Bulky Side Groups Research Articles

New Polymeric Acceptors Based on Benzo[1,2-b:4,5-b'] Difuran Moiety for Efficient All-Polymer Solar Cells.

In order to realize high-performance bulk-heterojunction (BHJ) all-polymer solar cells, achieving appropriate aggregation and moderate miscibility of the polymer blends is one critical factor. Herein, this study designs and synthesizes two new polymer acceptors (PAs), namely PYF and PYF-Cl, containing benzo[1,2-b:4,5-b'] difuran (BDF) moiety with/without chlorine atoms on the thiophene side groups. Thanks to the preferred planar structure and high electronegativity of the BDF units, the resultant PAs generate strong intermolecular interactions and π-π stacking in both the neat and blend films. At the same time, the BDF moieties flanked with bulky 2D side groups increase intermolecular space and restrain the excessive entanglement of polymer chains for developed heterojunction miscibility attributes. Consequently, appropriate polymer crystallinity and moderate miscibility between PAs and polymer donor (PD) contribute to harmonious blending morphologies. Eventually, the PM6:PYF-based solar cells achieve an optimal efficiency of 11.82%. More encouragingly, the PYF serves as an efficient guest acceptor and realizes an improved efficiency of 17.05% in the PM6:PYIT:PYF ternary systems, which is much higher than that of the host system (15.87%). This study highlights the importance of BDF moiety in designing new PAs for high-performance all-polymer solar cells.

From Molecular Design to Practical Applications: Strategies for Enhancing the Optical and Thermal Performance of Polyimide Films.

Polyimide (PI) films are well recognized for their outstanding chemical resistance, radiation resistance, thermal properties, and mechanical strength, rendering them highly valuable in advanced fields such as aerospace, sophisticated electronic components, and semiconductors. However, improving their optical transparency while maintaining excellent thermal properties remains a significant challenge. This review systematically checks over recent advancements in enhancing the optical and thermal performance of PI films, focusing on various strategies through molecular design. These strategies include optimizing the main chain, side chain, non-coplanar structures, and endcap groups. Rigid and flexible structural characteristics in the proper combination can contribute to the balance thermal stability and optical transparency. Introducing fluorinated substituents and bulky side groups significantly reduces the formation of charge transfer complexes, enhancing both transparency and thermal properties. Non-coplanar structures, such as spiro and cardo configurations, further improve the optical properties while maintaining thermal stability. Future research trends include nanoparticle doping, intrinsic microporous PI polymers, photosensitive polyimides, machine learning-assisted molecular design, and metal coating techniques, which are expected to further enhance the comprehensive optical and thermal performance of PI films and expand their applications in flexible displays, solar cells, and high-performance electronic devices. Overall, systematic molecular design and optimization have significantly improved the optical and thermal performance of PI films, showing broad application prospects. This review aims to provide researchers with valuable references, stimulate more innovative research and applications, and promote the deep integration of PI films into modern technology and industry.

Influence of particle parameters on deposition onto healthy and damaged human hair.

This research investigates how particle parameters, such as zeta potential, size, functional group, material composition, and hydrophobicity affect their affinity and deposition of particles onto hair. Streaming potential was used as the technique for analysis. The streaming potential data obtained was then converted to surface coverage data. Scanning electron microscopy (SEM) was also done to visualize particle localization on the hair surface. This study found stronger particle affinity on healthy than on damaged (oxidatively bleached) hair, due to diminished interaction sites from the removal of the hair shaft's external lipid layer. SEM imaging supported these findings and offered insights into particle localization. Hydrophilic silica particles accumulated along the exposed hydrophilic cuticle edges of healthy hair, due to hydrogen bonding with the exposed endocuticle. This localization is hypothesized to be due to the limited hydrophilic binding sites on the hydrophobic healthy hair cuticle surface. In damaged hair, an abundance of hydrophilic sites across the cuticle surface results in more dispersed binding. Hydrogen bonding and electrostatic attraction were shown to be the predominant forces influencing deposition, with hydrophobic interactions playing a less influential role. The affinity studies also proved that electrostatic attractions work over a longer range and are more effective at lower particle conditions compared with hydrogen bonding which only start to play a bigger role at higher particle concentrations. Steric hindrance of bulky side groups acted as a significant repulsive force. Results also revealed that larger particles deposit poorly on both healthy and damaged hair compared with smaller ones. Compared with neutrally charged silica nanoparticles (SN-2), positively charged PMMA particles (PN+16) have a stronger affinity to healthy hair, with highly charged particles (PN+49) depositing most rapidly. This study provides a fundamental understanding of how particle-surface parameters influence their affinity to hair and how damaging hair affects deposition.

