Crystalline polymers experimental techniques

We first discuss the materials research which includes monomer synthesis, growth of monomer crystalline structures and polymerization in the solid state, yielding the requisite polymer structures. Next, the nonlinear optical experimental research is discussed which includes a novel experimental technique to measure x (w). Linear and nonlinear optical data obtained for the polydiacetylene films is subsequently presented. Detailed theoretical analysis relating the data to x (< >) and subsequently to its molecular basis will be discussed in a later publication. 

Introduction of ring-opening metathesis as a versatile polymerisation technique (ROMP) by Chauvin and Herisson Nobel Prize Chemistry to Paul J. Flory for his fundamental achievements, both theoretical and experimental, in the physical chemistry of the macromolecules Fully aromatic polyamides developed Aramids, being lyotropic liquid crystalline polymers of high strength, due to extended molecular chains (Morgan and Kwolek)... 

The elastic constants of liquid crystalline polymers can be measured in terms of the Frederiks transitions under the presence of a magnetic or electric field. Raleigh light scattering is also a method for measuring the elastic constants. Those techniques successfully applied to small molecular mass liquid crystals may not be applicable to liquid crystalline polymers. This is why very few experimental data of elastic constants are available for liquid crystalline polymers. 

In Section 9.3 we present experimental studies of plastic deformation in two semi-crystalline polymers, HDPE and Nylon-6, both in tension and in plane-strain compression flow, from initial spherulitic morphologies to large plastic strains. In these studies, the evolving morphological alterations were monitored closely by a complementary array of techniques involving light microscopy and X-ray diffraction and scattering both in the crystalline and in the amorphous components. 

The recently published reviews by Papkov on lyotropic liquid crystalline polymer systems (12 ) and by Shibaev and Plate on the liquid crystalline states in polymers (13) should be regarded as the first attempts to systematize the great body of available experimental data with a view to elaborating adequate techniques of producing liquid crystalline polymer systems. 

The measured crystallinity of a polymer has no absolute value and is critically dependent on the experimental technique used to determine it. An estimate of the crystallinity of a polymer can be made from DSC data assuming strict two-state behaviour. In this case the polymer is presumed to be composed of distinct, non-interacting amorphous and crystalline regions where reordering of the polymer structure only occurs at the melting temperature of the crystalline component. Despite the obvious limitations of this model, it is widely used in industry to determine the crystallinity of polymers. The crystallinity ) is calculated using... 

Many experimental techniques have been used to examine the detailed structure of perfluorinated polymeric membranes. These include transmission electron microscopy [23], small angle X-ray scattering [24], Infra Red spectroscopy [25,26], neutron diffraction [27], Nuclear Magnetic Resonance [26,28], mechanical and dielectric relaxation [25,29], X-ray diffraction, and transport measurements. All these methods show convincing evidence for the existence of two phases in the perfluorosulfonate and perfluorocarboxylate polymers. One phase has crystallinity and a structure close to that of polytetrafluoroethylene (PTFE), and the other is an aqueous phase containing ionic groups. 

Chapters 1 and 2 introduce new experimental techniques that provide new sets of relevant data for the study of the local and overall mobility of polymer chains. In Chapter 1, the development of two-dimensional infrared spectroscopy is described with a discussion of the mathematical principles, the description of the instrumental technique, and a detailed analysis of a few cases. In Chapter 2 the success of Fourier transform infrared polarization spectroscopy is shown for the study of segmental mobility in a polymer or a liquid-crystalline polymer under the influence of an external directional perturbation such as electric, electromagnetic, or mechanical forces. Industrial research laboratories should pay much attention to the information which can be acquired with this technique for technologically relevant polymeric materials. 

There is still considerable discussion about the existence of chain folding in semi-crystalline polymers." Using a Monte Carlo method, Flory and Yoon have shown " that adjacent re-entry could not reproduce the experimental results from polyethylene" and polypropylene" in the intermediate q range. An analytical computational technique, involving a model having a Gaussian distribution of inter-stem distances in the lamella, has been shown to fit these data" and can replicate the earlier Monte Carlo calculations. The root mean square, inter-stem distances derived from the fits are 22 A for polyethylene and 28 A for polypropylene. 

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