We use optical and scanning force microscopy to explore the possibility of switching stability a bilayer poly(methyl methacrylate) (PMMA) on polystyrene by simply changing film thickness. show that for thin PMMA layers thicker films layer is unstable thickness fluctuations. However, are when they substantially thinner than now stable film. Dewetting morphologies cataloged as function individual polymer identifying which mechanism, be it spinodal dewetting or heterogeneous thermal nucleation....

Abstract The combined effects of illumination and thermal annealing on the morphological stability photodimerization in polymer/fullerene thin films are examined. While is known to cause fullerene dimerization stress their dedimerization, operation solar cells involves exposure both. competitive outcome these factors with blends phenyl‐C61‐butyric acid methyl ester (PCBM) polystyrene (PS), supported PEDOT:PSS quantified. UV–vis spectroscopy employed quantify dimerization, time‐resolved...

We have used helium-3 nuclear reaction analysis to study the morphology of spin-cast blends poly(9,-dioctylfluorene) (F8) and poly(9,-dioctylfluorene-alt-benzothiadiazole) as a function composition, casting solvent, initial solvent concentration. In cast from toluene, surface segregated layer is observed for broad range F8 compositions. The excess has maximum nm at an volume fraction ϕ = 0.5, dropping down –2 0.2 0.8. existence such layers could play important role in charge transport...

Abstract Low operating voltage is an important requirement that must be met for industrial adoption of organic field‐effect transistors (OFETs). We report here solution fabricated polymer brush gate insulators with good uniformity, low surface roughness and high capacitance. These ultra thin films, synthesized by atom transfer radical polymerization (ATRP), were used to fabricate OFETs both evaporated pentacene deposited poly(3‐hexylthiophene). The semiconductor‐dielectric interfaces in...

Fourier transform infrared spectroscopy was used to study the thermally induced conformational transitions undergone by lysozyme adsorbed different lipid layers. The role of electrostatic interaction in protein adsorption and thermal denaturation investigated considering this protein, which at pH 7.0 carries a positive charge, with anionic, zwitterionic, cationic There are qualitative quantitative differences between both unfolding formation intermolecular beta sheets surfaces. Unfolding is...

Poly(3,4 ethylene dioxythiophene)/poly(styrene sulfonate) (PEDT/PSS) blends are widely used in organic light‐emitting diodes (OLEDs) to enhance their performance. Using neutron reflectometry study such blends, it is shown that substantial segregation of the blend components occurs at surface (see Figure), a result will have implications both for performance and stability optoelectronic devices using PEDT/PSS.

The stability and association of polymer–fullerene films upon thermal annealing depends strongly on exposure to light, even at ambient conditions. As a result, dewetting nanocomposite can be prevented the characteristic lengthscales phase separated morphologies finely tuned. Coupling photopatterning with either self-organization process provides powerful route for directed assembly fullerene-based nanocomposites into functional "circuits".

In-situ grazing incidence X-ray diffraction has been used to investigate the kinetics of crystallization at surface thin films poly(ethylene terephthalate) (PET). By varying angle beam around critical film, penetration depth can be tuned allow a direct comparison molecular ordering in and bulk film. The results show that occurs significantly faster temperature range 90−100 °C (close glass transition 75 °C). (0 1̄ 1) 1 0) peaks narrow more rapidly achieve lower width, indicating progresses...

We discuss some recent findings relating to the structure of interfaces in semiconducting polymer devices. The three different types interface is characterized via neutron reflectivity and scanning force microscopy. In first example we find that enrichment dopant occurs at surface a doped polymeric conductor, this enriched layer penetrates several nanometres into material. Secondly, between an insulating not molecularly sharp, but rather broad with width typically order 1 nm. Finally present...

The growth-kinetics of PCBM crystals, on two different length-scales, is controlled by the thickness polymer layer within a PCBM–polymer bilayer.

The interfacial roughness at a buried dielectric–semiconductor interface in an all-polymer field-effect transistor (FET) is characterised by specular neutron reflectivity. Using mixed solvent (toluene–cyclohexane) to deposit poly(9,9-dioctylfluorene-alt-bithiophene) (F8T2) directly on top of poly(methylmethacrylate) (PMMA), we are able fabricate bilayer FET architectures with systematically controlled the polymer–polymer over range approximately 1 3 nm, simply changing ratio. This system has...

