Solution-cast Films Research Articles

Cross-Linked Metathesis Polynorbornenes Based on Nadimides Bearing Hydrocarbon Substituents: Synthesis and Physicochemical Properties.

Metathesis homo- and copolymerization of bifunctional monomers bearing two norbornene moieties was studied. The monomers were synthesized from cis-5-norbornene-exo-2,3-dicarboxylic anhydride and various diamines (hexamethylenediamine, decamethylenediamine, 1R,3S-isophoronediamine). The metathesis homopolymerization of these bis(nadimides) in the presence of the second-generation Grubbs catalyst afforded glassy cross-linked polymers in more than 90% yields. The metathesis copolymerization of the bis(nadimides) and a monofunctional norbornene derivative containing the β-pinene fragment also resulted in insoluble cross-linked polymers in nearly quantitative yields. The structures and purity of the synthesized polymers were confirmed via IR spectroscopy and CP/MAS NMR spectroscopy. Conditions for the fabrication of mechanically strong solution-cast thin films based on copolymers synthesized from the comonomers mentioned above were determined by varying the content of the cross-linking agent. It was shown that the films made in this way are stable in a range of organic solvents and could be useful as semipermeable or membrane materials for use in liquid organic media. The permeability of the polymer films in question to 1-phenylethanol and mandelic acid was studied. The results obtained are discussed along with the data from the DSC, TGA, and powder X-ray diffraction studies of the properties of the synthesized metathesis homo- and copolymers.

Deep blue high-efficiency solution-processed triplet-triplet annihilation organic light-emitting diodes using bis(8-carbazol-N-yl)fluorene- and benzonitrile-modified anthracene/chrysene fluorescent emitters

Triplet-triplet annihilation (TTA) emitters can effectively utilize non-radiative triplet excitons through the interaction of low triplet energy excitons to produce high energy singlet excitons, but they are mostly restricted by their multilayered device structure fabricated using layer-by-layer thermal vacuum evaporation. It is a great challenge to develop, for the first time, efficient solution-processed non-doped TTA organic light-emitting diodes (OLEDs). In this study, two solution-processable blue emissive TTA molecules (FAnCN and FCsCN) bearing (anthracen-9-yl)benzonitrile (AnCN) and (chrysen-6-yl)benzonitrile (CsCN) as TTA emissive cores modified with 9,9′-bis(8-(carbazole-N-yl)octyl)fluorene (F) are designed and synthesized, respectively. The experimental and theoretical studies reveal that both molecules exhibit deep blue emissions, amorphous morphology with good thermal stability, high-quality solution-cast thin films, decent hole mobility, high-lying HOMO levels (∼-5.45 eV), and suitable lowest singlet (S1)/triplet (T1) excited states (2T1 > S1) for TTA process. FAnCN and FCsCN are successfully employed as solution-processed non-doped emissive layers (EML) in simple structured TTA OLEDs. These devices show intense blue emissions, low turn-on voltages (∼3.6 V), excellent electroluminescent (EL) performances (EQEmax = 5.47–6.84 % and LEmax = 5.66–5.83 cd/A), and TTA characteristics. Especially, FCsCN-based TTA OLED emits deep blue EL emission peaked at 435 nm with a high EQEmax of 6.84 %. This work not only presents a new strategic design for the preparation of solution-processable TTA emitter, but also further ratifies that the TTA mechanism can also be applicable in solution-processed OLEDs.

Enhanced UV protection in silk fibroin based electrospun fabrics realized via orientation induced high efficiency of azobenzene isomerization

Due to the poor UV protection capability, natural silk fabrics not only suffer from easy damage by sunshine but also induce possible sunburn in the human body. Efficient azobenzene isomerization and enhanced UV shielding are realized by replacing the natural silk with natural protein silk fibroin (SF) and electrospinning together with light-responsive copolymer P(MEO2-co-OEG300-co-AHMA). Compared to a solution cast film, the absorption peak intensity at 355 nm is 60 % higher in UV–Vis spectra of the electropsun SF/P(MEO2-co-OEG300-co-AHMA) fabrics. This improvement is related to the highly oriented chains, inducing more space and higher efficiency for azobenzene isomerization. Only exposure to visible light for 20 min, the absorption peak corresponding to the trans- state at 355 nm recovers to 92.5 % in the electrospun fabrics, which is at least 100 % faster than that in the solution cast film (50 min). It is related to the zip effect of the isomerization in the oriented chain structure. Thus, not only the absorption of UV radiation, but also the isomerization rate is enhanced. Based on these unique absorption and recovery capabilities, the SF based electrospun fabrics can be used to replace the natural silk fabrics for UV shielding in summer, especially for cyclic use.

