Higher Tg Values Research Articles

Aggregation−induced red−shift emission from self-assembled planar naphthalene diimide dye: Interlayer in a Schottky-type photodiode and DFT studies

In this study, a planar, soluble, thin film-forming and self-assembled small naphthalene diimide (3) molecule with a subtle moiety at the imide-nitrogen was synthesized, and applied for the first time in literature as an interfacial layer between Al and p-Si layers in a Schottky-type photodiode. The morphology of the compound was examined by scanning electron microscopy (SEM) and atomic force microscopy (AFM). The thin film structure and morphology affected the optical and electrical properties. The energy levels of the highest occupied molecular orbitals and lowest unoccupied molecular orbitals of 3 were calculated as −6.14 eV and −4.02 eV, corresponding to the band gap of 2.12 eV consistent with density functional theory (DFT) results. Differential scanning calorimetry (DSC) studies revealed a relatively high Tg value at 208 °C, indicating high-temperature applicability of the crystalline structure. The I–V measurements of Al/3/p-Si heterostructure were performed under dark and various light power intensities. The current steadily rose with each incremental 20 mW increase in light intensity. The reverse current increased almost 10-fold at 100 mW/cm2 illumination compared to dark measurement. The photodiode's responsivity, photosensitivity, and detectivity factors were elucidated. The photodiode's characteristic values, such as Io, n, ϕb, and Rs, were obtained as 3.50 × 10−6 A, 8.24, 0.588 eV and 2.266 kΩ, respectively. The fabricated Schottky-type diode showed promising results for the optoelectronic field. The compound's perfect solubilities in a wide range of solvents, processability, excellent chemical and photochemical stabilities, and exciting optical, thermal and electrochemical properties make it an ideal candidate for thin film and molecular electronics applications.

Preparation and properties of phosphorus-containing thermotropic liquid crystal copolyester fibers with excellent flame retardance and mechanical property

In order to acquire polymeric fibers have both excellent flame retardance and mechanical properties, high molecular weight phosphorus-containing liquid crystal copolyesters derived from 6-hydroxy-2-naphthenic acid (HNA), terephthalic acid (TA) and 10-(2,5-dihydroxypheny)-10-hydro-9-oxa-10-phospha phenanthrene-10-oxide (DOPO-HQ) were synthesized via “one-pot” melt polymerization, and then the fibers were obtained by melt spinning method. The structure and property of the copolyesters were studied elaborately by experimental characterization technique and molecular simulation method. Shear shinning behavior was observed from rheology measurement, indicating that the copolyesters had excellent melt fluidity and spinnability. The rigidity of molecular chain was efficiently improved by the phosphorus-containing monomer DOPO-HQ and naphthalene HNA units which could be reflected by the molecular simulation results as well as high Tg values. The flame retardant mechanism of the phosphorus-containing flame retardant copolyester was systematically studied via limiting oxygen index (LOI), vertical burning (UL-94) test, cone calorimetry, scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy (XPS). The results showed that the copolyesters exhibit synergistic flame retardant mechanism of gas phase and condensed phase. Meanwhile, mechanical property of the as-spun fibers could be significantly improved by increasing the spinneret draw ratio (SDR) attributed to high molecular chain orientation. The maximum tensile strength of the as-spun fiber was 0.77 GPa observed for P-HNA60P20 at a relatively low SDR of 29. It was shown the unique combination of good thermal stability, spinnability as well as mechanical and flame retardant properties of the copolyesters would make them could be used as high-performance flame retardant materials.

Lipid profile in patients with acute coronary syndrome undergoing cardiac rehabilitation. Characteristics and effects of the program. The importance of small and dense LDL (LDLpd)

