Additive-CD-ICs

Nanostructuring/Functionalizing Polymers via CD-IC Formation and Coalescence and Additive Delivery with Additive-CD-ICs and -Rotaxanes... 

It is possible to more effectively deliver small-molecule additives to polymers by employing either crystalline additive-CD-ICs or additives that are permanently complexed/rotaxanated with CDs and that remain soluble. Additive-CD-IC complexes may be delivered by melt-processing up to temperatures of 300°C, while the permanently threaded and soluble additive-CD-rotaxanes can be delivered from their solutions. 

Because crystalline CD-ICs are high-melting and thermally stable, even when containing small-molecule guests that are volatile liquids [52, 53] or even gases in the bulk, delivery of additives to polymer materials can be improved by using additive-CD-ICs, which may often be conveniently melt-processed into polymers. An example of CD-IC delivery of a polymer additive is provided by the commercial antibacterial triclosan [17]. 

The behaviors and properties of polymers may also be modified with CDs and additive-CD-ICs. Because CD-ICs formed with smaU-molecule additives, such as antibacterials and flame retardants, are stable to temperatures beyond 250 °C, they may be compounded intact into many molten polymers. In this manner antibacterial and flame-retardant polymer fibers and films have been achieved. 

By way of the many examples discussed above, it should be clear that solid polymers may be effectively nanostructured by processing with CDs. Polymer solutions and gels may also be modified/controlled with CDs, and various functionalities may be delivered to them in the form of additive-CD-ICs. Finally, CDs may be covalently incorporated into polymers to provide them with permanent capabilities to bind and/or release a host of active agents. 

In addition, native cage a-CD was suspended in acetone solutions of the PEGs, and its solid-state conversion to channel structure as PEG chains were included and formed PEG-a-CD-IC crystals was observed by solution 1H NMR. The rate of PEG inclusion from solution was 10-times faster than the rate observed for the neat PEGs, even though the PEG concentration in solution was only 1% that of neat PEG. 

In summary, microscopic and thermal observations of PET samples coalesced from their crystalline y-CD-IC suggest crystalline characters and melt-crystallized morphologies that are different from normal samples. After coalescence of their segregated, extended chains from the narrow channels of the crystalline inclusion complex formed with host y-CD, PET chains are much more readily crystalliz-able, and, locally, quickly form small, possibly chain-extended crystals. In addition, the noncrystalline regions of coalesced PET exhibit conformational and motional... 

There is an important additional advantage of using (n-s) polymer-CD-ICs to nucleate the melt-crystallization of polymers. Because CDs are nontoxic, biocompatible, and biodegradable, they may be safely utilized in (n-s) polymer-CD-IC nucleants to fabricate both permanent and biodegradable/bioabsorbable implants that are also nontoxic. 

We also observed that the PC chains possess a preferred ability to form inclusion compounds with y-CD in solution, when competing with PMMA and PVAc. From the XH NMR spectrum of the coalesced 1 1 1 PC/PMMA/PVAc blend (not shown), the molar ratio of PC PMMA PVAc was determined to actually be 1.6 1 1.4 compared to the initial molar ratio of 1 24 24, respectively, used in solution to form their common y-CD-IC. Despite the initial 1 24 24 PC PMMA PVAc molar ratio in solution, the PC component in the coalesced PC/PMMA/PVAc blend is still prevalent over the PMMA and PVAc components, which indicates that there may be additional factors that govern the inclusion process from a multiguest system. We believe that this very strong preference of the host y-CD molecules for PC chains, rather than the other two possible guests, is due to their different hydrophobicities. Although the final molar ratio of the coalesced ternary blend can be somewhat controlled by modifying the initial molar ratio of polymers in their common solution, our eventual aim is to be able to adjust, as desired, the constituent polymer ratios in coalesced ternary blends. 

These results give further impetus to our belief that a variety of additives may be more effectively delivered to polymer films and fibers as high melting inclusion compounds formed with CDs. In this connection for flame retardants, which can be toxic and mutagenic on contact, their confinement in CD-ICs not only protects them from the environment, but protects the wearer of fabrics containing embedded FR-CD-ICs from direct contact with the FR. Thus, one can envision the use of the most effective FRs with little regard to issues of FR toxicity, if they are delivered in the form of their CD-ICs. 

These star polymers with y-CD cores have the ability to complex with a variety of additives via formation of CD-ICs. They may also be able to be blended with a second normally incompatible polymer, such as PDMS, with a strong propensity to thread through and complex with their y-CD cores [14], Both of these potential applications are illustrated schematically in Fig. 33. 

We have demonstrated that the structures, morphologies, and even chain conformations of solid polymer samples may be altered by including them in and then coalescing them from their CD-ICs. In addition to altering their physical behaviors, coalescence of guest polymers from their CD-ICs permits us to obtain solid polymer samples that are distinct from bulk samples made from their solutions and melts. Clearly study of such reorganized coalesced polymer samples can contribute to our ability to understand and develop improved structure-property relations for them. 

Vedula J, Tonelli AE (2007) J Polym Sci B Polym Phys Ed 45 735 (Here the slow addition of a heated trifluoroacetic acid solution of PET into rapidly stirred acetone resulted in a precipitated PET sample (p-PET) whose physical behaviors closely parallel those of PET coalesced from its y-CD-IC.)... 

In order to control an IC system, a chromatography data system (CDS) is usually needed. In addition to IC systems, some of these CDSs can also control gas chromatography (GC) and HPLC... 

Generation of the enolatc is followed in each case by addition of 1.1 equiv of TMSCI, warming to r.t. over 1 h, addition of CH,OH and stated workup. b Ratios determined by (iC analysis of methyl esters on a 6 m 13 % Carbowax 20-m column using a Vari-an CDS-111 integrator. 

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