Polymer Chemistry and Microstructure

Comprehensive Analytical Chemistry, Volume 53 ISSN 0166-526X, DOI 10.1016/S0166-526X(08)00402-9 

Natural polymers are far more complex materials, being exclusively organic , that is, products of life (cellulose, proteins, DNA.). Nevertheless, as nature seems to have formed (size, weight, hardness, etc.) several natural polymers (wood, bones, ivory, etc.) in such a way as to be almost immediately usable by our ancestors, they were most probably the bases of the first human tools. The commonly widespread conception that polymers are the youngest materials in the historical world is not true, but, strictly speaking, only applies to synthetic polymers, which were discovered about 100 years ago, early in the XXth century. 

Characterisation covers a wide field of science and technology and interacts from the synthesis stage through the analysis of structure to the determination of properties. Characterisation allows one to observe, control and model (including closed-loop backward interaction) all the complex interrelationships of materials science. 

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As a summary to this chapter focusing on polymer chemistry and microstructure, major characteristics of polymers are reported in Table 9, classified under... 

The analysis viscoelasticity performed by David Roylance [25] is a nice outline about the mechanical response of polymer materials. This author consider that viscoelastic response is often used as a probe in polymer science, since it is sensitive to the material s chemistry and microstructure [25], While not all polymers are viscoelastic to any practical extent, even fewer are linearly viscoelastic [24,25], this theory provide a usable engineering approximation for many applications in polymer and composites engineering. Even in instances requiring more elaborate treatments, the linear viscoelastic theory is a useful starting point. 

As mentioned previously, chemistry and physico-chemistry play major roles in polymer microstructure, and, as a consequence, on polymer properties. The characterisation of several chemical parameters of polymer chains is thus of paramount importance for controlling the final properties of polymer materials... 

Ionic cross-linking can be achieved in a number of systems and different microstructures result. For rigid chains it is possible for the ion to coordinate in a specific manner with the chain. Alginates are a good example of this. These are natural polymers derived from a brown macro-algae. The method of extraction and the species of the algae influences the chemistry and hence the rheology of these polymers. There... 

Modification of the cyclopentadienyl ligands has led to a very rich chemistry and today a great variety of microstructures and combination thereof can be synthesised as desired including isotactic polymer with melting points above 160 °C, syndiotactic polypropene [16], block polymers, hemi-isotactic polymers etc. 

Anionic polymerizations initiated with alkyllithium compounds enable us to prepare homopolymers as well as copolymers from diene and vinylaromatic monomers. These polymerization systems are unique in that they have precise control over such polymer properties as composition, microstructure, molecular weight, molecular weight distribution, choice of functional end groups and even copolymer monomer sequence distribution. Attempts have been made in this paper to survey these salient features with respect to their chemistry and commercial applications. 

Clearly, an enormous number of new polymers have and continue to be synthesized using ROMP reactions. The development of the new generation of single-site aUcylidene catalysts has introduced a new level of control over ROMP chemistry. Control of polymer microstructure should, in turn, result in a better understanding of the interplay between microstmcture and macroscopic properties. The use of living ROMP chemistry is still in its infancy. It will be interesting to observe whether or not useful materials can be developed from this chemistry. 

The principal problem of polymer science is the mastering of methods for obtaining materials with predetermined properties. Consequently, the main task of polymer chemistry is the development of the methods of synthesis of polymers which exhibit, in principle, any theoretically possible primary structure of macromolecules. At present, many empirical data have been accumulated in the field of experimental chemistry, which in many cases, make it possible to synthesize polymers with a predetermined primary microstructure. In particular, the most interesting in this sense is the available experience of the synthesis of stereoregular polymers. On the whole, the successful fulfilment of this program requires a reasonable and harmonious combination of empirical and theoretical approaches. 

Gopferich, A. and R. Langer, The influence of microstructure and monomer properties on the erosion mechanism of a class of polyanhydrides. Journal of Polymer Science Part A Polymer Chemistry, 1993, 31, 2445-2458. 

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