Abstract Funding Acknowledgements None. Introduction Recently it has been shown that not all lipid risk for atherosclerosis is due to LDL cholesterol. Both remnant particles and small and dense LDL (LDLpd) have been associated with a higer risk of the first cardiovascular events and recurrences. Methods We analyzed the lipid profile at admission of patients undergoing a cardiac rehabilitation (CR) program in a tertiary referral hospital, in association with other analytical parameters, clinical characteristics and outcomes of CR in these patients. We collected data from patients who completed the programme between January 2022 and March 2023 on admission and at the end of the programme. Clinical and anthropometric data and the results of the stress tests were collected. We defined a TG/HDL ratio greater than 2 as being associated with the presence of small and dense LDL. Results 170 patients who had complete analytical profiles at hospital admission were included, 80.5% were male with a mean age 57.9+/-9 years, 92.5% were referred after an acute coronary syndrome, 25.6% were diabetic, 56.6% were smokers and 37.7% were obese. LDLpd at hospital admission was present in 73.4% of the patients. Male gender was more likely (86.3 vs. 68.9%, p=0.01, p=0.01) as well as being obese (83.9 vs 68.8%, p=0.04). No differences were found in terms of age, presence of DM, smoking or peripheral arterial disease. Nor did functional capacity or baseline quality of life. Less improvement was found in the SF 36 questionnaire (-6 vs +20, p=0.011), but similar in ergometry. Basal lipid profile was associated with higher total Ch values (173 vs 149, p=0.002), Ch LDL (104 vs 79, p=0.000), remnants (32 vs 14, p=0.000). As for baseline LDL, 51.6% with LDLpd,had it high LDL Ch>100 mg/dl, compared to 22.2% of those without LDLpd (P=0.002). As for the profile at discharge, we found that 63.5% still had LDLpd at discharge from the CR program ( vs. 15.9% of those without elevated LDLpd, P=0.000) and 22% had elevated remnants (P=0.002). After CR, these patients still had higher TG values (128 vs 81, p=0.000), lower HDL-C (44 vs 56, p=0.003) and higher remnants (24 vs 17, p=0.000) despite the fact that a greater decrease in remnants and TG/HDL in this group. Conclusions More than one third of the patients who undergo a Cardiac Rehabilitation Program in our centre have LDLpd. Initially, male and obese patients have higher LDL and remnants. A weaker effect of the CR program in improving the lipidic profile has been observed in those patients. Consideration should be given to enhance lipid-lowering and intensive weight-loss treatments to decrease cardiovascular risk in this population.

The importance of remnant cholesterol particles.Lipid profile in patients with acute coronary syndrome undergoing cardiac rehabilitation

Abstract Funding Acknowledgements None. Main funding source(s): Ninguno. Introduction Recently it has been shown that not all lipid risk for atherosclerosis is due to LDL cholesterol. Both, remnant and small particles have been proposed as risk factors for the first cardiovascular event and recurrences. Methods This is an observational, descriptive, prospective, single-centre, descriptive study. We set out to analyse the lipid profile on admission of patients undergoing a cardiac rehabilitation (CR) program in a tertiary hospital. In addition, we studied the association with other analytical parameters, clinical characteristics and CR results in these patients. For this purpose, data were collected from patients who completed the program between January 2022 and March 2023. We compared analytical variables at hospital admission and at the end of the program, as well as clinical and anthropometric data and stress test results. In our study we defined elevated remnants as >30 mg/dl. Results We included 170 patients who had a complete analytical profile at hospital admission. In our cohort, 80.5% were male, with a mean age of 57.9+/-9 yrs. A total of 92.5% were referred after acute coronary syndrome. There were 25.6% diabetic, 56.6% smokers and 38.1% obese patients. Patients with elevated remnants were more likely to be men (90.3 vs 79.8%, p=0.039). No differences were found in age, presence of DM, smoking, obesity or peripheral arterial disease. Functional capacity, quality of life and improvement in these parameters did not differ either. As for baseline lipid profile, it was associated with higher total Ch (190 vs 152, p=0.0), LDL Ch (109 vs 90, p=0.0), TG (227 vs 104, p=0.0) and TG/HDL ratio (6.8 vs 2.5, p=0.0) and lower HDL Ch (37 vs 45, p=0.0). 66.1% of patients with high remnants have an LDL-Ch greater than 100 mg/dl, compared with 29.6% of those with low remnants.(P=0,000). Regarding the profile at discharge, we found that 34.4% still had elevated remnants at discharge from the CR program (vs 22.2% of those without elevated remnants, P=0.000) and that 75.9% had TG/HDL greater than 2. After CR, these patients still had higher TG values (156 vs 93, p=0.000), lower HDL-C (43 vs 50, p=0.003) and higher TG/HDL ratio (4 vs 2, p=0.000), despite a greater decrease in remnants and TG/HDL in this group. Conclusions More than one third of patients undergoing a Cardiac Rehabilitation Program in our hospital have elevated cholesterol remnants. These particles predominate in male patients and initially, they have a higher prevalence of small and dense LDL and lower HDL cholesterol. In addition, the effect of the cardiac rehabilitation program on the improvement of lipid risk parameters is lower. More powerful intensive treatments are needed to improve cardiovascular risk in this population.

