Name: monitoring the effects of illumination on the structure of conjugated polymer gels using neutron scattering
Uploaded: 2017-12-21T12:30:00
Description: Watch this Scientific Journal Video about Monitoring the Effects of Illumination on the Structure of Conjugated Polymer Gels Using Neutron Scattering at JoVE.com

The authors gratefully acknowledge the National Science Foundation (DMR-1409034) for support of this project. We also acknowledge the support of the National Institute of Standards and Technology, U.S. Department of Commerce, in providing the USANS facilities used in this work, where these facilities are supported in part by the National Science Foundation under Agreement No. DMR-0944772. The SANS experiments of this research were completed at ORNL&#39;s High Flux Isotope Reactor, which was sponsored by the Scientific User Facilities Division, Office of Basic Energy Sciences, US Department of Energy.

All handling of chemicals should be carried out with proper personal protective equipment and within a safety hood. All samples exposed to ionizing radiation should be handled under the supervision of the facilities radioactive control technicians. This protocol was performed by individuals who had completed appropriate radiation safety training.
1. Preparation of P3HT in d-ODCB Solutions
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	<li>Sample Acquisition
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		<li>Purchase 1 g of high regioregularity (&#62;90%...

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SANS &amp; USANS Data Reduction and Analysis Available from: <a target="_blank" href="https://www.ncnr.nist.gov/programs/sans/data/red_anal.html">https://www.ncnr.nist.gov/programs/sans/data/red_anal.html</a> (2017)</li><li>Feigin, L., Svergun, D. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=.">.</a> Structure Analysis by Small-Angle X-Ray and Neutron Scattering. , (1987).</li><li>Mittelbach, P. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Zur+Rontgenkleinwinkelstreuung+verdunnter+kolloider+systeme.">Zur Rontgenkleinwinkelstreuung verdunnter kolloider systeme.</a> Acta Phys. Austriaca. 14, 185-211 (1961).</li><li>Schulz, G. 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First, looking at the SANS data as a function of temperature, the increase in the Elliptical Cylinder Model scale factor indicates a marked increase in the amount of P3HT present in the nanofibril phase, which isconsistent with the progression of the gelation process. Simultaneously, the decrease in free chain Rg paired with an increase in Porod exponent reveals that the deteriorating thermodynamic conditions associated with temperature decrease are causing a chain collapse in the P3HT chains still present in ...

Conjugated polymers promise functional materials that can be utilized in a broad range of devices, such as organic light emitting diodes, organic semiconductors, chemical sensors, and organic photovoltaics.1,2,3,4,5,6 A crucial aspect of the performance in these devices is the ordering and packing of the conjugated polymer in the solid state in the active layer.7,8,9,10,11,12,13,14 This morphology is&#160;largely&#160;pre-determined by both the conformation of the polymer chain in solution as well as the structures that&#160;evolve as these solutions are cast unto a substrate and the solvent is removed. By studying the structures present throughout a typical sol-gel transition of a model optoelectronic polymer in a suitable solvent, these systems can be effectively modeled and a quantitative glimpse into the self-assembly that occurs during material deposition can be obtained.15,16,17,18,19,20
Specifically, we examine the conjugated polymer benchmark P3HT in the solvent deuterated ortho-dichlorobenzene (ODCB), a polymer-solvent system which has seen extensive use due to its suitability for a variety of organic electronic device fabrication techniques.23,24,25 In this given solvent environment, P3HT chains begin to aggregate upon an appropriate environmental stimuli, such as temperature decrease or loss of solvent quality. The exact mechanism for this assembly process is under investigation, with one of the leading proposed pathways believed to be a gradual process where individual P3HT molecules &#960;-stack to form lamellar nano-aggregates known as nanofibrils, which then themselves agglomerate to form larger micron scale macro-aggregates.24 Understanding these pathways and the resultant structures formed is&#160;key to properly predicting and influencing the formation of optimal device active layer morphologies.
Towards this ultimate goal of more precisely directing the formation of these active layer architectures, there exists a need to develop additional experimental and industrial methods to non-destructively alter conjugated polymer morphology in-situ. One relatively new methodology centers around the use of light exposure as an inexpensive means for altering polymer chain morphology, with both computational and experimental results pointing towards its feasibility.25,26,27 Recent work by our laboratory has indicated the existence of a light induced alteration of the conjugated polymer-solvent interaction in a dilute solution, leading to a notable change in polymer chain size upon illumination.30,31 Here, we present a protocol to continue this work by effectively monitoring the effects of exposing a much more concentrated conjugated polymer solution to direct light&#160;throughout a gelation process that is directed by a thermostat-controlled temperature ramp. We employ neutron scattering as it allows robust analysis of structural parameters of the polymer-solvent sol-gel system on length scales from angstroms to microns, an ability not possible through other more common rheological or spectroscopic instrumental methods.16,17,30,31 Thus, by comparing the properly analyzed small and ultra-small angle neutron data for the assembly of gels formed under illumination to identical data collected in complete darkness, structural differences brought on by illumination-driven effects can be comprehensively identified and quantified.

