The Nano-threading of Polymers

Rusa, Cristian C.; Rusa, Mariana; Peet, Jeff; Uyar, Tamer; Fox, Justin D.; Hunt, Martin A.; Wang, X.; Balik, C. M.; Tonelli, Alan E.

doi:10.1007/s10847-005-9038-1

Cited by 18 publications

(30 citation statements)

References 69 publications

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“…The mixture of α-CD with the reverse Tetronic, T90R4, generates similar diffraction peaks, but some of them are slightly shifted to lower angles compared to the direct poloxamines (for instance, the intense peak at 2θ = 19.9˚ is shifted to 19.6˚). In both cases, the presence of a strong diffraction peak at approximately 20˚ is the signature of a PPR, 54,55 and reflects the channel-like structure caused by the packing of CDs threaded onto the polymeric chain, which are stabilized by hydrogen bonding.…”

Section: Evidence Of Pseudo-polyrotaxane Formationmentioning

confidence: 99%

Pseudo-Polyrotaxanes of Cyclodextrins with Direct and Reverse X-Shaped Block Copolymers: A Kinetic and Structural Study

et al. 2019

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Pseudo-polyrotaxanes (PPRs) are supramolecular host-guest complexes constituted by the reversible threading of a macrocycle along a polymer chain, which offers potential applications in nanotechnology, drug delivery and biomaterials. We report the threading of cyclodextrins (CDs), cyclic oligosaccharides, onto X-shaped PEO-PPO block-copolymers, with two opposite presentation of their hydrophobic and hydrophilic blocks: Tetronic 904 (T904), and its reverse counterpart, Tetronic T90R4. We assess the effect of relative block position on the polymeric surfactants and cavity size of CD have on the composition, morphology, thermodynamics and kinetics of PPRs by using a combination of X-ray diffraction, Scanning Electron Microscopy (SEM), NMR, UV-Vis spectroscopy and Time-Resolved Small-Angle Neutron Scattering (TR-SANS). Solid PPRs with lamellar microstructure and crystalline channel-like structures are obtained with native CDs and both Tetronics above a threshold concentration of the macrocycle, which varies with the type of CD and surfactant. While γ-CD can form PPRs with both Tetronics, α-CD only form a PPR with T90R4 at high concentrations. The results can be explained in terms of the preferential complexation of α-CD with EO and γ-CD with PO monomers, which also has a direct impact on the kinetics of PPR formation. Thermodynamic parameters of the reaction were obtained from the analysis of the stoichiometries and threading times as a function of temperature by using a model based on the Eyring equation. Negative enthalpies and positive entropies are obtained in all cases, and reactions are thermodynamically most favorable in the case of α-CD with T904 and γ-CD with T90R4. TR-SANS experiments reveal an increase in the radius of gyration of the unimers over time, consistent with CDthreading and expansion of the PPR. Above the CMT, α-CD threads the unimers to form the PPR, with no effect on the structure of T904 micelles, whose volume fraction decreases due to the shift of micellization equilibrium.

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Section: Evidence Of Pseudo-polyrotaxane Formationmentioning

confidence: 99%

Pseudo-Polyrotaxanes of Cyclodextrins with Direct and Reverse X-Shaped Block Copolymers: A Kinetic and Structural Study

et al. 2019

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“…Before presenting and discussing our results concerning the processing of polymers with CDs, it seems appropriate to discuss several experiments designed to determine those factors important to the nanothreading of polymers with CDs during the process of forming polymer-CD-ICs, and which were recently summarized [55,73,74]. These include (1) the competitive CD threading of polymers with different chemical structures and molecular weights from their solutions containing suspended solid or dissolved CDs, (2) the threading and insertion of undiluted liquid polymers into solid CDs, and (3) suspension of IC crystals containing polymer A or B in a solution of polymer B or A and observation of the exchange of polymers between the solution 120…”

Section: Nanothreading Of Polymers [55 73 74]mentioning

confidence: 99%

“…al. [1] suggested, based on noncompetitive CD-IC formation studies, that there is a much lower probability of CD to find a chain-end for threading higher molecular weight polymers, than for lower MW polymers, thus causing the threading time to be drastically increased [1,55,73,74]. However, in competitive CD-IC formation with polymers of low and high MWs it was found that the CD-ICs formed contained predominantly the high MW polymer.…”

