Neat Films Research Articles

Charge Transport in Organic Semiconducting Crystals Exhibiting TADF: Insight from Quantum Chemical Calculations

Luminophores featuring thermally activated delayed fluorescence (TADF) are the workhorses of the third- and fourth-generation OLEDs. While these compounds have usually been used as dopants embedded in the host, non-doped TADF OLEDs have recently shown significant progress as well and have attained performances comparable to those of the host-dopant systems. For efficient operation of non-doped OLEDs, the charge transport in neat films and single crystals of TADF luminophores is important; however, this issue was nearly unexplored theoretically. In the current study, we calculated the charge-carrier mobilities in four single crystals of TADF luminophores that have different molecular packing motifs. Specifically, in one of them both the donor and acceptor moieties form uniform π-stacks, while in the others the donors (acceptors) show alternating lateral shifts along the stacks; the difference in the molecular packing resulted in the difference in the transfer integrals between the molecules. The reorganization energies differed as well by up to four times for the studied crystals. As a result, the charge mobilities varied from 0.001 to ~0.3 cm2/(V∙s), with the largest being predicted for the crystal of the luminophore that consisted of a rigid donor and acceptor. We anticipate that the results obtained will be useful in the design of TADF luminophores for non-doped OLEDs, OLETs, and other organic light-emitting devices.

Improving Electroluminescence Efficiency by Linear Polar Host Capable of Promoting Horizontal Dipole Orientation for Dopant.

In doped organic light-emitting diodes (OLEDs), the host materials play an important role in emitting layers. Most studies about host materials mainly focus on their energy levels and carrier transport behaviors, while less attention is paid to their influence on the dipole orientation of dopants, which closely associate with the light out-coupling efficiency (ηout ) of the device. Herein, a linear polar host material (l-CzTRZ) consisting of carbazole donor, triazine acceptor, and the conjugated para-terphenyl skeleton is developed and its crystal and electronic structures, thermal and electrochemical stabilities, optical property, and carrier transport ability are investigated. l-CzTRZ prefers ordered horizontal orientation and favors electron transport in neat film. More importantly, it can promote horizontal dipole orientation for the dopants via dipole-dipole interaction, furnishing an excellent horizontal dipole ratio of 91.5% and thus a high ηout of 43% for the phosphorescent dopant (PO-01-TB). Consequently, the OLED with l-CzTRZ host and PO-01-TB dopant attains state-of-the-art electroluminescence efficiencies of 135.5cd A-1 , 135.7 lm W-1 and 41.3%, with a small roll-off of 9.7% at 5000cdm-2 luminance. The presented significant impact of the host on the dipole orientation of the dopant shall enlighten the design of host materials to improve OLED performance.

Novel Ir(III) Complexes with NHC-Based Ancillary Ligands for Efficient Nondoped OLEDs

Nondoped organic light-emitting diodes (OLEDs) are of paramount importance for display and lighting applications owing to their advantages of facile fabrication and outstanding stability. However, nondoped OLEDs achieving extraordinary electroluminescence (EL) performance and low turn-on voltage (Von) remain sparse. Here, three Ir(III) complexes featuring N-heterocyclic carbene (NHC) auxiliary ligands functionalized with electron-deficient aromatic sulfonyl or phosphine oxide groups are reported as promising emitters for nondoped OLEDs. All Ir(III) complexes exhibit green emission with relatively high neat film efficiency. Although the photoluminescence spectra of three complexes reveal similarities, there are distinct differences in the nondoped EL performance. The nondoped device N3 based on tBu-Ir-ISO displays the most eminent EL performances and presents a low Von of 2.1 V, a power efficiency of 30.7 lm W-1, and a maximum current efficiency of 27.0 cd A-1, which can be attributed to steric hindrance and balanced carrier-transporting ability induced by electron-deficient substituents. Moreover, doped devices D1-D3 also realize excellent EL performance. It is believed that the strategy reported herein is a simple and efficient way of constructing excellent Ir(III) complexes for nondoped phosphorescent OLEDs.

