Latexes deuterated

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.

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. 

Monomer Sequence Distribution in the Copolymer by C NMR. The latex samples which were precipitated in the mixed solvent (ispropanol/hexane = 45/55 and dried in a vacuum oven at 45-50°C, were used for the C NMR study. The polymer samples were dissolved (5-7% weight volume) in deuterated pyridine (PYR d%) with tetramethylsilane (TMS) as a zero external reference. The NMR measurement and the theoretical calculation were carried out in CNRS, Laboratoire des Matriaux Organiques, in Lyon, France using C NMR 30 MH (Bruker). 

Figure 6.16 shows a plot of p(z) against z for PVA (M = 37 000 Da) adsorbed onto deuterated PS latex in D2O/H2O. The results shows a monotonic decay of p(z) with distance z from the surface, and several regions may be distinguished. Close to the surface (0 < z < 3 nm), the decay in p(z) was rapid and, assuming a thickness of... 

Figure 6.16 Plot of p z) against z for PVA (M = 37000) adsorbed onto deuterated PS latex in DjO/HjO.

In general, the above discussion has shown that the interface between two immiscible polymers is certainly an interesting point which needs further investigation. It is evident that SAXS is a highly useful tool for this purpose because this method can directly be applied to the latex without any prior staining or choice of special monomers, as e.g., deuterated monomers. 

Yang et al. [27], using small-angle neutron scattering (SANS), reported the formation of supermolecular structures in polystyrene latex particles prepared by the seeded emulsion polymerization of styrene onto deuterated polystyrene particles. The recorded scattering intensities, which were much higher than those expected on the basis of the Debye random coil model, indicate the presence... 

Figure 23.7 shows SANS data from a 4.6 vol% latexes with a fully deuterated PMMA-D shell, (thickness 30 A) polymerized on a PMMA-H core (radius, a = 498 A), after desmearing corrections for the finite instrumental resolution [37,42]. The absolute intensity at zero scattering angle is given by Eq. (23.15) with P(0) = 1 and Vp equal to the volume of the D-labeled polymer in the shell with SLD", p p = 6.97 x 10 cm-2. qiie SLD of the solvent is close to that of the PMMA-H core (p j = 1.06 x 10 cm2) and thus... 

Mixtures of deuterated and protonated polystyrene latexes have also been studied by SANS (78,79). The main advantage is the relatively large surface area presented for interdiffusion, since the latex particles are relatively small. Figure 5.12 (79) illustrates the time dependence of the interdiffusion process. The data follow the non-Fickian relationship up to a diffusion distance of about 0.4i g. For diffusion from one side only. Wool (80) derived the break point as 0.8i g. However, equal diffusion from both sides, the present case, yields half that value as intuitively expected, noting that the diffusion distance is measured from the original interface plane rather than the true diffusion distance. 

Investigation of adsorption of poly(ethylene oxide) on deutered polystyrene particles from D2O [16,17,41] and random eopolymer poly(vinyl alcohol-co-acetate) on polystyrene latex by SANS showed [17] that the density profiles of adsorbed polymer are well reproduced by mean field theories and Monte Carlo simulation (Fig. 10). 

FIG. 10 Neutron-scattering intensity for poly(ethylene oxide) adsorbed on deuterated polystyrene latex in D2O. Molecular weight 28 x 10, E =1.21 mg/m, and latex diameter was 240run [17]. 

To measure the rate and extent of polymer diffusion across a boundary, one needs a source of contrast. Contrast is achieved by labeling the polymer, for example, employing a small amount of deuterated latex in conjunction with small angle neutron scattering experiments, 10 or with fluorescent labels in conjunction with direct non-radiative energy transfer [DET] measurements.il In our laboratory, we prefer the DET methodology because of our ready access to beam time. Thus the latex we prepare are... 

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