Polymer structure, phenyl-substituted

Many of the unique properties of silicone oils are associated with the surface effects of dimethylsiloxanes. Silicones impart water repellency to fabrics, act as antifoaming agents (447), as release liners for adhesive labels, and as polishes and waxes (448). Dimethylsilicone oils can spread onto many solid and liquid surfaces to form films of molecular dimensions (449,450). This phenomenon is greatly affected by even small changes in the chemical structure of siloxane in the siloxane polymer. Increasing the size of the alkyl substituent from methyl to ethyl dramatically reduces the film-forming ability of the polymer (449). Phenyl-substituted silicones are spread onto water or solid surfaces more slowly than PDMS (451). 

Samples of the poly(dialkylphosphazenes) 1 and 2 displayed X-ray powder diffraction patterns characteristic of crystalline regions in the materials. The peaks in the diffraction pattern of 1 were of lower amplitude and greater angular breadth than those of 2. These data indicate that poly(diethylphosphazene) (2) is highly crystalline while poly(dimethyl-phosphazene) (1) is more amorphous with smaller crystalline zones. This high degree of crystallinity is probably responsible for the insolubility of 2 as noted above. All of the phenyl substituted polymers 3-6 were found to be quite amorphous in the X-ray diffraction studies, a result that is further evidence for an atactic structure of the poly(alkylphenylphosphazenes) 3 and 4 and for a random substitution pattern in the copolymers 5 and 6. 

Z. Chen, N.H.S. Lee, W. Huang, Y. Xu, and Y. Cao, New phenyl-substituted PPY derivatives for polymer light-emitting diodes — synthesis, characterization and structure-property relationship study, Macromolecules, 36 1009-1020, 2003. 

This disilaborane was an unexpected co-product in the synthesis of decaborane-alkylamine polymers. The Si2Bio cluster core consists of a distorted icosahedron in which the two silicon atoms occupy adjacent positions. The Si-Si interatomic distance is 2.308(2) A, which is slightly less than the Si-Si distance in organodisilanes (2.35 A) and the Si-B distances [2.017(3) to 2.116(3) A] are very close to the sum of the covalent radii of the two atoms (2.07 A). Further derivatives with disilaborane cluster geometry are known for the phenyl substituted compounds l,2-Ph2-doso-l,2-Si2B1oH1o and l-Me-2-Ph-doso-l,2-Si2BioHi0 [6, 7]. In addition to these disila-doso-dodecaborane clusters one example with two different group 14 elements as a part of the cluster core is known. In Scheme 3.3-2 the synthesis of this sila-stanna-doso-dodecaborate is shown. The structure of this heteroborate was determined in the solid state and the Si-Sn distance is 2.608(4) A (Scheme 3.3-2) [8]. 

Polymer Structure. The reaction studied here is summarized in Equation 21. As shown in the experimental section, it is possible to prepare these polymers at various degrees of substitution. As the degree of substitution increases, the ratios of the infrared C=0/0H absorption peaks and the phenyl/aliphatic C-H absorption peaks increase in a linear manner (Table I). (It would be possible to determine the degree of substitution from such calibrated curves.) At the same time, the intensity of the OH band in the NMR spectra diminishes while a strong set of peaks due to the phenyl group forms. Elemental nitrogen analysis values for the modified polymers agree closely with the calculated values. In addition, the infrared spectra show the necessary carbamate N-H bands. These factors enable us to have confidence that the polymer structure is as shown in Equation 21. 

The present study reports the synthesis, characterization and thermal reactions of phenyl and carbomethoxy substituted norbornenyl imides. These substrates were designed to model the reactive end-caps of the PMR-15 resin and allow an assessment of the effect that conjugating substituents would have on the high temperature cure of such systems. The effect of these substituents on both monomer isomerization and polymerization is reported and a possible use of the phenyl substituent as a probe of polymer structure is suggested. 