<table border="0" cellpadding="0" cellspacing="0" width="822">
	<tbody>
		<tr height="21">
			<td height="21" style="height:21px;width:353px;">M(106) poly(3-hexylthiophene-2,5-diyl) (P3HT)</td>
			<td style="width:143px;">Ossila</td>
			<td style="width:160px;">104934-50-1</td>
			<td style="width:167px;">Conjugated polymer</td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;">deuterated 1,2 ortho-dichlorobenzene (ODCB)</td>
			<td style="width:143px;">Sigma Aldrich</td>
			<td>AC321260050</td>
			<td>solvent</td>
		</tr>
	</tbody>
</table>

monitoring the effects of illumination on the structure of conjugated polymer gels using neutron scattering

We demonstrate a protocol to effectively monitor the gelation process of a high concentration solution of conjugated polymer both in the presence and absence of white light exposure. By instituting a controlled temperature ramp, the gelation of these materials can be precisely monitored as they proceed through this structural evolution, which effectively mirrors the conditions experienced during the solution deposition phase of organic electronic device fabrication. Using small angle neutron scattering (SANS) and ultra-small angle neutron scattering (USANS) along with appropriate fitting protocols we quantify the evolution of select structural parameters throughout this process. Thorough analysis indicates that continued light exposure throughout the gelation process significantly alters the structure of the ultimately formed gel. Specifically, the aggregation process of poly(3-hexylthiophene-2,5-diyl) (P3HT) nano-scale aggregates is negatively affected by the presence of illumination, ultimately resulting in the retardation of growth in conjugated polymer microstructures and the formation of smaller scale macro-aggregate clusters.

Through SANS and USANS experiments, the gelation process of P3HT in d-ODCB was effectively monitored from the dispersed solution state at 70 &#176;C to a fully gelled state at 20 &#176;C. These experiments were conducted in both complete darkness and under white light illumination. Figure 1 displays some example SANS reduced data curves from these experiments, with an example curve fit shown in Figure 2. From this data, the struc...

Watch this Scientific Journal Video about Monitoring the Effects of Illumination on the Structure of Conjugated Polymer Gels Using Neutron Scattering at JoVE.com

Monitoring the Effects of Illumination on the Structure of Conjugated Polymer Gels Using Neutron Scattering

A protocol for the analysis of gels formed from the optoelectronic conjugated polymer poly(3-hexylthiophene-2,5-diyl) (P3HT) using small and ultra-small angle neutron scattering in both the presence and absence of illumination is presented.

We demonstrate a protocol to effectively monitor the gelation process of a high concentration solution of conjugated polymer both in the presence and ...

