Poly(3-alkylthiophene)s show unexpected second-order nonlinear optical response

Abstract

Regioregular poly(3-hexylthiophene)s with chain lengths varying from 5 to 100 monomers are synthesized. Poly(3-hexylthiophene)s show in solution an unexpectedly significant second-order nonlinear optical response. The increase in transition dipole moment upon oligomerisation causes the significant second-order nonlinear optical response.

Hydrodynamic properties and conformation of poly(3-hexylthiophene) in dilute solutions

“…Poly(thiophene)s belong to the class of polyconjugated polymers with delocalized π‐electron system which is responsible for a number of important practical properties (conductivity, electrochromism, nonlinear optical properties, magnetism, etc …”

Investigation of Bimetallic Nickel Catalysts in Catalyst‐Transfer Polymerization of π‐Conjugated Polymers

“…The α‐methylene protons of the dominant repeating H‐T thiophenes are located at 2.65–2.9 ppm and the integration signals at 2.5–2.65 ppm represent the α‐methylene protons that belong to the T‐T regioisomer and chain‐end rings (Figure ). By setting the integration of the α‐methylene protons (H b –H e ) equal to 2, the integration of H a plus 2 to accommodate the end‐group thiophene units equals DP …”

Model of a polymer chain twisted inside a statistical segment. Poly(3‐hexylthiophene) in chloroform solutions

“…The assumption that the direction of a statistical segment coincides with the backbone direction is commonly used in modern molecular studies of polymers (as a rule, by default). Within the framework of this approach, macromolecular parameters in Eqns – have the following designations: L is the length of the backbone (main chain) of a polymer molecule and d is the hydrodynamic diameter of a polymer chain.…”

“…Polythiophenes belong to the class of polyconjugated polymers; their π ‐electron system is responsible for both intramolecular structuring (which corresponds to the optimal balance between the energy of π ‐electron conjugation and steric repulsion between neighbouring monomer units) and intermolecular association . These two phenomena determine typical optical and electromagnetic properties of the polymer which are explained by intramolecular electromagnetism in various publications . Therefore, polythiophenes represent types of macromolecular objects demanding thorough consideration of intramolecular structuring of any kind (completely stretched chain, helical conformation, etc.).…”