Vinyl polymers characteristics

Poly(A/-vinyl-2-pyrrohdinone) (PVP) is undoubtedly the best-characterized and most widely studied A/-vinyl polymer. It derives its commercial success from its biological compatibiUty, low toxicity, film-forming and adhesive characteristics, unusual complexing abiUty, relatively inert behavior toward salts and acids, and thermal and hydrolytic stabiUty. 

In the previous section, the adaptation of the RIS model was based on the distance between next-nearest neighbor beads. This approach is obviously inadequate for CH3-CHX-CH2-CHX-CH3, because it necessarily abandons the ability to attribute different conformational characteristics to the meso and racemo stereoisomers. Therefore a more robust adaption of the RIS model to the 2nnd lattice is necessary if one wants to investigate the influence of stereochemical composition and stereochemical sequence on vinyl polymers [156]. Here we describe a method that has this capability. Of course, this method retains the ability to treat chains such as PE in which the bonds are subject to symmetric torsion potential energy functions. 

The longest relaxation time. t,. corresponds to p = 1. The important characteristics of the polymer are its steady-state viscosity > at zero rate of shear, molecular weight A/, and its density p at temperature 7" R is the gas constant, and N is the number of statistical segments in the polymer chain. For vinyl polymers N contains about 10 to 20 monomer units. This equation holds only for the longer relaxation times (i.e., in the terminal zone). In this region the stress-relaxation curve is now given by a sum of exponential terms just as in equation (10), but the number of terms in the sum and the relationship between the T S of each term is specified completely. Thus... 

Radical polymerization is the most useful method for a large-scale preparation of various kinds of vinyl polymers. More than 70 % of vinyl polymers (i. e. more than 50 % of all plastics) are produced by the radical polymerization process industrially, because this method has a large number of advantages arising from the characteristics of intermediate free-radicals for vinyl polymer synthesis beyond ionic and coordination polymerizations, e.g., high polymerization and copolymerization reactivities of many varieties of vinyl monomers, especially of the monomers with polar and unprotected functional groups, a simple procedure for polymerizations, excellent reproducibility of the polymerization reaction due to tolerance to impurities, facile prediction of the polymerization reactions from the accumulated data of the elementary reaction mechanisms and of the monomer structure-reactivity relationships, utilization of water as a reaction medium, and so on. 

The presence of helical conformations in nascent vinyl polymers has often been advanced as an explanation for some of the characteristics of stereoregular... 

Landells, G., and C. S. Whewell Preparation and properties of regenerated cellulose containing vinyl polymers. I. Internal deposition of polymers. J. Soc. Dyers Colourists 67, 338 (1951). II. Staining, swelling, and stiffness characteristics. J. Soc. Dyers Colorists 71, 171 (195S). III. Moisture relations. J. Soc. Dyers Colorists 73, 496 (1957). 

Figures 8.37 and 8.38 [9] present velocity and temperature fields across the thickness, respectively, for various values of Br, and forn = 1 and n = 0.6. Griffith calculated the screw characteristic curves for Newtonian and non-Newtonian shear thinning fluids using various power law indices. Figure 8.39 presents these results and compares them to experiments performed with a carboxyl vinyl polymer (n = 0.2) and corn starch (n = 1).

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].

Because of this structural characteristics vdiich are much different from those of vinyl polymers, polyethyleneimine (PEI) is eicpected to provide interesting microenvironments for catalysis. Femandez-Prini and Turyn studied the deconq>osition of p-nitrophenyl fhosphate 2 in the presence of polyetih>ieneimine (114). 

Poly(amino acids) are attractive enzyme models because of their structural similarity. In fact, characteristic pH dependences of the cataljrtic rate were found and this was considered to reflect the conformational peculiarity of poly(amino acids). Unfortur nately, rate enhancements are only moderate and characterization of the catal3rtic site is difficult. Interesting results were obtained in the catalysis of oligopeptides, which supposedly mimic the active site of some hydrolytic enzymes. The stereoselectivity seems to be realized with oligopeptides more easily than with vinyl polymer catalysts. 

Figure 3. Solubility characteristics of typical vinyl polymers in MEK (Brook-...

Much has been written about ketones, as a class, as excellent solvents for vinyl polymers (7,8). Aside from solubility of the solvent, we also must consider its volatility characteristics (evaporation rate), flash point, boiling range, etc. With the high solubility type polymers, we have wide latitude with respect to selecting the ketone that will balance these properties against solution solids. This is evident in the next figures. 

Figure 30. Solubility characteristics of vinyl polymer types in methyl n-butyl ketone (Brookfield LVF viscometer)...

This chapter introduces the most predominant enzyme classes used for vinyl polymerization so far. An overview the current mechanistic understanding as well as selected practical examples are given. Complementary to the content of this chapter, detailed enumerations of polymer characteristics can be obtained from some excellent reviews [2-5]. 

The influence of [02], [laccase] on the performance of the laccase-initiated polymerization of vinyl monomers is essentially the same as observed with peroxidases (6.3.2) [69], Thus, the polymer characteristics are inversely correlated with [laccase] and [monomer], [Acac] exceeds only in minor effect on the polymer weight with the exception of very low [Acac] [69], Here, no polymerization was observed unless the [02] was reduced significantly. This indicates an 02-dependent irreversible inactivation mechanism of the Acac radical. The mechanism of this inactivation however remains to be elucidated. On the other hand, [02] may be an efficient handle to control the average molecular weight of the resulting... 

The nonreactive NAD are structures without polymerisable double bonds, but have a remarkable stabilisation effect on polymeric dispersions in polyether media. The main characteristic of such kinds of nonreactive NAD is to have an organic segment with high affinity for the carbocatenary vinylic polymer chemically linked to a high molecular weight polyether chain, which has a high affinity for the continuous liquid polyether matrix. 

A.L.R. Williams and D.G. Borden, The preparation and properties of photoreactive polymers I. 2 (arylvinyl) N vinylpyridinium arylsulfonate polymers, Makromol. Chem. 73, 203 (1964) D.G. Borden and J.L.R. Williams, Photopolymer design Photocrosslinkable styrylpyridinium substituted vinyl polymers with absorption maxima from 270 nm to 540 nm, Makromol. Chem. 178, 3035 (1977) K. Ichimura and N. Oohara, J. Polym. Set, Polym. Chem. Ed. 25, 3063 (1987) K. Ichimura and S. Watanabe, Immobilization of enzymes with use of photosensitive polymers having the stilbazolium group, J. Polym. Sci. Polym. Chem., Ed. 18, 891 (1980) K. Ichimura, Prep aration of water soluble photoresist derived from poly(vinyl alcohol), J. Polym. Sci. Polym. Chem., Ed. 20, 1411 (1982) Preparation and characteristics of photocross linkable poly(vinyl alcohol), 20, 1419 (1982). 

Synthetic poly(amino acids) possess advant s as well as disadvantages as enzyme models, when compared widi vinyl polymers. The greatest advantage is probably the structural similarity of the polymer backbone (polypeptide linkage), and conformational characteristics derived therefrom. On the odier hand, die syndietic problems are much greater than those of vinyl polymers. A review artide was recently published on tfiis subject (726). 

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