Achieving high-performance non-doped sky-blue OLEDs with negligible efficiency roll-off by combining AIE, HLCT and mechanoluminescence features

The hot exciton materials with high-lying reverse intersystem crossing provide great potential for the realization of efficient, low-cost and stable organic light-emitting diodes (OLEDs). However, it is highly desired but still challenging to achieve high-performance non-doped blue OLEDs with hot exciton luminogens. In this work, a new hybridized local and charge transfer (HLCT) luminogen 2-(4-(2-(4-(1,2,2-triphenylvinyl)phenyl)-1H-phenanthro[9,10-d]imidazole-1-yl)phenyl)phenanthro[9,10-d]oxazole (abbreviated as TPE-PI-PO) with the incorporation of tetraphenylethylene is obtained for constructing the high-performance non-doped blue OLEDs. TPE-PI-PO possesses the multifunctional features of aggregation-induced emission (AIE), HLCT and mechanoluminescence with high photoluminescence quantum yield (58%) in the neat film. The non-doped OLEDs based on TPE-PI-PO exhibits sky-blue emission, high luminance of 13,020 cd m−2 and the maximum efficiencies of 11.62 cd A−1, 5.08% with the negligible efficiency roll-off as low as 1.6% at 1000 cd m−2. The electroluminescent performance is highly competitive with the best reported non-doped blue fluorescent OLEDs based on AIE luminogens. These results can shed light on a feasible design principle to develop high-quality HLCT-type luminogens for high-performance non-doped blue OLEDs.

Modified Intramolecular‐Lock Strategy Enables Efficient Thermally Activated Delayed Fluorescence Emitters for Non‐Doped OLEDs

The development of intramolecular-lock strategy is an appealing task for designing efficient thermally activated delayed fluorescence (TADF) molecules, but only limited examples have been reported so far. Herein we present a "medium ring"-lock strategy to develop TADF emitters for improving the efficiency of organic light-emitting diodes (OLEDs). The installation of an electron-deficient heptagonal diimide lock onto a highly rotatable biphenyl-based emitter not only enhances electron-withdrawing ability of acceptor that decreases singlet-triplet energy gap (ΔEST ), but also endows the skeleton with modest rigidity and flexibility that increases photoluminescence quantum yield (PLQY) in neat film. In particular, the integration of the diimide lock also leads to an increase in horizontal orientation factor (Θ// ) from 69 % to 83 %. Consequently, this modified intramolecular-lock strategy enables an efficient TADF emitter to assemble high-performance non-doped OLEDs with a high external quantum efficiency of 26.2 % and a power efficiency of 76.6 lm W-1 .

Modified Intramolecular‐Lock Strategy Enables Efficient Thermally Activated Delayed Fluorescence Emitters for Non‐Doped OLEDs

AbstractThe development of intramolecular‐lock strategy is an appealing task for designing efficient thermally activated delayed fluorescence (TADF) molecules, but only limited examples have been reported so far. Herein we present a “medium ring”‐lock strategy to develop TADF emitters for improving the efficiency of organic light‐emitting diodes (OLEDs). The installation of an electron‐deficient heptagonal diimide lock onto a highly rotatable biphenyl‐based emitter not only enhances electron‐withdrawing ability of acceptor that decreases singlet‐triplet energy gap (ΔEST), but also endows the skeleton with modest rigidity and flexibility that increases photoluminescence quantum yield (PLQY) in neat film. In particular, the integration of the diimide lock also leads to an increase in horizontal orientation factor (Θ//) from 69 % to 83 %. Consequently, this modified intramolecular‐lock strategy enables an efficient TADF emitter to assemble high‐performance non‐doped OLEDs with a high external quantum efficiency of 26.2 % and a power efficiency of 76.6 lm W−1.

Biodegradable Poly(Butylene Succinate) Nanocomposites Based on Dimeric Surfactant Organomodified Clays with Enhanced Water Vapor Barrier and Mechanical Properties.