Enhanced magnetoelectric and energy storage performance of strain-modified PVDF-Ba0.7Ca0.3TiO3-Co0.6Zn0.4Fe2O4 nanocomposites

The experimental development of thin films that exhibit higher room-temperature low-field magnetoelectric (ME) sensing without compromising reliable electrical energy storage capabilities is rare. Here, an improved ferroelectric polarization, ME coupling and energy storage performance of polymer-based nanocomposites, which find applications in portable high-power dielectric capacitors, are studied. Multiferroic nanofiller-based three-phase flexible nanocomposites, polyvinylidene fluoride (PVDF)-(Ba0.7Ca0.3)TiO3-(Co0.6Zn0.4)Fe2O4, were fabricated using compression molding to enhance polarization which is pivotal for applications. PVDF with a high β-phase content (92.4 %), switchable ferroelectric behavior and higher breakdown strength (510 kV/mm) was obtained under optimized process conditions (500 MPa at 165 °C). The fabrication assisted alteration of intermolecular chain distance results in a tensile strain (1.42 %) of β-crystallites corresponding to an internal stress of ~21 MPa. The progressive increase of nanofiller content has led to enhanced polarization (11 μC/cm2), soft ferromagnetic properties, and enhanced ME coupling of 59 mV/cm-Oe due to switchable magnetostriction (λ11 = −18 ppm and dλ11/d = −22 × 10−9 Oe−1) at lower saturation field of 1.2 kOe. The ME sensitivity was found to be more than two-folds enhanced compared to solution-cast films making them prospective self-biased flexible devices for wearable electronics. Simultaneously, enhanced change of magnetization (19.6 %) under electric field was obtained. Detailed energy storage characteristics confirm that the nanofiller inclusion up to 7.12 vol% effectively improved the recoverable energy storage density (21.2 J/cm3) with an efficiency of 67 %. The experimental and simulation results corroborate a significantly improved breakdown strength of 617 kV/mm with reliable performance. Thus, careful processing provides viable polymer dielectrics with beneficial storage characteristics.

Porous Nano-Fiber Structure of Modified Electrospun Chitosan GBR Membranes Improve Osteoblast Calcium Phosphate Deposition in Osteoblast-Fibroblast Co-Cultures.

Desirable characteristics of electrospun chitosan membranes (ESCM) for guided bone regeneration are their nanofiber structure that mimics the extracellular fiber matrix and porosity for the exchange of signals between bone and soft tissue compartments. However, ESCM are susceptible to swelling and loss of nanofiber and porous structure in physiological environments. A novel post-electrospinning method using di-tert-butyl dicarbonate (tBOC) prevents swelling and loss of nanofibrous structure better than sodium carbonate treatments. This study aimed to evaluate the hypothesis that retention of nanofiber morphology and high porosity of tBOC-modified ESCM (tBOC-ESCM) would support more bone mineralization in osteoblast-fibroblast co-cultures compared to Na2CO3 treated membranes (Na2CO3-ESCM) and solution-cast chitosan solid films (CM-film). The results showed that only the tBOC-ESCM retained the nanofibrous structure and had approximately 14 times more pore volume than Na2CO3-ESCM and thousands of times more pore volume than CM-films, respectively. In co-cultures, the tBOC-ESCM resulted in a significantly greater calcium-phosphate deposition by osteoblasts than either the Na2CO3-ESCM or CM-film (p < 0.05). This work supports the study hypothesis that tBOC-ESCM with nanofiber structure and high porosity promotes the exchange of signals between osteoblasts and fibroblasts, leading to improved mineralization in vitro and thus potentially improved bone healing and regeneration in guided bone regeneration applications.