Designing A-D-A Type Fused-Ring Electron Acceptors with a Bulky 3D Substituent at the Central Donor Core to Minimize Non-Radiative Losses and Enhance Organic Solar Cell Efficiency.

Designing and synthesizing narrow band gap acceptors that exhibit high photoluminescence quantum yield (PLQY) and strong crystallinity is a highly effective, yet challenging, approach to reducing non-radiative energy losses (▵Enr) and boosting the performance of organic solar cells (OSCs). We have successfully designed and synthesized an A-D-A type fused-ring electron acceptor, named DM-F, which features a planar molecular backbone adorned with bulky three-dimensional camphane side groups at its central core. These bulky substituents effectively hinder the formation of H-aggregates of the acceptors, promoting the formation of more J-aggregates and notably elevating the PLQY of the acceptor in the film. As anticipated, DM-F showcases pronounced near-infrared absorption coupled with impressive crystallinity. Organic solar cells (OSCs) leveraging DM-F exhibit a high EQEEL value and remarkably low ▵Enr of 0.14 eV-currently the most minimal reported value for OSCs. Moreover, the power conversion efficiency (PCE) of binary and ternary OSCs utilizing DM-F has reached 16.16 % and 20.09 %, respectively, marking a new apex in reported efficiency within the OSCs field. In conclusion, our study reveals that designing narrow band gap acceptors with high PLQY is an effective way to reduce ▵Enr and improve the PCE of OSCs.

Effect of Hydrophobic Side-Group Chemistry on Conformation, Intermolecular Structure and Dynamics of Cationic Poly(Vinyl Amine) in Aqueous Solution

Atomistic molecular dynamics simulations of the single chains of cationic polyelectrolytes of atactic poly(vinyl amines) (PVAm) modified by hydrophobic side-groups, poly(N-ethyl-n-vinyl amine) (ethyl-PVAm) and poly(N-benzyl-n-vinyl amine) (benzyl-PVAm), in aqueous solution, were carried out over the entire range of degree-of-ionization, f. These polymers, to our knowledge, were studied here by molecular simulations for the first time. The interplay of electrostatic interactions, excluded volume, hydrophobic effect, hydrogen bonding and counter-ion interaction with hydrophobic-polyions, is analyzed. The conformational transition of the polyelectrolyte chain from a coiled to an extended state was gradual and was observed for 0.3 < f < 0.7. Ethyl-PVAm and benzyl-PVAm exhibited similar values of radius-of-gyration Rg and end-to-end distance R for f > 0.5, in agreement with available experimental data. The more hydrophobic benzyl-PVAm showed a more extended conformation with a preference for trans states in the backbone. The change in chain expansion with respect to f was more for benzyl-PVAm as compared to ethyl-PVAm. The relaxation time of polymer-water H-bonds increased with f and the hydrophobicity of the polymer chain, with faster decay for ethyl-PVAm. The water molecules solvating the hydrophobic PVAm’s showed dynamical restriction due to bulky hydrophobic side-groups resulting in long-lived H-bonds. The number of polymer-water H-bonds showed a transition at a certain charge, which influenced the complex interplay of steric effect, hydrophobic effect and solvation.

Azobenzene isomerization on a reactive copper surface by efficient decoupling with bulky side groups

Azobenzene derivatives, an important class of molecular switches that undergo isomerization between trans and cis states, have been studied on various coinage metal surfaces in the past. However, on reactive copper surfaces switching turned out to be difficult. Here, we show that the use of bulky 2,6-dimethylphenyl side groups enables switching on a Cu(111) surface as studied by scanning tunneling microscopy. By applying voltage pulses from the STM tip, irreversible trans → cis isomerization of individual molecules can be induced where exactly one molecule within each unit cell is isomerized. The absence of backward cis → trans switching illustrates the importance of the adsorption structure on the potential energy landscape of azobenzene. Isomerization, which is activated by inelastic scattering of single tunneling electrons, happens in a very localized fashion, thus allowing to ‘write’ patterns of individual cis isomers into the homogeneous molecular layer. Our study demonstrates how the bulky spacer groups direct adsorption and self-assembly into close-packed structures, which are similar to three-dimensional molecular crystals, on the surface. In addition, they modulate the electronic coupling to the underlying substrate to maintain successful switching behavior even on the most reactive coinage metal surfaces.

