Dynamics of the "Strong" Polymer of n-Lauryl Methacrylate below and above the Glass Transition

Floudas, G.; Placke, P.; Štěpánek, Petr; Brown, Wyn; Fytas, G.; Ngai, K. L.

doi:10.1021/ma00124a015

Cited by 83 publications

(84 citation statements)

References 9 publications

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“…3, were obtained for the activation energy of 27 kJ/mol. Distinct difference between theoretical and experimental value of T 1ρ at minimum may be due to temperature dependence of parameter describing distribution of correlation times and/or the increase in number of ethylene groups involved in the motion when temperature rises up, which was observed in other polymers [11,[16][17][18]. Motional behavior of the studied copolymer observed in NMR is reflected in dielectric and mechanical studies.…”

Section: Resultsmentioning

confidence: 78%

Molecular Dynamics in Cyclic Olefin Copolymer

et al. 2005

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Nuclear magnetic resonance, broadband dielectric spectroscopy and dynamic-mechanical thermal analysis were employed to study molecular dynamics of ethylene-norbornene copolymer. The analysis of experimental data indicates existence of three motional processes denoted as α, β, and γ in order of decreasing temperature. The α relaxation is related to the dynamic glass transition, while the β relaxation, observed only for the untreated sample, is assigned to short range segmental motions involving norbornene units. The γ relaxation is due to very local motions of ethylene units e.g. trans-gauche isomerization, similar to those responsible for γ relaxation in polyethylene. The rate of motion accountable for γ process, follows the Vogel-Fulcher-Tammann equation, similarly to α transition, indicating cooperative nature of the motion.

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Section: Resultsmentioning

confidence: 78%

Molecular Dynamics in Cyclic Olefin Copolymer

et al. 2005

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“…that the changes in the osmotic modulus are the Figure 4a shows the relaxation rate for the cluster mode as a function of q 2 in the PLMA melt at 60ЊC illustrating its apparent diffusive character. At temperatures above about 5ЊC, the density fluctuations which formed the subject of the prior communication, 6 already lie outside of the experimental time window. Figure 4b shows the scattering vector dependence of the inverse scattered intensity, taken up with a low intensity laser and averaged over 30 min/run, for the cluster mode in the PLMA melt at 60ЊC, where the intensity of this mode has been obtained by apportioning the total intensity using the relative amplitude of the relevant mode.…”

Section: Cluster Modementioning

confidence: 95%

“…The first part of this work describes an invesponent as a function of PLMA concentration in the solutions and also a determination of the tigation of melt PLMA using dielectric spectroscopy and depolarized light scattering. 6 There it characteristic dimensions as a function of solvent content. was observed that the main process is a mixed ab-relaxation which could be studied over a broad temperature range.…”

Section: Introductionmentioning

confidence: 99%

Dynamic light scattering of poly(n-laurylmethacrylate) in the melt and in concentrated ethyl acetate solutions

Brown

Štěpánek

1997

J. Polym. Sci. B Polym. Phys.

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Dynamic light‐scattering measurements have been made on the “soft” polymer: poly(n‐laurylmethacrylate) (PLMA) in solution in ethyl acetate over the concentration range 0.1 < C < 0.9 g/mL as well as melt PLMA. With the concentrated solutions, the hydrodynamic screening length (ξh) scales with an exponent of −0.7 below C ≈ 0.3 g/mL. Importantly, ξh decreases above 0.3 g/mL, and the concentration dependence increases strongly above this concentration. The latter contrasts with the behavior in a variety of well‐studied poly(styrene) solutions, which are inevitably investigated close to the glass point, and for which there is a pronounced increase of ξh over the same concentration range. In PLMA solutions, the decrease in ξh parallels the behavior of the static screening length (ξs) which has been observed in other flexible polymer systems. Dynamic “clusters” (also termed “long‐range density fluctuations”) contribute a large part of the scattered intensity above the concentration 0.6 g/mL and also in melt PLMA which contrasts with poly(styrene) systems in which they are absent. In common with the clusters recently observed in another polymeric melt, poly(methyl‐p‐tolylsiloxane) (ref. 9) this component is diffusive. While, however, in the latter system the clusters “melt out” at 90°C, we find in the well‐matured PLMA systems that the cluster amplitude is temperature‐independent (within the temperature‐time range studied) in the solutions up to at least 80°C and up to at least 150°C in the melt, which were the highest temperatures examined. The clusters in the PLMA systems have a correlation length of the magnitude 65 nm in the melt, whereas in the solutions this dimension varies between 73 nm at 0.9 g/mL to 126 nm at 0.7 g/mL. In PLMA the clusters are presumed to arise from local segregation owing to the large paraffinic side groups on the chain. © 1997 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 35: 1013–1024, 1997

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“…The estimated nanodomain size is compared with the size of dynamic heterogeneities estimated independently from calorimetric data for the polyethylene-like glass transition using the fluctuation approach. C = 10) was investigated by PCS and other methods [31,32] in order to compare the properties with those of the a process in the lower members. More recently, the development of the polyethylene-like glass transition (a PE ) with side-chain length was systematically investigated.…”

Section: Introductionmentioning

confidence: 99%