Enhanced and tunable photoluminescence of polyphenylenevinylenes confined in nanocomposite films

Abstract

(http://creativecommons.org/licenses/by/4.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly credited.Conformation of macromolecules and interchain interactions determine spectral properties of conjugated polymers (CP). An achievement of spatial confinement of isolated chains is one of the routes to use this feature of CP for their purposeful usage. In the present work, CP/O300 nanocomposites based on CP -poly(p-phenylenevinylene) and poly(2-methoxy-5-(2′-ethylhexyloxy)-1,4-phenylenevinylene) -and silica nanoparticles (O300) are prepared. In comparison with many previously known hybrid nanomaterials synthesized with the similar purpose, CP/O300 nanocomposites are characterized by the essentially enhanced and tunable photoluminescence. The greatest change of color coordinates is observed for poly(p-phenylenevinylene)-based nanocomposites due to specific preparation method and interaction with the inorganic component. The main emission from CP in the CP/O300 nanocomposites is owing to 0-0 transitions, while 0-1 transitions, associated with aggregate states of the CP chains, are suppressed.Keywords: Conjugated polymers; Silica nanoparticles; Nanocomposite films; Spatial confinement; Tunable photoluminescence BackgroundConjugated polymers (CP) attract attention of many researches due to the perspective of their applications in different optoelectronic devices [1][2][3][4][5]. Functional characteristics of such devices depend not only on the chemical structure of the macromolecules but also on their conformation as well as interchain interactions, because π-π interaction can decrease the intermolecular distance and affect the charge transport and energy transfer [4,6,7].One route to determine the fine details of the processes that control the operation of solid CP-based devices is isolating the polymer chains. Such an effect was achieved previously by extreme dilution of CP solutions in the so-called 'good solvents ' [8,9], an isolation of CP chains as molecular wires in the structure of polyrotaxanes [ 10,11] or in a matrix of non-conductive organic polymers [12].An alternative approach was to achieve confinement of CP in inorganic materials. The effect was achieved when the CP macromolecule is inserted inside the cavities of different 2D and 3D non-conductive porous matrices [13][14][15][16][17][18][19][20][21][22][23][24][25][26]. Such hybrid nanocomposites were prepared by embedding CP macromolecules inside the pre-synthesized mesoporous particles [13][14][15][16][17][18] and films [19,20], also using an in situ method, i.e., during film formation [21,22], in the latter case. The procedure of exfoliation followed by successive adsorption of CP was used for layered matrices [7,[23][24][25][26].The studies of confinement of CP macromolecules permitted to establish a number of important regularities for luminescent properties of CP, as well as to evaluate the possibility and advantages of using this effect to create improved optoelectronic devices...

Polarized Emission from Conjugated Polymer Chains Aligned by Epitaxial Growth during Off-Center Spin-Coating

“…Furthermore, it may be worth remarking that the PL spectra of samples containing TCB display more structured spectral shapes with pronounced shoulders at 580 and 640 nm, respectively, forF8BT and MEH-PPV. Once again, this phenomenon agrees well with the crystallinity enhancement observed by XRD ( Figure 5) as these enhanced shoulders are typically ascribed to an increase in interchain interactions of the conjugated polymer materials [18]. The highest polarized PL intensities for off-center spin-coated samples with TCB are measured at angles of 15 and 30 degrees with respect to the fiber axis for F8BT and MEH-PPV, respectively.…”