Poly fine structure

Nakase, Y., Kurijama, I. and Odajima, A. Analysis of the Fine Structure of Poly(Oxyme-thylene) Prepared by Radiation-Induced Polymerization in the Solid State. Vol. 65, pp. 79-134. 

Organic molecules having many degenerate orbitals 187 Poly(m-phenylenecarbenes) 194 Poly(acetylenes) and other conjugated polymers 197 Analytical methods and characterization 201 Epr fine structure 201... 

Figure 1. Morphology of sequential IPNs. (a) Crois-poly (ethyl acrylate)-m/er-crojs-polystyrene, showing typical cellular structure and a fine structure within the cell walls, (b) Cross-poly (ethyl acrylate)-/ /cr-cross-polystyrene-s/a/-(methyl methacrylate), showing smaller domain structure. PEA structure stained with OsO. (Reproduced from ref. 5. Copyright 1972 American Chemical Society.)...

The process for preparing linear poly-p-xylylenes by pyrolytic polymerization of di-p-xylylenes has been extended to include the formation of p-xylylene copolymers. Pyrolysis of mono-substituted di-p-xylylenes or of mixtures of substituted di-p-xylylenes results in formation of two or more p-xylylene species. Copolymerization is effected by deposition polymerization on surfaces at a temperature below the threshold condensation temperature of at least two of the reactive intermediates. Random copolymers are produced. Molecular weight of polymers produced by this process can be controlled by deposition temperature and by addition of mercaptans. Unique capabilities of vapor deposition polymerization include the encapsulation of particulate materials, the ability to replicate very fine structural details, and the ability of the monomers to penetrate crevices and deposit polymer in otherwise difficultly accessible structural configurations. 

Abbreviations BCC. body centered cubic DOS. density of states ESR. electron spin resonance HX.AI S, extended X-ray absorption fine structure F CC. face centered cubic (a crystal structure). FID, free induction decay FT, Fourier transform FWHM, full width at half maximum HCP, hexagonal close packed HOMO, highest occupied molecular orbital IR, Infrared or infrared spectroscopy LDOS, local density of states LUMO, lowest unoccupied molecular orbital MAS. magic angle spinning NMR. nuclear magnetic resonance PVP. poly(vinyl pyrrolidone) RF. Radiofrequency RT, room temperature SEDOR, spin echo double resonance Sf, sedor fraction SMSI, strong metal-support interaction TEM. transmission electron microscopy TOSS, total suppression of sidebands. 

Recently, Schulten et al.(42,45) have proposed a new model for humic substances in soil based partly on NMR data but mostly on pyrolysis studies. This model proposes that the core structure of humic acids is alkyl-aromatic and alkyl-poly-aromatic. The lack of oxygen functionality and the fact that pyrolysis data for highly oxygenated humic acids may be biased in favor of more volatile alkyl-aromatics dictates that the model needs extreme revision or is simply incorrect. The recent studies of Saiz-Jimenez et d, (44) and Hatcher et al.(5 ) appear to refute the original model presented by Schulten et al.( 7) The NMR data appears to be in accord with the model presented by Schulten et al.( 7), however, NMR does not represent carbon structures with specific molecular-level detail. It only provides average information with a sometimes added benefit of added fine structure. 

The structure of the copolymer, poly(di-n-butylstannane-co-methylphenylsilane) with a Sn Si ratio of 1 3 was determined with X-ray absorption fine-structure spectroscopy (EXAES) and X-ray absorption near-edge spectroscopy (XANES). The bond distances of Sn-Sn (2.82 A), Sn-Si (2.58 A), and Sn-C (2.15 A) in the copolymer were comparable with the cyclooligostannylsilane, illustrated in Eigure 3.8.1. 

Figure 8 is the phosphorescence spectrum taken from a glassy solution of poly(n-propyl methyl silylene) in methyl cyclopentane at 89°K. This emission is similar in width to the film emission, as are the solution spectra of the other polymers. Again delayed fluorescence is evident but the sharp vibrational fine structure is lost. The solution and film spectra are not expected to be comparable since they represent conformational equilibria (at room temperature for film and the Tg of 3-methylpentane for the solutions). 

FIGURE 2.7 Fine-structured poly(pyrrole) film formed on the ionic liquid surface using 10 ms voltage pulses. (Source Dr. Jenny Pringle, Monash University, Australia.)... 

Mechanistic studies by Haynes et al. demonstrated that the same catalytic cycle operates for both homogeneous and ionically attached systems [107,108]. Reaction of quaternized poly(4-vinylpyridine-co-styrene-co-divinylbenzene) with [Rh(CO)2I]2 generated the ionically attached Rh(I) complex [Rh(CO)2I2] (Scheme 12). IR spectroscopy revealed v(CO) bands of the supported cis-[Rh(CO)2I2] at frequencies close to those observed for this complex in solution. The structure of the supported complex was also confirmed by extended X-ray absorption fine structure (EXAFS) measurements, which showed that the geometry is very similar to that determined by X-ray crystallography for salts of [Rh(CO)2I2] -... 

Quantitative measurement shows about 11% of the monomer units to be inverted. The principal spectrum shows splitting into mm, mr, and rr triad resonances with some pentad fine structure. The polymer is nearly atactic. Assignment of inversion "defect" resonances is made easier by reference to spectrum (b), which is that of poly (vinyl fluoride) prepared by the following route (17) ... 

Microstructures of Poly(chlorofluoroethylene)s The carbon-13 NMR spectrum of PVCF consists of a —CH2— resonance at 54.1 ppm and a —CFC1— resonance at 108.8 ppm. There is no splitting of these lines due to tacticity, nor are there any other resonances to indicate the presence of regioirregular monomer sequences. However the polymer is stereoirregular, as shown by the fluorine-19 NMR spectrum in Figure 1. There are three principal resonances spread by 3 ppm owing to triad stereosequences, with some pentad fine structure which is barely resolved. 

Recently, high resolution solution and solid state 29Si NMR studies have been conducted on the polysilanes (RR Si)w124 127. It is obvious that this technique will be a powerful method for determining the microstructure of these polymers. Figure 12 shows a comparison between the 29SiNMR spectrum of poly(methyl-n-hexylsilane) and poly(di-n-hexylsilane)124. In the former case the effects of tacticity can be seen in the fine structure of the spectrum whereas in the latter case for which this is impossible only a single peak is observed. 

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