A scalable methodology to perform miniemulsion polymerizations is demonstrated for the polymerization of methyl methacrylate (MMA). Scalability of the miniemulsification was achieved by using a spinning disk reactor, which provides the required energy input to form a metastable emulsion, yielding miniemulsion droplets with an average size of 154 nm and a PDI of 0.17. Polymerization proceeds likewise in a scalable fashion, achieved by using agitated continuous flow reactors, which effectively prevent reactor fouling, a problem that typically limits emulsion polymerization in continuous flow. For the MMA miniemulsion process, synthesis of over 100g of polymer particles with well-defined particle distributions (the average polymer particle size, obtained after polymerization in the ATR reactor following emulsification using the SDR, was 170 nm with a PDI of 0.10) has been achieved, and operation of the designed reactor setup is stable over an entire workday. The space-time yield of the miniemulsion was found to be 53 g/Lh, significantly outperforming previous methods of miniemulsion polymerization.

Here, we present two series of new electroactive compounds containing electron donors (carbazolyl) and electron acceptor (pyridinyl) fragments as potential host materials. The objective compounds 9-(2-ethylhexyl)-3,6-di [3-(methoxypyridin-3-yl)carbazol-9-yl]carbazoles RB71 and RB74 were synthesized by an Ullmann coupling reaction between the intermediate derivatives: 9-(2-ethylhexyl)-3,6-diiodocarbazole and corresponding 3-(methoxypyridin-3-yl)-9H-carbazole. Other target derivatives, 9-alkyl-3-[N-(9-alkylcarbazol-3-yl)-N-(4-methylpyridin-2-yl)amino]carbazoles RB70 and RB75, were also prepared, according to the Ullmann reaction method, from 2-amino-4-methylpyridine and the corresponding 3-iodo-9-alkylcarbazole. Thermogravimetric analysis confirmed that the new derivatives are highly thermally stable compounds, with 5% weight loss in the temperature range of 349 °C to 488 °C. According to differential scanning calorimetry results, some amorphous materials exhibit very high glass transition temperatures exceeding 150 °C in some cases, which is a significant advantage for compounds with potential applications in organic light-emitting devices. The electroluminescent properties of devices utilizing the new hosts RB71 or RB70 with 5.0, 10.0, 15.0, and 20.0 wt.% concentrations of the dopant tris(2-phenylpyridine)iridium(III), Ir(ppy)3, were demonstrated. All the PhOLEDs emitted light at approximately 515 nm with CIE coordinates of (0.30, 0.61) due to Ir(ppy)3 emissions. The most efficient device with RB71 host demonstrated a maximum power efficacy of 8.0 lm/W, maximum current efficiency of 12.7 cd/A, and maximal external quantum efficiency of 5.4% with a relatively low turn-on voltage of 4.3 eV, as well as luminance exceeding 4000 cd/m2. Additionally, 15 wt.% Ir(ppy)3 emitter-based PhOLED with RB70 host outperformed the other devices by displaying a maximum power efficacy of 9.6 lm/W, maximum current efficiency of 16.0 cd/A, and maximal external quantum efficiency of 6.7% with a relatively low turn-on voltage of 3.7 eV, as well as luminance reaching 11,200 cd/m2. Some devices seem to exhibit higher efficiencies than those previously reported for OLEDs that utilize a 4,4′-bis(9-carbazolyl)-2,2′-biphenyl (CBP) host.

Biopolymers such as gelatin, hyaluronic acid, and chitin are used in the form of hydrogels as scaffolds for tissue engineering and as bioinks for bioprinting. The biopolymers themselves tend to be weak and hence are usually chemically functionalized to improve their stability and tenacity. The chemical functionalization is currently conducted using batch methods, which are time-consuming, difficult to scale up, and have batch-to-batch variation. Flow chemistry, on the other hand, is more efficient, safer, reproducible, easy to scale up, and can give much higher space-time yields compared to batch reactions. In this study, a flow chemistry protocol was developed for the synthesis of the commonly used biomaterial gelatin methacrylate (GelMA), and the resulting GelMA was used in bioprinting and as a hydrogel in cell culture studies to investigate its ability to support cell attachment and expansion. It was found that conversion of gelatin into GelMA proceeded rapidly and optimally at 60 degrees C, giving reproducible and high degrees of substitution (65-85%) and high yields in up to 20 minutes of reaction. Scale-up of the reaction was also demonstrated. The resulting GelMA was characterized by oscillatory shear rheometry and was found to be capable of extrusion bioprinting, yielding self-supporting and defect-free hydrogel patterns. The GelMA hydrogels were also found to be able to support the proliferation of primary endometrial cells over 6 days of culture. The GelMA produced by flow chemistry, therefore, was shown to be suitable for use as a bioink and as a hydrogel substrate for cell culture, demonstrating the potential of flow chemistry as an efficient method to produce biomaterials for bioprinting and tissue engineering applications.

