Functional Groups in Polymers

Functional groups that may have to be determined include unsaturation, hydroxy, carbonyl, carboxyl, alkyl, aryl, alkoxy, oxyalkylene, nitrile, ester, amino, nitro, amide, amido, imino, and epoxy groups. Comonomer ratios, isomers, and short-chain branching are all structural features of polymers that may have to be elucidated in order to obtain a complete picture of polymer structure. 

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Nonintentional food additives, 12 29 Noninteracting solvents, 23 99 Nonionic emulsifiers, in VDC emulsion polymerization, 25 722-723 Nonionic functional groups, in polymer colloids, 20 384... 

Further details of the theory and application of Raman spectroscopy in polymer studies can be found elsewhere (1. 9). However, vibrational frequencies of functional groups in polymers can be characterized from the spacing of the Raman lines and thus information complementary to IR absorption spectroscopy can be obtained. In addition, since visible radiation is used the technique can be applied to aqueous media in contrast to IR spectroscopy, allowing studies of synthetic polyelectrolytes and biopolymers to be undertaken. Conformation and crystallinity of polymers have also been shown to influence the Raman spectra Q.) while the possibility of studying scattering from small sample volumes in the focussed laser beam (-100 pm diameter) can provide information on localized changes in chemical structure. 

Table 1.22 Some of the More Important Functional Groups in Polymer Chemistry...

Polymer-Analogous Conversions of Functional Groups in Polymer Chains... 

Photophysical and photochemical processes in polymer solids are extremely important in that they relate directly to the functions of photoresists and other molecular functional devices. These processes are influenced significantly by the molecular structure of the polymer matrix and its motion. As already discussed in Section 2.1.3, the reactivity of functional groups in polymer solids changes markedly at the glass transition temperature (Tg) of the matrix. Their reactivity is also affected by the / transition temperature, Tp, which corresponds to the relaxation of local motion modes of the main chain and by Ty, the temperature corresponding to the onset of side chain rotation. These transition temperatures can be detected also by other experimental techniques, such as dynamic viscoelasticity measurements, dielectric dispersion, and NMR spectroscopy. The values obtained depend on the frequency of the measurement. Since photochemical and photophysical parameters are measures of the motion of a polymer chain, they provide means to estimate experimentally the values of Tp and Tr. In homogeneous solids, reactions are related to the free volume distribution. This important theoretical parameter can be discussed on the basis of photophysical processes. 

Distribution of functional groups in polymer-supported reagents wd catalysts has been studied with a scanning electron microprobe. Chloromethylation of 2% cross-linked 300-600 nm polystyrene beads with chloromethyl methyl ether and stannic chloride to 0.67 mequiv Cl/g (2S) followed by phosphination with lithium diphenyl-... 

The dissolution of polymer is determined by chain flexibility. The mechanism of dissolution consists of separating chains from each other and their transfer into solution. If a chain is flexible, its segments can be separated without a large expenditure of energy. Thus functional groups in polymer chain may interact with solvent molecules. 

A selective size domain can be obtained by cross-linking of functional groups in polymers, thereby constructing a supramolecular structure. 

Some applications of infrared spectroscopy to the determination of functional groups in polymers are discussed next. 

Ionization state the most powerful tool for finding the chemical properties of functional groups in polymer blend, such as the ionization states of ion-izable groups at the active sites of rubber molecules. 

Methods based on determination of specific elements In certain cases, the polymers contain functional groups of some specific element. For these polymers, it is sufficient to analyze the polymers for that particular element, and the degree of functionalization can be determined from the percentage of that element. In this case, it is assumed that no low-molecular-weight substances are adsorbed or entrapped in the polymer. Table 3-1 lists typical examples of the functional groups in polymers that can be determined by elemental analysis. 

Functional Groups in Polymers That Can Be Determined by Chemical Methods... 

III. PHYSICAL AND PHYSICOCHEMICAL METHODS OF DETERMINING FUNCTIONAL GROUPS IN POLYMERS... 

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