Polymerization Of MMA In Presence Research Articles

Composition and excitation wavelength dependent photoluminescence color tuning in nanocomposite of PMMA and ZnO nanorods for PLED

Semiconducting nanocomposites of PMMA and ZnO are obtained by bulk polymerization of MMA in presence of hydrothermally synthesized ZnO nanorods. Three different phenomena i.e. FRET from PMMA to ZnO, red edge effect in PMMA, self-absorption in ZnO are found to be mainly responsible for the tunable luminescence in PMMA-ZnO nanocomposite. At excitation wavelength 285 nm, due to significant overlap between emission spectrum of PMMA and absorption spectrum of ZnO, FRET occurs from PMMA to ZnO and enhanced blue emission from the composite is obtained. Due to self-absorption in ZnO, the emission shows red shift up to few nanometers with increase in ZnO content. Again the energy transfer efficiency decreases with increase in ZnO content in the composite due to which emission intensity also decreases. Due to red edge effect the emission from PMMA shifts towards higher wavelength with the red shift of excitation wavelength. This causes no spectral overlap between PMMA and ZnO and no significant FRET occurs at excitation wavelength 377 nm. Here the emission from both PMMA and ZnO is observed and with increment of ZnO content the emission from ZnO becomes dominant. Thus with proper tuning of ZnO content in the composite, the emission from the composites excellently changes from deep blue to white upon illumination with photon of wavelength 377 nm. To get an insight of the applicability of the composites for polymer light emitting diode (PLED), electroluminescent property of the composites is investigated with the help of a mathematical model. From the calculated results, the external quantum efficiency (ηext) using the nanocomposite with 5 wt% of ZnO as emissive layer which emits light of wavelength 440 nm, is found to be the highest i.e. 5% at a turn-on voltage of 2.6 V. The other composites also show quite good ηext and hence become promising candidates for application in blue as well white light emitting PLED.

Effect of acceptor concentration in the FRET controlled photoluminescence of PMMA-ZnO nanocomposite for the application of PLED device

Luminescent PMMA-ZnO nanocomposites are synthesised through bulk polymerization of MMA in presence of ex-situ prepared ZnO nanoplates. Variation of ZnO concentration affects the optical properties of the composite. Introduction of ZnO in the PMMA matrix makes the composite as semiconducting in nature by creating a lower energy gap in the composite. Again Förster resonance energy transfer (FRET) between PMMA (donor) to ZnO (acceptor) enhances emission of ZnO significantly. But the enhanced emission decreases with increase in ZnO concentration, i.e. the emission intensity of PMMA-ZnO nanocomposite shows an increasing trend with decrease in the content of ZnO. The energy transfer efficiency varies from 97% to 52% when the concentration of ZnO varies from 10 wt% to 30 wt%. The Photoluminescence quantum efficiency of the composite showing highest emission is calculated and found to be 74%. Corresponding theoretically calculated electroluminescence quantum efficiency is 4% at an operating voltage of 3.1 V assuming all the injected charge carriers can generate singlet exciton if the composite showing highest emission is used as an emissive layer in PLED.

X-ray micro computed tomography, segmental relaxation and crystallization kinetics in interfacial stabilized co-continuous immiscible PVDF/ABS blends

Abstract A model immiscible blend system (PVDF/ABS, 50/50 wt/wt) was studied here and an attempt was made to stabilize the co-continuous structures using either a mutually soluble homopolymer (PMMA) or by introducing particles like graphene oxide sheets (GO) which preferentially localizes in PVDF or a combination of both i.e. PMMA wrapped GO, synthesized by in situ polymerization of MMA in presence of GO sheets (PMMA-GO). The improvement in structural properties couldn't be realized with GO alone or when added along with PMMA separately however, with PMMA-GO significant improvement in structural properties was realized. The coarsening of co-continuous microstructure during annealing was monitored here using both scanning electron microscopy and micro tomography. 2D SEM micrographs and the X-ray tomography reveal that the PVDF/ABS blends containing only PMMA coarsened upon annealing however, in presence of PMMA-GO although the phase dimension of the initial morphology was larger than the blends with only PMMA but the coarsening was suppressed as observed from micro-CT scans. The crystallization kinetics using modified Avrami model was assessed through non-isothermal DSC measurements to study the effect of PMMA, GO and PMMA-GO on the crystallization behaviour of the blends. Taken together, our results uncover an important observation wherein PMMA-GO effectively compatibilizes and stabilizes the morphology against post-processing operations like annealing in PVDF/ABS blends and also significantly improves the structural properties.

