Influence of Chain End and Molecular Weight on Molecular Motion of Polystyrene, Revealed by the ESR Selective Spin-Label Method

Miwa, Yohei; Tanase, Takayuki; Yamamoto, Katsuhiro; Sakaguchi, Masato; Sakai, Masahiro; Shimada, Shigetaka

doi:10.1021/ma030026l

Cited by 34 publications

(83 citation statements)

References 36 publications

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“…As an example, Kajiyama et al [6] reported that polymer surface enriched with segregated chain ends exhibited higher molecular mobility, in other words, lower glass-rubber transition temperature (T g ) as evidenced by atomic force measurement. Miwa et al [7] spin-labeled selectively at particular sites and detected the molecular mobility of each site. Figure 8.1 shows chemical structures of spin-labeled polystyrene (PS) at the inside and the end of chain segments.…”

Section: Glass-rubber Transition Detected By the Spin Label Methods Fomentioning

confidence: 99%

“…In general, the splitting between Chemical structure of spin-labeled PS at inside (left) and end (right) of chain. The figure is adapted from [7] with permission from the American Chemical Society the outer-most lines of the main triplet spectrum due to the nitrogen hyperfine coupling becomes narrower with an increase in the mobility of the radicals because of the motional averaging of the anisotropy. The extreme separation width shown with arrows in Fig.…”

Section: Glass-rubber Transition Detected By the Spin Label Methods Fomentioning

confidence: 99%

“…Separation between arrows shows extreme separation width. The figure is adapted from [7] with permission from the American Chemical Society Fig. 8.3 Temperature dependence of extreme separation width for spin-labeled PS at chain end (solid) and at inside site (open).…”

Section: Glass-rubber Transition Detected By the Spin Label Methods Fomentioning

confidence: 99%

“…8.3 Temperature dependence of extreme separation width for spin-labeled PS at chain end (solid) and at inside site (open). The figure is adapted from [7] with permission from the American Chemical Society than that of the spin-labeled PS at the inside site. This is caused by the large free volume at the chain end in comparison with that at the inside of the chain.…”

Section: Glass-rubber Transition Detected By the Spin Label Methods Fomentioning

confidence: 99%

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Spin Labeling and Molecular Dynamics

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Principles and Applications of ESR Spectroscopy

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Measurements of temperature dependent ESR spectra of spin labels trapped in the polymer matrices is very effective for the evaluation of molecular mobility (molecular motion) of polymer chains. We can characterize the molecular motion of the particular sites in different region by the ESR method. It is possible to detect the mobility of polymer material at the segment or atomic level. ESR studies help to relate the features of the nanometer scale to macroscopic properties of the polymer materials. We present examples of spin labeling studies in the polymer science to help readers new to the field understand how and for what areas the method is effective. In the first part, we give a simple review of the spin labeling method and present applications in the polymer physics related to relaxation phenomena in various systems. In the second part applications to biopolymer system are introduced to help the clarification of various mechanisms of bio-membranes. IntroductionIn this chapter, we deal with applications of spin labeling to molecular dynamics in polymer science. The radical species in these studies are stable so-called spin labels and spin probes. The success of these studies has made the ESR method increasingly popular for polymer investigations. We can characterize the molecular motion and the structure of the polymer chain in a wide temperature range including that above the melting temperature. The ESR method is effective for the characterization of the heterogeneity in mobility and structure of polymer materials as mentioned in Chapter 7. The heterogeneity is one of the most important features in polymer materials including biopolymers and related to the broad distribution of relaxation time of physical properties such as stress and dielectric relaxations, creep etc. Selective spin labeling is very effective for the detection of the molecular motion in the various sites and regions of the polymer systems. We can for example selectively observe the molecular motion of the particular sites in a chain and particular chains in the copolymer and blend systems.In this chapter we present typical applications of the spin labeling method to polymer physics and biopolymer systems.

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Section: Glass-rubber Transition Detected By the Spin Label Methods Fomentioning

confidence: 99%

Section: Glass-rubber Transition Detected By the Spin Label Methods Fomentioning

confidence: 99%

Section: Glass-rubber Transition Detected By the Spin Label Methods Fomentioning

confidence: 99%

Section: Glass-rubber Transition Detected By the Spin Label Methods Fomentioning

confidence: 99%

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Spin Labeling and Molecular Dynamics

Lund

Shiotani

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2010

Principles and Applications of ESR Spectroscopy

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“…Second, as discussed in Section 4.3, the AgNWs act as heterogeneous nucleating sites and lead to shorter polymer chains. As a result, the segmental mobility of the chains increases accounting for lower T g [64]. …”

Section: Differential Scanning Calorimetrymentioning

confidence: 99%

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2016

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The present work demonstrates a novel technique for dispersing nanofillers in a thermoplastic polymer, where polymerization and dispersion of the nanofillers occur simultaneously via dynamic emulsion polycondensation at ambient temperature. The composite is manufactured in the form of a uniform powder, which can then be molded into desired shape by melting or sintering. The technique is demonstrated for Ag nanowire / Nylon 66 composites. In this demonstration, Ag nanowires are synthesized by the polyol process. Polyvinylprrolidone (PVP) is used to functionalize the Ag nanowires. Nanocomposites with varying Ag content are prepared and investigated. The nanowires are found to be monodispersed and hydrogen-bonded to the Nylon 66 matrix through PVP. Glass transition temperature of the composites decreases from 61 to 48 °C with Ag weight fraction increasing from 0 to 6.47%. The depression of the glass transition temperature is owed to the plasticizer effect as well as heterogeneous nucleation effect of the nanowires for polymerization leading to shorter chain length.

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Characterization of Polymers

Pethrick

2004

Encyclopedia of Polymer Science and Technology

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In order to effectively use polymeric materials, it is important to understand what factors influence their physical and chemical properties. This article attempts to develop a framework for the systematic discussion of the characteristics of polymeric materials in terms of the methods used in their synthesis, the dominant nature of the organization or lack of it in the solids state, and their process ability. Many properties of a polymer are influenced by the length or the polymer chain or its size, and techniques which allow quantification of these properties are very important in defining the nature of a polymer. The final physical properties of a polymer can be influenced by the nature of the structure developed on formation of a solid, and relating physical properties to morphology is often required in order to understand the subtle effects which can be observed and to make polymeric materials commercially interesting for a wide range of applications.

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Influence of Chain End and Molecular Weight on Molecular Motion of Polystyrene, Revealed by the ESR Selective Spin-Label Method

Cited by 34 publications

References 36 publications

Spin Labeling and Molecular Dynamics

Spin Labeling and Molecular Dynamics

Ag-Nylon Nanocomposites by Dynamic Emulsion Polycondensation

Characterization of Polymers

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