2011
DOI: 10.1021/ma2000042
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Evolution of the Environment of Guest Molecules in Dynamically Heterogeneous Matrices of Poly(ethyl methacrylate) and Poly(n-butyl methacrylate) Far below Tg

Abstract: Photoinduced cis–trans isomerization has been used to measure the lifetime of structural heterogeneities in the matrices of poly(ethyl methacrylate) (PEMA) and poly(n-butyl methacrylate) (PnBMA) far below T g. Nonequilibrium distribution of probe molecules over their environments was formed by a partial trans → cis isomerization. To monitor the equilibration process, the back-isomerization was started after different delay times. The change in quantum yield of back-isomerization with delay time is interpreted … Show more

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Cited by 2 publications
(4 citation statements)
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“…The experimental technique has been described in detail elsewhere. , Here, basic details only are given. PEMA ( M w = 515 000 by GPC, T g = 336 K) and P n BMA ( M w = 337 000 by GPC, T g = 288 K) were purchased from Aldrich and P n HexMA (Approx.…”
Section: Experimental Methodsmentioning
confidence: 99%
“…The experimental technique has been described in detail elsewhere. , Here, basic details only are given. PEMA ( M w = 515 000 by GPC, T g = 336 K) and P n BMA ( M w = 337 000 by GPC, T g = 288 K) were purchased from Aldrich and P n HexMA (Approx.…”
Section: Experimental Methodsmentioning
confidence: 99%
“…The cistrans thermoisomerization is accounted for by the relaxation rates k 1 (inverse of the cis isomer lifetime t c1 ) and k 2 (inverse of the cis isomer lifetime t c2 ), which are applicable to different segments of the chromophore population that exhibit different interactions with the surrounding polymer matrix (eqn (1) for each of these fractions is solved separately). 16,17 G(O 0 -O) is the probability for the molecules to rotate from O 0 to O in the process of the cistrans thermal recovery and is assumed to be applicable to both the aforementioned fractions of the chromophore population.…”
Section: Theory and Calculationsmentioning
confidence: 99%
“…The former (k 1 ) is attributed to a fast non-thermally driven cistrans isomerization process, explained by a local structural relaxation mechanism. 17 Initially the environment of the photoexcited cis isomer is considered to still be ''adjusted'' to the geometry of the trans isomer, thus the probability of back reaction cistrans is the highest. Later on, in the course of the structural relaxation, the surrounding matrix readjusts to the geometry of the cis isomer and the probability for the cistrans relaxation decreases.…”
Section: Temperature Dependence Of Parametersmentioning
confidence: 99%
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