Photochromic and fluorescent probe studies in glassy polymer matrices. 4. Effects of physical aging on poly(methyl methacrylate) as sensed by a size distribution of photochromic probes

Royal, J. Scot; Victor, John G.; Torkelson, John M.

doi:10.1021/ma00028a035

Cited by 45 publications

(34 citation statements)

References 10 publications

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“…We speculate that its unusual rotation behavior may be related to this. 38,39 . Table II reports ␤ values obtained from fits to anisotropy decay data at high temperatures and at T g .…”

Section: Resultsmentioning

confidence: 99%

How do molecules move near T g? Molecular rotation of six probes in o-terphenyl across 14 decades in time

Cicerone

Blackburn

Ediger

1995

The Journal of Chemical Physics

367

182

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Time resolved optical spectroscopy was used to observe molecular rotation over more than 14 decades in time for six probes in o-terphenyl (OTP). In contrast to previous studies, probe rotation times are found to depend significantly upon probe size in the deeply supercooled regime. Systematic deviations from the temperature dependence of the Debye–Stokes–Einstein equation are observed, however, these deviations are relatively small. These observations are inconsistent with some models of cooperative molecular motion near Tg which invoke rigid aggregates or locally liquidlike regions. The width of the relaxation spectrum (characterized by the KWW β parameter) systematically decreases with increasing probe size. Near Tg, the largest probe (rubrene) rotates with nearly a single exponential correlation function. Based on the observed trend in β, it is estimated that OTP is homogeneous on length scales greater than 2.5 nm at Tg.

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“…We speculate that its unusual rotation behavior may be related to this. 38,39 . Table II reports ␤ values obtained from fits to anisotropy decay data at high temperatures and at T g .…”

Section: Resultsmentioning

confidence: 99%

How do molecules move near T g? Molecular rotation of six probes in o-terphenyl across 14 decades in time

Cicerone

Blackburn

Ediger

1995

The Journal of Chemical Physics

367

182

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“…In this case the thermal back process has been described by two or three exponentials 3,12,17,18 or by the Kohlrausch-Williams-Watt stretched exponential model. 19 In the fundamental and applied chemistry maleimide derivatives are placed on an important place. Due to their dienophilic nature (Diels-Alder reaction, "click chemistry"), reactivity in Michael-addition reactions (especially for located S atoms in the protein and peptide structures), ability to undergo photocycloaddition, polymerization and crosslinking reactions this type of compounds is widely employed as substrates in chemical and biological applications.…”

Section: Introductionmentioning

confidence: 99%

Responsive behavior of 4-(N-maleimido)azobenzene in polymers with aromatic main chain and side chain linked units

Airinei¹,

Rusu²,

Bărboiu³

2010

J. Braz. Chem. Soc.

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Matrizes poliméricas com cadeia principal aromática e cadeias laterais formadas por unidades de poliestireno e polissulfona foram empregadas para construir filmes finos contendo moléculas de maleimidoazobenzeno, a fim de desenvolver novos materiais com propriedades responsivas. O comportamento fotocrômico do composto ativo foi estudado no estado sólido e em solução, para comparação. A isomerisação térmica cis-trans de cromóforos de azobenzeno em filmes finos de polímeros segue duas etapas cinéticas diferentes. Um processo de relaxação de segunda ordem (rápido e lento) ocorre em matriz de poliestireno abaixo de 70 o C, enquanto a isomerização térmica a 70 o C ou em temperatura mais alta segue cinética de primeira ordem. A quantidade de isômero cis correspondente ao estado fotoestacionário foi mais baixa em filmes do polímero do que em solução.Polymer matrices with aromatic main chain and side chain linked units (polystyrene, polysulfone) were employed to construct thin films containing maleimidoazobenzene molecules in order to develop new materials with responsive properties. The photochromic behavior of the active compound was studied both in the solid and solution state for comparison. The thermal cistrans isomerization of azobenzene chromophores in polymer films follows two different kinetic pathways. A double-exponential relaxation process (fast and slow) took place in polystyrene matrix under 70 o C while the thermal isomerization at 70 o C and higher follows a first-order kinetics. The cis isomer content corresponding to the photostationary state was found to be lower in polymer films than in solution.

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“…fluorescent ro-'5) and photochromic probes [16][17][18][19][20][21][22], and various scattering techniques 23,24). In particular, the fluorescent and photochromic probing techniques have been most useful in characterizing the evolution of the polymer structure during polymerization.…”

mentioning

confidence: 99%

Radical concentrations, environments, and reactivities during crosslinking polymerizations

Anseth

Anderson

Bowman

1996

Macro Chemistry & Physics

125

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Radical environments and concentrations during the crosslinking polymerizations of multiethylene glycol dimethacrylates were characterized with electron spin resonance spectroscopy. The relative concentrations of free and trapped radicals were used as a measure of certain structural features in the evolving polymer, especially with respect to microgel formation. The influence of monomer structure and crosslinking density on the polymer structure was studied by examining the radical behavior during the polymerization of diethylene glycol dimethacrylate, poly(ethy1ene glycol 200) dimethacrylate, and poly(ethylene glycol 600) dimethacrylate. The extent of radical trapping and microgel formation was found to increase with increasing crosslinking density. The influence of the rate of initiation on radical trapping was also investigated, and slower rates of polymerization led to a higher fraction of trapped radicals with respect to the total radical population. Finally, the termination mechanism of radicals was characterized (long-term and short-term) and the corresponding kinetic constants quantified.

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Photochromic and fluorescent probe studies in glassy polymer matrices. 4. Effects of physical aging on poly(methyl methacrylate) as sensed by a size distribution of photochromic probes

Cited by 45 publications

References 10 publications

How do molecules move near T g? Molecular rotation of six probes in o-terphenyl across 14 decades in time

How do molecules move near T g? Molecular rotation of six probes in o-terphenyl across 14 decades in time

Responsive behavior of 4-(N-maleimido)azobenzene in polymers with aromatic main chain and side chain linked units

Radical concentrations, environments, and reactivities during crosslinking polymerizations

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