Mechanically robust multifunctional starch films reinforced by surface-tailored nanofibrillated cellulose

The objective of this study was to develop a transparent, mechanically robust, and fully biodegradable film made of sweet potato starch (SPS) reinforced with nanofibrillated cellulose (NFC) to serve as a potential alternative for packaging. Various surface modifications were applied to NFC using urea/NaOH (UA), oxalic acid (OA), citric acid (CA), and (3-mercaptopropyl) trimethoxysilane (MT). SPS/NFC blend was innovatively treated by ball-milling, incorporating different concentrations (2–10 wt%) of surface-modified NFC and calcium gluconate as a modifier. Interestingly, the solution-cast blend films possessed improved tensile strength, tensile modulus, crystallinity, barrier property and hydrophobicity after NFC additions. More importantly, ball-milling promoted the physical combination of starch and NFC and generated metal-organic supramolecular interaction between –OH and Ca2+. In particular, the SPS-OA/NFC6 composite film exhibited remarkable improvements in tensile strength and tensile modulus, increasing from 1.46 MPa to 13.7 MPa and 6.04 MPato 531.33 MPa, respectively, compared to the neat SPS film. The contact angle of the SPS/CA-NFC6 film was approximately 79% higher than that of the pure SPS film. Generally, the optimal NFC addition was 6 wt%. This study provides guidance for the production of a new type of starch-based material with high mechanical strength and transparency.

Polymer Photocatalysts with Side Chain Induced Planarity for Increased Activity for Sacrificial Hydrogen Production from Water

AbstractConjugated polymers are promising materials for photocatalytic hydrogen evolution. However, most reported materials are not solution‐processible, limiting their potential for large‐scale application, for example as solution cast films. Flexible side‐chains are commonly introduced to provide solubility, but these often impart unfavorable properties, such as hydrophobicity, which lowers photocatalytic activity. Here, computational predictions are employed to aid in the design of chloroform soluble polymer photocatalysts that show increased planarity through favorable intramolecular interactions. Using this approach, three conjugated polymer photocatalysts with identical poly(benzene‐dibenzo[b,d]thiophene sulfone) backbones but different solubilizing side‐chains on the benzene‐ring are explored, i.e., tri(ethylene glycol), n‐decyloxy, and n‐dodecyl. These side‐chain variations significantly alterr the properties of the polymers, specifically energy levels, optical gap, and wettability. The hydrophobic n‐decyloxy functionalized polymer has a sacrificial hydrogen evolution rate of 17.0 µmol h−1 in suspension, while the hydrophilic tri(ethylene glycol) functionalized polymer is almost three times more active (45.4 µmol h−1). Conversely, no hydrogen evolution is observed for the purely alkyl side‐chain (n‐dodecyl) containing polymer due to the side‐chain induced torsion of the backbone. A thin‐film of the most active polymer exhibits a promising area‐normalized sacrificial hydrogen evolution rate of 7.4 ± 0.3 mmol h−1 m−2 under visible light irradiation.

Influence of H-bonding on the crystalline structures and ferroelectric and piezoelectric properties of novel nanogenerators of the lithium salt of 6-amino hexanoic acid incorporated poly(vinylidene fluoride) composites.

