Spin labeling polystyrene

For proteins adsorbing to spin-labeled polystyrene (a hydrophobic surface), the relaxation times do increase significantly relative to the controls, but only for one protein, mfp-3s, which has a relaxation time of t 750 ps. ... 

Synthesis of spin-labelled polystyrene has been carried out by the reaction of the polymer containing chlormethyl groups with radical IV (R=OH) [88, 89] ... 

The spin-labelled polystyrene contains one AR per 1000 monomer units. If t-butylmagnesium chloride is used instead of phenylmagnesium bromide, a polymer with -butylaminoxyl groups can be obtained [108] ... 

Synthesis via scheme (2.53) has several drawbacks. The mercurated polystyrene is inclined to cross-link, and the polymer containing nitroso groups is unstable. A more suitable method of synthesis of spin-labelled polystyrene is given below [109] ... 

The SRLS mechanism has been invoked to explain the segmental rotational dynamics of spin-labeled polystyrene in toluene solution. This study provides an example of a system in which the dynamic cage is defined by constrained diffusion of the spin label attached to a polymer. The SRLS model is appropriate to analyze these spectra, since the local ordering environment is coupled to the global tumbling modes of the polymer. Moreover, the high (250-GHz) frequency ESR spectra of this... 

Pilar J, Labsky J, Marek A, Budil DE, Earle KA, Freed JH (2000) Segmental rotational diffusion of spin-labeled polystyrene in dilute toluene solution by 9 and 250 GHz ESR. Macromolecules 33(12) 4438-4444. doi 10.1021/ma0002242... 

Spin-labelled polystyrenes were prepared by reacting the corresponding lithiated polymers with 2-methyl-2-nitrosopropane, either in para or in meta positions. In the latter case the lithiation results from the modification of polystyrene by BuLi complexed with N,N,N N -tetramethylethylenediamine the metallated polymer is reacted with 2-methyl-2-nitrosopropane (MNP), " as in reaction (18). 

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.)...

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... 

Functional groups attached to solvent-swollen polymer chains exhibit free rotational motion as indicated by electron spin resonance rotational correlation times 132-134) These studies using nitroxide spin labels covalently bound to polystyrene matrices indicated that the mobility of the substituent is a function of the cross-link density and degree of swelling. The rotational correlation time of nitroxide within 2% cross-linked beads was about 100 times shorter in dichloromethane or benzene than in ethanol, and 2-3 times longer than nitroxide bound to non-cross-linked polystyrene. The latter observation shows that the heterogeneous reaction involving 2% cross-linked polystyrene is 2-3 times slower than the same reaction in solution. 

Glass-Rubber Transition Detected by the Spin Label Method for Polystyrene (PS) Molecular Weight Dependence... 

Figure 9.3 Mip-mediated surface water displacement from polystyrene (PS). PS beads were labeled with tethered nitroxide spin labels. Upon excitation during electron spin resonance, polarization was transferred to the surrounding water molecules within 15 A. Polarized water molecules present relaxation correlation times (t in Table inset) that reflect the local environment. Longer times denote more confinement and lower diffusivily. Only one adhesive protein, mfp-3s, is capable of increasing the surface water relaxation time, presumably by adsorbing directly onto the PS surface. Mfp-3s is notable for having a high hydrophobicity (inset table), as indicated by the negative hydropathy value, which denotes a normalized per average free energy of transfer from water to the non-polar solvent Data from ref. 22.

The important reaction of nitroso componnds resnlting in spin-labelled polymers is radical captnre. Polystyrene containing -bntyl aminoxyl was obtained by radical polymerisation in the presence of TNB and t-bntylperoxyoxalate [111] ... 

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... 

Kumler and Boyer (1976) used esr spectroscopy to study the glass transition of several spin-labeled polymers and copolymers, and spin-labeled polymeric matrices have been used to study solvent effects on chain flexibility in polystyrenes usually used in peptide solid-phase syntheses (see Section IV). 

Regen (1974) described a method of assessing the mobility of the resin sites by covalent attachment of a spin-label probe [2,2,6,6-tetramethyl-4-piperidinyl-l-oxy group (Tempo) (Fig. 3-1. R = (P)—)] to the chlo-romethylated co(polystyrene-DVB). Rotational correlation times (t) were calculated from observed room-temperature electron paramagnetic resonance (epr) spectra. The degree of swelling, q, (swelled volume/ dry volume) was determined from the measured density of the dry resin and the weight of the imbibed solvent. The data indicate that those... 

The simplest method of spin labelling is to utilise a functional group on the polymer to attach the label, usually via a condensation reaction (Scheme 1). Labels can also be introduced by less rect methods. For example, the Keana synthesis [6] (Scheme 2) has been used to label polyethylene that had been copolymerised with a small amount of carbon monoxide [7]. Polystyrene has been labelled by reacting the lightly lithiated polymer with either 2-methyl-2-nitrosopropane or nitrosobenzene (Scheme 3) [8]. 

Another system examined by Miwa et al. is that of binary blends of the AB-type copolymer, polystyrene-fclock-poly(methyl acrylate) (PS-PMA), with homopolymers miscible only with the A (PS) block, including PCHA of different molecular weights (Mn = 1000 and M = 17 300, comparable to that of the PS block in the copolymer) and the low-molecular-weight PS homopolymer (PS-1, M = 900) [65]. The copolymer was spin-labeled (using Tempamine) at chemical junction points... 

In the UK, Booker et al. (1967) used a spinning disk to make monodisperse polystyrene particles. Polystyrene was dissolved in xylene, at a concentration of 0.2%, and chromium acetyl acetonate, labelled with 51Cr, was added. The spinning disk was operated at 3 x 104 rpm to produce 40-/,polystyrene spheres. Few etal. (1970) adapted this method to produce particles of polystyrene labelled with "mTc. This isotope has only very slight beta emission, so the dose to the lung is low, and though the radioactive half-life is only 6 h, this is adequate for estimation of the ratio P/(TB + P) and for analysis of the kinetics of the mucociliary clearance. 

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