TABLE 4.2 Potential Breakthroughs in Characterization of Polymers


Molecular Characterization


• Ways to find molecular weight distributions for insoluble polymers


• Better ways to determine branch content and sequence information


• Better ways of measuring how branch content and monomer composition are distributed over range of molecular weights


Solutions, Melts, and Elastomers


• Better ways to measure the distribution of molecular lengths between cross-links


• More intense sources of long-wavelength neutrons to make possible time-resolved experiments


• Better techniques for the preparation of isotopically labeled biomaterials


Solid-State Structure and Properties


• Energy-filtered soft X-ray microscopy


• Electron tomography


• New techniques for reducing electron radiation damage


• Chemical-imaging transmission electron microscopy


• Ways to measure plastic deformation and fracture properties of small samples


• Methods to probe mechanism of shear yielding in glassy polymers


• Methods to characterize the microscopic deformation of rubber-modified polymers at impact strain rates


• New techniques for the solution of the phase problem in biomolecules


• Computational techniques for the solution of nonglobular virus structures such as the AIDS virus and complex structures such as those of molecular motors


Surfaces and Interfaces


• Analysis techniques that can characterize curved interfaces


• Interface analysis techniques with both good depth resolution and good lateral resolution


• Ways to use atomic force microscopy to characterize local mechanical properties




• Scanning tunneling microscopy to read out biopolymer sequences


• Rapid sequencing methods


• Computer algorithms to predict biomolecular structures from sequences


• Higher-resolution electrophoretic methods for separating large biopolymers


• Time-resolved Laue diffraction methods for X-ray crystal structure determination


• Hydrogen exchange nuclear magnetic resonance for local motions and internal structure of biopolymers

The number and average molecular weight of soluble polymers can be obtained by numerous methods, including colligative property measurements, scattering, and ultracentrifugation. Viscosity measurements, which are sensitive to molecular weight, size, and polydispersity, are also useful. Size exclusion chromatography (SEC), which is sensitive to molecular size rather than weight, now may be equipped with light scattering and viscosity detectors so that absolute molecular weights can be obtained directly. Further research is needed, however,

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