Biocomposites based on biodegradable polybutylene succinate (PBS) and organomodified clays (OMt) were prepared by melt blending process. The OMt nanofillers were obtained by ion exchange reaction between sodium montmorillonite (Mt) and gemini surfactants bearing 4-decyloxyphenylacetamide hydrophobic chains and ethylene or hexylene spacer. X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and rheological measurement results showed that the investigated hybrids present a uniform dispersion with an exfoliation of clay into the PBS matrix, particularly for short spacer surfactant based composites. The effect of organoclay loading and composition on the thermal, mechanical, and barrier properties was also investigated. High clay loading and long gemini surfactant spacer lead to substantial improvement of Young modulus values by 21%, while low clay content induces a reduction of the hybrid's crystallinity due to strong OMt-PBS interactions. Compared to that of the neat PBS film, a significant reduction of the water vapor permeability (WVP) by 28% was obtained by adding only 3 wt % of PBS/OMt (2) which opens up prospects for this material in the field of food packaging. This study shows that gemini surfactant-modified organoclays can be used as effective nanofillers in a PBS matrix to access to value-added nanocomposites.

Fabrication, characterisation, and application of green crosslinked sodium alginate hydrogel films by natural crab-shell powders to achieve drug sustained release

In this study, natural crab-shell particles (CSP) and deacetylated crab-shell particles (dCSP) were used as crosslinking agents at the present of glucolactone to obtain high strength mono-crosslinked and bi-crosslinked sodium alginate (NaAlg) hydrogel films, respectively. The results indicated that the CSP in the system could occur Ca2+ crosslinking, and the addition of dCSP could help to form both Ca2+ crosslinking and polyelectrolytes interactions with NaAlg. The remaining unreacted CaCO3 could enhance the thermal stability of the films due to the high thermally stable CaCO3. The surface hydrophobicity, gel properties, mechanical strength and thermal stabilities of those bi-crosslinked NaAlg hydrogel films were better than those of neat NaAlg film and mono-crosslinked NaAlg hydrogel films, which overcome the inferior thermo-mechanical properties for traditional hydrogel films. In addition, the releasing time of those prepared hydrogel films for diclofenac sodium was higher than 36 h, which illustrated sustained drug releasing activity. The CSP modified NaAlg hydrogel film with 0.5% GDL content exhibited the highest cumulative release amount. The proposed approach is a promising green crosslinking technique to develop high performance NaAlg hydrogel films that can realize active ingredients and drugs sustained release in food packaging and medical wound dressing areas.

Approaching 800 nm near-infrared thermally activated delay fluorescence materials via simple malononitrile condensation strategy

The development of organic materials with near-infrared (NIR) thermally activated delayed fluorescence (TADF) has drawn growing attention in recent years, but most of the reported NIR TADF emitters have emission peaks less than 780 nm with considerable visible emission remnants. To achieve pure NIR emission, we developed a strong electron acceptor fluoren-9-ylidene malononitrile ( FM ) by malononitrile condensation with fluorenone. Exploiting FM as acceptor, two novel molecules 3TPAFM and 36DTPAFM with pure NIR TADF were facilely synthesized and displayed high thermal stability. Compared with the orange emissive non-TADF fluorenone precursors, 3TPAFM and 36DTPAFM demonstrated significantly red-shifted emission of up to 217 nm and largely reduced energy gaps between the lowest singlet and triplet states, leading to pure NIR TADF with emission peak at 802 nm in neat films. The photophysical study revealed that their nonradiative decay rates are comparable with fluorenone counterparts even with such significantly reduced optical energy gap, manifesting largely attenuated limitation from the energy gap law. The non-doped OLEDs based on 3TPAFM and 36DTPAFM achieved pure NIR emission with λ EL at 792 and 788 nm, and external quantum efficiencies of 0.21% and 0.32% at 1 mA cm −2 , respectively. This work provides a simple and powerful strategy to achieve NIR TADF by malononitrile condensation with ketone group and presents FM group as a desirable acceptor candidate to construct pure and efficient NIR emitting materials. • Two novel NIR TADF emitters were constructed through simple malononitrile condensation strategy. • They achieved significant redshifts of 217 nm while maintaining similar nonradiative decay rates with fluorenone precursors. • Their non-doped OLED devices realized pure and efficient NIR emission with peaks around 790 nm.

