Control of π-Stacking for Highly Emissive Poly(p-phenylenevinylene)s:  Synthesis and Photoluminescence of New Tricyclodecane Substituted Bulky Poly(p-phenylenevinylene)s and Its Copolymers

Abstract

In the present work, we have demonstrated a facile approach to increase the luminescence of the poly (p-phenylenevinylene)s via controlling the molecular aggregates induced by pi-stacking. We have synthesized new bulky tricyclodecane (TCD) substituted PPVs: poly(2-methoxy-5-tricyclodecanemethyleneoxy-1,4-phenylenevinylene) (MTCD-PPV), poly(bis-2,5-tricyclodecanemethyleneoxy-1,4-phenylenevinylene) (BTCD-PPV), and a series of symmetrically substituted bulky PPV copolymers (P-1-P-7) covering the entire composition range from 0 to 100 mol %. The structures of the monomers and polymers were confirmed by 1H NMR and FTIR, and the molecular weights were determined by gel permeation chromatography. The composition analysis by NMR revealed that the bulky monomer was highly reactive and the incorporation of bulky units in MEH-PPV increased irrespective of the feed ratio. The polymers possess good solubility, high molecular weights, good thermal stability, and so forth. The molecular weights of the PPV copolymers were also significantly affected by the bulky substitution: the higher the incorporation of bulky units, the lower the molecular weight. The absorption and emission studies revealed that there was no influence on the MEH-PPV by TCD substitution in solution whereas in the solid state the photoluminescence intensity of PPV increased more than 10 times. The luminescence increase in PPV was observed throughout the entire bulk and was not confined to any particular domain in the polymer. The bulky PPV copolymers showed that both the luminescence intensity (in film) and quantum yields (in solution) increased with an increase in the extent of BTCD incorporation in the MEH-PPV and attained a maximum for 50% BTCD. The TCD unit has thus proved to be an efficient bulky susbstituent for PPV as it controls the pi-stack-induced molecular aggregates in the polymer chains by increasing the interchain distances. The new bulky PPV copolymers are highly soluble, thermally stable, and highly luminescent besides being economically cheap compared to the other materials reported so far for the bulkier approach in pi-conjugated materials.

Solvent-induced photoemissions of high-energy chromophores of conjugated Polymer MEH-PPV: Role of conformational disorder

“…This comparison is valid because slight modification of alkoxy side chain does not affect the optical properties of the chromophores. 29,30 Theoretical calculations of HOMO-LUMO energy gap of various PPV oligomers are also consistent. 31 The emission spectrum of the 0.02 mg/mL MEH-PPV95 solution constitutes of a peak at 558 nm with broad shoulder at about 607 nm as illustrated in Figure 1(b).…”

Electron delocalization in vinyl ruthenium substituted cyclophanes: Assessment of the through-space and the through-bond pathways

“…Implications are numerous and incluel e, inter alia , the photophysics of luminophores [6][7][8] or of polymers having exte nel eel arene substitue nts or backbones [9,10], the formation of self-assembleel coorelination cages [3,5,11] anel the exchange of magnetic [1 2-18] or electronic information [8,16,[19][20][21][22][23][24][25][26][27][28]. 7t-Stacking is also hel eI res ponsibl e for rapiel charge mig rati o n over oligonucleotieles a nel DNA [29][30][31][32] or columnar m eso phases mael e up of suitably functionalizeel eli sk-shape el bllileling blocks with exteneled aromatic cores [32][33][34][35][36][37].…”

Photophysical properties and quantum chemical studies of poly(2,7-9,9'-dihexylfluorene-dyil)

“…These emission spectra have a vibronic structure partially resolved as usually observed for fluorene-based polymers. [2][3][4][5][6][7][8][10][11][12][13][14][15][16][17] Furthermore, the emission profile is similar for all solvents with small spectral shifts (λ max = 415 nm for chloroform, λ max = 412 nm for toluene, λ max = 414 nm for THF and λ max = 416 nm for ethyl acetate). Table 1.…”

“…1,2009 The spectral range of emission of conjugated polymers depends on several intrinsic or extrinsic parameters. 9,13,[16][17][18][19][20][21][22] Among the intrinsic parameter the energy gap between the electronic bands is important and is associated with the critical conjugation length. 1,9,18 Evidences of the dependence of conjugation length and band position can be obtained either experimentally or using quantum mechanical theoretical techniques.…”