Spin labeling poly

Fig. 12.1.1 Dependence of order parameter, S. of the secondary polymer, spin-labeled poly (methyl methacrylate) (PMMA) and polystyrene (PST), bound to poly(maleic anhydride—styrene )-grafted silica on hexane content in ethyl acetate-hexane cosolvent. Numbers in parentheses are number average molecular weight of the secondary polymer. (From Ref. 48.)...

Here, the additional term involves the real permittivity (cj) and volume fraction ( j) of the interphase. Although this provides a qualitative structural interpretation of the data, it is not without its problems, as illustrated by the finite element simulation work of Maity et al. (2010), where it is necessary to assume an unrealistically large interphase thickness of about 200 nm in order quantitatively to reproduce the experimental data. Studies of nitroxide spin-labelled poly(methyl acrylate) containing a synthetic fluoromica suggested a rigid interface region that is just 5-15 nm in thickness (Miwa et al. 2008). 

Pilar J, Labsky J (1991) EPR study of chain rotational-d3Tiamics in dilute aqueous-solutions of spin-labeled poly(methacrylic acid) at different degrees of neutralization. Macnnnolecules 24(14) 4188 194. doi 10.1021/ma00014a036... 

Miscibility in s-IPNs was also examined for systems consisting of STMAA and the spin-labeled poly(e-caprolactone) (PCL) [79]. The results of this study led to the conclusion that, in the case of polymers interacting via hydrogen-bonding, the intracomponent crosslinking is not in favor of miscibility. The microphase... 

Exfoliated nanocomposites are usually more desirable for industry, because the strong interactions between the polymer and the clay layers can lead to controllable and often optimized polymer properties. The spin-labeled poly(methyl acrylate) (PMA) containing trimethylammonium chloride (TMC) at low concentration ( lmol.%) is shown in Chart 1 ion exchange between the TMC moiety as an anchoring group and the clay platelet surface allowed the preparation of exfoliated nanocomposites even in the absence of surfactants. " ... 

Sphingomyehn, IR spectrophotometry, 683-4 Spin delocahzation, polar effects in decomposition, 903 Spin labels, free radicals, 665 Spin-lattice relaxation oxidized functional groups, 695 poly (methylstyrene peroxide), 709 Spin trapping artemisinin ESR, 1291 free radicals, 665... 

Poly(vinyl acetate), PVAc, of molecular weights (M ) 6.1x1 01, 1.9xl05, and 6.0xl05, was randomly labeled by ester exchange with 2,2,5,5-tetramethyl-3-pyrrolin-l-oxyl-3-carboxylic acid to give a spin labeled polymer containing typically 1-10 nitroxides per polymer molecule. Polystyrene was prepared by emulsion... 

The first experiments concerning the use of nitroxide spin labels, a study of conformational changes in poly-L-lysine and bovine serum albumin [126] were carried out by Stone, Buckman, Nordio and McConnell in 1965, and it is largely due to the impetus provided by this group that such a large literature about them now exists. This has been reviewed in a number of places [127-130] a few experiments representative of the general areas in which spin labels have found application are given here. 

BeKsto S, Bartucci R, Montesano G, Marsh D, SporteUi L (2000) Molecular and mesoscopic properties of hydrophilic polymer-grafted phospholipids mixed with phosphatidylcholine in aqueous dispersion interaction of dipalmi-toyl N-poly(ethylene glycol) phosphatidyleth-anolaminewithdipalmitoylphosphatidylcholine studied by spectrophotometry and spin-label electron spin. Biophys J 78 1420-1430... 

The group of Goldfarb and coworkers have in recent years explored how (spin-labeled) thermoresponsive triblock copolymers of the Pluronic -type (PEO-PPO-PEO, poly(ethylene oxide)-poly(propyleneoxide)-poly(ethyleneoxide)) can be used to build templates, e.g., for the formation of mesoporous frameworks [93, 94]. These structures bear great potential as carrier materials for catalysts and hence could aid societal needs in energy and sustainability. 

Similarly, Wasserman and coworkers have studied a wide selection of polymeric materials in aqueous solution that are associative of some kind, i.e., that form some sort of self-assembly through non-covalent interactions [96]. Their study mainly deals with hydrogels of hydrophobically modified polymers, aqueous solutions of polymeric micelles created by block copolymers, and hydrogels based on poly (acrylic acid) and macrodiisocyanates. The spin probes of choice were hydrophobic, such as 5- and 16-DSA (see Eig. 2) or even spin labeled polymers. It was, e.g., possible to screen for the effect of chemical stmcture on the gel formation by recording and understanding the local mobility of the hydrophobic, long chain spin probes as a function of temperature. 

Maliakal et aV have studied the proton relaxivity produced by dinitroxide spin labels attached to poly(propylene imine) dendrimers as potential MRI contrast agents. They find that proton relaxivity, which is substantially higher than for mononitroxide spin labels, is not seriously affected by electron selfexchange. 

Fig. 4 Dynamical contrast between two surfactant sites in a colloidal polymer dispersion [poly(butylmethacrylate)]. Surfactant spin labels anchored with their tail end in the polymer particle exhibit a rigid limit line shape (A), while surfactants not anchored are more mobile (B). The total spectrum C of the dispersion is a superposition, with the fraction of the mobile component decreasing with decreasing water content (data taken from S. Cramer. Ph.D. thesis. University of Mainz, 2000). View this art in color at www.dekker.com.)...

The following tables give the spin-Hamilton parameters g and of free radicals as determined mainly by spectroscopic measurements on liquid or solid samples. Gaseous phase di- and tri-atomic radicals are included in the tables on inorganic radicals. There is a special table on organic poly radicals and a collection of information on spin-labelled biomolecules. 

Miwa Y, Drews AR, Schlick S (2008) Unique structure and dynamics of poly(ethylene oxide) in layered silicate nanocomposites accelerated segmental mobility revealed by simulating ESR spectra of spin-labels, XRD, FTIR, and DSC. Macromolecules 41 4701-4708 Mohan SD, Mitchell GR, Davis FJ (2011) Chain extension in electrospun polystyrene fibres a SANS study. Soft Matter 7 4397-4404... 

ALE Aleksandrova, T. A., Vasserman, A. M., and Tager, A. A., Study of the stmctuie and phase equihbrium of the poly(viityl acetate)-methanol system by the spin labeling technique (Russ ), Vysokomol. Soedin., Ser. A, 19,137,1977. 

AU of these methods produce randomly labelled polymers with the labels on in-chain segments. End-labelled i>olymers are generally prepared by anionic polymerisations. The living chain end is terminated with a suitably functionalised spin label, usually an acid chloride [11]. A different method was used to prepare end labelled poly(n-butyl isocyanate) [12]. Here the spin label 2,2,5,5- tet-ramethyl-l-pyrrolidinyloxy-3-carboxamide was used as an initiator in competition with cyanide ion (Scheme 5). This produced a spin concentration of one label per three polymer chains. 

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