Poly structural characteristics

Table 9.8 Structural characteristics of G1 dendritic poly(ethylene oxides) obtained by terminal grafting (adapted from ref. 20)...

Simmons S, Thomas EL (1995) Structural characteristics of biodegradable thermoplastic starch/poly(ethylene-vinyl alcohol) blends. J Appl Polym Sci 58 2259-2285... 

The preceding structural characteristics dictate the state of polymer (rubbery vs. glassy vs. semicrystalline) which will strongly affect mechanical strength, thermal stability, chemical resistance and transport properties [6]. In most polymeric membranes, the polymer is in an amorphous state. However, some polymers, especially those with flexible chains of regular chemical structure (e.g., polyethylene/PE/, polypropylene/PP/or poly(vinylidene fluoride)/PVDF/), tend to form crystalline... 

Characterization of the poly(macromonomers) prepared by homopolymerization has proved that they provide a useful probe for discussing the structural characteristics of the star and brush polymers. Graft copolymers have been and will be a most important area of application of the macromonomer technique since a variety of multi-phased and microphase-separated systems can easily be designed just by an appropriate combination of a macromonomer and a conventional monomer. In general, however, characterization of their absolute MW, branch/backbone composition as well as their distributions remain to be studied in more detail. 

Congenericity is a fuzzy concept related to the structures of the molecules of the studied dataset. With respect to some defined molecular structural characteristics, chemical analogues can be considered congeneric compounds, their structural differences being the interesting part of the study. Mono-substituted benzenes, polychlorobiphe-nyls, triazines, and poly-aromatic hydrocarbons are all examples of congeneric datasets. 

The blending of different polymers is a frequently used technique in industrial polymer production to optimize the material s properties. The biodegradable polymer poly(3-hydroxybutyrate) (PHB) [45, 46], for example, which can be produced by bacteria from renewable resources, has the disadvantage of being stiff and brittle. The mechanical properties of PHB, however, can be readily enhanced by blending with another biopolymer, poly(lactic acid) (PLA) [47]. In order to prepare the optimum blend, it must be noted that the miscibility of different polymers depends on their concentration, the temperature, and their structural characteristics [48]. 

Chitosan is a linear randomly distributed, binary heteropolysaccharide prepared by deacetylation of chitin, a linear polymer of P(l-4) linked N-acetyl-o-glucosamine units composed of mucopolysaccharides and amino sugars. It is a natural poly-(aminosaccharide), having structural characteristics similar to glycosaminoglycans. 

Davidovich-Pinhas, M., Bianco-Peled, H. Physical and structural characteristics of acrylated poly(ethylene glycol)-alginate conjugates. Acta Biomater. 7, 2817-2825 (2011)... 

The synthesis of model compounds mimicking the structural characteristics of the possible subunits, and the comparison of their spectra with that of the hb polymer, represents a common method for assigning signals to subunits. This procedure, for the assignment of urea and urethane carbonyl carbon signals of a hb poly(urea urethane) synthesized from an AA (2,4-toluylene diisocyanate) and B2 B (diethanol amine) monomer [94], is shown in Figure 24.3. 

Sugijama, H., Lewis, D., White, J. Structural Characteristics, Rheological Properties, Extrusion and Melt Spinning of 60/40 Poly(Hydroxybenzoic Acidcoethylene Terephtalate). 

The crystal structure of PHB is a orthorhombic form with unit cell parameters fl = 0.576 nm, = 1.320 nm, and c(fiber axis)=0.596 nm, and space group P2,2,2, (Alper et al. 1963 Okamura and Marchessault 1967). The conformational analysis by intermolecular energy calculation has indicated that the PHB molecule has a left-handed 2j helix conformation (Comibert and Marchessault 1972 Yokouchi et al. 1973 Bruckner et al. 1988). The crystal structure of random copolymers of 3HB and 3HV has been investigated extensively (Bloembergen et al. 1986 Kamiya et al. 1991 VanderHart et al. 1995). A structural characteristic of poly(3HB-co-3HV) is isodimorphism, i.e., cocrystallization, of the two monomer units. In contrast, the cocrystallization of 3HB with 3HH or (7 )-6-hydroxyhexanoate (6HH) does not occur. 

Queiroz DP, de Pinho MN (2005) Structural characteristics and gas permeatimi properties of poIydimethyIsiioxane/poly(propylene oxide) urethaneAueabi-sofl segment membranes. Polymer 46 2346-2353... 

Van, S., Yin,)., Yang,)., and Chen, X. (2007) Structural characteristics and thermal properties of plasticized poly(L-lactide)-silica nanocomposites synthesized by sol-gel method. Mater. Lett., 61 (13), 2683-2686. 

De Sitter K, Winberg P, D Haen J, Dotremont C, Leysen R, Martens JA, Mullens S, Maurer FHJ, Vankelecom IFJ (2006) Silica filled poly(l-trimethylsilyl-l-propyne) nanocomposite membranes relation between the transport of gases and structural characteristics. J Membr Sci278(l-2) 83-91... 

During the past several years, it has become clear that poly(ADP-ribose) synthetase has two unique features (1, 2). One is that the enzyme requires DNA for catalytic activity and another is that the enzyme is subjected to automodification during the reaction. These two unique features wUl provide us with a key for clarifying the physiological function of this enzyme in vivo. In this article, we wLU present our recent data on molecular cloning of human poly(ADP-ribose) synthetase and will discuss the physiological functions of this enzyme on the basis of its structural characteristics. 

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