Molecular Characterization of Polymers

Survey spectra using the MPI method are used primarily for quantification of surface components in inorganic materials, with a detection limit of ppm to ppb. The same mode coupled with SPI can be used for molecular characterization of polymer films. 

Miinstedt, H., Auhl, D. Rheological measuring techniques and their relevance for the molecular characterization of polymers. J. Non-newton. Fluid Mech. 128, 62-69 (2005)... 

Several parameters can be derived from the ESR spectrum and be used for molecular characterization of polymer materials. The temperature and time dependent parameters reflect the dynamical behaviors of chemical reaction and physical properties in the polymer matrices. In the classification system used here the ESR parameters are divided into a group related to molecular characterization of polymer materials (A) and examples of applications to polymer science (B). 

Conformation of macromolecules in solid state and in solution exhibits both many contingencies and restrictions. Coiled conformation of macromolecules is most appropriate for majority of methods employed for molecular characterization of polymers. Statistical coils of macromolecules in equilibrium exhibit large conformational entropy. Any external intervention that leads to a change in the conformation of macromolecules has to surmoimt considerable resistance, which is cormected with the loss of overall conformational entropy. 

In this chapter, pecuharities of the charged macromolecules will be dealt only marginally - especially to demonstrate adverse impact of charges on molecular characterization of polymers with help of liquid chromatography. 

The essential information supplied by detectors is the concentration of macromolecules in the column effluent. For comprehensive molecular characterization of polymers, additional data on eluted macromolecules are also important snch as their molar mass, composition or architecture. 

In the first chapter, an overview of thermodynamic behaviors of non-equilibrium polymers is discussed. In the consecutive chapters, different properties of polymer blends are discussed, including surface tension, transition, crystallization, morphology, and flow behaviors. Miscibility and molecular characterizations of polymer blends are also covered in this book. Applications to various systems are reviewed, and both experimental concerns and references are supplied. 

The molecular characterization of polymers is most effectively carried out by taking the polymer into solution. It is much more difficult to make analytical measurements on polymers which do not dissolve. Dissolution is not thermodynamically or kinetically favoured and polymers which are crosslinked to form a three-dimensional network cannot dissolve. 

Secondary ion mass spectrometry (SIMS), when carried out in the static (i.e., zero damage) mode, is a uniquely powerful tool for the molecular characterization of polymer surfaces. Its molecular specificity also allows the detection and characterization of additives and contaminants, whose presence at the surface can cause major changes in surface behavior, at the submonolayer level. Modern instruments based on time-of-flight (ToF) mass analyzers and liquid-metal ion sources are capable of chemical imaging with a spatial resolution of well below 1 pm. 

Relationships between the synthesis and molecular properties of polymers (Chapter 2), and between their molecular and bulk properties (Chapters 4 and 5), provide the foundations of Polymer Science. In order to establish these relationships, and to test theories, it is essential to accurately and thoroughly characterize the polymers under investigation. Furthermore, use of these relationships to predict and understand the in-use performance of a particular polymer depends upon the availability of good characterization data for that polymer. Thus polymer characterization is of great importance, both academically and commercially. The current chapter is concerned with molecular characterization of polymer samples, by which is meant the determination of their average molar masses, molar mass distributions, molecular dimensions, overall compositions, basic chemical structures and detailed molecular microstructures. Since most methods of molecular characterization involve analysis of polymers in dilute solution (<20gdm ), the relevant theories for polymers in solution will be introduced before considering the individual methods. 

The conformation plot is the scaling law between macromolecule size and molecular weight (i.e., the chain length) and it is very useful in studying the stiffness (flexible, stiff, or compact conformation) of polymers. Also branching, degree of functionalization, or derivatization could be studied using the conformation plot of the polymer. Therefore, it is very useful in the molecular characterization of polymers. 

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