Electronic Transitions of Polyalkylthiophenes Partially Derivatized with NLO Chromophores: A Theoretical and Experimental Study

Abstract

Summary: The UV‐vis spectral profiles of some alkylthiophene copolymers in CHCl3 solutions, variously substituted with an azobenzenic NLO chromophore have been carefully analyzed and distinct intensity contributions have been assigned to the overlapped electronic transitions appearing in the lower energy part of the spectra. The different spectral behaviours are influenced by the chromophore content, the length of the alkylic side‐chain of the plastifying comonomer and, more significantly, by the number of the carbon atoms in the oligomethylenic spacer between the chromophoric group and the conjugated polythiophenic chain. This latter finding can be correlated with the strong steric hindrance caused by chromophore crowding in close proximity to the polymeric backbone. As the intensity distributions may be reasonably compared with the NLO properties, identification of the above parameters and of their role is an important step towards the synthesis of polyalkylthiophenes with predictable electronic properties and the development of materials with enhanced NLO characteristics.Graphical surfaces of the highest‐occupied (HOMO)s and the lowest unoccupied (LUMO) molecular orbitals involved in the first three π–π* electronic transitions of the chromophoric system.magnified imageGraphical surfaces of the highest‐occupied (HOMO)s and the lowest unoccupied (LUMO) molecular orbitals involved in the first three π–π* electronic transitions of the chromophoric system.

Third-Order Nonlinear Optical Behavior of Novel Polythiophene Derivatives Functionalized with Disperse Red 19 Chromophore

“…This difference was sufficient to increase the nonlinear properties of the polymers in solid state. The regioregularity (diads and triads) molecular weight distribution (Mn and Mw) and thermal properties ( and ) are similar with those normally found in PT synthesized according to the same regioselective method [15][16][17][18][19][20][21][22][23][24][25][26][27][28][29][30]. These values were also similar between both copolymers; only the copolymer obtained from 3-HT showed a higher polydispersity consistent with the presence of a greater amount of TDR19 in the copolymer P1.…”

“…Moreover, the presence of various substituents in 3-and/or 4-positions of the thiophene ring results in new materials which combine the physical properties of the polyconjugated backbone and the substituent group. For instance, a push-pull chromophore as a side group 2 International Journal of Polymer Science in the conjugated backbone enhanced charge-transfer properties and second-order NLO responses of a polythiophene [15][16][17][18][19][20][21][22][23][24][25][26][27][28][29][30]. The third-order NLO response in PT and other conjugated polymers has been also reported although less extensively in comparison with the second-order one, by using different techniques such as electroabsorption andscan [31,32].…”

Synthesis and Physicochemical Characterization of New Polythiophenes Based on Three Different Monomers

“…Aditionally, their fuctionalization is relatively easy and synthesizing 3-and/or 4-substituted polythiophenes can produce new materials which combine physical properties characteristic of the polyconjugated backbone with specific properties of a given substituent. For example, push-pull chromophores functionalization, combine second-order NLO properties of the choromophore with third order NLO properties of the conjugated backbone [2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17][18]. Polythiophenes have promising applications in electrochromic devices [19], biosensors [20], electrochemical supercapacitors [21], anticorrosion [22], transistors with polymer films [23][24][25], polymer light emitting diodes [26,27], photodetectors and organic polymer solar cells [28].…”

Sharp Increase in the (Hyper)polarizabilities of Quinoid-Type Isonaphtothiophene (INT) Oligomers: A Quantum Chemical Insight

“…Geometrical and electronic effects have been studied for polydiethynylsilane (PDES) and polysilole (PS) on the static polarizability (α) and the second hyperpolarizability (γ) at longitudinal components . An investigation showed that the factors affecting the spectral shape have been correlated with the NLO efficiency of the copolymers . Furthermore, a key factor of the diffusion electron to enlarge the first hyperpolarizabilites of alkali salts was reported several years ago .…”

“…33 An investigation showed that the factors affecting the spectral shape have been correlated with the NLO efficiency of the copolymers. 34 Furthermore, a key factor of the diffusion electron to enlarge the first hyperpolarizabilites of alkali salts was reported several years ago. 9 This drives us to ask is the synthesized metal-like conducting polymer capable to enhance the hyperpolarizabiltities like the alkali metal doped systems.…”