Fractional deuteration

This method applies for whatever polymer concentration. In practice, it is preferable to use high concentrations in order to increase the signal-to-noise ratio and therefore minimize counting time. However, it can also be applied to semidilute or even dilute solutions where Zimm plots are useful. It also applies not only to linear polymers but also to any form of chain architecture and to deuterated/protonated mixtures in non-solvent matrices such as polymer blends or polymer networks provided that changing the deuterated fraction does not change the homogeneous nature of the mixture (i.e., no change to the chain conformations and interactions). 

The quantity measured with the help of neutron scattering, by all the quoted authors, is the structure function HD q) associated with the deuterated fraction... 

Bradbury et al. (1967) have studied partial nucleoproteins produced by removal of histone fractions from nucleohistone. Figure 12.6 shows a polarized infrared spectrum of one of the nucleoproteins oriented by shearing. The spectrum is that of a film deuterated by D2O vapor. The bands of the in-plane vibrations of cytosine and guanine moieties are highly polarized when the electric vector is placed perpendicular to the fiber axis. The 1452 cm absorption is that of the amide IF band (Miyazawa et al., 1956 Miyazawa, 1962) for the readily deuterated fraction of the partial nucleoprotein. As seen in Fig. 12.6, the 1452 cm band is polarized considerably in the direction parallel to the fiber axis, giving evidence that the extended polypeptide chain is situated so that its axis lies between the angle of the groove in the DNA double helix and the axis of the DNA helices (Bradbury et al., 1967). 

Publication In preparation. Professor G. Dijkstra and K. Versluls of Utrecht State University are acknowledge for analyzing the deuterated fractions by GLC-MS array. 

Two experiments have been performed which allow a comparison between S(q) and for same conditions and the same sample. The form factor is given by SANS and the orientation PjfO) by deuterium magnetic resonance Both are sensitive to deuterated species and can be used in melts for large deuterated fractions. A small chain of deuterated PDMS (M jj 10000, 20000) is dissolved in... 

Experiments involving relaxation of centrally deuterated polystyrene chains in a higher molecular weight matrix recently provided support for the minor chain reptation model.Using infrared dichroism studies of step-strained PS films, the protonated chain-ends were found to relax faster than the centrally deuterated fraction. This is consistent with the MC model shown in Fig. 1(a) where the chain-ends first lose memory of their initial orientation. 

Fig. XI-7. Volume fraction profile of 280,000-molecular-weight poly(ethylene oxide) adsorbed onto deuterated polystyrene latex at a surface density of 1.21 mg/m and suspended in D2O, from Ref. 70.

Let us first consider two identical polymers, one deuterated and the other not, in a melt or a glassy state. The two polymers (degree of polymerization d) differ from each other only by scadermg lengths and b. If the total number of molecules is N, x is the volume fraction of the deuterated species x = N- / N, with Aq -t = A). According to equation (B1.9.116), we obtain... 

Styrene is difficult to purify and keep pure. Usually contains added inhibitors (such as a trace of hydroquinone). Washed with aqueous NaOH to remove inhibitors (e.g. rert-butanol), then with water, dried for several hours with MgS04 and distd at 25° under reduced pressure in the presence of an inhibitor (such as 0.005% p-tert-butylcatechol). It can be stored at -78°. It can also be stored and kept anhydrous with Linde type 5A molecular sieves, CaH2, CaS04, BaO or sodium, being fractionally distd, and distd in a vacuum line just before use. Alternatively styrene (and its deuterated derivative) were passed through a neutral alumina column before use [Woon et al. J Am Chem Soc 108 7990 1986 Collman J Am Chem Soc 108 2588 1986]. 

We present here a simple experiment, conceived to test both the reptation model and the minor chain model, by Welp et al. [50] and Agrawal et al. [51-53]. Consider the HDH/DHD interface formed with two layers of polystyrene with chain architectures shown in Fig. 5. In one of the layers, the central 50% of the chain is deuterated. This constitutes a triblock copolymer of labeled and normal polystyrene, which is, denoted HDH. In the second layer, the labeling has been reversed so that the two end fractions of the chain are deuterated, denoted by DHD. At temperatures above the glass transition temperature of the polystyrene ( 100°C), the polymer chains begin to interdiffuse across the... 