The overall goal of this experiment is to quantify the structural evolution of conjugated polymers throughout the gelation process as a function of both temperature change and in situ light exposure. This method can help provide answers to key questions in the behavior of conjugated polymers. It provides insight into the importance of the presence of an exeton on their structure and assembly.The main advantage of this technique is that it allows unobtrusive and nondestructive analysis of the polymer length scales relevant to the structure's form during the conjugated polymer gelation process. To begin the procedure, filter five grams of high purity d4-ODCB through a 0.45 micrometer sieve. Then, place 0.34 grams of P3HT and 1.66 grams of filtered d4-ODCB in five gram glass vial containing a stir bar.Cap the vial with a foil-lined cap and seal the vial with plastic paraffin film. Wrap the vial in aluminum foil to completely exclude light. It is critical to minimize the light exposure that the sample receives from ambient lighting, such as fluorescent room lights.Samples should not be left on bench tops or in staging areas without sufficient shielding from illumination. Stir the solution at 70 degrees Celsius for a minimum of one to three hours. If the solution is not yet homogeneous, leave the solution stirring at 70 degrees Celsius.Once the solution is homogeneous, heat a glass pipette to 70 degrees Celsius in an oven. Use the heated pipette to quickly transfer the viscous solution to a clean, dry, one to two millimeter thick quartz banjo cell. Cap the banjo cell and seal the cell with plastic paraffin film.Wrap the cell in aluminum foil or store the cell in a light excluding container. Prepare a banjo cell containing only filtered d4-ODCB and an empty banjo cell as backgrounds. To begin the experiment, verify that the instrument sample stage is equipped with temperature controls capable of ranging from 70 to 20 degrees Celsius.Place the sample and background banjo cells in an appropriately sized holding block and label the holders. Wrap the block in 0.1 millimeter thick aluminum foil to exclude light while transferring the samples to the sample stage. Unwrap the samples, load the samples into the stage, and apply aluminum foil to the sample stage.Align and calibrate the SANS instrument. Set the detector distance close to its maximum setting. Based on count rates for the P3HT sample and the solvent blank, determine the appropriate scattering time for the experiment.Configure the sample heating scripts to ramp from 70 to 20 degrees Celsius, holding for 15 minutes at each ramp point within the scattering time. Heat the sample stage to 70 degrees Celsius and hold that temperature for 15 minutes to equilibrate the sample. Acquire SANS data, transmission data, and a blocked bean measurement for the sample.Acquire SANS data at room temperature for both the solvent blank and the empty cell. Upon completing the dark experiment, remove the aluminum foil from the sample stage. Position an optical illuminator with a halogen white light source so that the sample slot at the scattering collection position is fully illuminated.Measure and record the maximum light intensity at the sample position. Adjust the illuminator, if necessary, to achieve an intensity of at least 5, 000 lux. Equilibrate the sample at 70 degrees Celsius and collect sample and background data with the exact procedure used for the dark experiment.Process and analyze the data to determine key structural parameters. The reduced SANS data was fit to a linear combination of fitting equations representing nanofibril aggregates through the elliptical cylinder model and the free chains in solution through the polymer excluded volume model. Absolute intensity was observed to increase as temperature decreased for both the dark and light experiments.The distinct difference between the dark and light experiments for each temperature indicates that light exposure significantly affected the P3HT aggregation. Individual structural parameters were extracted from the combined model fit. The nanofibril surface area was consistently greater for samples studied in the dark.The elliptical cylinder model scale factor, which describes the amount of P3HT in the aggregate phase, was also greater for dark samples. The free chain radius of gyration was consistently smaller and the Porod exponent was higher for dark samples. Using ultra-small angled neutron scattering, the aggregate radius of gyration was found to be larger for dark samples at lower temperatures.Overall, the data indicates that exposure to light hindered P3HT aggregation. Once mastered, this technique should take about three to four hours for each sample. While attempting this procedure, remember to choose an appropriate fitting model that spans the entire length scale of interest.Literature, research, and trial and error customization will help find the most robust fitting model that fits your system with minimal residual discrepancy.

monitoring-effects-illumination-on-structure-conjugated-polymer-gels

Research

JoVE Journal

Chemistry

Structure and Coordination Determination of Peptide-metal Complexes Using 1D and 2D 1H NMR

Copper (I) binding by metallochaperone transport proteins prevents copper oxidation and release of the toxic ions that may participate in harmful redox reactions. The Cu (I) complex of the peptide model of a Cu (I) binding metallochaperone protein, which includes the sequence MTCSGCSRPG (underlined is conserved), was determined in solution under inert conditions by NMR spectroscopy.
NMR is a widely accepted technique for the determination of solution structures of proteins and peptides. Due to difficulty in crystallization to provide single crystals suitable for X-ray crystallography, the NMR technique is extremely valuable, especially as it provides information on the solution state rather than the solid state. Herein we describe all steps that are required for full three-dimensional structure determinations by NMR. The protocol includes sample preparation in an NMR tube, 1D and 2D data collection and processing, peak assignment and integration, molecular mechanics calculations, and structure analysis. Importantly, the analysis was first conducted without any preset metal-ligand bonds, to assure a reliable structure determination in an unbiased manner.