Charge carrier doping of conjugated polymers holds great promise for enhancing electronic and optoelectronic properties, yet, a comprehensive understanding of the electronic structure of doped polymers remains elusive. Herein, we employ transient absorption spectroscopy to investigate a prototypical conjugated polymer, defect-free poly-3-hexylthiophene (DF-P3HT), at varying degrees of hole-doping across a range of wavelengths to account for the representative model of its electronic structure. Our findings elucidate an underlying dynamic dopant-polymer interaction, revealing the formation and evolution of ion-bound charge carriers on femtosecond-to-nanosecond time scales. At low dopant concentrations, efficient charge separation forms free polarons, which contribute to an enhanced current. However, as dopant concentrations increase, we observe a marked transition from free polarons to bound polaronic states, identified for the first time by an unequivocal absorption spectrum, which is similar to 1400 cm-1 red-shifted with respect to the free polaron transient absorption feature. This shift is attributed to the saturation of doping sites leading to substantial Coulombic interactions, Stark effect diminished charge mobility due to localization, and increased recombination losses. Our work in identifying ion-bound polaron signature offers a pathway to optimize doping strategies for improved performance in organic electronic devices, and hints at a band-bending model for polaronic transitions.

The current academic study focuses on analysis and synthesization of a high density, high refractive indexed heavy metal oxide pigmented heat absorbent sodium silicate glass system xPbO-y(0.14Cu2O-0.05CuO-0.03SnO2) -30Na2O-(70-0.22y-x)SiO2 (x= 0,1.5,10 mol% and y = 0,1) explored with various ratios PbO doping via conventional melt annealing route, resulted optimally suited material for various linear and nonlinear optoelectronic applications. The fundamental physio-mechanical properties like density(ρ), molar volume(V_m ), and oxygen packing density (OPD) of synthesized samples were analyzed, alongside elastic moduli were computed utilizing experimental, Makishima-Mackenzie, & Rocherulle models. When the XRD data verified the substance's amorphous character, the FTIR study specified the vibrational bands associated with the silicate matrix’s structure. The visible optical properties, solar optical properties, refractive index (n), extinction coefficient (k) optical dielectric constants, direct &indirect optical band gap, and Urbach energy (〖 E〗_( U) ) were measured from computed spectral data collected by Jasco V-770 spectrophotometer in the solar spectrum wavelength spanning 190 nm - 1100 nm, as a result, the computed indirect optical band gap energy (E_gind ) and, direct optical band gap energy (E_gd ) were illustrated to be in the 1.64-2.61 and, 2.57-3.03 eV range respectively. Using the absorption spectra, the average of refraction index (n_0 ), corresponding nonlinear refractive index (n_( 2) ), molar refraction (R_( m) ), polarizability (α_m ), reflection loss (R_L ), optical transmission (T), metallization criterion (M_c ), optical electronegativity (〖Δχ〗^* ), third order nonlinear optical susceptibility(χ^((3)) ) have all been calculated, whereas the beneficiary parameter, optical basicity (Λ_th) has been also evaluated. All the above characterizations have been established and explored, paving the road for the created product to be an acceptable option for commercial construction, especially for exterior use in high-light areas as well as optoelectronic devices.