Atomic Force Microscopy and Molecular Dynamic Simulation of Adsorption of Polyacrylamide with Different Chemistries onto Calcium Carbonate.

This study investigates the interaction of polyacrylamide (PAM) of different functional groups (sulfonate vs. carboxylate) and charge density (30% hydrolysed vs. 10% hydrolysed) with calcium carbonate (CaCO3) via atomic force microscopy (AFM) and partly via molecular dynamic (MD) simulations. The PAM used were F3330 (30% hydrolysed), AN125 (25% sulfonated), and AN910 (% hydrolysed). A total of 100 ppm of PAMs was prepared in 0.1% NaCl, 3% NaCl, and 4.36% NaNO3 to be employed in AFM experiments, while oligomeric models (30 repeating units) of hydrolysed polyacrylamide (HPAM), sulfonated polyacrylamide (SPAM), and neutral PAM (NPAM) were studied on a model calcite surface on MD simulations. AFM analysis indicated that F3330 has a higher average adhesion and interaction energy with CaCO3 than AN125 due to the bulky sulfonate side group of AN125 interfering with SPAM adsorption. Steric repulsion of both PAMs was similar due to their comparable molecular weights and densities of the charged group. In contrast, AN910 showed lower average adhesion and interaction energy, along with slightly longer steric repulsion with calcite than F3330, suggesting AN910 adopts more loops and tails than the slightly flatter F3330 configuration. An increase in salt concentration from 0.1% to 3% NaCl saw a reduction in adhesion and interaction energy for F3330 and AN125 due to charge screening, while AN910 saw an increase, and these values increased further at 4.36% NaNO3. MD simulations revealed that the salt ions in the system formed salt bridges between PAM and calcite, indicating that the adhesion and interaction energy observed from AFM are likely to be the net balance between PAM charged group screening and salt bridging by the salt ions present. Salt ions with larger bare radii and smaller hydrated radii were shown to form stronger salt bridges.

Tunable Charge Transport and Spin Dynamics in Two-Dimensional Conjugated Metal-Organic Frameworks.

Two-dimensional conjugated metal-organic frameworks (2D c-MOFs) have attracted increasing interest in electronics due to their (semi)conducting properties. Charge-neutral 2D c-MOFs also possess persistent organic radicals that can be viewed as spin-concentrated arrays, affording new opportunities for spintronics. However, the strong π-interaction between neighboring layers of layer-stacked 2D c-MOFs annihilates active spin centers and significantly accelerates spin relaxation, severely limiting their potential as spin qubits. Herein, we report the precise tuning of the charge transport and spin dynamics in 2D c-MOFs via the control of interlayer stacking. The introduction of bulky side groups on the conjugated ligands enables a significant dislocation of the 2D c-MOFs layers from serrated stacking to staggered stacking, thereby spatially weakening the interlayer interactions. As a consequence, the electrical conductivity of 2D c-MOFs decreases by 6 orders of magnitude, while the spin density achieves more than a 30-fold increase and the spin-lattice relaxation time (T1) is increased up to ∼60 μs, hence being superior to the reference 2D c-MOFs with compact stackings whose spin relaxation is too fast to be detected. Spin dynamics results also reveal that spinless polaron pairs or bipolarons play critical roles in the charge transport of these 2D c-MOFs. Our strategy provides a bottom-up approach for enlarging spin dynamics in 2D c-MOFs, opening up pathways for developing MOF-based spintronics.

