones, formed by main chain segments, and unstable ones, formed at the expense of the interaction of adamantane fragments. The authors of papers [21-23] studied the problem of how much the indicated notions corresponded to the real structure of the studied EP. This can be carried out with the aid of the methods of [3], based on the study of wide angle X-ray halos. 

Polymer 4 was partially soluble in DMSO and amide solvents such as DMF and DMAc. Solution and solid-state NMR were used to confirm the product structure. Peaks due to the adamantane moiety and aramid carbonyls were present indicating reaction. Again, residual solvent peaks were observed in the solid-state NMR spectra, even after extensive extraction and vacuum drying. It appears that hyperbranched structures and adamantane incorporation disrupts crystalline packing and leads to a more open and molecularly-porous branched structure that is capable of taking up and holding solvent. 

The incorporation of adamantane into various types of polymer ows some promise for thermal property enhancement without sacrificing processability. The overall approach is twofold on the one hand, to use the tetrahedral geometry of adamantane to enforce three dimensional structures, and on the other to use bulky pendant adamantanes to promote solubility, maintain thermal stability, and raise glass transition temperatures. We believe both approaches offer valuable methods for modifying physical and mechanical properties of commercially important polymers, and we hope to continue to explore such opportunities. 

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