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Related Concept Videos

UV–Vis Spectroscopy: Woodward–Fieser Rules01:29

UV–Vis Spectroscopy: Woodward–Fieser Rules

UV–Visible absorption spectra of conjugated dienes arise from the lowest energy π → π* transitions. The light-absorbing part of the molecule is called the chromophore, and the substituents directly attached to the chromophore are called auxochromes. A strong correlation exists between the absorption maxima, λmax, and the structure of a conjugated π system. The Woodward–Fieser rules predict the value of λmax for a given structure by adding the contributions...
Structure of Conjugated Dienes01:16

Structure of Conjugated Dienes

Introduction
Conjugated dienes are compounds characterized by the presence of alternating double and single bonds. In a conjugated system like 1,3-butadiene, the unhybridized 2p orbital on each carbon overlaps continuously, allowing the π electrons to be delocalized across the entire molecule. In contrast, this type of overlap does not occur in cumulated and isolated dienes, such as 2,3-pentadiene and 1,4-pentadiene, respectively. Instead, the π electrons remain localized between the double...
Conformations of Cyclohexane02:11

Conformations of Cyclohexane

Cyclohexane does not exist in a planar form due to the high angle and torsional strain it would experience in the planar structure. Instead, it adopts non-planar chair and boat conformations.
The chair form is the most stable and derives its name from its resemblance to the “easy chair.” In the chair conformation, two carbon atoms are arranged out-of-plane — one above and one below, minimizing the torsional strain. In the chair form, the bond angle is very close to the ideal tetrahedral value,...
UV–Vis Spectroscopy of Conjugated Systems01:32

UV–Vis Spectroscopy of Conjugated Systems

Organic compounds with conjugated double bonds show strong absorption features in the UV–visible region of the electromagnetic spectrum attributed to π → π* electronic excitations. Generally, a UV–vis absorption spectrum is recorded as a plot of absorbance vs wavelength. The wavelength of maximum absorbance, which manifests as a peak in the absorption spectrum, is denoted as λmax.
One of the factors influencing λmax is the extent of conjugation in the...
Stability of Conjugated Dienes01:28

Stability of Conjugated Dienes

Introduction
A comparison of the enthalpies of hydrogenation of dienes reveals that conjugated dienes release less heat on hydrogenation, rendering them more stable than their nonconjugated analogs.
¹H NMR of Conformationally Flexible Molecules: Variable-Temperature NMR01:15

¹H NMR of Conformationally Flexible Molecules: Variable-Temperature NMR

The axial and equatorial protons in cyclohexane can be distinguished by performing a variable-temperature NMR experiment. In this process, except for one proton, the remaining eleven protons are replaced by deuterium. The deuterium substitution avoids the possible peak splitting caused by the spin-spin coupling between the adjacent protons. The remaining proton flips between the axial and equatorial positions.

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Related Experiment Video

Updated: Jul 16, 2026

Synthesis of Cyclic Polymers and Characterization of Their Diffusive Motion in the Melt State at the Single Molecule Level
06:55

Synthesis of Cyclic Polymers and Characterization of Their Diffusive Motion in the Melt State at the Single Molecule Level

Published on: September 26, 2016

Conformations in dioctyl substituted polyfluorene: a combined theoretical and experimental Raman scattering study.

C Volz1, M Arif, S Guha

  • 1Department of Physics and Astronomy, University of Missouri, Columbia, Missouri 65211, USA.

The Journal of Chemical Physics
|February 23, 2007
PubMed
Summary

Polyfluorene (PF8) structures depend on side chains. Raman spectroscopy and DFT calculations reveal how alkyl side chain conformations influence backbone planarity and induce the beta phase in polyfluorenes.

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The Preparation and Properties of Thermo-reversibly Cross-linked Rubber Via Diels-Alder Chemistry
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Last Updated: Jul 16, 2026

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Studying Soft-matter and Biological Systems over a Wide Length-scale from Nanometer and Micrometer Sizes at the Small-angle Neutron Diffractometer KWS-2
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The Preparation and Properties of Thermo-reversibly Cross-linked Rubber Via Diels-Alder Chemistry
07:02

The Preparation and Properties of Thermo-reversibly Cross-linked Rubber Via Diels-Alder Chemistry

Published on: August 25, 2016

Area of Science:

  • Materials Science
  • Polymer Chemistry
  • Spectroscopy

Background:

  • Polyfluorenes (PF) exhibit structural sensitivity to functionalizing side chains.
  • Dioctyl-substituted polyfluorene (PF8) forms metastable structures influenced by thermal history and solvent choice during film formation.

Purpose of the Study:

  • To investigate the impact of crystallographic phases on the backbone and side chain morphology of PF8.
  • To correlate alkyl side chain conformations with observed structural changes in PF8 films.

Main Methods:

  • Utilized Raman scattering techniques to study structural changes in PF8.
  • Employed hybrid density-functional theory (DFT) with a 3-21G(*) basis set to calculate vibrational spectra of fluorene oligomers.
  • Modeled alkyl side chains in limiting conformations (all anti, anti-gauche-gauche, end gauche).

Main Results:

  • Experimental Raman spectra were analyzed in conjunction with theoretical calculations.
  • Demonstrated a link between specific alkyl side chain conformations and the formation of the beta phase in PF8.
  • Identified enhanced chain planarity in regions associated with the beta phase.

Conclusions:

  • Alkyl side chain conformation is a critical determinant of polyfluorene structural properties.
  • The beta phase in PF8 originates from specific side chain conformations leading to increased backbone planarity.
  • Raman spectroscopy combined with DFT provides valuable insights into polymer morphology and phase transitions.