The lithium salt of 6-amino hexanoic acid (Li-AHA) was melt-mixed with poly(vinylidene fluoride) (PVDF), wherein the Li-AHA concentration was varied between 1-15 wt% with the aim of establishing hydrogen bonding between the NH2 functionality of Li-AHA and the -CF2 moieties of PVDF. This was followed by compression-moulding as well as solution-casting to make PVDF/Li-AHA composite thin films. FTIR analysis established interactions between the -CF2 groups in PVDF with amine functional moieties of Li-AHA. Moreover, FTIR analysis estimated that the solution-cast PVDF/Li-AHA composite of 15 wt% Li-AHA exhibited the highest polar phase fraction of ∼60%. Furthermore, ferroelectric analysis showed that the solution-cast PVDF/Li-AHA composite of 15 wt% Li-AHA exhibited the highest remnant polarization of 0.07 μC cm-2 (at 50 Hz, 1000 V) from the polarization versus electric field loop. Finally, energy harvester devices were fabricated using compression-moulded and solution-cast PVDF/Li-AHA composite films, in which a maximum output voltage of ∼110 V was obtained in the solution-cast PVDF/Li-AHA composite of 15 wt% Li-AHA. The devices also displayed a maximum power density of 75 μW cm-2 and 85 μW cm-2 for those fabricated via compression-moulding and solution-casting, respectively. Three different capacitors were efficiently charged by the tapping of the devices made from solution-cast and compression-moulded composite films of 15 wt% Li-AHA. An interrelationship between processing, structure and properties was successfully established in the PVDF/Li-AHA composites with greatly enhanced piezoelectric properties.

Solution Processable Polyaniline with High Electrochemical Charge Capacity

Polyaniline (PANI) is a charged polymer well-known for its high charge storage capacity and moderate electrical conductivity. PANI is often prepared by chemical or electro-polymerization, however, these polymerization methods limit options for substrate material, electrode/device geometry, and polymer morphology. To address these limitations, it is attractive to form PANI films by solution-casting. In this study, we examine the electrochemical properties of solution-cast PANI films formed from a commercially available PANI suspension containing excess dinonylnaphthalenesulfonic acid (DNNSA). Films prepared by solution casting of PANI-DNNSA have been previously characterized in terms of conductivity, morphology, and optical properties, however the electrochemical behavior of these films has been largely unexplored. Here, we present an electrochemical analysis of these solution-cast PANI films using quartz crystal microbalance, electrochemical impedance spectroscopy, and cyclic voltammetry. As cast, we find that the polymer exhibits limited electrochemical activity, but that postprocessing the material with electrolyte and crosslinking solutions increases the charge capacity up to 95 mAh/g – 86% of the charge capacity typically reported for electrodeposited PANI films. Ion-exchange processes, electrochemical capacitance, and energy storage capabilities of the chemically treated solution-cast films are assessed and compared to those of electro-deposited and chemically oxidized PANI. We demonstrate redox-active PANI films on both (a) conductive and insulating, and (b) planar and porous substrates. Finally, symmetric faradaic supercapacitor devices were constructed using spin-coated PANI electrodes in aqueous electrolyte, and the stability of these devices was examined by repeat galvanostatic charging/discharging at low current, achieving up to 88% capacity retention after 500 charge-discharge cycles.

Multiple shearing-induced high alignment in polyethylene/graphene films for enhancing thermal conductivity and solar-thermal conversion performance

The simultaneous achievement of ordered alignment for fillers and polymer matrix is highly desired in polymer-based thermally conductive composites, but it is still extremely challenging. Herein, we put forward a layer-by-layer scraping (LbLS) method to simultaneously arrange ultra-high molecular weight polyethylene (UHPE) chains and graphene nanoplates (GNP) into a highly oriented structure. When UHPE/GNP gel suffering the strong shearing effect during LbLS process, the inner UHPE chains and GNP were dragged and orderly arranged along shearing direction, and these oriented structures were retained after rapidly drying by distillation. After layer-by-layer stacking, nacre-like UHPE/GNP films with tightly layered structure were obtained. By adjusting the scraping gap from 200 to 50 μm, the oriented structure can be effectively reinforced with the Herman orientation factors f increasing from 0.83 to 0.88 for GNP and 0.75 to 0.82 for UHPE chains. The highly ordered structure can form a tight and oriented thermal conduction network with low interfacial thermal resistance in plane. The LbLS composite film thus significantly enhanced the in-plane thermal conductivity up to 28.88 W/mK, compared with traditional solution casting film (9.63 W/mK). Moreover, the highly oriented structure can significantly increase the solar-thermal conversion performance (58.1 °C@100 mW/cm2) by improving its light absorption ability comparing to that of solution casting film. Besides, the mechanical strength and toughness that depend on the filler and chain alignment were effectively increased by the oriented structure.