Synthesis and Characterization of Lignin-Incorporated Carboxymethyl Cellulose (CMC) Films from Oil Palm Lignocellulosic Waste

An environmentally friendly, biobased film was prepared from cellulose and lignin extracted from oil palm dried long fiber (DLF). DLF crude cellulose was first extracted from this lignocellulosic biomass by an alkaline pretreatment process at an elevated temperature (5.75 wt% NaOH, 200 °C, and 1 h), before it was carboxymethylated to obtain carboxymethyl cellulose (CMC). CMC is highly soluble in water, whereas lignin was precipitated out of the filtrate of the alkaline pretreatment process by adding acid to pH 2 (50 wt% H2SO4). The lignin/CMC films were synthesized at varying lignin concentrations of 0.25%, 0.5%, and 1% (w/v) in ethanolic solution with 0.25% (v/v) of glycerol; a neat CMC film was also prepared as a control. These lignin/CMC films were evaluated and compared for their morphological, physical, chemical, and thermal characteristics. The films displayed a brownish physical appearance, which was attributed to the natural color of lignin. The successful incorporation of lignin in the films was confirmed with the characteristic spectral bands of lignin in the mid-IR range (4000–400 cm−1). When measured with UV-vis spectrometer, the lignin/CMC films showed more enhanced UV blocking properties than the neat CMC film. The CMC films incorporated with lignin also showed slightly improved hydrophobicity and thermal stability. However, due to the low compatibility of lignin with CMC, the distribution of the lignin/CMC film was observed to be inhomogeneous in SEM images. Nonetheless, the addition of lignin to CMC in synthesizing biobased films is promising, potentially providing better properties that can be useful as biodegradable material.

D–π–A–π–D-type Fluorophores based on Pyridal[2,1,3]thiadiazole acceptor with hybridized local and charge-transfer excited-state for high-efficiency OLEDs

Hybridized local and charge-transfer (HLCT) excited-state fluorophores, which are characterized by high photoluminescence quantum yield (PLQY) and reverse intersystem crossing (RISC) from high-lying triplets to singlets, has emerged advantages in organic light-emitting diodes (OLEDs) application. Although blue and green HLCT fluorophores are well developed, the long wavelength ones (orange to red) are still behind. Here, based on more electron-deficient Pyridal[2,1,3]thiadiazole (PT) acceptor, a D–π–A–π–D-type HLCT emitter, namely 2CZP-PT, with orangered emission is designed and synthesized. Due to the less steric hindrance of pyridine nitrogen in PT, a small twist angle between the π bridge and acceptor on the nitrogen side is obtained, which endows the whole molecule with relative planar conformation. Thus 2CZP-PT exhibits HLCT characteristics with high PLQY (77% in THF solution and 44% in neat film), as well as energy levels arrangement favoring the RISC process from high-lying triplet levels to singlet levels. The doped devices based on 2CZP-PT reached a maximum external quantum efficiency (EQEs) of 9.57% with an electroluminescence (EL) peak at 568 nm. While the non-doped OLEDs based on 2CZP-PT emitter achieved a maximum EQEs of 1.34% with red EL peaked around 600 nm, whose efficiency roll-off is only 1.5% at 1000 cd m−2. These device performances demonstrate PT based D–π–A–π–D-type fluorophores are promising for their long-wavelength OLEDs application.

Donor-σ-acceptor molecules with alkyl σ-linkers of different lengths: Exploration on the exciplex emission and their use for efficient organic light-emitting diodes

Donor-σ-acceptor molecules featuring exciplex emission have been extensively researched for developing thermally-activated delayed fluorescence; however, varying the length of alkyl σ-linker to explore the exciplex emission and to develop efficient exciplex emitters has not been fully conducted. Herein, we report donor-σ-acceptor exciplex emitters (1–3) developed with 9,9-dimethyl-10-phenyl-9,10-dihydroacridine donor, 2,4,6-triphenyl-1,3,5-triazine acceptor, and alkyl σ-linkers of different lengths (−CH2− for 1, –CH2CH2− for 2, and –CH2CH2CH2− for 3). The chemical structures of 1–3 have been verified by X-ray crystallography. Theoretical calculations reveal that intramolecular through-space charge transfer is the dominant charge-transfer mechanism within the molecules. In dilute solution and the films with low concentration of the dopant, intramolecular exciplexes are formed, whereas in the films with high concentration of the dopant, both intra- and inter-molecular exciplexes are formed. 1–3 all show aggregation-induced emission properties. In heavily doped or neat films, 1–3 show sky-blue emission with photoluminescent efficiency of up to 0.70 and high reverse intersystem crossing rates of up to 5.1 × 106 s−1. It is shown that varying the length of alkyl σ-linker regulates the thermally-activated delayed fluorescence of the exciplex formed in neat film. Vacuum-evaporated and solution-processed organic light-emitting diodes using 1–3 as the emitters show sky-blue and blue electroluminescence with peak external quantum efficiencies of up to 14.5% and 13.0%, respectively. The efficiency is among the highest for solution-processed blue organic light-emitting diodes based on small-molecule exciplex emitters reported so far.