Structure and Coordination Determination of Peptide-metal Complexes Using 1D and 2D 1H NMR

The NMR-solution structure of a metallochaperone model peptide with Cu (I) was determined, and a detailed protocol from sample preparation and 1D and 2D data collection to a three-dimensional structure is described.

Copper (I) binding by metallochaperone transport proteins prevents copper oxidation and release of the toxic ions that may participate in harmful redox ...

Preparation of Highly Porous Coordination Polymer Coatings on Macroporous Polymer Monoliths for Enhanced Enrichment of Phosphopeptides

We describe a protocol for the preparation of hybrid materials based on highly porous coordination polymer coatings on the internal surface of macroporous polymer monoliths. The developed approach is based on the preparation of a macroporous polymer containing carboxylic acid functional groups and the subsequent step-by-step solution-based controlled growth of a layer of a porous coordination polymer on the surface of the pores of the polymer monolith. The prepared metal-organic polymer hybrid has a high specific micropore surface area. The amount of iron(III) sites is enhanced through metal-organic coordination on the surface of the pores of the functional polymer support. The increase of metal sites is related to the number of iterations of the coating process.
The developed preparation scheme is easily adapted to a capillary column format. The functional porous polymer is prepared as a self-contained single-block porous monolith within the capillary, yielding a flow-through separation device with excellent flow permeability and modest back-pressure. The metal-organic polymer hybrid column showed excellent performance for the enrichment of phosphopeptides from digested proteins and their subsequent detection using matrix-assisted laser desorption/ionization time-of-flight mass spectrometry. The presented experimental protocol is highly versatile, and can be easily implemented to different organic polymer supports and coatings with a plethora of porous coordination polymers and metal-organic frameworks for multiple purification and/or separation applications.

A procedure for the preparation of porous hybrid separation media composed of a macroporous polymer monolith internally coated by a high surface area microporous coordination polymer is presented.

We describe a protocol for the preparation of hybrid materials based on highly porous coordination polymer coatings on the internal surface of macroporous ...

Photodynamic Therapy with Blended Conducting Polymer/Fullerene Nanoparticle Photosensitizers

In this article a method for the fabrication and reproducible in-vitro evaluation of conducting polymer nanoparticles blended with fullerene as the next generation photosensitizers for Photodynamic Therapy (PDT) is reported. The nanoparticles are formed by hydrophobic interaction of the semiconducting polymer MEH-PPV (poly[2-methoxy-5-(2-ethylhexyloxy)-1,4-phenylenevinylene]) with the fullerene PCBM (phenyl-C61-butyric acid methyl ester) in the presence of a non-compatible solvent. MEH-PPV has a high extinction coefficient that leads to high rates of triplet formation, and efficient charge and energy transfer to the fullerene PCBM. The latter processes enhance the efficiency of the PDT system through fullerene assisted triplet and radical formation, and ultrafast deactivation of MEH-PPV excited stated. The results reported here show that this nanoparticle PDT sensitizing system is highly effective and shows unexpected specificity to cancer cell lines.

This protocol describes a method for the fabrication of conducting polymer nanoparticles blended with fullerene. These nanoparticles were investigated for their potential use as a next generation photosensitizers for Photodynamic Therapy (PDT).

In this article a method for the fabrication and reproducible in-vitro evaluation of conducting polymer nanoparticles blended with fullerene as the next ...

Layer-by-layer Synthesis and Transfer of Freestanding Conjugated Microporous Polymer Nanomembranes

CMP as large surface area materials have attracted growing interest recently, due to their high variability in the incorporation of functional groups in combination with their outstanding thermal and chemical stability, and low densities. However, their insoluble nature causes problems in their processing since usually applied techniques such as spin coating are not available. Especially for membrane applications, where the processing of CMP as thin films is desirable, the processing problems have hindered their commercial application.
Here we describe the interfacial synthesis of CMP thin films on functionalized substrates via molecular layer-by-layer (l-b-l) synthesis. This process allows the preparation of films with desired thickness and composition and even desired composition gradients.
The use of sacrificial supports allows the preparation of freestanding membranes by dissolution of the support after the synthesis. To handle such ultra-thin freestanding membranes the protection with sacrificial coatings showed great promise, to avoid rupture of the nanomembranes. To transfer the nanomembranes to the desired substrate, the coated membranes are upfloated at the air-liquid interface and then transferred via dip coating.

