Rigid linear polymer

The molecular architecture of a polyphosphazene has a profound influence on properties. For example, linear and tri-star trifluoroethoxy-substituted polymers with the same molecular weight (1.2 x 104 or higher) have strikingly different properties.138 The linear polymers are white, fibrous materials that readily form films and fibers, whereas the tri-arm star polymers are viscous gums. One is crystalline and the other is amorphous. Cyclolinear polymers are usually soluble and flexible. Cyclomatrix polymers are insoluble and rigid. Linear polymers can be crystalline, but graft or comb polymers are usually amorphous. 

Several theoretical works predict the onset of mesophases (1-5) and take into account the molecular structure of polymers. There are two kinds of structures that are often cited the rigid or semi-rigid linear polymers and the connected ones or those containing mesogenic side chains ( ). 

We now imagine many fractal objects floating in solution. Our main interest is the case where these objects are polymers. But we shall try to make our reasoning applicable for any connected fractal structures, with general dimension D. In this way our conclusions will be applicable to several types of fractal structure that impart special properties to liquids random-walk and rigid linear polymers [8.9], branched polymers (see Chap. 2), and colloidal aggregates 8,17. ... 

Many complex systems have been spread on liquid interfaces for a variety of reasons. We begin this chapter with a discussion of the behavior of synthetic polymers at the liquid-air interface. Most of these systems are linear macromolecules however, rigid-rod polymers and more complex structures are of interest for potential optoelectronic applications. Biological macromolecules are spread at the liquid-vapor interface to fabricate sensors and other biomedical devices. In addition, the study of proteins at the air-water interface yields important information on enzymatic recognition, and membrane protein behavior. We touch on other biological systems, namely, phospholipids and cholesterol monolayers. These systems are so widely and routinely studied these days that they were also mentioned in some detail in Chapter IV. The closely related matter of bilayers and vesicles is also briefly addressed. 

Rea.ctlons, Butynediol undergoes the usual reactions of primary alcohols. Because of its rigid, linear stmcture, many reactions forming cycHc products from butanediol or i j -butenediol give only polymers with butynediol. 

At present, it is known that the structures of the ECC type (Figs 3 and 21) can be obtained in principle for all linear crystallizable polymers. However, in practice, ECC does not occur although, as follows from the preceding considerations, the formation of linear single crystals of macroscopic size (100% ECC) is not forbidden for any fundamental thermodynamic or thermokinetic reasons60,65). It should be noted that the attained tenacities of rigid- and flexible-chain polymer fibers are almost identical. The reasons for a relatively low tenacity of fibers from rigid-chain polymers and for the adequacy of the model in Fig. 21 a have been analyzed in detail in Ref. 65. 

Both thermosets and thermoplastics are used as food-contact materials, though thermoplastics predominate in this appfication. Examples of the former are phenol- and urea-formaldehyde, while probably the best known example of the latter is low-density poly(ethylene). Other linear polymers are used include high-density poly(ethylene), poly(propylene), and PVC, all of which find quite extensive use. Polymers for food packaging may be in the form of films and other flexible items, or in the form of rigid containers, such as clear drinks bottles or opaque cartons for dairy products. 

The molar mass dependence of the intrinsic viscosity of rigid chain polymers cannot be described by a simple scaling relation in the form of Equation (36) with molar mass independent of K and a. over a broad molar mass range. Starting from the worm-like chain model, Bohdanecky proposed [29] the linearizing equation... 

Some polymer materials, particularly biomedical materials and step-growth polymers, comprise crosslinked networks. The effect of irradiation on networks, compared with linear polymers, will depend on whether scission or crosslinking predominates. Crosslinking will cause embrittlement at lower doses, whereas scission will lead progressively to breakdown of the network and formation of small, linear molecules. The rigidity of the network, i.e. whether in the glassy or rubbery state (networks are not normally crystalline), will affect the ease of crosslinking and scission.. ... 

The solution properties of dendrigraft polybutadienes are, as in the previous cases discussed, consistent with a hard sphere morphology. The intrinsic viscosity of arborescent-poly(butadienes) levels off for the G1 and G2 polymers. Additionally, the ratio of the radius of gyration in solution (Rg) to the hydrodynamic radius (Rb) of the molecules decreases from RJRb = 1.4 to 0.8 from G1 to G2. For linear polymer chains with a coiled conformation in solution, a ratio RJRb = 1.48-1.50 is expected. For rigid spheres, in comparison, a limiting value RJRb = 0.775 is predicted. 

The difunctional N-cyanourea compounds were found to polymerize into different polymeric materials at different temperatures. At room temperature, a linear polymer was obtained either from the polymerization of a di-N-cyanourea monomer or directly from the mixture containing a diisocyanate and cyanamide. At elevated temperature (>100°C), the di-N-cyanourea monomer, or the mixture of a diisocyanate and cyanamide, cross-linked to a rigid foam or flexible material, depending on the structure of the monomer. 

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