Deuterated polymer

The main experimental techniques used to study the failure processes at the scale of a chain have involved the use of deuterated polymers, particularly copolymers, at the interface and the measurement of the amounts of the deuterated copolymers at each of the fracture surfaces. The presence and quantity of the deuterated copolymer has typically been measured using forward recoil ion scattering (FRES) or secondary ion mass spectroscopy (SIMS). The technique was originally used in a study of the effects of placing polystyrene-polymethyl methacrylate (PS-PMMA) block copolymers of total molecular weight of 200,000 Da at an interface between polyphenylene ether (PPE or PPO) and PMMA copolymers [1]. The PS block is miscible in the PPE. The use of copolymers where just the PS block was deuterated and copolymers where just the PMMA block was deuterated showed that, when the interface was fractured, the copolymer molecules all broke close to their junction points The basic idea of this technique is shown in Fig, I. 

Significant experimental support for these relations and the minor chain repta-tion model has been obtained from neutron reflection and SIMS experiments using specially deuterated polymers... 

I(q) is the intensity at wave vector q, (bjjr-bp) is a contrast factor arising from the difference in scattering lengths of deuterated and protonated species, M is molecular weight of the deuterated polymer, c is concentration in gm/ml, S(q) is a particle scattering factor, and A contains machine constants, detector efficiency, and other fixed quantities. For the purpose of the current study, S(q) is the quantity of significance, and it is given by... 

This highly sophisticated investigation has been superseded by C spectroscopy, which is mote sensitive to the stereochemical envirorunent and does not requite the preparation of deuterated polymers. C NMR analysis of steric purity and sequence distribution can, therefore, be directly carried out on commercially available polymers. Thus, any doubt regarding the previous conclusions about laboratory-produced polymers obtained under necessarily different... 

This model had been proposed by Fowells et al. (17) on the basis of NMR measurements of partially deuterated polymers prepared in the system THF/Li, and it was applied by Fisher and Szwarc (3o) and Sigwalt and coworkers (31,32)to the polymerization of 2-vinyl pyridine. 

The CP experiments on polymer blend systems, using a mixture of two polymers in which one is deuterated and another is protonated, have been carried out in order to elucidate their miscibility. This information is given by whether protons in the protonated polymer are cross-polarized to deute-rons of the other deuterated polymer or not. These studies show that effective CP transfer may be limited to about 10 A. In the... 

In analyzing the spectrum of a polymer we do not, of course, limit ourselves to the study of a single specimen. We have already noted the significant information which can be obtained by studying oriented samples as well as deuterated polymers, when possible. In this section we will consider briefly how the study of other kinds of specimens adds to our knowledge of the origin of bands. 

While it cannot be said that all of the assignments in the spectrum of PVdC are satisfactorily established, it would seem that the majority are. The important ones from the standpoint of the chain structure are the v (CC12) modes, and the present evidence on their assignment supports the correctness of the Fuller structure. A study of a partially deuterated polymer might be of further assistance in this respect. What is also clearly needed is a more detailed study of the skeletal modes to be expected from the proposed chain structure, since these clearly contribute significantly to the spectrum. Finally, knowledge of the crystal structure might permit more to be said on the nature of interchain interactions and their effect on the spectrum. 

Since its introduction in the early 1970s, the small angle neutron scattering (SANS) method has had a substantial impact on polymer research. When used with partially deuterated polymers, SANS permits a close monitoring of macro-molecular conformations in polymer solutions, melts, and blend mixtures. This advantage has made it a unique tool for the understanding of the morphology of polymer materials and of the relationship between their structures and physical properties. 

Consider a polymer solution consisting of protonated and deuterated polymers (concentrations CH and CD respectively) that have the same degree of polymerization N. The scattered intensity is proportional to the structure factors for the polymer-polymer correlations SHH(Q), SDD(Q), SHIj(Q), polymer-solvent correlations SpS(Q), and solvent-solvent correlations Sss(Q). The protonated, deuterated and solvent molecule scattering lengths are called aH, aD and as and ap is the average polymer scattering length. The scattered intensity can be expressed in terms of an absolute cross section as ... 

Stuart Cooper It would be a mistake, just as we avoid trying to teach too much math to our students, to try to teach them too much polymer chemistry. It s healthy and good to see a rekindling of interest in polymer chemistry from chemistry departments and polymer science departments at various universities around the country. Some of the most beautiful collaborations are indeed those where you see someone—maybe in an industrial laboratory or a university laboratory—synthesizing tailor-made materials, whether it be a starblock polymer or deuterated polymers, for collaboration with someone in the solid-state area who may be in a chemical engineering de-... 

Surface characterization regarding other electron spectroscopies. To evidence specific attributes of HREELS to be compared to ESCA (XPS), UPS or AES ones, we chose to present (Figure 3) spectra recorded from polystyrenes (2). These thin film samples were made from normal and fully deuterated polymers. Immediately, it appears that HREELS is really capable of adding a new and unique dimension to electron surface analyses as ... 

Since for each experimental point a new specimen is required, the data in Fig. 17 were obtained with a commercial polystyrene sample, available in larger quantities than the anionic and deuterated polymers used for the SANS experiments. The curves in Fig. 17 suggest the following expression for the tensile stress ... 

Molecular weights of polymers from styrenes deuterated in the side chain are the same as those of polystyrene prepared under the same conditions [78], and this is true also of polymers from ethylene and deuteroethylene [79]. If hydride ion transfer were rate determining an isotope effect would be expected with higher molecular weights in the deuterated polymers. The rate determining step would therefore appear to be coordination of monomer followed either by rapid transfer or insertion into the polymer chain. 

For all these specialty polymers, deuterium can be used as a label on one or the other monomer. Deuterium labeling allows the use of techniques based on ion detection such as forward recoil spectrometry (FRES), nuclear reaction analysis (NRA) or secondary ion mass spectrometry (SIMS). If a high-resolution depth profile of the interfacial region is needed, neutron reflectivity can also be used. The main drawback of that approach is the cost of the deuterated polymers while deuterated styrene and methyl methacrylate are expensive but commercially available, other monomers need to be synthesized and the cost can be quite prohibitive. 

A second, seemingly less artificial, method would be to add a certain amount of block copolymer to one of the homopolymers and let it diffuse to the interface. This method has not been used to prepare fracture samples with deuterium-labeled block copolymers for several practical reasons Dissolving 5% of copolymer in a sheet of 50x100x2 mm dimensions requires 500 mg of deuterated polymer while a similar interface can be obtained by spin-casting with approximately 5 mg. The time involved to achieve true diffusional equilibrium over millimeter-scale thicknesses is prohibitively long at typical welding temperatures and the presence of a background concentration of deuterium-labeled polymer... 

Constant-time imaging of H in solids has been applied in combination with MAS for line narrowing [Cor3, Cor4]. The images were recorded for a dynamically stressed poly(isoprene) phantom and of poly(butadiene) in two poly(butadiene)/poly(styrene) blends. Spectroscopic MAS imaging has also been tested on deuterated polymers to probe differences in molecular moblity from the lineshape of the rotary-echo envelope... 

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