Section: Cd-star Polymers [114-118]mentioning

confidence: 99%

Molecular Processing of Polymers with Cyclodextrins

Tonelli

2009

Advances in Polymer Science

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We summarize our recent studies employing the cyclic starch derivatives called cyclodextrins (CDs) to both nanostructure and functionalize polymers. Two important structural characteristics of CDs are taken advantage of to achieve these goals. First the ability of CDs to form noncovalent inclusion complexes (ICs) with a variety of guest molecules, including many polymers, by threading and inclusion into their relatively hydrophobic interior cavities, which are roughly cylindrical with diameters of ∼0.5 − 1.0 nm. α-, β-, and γ-CD contain six, seven, and eight α-1,4-linked glucose units, respectively. Warm water washing of polymer-CD-ICs containing polymer guests insoluble in water or treatment with amylase enzymes serves to remove the host CDs and results in the coalescence of the guest polymers into solid samples. When guest polymers are coalesced from the CD-ICs by removing their host CDs, they are observed to solidify with structures, morphologies, and even conformations that are distinct from bulk samples made from their solutions and melts. Molecularly mixed, intimate blends of two or more polymers that are normally immiscible can be obtained from their common CD-ICs, and the phase segregation of incompatible blocks can be controlled (suppressed or increased) in CD-IC coalesced block copolymers. In addition, additives may be more effectively delivered to polymers in the form of their crystalline CD-ICs or soluble CD-rotaxanes. Secondly, the many hydroxyl groups attached to the exterior rims of CDs, in addition to conferring water solubility, provide an opportunity to covalently bond them to polymers either during their syntheses or via postpolymerization reactions. Polymers containing CDs in their backbones or attached to their side chains are observed to more readily accept and retain additives, such as dyes and fragrances. Processing with CDs can serve to both nanostructure and functionalize polymers, leading to greater understanding of their behaviors and to new properties and applications.

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“…It was hoped that, through the careful removal of the crystalline host CD lattice, the resulting coalesced polymer chains (c-polymers) would retain a significant degree of their included extended and un-entangled natures, so they would be organized in a manner quite different from samples processed from their solutions or melts, where they randomly coil and entangle. As we will now demonstrate, this has indeed been found to be the case [2,3,4,5,6,7,8,9,10,11,12,13,14,15,16,17,18,19,20,21,22,23,24,25,26,27,28,29,30,31,32,33,34,35,36,37,38,39,40,41,42,43,44,45,46,47,48,49,50,51,52,53,54,55,56,57,58,59,60,61,62,63,64,…”

Section: Introductionmentioning

confidence: 99%

Reorganizing Polymer Chains with Cyclodextrins

et al. 2017

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During the past several years, we have been utilizing cyclodextrins (CDs) to nanostructure polymers into bulk samples whose chain organizations, properties, and behaviors are quite distinct from neat bulk samples obtained from their solutions and melts. We first form non-covalently bonded inclusion complexes (ICs) between CD hosts and guest polymers, where the guest chains are highly extended and separately occupy the narrow channels (~0.5-1.0 nm in diameter) formed by the columnar arrangement of CDs in the IC crystals. Careful removal of the host crystalline CD lattice from the polymer-CD-IC crystals leads to coalescence of the guest polymer chains into bulk samples, which we have repeatedly observed to behave distinctly from those produced from their solutions or melts. While amorphous polymers coalesced from their CD-ICs evidence significantly higher glass-transition temperatures, T g s, polymers that crystallize generally show higher melting and crystallization temperatures (T m s, T c s), and some-times different crystalline polymorphs, when they are coalesced from their CD-ICs. Formation of CD-ICs containing two or more guest homopolymers or with block copolymers can result in coalesced samples which exhibit intimate mixing between their common homopolymer chains or between the blocks of the copolymer. On a more practically relevant level, the distinct organizations and behaviors observed for polymer samples coalesced from their CD-ICs are found to be stable to extended annealing at temperatures above their T g s and T m s. We believe this is a consequence of the structural organization of the crystalline polymer-CD-ICs, where the guest polymer chains included in host-IC crystals are separated and confined to occupy the narrow channels formed by the host CDs during IC crystallization. Substantial degrees of the extended and un-entangled natures of the IC-included chains are apparently retained upon coalescence, and are resistant to high temperature annealing. Following the careful removal of the host CD lattice from each randomly oriented IC crystal, the guest polymer chains now occupying a much-reduced volume may be somewhat "nematically" oriented, resulting in a collection of randomly oriented "nematic" regions of largely extended and un-entangled coalesced guest chains. The suggested randomly oriented nematic domain organization of guest polymers might explain why even at high temperatures their transformation to randomly-coiling, interpenetrated, and entangled melts might be difficult. In addition, the behaviors and uses of polymers coalesced from their CD-ICs are briefly described and summarized here, and we attempted to draw conclusions from and relationships between their behaviors and the unique chain organizations and conformations achieved upon coalescence.

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The Nano-threading of Polymers

Cited by 18 publications

References 69 publications

Pseudo-Polyrotaxanes of Cyclodextrins with Direct and Reverse X-Shaped Block Copolymers: A Kinetic and Structural Study

Pseudo-Polyrotaxanes of Cyclodextrins with Direct and Reverse X-Shaped Block Copolymers: A Kinetic and Structural Study

Molecular Processing of Polymers with Cyclodextrins

Reorganizing Polymer Chains with Cyclodextrins

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