Fabrication of Polymer Materials from Their Cyclodextrin Inclusion Complexes
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Date
2003-10-28
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Abstract
Inclusion complexed (IC) and coalesced biodegradable poly(ε-caprolactone) (PCL), poly(L-lactic acid) (PLLA), and their diblock copolymer (PCL-b-PLLA) were achieved by forming ICs between host α-cyclodextrin(α-CD) and guest PCL, PLLA, and PCL-b-PLLA, followed by removing the α-CD host with an amylase enzyme. The melting and crystallization behavior of these CD-IC treated polymers are investigated. Both isothermal and nonisothermal crystallization studies demonstrate that the PCL and PLLA blocks in the IC-coalesced samples are more readily and homogeneously crystallized than those in the as-synthesized samples or their physical blend, even though the level of crystallinity in the IC-coalesced diblock copolymer is significantly lower. Moreover, unlike the as-synthesized diblock copolymer, the crystallization of PCL and PLLA blocks in the IC-coalesced diblock copolymer are not influenced by their covalent connection.
Poly(ethylene terephthalate) (PET) and bisphenol A polycarbonate (PC) samples have been produced by the coalescence of their segregated, extended chains from the narrow channels of the crystalline inclusion complexes formed between the γ-cyclodextrin (γ-CD) host and PET and PC guests. Experimental observations of PET and PC samples coalesced from their crystalline ICs suggest structures and morphologies that are different from those of samples obtained by ordinary solution and melt processing techniques. PC crystals formed upon the coalescence of highly extended and segregated PC chains from the narrow channels in the CD host lattice are possibly more chain-extended and certainly more stable than chain-folded PC crystals. The coalesced PET melt rapidly recrystallizes during the attempted quench, and so upon reheating, it displays neither a glass transitions temperature (Tg) nor a crystallization exotherm but simply remelts at the as-coalesced melting temperature (Tm). An inclusion complex between nylon-6 and α-cyclodextrin was obtained and we attempted to use the formation and subsequent disassociation of the nylon-6/α-CD inclusion complex to manipulate the properties of nylon-6. Examination of as-received and IC coalesced nylon-6 samples show that dominated α-form crystalline phase of nylon-6 and a great increase in crystallinity are in the coalesced sample.
When inherently immiscible polymers are included as guests in the narrow channels of their common inclusion complexes formed with host cyclodextrins and then these polymer-1/polymer-2-CD-IC crystals are coalesced, an intimately mixed blends of the polymers are obtained. Polycarbonate (PC)/poly(methyl methacrylate) (PMMA) blends coalesced from their common γ-CD-ICs are amorphous and generally exhibit single glass transitions at temperature (Tg) between those of pure PC and PMMA. FTIR spectroscopy suggests an intimate mixing of and possible specific interactions between PC and PMMA chains in the coalesced blends. An attempt to achieve an intimate blend between nylon 6 and nylon 66 by forming and dissociating their common α-CD-IC was also made. Experimental results demonstrate that α-cyclodextrin can only host single nylon polymer chains in the IC channels. Spectroscopic results illustrate that there is intimate mixing existing in the IC coalesced blend, but not in their solution cast physical blend.
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Keywords
polymer, polymer blend, engineering polymers, biomaterials, inclusion complexes
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Degree
PhD
Discipline
Fiber and Polymer Science