Effect of Multiwalled Carbon Nanotubes on the Properties of Poly(methyl methacrylate) in PMMA/CNT Nanocomposites

SummaryIn the present paper poly(methyl methacrylate) (PMMA)/multiwall carbon nanotubes (MWCNT) nanocomposites were prepared by bulk polymerization of MMA in presence of varying amounts of MWCNT and 2‐hydroxyethyl methacrylate (HEMA) modified MWCNT (HCNT) using azobisisobutyronitrile (AIBN) as an initiator. The nanocomposites were characterized for their structural, thermal, electrical and morphological behaviour using Fourier transform infrared spectroscopy (FTIR), Raman spectroscopy, dynamic mechanical analysis (DMA), thermogravimetric analysis (TGA), differential scanning calorimetry (DSC) and scanning electron microscopy (SEM). The presence of nanofiller inhibits the formation of head to head linkages as all the nanocomposite samples show two step degradation whereas PMMA prepared under similar condition showed three step degradation. The glass transition temperature (Tg) of PMMA increased after incorporation of MWCNTs. The obtained nanocomposites show an increasing trend in the molecular weight with increase in the wt % of MWCNT whereas it decreases with the increasing initiator concentration. It was observed that the electrical conductivity is the function of molecular weight of the polymer as well as the content of MWCNT in the nanocomposites. The electrical conductivity of PMMA/HCNT composites was slightly lower as compared to PMMA/MWCNT whereas an increasing trend in the storage modulus of PMMA/HCNT nanocomposites was observed.

Electrical and mechanical properties of PMMA/reduced graphene oxide nanocomposites prepared via in situ polymerization

We report the effect of filler incorporation techniques on the electrical and mechanical properties of reduced graphene oxide (RGO)-filled poly(methyl methacrylate) (PMMA) nanocomposites. Composites were prepared by three different techniques, viz. in situ polymerisation of MMA monomer in presence of RGO, bulk polymerization of MMA in presence of PMMA beads/RGO and by in situ polymerization of MMA in presence of RGO followed by sheet casting. In particular, the effect of incorporation of varying amounts (i.e. ranging from 0.1 to 2 % w/w) of RGO on the electrical, thermal, morphological and mechanical properties of PMMA was investigated. The electrical conductivity was found to be critically dependent on the amount of RGO as well as on the method of its incorporation. The electrical conductivity of 2 wt% RGO-loaded PMMA composite was increased by factor of 107, when composites were prepared by in situ polymerization of MMA in the presence of RGO and PMMA beads, whereas, 108 times increase in conductivity was observed at the same RGO content when composites were prepared by casting method. FTIR and Raman spectra suggested the presence of chemical interactions between RGO and PMMA matrix, whereas XRD patterns, SEM and HRTEM studies show that among three methods, the sheet-casting method gives better exfoliation and dispersion of RGO sheets within PMMA matrix. The superior thermal, mechanical and electrical properties of composites prepared by sheet-casting method provided a facile and logical route towards ultimate target of utilizing maximum fraction of intrinsic properties of graphene sheets.

Preparation of graft acrylic copolymers with a heterophase structure by latex-suspension polymerization

Polymerization of MMA in presence of a graft latex copolymer of butylacrylate(70% by weight) and MMA (30% by weight) has been investigated. The conditions in which particles of the emulsion-suspension copolymer form are defined. Electron microscopy and DTA have established that the copolymer particles have a heterophase structure. An equation is proposed for calculating the size of the dispersion drops in the system NMA-latex-water. Tests of the emulsion-suspension copolymer have been run with a maximum content of the latex copolymer (21% by weight) in the polymer-monomer composite. The impact strength of the material obtained was 10–12 kj/m 2.

Aspects of the inhibition of polymerization of methylmethacrylate by the chloraniltriethylamine system

The kinetic patterns of the polymerization of MMA in presence of chloranil and triethylamine including the presence of “critical” concentration of inhibitor and initiator are explained by the fact that an effective inhibitor forms as a result of the conversion of the charge transfer complex between chloranil and triethylamine to a radical pair.