Monomer ratio‐controlled polyimides with enhanced dielectric properties and thermal stabilities through crosslinking network

AbstractPolyimides (PI) are considered as one of the most used materials for flexible printed circuit board substrates because of their excellent thermal stabilities, outstanding mechanical properties, and great dielectric properties. Dielectric constants (Dk) of common commercial PIs, however, are still above 3.0 (at 10 GHz), which is still substandard for high‐frequency applications. In this study, we develop thermally stable PIs with enhanced dielectric properties by structural design and crosslinking. Stiff aromatic 2,2′‐bis(trifluoromethyl)benzidine (TFMB) and soft aliphatic dimer diamines (DDA, priamine), including priamine 1074 (DDA‐1) and priamine 1071 (DDA‐2), are used as the diamines, and cyclobutanetetracarboxylic dianhydride (CBDA) is used as the dianhydride. By adjusting the ratio of the diamines, a series of PIs (PI‐1–PI‐5) with high thermal stabilities and low‐Dk values are synthesized. Among these PIs, PI‐4 synthesized by diamines with the ratio of TFMB:DDA‐1:DDA‐2 = 85:10:5, possesses relatively good performances. Therefore, PI‐4 is further chosen to be thermally crosslinked. By changing the contents of the crosslinker, triallyl isocyanurate (TAIC), crosslinked PIs (CPIs) are synthesized. The resulting CPIs have a significant improvement in thermal properties, dielectric properties, and mechanical strengths. Especially, for the CPI‐4‐30, in which 30% of TAIC is used, the glass transition temperature (Tg) increases by 20°C, the Dk decreases from 2.62 to 2.41, and the ultimate tensile strength boosts from 91.65 to 115.16 MPa. The CPIs with low Dk and high Tg values may have great potential as substrate materials for broad applications, such as microelectronics and integrated circuit packages.

A renewable tricyclic building block towards synthesis of biobased polyesters with high-performance and hydrolyzability

The development of biobased polyesters which concurrently achieve high‐performance and hydrolyzability, is a significant challenge. Here N,N′-trans-1,4-cyclohexane-bis(pyrrolidone-4-methyl carboxylate) (CBPC), a tricyclic diester, was prepared by Michael addition-cyclization from renewable feedstocks. Single-crystal X-ray revealed an unfolded skeleton of CBPC, in which two pyrrolidones symmetrically disposed in non-planar space around the cyclohexane. CBPC exhibited a high reactivity to be polymerized with various diols to generate biobased polyesters with high number-average molecular weight over 40 kDa. The tricyclic structure imparts the high glass transition temperature (Tg) (over 100°C), tough mechanical properties (tensile strength up to 56.8 MPa) as well as noticeable hydrolytic degradation to the resulting polyesters, which exhibit great potential to compete with commercial polyesters of polyethylene terephthalate (PET), polylactic acid (PLA) and polybutylene terephthalate (PBT). The hydrolytic pathway and reactivity site of the polyesters were further elucidated by the theoretical calculation. Note that PBT, PET and PLA are extremely reluctant to hydrolyzation, a higher sensitivity to hydrolysis is desired for high-performance polyester to reduce environmental impact. Overall, this work addresses some critical requirements for high-property polyesters which concurrently achieve high Tg values, tough mechanical properties, wide process windows, and hydrolysis quality.

Design, Synthesis and Properties of Semi-Alicyclic Colorless and Transparent Polyimide Films with High Glass Transition Temperatures and Low Retardation for Potential Applications in Flexible Electronics.