Regulating Organic Dopant Dispersion in Polymer Matrices for Concentration‐Controlled Color‐Tunable Organic RTP Emissions

AbstractMulti‐aryl conjugated organic molecules have intrinsically poor compatibility with most polymers, although they can be dispersed into polymer matrices by solution casting film. This work proposes that this property can be used to obtain diverse dispersion states and realize unique room temperature phosphorescence (RTP). Herein, cyano‐ and amide‐containing N‐phenylcarbazoles (2Q5X, 2J5X) are doped into different polar and rigid PVA and PMMA. 2J5X/PVA emits blue and green RTP after 254 and 365 nm light excitation, respectively, whereas 2Q5X/PVA emits green RTP bearing excitation wavelength‐dependent blue‐emitting shoulder. When 2Q5X is doped into PMMA, this blue RTP becomes dominant due to the increase in molecular dispersion ratio. Combined with the investigations on RTP properties of low doping concentration polymers and crystalline and amorphous states, the blue RTP and green RTP are attributed to the emissions of the isolated molecule and the clustering molecules, respectively. This work reveals that regulating the dispersion of organic dopants in polymers can provide unique and diverse RTP properties.

Structure-property correlation of polyvinyl alcohol films fabricated by different processing methods

Polyvinyl alcohol (PVA) films prepared by solution casting method or thermal processing techniques have been widely used in industrial applications. However, the relationship between processing methods and structural properties is still unclear. In this study, three film-forming techniques, namely solution casting, blown film extrusion and extrusion casting, were adopted to prepare PVA films and the influence of processing methods on the structural and physical properties of the films was studied. The results showed that blown film (BF) prepared under biaxial elongational flow had higher crystallinity, larger crystallite size and greater in-plane orientation compared to solution cast film (SCF) and extruded film (ETF). SCF showed the smallest crystallite size, slowest melting temperature, fewer defects, evident skin-core structure and in-plane orientation ascribing to its slow film forming process, stratified solidification and low initial macromolecular concentration. ETF displayed the lowest degree of crystallinity and orientation owing to the fast cooling outside the slit die and the absence of strong flow field. Hence, BF and SCF were endowed with high tensile strength (152.8 and 134.5 MPa), good puncture resistance (245.0 and 245.7 N/mm) and excellent oxygen barrier property (PO2 = 3.07 × 10−19 and 2.33 × 10−18 cm3 cm/(cm2·s·Pa)) while ETF exhibited inferior mechanical properties and oxygen barrier performance. These findings are of significance for building relationships between processing techniques, structural characteristics and practical properties of PVA films and help match appropriate film forming technology to the production of films for different application scenarios.

6FDA-DABA polyimide, polyphenylene, and polyimide-polyphenylene multiblock synthesis, characterization, and membrane gas separation performance and modeled transport

A 6FDA-DABA (6FD) polyimide, polyphenylene (PP), and multiblock copolymer (6FD-PP) materials were synthesized using sequential polycondensation and Diels-Alder reactions. PP and 6FD solubility parameters were 19.4 (MPa)1/2 and 22.4 (MPa)1/2, as predicted using Group Contribution Theory. Due to their solubility parameter differences, PP and 6FD solutions in tetrahydrofuran became immiscible when mixed at all concentrations. However, 6FD-PP multiblock copolymer solutions were clear, and their solution-cast films were robust and creasable. Homopolymer and block copolymers estimated fractional free volume (FFV) ranged from 0.174 (6FD) to 0.196 (PP). Their densities and FFV largely obeyed the rule of mixtures, suggesting a "blend-like" morphology. The glass transition temperature (Tg) of 6FD and PP were 285 °C and 400 °C, which became two distinct Tgs at 340 °C and 420 °C for 6FD-PP-[14k:13k]. Larger PP block lengths appeared to suppress the first-order polyimide transition entirely. SAXS and AFM morphological analysis revealed two distinct domains with an average separation distance ranging from 9.0 to 47.7 nm, dependent on PP block length. Membrane gas separation performance was compared to Robeson's upper bound. 6FD-PP multiblock copolymer gas transport properties were found to be highly dependent upon copolymer composition and FFV. Increasing PP content within a copolymer significantly improved gas permeability at the expense of He/CH4 and CO2/CH4 selectivity. Membrane CO2 permeability ranged from 4.36 Barrers using 6FD to 155 Barrers with PP. Their CO2/CH4 selectivity varied between 80.6 (6FD) to 12.7 (PP). 6FD-PP-[14k:13k] membrane's O2 permeability was between these polymers. The membrane had a 30% improvement in its ideal O2/N2 selectivity. The N2/CH4 selectivity ranged from 3 to 1.70, suggesting that 6FD-PP multiblock systems could be efficiently tailored from N2 to CH4 selectivity. Five gas permeability models (rule-of-mixture, Maxwell, EBM, laminate, and blend) were used to study 6FD-PP block copolymer transport behavior. Among them, a blend model had the most reasonable gas permeability prediction. 6FD-PP multiblock membranes improved several ideal gas pairs leading to more permeable and selective materials. The synthetic approach using block copolymerization creates an opportunity for gas separation improvement and tuneability of specific gas pairs.