Consolidation of Calcium Carbonate Using Polyacrylamides with Different Chemistries

In this work, the consolidation of calcium carbonate (CaCO3) by polyacrylamide (PAM) of different molecular weights, charge densities, and functional groups was investigated via oscillatory rheology and unconfined compressive strength (UCS) analysis. Oscillatory rheology showed that the storage modulus G′ was approximately 10 times higher than the loss modulus G″, indicating a highly elastic CaCO3 sample upon consolidation via PAM. Both oscillatory rheology and UCS analysis exhibited similar trends, wherein the mechanical values (G′, G″, and UCS) first increased with increasing polymer dosage, until they reached a peak value (typically at 3 mgpol/gCaCO3), followed by a decrease in the mechanical values. This indicates that there is an optimum polymer dosage for the different PAM-CaCO3 colloidal systems, and that exceeding this value induces the re-stabilisation of the colloidal system, leading to a decreased degree of consolidation. Regarding the effect of the PAM molecular weight, the peak G′ and UCS values of CaCO3 consolidated by hydrolysed PAM (HPAM) of different molecular weights are very similar. This is likely due to the contour length of the HPAMs being either almost the same or longer than the average distance between two CaCO3 particles. The effect of the PAM charge density revealed that the peak G′ and UCS values decreased as the charge density of the PAM increased, while the optimum PAM dosage increased with decreasing PAM charge density. The higher likelihood of lower-charge PAM bridging between the particles contributes to higher elastic energy and mechanical strength. Finally, regarding the PAM functional group, CaCO3 consolidated by sulfonated polyacrylamide (SPAM) typically offers lower mechanical strength than that consolidated with HPAM. The bulky sulfonate side groups of SPAM interfere with the surface packing, reducing the number of polymers able to adsorb onto the surface and, eventually, reducing the degree of consolidation of CaCO3. The zeta potential of the PAM-CaCO3 samples became more negative with increasing PAM concentration due to the saturation of the particle surface. Good agreement between oscillatory rheology and UCS analysis could accelerate PAM screening for optimum CaCO3 consolidation.

N-heterocyclic carbenes – The design concept for densely packed and thermally ultra-stable aromatic self-assembled monolayers

Self-assembled monolayers (SAMs) of N-heterocyclic carbenes (NHCs) on metal substrates are currently one of the most promising systems in context of molecular-scale engineering of surfaces and interfaces, crucial for numerous applications. Interest in NHC SAMs is mainly driven by their assumingly higher thermal stability compared to thiolate SAMs most broadly used at the moment. Most of the NHC SAMs utilize imidazolium as an anchoring group for linking molecules to the metal substrate via carbene C atom. It is well established in the literature that standing up and stable NHC SAMs are built only when using bulky side groups attached to nitrogen heteroatoms in imidazolium moiety, which, however, leads to monolayers exhibiting much lower packing density compared to thiolate SAMs. Here, by combined X-ray photoelectron spectroscopy, near-edge X-ray absorption fine structure spectroscopy, and temperature-programmed secondary ion mass spectrometry analysis, we demonstrate that using NHCs with small methyl side groups in combination with simple, solution-based preparation leads to the formation of aromatic monolayers exhibiting at least doubled surface density, upright molecular orientation, and ultra-high thermal stability compared to the NHC SAMs reported before. These parameters are crucial for most applications, including, in particular, molecular and organic electronics, where aromatic SAMs serve either as a passive element for electrode engineering or as an active part of organic field effect transistors and novel molecular electronics devices.

Polymers and Green Chemistry

The purpose of this lab is to introduce students to some basics of the chemistry of polymers. Polymer chemistry is often an afterthought in the General Chemistry curriculum, but polymers are very much present in students’ lives. The lab introduces the relationship between molecular structure (e.g., branched vs. linear, bulky vs small side groups) and bulk properties (e.g., flexibility). This lab is also “pre-stoichiometry” in the sense that precursor ideas to stoichiometry are introduced without formal stoichiometric terminology. In one activity, the ratio of reacting alginate to calcium ions is varied to find the maximum yield of alginate gel. The lab introduces atom economy using addition and condensation polymers without formal stoichiometry. Students are likely to be at least a little familiar with recycling polymers before they even step into the lab. Building on this, using polymers as a lab topic provides an opportunity to bring Green Chemistry and Sustainability concepts into the lab course. Working with biologically-sourced, water-soluble starch or alginate polymers should be greener than working with polystyrene or nylon polymers which do not dissolve in pure water. The aforementioned atom economy example is also related to Green Chemistry principles. This document features contributions from Bozana Lojpur at Bradley University and Saskia van Bergen at the Washington State Department of Ecology.