Polyimide (PI) optical films with high glass transition temperatures (high-Tg), high optical transparency, and low optical retardations (low-Rth) are highly desired in advanced optoelectronic applications. However, the standard PI films usually suffer from deep colors, high optical anisotropies and limited Tg values. In the current work, a series of semi-alicyclic colorless and transparent PI (CPI) films were developed from hydrogenated pyromellitic dianhydride stereoisomers, 1S,2R,4S,5R-hydrogenated pyromellitic dianhydride and 1R,2S,4S,5R-hydrogenated pyromellitic dianhydride, and fluorene-containing diamines, including 9,9-bis(4-aminophenyl)fluorene and 9,9-bis(3-fluoro-4-aminophenyl)fluorene, respectively. The derived CPI films showed Tg values higher than 420 °C according to differential scanning calorimetry measurements. In addition, the fluorene-based CPI film showed optical transmittances higher than 80% at the wavelength of 400 nm, with yellow indices in the range of 0.60~1.01 and haze values below 3.0%. The CPI films showed average refractive indices from 1.5407 to 1.6309, extremely low birefringence at the level of minus fourth power of ten, and further exhibited quite low optical retardations below 10 nm.

Enhancement of saltwater ageing behavior of nanocomposites and lap joints with boron nanoparticles

The presented research aims to enhance the ageing performance of nanocomposites and bonded joints in the saltwater medium with boron nanoparticle doping. Epoxy nanocomposites and bonded aluminum 2024-T3 joints doped with 2 wt% silane-functionalized boron carbide (B4C) and boron nitride (BN) nanoparticles and undoped were produced for that purpose. The produced samples were immersed in a saltwater (10% NaCl) solution at 40 °C for 480, 960 and 1440 h. By performing the weight change test, Fourier transform infrared (FT-IR) spectroscopy, dynamic mechanical analysis (DMA), differential scanning calorimetry (DSC), tensile test and scanning electron microscope (SEM), the research aimed to comprehensively assess the changes in the properties of nanocomposites and lap joints after exposure to saltwater ageing, shedding light on the effectiveness of boron nanoparticle doping in improving their performance in saltwater environments. The result showed that thanks to the anti-plasticisation behaviour of nanoparticles, 18.4% and 19.6% higher Tg values were obtained in B4C and BN-doped nanocomposites after 1440 h of ageing, respectively. Similarly, the static tensile strength of the undoped composite decreased by 22%, while B4C and BN-doped nanocomposites decreased by 15% and 14%, respectively, at the end of ageing. After 1440 h, the storage modulus of undoped, B4C and BN-doped nanocomposites decreased by 24.2%, 15.3% and 11.9%, respectively. It was found that B4C and BN-doped bonded joints performed superior mechanical properties compared to their undoped counterparts. The joints doped with B4C and BN nanoparticles carried 50% and 52% higher loads than the undoped joint.

Aromatic Polyimide Membranes with tert-Butyl and Carboxylic Side Groups for Gas Separation Applications-Covalent Crosslinking Study.

A set of aromatic copolyimides was obtained by reaction of 4,4'-(hexafluoroisopropylidene) diphthalic anhydride (6FDA), and mixtures of the diamines 1,4-bis(4-amino-2-trifluoromethylphenoxy)-2,5-di-tert-butylbenzene (CF3TBAPB) and 3,5-diamino benzoic acid (DABA). These polymers were characterized and compared with the homopolymer derived from 6FDA and CF3TBAPB. All copolyimides showed high molecular weight values and good mechanical properties. The presence of carboxylic groups in these copolymers allowed their chemical crosslinking by reaction with 1,4-butanediol. Glass transition temperatures (Tg) were higher than 260 °C, showing the non-crosslinked copolyimides had the highest Tg values. Degradation temperature of crosslinked copolyimides was lower than their corresponding non-crosslinked ones. Mechanical properties of all polymers were good, and thus, copolyimide (precursor, and crosslinked ones) films could be tested as gas separation membranes. It was observed that CO2 permeability values were around 100 barrer. Finally, the plasticization resistance of the crosslinked material having a large number of carboxylic groups was excellent.

Influence of Polymer Polarity and Association Strength on the Properties of Poly(alkyl ether)-Based Supramolecular Melts