Different approaches have been introduced to raise the response speed of bulk heterojunction-based organic photodiodes (OPDs), with the best-performing devices now having speeds in the MHz range. In most organic photodiodes, the response speed is commonly assumed to be due to transit time of charge carriers. Upon investigating fluence-dependent photoresponse of different OPDs, it is found here that bimolecular recombination dictates the response speed at higher fluence levels. Herein, four different organic blend based photodiode systems and their response speed to a range of incident optical fluences are reported. A steep variation in response speed, depending upon the blend system is observed. Using experimental and theoretical studies, the intensity-dependent response speeds are attributed to differences in the suppressed recombination factor. A high factor enables faster response times in the regime of higher light intensity. This new approach to high-speed detections has implications for the design of high-speed organic photodetectors, especially in applications where the speed of the photodetector is most important irrespective of the intensity of the incident signal. It is experimentally observed through this work that organic photodiode response speed is strongly dependent on the excitation fluence. Using a time-delayed collection field, it is found that the suppressed recombination factor dictates the response speed of the photodiode at higher fluence levels. image

We report a continuous flow method for the process intensification of commercially important propylenediox-ythiophene (ProDOT) monomers. A new four-step synthetic route was designed to make the whole process more economical and continuous flow amenable. Apart from being safe and having a higher throughput via continuous flow, we could optimize each of the synthetic steps to quantitative conversion. GC-MS analysis was used to monitor each of the processes during optimization. The overall process could be completed in around 65 min, starting from the commercially available materials, as compared to the few days via the reported batch processes. Furthermore, we have shown that the most critical step of the Williamson etherification could be intensified via continuous flow to the space-time yield (STY) of 63 g/h/L as compared to 0.16 g/h/L via the traditional batch process. As all the synthetic steps in our continuous flow process were optimized to quantitative conversions, it opens up the possibility of telescoping of the whole process. We believe that our findings will be able to fill the existing gap in the process intensification for the synthesis of commercially important ProDOT-based monomers.

Continuous flow chemistry offers an exceptionally high degree of operational flexibility to handle photochemical transformations.

A one-pass continuous flow strategy to form block copolymer nanoaggregates directly from monomers is presented. A key development towards such a sophisticated continuous flow setup is a significant improvement in continuous flow dialysis. Often impurities or solvent residues from polymerizations must be removed before block extensions or nanoaggregate formation can be carried out, typically disrupting the workflow. Hence, inline purification systems are required for fully continuous operation and eventual high throughput operation. An inline dialysis purification system is developed and exemplified for amphiphilic block copolymer synthesis from thermal and photoiniferter reversible addition fragmentation chain transfer (RAFT) polymerization. The inline dialysis system is found to be significantly faster than conventional batch dialysis and the kinetics are found to be very predictable with a diffusion velocity coefficient of 4.1 × 10−4 s−1. This is at least 4–5 times faster than conventional dialysis. Moreover, the newly developed setup uses only 57 mL of solvent for purification per gram of polymer, again reducing the required amount by almost an order of magnitude compared to conventional methods. Methyl methacrylate (MMA) or butyl acrylate (BA) was polymerized in a traditional flow reactor as the first block via RAFT polymerization, followed by a ‘dialysis loop’, which contains a custom-built inline dialysis device. Clearance of residual monomers is monitored via in-line NMR. The purified reaction mixture can then be chain extended in a second reactor stage to obtain block copolymers using poly(ethylene glycol) methyl ether acrylate (PEGMEA) as the second monomer. In the last step, nano-objects are created, again from flow processes. The process is highly tuneable, showing for the chosen model system a variation in nanoaggregate size from 34 nm to 188 nm.

Photogenerated polarons in π-conjugated polymers are the precursors to free charges at donor-acceptor interfaces. Unraveling the relationship between film morphology and polaron formation is conjectured to enable efficient charge generation in organic photovoltaic devices. However, it has been challenging to track the ultrafast dynamics of polarons selectively and thus evaluate the molecular coordinates that drive charge generation in films. Using a combination of broadband femtosecond transient absorption and resonance-selective femtosecond stimulated Raman spectroscopy, here, we investigate the polaron generation dynamics exclusively in traditional crystalline poly(3-hexylthiophene) (P3HT) and its amorphous side-chain variant poly(3-(2-ethylhexyl)thiophene-2,5-diyl) (P3EHT) films. The transient Raman data unequivocally provides evidence for an initial delocalization of the polaronic states via thiophene backbone planarization in ∼100 fs while capturing the subsequent morphology-dependent cooling dynamics in a few picoseconds. Our work highlights the structural significance of crystalline morphology in generating hot-charges and thereby emphasizes the importance of side-chain engineering in designing highly efficient conjugated polymer films for hot-carrier photovoltaic devices.

