Deuterated PB

Fig. 4.21 Scaling representation of the NSE data on fully deuterated PB near the first valley of S(Q) (Q=1.88 A ). The scale r (T) is taken from viscosity measurements. The solid line represents the master function obtained for the spectra at temperatures >220 K (KWW with =037). The dashed lines are the result of fitting stretched exponentials to the different low-T spectra keeping 15=037 fixed filled diamond 280 K, filled circle 260 K, empty triangle 250 K, empty diamond 240 K, cross 230 K, empty square 205 K, filled square 190 K, empty circle 180 K) (Reprinted with permission from [188]. Copyright 1992 The American Physical Society)...

Figure 15.8 2H NMR spectra obtained in a randomly crosslinked, deuterated PB network. Precursor chain molecular weight 115700 g.mol"1, 1.2% crosslink agent, the average molecular weight between junctions is 27400 g.mol 1 (as determined by swelling experiments) or 11600 g.mol"1 (elastic measurements). The smooth curves are fits with a most probable distribution of chain lengths with number average molecular weight Mc = 11600 and with non-Gaussian chain statistics...

Deuterated PB networks filled with carbon black have been investigated recently [74]. The 2H NMR lineshape is different from that in unfilled elastomers an asymmetric doublet is observed as the sample is uniaxially stretched (A,=1.8)). This asymmetry is related to the presence of carbon black fillers, which induce magnetic inhomogeneities. 

LDPE, HOPE, deuterated and hydrogenated PB blends LDPE/HDPE at 143°C were found immiscible Xj2 = +0.00056 dHDPE with deuterated PB had Xj2 = +0.0004 blends of hydrogenated PB with deuterated PB gave x = +0.00053 at 130°C. Alamo et al., 1997... 

PB which are indistinguishable for neutrons if a fully deuterated PS is mixed with a partially deuterated PB consisting statistically of 4.4% protonated and 95.6% deuterated monomers. 

A first observation can be established, namely, that blends with deuter-ated PB(1,2) show a much stronger tendency towards incompatibihty than blends with deuterated PB(1,4). This observation is supported by the finding that a corresponding mixture of dPB(l,2) and PB(1,4) was not miscible below... 

The FH parameters Th and Fa for the PB copolymer blends are depicted in Fig. 10 versus the vinyl content of the protonated PB component. The solid and open triangles and spheres represent blends with fixed vinyl content of X = 0.07, 0.16, and 0.91 of the deuterated PB component, respectively. The FH parameters were corrected for chain-end effects which are rather strong and are not shown here (see Fig. 6 in [64]). 

Consistent notation is adopted throughout this book. Diblock copolymers are written poly(monomer A) poly (monomer B) or PA-PB, where examples of PA and PB are illustrated in Fig. 1.2. Similarly, triblock copolymers are written poly(monomer A)-poly(monomer B)-poly(monomer C) or PA-PB PC. Deuterated blocks are denoted dpoly(monomer A) or dPA. The molar mass of a copolymer is denoted by M, or Af corresponding to the weight- or number-average respectively, and the composition is specified by the volume fraction of one component,/. In solution, the volume fraction of a copolymer is denoted [Pg.3]

This method was further developed by Iatrou et al. [22]. All possible combinations of A2B polymers with A and B being PS, PI or PB were prepared. A more sophisticated and complicated high vacuum technique was used to ensure the formation of well defined products. High degrees of molecular, structural and compositional homogeneity were achieved by this technique, as was evidenced by the combination of all the molecular and spectroscopic characterization data. In a more recent study stars having deuterated PS arms, (PI)2(d-PS) were also prepared [23]. 

Deuterated poly( 1,4-butadiene) (PB) networks have also been investigated [18-22], The linear precursor chains Mn from 75000 to 116000 g.mol 1) are homogeneously, selectively deuterated in the 1,4 positions, and randomly crosslinked with different types or amounts of crosslinkers. Star precursor chains deuterated at the center have also been used. 

The doublet appears in various other polymer matrices, which shows that the uniaxial ordering of chain segments is perhaps a quite general phenomenon. For instance, PB networks with chains deuterated in 1,4 positions (Figure 15.8) have been studied [18-21]. Their behaviour is essentially the same, even though the linewidth is much broader... 

Figure 15.14 2H NMR spectra of deuterated benzene molecules diffusing in a uniaxially stretched PB network for various elongation ratios. The solvent volume fraction is 9%...

Silica hydrolysis-condensation of alkoxysilane-terminated chains of various polymers (PB, poly(propylene)-glycol, poly (ethylene)-glycol) leads to the formation of silica nodules. Hybrid (organic-inorganic) nanocomposite rubbery materials are obtained in this way. These materials have been swollen by various deuterated solvents, in order to probe the order induced in the polymer matrix under stress [80]. 

New crosslinked elastomers may be formed by self-aggregation of substituted functional units able to form directed hydrogen-bonds. 1,4-PB has been randomly substituted with about 4 mol% urazole units [94], The urazole units form hydrogen-bonded supramolecular, plate-like aggregates which act as effective crosslinking zones, thus creating a thermoplastic elastomer [95, 96, 97]. The system is deuterated either in the PB backbone or in the urazole units, which allows to investigate the molecular dynamics in... 

In the above, we have seen that a certain interpolymer interaction is required for different polymers to be miscible. Here, we will see that high resolution NMR enables us to locate interacting regions in component polymers. One of the most useful methods is the nuclear Overhauser effect (NOE) between H— H and H—NOE can be observed between spins whose distances are less than about 0.5 nm. The one- (ID) and two-dimensional (2D) NOE experiments have been used to reveal the spatial structure of biomolecules in solutions. Of course, these can be applied to locate interacting regions in a blend in solution and in solids [3]. For example, Crowther et al. [22] and Mirau et al. [23] applied NOE experiments to polystyrene/poly(vinyl methyl ether) (PS/PVME) in a toluene solution, and show that the interpolymer NOE signals between the aromatic protons of PS and the methoxy protons of PVME can be observed at polymer concentrations higher than 25 wt%. In the solid state, Heffner and Mirau [24] measured 2D H— H NOESY (NOESY nuclear Overhauser effect spectroscopy) spectra of 1,2-polybutadi-ene and polyisoprene (1,2-PB/PI) and observed NOE cross-peaks between these component polymers. White and Mirau observed interpolymer NOE interactions between the H spins of PVME and the spins of deuterated... 

Fig. 9. A comparison of the late stage scaling function of near critical polybutadiene/polyisoprene (PB/PI) mixtures at T = 55 °C with that of deuterated poly-butadiene/polybutadiene mixture [36], DPB/PB and of an iso-butyric acid/water mixture [181] I/W. Note the asymptotic exponents F(x < 1) ocx and F(x > 1) ocx-4. From Takenaka and Hash-imoto [180]...

The angular distributions of 84Mev neutrons scattered from Al, Cu, and Pb were measured by Bratenahl, Fernbach, Hildebrand, Leith and Moyer. The distributions were studied from 2 5 to about 25°. They used the broad spectrum of neutrons from the stripping of IQOMev deuter-ons on a Be target (see Sect. 35). 

Other examples of such detailed analysis of the structure with the aid of contrast variation can be found for partially deuterated polystyrene-polyisoprene (PS-Pl) diblock copolymer micelles in decane [86, 95] Pluronic (PEO-PPO-PEO) micelles in water [96, 97] PB-PEO micelles in water [85] or PEP-PEO micelles in water [44] or in water/ DMF mixture [98]. 

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