The present work focuses on the impact of polymer polarity and hydrogen-bonding (H-bonding) end groups association strength on the structure and dynamics of poly(alkyl ether)-based supramolecular model polymers studied by means of small angle scattering (SAS), rheology, dielectric relaxation spectroscopy (DRS), and differential scanning calorimetry (DSC). These consist of poly(propylene oxide) (PPO) or poly(ethylene oxide) (PEO) backbone that self-assembly in the bulk via hydrogen bonding (H-bonding). Diaminotriazine (DAT) and thymine-1-acetic acid (THY) as well as 2-ureido-4[1H]-pyrimidinone (UPY) are the H-bonding end groups of choice. Both PPO and PEO bearing either DAT or THY as end groups associate into linear chains, but PPO-THY/DAT forms longer chains in comparison with PEO-THY/DAT. The lower polarity of the backbone results in stronger associations for the same end groups. However, the temperature dependence of the association/dissociation lifetimes for this H-bonding type is independent of the different main chain polarity as these breaking times do not exceed the rouse chain dynamics as expected within the Cates model. PPO-UPY forms a transient network characterized by the interplay between small transient bonds controlled by the characteristic times of association/dissociation between pairs of UPY groups involving probably just two ends, revealed by the similar dielectric spectra with PPO backbone, and a more stable bond type of associate that forms phase separated UPY clusters. The latter are responsible for the physical cross-links in the network and result in the rubbery-like plateau of the rheological spectra. PPO-UPY has similar structure to PEO-UPY, as validated by small angle scattering, but the UPY detachment times in the clusters are longer for PEO-UPY than for PPO-UPY, though the activation energies are very close and match the typical energy barrier specifically imposed by the hydrogen bonds. Moreover, while the segmental relaxation times and the glass transition temperature (Tg) of PPO-UPY is similar to PPO, PEO-UPY has the highest Tg value and a much slower segmental relaxation as compared to PEO and PPO based supramolecular polymers. This seems to indicate that the H-bonding association dynamics of the UPY groups is strongly influenced by the main chain polarity that play a fundamental role in defining the time scale of the association process.

Sustainable ABA triblock methacrylate copolymers incorporating both high and low Tg terpene-derived monomers

We report the synthesis of novel terpene-based monomers: nopinyl acrylate and methacrylate, from naturally abundant β-pinene. A very high Tg value was observed for poly(nopinyl methacrylate) when synthesised by free radical polymerisation, and well-defined polymers have been produced via RAFT polymerisation. This exciting new high Tg material shows promise as a hard block in thermoplastic elastomers. ABA triblock copolymers have been synthesised which also incorporate a low Tg renewable soft block, poly(tetrahydrogeraniol methacrylate), using a divergent, difunctional RAFT polymerisation method. Initial phase separation behaviour and adhesive properties have been investigated to highlight the potential of these copolymer materials as renewably sourced thermoplastic elastomers.

Effect of sulfonating agent in the properties of styrene copolymers for PEMFC membranes

Two different sulfonating agents: sulfuric acid (S) and acetyl sulfate (AcS) were evaluated for chemical modification of poly (styrene-co-butyl acrylate) (StBuA) copolymer, as low-cost membranes. The reaction was carried out by direct sulfonation during 2–5 h of sulfonation time. FTIR confirmed sulfonation through the presence and widening of the several SO3H characteristic absorption bands. The molecular weight decreased after sulfonation, compared with pristine StBuA. TGA thermal analysis showed stability over 150 ᵒC with residues suggesting crosslinking and a glass transition (Tg) enhanced. Even with higher Tg values, sulfonated copolymers became flexible, as seen by their lower complex modulus (E∗). Ion exchange capacity (IEC) ranged from 0.91 to 1.53 meq g−1 and degree of sulfonation (DS) from 7 to 40%. The proton conductivity for sulfonated membranes exhibited similar or higher to Nafion membrane, particularly for S-4h membranes. A Grotthuss mechanism is envisaged for AcS and vehicular mechanism for S membranes.

Cleavable epoxy networks using azomethine-bearing amine hardeners

This work is a proof-of-concept of the use of azomethine-bearing diamines as novel hardeners of standard epoxy compounds to yield cleavable and thermoformable covalent adaptable networks (CANs), with functional properties otherwise comparable to conventional epoxy networks. A suitable aromatic diamine (TPA-o-PD) was synthesised at acceptable purity for the intended use and successfully reacted with DGEBA. The resulting azomethine-bearing cured epoxy networks exhibited glass transition temperature values and a thermal stability profile similar to conventional epoxy network counterparts. In contrast to their conventional counterparts however, the azomethine-bearing networks were shown to dissolve in mixtures of chloroform and methanesulfonic acid, due to acid hydrolysis of at least some of the azomethine bonds of the network. The resulting recyclate material after evaporating the solvent was consistent with the profile of a thermoplastic polymer of high molecular weight, suggesting limited depolymerisation/network cleavage during dissolution in the chloroform/methanesulfonic acid mixture. The recyclates were soluble in polar aprotic solvents and showed good thermal stability, high Tg and molecular weight values, consistent with the attributes of engineering thermoplastics. Lastly, the cured networks were shown to be thermoformable at 200 °C, yielding self-standing films with only minor reduction of properties.