Crosslinked polyimides with bulky side-group polyhedral silsesquioxanes: Towards lower dielectric constant and better mechanical property

The synthesis of a low dielectric constant polyimide (PI) with a polyhedral oligomeric silsesquioxane (POSS) cross-linked structure is presented. A non-planar conjugated diamine monomer (FSNH2) with two -CH=CH2 reactive groups was first synthesised in a two-step process, and then two polyimides were synthesized by PSS-Octavinyl (OVPOSS) substituted, FSNH2 and dianhydride. OVPOSS cross-linked polyimides have good thermal stability and low dielectric constant. 6FDA-FSNH2-OVPOSS(6FPI-3) can reach a minimum dielectric constant of 2.08 (108 Hz) and a dielectric loss of 0.008 (108 Hz). In addition, the cross-linked structure of the OVPOSS and polyimide chains prevents the agglomeration of OVPOSS to a certain extent and improves the tensile strength and elongation at break of the polyimides, which has great application potential in large-scale integrated circuits.

Polymers of Intrinisic Porosity with Bulky Side Groups on the Spirobisindane Moieties for Gas Separation

Polymers of Intrinisic Porosity with Bulky Side Groups on the Spirobisindane Moieties for Gas Separation

Correlation between conformational feature in solution and chiral separation ability of linear and nonlinear amylose tris(alkylcarbamate)s

Five immobilized-type chiral columns were prepared from linear, cyclic, and hyperbranched amylose tris(n-octadecylcarbamate) (ATODC) and amylose tris(n-butylcarbamate) (ATBC). A small amount of the linker site, 3-(triethoxysilyl)propylcarbamate, significantly reduced the chain dimensions of ATBC for which high chain stiffness is attained by intramolecular hydrogen bonding between butylcarbamate groups located on the neighboring glycosidic residue. This phenomenon was not found for ATODC, which is mainly stiffened by bulky side groups. While both columns have appreciable chiral recognition ability, number of separated racemates decreased with decreasing side group bulkiness. The bulkiness of the side groups thus plays a definite role in the chiral separation ability. Furthermore, chain linearity on the silica surface is an important factor for the chiral separation because no substantial chiral separation was found for the chiral columns consisting of cyclic ATODC and cyclic ATBC. The chiral column made of hyperbranched ATODC has an intermediate chiral separation ability between linear and cyclic ATODC, supporting this suggestion.

Cholesterol-substituted 3,4-ethylenedioxythiophene (EDOT-MA-cholesterol) and Poly(3,4-ethylenedioxythiophene) (PEDOT-MA-cholesterol)

Cholesterol is a rigid, crystalline, non-polar natural substance that exists in animal blood and cell membranes. Some of its derivatives are known to form ordered liquid crystalline mesophases under suitable conditions. In this work, we carefully examined the influence of cholesterol substitution on the characteristics of 3,4-ethylenedioxythiophene (EDOT-MA-cholesterol) and its corresponding polymer poly(3,4-ethylenedioxythiophene) (PEDOT-MA-cholesterol) synthesized by both chemical and electrochemical polymerization. We found evidence for an ordered lamellar (smectic-like) structure in the EDOT-MA-cholesterol monomer by differential scanning calorimetry (DSC), polarized optical microscopy (POM), and X-ray diffraction techniques. The ordered phase was observed to form on cooling from the isotropic melt at about 80 °C. Due to the insulating and bulky cholesterol side group on the EDOT monomer, we found that there was a maximum charge density for electrodeposition at ∼ 0.155 C.cm−2. A series of electrodepositions were performed from 0 to 0.155 C.cm−2 for probing the change of the charge transport with more charges used for the electrodeposition. We found that the impedance increased in the high-frequency range (above 104 Hz) and decreased in the low-frequency range (below 102 Hz). Three equivalent circuit models were proposed for fitting impedance data at different charge densities for a better understanding of the film growth process. The suppressed cyclic voltammogram (CV) of PEDOT-MA-cholesterol showed that the charge storage capability was essentially eliminated in the thickest films. The limited doping of the films was corroborated by their diminished electrochromic behavior, polaron-dominating absorption in UV-vis, overoxidized S 2p X-ray Photoelectron Spectroscopy (XPS) signal of electrodeposited films, and proton Nuclear Magnetic Resonance (1H NMR) of chemically polymerized samples. Dense film morphologies were confirmed by scanning electron microscopy (SEM). Grazing incident X-ray diffraction (GIWAXS) indicated the disrupted stacking of conjugated chains, which correlated with the decreased conductivity of the PEDOT-MA-cholesterol films. The measurement of the electrical conductivity gave a value of around 3.30 × 10−6 S.cm−1 which is about six orders of magnitude lower than has been seen in PEDOT (∼3 S.cm-1).

