Poly segmental mobility

In the absence of solvent, the influence of the surface on the segmental mobility can be deduced by measuring the temperature dependence of the spectral line shape in the presence and absence of the surface. The temperature dependence of bulk poly(vinyl acetate) is shown in Figure 3, and of bulk polystyrene... 

The difference in f3C-Tj between polymers with different tacticities but the same chemical structure results not only from differences in the chain segmental motion between stereoregular polymers or sequences but also from differences in preferred conformations between the stereoregular polymers or sequences which lead to different average distances for the interaction of a carbon with a proton of a neighbouring monomeric unit.298 The solvent dependence of l3C-T for stereoregular PMMAs has been explained by the solvent-dependent conformation of the polymer chain.299-301 In the case of H-Tj the mechanism of relaxation is rather complicated and the observed T cannot be directly related to the segmental mobility of the polymer chains. However, the H-T] values of poly (alkyl methacrylate )s were found to be parallel with the values, i.e. the Tx of the protons in the isotactic poly-... 

NMR-studies indicate a reduced segmental mobility and higher order parameter for the central hydrocarbon fragments of bola-surfactants [437] compared to the tail ends of the corresponding monomers. The differences however are less pronounced as for oligomeric poly soaps [68, 69],... 

Many polymers are themselves brittle at room temperature. For these polymers to become more pUable, additives called plasticizers that allow segmental mobility, and consequently segmental flexibility, are added. For syn-tiietic pol)miers such as poly(vinyl chloride) (PVC) and polystyrene (Figure 13), plasticizers are added that allow tiie polymers to be flexible. 

It should be expected that the influence of the chain segment mobility is most pronounced when the photochrome groups are inserted into a semirigid polymer backbone instead of being attached as mobile side groups in copolymers. Therefore, polyesters have been prepared by condensation of bis-hydroxymethyl-spirobenzopyrans with bisacid dichlorides.followed by polyesterification with bisphenol-A43,46). Thus, a photo-chromic poly(bisphenol-A-pimelate) (polyester XI) of the following formula was obtained. 

The thermotropic behavior of both the isotactic and syndiotactic poly n-[4 -(4"-methoxyphenyl)phenoxy]alkyl methacrylate s is summarized in Table 11. All of the tactic polymers crystallize. With the exception of poly 2-[4 -(4"-methoxyphe-nyl)phenoxy]ethyl methacrylate] (n=2), the melting temperature of the isotactic polymers is almost independent of the spacer length. In contrast, the syndiotactic polymers melt with a large odd-even alternation. However, only the syndiotactic polymers with at least four carbons in the spacer exhibit an enantiotropic smectic mesophase, which occurs over only a very narrow temperature range. The greater order of the isotactic polymers is evidently due to the greater segmental mobility of isotactic versus syndiotactic polymethacrylate backbones [246, 247]. 

In the case of H-Ti the mechanism of relaxation is rather complicated and the observed Tj cannot be directly related to the segmental mobility of pdymer. However, the H-T s of pdy(alkyl methaciylate)s were found to be parallel with C-Ti s namely, the T of the protons in isotactic pdymer was alw s longer than that of the comparable protons in syndiotactic polymer. The study of the H-T in partially deuterated and undeuterated poly(methj4 methacrylate)s indicated that the T s of the protons in the side chain groups were mainly controlled by the segmental motion of the polymer chain and that the longer Tj s of side chain protons in isotactic polymer were due to the greater mobility of the pdymer chain compared with the syndiotactic one. ... 

RUG Ru, G. and Feng, J., Effects of end groups on phase transition and segmental mobility of poly(A -isopropylacrylamide) chains in D2O, J. Polym. Sci. Part B Polym. Phys., 49, 749, 2011. 

Johansson A, Tegenfeldt J (1996) Segmental mobility in complexes of Pb(Cp3S03)(2) and poly(ethylene oxide) studied by NMR spectroscopy. J Chem Phys 104(13) ... 

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