Labeled polybutadiene

Moreover, the ratios Tj/Xj obtained at different temperatures are similar to the values obtained for labell polybutadiene in dilute solution in toluene (= 30). Thus, the surrounding chains seem to affect local dynamics only at the level of the friction coefficient. Intrachain connectivity remains the essential non isotropic constraint on local dynamics in bulk polymers and models for the isolated chain are applicable. This is consistent with the idea that topological interchain effects only act on a... 

Mw = 4.1.10 was used as a matrix for FAD experiments. An anthracene labeled polybutadiene with the same microstructure was synthetized by anionic polymerization as... 

A detailed study of the FAD of anthracene labeled polybutadiene in a matrix of Diene 45 NF has been performed in the temperature range 240K-353K ( 2 ). 

Figure 3. Comparison of the best fit obtained from the Hall-Helfand expression reconvoluted by the measured instrumental function (excitation pulse) (continuous line) with the experimental anisotropy (dots) of labeled polybutadiene at 335,7K. The excitation pulse is plotted as a dash-dot line (arbitrary scaled). The upper graph represents the weighted residuals.

It should be pointed out that a comparison of the FAD curves of labeled polybutadiene to the ones obtained for free 9,10 (dialkyl) anthracene probes in a Diene 45 NF matrix led to the conclusion ( ) that the local motions observed by the FAD experiments performed on labeled polybutadiene involve about 6 butadiene units. 

In polymers, due to the constraint resulting from the connectivity of the chain, the local motions are usually too complicated to be described by a single isotropic correlation time x, as discussed in chapter 4. Indeed, fluorescence anisotropy decay experiments, which directly yield the orientation autocorrelation function, have shown that the experimental data obtained on anthracene-labelled polybutadiene and polyisoprene in solution or in the melt cannot be represented by simple motional models. To account for the connectivity of the polymer backbone, specific autocorrelation functions, based on models in which conformational changes propagate along the chain according to a damped diffusional process, have been derived for local chain... 

Viovy JL, Monnerie L, Merola F (1985) Fluorescence anisotropy decay studies of local polymer dynamics in the melt. 1. Labeled polybutadiene. Macnnnolecules 18(6) 1130-1137. doi 10.1021/ma00148a014... 

ABSTRACT - The fluorescence anisotropy decay (FAD) technique is first described, then the different expressions ich have been proposed for the orientation autocorrelation function (OACF) of polymer chains are presented. Typical FAD curves of dilute and concentrated solutions of polystyrene labelled with an anthracene group in the middle of the chain are compared to the various OACF expressions and discussed. In the case of bulk polybutadiene, FAD results obtained either on anthracene labelled chains or on 9,10 dialkylanthracene probes free in the polymer matrix, show that the same type of OACF as for polymer solutions can account for the experimental data. Besides, the temperature dependence of the correlation time of the labelled polybutadiene appears to agree with the WLF equation derived from macroscopic viscoelastic measurements, proving that the segmental motions of about 20 bonds which lead to the FAD of labelled polybutadiene participate in the glass transition processes of this polymer. 

In the studies described above on FAD of labelled polybutadiene, the type of orientation autocorrelation function able to account for the experimental results has been defined. However, no information has been obtained about the size of the chain sequence involved in the motion observed by FAD of labelled polybutadiene. In order to obtain an estimate of this sequence length, FAD measurements have been performed (41) on various 9,10 dialkylanthracene probes (Fig. 18), denoted C, with n varying. 

Besides, it is interesting to examine how the H-H or GDL expressions, given in Table 2 and used for polymer chains in solution or in bulk, can fit the FAD curves of the various C probes. It appears that both functions yield a very good fit for and and in this latter probe the characteristic times and T are the same as in labelled polybutadiene. This gives an estimate oi the size of the sequence diose motion is reflected through the FAD of the anthracene label about 30 bonds. It is worth noting that for shorter tails the quality of the fit rapidly decreases because of a higher contribution of the overall motions compared to the internal (polymer-like) motions. Thus,... 

It has also been shown that the segmental motions which are responsible for the orientation decorrelation observed by FAD of labelled polybutadiene, involve about 30 bonds and these motions participate to the glass transition phenomenon. On the contrary, the overall motion of 9,10 dimethylanthracene probe in a polybutadiene matrix is associated with local chain motions diich are not involved in the glass transition processes of this pol3mier. 

Metal—Carbon Bonds in Cobalt-Catalyzed Polymerization. Concentrations of metal-carbon bonds were determined (using tritium labelled alcohol) with increase in conversions. Experiments were made in two solvents (petrol and benzene) with two cobalt salts (chloride and naphthenate) under conditions giving rise either to liquid mixed structure or to high trans polybutadiene. The data are summarized in Table XI. Table XII and Figure 11 shows optical properties of some cobalt salts and complexes. 