Use of orange juice processing waste to produce films using blown film extrusion for food packaging

Orange peel (OP) is a by-product from citrus juicing that is wasted. Conversion of this waste into plastic filler can help reduce environmental problems. OP has been incorporated into plastics to form biocomposites using compression molding, injection molding, and casting. However, blown film extrusion, the most common manufacturing process for plastic films has not been investigated yet. The aims of this study were: (1) to produce linear low density polyethylene (LLDPE)/OP films using blown film extrusion, (2) to determine the maximum OP amount that can be used to replace plastic through blown film production, and (3) to assess the effect of OP amount on film morphology and properties. LLDPE/OP masterbatch pellets were produced and combined with neat LLDPE using specific processing parameters determined to produce blown LLDPE/OP composite films differing in OP content (5, 10, 11.5, and 12.5%). The morphology, thickness, and mechanical, barrier, optical and thermal properties of the blown composite films and neat films were compared. The results show that LLDPE/OP films containing up to 11.5% OP can be produced through blown film extrusion. These films have similar (p > 0.05) water barrier, crystallinity, and melting temperature, but lower tensile strength and elongation at break than neat LLDPE films. OP loading enhanced the UV and visible light blocking capacity of the films. This study revealed that blown LLDPE/OP films are suitable for food packaging.

Processing Compostable PLA/Organoclay Bionanocomposite Foams by Supercritical CO2 Foaming for Sustainable Food Packaging.

This article proposes a foaming method using supercritical carbon dioxide (scCO2) to obtain compostable bionanocomposite foams based on PLA and organoclay (C30B) where this bionanocomposite was fabricated by a previous hot melt extrusion step. Neat PLA films and PLA/C30B films (1, 2, and 3 wt.%) were obtained by using a melt extrusion process followed by a film forming process obtaining films with thicknesses between 500 and 600 μm. Films were further processed into foams in a high-pressure cell with scCO2 under constant conditions of pressure (25 MPa) and temperature (130 °C) for 30 min. Bionanocomposite PLA foams evidenced a closed cell and uniform cell structure; however, neat PLA presented a poor cell structure and thick cell walls. The thermal stability was significantly enhanced in the bionanocomposite foam samples by the good dispersion of nanoclays due to scCO2, as demonstrated by X-ray diffraction analysis. The bionanocomposite foams showed improved overall mechanical performance due to well-dispersed nanoclays promoting increased interfacial adhesion with the polymeric matrix. The water uptake behavior of bionanocomposite foams showed that they practically did not absorb water during the first week of immersion in water. Finally, PLA foams were disintegrated under standard composting conditions at higher rates than PLA films, showing their sustainable character. Thus, PLA bionanocomposite foams obtained by batch supercritical foaming seem to be a sustainable option to replace non-biodegradable expanded polystyrene, and they represent a promising alternative to be considered in applications such as food packaging and other products.

