Polymer chain intramolecular structure

The cause of noninterpenetration in Vollmert s experiments was left up in the air because of the possibility of thermodynamic (and even steric) incompatibility. Braun (1976) endeavoured to circumvent this ambiguity by carrying out crosslinking reactions on identical polymer molecules. This was based upon the observation that 1,1-diphenylethylene in the presence of sodium metal forms radical anions that rapidly dimerize in quantitative yield. This reaction was applied to poly(l-phenyl-l-(4-vinylphenyl) ethylene-costyrene), which can in principle undergo both intramolecular and intermolecular reactions. Intramolecular reactions cause coil contraction, which is manifest by a decrease in the intrinsic viscosity of the polymer solutions. Intermolecular reactions stiffen the polymer chains, their structure... 

The investigation of structural dynamics of CP is particularly topical in connection with the establishment of correlation between local intramolecular mobility and the reactivity of chain fragments. It has been established that groups located in the most mobile parts of the polymer chain exhibit the greatest reactivity [48], The chemical heterogeneity in relationship to local mobility is particularly... 

The explanation proposed involved sequential inter- and intramolecular addition steps. The presence of cyclic structures within the polymer chain was soon confirmed by degradation experiments.106 However, these experiments did... 

A different type of microgels can be obtained by solution polymerization. Since an increase of dilution during crosslinking increases the probability of intramolecular crosslinking, the growing polymer chains in a highly dilute solution become intramolecularly crosslinked and their structure approaches that of the microgels formed within the micelles. 

Solid state 2H NMR parameters are almost exclusively governed by the quadrupole interaction with the electric field gradient (EFG) tensor at the deuteron site.1 8 The EFG is entirely intramolecular in nature. Thus molecular order and mobility are monitored through the orientation of individual C-2H bond directions. Therefore, 2H NMR is a powerful technique for studying local molecular motions. It enables us to discriminate different types of motions and their correlation times over a wide frequency range. Dynamics of numerous polymers has been examined by solid state 2H NMR.1 3,7,9 Dynamic information on polypeptides by NMR is however limited,10 26 although the main-chain secondary structures of polypeptides in the solid have been extensively evaluated by 13C and 15N CP/MAS NMR.27,28... 

The simulation of polymer chains attached at one end to an inert interface ("tails") Is described, using a combination of Monte-Carlo techniques and the RIS scheme. Four types of chains that exhibit different structural and geometrical characteristics are examined PE, POM, POE, and PDMS. The overall effects on the conformation of the attached chains arising from the presence of the interface are qualitatively similar. The chains are significantly extended, as measured by the mean square displacement, in the direction normal to the interface, but essentially unaffected parallel to the interface. A comparison Is made of intramolecular excluded volume with excluded volume arising from an impenetrable interface. It is shown that the two types of excluded volume exhibit qualitatively different effects on the conformation. 

A more serious factor that has direct regard to initial steps of mesophase formation in polymer solutions has to be assessed. That is the interaction between the molecules of LC polymer and of the solvent. The conformation of the macromolecule appears to be sensitive to the thermodynamic quality of the solvent, and this has a very pronounced effect on the mode of intramolecular structure formation. For instance, the folding of the chain in a bad solvent leads to a sharp rise in intramolecular orientational ordering of the side branches. This is manifest as an increase of optical... 

Hydrogen atoms in allylic position are favorite sites for hydroperoxidation of chains. So, this mechanism proceeds in the formation of lateral hydroperoxides, and not like for other polymers, in intramolecular peroxides. Rearrangement of chemical structures coming from ozonides are rapidly observed (Scheme 33). 

As displayed in the proposed scheme, each intramolecular transesterification randomly breaks the polymer chain. In this way, an attack on the polymer chain leads to a free residual polymer and a new randomized, modified polymer. Consequently, an original copolymer with a block-like structure would be converted to a randomized copolymer after undergoing n transesterifications [42,43]. 

Because atactic polymer has no ordered structure and shows only slight intramolecular interactions, the interactions between atactic polymers is the strongest (Fig. 10 a). The isotactic polymers may be stabilized by assuming the helix conformation reported for isotactic poly(methyl methacrylate)401. Nucleic add bases are situated outside the polymer chain so that they can form the complex, although the interaction is not so strong. On the other hand, the syndiotactic polymer may have a rod-like conformation that is supported by the low solubility of the polymer and by NMR spectra321. Tlierefoie, it is well understood that the complex formation ability of the syndiotactic polymers is very low. 

This article deals with some topics of the statistical physics of liquid-crystalline phase in the solutions of stiff chain macromolecules. These topics include the problem of the phase diagram for the liquid-crystalline transition in die solutions of completely stiff macromolecules (rigid rods) conditions of formation of the liquid-crystalline phase in the solutions ofsemiflexible macromolecules possibility of the intramolecular liquid-crystalline ordering in semiflexible macromolecules structure of intramolecular liquid crystals and dependence of die properties of the liquid-crystalline phase on the microstructure of the polymer chain. 

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