Polarization polymer chains

Polymers with rigid, cyclic structures in the polymer chain, as in cellulose and poly(ethy-leneterephthalate), are difficult to crystallize. Moderate crystallization does occur in these cases, as a result of the polar polymer chains. Additional crystallization can be induced by mechanical stretching. Cellulose is interesting in that native cellulose in the form of cotton is much more crystalline than cellulose that is obtained by precipitation of cellulose from... 

Polymers filled with ultrafine metal particles form periodic stripes. These stripes are thought to be caused by an inhomogeneous electric field which induces electrostatic interactions among the polarized polymer chains. The phenomenon is known as mutual dielectrophoresis. 

Functional polymers are macromolecules that have unique properties or uses. The properties of such materials are often determined by the presence of chemical functional groups that are dissimilar to those of the backbone chains. Examples are polar or ionic functional groups on hydrocarbon backbones or hydrophobic groups on polar polymer chains. Chemical heterogeneity on the polymer chains can le to enhanced reactivity, phase separation, or association. The ability of functional polymers to form self-assemblies or supramolecular stmctures is a further incentive. When the formation or dissociation of the self-assemblies is triggered by chemical or physical stimuli so called smart materials can result ... 

Why are two species of non-polar polymer chains not easy to mix with each other ... 

NADs are always sterically stabilized, so the surfactant is polymeric. Frequently graft copolymers are used. These contain polar polymer chains, which anchor well onto the dispersed particles and which are chemically bonded (or grafted ) onto non-polar polymer chains which are soluble in the continuous phase ... 

Thermoplastic elasto-ionomers, whose network knots are thermolabile ionic microdomains formed by associations between ionic groups (carboxylic or sulfonic acids) present in non-polar polymer chains. ... 

To make the modified surface properties (hydrophilic/hydrophobic) more permanent, siuface-modifying macromolecules (SMMs) were developed. SMM has an amphi-phatic structure consisting theoretically of a main polyurethane chain terminated with two low polarity polymer chains (i.e., fluorine segments) [65]. 

In the 1930s the first type of polyalkene formed was low-density poly(ethene) (LDPE) and it is still useful today. Its non-polar polymer chains interact with each other by van der Waals forces. As the chains are heavily branched, not straight chains, these intermolecular forces are relatively weak for such large molecules. The random branching makes it impossible for the polymer chains to pack neatly together and accounts for its low density and low melting temperature (see Figure 28.20). 

Figure 28.20 The branched chains of LDPE. The van der Waals forces between the non-polar polymer chains are affected not only by the size of the chains but also their inability to pack closely together, reducing the effectiveness of instantaneous dipoles in one chain to induce dipoles on neighbouring chains.

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