Macromolecular chemistry and physics 1994

Eisenbach, Claus D.; Haarer, D.; Schmidt, Manfred

doi:10.1002/actp.1995.010460101

Cited by 7 publications

(16 citation statements)

References 106 publications

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“…16 Consistent with these observations, the distribution of free volume at sites is narrowed upon annealing (physical aging) of poly-(methyl methacrylate) below its glass transition temperature; the number of sites with larger free volumes is decreased more than the ones with smaller free volumes. 38 Here, we have demonstrated that the thermal cis f trans isomerizations of azobenzenyl groups also follows two distinct kinetic pathways in drawn, partially crystalline polyethylene above the glass transition temperature.…”

Section: Discussionsupporting

confidence: 56%

“…Two parallel first-order cis f trans rate processes have been observed for azobenzene groups incorporated within the main chains of an annealed polymer as well, and the rate of the slower one is similar to the unique rate measured in newly prepared (unannealed) films. 16 The appearance of the faster component when films are either annealed or drawn suggests that it is associated with "stressed" cis isomers in sites in the regions where polymer chains are more ordered, the free volume is smaller, and chain relaxation is slower.…”

Section: Discussionmentioning

confidence: 99%

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Thermal Cis → Trans Isomerization of Covalently Attached Azobenzene Groups in Undrawn and Drawn Polyethylene Films. Characterization and Comparisons of Occupied Sites

Wang

Weiss

2003

Macromolecules

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The thermal cis f trans isomerization of azobenzene groups covalently attached to chains of undrawn and drawn polyethylene films (Azo-PE) has been examined in a temperature range that is well above the glass transition and well below the melting transition. Isomerizations in undrawn films at all temperatures and in a drawn film at 70°C, the highest temperature examined, follow singlecomponent first-order kinetics. At 20-65°C, two first-order components whose activation energies are both smaller than that of the undrawn film are needed to describe the isomerization kinetics in the drawn state. Doped (i.e., noncovalently attached) azobenzene groups in polyethylene films (Azo/PE) also exhibit a biexponential kinetics after drawing, but the fraction of the faster component is much smaller than that in the drawn Azo-PE films. Comparisons between the rate constants for isomerization of undrawn and drawn Azo-PE and Azo/PE films at the same temperature indicate that as a consequence of probe translocations the populations of sites occupied by the probe change significantly when the doped film is drawn. The faster and slower rate components in drawn Azo-PE are assigned to cis isomers residing in interfacial and amorphous sites, respectively, on the basis of differences in polymer chain ordering, rates of relaxation, and free volumes at occupied sites in interfacial and amorphous regions. These results are discussed in terms of how the micromorphological changes in PE when it is drawn affect the dynamics of the guest molecules and how the latter provides information about the local PE matrix.

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Section: Discussionsupporting

confidence: 56%

Section: Discussionmentioning

confidence: 99%

Thermal Cis → Trans Isomerization of Covalently Attached Azobenzene Groups in Undrawn and Drawn Polyethylene Films. Characterization and Comparisons of Occupied Sites

Wang

Weiss

2003

Macromolecules

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“…13,16 The characteristics of the P22DPy and PS-co-SSH employed in this work are compiled in Table 1.…”

Section: Methodsmentioning

confidence: 99%

Miscibility of Rigid-Rod and Random-Coil Macromolecules through Acid−Base Interactions

Eisenbach¹,

Hofmann²,

Göldel³

et al. 1999

Macromolecules

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Acid-base interactions can be used to overcome the free energy barrier to the mixing of rods and coils, originating primarily from the reduced entropy of the coil conformation in the presence of rods. A study of rigid-rod polydiacetylene, carrying pyridine side groups, and sulfonated polystyrene blends, in conjunction with a modified Flory theory, shows a rich variety of observed and expected phase behavior.

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“…Another possibility is to produce grafted copolymers with a variety of different grafts by incomplete decomposition of the azo functions in the presence of different monomers (31). Using the basic reaction shown above, azo copolymers can be obtained by substituting for the azo compound a mixture of the azo compound and a similar, but azo-free, monomer (48)(49)(50)(51).…”

Section: N2o3mentioning

confidence: 99%

“…Highly conjugated azo polymers are usually brown or black, whereas the polymers obtained from prepolymeric amines are lighter (78,79). The cis-trans isomerization of the azo functions has been used to study chain mobility in polymers (48)(49)(50)(51)88). Azo groups in the main chain confer liquidcrystal properties (45,(89)(90)(91), recognizable by the turbidity of polymer solutions, opalescence upon stirring, and depolarization of plane-polarized light.…”

Section: N2o3mentioning

confidence: 99%

Azo Polymers

Nuyken¹

2011

Encyclopedia of Polymer Science and Technology

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Azo‐containing polymers (azo polymers) can be formally classified according to a variety of criteria. In this review, the thermal stability of the NN group is the principal criterion. A further subdivision, according to the position of the NN group, is main‐chain azo groups, where each monomer unit contains a stable or unstable azo function or in copolymers in which one component contains an azo group, vs. side‐chain azo groups, where each monomer contains an azo group or in copolymers in which one component contains an azo function.

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Macromolecular chemistry and physics 1994

Cited by 7 publications

References 106 publications

Thermal Cis → Trans Isomerization of Covalently Attached Azobenzene Groups in Undrawn and Drawn Polyethylene Films. Characterization and Comparisons of Occupied Sites

Thermal Cis → Trans Isomerization of Covalently Attached Azobenzene Groups in Undrawn and Drawn Polyethylene Films. Characterization and Comparisons of Occupied Sites

Miscibility of Rigid-Rod and Random-Coil Macromolecules through Acid−Base Interactions

Azo Polymers

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