Heat-Resistant Polymers with Intense, Visible Photoluminescence Functionality and Fluorescence Probing Application

Heat-resistant polymers with an intense, visible photoluminescence (PL) functionality are presented. A polybenzoxazole (PBO) containing hexafluoroisopropylidene (HFIP) side groups exhibited an intense purple PL with a quantum yield, ΦPL, of 0.22 (22%), owing to the effectively disturbed concentration quenching (CQ) in the fluorophore units by the bulky HFIP side groups. The chain ends of a wholly cycloaliphatic polyimide (PI), derived from 1,2,3,4-cyclobutanetetracarboxylic dianhydride (CBDA) and 4,4′-methylenebis(cyclohexylamine) (MBCHA), were modified with conjugated monoamines. The PI derived from 2,3,6,7-naphthalenetetracarboxylic dianhydride (2,3,6,7-NTDA) and MBCHA exhibited a very high glass transition temperature (Tg = 376 °C) and purple fluorescence from the S1(π,π*) state. However, its ΦPL value was lower than expected. A pronounced effect of fluorophore dilution using CBDA on the PL enhancement was observed. This is closely related to the planar structure of the 2,3,6,7-NTDA-based diimide units. By contrast, the counterpart using an 2,3,6,7-NTDA isomer, 1,4,5,8-NTDA, was virtually non-fluorescent, despite its sufficient dilution using CBDA. The PI film obtained using 3,3″,4,4″-p-terphenyltetracarboxylic dianhydride (TPDA) with a non-coplanar structure and MBCHA exhibited an intense blue fluorescence spectrum (ΦPL = 0.26) peaking at 434 nm. The dilution approach using CBDA enhanced its fluorescence up to a high ΦPL value of 0.41. Even when TPDA was combined with an aromatic diamine, 2,2′-bis(trifluoromethyl)benzidine (TFMB), the intense blue fluorescence was observed without charge-transfer fluorescence. A semi-cycloaliphatic PI derived from TFMB and a novel cycloaliphatic tetracarboxylic dianhydride, which was obtained from a hydrogenated trimellitic anhydride derivative and 4,4′-biphenol, was used as another host polymer for 9,10-bis(4-aminophenyl)anthracene (BAPA). The BAPA-incorporating PI film resulted in a significant PL enhancement with a considerably high ΦPL of 0.48. This PI film also had a relatively high Tg (265 °C). A reactive dye, N,N′-bis[4-(4-amino-3-methylbenzyl)-2-methylphenyl]-3,4,9,10-perylenetetracarboxydiimide, was harnessed as a fluorescence probe to explore transamidation between polyimide precursors in solution.

Design of polyarylates containing tert‐butyl cyclohexyl bulky side group with high transparency and low dielectric properties