In this paper we describe the interfacial synthesis of conjugated microporous polymers (CMP) on sacrificial substrates, and the dissolution of the substrate for the preparation of freestanding CMP nanomembranes. In addition, we will describe how the fragile nanomembranes can be transferred to other substrates.

CMP as large surface area materials have attracted growing interest recently, due to their high variability in the incorporation of functional groups in ...

Functionalization of Single-walled Carbon Nanotubes with Thermo-reversible Block Copolymers and Characterization by Small-angle Neutron Scattering

We demonstrate a protocol for single-walled carbon nanotube functionalization using thermo-sensitive PEO-PPO-PEO triblock copolymers in an aqueous solution. In a carbon nanotube/PEO105-PPO70-PEO105 (poloxamer 407) aqueous solution, the amphiphilic poloxamer 407 adsorbs onto the carbon nanotube surfaces and self-assembles into continuous layers, driven by intermolecular interactions between constituent molecules. The addition of 5-methylsalicylic acid changes the self-assembled structure from spherical-micellar to a cylindrical morphology. The fabricated poloxamer 407/carbon nanotube hybrid particles exhibit thermo-responsive structural features so that the density and thickness of poloxamer 407 layers are also reversibly controllable by varying temperature. The detailed structural properties of the poloxamer 407/carbon nanotube particles in suspension can be characterized by small-angle neutron scattering experiments and model fit analyses. The distinct curve shapes of the scattering intensities depending on temperature control or addition of aromatic additives are well described by a modified core-shell cylinder model consisting of a carbon nanotube core cylinder, a hydrophobic shell, and a hydrated polymer layer. This method can provide a simple but efficient way for the fabrication and in-situ characterization of carbon nanotube-based nano particles with a structure-tunable encapsulation.

A method for the functionalization of carbon nanotubes with structure-tunable polymeric encapsulation layers and structural characterization using small-angle neutron scattering is presented.

We demonstrate a protocol for single-walled carbon nanotube functionalization using thermo-sensitive PEO-PPO-PEO triblock copolymers in an aqueous ...

The Preparation and Properties of Thermo-reversibly Cross-linked Rubber Via Diels-Alder Chemistry

A method for using Diels Alder thermo-reversible chemistry as cross-linking tool for rubber products is demonstrated. In this work, a commercial ethylene-propylene rubber, grafted with maleic anhydride, is thermo-reversibly cross-linked in two steps. The pending anhydride moieties are first modified with furfurylamine to graft furan groups to the rubber backbone. These pendant furan groups are then cross-linked with a bis-maleimide via a Diels-Alder coupling reaction. Both reactions can be performed under a broad range of experimental conditions and can easily be applied on a large scale. The material properties of the resulting Diels-Alder cross-linked rubbers are similar to a peroxide-cured ethylene/propylene/diene rubber (EPDM) reference. The cross-links break at elevated temperatures (&#62; 150 &#176;C) via the retro-Diels-Alder reaction and can be reformed by thermal annealing at lower temperatures (50-70 &#176;C). Reversibility of the system was proven with infrared spectroscopy, solubility tests and mechanical properties. Recyclability of the material was also shown in a practical way, i.e., by cutting a cross-linked sample into small parts and compression molding them into new samples displaying comparable mechanical properties, which is not possible for conventionally cross-linked rubbers.

A simple two-step approach involving rubber modification and cross-linking yields fully reworkable, elastic rubber products.

A method for using Diels Alder thermo-reversible chemistry as cross-linking tool for rubber products is demonstrated. In this work, a commercial ...