Cooper and coworkers30 measured also the absorption spectrum of transient species produced in the radiolysis of pure liquid DMSO-d6 and found the same absorption of the first two bands, however, the intensity of the absorption is about 30% larger in the case of the deuterated compound for both of the absorption bands. The intensity of the absorption is given by Ge, but as the same change was found for both bands it seems most reasonable that the 30% difference arises from a change in G rather than in e. This is similar to water, where the fraction of ions which become free ions is substantially larger for the deuterated compound32. 

Fig. 8.7 ST curves (molar fraction yns as a function of temperature) for [Fe(2-pic)3] CI2 C2H5OH deuterated in different positions of the solvent (from [15])...

Zink et al. used a blend of polystyrene (hPS) and its deuterated counterpart (dPS), both of molecular weight 1.95 x 106 (abbreviated 1.95 M). The average volume fraction (4>dPS) of deuterated polystyrene was 30%. The polymers were dissolved in toluene and spin cast on thin silicon wafers (about 10 x 10 mm), the resulting film thickness being about 300 nm. The samples were annealed at 245°C for 8 days, and the measurement of the resulting depth profiles was conducted by NRA using a monoenergetic 700 keV 3He beam. The nuclear reaction employed can be written ... 

Fully-deuterated xetralin was used to study the mechanisms of coal liquefaction. Experiments were conducted with xetralin-di2, deuterium g s and bituminous coal at 400°C and at 15.2-20.7 MPa. The recovered solvent and solvent-fractionated coal products were analyzed for total deuterium content and for deuterium content in each structural position. 

The atom % 2H values of the solvent-fractionated products are also shown in Table I. In previous hydrogenation experiments conducted without the use of a donor solvent (1,18), deuterium incorporation increased from the most soluble oil fraction to the insoluble residue. In E10 and El9, contact of the coal with Tetralin resulted in a uniform incorporation of deuterium in almost all of the four product fractions. In El9, the BMI fraction s high value of 61 atom % 2H may be due to direct gas-phase exchange and deuteration. 

The isotopic composition of the two fractions was then determined on an AEI MS-10 mass spectrometer. From the analysis of the reaction products and the known flow rate of the reactants, the rates of exchange (Ee) and deuteration (Eh) could then be calculated. 

Plenty of other X and Mc scales are available, for these acid media and others. We have published an X scale for aqueous HBr and an Y0 scale for HC1,36 and an X scale for DCIO4,52 although different scales for deuterated acids are unnecessary the scales for the protonated acids can be used, along with the assumption of equal acidity at equal molarity or mole fraction for protonated and deuterated acids,53 which works very well. Marziano, Tomasin... 

The samples of the 96% deuterated latex were prepared by a standard surfactant-free procedure which is described fully elsewhere (13). The narrow distribution fractions of PEO were obtained from Polymer Labs (Shawbury) and were manufactured by the Toya Soda Co. The details of these samples are given in Table I. 

The results of a mass spectrometric investigation of the products, after correcting for the 13 C content and the M-l fractionation of the molecular ion, showed that the trans-2-butene was > 97% deuterated and that less than 1% of the c -2-butene was deuterated. This means that at least 97% of the elimination reaction to form the fraws-2-butene and > 99% of the elimination to form the cw-2-butene occurred by an awh -periplanar mechanism (Scheme 23). 

Although the first NMR spectra of deuterated proteins were published already in 1968, the deuteration was mainly employed for the purpose of simplifying one-dimensional proton spectra.53,54 Later in the 1980s, LeMaster and co-workers employed random fractional deuteration for the assignment of thioredoxin using homonuclear two-dimensional spectroscopy.55 However, it was realized that deuteration significantly improves the spectral quality of homonuclear multidimensional NMR experiments. 

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