Guest polymer

To put the current research in LDH/polymer nanocomposites into context, we will first give a brief review of 2D-hybrid materials composed of a guest polymer and an inorganic host structure. 

In materials science, considerable attention has been devoted to how to prepare and shape new multifimctional materials. For the past two decades, 2D-hybrid materials composed of a guest polymer and an inorganic host structure have been extensively studied [1-10]. The lamellar host structure supplies a constrained environment in which the polymer is forced to locate and both parts may also act synergistically. 

Note The discontinuous phase domain is sometimes referred to as the guest polymer. 

Photochemical Phase Transitions in Guest/Polymer LC Systems... 

In another study, it was successfully reported an intimate ternary blend system of poly(carbonate) (PC)/poly(methyl methacrylate ) (PMMA)/poly (vinyl acetate) (PVAc) obtained by the simultaneous coalescence of the three guest polymers from their common y-cyclodextrin (y-CD) inclusion complex (IC). The thermal transitions and the homogeneity of the coalesced ternary blend were studied by differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA) [50]... 

To get a better insight into the dynamics of prepared ICs, more advanced NMR experiments were carried out [19]. Distinctive cross-polarization parameters were observed for guest polymer and host a-cyclodextrin in the inclusion complex. For a-CD, as expected from the relatively rigid molecule, the intensity quickly rises to a maximum, and then quickly decays. The behaviour is quite different for the PCL-PEO-PCL block copolymer, which has a slow rise in intensity followed by a slower decay. Maximum intensity was observed at 1 ms and 0.5 ms CP-time for PCL-PEO-PCL and a-CD. To evaluate the domain size... 

Fig. 15 Schematic drawing of inclusion of side chain guest polymers by CDs...

The IC of RAMEB and an adamantane modified polyacrylamide is thermosensitive heating of the aqueous solution of the IC of this guest polymer leads to a very steep increase of both viscosity and turbidity at a certain temperature, which is due to temperature induced decomplexation, followed by an aggregation of the polymer [196],... 

The interaction of CD dimers or CD polymers with side chain guest polymers leads to the reversible formation of three-dimensional supramolecular networks, as shown in Fig. 17. 

A remarkably different system comprised of a P-CD polymer and a guest polymer was recently described by Gref et al. [209], They mixed aqueous solutions of neutral P-CD epichlorohydrin polymer and a neutral lauryl ester of dextran, both of high molecular weights, and received no macroscopic gels but well-defined and... 

Fig. 18 Viscosities of mixtures of a 3-CD polymer (P-cyclodextrinyl-PIBMA) and a guest polymer (tert-butyl anilide of PIBMA) as functions of the molar fraction of guest groups in water for different shear rates D (s-1) of 66 (filled diamonds), 131 (filled squares), 196 (filled circles), 393 (open triangles), and 590 (open circles) at constant total polymer concentration of 2 wt% [202]...

Fig. 19 Cyclodextrin vesicles stabilized by complexation of the guest polymer, tert-butylanilid-PIBMA [210]...

Fig. 20 Schematic representation of different binding modes for guest polymers with planar CD arrays [213]...

It was found meanwhile that nearly every slim unbranched polymer chain, such as poly(trimethylene oxide) [224], poly(l,3-dioxolane) [225], poly(tetramethylene oxide) [226], polyethylene imine) [227], poly(3-hydroxy propionate), poly (4-hydroxybutyrate) and poly(6-hydroxyhexanoate) [228,229], poly(butylene succinate) [229], polyadipates [230], nylon-6 [231], and even oligomers of polyethylene [232], form a-CD ICs with channel structures. In all of these cases, inclusion is a heterogeneous process, since the guest polymer and its CD complex are almost insoluble in water. Therefore, extensive sonication had to be applied to accelerate the diffusion process. The polymer was also dissolved in an organic solvent, e.g., nylon-6 in formic acid, and this solution was added to the solution of a-CD [231], Alternatively, a monomer, such as 11-aminoundecanoic acid, was included in a-CD and polymerized to nylon-11 by solid state polycondensation within the channels of the IC. Thus, the IC of nylon-11 was formed under conservation of the crystal packing [233-235],... 

CD-ICs formed with polymer guests are crystalline solids (see Fig. If), which may be formed by mixing host CD solutions (usually aqueous) with guest polymer solutions (usually nonaqueous and organic) with the aid of heating, stirring, and... 

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. X-ray diffraction, DSC, TGA, and FUR and NMR spectroscopies are typically used to characterize the coalesced polymer samples. 

PCL, PLLA, or both were included. The a-CD-IC resulting from the suspension of PLLA-a-CD-IC in the PCL solution was found to contain only PCL guest chains, while the a-CD-IC resulting from the suspension of PCL-a-CD-IC in the PLLA solution contained only a very small amount of PLLA guest chains. The above results were interpreted to signify the importance of both guest polymer hydrophobicity and guest/host steric compatibility in the formation of polymer-CD-ICs. 

Formation of polymer-CD-ICs with amounts of host CDs insufficient to completely thread and confine the guest polymers, results in polymer-CD-IC crystals with portions of the guest polymer chains emerging from the host CD crystalline surfaces [102], When a nonstoichiometric (n-s) polymer-CD-IC, with only partially included chains, is added in small quantities to a bulk sample of the same polymer, which can crystallize and has a Tm below the decomposition temperature of CD-ICs... 

By combination of a solution containing two chemically distinct dissolved polymers with a CD solution, it is possible to form a common CD-IC containing both guest polymers. Assuming that each of the guest polymers is randomly included or mixed in the CD channels of their common CD-IC (see Figs. If, 2), we may anticipate that upon coalescence an intimate blend would result. The intimate blending of normally incompatible polymers, both binary and ternary blends, by coalescence from their common CD-ICs has in fact been demonstrated [40],... 

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. 

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