Poly , size effects

Fignre 1. Ring size effect on the potential of the Ni" /Ni" redox change of n-dentate poly-aza macrocycles. Points N4, N5, and Ne refer to 1 1 complexes with tetra-aza (systems 4, 5, 7, 8 ), penta-aza (systems 9-11 ) and hexa-aza (system 12 ) macrocycles respectively. Points 2 x N3 refer to 1 2 metal complexes with tri-aza macrocycles (systems 1-3 A). The open square refers to the isocyclam system, 6. E1/2 values measured in acetonitrile (0.1 M Et4NBp4) at 25 °C. 

Kinoshita has also shown that ORR data for supported catalysts in hot, concentrated H3PO4 (180 °C, 97-98% acid) reported in three different studies were also fit by this model. Since the physical basis for the crystallite size effect in sulfuric acid is anion adsorption, it would be a considerable reach to suggest that the same physical basis applies to this size effect, i.e., structure-sensitive anion adsorption. There are, nonetheless, indications that this is the case. Anion adsorption in dilute phosphoric [43] has a very similar structure sensitivity as sulfate adsorption, i.e., strongest adsorption on the (111) face, and on poly-Pt anion adsorption and/or neutral molecule adsorption in dilute phosphoric has a strongly inhibiting effect on the kinetics of the ORR [43]. Sattler and Ross [16] report a similar crystallite size dependence of the ORR on supported Pt in dilute phosphoric acid at ambient temperature as that found in hot, concentrated acid with the same catalysts. But it is unclear whether similar adsorption chemistry would exist in the extreme conditions of hot, concentrated phosphoric acid. 

Two reports have been published on the sonochemical preparation of nanosized ceria, Ce02 [133, 134]. Zhu and coworkers [133] synthesized nanocrystalline ceria (Ce02) particles via sonochemical and microwave assisted heating routes from aqueous solutions containing (NH4)2Ce(N03)6, hexamethylenetetramine and poly (ethylene glycol) (PEG Mw = 19,000). Analysis of the results showed that the products had a uniform shape, narrow size distribution, and displayed conspicuous quantum size effects. 

Table n. Size Effects on Diffusion in Poly(Methyl Methacrylate)... 

D. Freilich and G.B. Tanny, Hydrodynamic and microporous support pore size effects on the properties and structure of dynamically formed hydrous Zr(IV)-polyacrylate membranes, Desalination, 1978, 27, 233-251 A.J. van Reenen and R.D. Sanderson, Dynamically formed hydrous zirconium(IV) oxide-polyelectrolyte membranes, VI. Effect of copolymer composition on the stability of poly(acrylic acid - covinyl acetate) and poly(acrylic acid - covinyl alcohol) membranes, Desalination, 1989, 72, 329-338. 

Fig. 6 (a) NMR spectra of Poly(methyl methacrylate) (PMMA) obtained from the nanochannels of [Cu2(L)2(ted)] and the bulk condition in nitrobenzene- / at 110°C. (b) Plot of nanochannel size effect on tacticity of PMMA... 

Pace. M.D. Snow. A.W. Nitroxide spin-probe label of hydrogen-bonding and probe size effects in a linear epoxy polymer. Macromolecules 1995. 28 (15), 5300-5305. Starodoubtsev. S.G. Ryabova. A.A. Dembo, A.T. Dembo. K.A. Aliev, I.I. Wasserman, A.M. Khokhlov, A.R. Composite gels of poly(acrylamide) with incorporated bentonite. Interaction with cationic surfactants. ESR and SAXS study. Macromolecules 2002. 35 (16). 6362-6369. 

The following three points were ascertained 1) poly-merizabilities of the monomers 2) motion of polymer chains around the ends of the propagating radicals and 3) microstructures of the resultant polymers. These space-size effects are summarized in Table 3. 

The band-edge photoluminescence (PL) of K-CaSe has been shown to respond to the adsorption of a variety of analytes to the semiconductor s surface. This conceivably can be used for sensor development. However, one major problem is the issue of selectivity. Although Lewis bases and acids can be readily distinguished due to their differential effect on the electronic properties of the semiconductor, analyte-specific analysis is difficult to achieve. Ellis and co-workers [64] have examined the effect of imprinted polymer coating on the surface on the response of the semiconductor. Without the coating, the bare surface of CdSe responds to the adsorption of ammonia, mono-, di-, and trimethylamine with similar PL enhancement. However, upon coating the surface with ammonia imprinted poly(arylic acid) (PAA), CdSe only responded to the presence of ammonia, but not trimethylamine. On the other hand, CdSe coated with trimethylamine-imprinted polymer does not provide this selectivity, indicating the selectivity was mostly due to the size effect. 

Clarson, S. J. Mark, J. E. Semiyen, J. A., Studies of Cyclic and Linear Poly(dimethylsiloxanes) Effect of Ring Size on the Topological Trapping of Cyclic Polymers into Model Network Structures. Polym. Comm. 1986, 27, 243-245. 

Levy, H.B., Lvovsky, E., Riley, F.L., and Stephen, E., 1981, Interferon induction in primates by stabilized poly I poly C (poly ICLC) effect of size of polynucleotides. Infect Immun, in press. 

Clarson, S.J.,Mark, J.E., and Semiyen, J.A. (1986) Studies of cyclic and linear poly(dimethylsiloxanes) Effect of ring size on the trapping of cyclic polymers into network structures. Polymer Communications, 27,244-245. 

Polymer crystals are frequently small and imperfect, so that the diffraction spots are fuzzy, or they are arcs from an oriented poly-crystalline texture (see Fig. 3.1C). The degree of perfection of crystals of known structure can be determined from measurement of diffraction line widths and intensities. The analysis used for x-ray diffraction [21, 35, 36] can be transferred directly to electron diffraction. One can distinguish between crystal size effects and the effects of disorder within the crystals, but often a simple estimate of the mean crystal size, 0.9A/(angular breadth), is used. All electron diffraction measurements on polymers may be impacted by radiation damage (see Section 3.4). 

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