Achieving the Blue Phase Photo-Physics of MEH-PPV through PMMA Matrix- A Cost Effective Technique

This paper presents the simplest and most economic method of achieving the oligomer conformation of poly[2-methoxy,5-(2-ethyl-hexyloxy)-p-phenylene-vinylene] (MEH-PPV), even under ordinary temperature and pressure conditions with poly methyl methacrylate (PMMA) as the insulating host matrix. The red phase photo physics of MEH-PPV undergoes blue phase transition, when highly diluted by the dielectric environment. In contrast to 588.4 nm red line emission by the neat MEH-PPV film, MEH-PPV/PMMA films emit in the range 500–535 nm with an excitonic peak at 455.6 nm, affirming the blue emission. The discrete emission peaks at 503.3 nm, 519 nm, 530 nm and 535 nm by the films can be correlated to the exciton delocalization lengths of trimeric, tetrameric, pentameric and hexameric regimes. The intra-chain excitonic coupling between the transition dipoles (TDMs) of the π-conjugated chains are interrupted by the PMMA matrix, causing the collapsed chain or oligomer conformations. TGA and DSC stability elucidations are theoretically supported by Coats-Redfern model of the thermal decomposition kinetics. An increase in the activation energy from 97.22 to 151.76 KJ/mole is noticed with the doping level. The FTIR resonant peaks corresponding to vinyl ring wagging and C = C stretching modes are noticed. The DC conductivity, AC conductivity and dielectric properties and of these films are also investigated and reported. The novelty lies in the unprecedented tuning of emission over the visible range, large Stoke’s shift, highly correlated photo physics parameters, the simple and cost-effective technique at ordinary laboratory conditions unlike the solvent vapor annealing (SVA) or thermal induced annealing (TIA) available in literature.