Electrochemical Impedance Spectroscopy as a Tool for Electrochemical Rate Constant Estimation

Electrochemical impedance spectroscopy (EIS) was used for advanced characterization of organic electroactive compounds along with cyclic voltammetry (CV). In the case of fast reversible electrochemical processes, current is predominantly affected by the rate of diffusion, which is the slowest and limiting stage. EIS is a powerful technique that allows separate analysis of stages of charge transfer that have different AC frequency response. The capability of the method was used to extract the value of charge transfer resistance, which characterizes the rate of charge exchange on the electrode-solution interface. The application of this technique is broad, from biochemistry up to organic electronics. In this work, we are presenting the method of analysis of organic compounds for optoelectronic applications.

Electrochemical impedance spectroscopy (EIS) of species that undergo reversible oxidation or reduction in solution was used for determination of rate constants of oxidation or reduction.

Electrochemical impedance spectroscopy (EIS) was used for advanced characterization of organic electroactive compounds along with cyclic voltammetry (CV). ...

Raman and IR Spectroelectrochemical Methods as Tools to Analyze Conjugated Organic Compounds

In the presented work, two spectroelectrochemical techniques are discussed as tools for the analysis of the structural changes occurring in the molecule on the vibrational level of energy. Raman and IR spectroelectrochemistry can be used for advanced characterization of the structural changes in the organic electroactive compounds. Here, the step-by-step analysis by means of Raman and IR spectroelectrochemistry is shown. Raman and IR spectroelectrochemical techniques provide complementary information about structural changes occurring during an electrochemical process, i.e. allows for the investigation of redox processes and their products. The examples of IR and Raman spectroelectrochemical analysis are presented, in which the products of the redox reactions, both in solution and solid state, are identified.

A protocol of step-by-step Raman and IR spectroelectrochemical analysis is presented.

In the presented work, two spectroelectrochemical techniques are discussed as tools for the analysis of the structural changes occurring in the molecule ...

Using Cyclic Voltammetry, UV-Vis-NIR, and EPR Spectroelectrochemistry to Analyze Organic Compounds

Cyclic voltammetry (CV) is a technique used in the analysis of organic compounds. When this technique is combined with electron paramagnetic resonance (EPR) or ultraviolet-visible and near-infrared (UV-Vis-NIR) spectroscopies, we obtain useful information such as electron affinity, ionization potential, band-gap energies, the type of charge carriers, and degradation information that can be used to synthesize stable organic electronic devices. In this study, we present electrochemical and spectroelectrochemical methods to analyze the processes occurring in active layers of an organic device as well as the generated charge carriers.

In this article, we describe electrochemical, electron paramagnetic resonance, and ultraviolet-visible and near-infrared spectroelectrochemical methods to analyze organic compounds for application in organic electronics.

Cyclic voltammetry (CV) is a technique used in the analysis of organic compounds. When this technique is combined with electron paramagnetic resonance ...

Reactive Vapor Deposition of Conjugated Polymer Films on Arbitrary Substrates

We demonstrate a method of conformally coating conjugated polymers on arbitrary substrates using a custom-designed, low-pressure reaction chamber. Conductive polymers, poly(3,4-ethylenedioxythiophene) (PEDOT) and poly(3,4-propylenedioxythiophene) (PProDOT), and a semiconducting polymer, poly(thieno[3,2-b]thiophene) (PTT), were deposited on unconventional highly-disordered and textured substrates with high surface areas, such as paper, towels and fabrics. This reported deposition chamber is an improvement of previous vapor reactors because our system can accommodate both volatile and nonvolatile monomers, such as 3,4-propylenedioxythiophene and thieno[3,2-b]thiophene. Utilization of both solid and liquid oxidants are also demonstrated. One limitation of this method is that it lacks sophisticated in situ thickness monitors. Polymer coatings made by the commonly used solution-based coating methods, such as spin-coating and surface grafting, are often not uniform or susceptible to mechanical degradation. This reported vapor phase deposition method overcomes those drawbacks and is a strong alternative to common solution-based coating methods. Notably, polymer films coated by the reported method are uniform and conformal on rough surfaces, even at a micrometer scale. This feature allows for future application of vapor deposited polymers in electronics devices on flexible and highly textured substrates.

This paper presents a protocol for reactive vapor deposition of poly(3,4-ethylenedioxythiophene), poly(3,4-propylenedioxythiophene), and poly(thieno[3,2-b]thiophene) films on glass slides and rough substrates, such as textiles and paper.