Synthesis of Multiblock Copolymer Composed of Biodegradable Poly(butylene succinate) and Poly(2-pyrrolidone): Impact of Each Block Length on the Mechanical Properties.

A series of multiblock copolymers comprising a systematic combination of biomass-originated and biodegradable poly(butylene succinate) (PBS) and poly(2-pyrrolidone) (PA4) units is synthesized with various mean degrees of polymerization (mDP) of each unit. Despite the inherent immiscibility of PBS and PA4, multiblock structure allows to mix the two components in the solution-cast films from solution. The mechanical properties of the cast films are highly dependent on the mDP of each unit, as demonstrated by tensile tests. The film of the copolymer with the lowest mDP of each unit (PBS: 17, PA4: 10) is transparent and exhibits extremely high elongation at break (> 400%) and high tensile stress (39.5MPa) with strain hardening. The films with 50% or higher crystallinity are brittle and opaque, while a decrease in crystallinity can result in higher elongation, as revealed by wide-angle X-ray diffraction measurements.

Short-Loop Chemical Recycling via Telechelic Polymers for Biobased Polyesters with Spiroacetal Units

Spirocyclic acetal structures have recently received growing attention in polymer science due to their dual potential to raise the glass transition temperature (Tg) and enable chemical recycling of biobased polymers. In the present work, a vanillin-based diol with a spirocyclic acetal structure was incorporated in a series of rigid amorphous polyesters based on neopentyl glycol and dimethyl terephthalate (DMT). Up to 50 mol % of spirocyclic diol (with respect to DMT) could be incorporated in the copolyesters, but a reasonably high molecular weight was only achieved when ≤30 mol % of the spirocyclic diol was used. The presence of the spiroacetal units in the polyesters not only enhanced the Tg (up to 103 °C) and thermal stability (T5 ≥ 300 °C) but also the oxygen barrier of solution-cast films. We found that the acetal units in the copolyesters could be selectively hydrolyzed under acidic conditions while virtually retaining all of the ester bonds in the polymer backbone. After acidic hydrolysis, telechelic polymers exclusively terminated by two aldehyde end groups were obtained. In this work, we have demonstrated that these telechelic polyesters can be conveniently converted back into poly(acetal-ester)s via cycloacetalization reactions with pentaerythritol.

Preparation of high electromagnetic interference shielding and humidity responsivity composite film through modified Ti3C2Tx MXene cross-linking with sodium alginate

This paper established a new kind of L-citrulline-modified MXene cross-linked sodium alginate composite film through solution blending and casting film methods. The L-citrulline-modified MXene cross-linked sodium alginate composite film exhibited high electromagnetic interference shielding efficiency of 70 dB and high tensile strength of 7.9 MPa, which were much higher than the sodium alginate film without L-citrulline-modified MXene. In addition, the L-citrulline-modified MXene cross-linked sodium alginate film appeared humidity responsibility in a water vapor environment, the weight, thickness, and current appeared to increase trend and the resistance appeared to decrease trend after it absorbed water, and these parameters recovered to their original values after drying.