Scalable continuous flow synthesis of dendritic fibrous nanospheres of silica (DFNS).

In this manuscript, we report, for the first time, a direct C-H:C-H arylation process for the polymerization of 3,4-propylenedioxythiophene derivatives. The requirement of aryl halides monomers can be completely excluded in this process, making the process atom economical and environmentally friendly. We could successfully homopolymerize Prodot-diethylhexyl using palladium acetate as catalyst. The optimized process required the stepwise ramping of the temperature from 70 °C to 140 °C. It was also observed that a direct heating of the polymerization mixture to 140 °C results in the decomposition of the catalyst leading to unsuccessful polymerization. At present, the exact mechanism of the whole process is not clear.

We study the differences in electrical charge transport dynamics of the conductivity enhancement of poly(3,4-ethylenedioxythiophene) (PEDOT) derivatives under geometrical confinement. The results of polymer blend poly(3,4-ethylene dioxythiophene):poly(styrenesulfonate) and a polymer-monomer blend, poly(3,4ethylenedioxythiophene):tosylate, highlight the role of dopants and processing conditions of these systems under confinement. The prevailing transport length scales in confined geometry of characteristic dimensions originate from varying disorder in these polymer systems. These observable differences in two different PEDOTs introduced by molecular level reorganization can be utilized to tune conducting polymer systems for efficient electrical and thermoelectric properties. The electrical conductivity σ of the polymer system, which is a function of the electronic structure at molecular level and a connectivity parameter, has been probed in cylindrical-alumina nanoscaffolds of various channel diameters, at different frequencies ω and temperatures T. The observations also emphasize the role of disorder in these conducting polymer systems.

Dimethyl-2,5-bis[4-(methoxyphenyl)amino] terephthalate (DBMPT) exhibits aggregation-induced enhancement of emission with Tween 40 and formation of nanorods with strong orange fluorescence. These nanorods disrupt fibrils of human serum albumin and lead to partial refolding of the protein, as monitored by circular dichroism and thioflavin T (ThT) fluorescence. The resultant milieu emits white light, the mechanism of which is explored in this study. It is established that direct excitation of the acceptor plays a significant role, even though Förster resonance energy transfer (FRET) is found to be operative to some extent. A decrease in the fluorescence intensity and lifetime of ThT with progressive addition of DBMPT, which is often used as the sole indicator of FRET, is ascribed to the disruption of the fibrils by the nanorods.

The field of organic photodiodes (OPDs) has witnessed continuous development in the last decade. Although a considerable portion of electron‐donating materials are polymers, there has been an existential gap in deciphering the influence of the polymer's molecular‐weight on the photodiode performance. We take up OPDs based on 5,5′‐[(9,9‐Dioctyl‐9 H ‐fluorene‐2,7‐diyl)bis(2,1,3‐benzothiadiazole‐7,4diylmethylidyne)]bis[3‐ethyl‐2‐thioxo‐4‐thiazolidinone] (FBR) acceptor material blended with three different molecular‐weights of defect‐free form of a well‐known donor polymer poly(3‐hexylthiophene‐2,5‐diyl) (P3HT) are taken up, and their optoelectronic performance along with morphological characteristics are studied. Disparity of up to a decade in key photodetecting characteristics is observed. Further, the tools of near‐edge X‐ray absorption fine‐structure spectroscopy, resonant soft X‐ray scattering spectroscopy, atomic force microscopy, and time‐delayed collection‐field measurements are employed to decipher the difference in the fundamental photo‐physical processes and the operating mechanisms of the OPDs. It is concluded that the molecular weight and the resulting morphology of the active layer strongly influence photodiode performance, in particular, dark current, linear dynamic range, and specific‐detectivity.