It is clear that any kind of addition polymerization of the norbornenyl double bond will benefit from the electronic stabilization provided by a conjugating substituent. A simple radical addition process such as is known for both styrene and acrylate monomers may be a reasonable analogy to our system. Whether this effect alone is enough to account for our observations is not clear. A possible additional effect, at least in the case of the phenyl substituted monomers, is suggested below as part of our work on polymer structure. 

Having established the effect of substitution on the rates of both monomer isomerization and polymerization, we addressed the question of polymer structure. Specifically, are norbornenyl imide units incorporated into the fully cured polymer with their norbornyl rings intact If so, does the polymer also reflect the equilibrium ratio of exo and endo ring fused monomers For our parent monomers, PN and PX, this question has been unanswerable. We have not found any direct probe that allows an unambiguous assessment of specific substructures within the cured polymer. We do, however, have some evidence bearing on this question for the phenyl substituted monomer. This evidence is attributable in part to our discovery of an unexpected side-reaction in the cure of the phenyl substituted monomer, and in part to the presence of a unique NMR diagnostic for phenyl substituted, endo norbornyl N-phenyl imides. Both of these results are detailed below. 

Methyl- or phenyl-substituted silsesquioxanes obtained by hydrolysis and condensation of RSi(OR )3 or RSiCb (R = Me, Ph) were studied extensively by several groups75. MeSi— and PhSi— units are the classical components of silicones. The molecular weight and structure of methyl- or phenyl-substituted silsesquioxane polymers, and thus their physical properties (solubility, mechanical properties, etc.), depend very much on the reaction conditions. Since silicones are not the topic of this article, the interested reader is referred to the relevant literature. 

In going from benzene to 3-carotene (the second structure), the Y value increases by more than three orders of magnitude showing the importance of increase in the effective conjugation length. The third structure exhibits N-phenyl substitution in the benzimidazole type structures to introduce a two dimensional conjugation. The last structure, an organometallic polymer, has also been measured in the solution phase. Because of the resonance condition encountered, the Y value is.complex. 

The conformational structures of polysilane main chains at the macro-and microscopic levels are controllable by suitable choice of the side chain structures. Similarly, it is also the side chain which controls the optoelectronic properties by effecting the optical band gap. In the case of phenyl-substituted polysilanes, electronic interaction between the delocalized Si chain cr-bonding orbitals and the it-orbitals of the aryl groups causes a dramatic modification of both the band gap and conformational properties [61,83]. These aryl-containing polysilanes may be potential candidates for applications in a molecular-based chiroptical switch and memory in the UV/visible region. On the other hand, the precise control of helical polymers is now a subject of great interest and importance, due to the tech-... 

We have studied the thermochromism of fluorescence and show this behavior to be consistent with the rotational isomeric state model previously proposed to explain solution thermochromism in absorption (9,10). Weak, structured phosphorescence is observed from all polymers studied. The contrast between the structured phosphorescence and the narrow fluorescence is interpreted as evidence that the triplet state is the immediate precursor to photochemistry. Finally, the change in the fluorescence character in the aryl series on going from phenyl substitution to naphthyl substitution suggests a change in the nature of the transition from one involving mixed side chain-backbone states in the phenyl case to one which is primarily side chain-like for naphthyl-substituted polysilylenes. 

Polyglycine, H(-CO-CH2-NH)n-H, is the simplest polypeptide. It has two solid state structures. Form I consists of chains of polymer that are hydrogen-bonded into two-dimensional sheets. This form (including selectively deuterated isotopomers) has been studied by INS [53-55]. The spectra were interpreted similarly to those of N-methylacetamide. Reexamination of the spectra with periodic-DFT calculations is necessary. Acetanilide, C6H5-NH-C(=0)-CH3, forms hydrogen-bonded chains similar to N-methylacetamide and as such is a potential model for phenyl substituted peptides. However, the interest in acetanilide is that the... 

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