Synergistic effect of hybrid hydroxylated boron nitride and cellulose nanocrystals for enhancing the thermal, mechanical, and hydrophobic properties of composite film

AbstractHybrid composite films are largely preferred over neat films because of their superior thermal, mechanical, chemical, and hydrophobic properties. The hybrid composite film has a wide range of use, including space, defense, electronics, packaging, and engineering applications. Fabricating multifunctional hybrid composite films with biodegradable polymer and biodegradable filler such as cellulose nanocrystals has become popular in recent years as an alternative to conventional plastics. In this paper, hybrid hydroxylated boron nitride (BN) nanoparticles with CNC nano‐filer reinforced composite PVA films were fabricated. The obtained composite films were characterized for morphological, chemical, physical, thermal, and hydrophobic properties. The morphological analysis indicates that the hybrid nano‐filler was well dispersed in the poly(vinyl alcohol) (PVA) matrix. The reaction and hydrogen bond interactions between CNC and BN in composite films are confirmed by the Fourier transform infrared spectroscopy and x‐ray diffraction pattern. The contact angle method is used to confirm the enhancement of the hydrophobic property. The physical properties of the composite films and neat PVA film were analyzed by tensile test method using a universal testing machine. The thermal stability of the neat PVA film and the composite films were analyzed by the thermo‐gravimetric analysis method. The effect of hybridization of nanoparticles on the thermal, mechanical, and hydrophobic properties was studied. The hybrid composite film with enhanced properties allows it for multifunctional applications.

Regioisomer‐Free Difluoro‐Monochloro Terminal‐based Hexa‐Halogenated Acceptor with Optimized Crystal Packing for Efficient Binary Organic Solar Cells

AbstractHerein, we synthesized new hetero‐halogenated end groups with well‐determined fluorinated and chlorinated substitutions (o‐FCl‐IC and FClF‐IC), and synthesized regioisomer‐free small molecular acceptors (SMAs) Y‐Cl, Y‐FCl, and Y‐FClF with distinct hetero‐halogenated terminals, respectively. The single‐crystal structures and theoretical calculations indicate that Y‐FClF exhibits more compact three‐dimensional network packing and more significant π‐π electronic coupling compared to Y‐FCl. From Y‐Cl to Y‐FCl to Y‐FClF, the neat films exhibit a narrower optical band gap and gradually enhanced electron mobility and crystallinity. The PM6 : Y‐FClF blend film exhibits the strongest crystallinity with preferential face‐on molecular packing, desirable fibrous morphology with suitable phase segregation, and the highest and balanced charge mobilities among three blend films. Overall, the PM6 : Y‐FClF organic solar cells (OSCs) deliver a remarkable efficiency of 17.65 %, outperforming the PM6 : Y‐FCl and PM6 : Y‐Cl, which is the best PCE for reported hetero‐halogens‐based SMAs in binary OSCs. Our results demonstrate that difluoro‐monochloro hetero‐terminal is a superior regio‐regular unit for enhancing the intermolecular crystal packing and photovoltaic performance of hetero‐halogenated SMAs.

Regioisomer-Free Difluoro-Monochloro Terminal-based Hexa-Halogenated Acceptor with Optimized Crystal Packing for Efficient Binary Organic Solar Cells.

Herein, we synthesized new hetero-halogenated end groups with well-determined fluorinated and chlorinated substitutions (o-FCl-IC and FClF-IC), and synthesized regioisomer-free small molecular acceptors (SMAs) Y-Cl, Y-FCl, and Y-FClF with distinct hetero-halogenated terminals, respectively. The single-crystal structures and theoretical calculations indicate that Y-FClF exhibits more compact three-dimensional network packing and more significant π-π electronic coupling compared to Y-FCl. From Y-Cl to Y-FCl to Y-FClF, the neat films exhibit a narrower optical band gap and gradually enhanced electron mobility and crystallinity. The PM6 : Y-FClF blend film exhibits the strongest crystallinity with preferential face-on molecular packing, desirable fibrous morphology with suitable phase segregation, and the highest and balanced charge mobilities among three blend films. Overall, the PM6 : Y-FClF organic solar cells (OSCs) deliver a remarkable efficiency of 17.65 %, outperforming the PM6 : Y-FCl and PM6 : Y-Cl, which is the best PCE for reported hetero-halogens-based SMAs in binary OSCs. Our results demonstrate that difluoro-monochloro hetero-terminal is a superior regio-regular unit for enhancing the intermolecular crystal packing and photovoltaic performance of hetero-halogenated SMAs.

Hybrid Films from Blends of Castor Oil and Polycaprolactone Waterborne Polyurethanes.