The way in which conjugated polymers pack in the solid state strongly affects the performance of polymer-based optoelectronic devices. However, even for the most crystalline conjugated polymers the precise packing of chains within the unit cell is not well established. Here we show that by performing resonant X-ray diffraction experiments at the sulfur K-edge we are able to resolve the tilting of the planar backbones of crystalline poly(3-hexylthiophene) (P3HT) within the unit cell. This approach exploits the anisotropic nature of the X-ray optical properties of conjugated polymers, enabling us to discern between different proposed crystal structures. By comparing our data with simulations based on different orientations, a tilting of the planar conjugated backbone with respect to the side chain stacking direction of 30 ± 5° is determined.

Four batches of P3HT with varied molecular weight (MW) but constant regioregularity (RR) are investigated. When RR is fixed at 100%, solar cell efficiency is less sensitive to MW with high efficiencies achieved for as-cast devices.

The improvement of electron transport in polymer semiconductors is highly desirable for realizing robust, large-area and low-cost organic integrated circuits. This work investigates the effect of regioregularity on the intrinsic hole and electron transport characteristics of poly(3-hexylthiophene-2,5-diyl) (P3HT) using current-voltage (I-V) measurements in metal/polymer/metal sandwich structures. Through a direct comparison between 93% regioregular P3HT (EG-P3HT) and 100% regioregular defect-free poly(3-hexylthiophene-2,5-diyl) (DF-P3HT), it is found that the elimination of regioregularity defects improves the electron mobility of DF-P3HT (1.05 × 10-7 cm2 V-1 s-1) by three orders of magnitude compared to the 93% regioregular EG-P3HT sample (1.82 × 10-10 cm2 V-1 s-1). Quantum chemical calculations indicate that the improvement of electron mobility in DF-P3HT can be associated to the lower degree of disorder in these samples that tends to increase the transfer angle between the lowest unoccupied molecular orbitals of adjacent chains. At the same time, the lower dipole moments produced by the defect-free polymer molecules also appears to play an important role in decreasing the susceptibility of charge transport to environment-induced electron traps. The obtained results provide a strong evidence that the elimination of regioregularity defects is an effective technique to improve electron transport and restore the symmetry between hole and electron mobility in P3HT as well as other thiophene-based polymers.

It has been shown that light-matter strong coupling of materials can lead to modified and often improved properties which has stimulated considerable interest. While charge transport can be enhanced in n-type organic semiconductors by coupling the electronic transition and thereby splitting the conduction band into polaritonic states, it is not clear whether the same process can also influence carrier transport in the valence band of p-type semiconductors. Here we demonstrate for the first time that it is indeed possible to enhance both the conductivity and photoconductivity of a p-type semiconductor rr-P3HT that is ultra-strongly coupled to plasmonic modes. It is due to the hybrid light-matter character of the virtual polaritonic excitations affecting the linear-response of the material. Furthermore, in addition to being enhanced, the photoconductivity of rr-P3HT shows modified spectral response due to the formation of the hybrid polaritonic states. This illustrates the potential of engineering the vacuum electromagnetic environment to improve the opto-electronic properties of organic materials.

Dimethyl-2,5-bis(4-methoxyphenylamino)-terephthalate (DBMPT) is a water-insoluble fluorogenic molecule, which has been rendered water-soluble in physiological conditions, by the addition of triblock copolymers (TBPs), P123 PEO19 PPO69 PEO19), and F127 (PEO100PPO65PEO100). DBMPT-TBP mixed aggregates, formed in the process, exhibit significant aggregation-induced enhancement of emission, with nanosecond fluorescence lifetimes. Dynamics involved in suppression of nonradiative pathways and consequent enhancement of fluorescence are followed by femtosecond transient absorption and time-resolved fluorescence spectroscopic techniques. Interestingly, shapes of the aggregates formed with the two TBPs are found to be very different, even though they differ only in the length of hydrophilic blocks. DBMPT-P123 aggregates are micrometer-sized and spherical, while DBMPT-F127 aggregates form nanorods. Evolution of their morphologies, as a function of TBP concentration, is monitored using cryo-TEM, FESEM, and fluorescence lifetime imaging microscopy. Fluorescence lifetime distribution provides useful insight into microheterogeneity in these mixed aggregates. Excellent cell permeability is observed for DBMPT-F127 nanorods, in contrast to DBMPT-P123 microspheres. These fluorescent nanorods exhibit the ability to mark lipid droplets within the cell and hence bear the promise for application in intracellular imaging.