Reorganization of the chain packing between poly(ethylene isophthalate) chains via coalescence from their inclusion compound formed with γ‐cyclodextrin

J Polym Sci B Polym Phys

2009

Cyclodextrins (CDs) are cyclic starches containing a-1,4-linked glucose units. Commonly available a-, b-, and c-CDs have six, seven, and eight glucose units, respectively. They are well known for forming 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. Warm water washing of crystalline CD-ICs containing polymer guests insoluble in water or treatment with amylase enzymes serve to remove the host CDs and result in the coalescence of the guest polymers into solid bulk samples. When guest polymers are coalesced from their CD-ICs by carefully removing the host CD lattices, they are observed to solidify with structures, morphologies, and even conformations that are distinct from bulk samples made from their solutions and melts. In addition, molecularly mixed, intimate blends can be obtained upon coalescence of two or more normally immiscible polymer guests from their common CD-ICs. Not only are the organizations and behaviors of bulk polymer samples significantly modified on coalescence from their CD-ICs, but both are also maintained for significant periods of time even when heated above their T g s and T m s, where their chains are mobile. Here, we discuss the long-time, high temperature stabilities of the organizations and properties of bulk polymers coalesced from their crystalline CD-ICs. While random-coiling of their initially coalesced, largely extended, separated, and unentangled chains may be relatively rapid, we conclude that the subsequent slow establishment of homogeneous melts or phase-segregated blends results from the extremely sluggish center-of-mass diffusion that must accompany full entanglement of their chains. Apparently, the process of entangling the largely separated and not fully interpenetrating randomly coiled chains initially coalesced from their CD-ICs is particularly slow, much slower in fact than the center-of mass diffusion of polymer chains in their fully entangled melts. V V C 2009 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys

Section: Coalesced Neat Polymerssupporting

confidence: 92%

Section: Coalesced Neat Polymersmentioning

confidence: 94%

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Organizational stabilities of bulk neat and well‐mixed, blended polymer samples coalesced from their crystalline inclusion compounds formed with cyclodextrins

J Polym Sci B Polym Phys

2009

“…The glass transition temperature of poly(ethylene isophthalate) (PEI) coalesced from its γ-CD-IC is ∼15-20 • C higher (∼70 • C) than that of the as-synthesized PEI, though both appear completely amorphous [58]. Typically polymer chains in amorphous regions start to move at the glass transition temperature.…”

Section: Pei [58]mentioning

confidence: 99%

Molecular Processing of Polymers with Cyclodextrins

Advances in Polymer Science

2009

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.

“…In the past several years, we have demonstrated that it is possible to obtain bulk polymer samples whose structures, morphologies, and even chain conformations are significantly altered from those obtained by processing randomly coiling, entangled polymers from their solutions and melts by the usual techniques. By first forming inclusion compound (IC) crystals between guest polymers and host cyclodextrins (CDs),1–72 and then coalescing the guest polymer chains from the polymer‐CD‐ICs through removal of the host CD crystalline lattice,10, 11, 17–23, 25, 27, 28, 30–35, 37–41, 44–46, 51 we find the resulting coalesced bulk samples to be significantly reorganized. For example, we generally observe that (i) crystallizable homopolymers coalesced from their CD‐ICs evince increased levels of crystallinity, unusual polymorphs, and higher melting, crystallization, and decomposition temperatures,21, 23, 27, 31, 32, 37, 40 while coalesced amorphous homopolymers exhibit higher glass transition temperatures17, 22, 47 than samples consolidated from their disordered solutions and melts; (ii) molecularly mixed, intimate blends of two or more polymers that are normally believed to be immiscible can be achieved by coalescence from their common CD‐IC crystals,10, 17, 22, 28, 33, 34, 38, 44, 48 (iii) the phase segregation of incompatible blocks can be controlled (suppressed or increased) when block copolymers are coalesced from their CD‐IC crystals,18, 20, 25, 35 and (iv) the thermal and temporal stabilities of the well‐mixed homopolymer blends and block copolymers obtained by coalescence from their CD‐ICs appear to be substantial,10, 17, 21, 32, 33, 38, 44 thereby suggesting retention or reformation of their as‐coalesced structures and morphologies under normal thermal processing conditions.…”

Section: Introductionmentioning

confidence: 98%

Reorganization of poly(ethylene terephthalate) structures and conformations to alter properties

Vedula

J Polym Sci B Polym Phys

2007

The solid-state morphologies, structures, and chain conformations of poly (ethylene terephthalate) (PET) have been reorganized/altered from those normally produced by solution and melt processing. This has been achieved by two distinct methods: (1) formation of a crystalline inclusion compound (IC) between guest PET and host c-cylodextrin (c-CD), followed by removal of the host c-CD and coalescence of the guest PET (c-PET) and (2) rapid precipitation of PET from a warm trifluoracetic acid solution into a large excess of rapidly stirred acetone (p-PET). Our prior observations (FTIR, NMR, DSC, X-ray) demonstrated that c-PET processed in this manner has a morphology, structure, and non-crystalline chain conformations that are quite distinct from those of as-received PET (asr-PET). Where possible to compare, here we find that c-and p-PETs behave very similarly, but very distinctly from asr-PET. The reorganized c-and p-PETs were found to be repeatedly rapidly crystallizable from the melt with a high level of crystallinity, and in their non-crystalline regions to have tightly packed chains predominantly adopting highly extended kink conformations, which evidence no glass-transition behavior. What is most unusual and somewhat puzzling is that their contrasting structures, morphologies, conformations, and thermal responses were observed to be independent of melt annealing, and persisted even after holding both samples above T m for extended periods (hours). p-PET, which can be produced in larger quantities than c-PET, was utilized to measure additional macroscopic properties, such as melt viscosities, densities, and the stressstrain and thermal shrinkage of melt-pressed films, for comparison to those of asr-PET. V V C 2007 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 45: [735][736][737][738][739][740][741][742][743][744][745][746] 2007