An urethane-based pressure-sensitive adhesive composed of a liquid hydroxytelechelic polybutadiene and a polyisocyanate does not require a solvent in coatings onto label sheets. This polymer together with the (polystyrene-co-butadiene) copolymer and a polyisocyanate was applied in steel coatings 239 240>. 

We recently performed FAD experiments on polybutadiene chains labelled with anthracene in the middle of the chain (Fig. 7), embedded in a matrix of homopolymers unlabelled chains. The concentration of labelled chains was about 1 %. 

Fig. 7. Polybutadiene labelled with anthracene in the middle of the chain (PBAPB)...

FAD allows to study rather precisely and unambiguously the OACF of polymer chains. Thanks to the unique statistical nature of the single photon method, and to the performances of the synchrotron source, it has proved very useful in the discussion of the nature of motions. For instance, it led to the first observation of the diffusion of orientational motions along the chains in polymer melts. Of course, the labeling nature of this kind of experiments implies two limitations. The first one, technical, is the necessity of labeling chains. Indeed, many different polymers can be labelled and several species have been or are studied in our laboratory (Polystyrene polybutadienes -20.37) polyisoprenes poly-... 

The termination reactions appear to be quantitative and specific for the reaction of saturated polymer molecules attached to aluminium and titanium [116], but applied to diene polymerizations the method is less satisfactory mainly because of the greater stability of allylic carbon-transition metal bonds. Polybutadiene has been labelled by terminating with tritiated methanol with the Cr(acac)3/AlEt3 catalyst [55], and similarly polyisoprene prepared with VCl3/AlEt3 [107]. Polybutadiene prepared with Til4/Al(i-Bu)3 has been labelled using C02 [115]. 

As an example, some results obtained by Viovy et al. on bulk polybutadiene are presented [76, 77]. 1 % of the chains were labelled by anthracene in their middle, as is shown in Fig. 41. The evolution of the anisotropy decay with temperature is given in Fig. 42. As expected, the decay rate increases as the temperature rises, indicating an increase of the chain mobility in the vicinity of the chromophore. 

Fig. 16.3 GC with mass-exact labels obtained from the MS of a,(u-bis(trimethylsilyl)-1,4-polybutadiene containing 3, 4, and 5 units of M. For each value of m/z there are two or more GC peaks corresponding to the various cis/trans isomers that are formed during degradation...

Figure 4.1.5. Volume of the increased swelling of crosslinked polybutadiene urethane elastomer, Xh b-85. Labels of points ...

Notes The values of A, B, and C and thus of y are based on a reference volume Vre/ = 0.1 nm Polymer notation A d- label preceding the polymer acronym indicates a per-deuterated polymer partially deuterated polymers are labeled as dy, df, etc., for selective deuteration of 3, 4, etc., hydrogens. Numbers in subscripted parentheses after the polymer name indicate the primary comonomer fraction, e.g., SPB(6s) is a saturated polybutadiene with 66 mol% butadiene Polymer acronyms P2VP poly(2-vinyl pyridine), P4MS poly(4-methylstyrene), PBMA poly(n-butyl methacrylate), PCHA poly(cyclohexyl acrylate), PEB poly(ethyl butylene), PIB polyisobutylene, PI polyisoprene, PMMA poly(methyl methacrylate), PPMA poly(n-pentyl methacrylate), PP polypropylene, HHPP head-to-head polypropylene, PS polystyrene, PVME poly(vinyl methyl ether), PXE poly(2,6-dimethyl-l,4-phenylene oxide), SPB saturated polybutadiene, SPI saturated polyisoprene... 

Experimental work is consistent with the view that solvent specific corrections to the intramolecular potential are not required in the absence of strong polymer/solvent interactions. Glowinkowski et al. used CNMR to study the local dynamics of polyisoprene in ten solvents as a function of temperature [31]. They measured correlation times due to the motion of differmt C-H vectors in the chain backbone. They found that these correlation times were determined by oidy the temperature and the solvent viscosity. Variables such as solvent shape, flexibility, and chemical functionality had no effect on the correlation times, except through the solvent viscosity. (Highly polar solvents were excluded from this study as they do not dissolve polyisoprene.) Similar conclusions have been reached in NMR studies of polybutadiene [52] and in time-resolved optical studies of polyisoprene [53] and polystyrene [54] with anthracene labels. NMR studies of PEO [55] have been interpreted as supporting this same conclusion [31] (except when the solvent was water [56]). 

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