AbstractA new kind of novel low dielectric constant (Dk) and high transparency polyarylate had been synthesized through interfacial polycondensation with 1,1′‐ bis (4‐hydroxybenzene)‐4‐tert‐butylcyclohexane (Bt‐BPZ) containing tert‐butyl cyclohexyl bulky side group. As we expect, that the introduction of tert‐butyl cyclohexyl with large free volume is proved to be an efficient strategy for obtaining low dielectric constant and high transparency polyarylate. The optimal dielectric property is obtained with 90% Bt‐PZA in polyarylate (Bt‐PZA91), which show aDkas low as 2.14 at 1 MHz. Meanwhile, Bt‐PZA91 also demonstrates good transmittance of 81.08%–88.34% at 450 nm and 78.67–88.26 at 400 nm. The cut‐off wavelength of Bt‐PZA91 is 304 nm, which is 16 nm shorter than commercial product U‐100 (λc: 320 nm). In addition, the resultant polyarylates showed good comprehensive performance such asTgof 202.2–220.5°C,Td 5%(the initial thermal degradation temperature) of 455.4–468.4°C, tensile strength of 64.7–86.8 MPa and low water absoption (0.41% of Bt‐PZA91). Also it was found to can be thermal process, that its convenient thermoplastic processability makes it a great candidate for light‐electronic industry, 5G communication, and we believe that Bt‐PZA will have a broad application prospect.

Effect of bulky side groups on photophysical properties and electroluminescent performance of oligo(styryl)benzenes

The rational design of electroluminescent compounds has been recognized as a promising strategy to maximize the efficiency of electronic devices. In this work, we analyze the impact of the substitution of n-alkyl and n-alkoxy side chains by bulkier side groups (tert-butyl and tert-butoxy) on the photophysics of the two model fluorophores 1,3,5-tris(styryl)benzene and 1,2,4,5-tetra(styryl)benzene. We found that the bulky side groups have a significant contribution to the vibrational normal modes associated with the non-radiative deactivation. The aggregation-induced enhanced emission phenomenon observed in some cases was attributed to the blocking of the trans→cis photoisomerization and the restriction of intramolecular vibrations. In the solid state, the bulky side groups have demonstrated to play a determining role in the supramolecular structure and photophysical properties, particularly in the case of the tetra(styryl)benzenes. In light-emitting devices, we found that the incorporation of the bulky side groups in oligo(styryl)benzenes could reduce the electromer formation and improve the device performance. The tetra(styryl)benzenes, and particularly the tert-butyl derivative, showed better device performance, with lower turn-on voltage, higher current density and electroluminescent intensity.

Electroluminescent property of new chrysene derivatives having bulky side group of aromatic amine moiety

Two blue emitting materials, 4,4'-(chrysene-6,12-diyl)bis(N,N-diphenylaniline) (TPA-C-TPA) and 12-(4-(diphenylamino)phenyl)-N,N- Diphenylchrysen-6-amine (TPA-C-DPA) were prepared with the composition of chrysene core moiety and dipenylamine (DPA) and triphenylamine (TPA) moieties as the side group. Two compounds were used to emitting layer as the dopants (EMLs) in doped device. The doped device using TPA-C-TPA showed current efficiency of 2.49 cd/A and external quantum efficiency of 4.26% at a current density of 10 mA/cm2. The doped device using TPA-C-DPA exhibited CE of 2.28 cd/A and EQE of 3.52% at a current density of 10 mA/cm2. TPA-C-TPA and TPA-C-DPA show the Commission Internationale de L’Eclairage (CIE) coordinates of (0.15, 0.06) and (0.14, 0.06) corresponding to the electroluminescence peak at 439 and 444 nm.

Synthesis and properties of transparent poly(ester‐amide‐imide)s from tert‐butylhydroquinone bis(trimellitate anhydride) and p‐phthaloyl chloride

AbstractTwo series of poly(ester‐amide‐imide)s (PEsAIs) with simultaneously bulky side groups, ester and amide bonds were synthesized by copolymerization of tert‐butylhydroquinone bis(trimellitate anhydride), p‐phthaloyl chloride and other monomers. These PEsAIs had glass transition temperatures (Tgs) in the range of 231–301 °C, coefficients of thermal expansion (CTEs) of 17–59 ppm K−1 and displayed good mechanical properties with tensile modulus of 2.6–4.5 GPa, tensile strengths of 63–143 MPa and elongations at break of 3.0%–11.7%. All films had good transparency with transmittances at 400 nm (T400nm) of 43%–80%. The introduction of p‐phthaloyl chloride successfully improved the properties of the polymer with higher transmittance, higher Tg and lower CTE. In particular, PEsAI‐b‐60 presented the best comprehensive performance with a moderate Tg of 301 °C, low CTE of 17 ppm K−1 and high transmittance (T400nm) of 75%. © 2023 Society of Industrial Chemistry.