Branched polymers spectroscopic methods

Polymerization in electrostatic systems like the ones mentioned above is stericaUy inhibited by alkyl substitution at the a-carbon which must assume a coordination number greater than 4. Coates and Glockhng have treated this inhibition of polymerization in terms of decreased electronegative character of the branched alkyl groups. Therefore, stimulated by the idea that f-afkylhthium compounds may exist as low polymers or even as monomeric molecules, Weiner and coworkers and Kottke and Stalke have isolated f-butyllithium as a pure substance for the first time and characterised it by spectroscopic methods and X-ray diffraction. The colourless crystalline solid was found to be tetrameric over a range of concentrations in both benzene and hexane ... 

Infrared spectroscopic methods are extensively used to analyse polymers due to their simplicity, rapidity, reproducibility, non-destructive character and ease of sample preparation. Degree of crystallinity [73], chain branching [74], degree of oxidation [75], density measurements [76], quantification of additives [75, 77], end-group analysis [78, 79] and other physical/chemical properties have been studied using MIR and/or NIR. 

Short-branch grafts, even in appreciable concentration, may be difficult to quantify by methods of coil size determination. However, compositions in this range can be susceptible to spectroscopic analysis as by infrared and by carbon-13 nuclear magnetic resonance [45]. Adsorption characteristics as well as solubility can also be useful in evaluating polymer blocks and grafts. For example, vinyl acetate grafts to poly(vinyl alcohol) and mixed... 

Spectroscopic techniques are of great importance in polymer science, as they are in all branches of the chemical sciences, and these are dealt with in chapters 3 and 4. NMR is of prime importance as a method for identification and elucidation of the structure of polymer chains, and a complete chapter has been devoted to this technique. In recent years it has become an increasingly sophisticated and correspondingly expensive technique, requiring considerable skill in operating the spectrometer and in interpreting spectra, but it is still available in a simple and routine form in many laboratories. Vibrational spectroscopy encompasses infrared (IR) and Raman. These techniques, IR in... 

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