Abstract Neutron reflectivity and photoluminescence measurements are reported on bilayers of polyfluorene‐based conjugated polymers. By using a novel thermal processing procedure it is possible to control the width interface between poly(9,9‐dioctylfluorene) (F8) poly(9,9‐dioctylfluorene‐ alt ‐benzothiadiazole) (F8BT), measure impact interfacial roughness resonant energy transfer excitons at (Förster transfer). It found that increasing root mean square (rms) F8/F8BT over range ∼1 nm ∼5 leads...

Specular neutron reflectivity and nuclear reaction analysis (NRA) are used to measure the interfacial width between poly(9,9-dioctylfluorene) (F8) poly(9,9-dioctylfluorene-alt-benzothiadiazole) (F8BT) in a 500 nm bilayer. Annealing at temperatures up 280 °C allows us vary this over large range, from ∼1 greater than 30 nm. Approximate calculations using predictions of self-consistent field theory (SCFT) for both Gaussian semiflexible chains suggest that liquid−liquid regime results SCFT valid...

Abstract Domain composition and interfacial structure are critical factors in organic photovoltaic performance. Here, we report neutron reflectivity, grazing-incidence X-ray diffraction atomic force microscopy measurements of polymer/fullerene thin-films to test a hypothesis that these partially miscible blends rapidly develop profiles consisting co-existing phases liquid-liquid equilibrium. We study range polymer molecular weights between 2 300 kg mol −1 , annealing temperatures 120 170 o...

We have used the technique of neutron reflectometry in order to evaluate changes that occur within polymer light-emitting devices as they are operated. The examined consisted an indium-tin-oxide, anode, a deuterated-poly(styrene sulfonate)/poly(3,4 ethylenedioxythiophene), ($d$-PSS/PEDT), charge injection layer, poly(fluorene), (F8), and low work-function cathode. found clear evidence for segregation $d$-PSS $d$-PSS:PEDT/F8 interface device driven until its brightness had fallen 10% initial...

Measurements have been performed on thermally equilibrated conjugated-polymer/insulating-polymer bilayers, using specular and off-specular neutron reflectivity. While reflectivity is only sensitive to the structure normal sample, measurements can probe of buried polymer/polymer interface in plane sample. Systematic analysis scattering from a set samples with varying insulating-polymer-thickness, distorted-wave Born approximation (DWBA), has allowed robust determination intrinsic width at...

Neutron reflectivity was used to study the interface between semiconducting polymer poly(9,9-dioctylfluorene) (PFO) and insulating poly(methyl methacrylate) (PMMA). The PFO/PMMA interfacial width measured in nematic crystalline phases of PFO, both with PMMA on top PFO vice versa. These interfaces are broad compared atomic length scales, widths range from 10 20 Å. We found that independent chosen geometry thermal processing history. equilibrium only depended temperature, phase being broader...

Interfaces between a poly(3-hexylthiophene) [P3HT] and an end-grafted (brush) layer of poly(methyl methacrylate) [PMMA] are shown using neutron reflectometry to be dependent on heat treatment. Annealing the samples allows part brush cross into P3HT creating very asymmetric interface. We suggest that rearrangement occurs, space for movement film. This interpenetration was observed with two different molecular weight (17.5 28 kg mol−1) films. Output characteristics devices made from layers...

Following annealing at sufficiently high temperatures, well-controlled thin-film bilayers exhibit thermal changes in phase-composition, phase-volume and interfacial roughness that are reversible, irrespective of the starting layer compositions.

The early-stage roughening of the interface between thin deuterated poly(methyl methacrylate) (d-PMMA) layers on thick polystyrene (PS) films was studied as a function temperature using real-time specular neutron reflectivity. By measuring growth roughness precursor dewetting, characteristic time constant early stages process approaching glass transition $({T}_{g})$ two polymers from above and compared with prediction by spinodal process. Both solid liquid regimes were probed, in which...

Abstract High aspect‐ratio poly(9,9′‐dioctylfluorene) (F8) nanowires are fabricated on top of silicon/amorphous Teflon substrates, by dewetting F8 thin‐films. The conjugated nature the polymers enables self‐assembly continuous molecularly‐aligned several micrometers in length and tens nanometers width, without using a template. sizescale dewetted morphology can be controlled varying thickness amorphous layers. As predicted van der Waals theory characteristic increases with film thickness....