Vinyl polymers experimental

We conclude that the difference between the experimental value and the no-transfer value of the fluorescence ratio of P2VN and PS is less in solution than in dilute miscible blends, because energy migration must compete with rotational processes in the generation of excimers in solution. This difference is also present when the effect of molecular weight on aryl vinyl polymers in solution and in dilute miscible blends is considered in the next section. 

Analogous investigations yielded interesting results also in the field of optically active vinyl polymers. In some cases a remarkable dependence of the optical activity on stereoregularity was experimentally found and optical activity has been used to study the relationships between stereoregularity and conformation of the macromolecules in solution. 

Such a model is in agreement with all the experimental findings till now ascertained in the field of optically active vinyl-polymers in fact it explains, in the case of polymers having asymmetric carbon atoms in a or j position with respect to the principal chain, the relationships between absolute structure of monomers and sign of the rotatory power of polymers, and the high rotatory power observed in isotactic polymers. The rapid and reversible variation of the optical rotation with temperature (105) is probably connected with the existence of a conformational equilibrium that is rapidly attained at each temperature. 

Blocking - [AMIDES, FATTY ACID] (Vol 2) -m experimental design [DESIGN OF EXPERIMENTS] (Vol 7) -in PVAc [VINYL POLYMERS - VINYL ACETATE POLYMERS] (Vol 24)... 

Figure 8.39 Screw characteristic curves for various power law indeces. Experimental values are shown for a carboxyl vinyl polymer with n = 0.5 and corn starch (Newtonian) with n = 1 [9].

The conformational considerations lead us to expect that the monolayer thickness differs among the three classes that is accessible experimentally by the reflectivity techniques [94], For instance, fatty acid monolayers have thicknesses on the order of 20 A [95,96], whereas the vinyl polymer mono-layers of the first kind can have thicknesses of less than 10 A [97]. On the other hand, the other class of vinyl polymers gives rise to thicker mono-... 

Apparently, mammals do not pcKsess any enzymes capable of the degradation of vinyl polymers. Two weeks after the injection, polyvinyl analogs from liver and spleen were compared with the original sample distribution of molecular weights was found identical whithin the limits of experimental error ... 

At the phenomenological level it may be known that Solvent A works well with acrylic dispersions while Solvent B is better for vinyl dispersions. Experimentally the important question of how much to add can be determined by systematic experimentation. However, for fine tuning some theoretical knowledge about the influence of transient solvent on the glass transition temperature (Tg), and tihe influence this will have on the minimum film forming temperature (MFT) is usefiil. This would undoubtedly lead to some consideration of the distribution (partitioning) of the solvent between the aqueous and polymer phases, which can be... 

This procedure provides poor reproducibility, because the pyrolysis products depend strongly on the experimental conditions, but provides a useful analytical tool in the identification of acrylic and vinylic polymers or monomer units from polyester, polyurethane, and phenolic and polyacrylate resins. 

Coupled relaxation in vinyl polymers in solution has been studied by Heatley and co-workers.By measuring under decoupling conditions, it is possible to study low-frequency motions ( kHz) as well as those at high frequencies ( MHz) accessible via the normal unperturbed relaxation times. Experimental data for poly(vinyl acetate) in toluene and polystyrene in several solvents were analysed in terms of equation (1). For poly (vinyl acetate), the ratio p/0 increased markedly with decreasing temperature, whereas for polystyrene, the ratio remained constant at ca. 0.1. 

It is shown in Section 1.6.3 that, on theoretical grounds, vinyl polymers may be expected to have a head-to-tail structure. For polystyrene there is experimental evidence that this is indeed the case. When polystyrene is pyrolysed in vacuo at 290-320°C the following fractions are obtained [5] ... 

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