Double-Decker-Shaped Polyhedral Silsesquioxanes Reinforced Epoxy/Bismaleimide Hybrids Featuring High Thermal Stability.

In this study, we synthesized bismaleimide into a functionalized double-decker silsesquioxane (DDSQ) cage. This was achieved by hydrosilylation of DDSQ with nadic anhydride (ND), reacting it with excess p-phenylenediamine to obtain DDSQ-ND-NH2, and treating with maleic anhydride (MA), which finally created a DDSQ-BMI cage structure. We observed that the thermal decomposition temperature (Td) and char yield were both increased upon increasing the thermal polymerization temperature, and that these two values were both significantly higher than pure BMI without the DDSQ cage structure since the inorganic DDSQ nanoparticle could strongly enhance the thermal stability based on the nano-reinforcement effect. Based on FTIR, TGA, and DMA analyses, it was found that blending epoxy resin with the DDSQ-BMI cage to form epoxy/DDSQ-BMI hybrids could also enhance the thermal and mechanical properties of epoxy resin due to the organic/inorganic network formation created by the ring-opening polymerization of the epoxy group and the addition polymerization of the BMI group due to the combination of the inorganic DDSQ cage structure and hydrogen bonding effect. The epoxy/DDSQ-BMI = 1/1 hybrid system displayed high Tg value (188 °C), Td value (397 °C), and char yield (40.4 wt%), which was much higher than that of the typical DGEBA type epoxy resin with various organic curing agents.

Dynamics of Poly(cyclohexene carbonate) as a Function of Molar Mass

Stereoregular poly(cyclohexene carbonate) (PCHC) homopolymers were prepared via copolymerization of cyclohexene oxide and carbon dioxide (CO2) using (R,R)-(salcy)-CoCl and bis(triphenylphosphine)iminium chloride as a catalyst. The homopolymers had molar masses in the range of 4800–33,000 g mol–1 and relatively narrow dispersity after careful fractionation, as required for the molecular dynamics investigation. We employed differential scanning calorimetry and dielectric spectroscopy, the latter as a function of temperature and pressure, for investigating the thermal properties and the molecular dynamics, respectively. The segmental dynamics in the vicinity of the liquid-to-glass temperature was very complex. The dual segmental processes were inseparable by decreasing the temperature or by increasing the pressure. Based on DFT calculations of the dipole moment, they were ascribed to different stereo sequences of the PCHC backbone. The limiting glass temperature, Tg, for very high molar masses was ∼125 °C. The high Tg value obtained herein well justifies its application as a CO2-based alternative for polystyrene (PS) in a variety of materials based on block copolymers. Moreover, fragility increased with increasing molar mass with values intermediate to poly(styrene) and poly(cyclohexyl methacrylate). The flexible cyclohexyl group in PCHC undergoing intramolecular chair-to-chair conversion increases the packing ability and consequently decreases the fragility. PCHC is a brittle material because it lacks entanglements even for the higher molar masses investigated herein, which is relevant for application as a PS substitute. Within the investigated range of molar masses, the dependences of the terminal relaxation times, τΝΜ, and of the zero-shear viscosity, ηο, on the molar mass, M, are τΝΜ/τSM ∼ M3.2 and ηο ∼ M1.4, revealing an intermediate behavior between Rouse and entangled chains.

Direct Synthesis of Thermally Stable Semiaromatic Polyamides by Bulk Polymerization Using Aromatic Diamines and Aliphatic Dicarboxylic Acids.

