Backbone, typical

In the case of water-soluble polymers, there is another factor that has to be taken into account when considering solubility, namely the possibility of hydrophobic interactions. If we consider a polymer, even one that is soluble in water, we notice that it is made up of two types of chemical species, the polar functional groups and the non-polar backbone. Typically, polymers have an organic backbone that consists of C—C chains with the majority of valence sites on the carbon atoms occupied by hydrogen atoms. In other words, this kind of polymer partially exhibits the nature of a hydrocarbon, and as such resists dissolution in water. 

Much more research has been carried out with polymers in which the coordinated metal atom is part of the chain backbone. Typically, the metal atoms are copper, nickel, and cobalt. Oxygen atoms or carbon atoms adjacent to the metal atom provide the electrons required for the coordinate bond.30 Polymers of this type are often rather intractable, for a variety of reasons. Specifically, insolubility can be a problem for species with moderate molecular weights. Also, coordination between chains can cause aggregation, and ligand-exchange reactions with small molecules such as solvents can cause chain scission. However, in some favorable cases, the intramolecular coordination is sufficiently strong for the polymer to be processed by the usual techniques such as spinning into fibers or extrusion into films.30... 

The chemical shift interaction is most frequently studied and a number of chemical shift tensors are well characterized in polymers [6-8]. For both an analysis of structure and dynamics it is important that the tensor element magnitudes and tensor element orientations relative to the molecular frame (i.e., the covalent bonds associated with nuclear sites) be known. Fig. 6.4.1 shows the orientation of the amide chemical shift tensor with respect to the molecular frame as defined by two Euler angles for amide nitrogens in a polypeptide backbone, typically od = 0 5° and ]8d = 104 2° [9j. 

General Considerations. The terms addition and condensation polymers were first used by Carothers and are based on whether the repeating unit, mer, of a polymer chain contains the same atoms as the monomer Addition polymers have the same atoms as the monomer in the repeat unit, with the atoms in the backbone typically being only carbon. Condensation polymers typically contain fewer atoms within the repeat unit than the reactants because of the formation of byproducts during the polymerization process, and the polymer backbone typically contains atoms of more than one element. Polystyrene, poly(vinyl chloride), polyethylene, and poly(vinyl alcohol) are illustrative of addition polymers, and polyesters and polyamides (nylons) are illustrative of condensation polymers. The corresponding polymerizations are then called addition and condensation polymerizations. 

Fluoropolymers for 157 nm lithography can be categorized into two groups 1) polymers containing F in the backbone, typically prepared by copolymerization involving tetrafluoroethylene (TFE) and 2) polymers containing F in the side chain (Fig. 83). NBHFA has been copolymerized with NBTBE,NBHFA... 

In Jpjj and coupling, the phosphorus and hydrogen atoms are separated by one fj) or two ( J) atoms of the backbone - typically carbon atoms. This arrangement leads to a Karplus-like dependance of the and vicinal Jpjj coupling constants on the dihedral angle 0. 

Nonchain scission refers to reactions involving pendant groups that do not break the backbone. Typical of such reactions are dehydrochlorination of poly( vinyl chloride) (Equation 1.57), elimination of acid from poly(vinyl esters)—for example, poly(vinyl acetate) (Equation 1.58)—and elimination of alkene from poly(alkyl acrylate)s (Equation 1.59). 

Some polysiloxanes have cyclic groups in the backbone, typically cyclics of -Si(CHg)j-0- units of various sizes, or such siloxane units mixed with some carbosiloxanes (with additional -CH - sequences). " -cyclic portions can add considerable stiffness, resulting in isotropization temperatures above the decomposition temperatures. 

CPs usually consist of a backbone and side chains, shown in Figure The backbones typically contain n-... 

To illustrate briefly this problem let us consider a one dimensional chain of hydrogen bridges. This is a possibility in several polymers, especially polypeptides. Such a chain has a backbone typically represented by... 

Radical polymerization is the workhorse of many polymer chemists and has been used extensively to fabricate materials, which are easily scalable and also having multiple characteristics due to the different monomers in the polymer backbone. Typical monomers polymerized include N-isopropylacrylamide (NIPAAm) and... 

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