Enhancing the thermal conductivity of amorphous polyimide by molecular-scale manipulation

Due to their remarkable mechanical, chemical, and electrical properties, polymers are widely utilized in industry. However, the low thermal conductivity of polymers limits more extended applications of them that require high degrees of heat dissipation. Here, we demonstrate that the combination of increased chain orientation and powerful intermolecular interaction can boost the thermal conductivity of polyimide (PI). The thermal conductivity values of electrospun individual PI nanofibers (INF-PI) and hot-pressed nanofibrous PI films (HP-PI) formed with these nanofibers were as high as 0.44 and 0.98 W m−1 K−1, respectively, at room temperature. The former and the latter were measured by the suspended microdevice and hot-disk methods, respectively. These values are considerably higher than the solution-casting PI film (SC-PI) value of 0.1 W m−1 K−1. Furthermore, molecular-scale structural characterizations revealed that the electrospinning process improved chain orientation and that high pressure and thermal treatment during the hot-pressing process facilitated the formation of π–π interactions, resulting in an exceptionally high thermal conductivity in HP-PI.

3D-Printed Pectin/Carboxymethyl Cellulose/ZnO Bio-Inks: Comparative Analysis with the Solution Casting Method.

Bio-inks consisting of pectin (Pec), carboxymethyl cellulose (CMC), and ZnO nanoparticles (ZnO) were used to prepare films by solution casting and 3D-printing methods. Field emission scanning electron microscopy (FE-SEM) was conducted to observe that the surface of samples made by 3D bioprinter was denser and more compact than the solution cast samples. In addition, Pec/CMC/ZnO made by 3D-bioprinter (Pec/CMC/ZnO-3D) revealed enhanced water vapor barrier, hydrophobicity, and mechanical properties. Pec/CMC/ZnO-3D also showed strong antimicrobial activity within 12 h against S. aureus and E. coli O157: H7 bacterial strains compared to the solution cast films. Further, the nanocomposite bio-inks used for 3D printing did not show cytotoxicity towards normal human dermal fibroblast (NDFB) cells but enhanced the fibroblast proliferation with increasing exposure concentration of the sample. The study provided two important inferences. Firstly, the 3D bioprinting method can be an alternative, better, and more practical method for fabricating biopolymer film instead of solution casting, which is the main finding of this work defining its novelty. Secondly, the Pec/CMC/ZnO can potentially be used as 3D bio-inks to fabricate functional films or scaffolds and biomedical applications.

The relationship between exponent t in McLachlan equation and electronic percolation thresholds of solution cast films

The relationship between exponent t in McLachlan equation and electronic percolation thresholds of solution cast films

In-situ grafting N-arylcarbazoles enables more ultra-long room temperature phosphorescence polymers

N-Arylcarbazole derivatives have been proven to be applicable dopants for organic room temperature phosphorescence (RTP) polymers. Here we present for the first time that their structure modification enables highly-efficient and more ultra-long RTP. Three N-phenylcarbazole derivatives (CZPA, CZBM, and CZBA) containing boronic acid, formamide, and carboxyl units are doped into polyvinyl alcohol (PVA) by thermoplasticizing solution-cast films. PVA/CZBA and PVA/CZBM sheets show highly-level balanced RTP efficiencies (13.7–17.8 %) and lifetimes (1.79–1.97 s), and PVA/CZPA sheets exhibit ultralong RTP lifetimes of 2.36–3.21 s and commendable RTP efficiencies of 3.6–6.1 % under 365 nm light excitation. To our knowledge, the current doped polymer films with similar RTP lifetimes are almost excited by deep UV light, and N-arylcarbazoles have never been developed as so excellent dopants for ultra-long RTP polymers. The greatly improved RTP properties are attributed to the dual effect of extra n-π* transition and chemical grafting of boronic acid onto PVA chains, which not only enhances triplet population but also inhibits non-radiative relaxation. This work opens up an effective molecular and processing strategy for enhancing RTP properties of organic doped polymers.