Waterborne polyurethanes (WBPUs) with relatively high biobased content (up to 43.7%) were synthesized, aiming at their use as coatings for metals and woods. The study was performed on self-standing films obtained from anionic polyurethane water dispersions (PUDs). The initially targeted PUD was prepared from castor oil (CO), while tartaric acid (TA), a byproduct of wine production, was utilized as the internal anionic emulsifier. Although the films were cohesive and transparent, they were fragile, and thus blending the CO-TA PUD with other WBPUs was the chosen strategy to obtain films with improved handling characteristics. Two different WBPUs based on polycaprolactone diol (PCL), a biodegradable macrodiol, were prepared with dimethylolpropionic acid (DMPA) and tartaric acid (TA) as synthetic and biobased internal emulsifiers, respectively. The use of blends with PCL-TA and PCL-DMPA allowed for tailoring the moduli of the samples and also varying their transparency and haze. The characterization of the neat and hybrid films was performed by colorimetry, FTIR-ATR, XRD, DMA, TGA, solubility and swelling in toluene, and water contact angle. In general, the addition of PCL-based films increases haze; reduces the storage modulus, G’, which at room temperature can vary in the range of 100 to 350 MPa; and reduces thermal degradation at high temperatures. The results are related to the high gel content of the CO-TA film (93.5 wt.%), which contributes to the cohesion of the blend films and to the crystallization of the PCL segments in the samples. The highest crystallinity values corresponded to the neat PCL-based films (32.3% and 26.9%, for PCL-DMPA and PCL-TA, respectively). The strategy of mixing dispersions is simpler than preparing a new synthesis for each new requirement and opens possibilities for new alternatives in the future.

Active Packaging Films Made by Complex Coacervation of Tragacanth Gum and Gelatin Loaded with Curcumin; Characterization and Antioxidant Activity.

The development of biopolymer-based green packaging films has gained remarkable attention in recent years. In this study, curcumin active films were prepared using different proportions of gelatin (GE) and a soluble fraction of tragacanth gum (SFTG) (1GE:1SFTG and 2GE:1SFTG) by complex coacervation. The various ratios of used biopolymers did not significantly impact the mechanical properties, thickness, and WVP of final films. However, biopolymers’ ratio impacted the moisture content, water solubility, swelling ratio, and release rate. Blending curcumin with biopolymers caused a reduction in tensile strength (from 1.74 MPa to 0.62 MPa for film containing 1GE:1SFTG and from 1.77 MPa to 0.17 MPa for film containing 2GE:1SFTG) and proliferation in elongation at break (from 81.48% to 122.00% for film containing 1GE:1SFTG and from 98.87% to 109.58% MPa for film containing 2GE:1SFTG). Moisture content and water solubility of films experienced a decrease after the addition of curcumin. Antioxidant activity of curcumin-loaded films was almost five times higher than neat film samples. Furthermore, the interreaction between the carboxylic group of SFTG and amide I of GE formed an amide linkage and was proven by FTIR analysis. TGA showed a drop in the thermal stability of film samples compared to the main ingredients. In general, the complex coacervate of SFTG and GE has the advantage of developing eco-friendly and low-cost packaging film in the food industry, especially for the protection of fatty foods.

Chiral‐at‐Cage Carboranes for Circularly Polarized Luminescence and Aggregation‐Induced Electrochemiluminescence

AbstractHerein, we report the structures of chiral‐at‐cage carborane derivatives bearing carbazole chromophores that emit circularly polarized luminescence (CPL) and aggregation‐induced electrochemiluminescence (AIECL). By adjusting the substituent positions on the carborane derivatives, two chiral luminescent molecules, Cb1 and Cb2, with different properties were obtained. The photoluminescence dissymmetry factors |gPL| of both (R/S)‐Cb1 and (R/S)‐Cb2 enantiomers in neat films were as high as 6.24×10−3 and 7.38×10−3, respectively. Cb1 showed a deep blue emission peak at 434 nm in n‐pentane. Interestingly, distinct fluorescence and CPL spectra were observed in solvents of different polarities due to the twisted intramolecular charge transfer effect, suggesting its potential use in solvent recognition. Meanwhile, Cb2 exhibited good AIECL property, excellent ECL stability and could be used for determining dopamine concentrations, suggesting its potential applications in biology and diagnosis.