Semiaromatic polyamides were directly synthesized by bulk polycondensation of aliphatic dicarboxylic acids (with 5, 6, 7, and 10 carbon numbers) and aromatic diamines (4,4′-oxydianiline and 4,4′-diaminodiphenylmethane) under natural pressure. In addition, copolyamides were successfully obtained by the copolymerization of aliphatic dicarboxylic acids, aromatic diamines, and biobased amino acid, 4-aminohydrocinnamic acid. The obtained polyamides had relatively high inherent viscosity values of 0.35–0.76 dL/g. The obtained polyamides exhibited good thermal stability with Td5% in the range of 316–416 °C, even when incorporated with aliphatic methylene units. In particular, some copolyamides (2AO, 2PO, and 2GM) had high Tg values of 150, 158, and 156 °C and relatively low Tm values of 277, 288, and 234 °C, respectively, which may be preferable thermal properties for melt-drawing processes.

Revealing the mechanism of lignin re-polymerization inhibitor in acidic pretreatment and its impact on enzymatic hydrolysis

Phenolic additives, including 2-naphthol, 2-naphthol-7-sulfonate, and resorcinol were evaluated for their impact on the lignin re-polymerization and subsequent hydrolysis of bamboo residues. Low surface lignin concentration (65.68%) of the substrate and high Tg value (185 °C) of lignin was observed for 2-naphthol-7-sulfonate assisted pretreatment, leading to the most significant increase (14%) in enzymatic hydrolysis efficiency of pretreated bamboo residues. Meanwhile, physicochemical properties of lignin revealed that the introduced sulfonic acid groups increased the surface charge, decreased the molecular weight, promoted the cleavage of β-O-4 linkages, and prevented the re-condensation of lignin. Even though resorcinol-assisted pretreatment, by contrast, was found to be an inhibitor for enzymatic hydrolysis. NMR analysis of modified lignin showed that resorcinol led to a higher amount of non-condensed phenolic OH groups and promoted the cleavage of β-O-4 linkages, acting as an inhibitor in lignin re-polymerization during the dilute acidic pretreatment. In short, the above findings present a detailed view of suppressing lignin re-polymerization for boosting the utilization of bioresources with acidic pretreatment.

High-Tg and Degradable Isosorbide-Based Polybenzoxazine Vitrimer

This work describes new fully bio-based vitrimers prepared from isosorbide, a renewable sugar-based chemical. Isosorbide was reacted with 4-hydroxypropionic acid, paraformaldehyde, mono-ethanolamine, and/or furfurylamine via consecutive solvent-free Fischer esterification and Mannich-like ring-closure reactions. The two-step synthesis led to the formation of a di-telechelic benzoxazine-terminated isosorbide monomer, containing ester bonds and aliphatic hydroxyl and/or furan groups. The atom economy factor yields 85%. The structural features of the resulting products were substantiated by spectroscopic techniques. The ring-opening polymerization was monitored by rheological and differential scanning calorimetry (DSC) measurements. Very high Tg values afforded by the isosorbide substructure were measured (from 143 to 193 °C), which increase with furan ring content. Internally catalyzed transesterification reactions conferred fast dynamic exchanges (τ* = 300 s at 180 °C). Self-healing and chemical and mechanical recycling were also demonstrated. Finally, the degradability of the sugar-based polybenzoxazine vitrimers was demonstrated as well. The materials were highly stable in pH-neutral water, even at 80 °C for 60 days, but owing to the isosorbide structure, pronounced degradation was observed under acidic or alkaline conditions. In summary, isosorbide is a suitable building block for the design of degradable and 100% recyclable high-Tg polybenzoxazine vitrimers.

Tuning thermal properties and biodegradability of poly(isosorbide azelate) by compositional control through copolymerization with 2,5-furandicarboxylic acid

A new fully biobased poly(isosorbide furanoate-co-azelate) (PISFAz) copolyester series was synthesized through melt polycondensation. Incorporation of 2,5-furandicarboxylic acid (FDCA), a rigid comonomer, at different molar ratios in poly(isosorbide-azelate) homopolymer led to tuning of the thermal properties and biodegradability of the resulting copolyesters. The PISFAz copolyesters with various FDCA molar content spanning from 10 to 70% were prepared and characterized by FTIR, GPC, 1D/2D NMR and viscosity measurements. It was found that PISFAz were totally amorphous materials with high thermal stability. NMR results indicated that random microstructures were obtained for the prepared copolymers with high azelaic acid content (⩾ 60 mol%). Most notably, the inclusion of FDCA units into the copolymer molecular chains induced a significant increase in the glass transition temperatures (Tg) that varied from 9.2 to 91.1 °C depending on FDCA content, leading to copolyesters with tunable Tg over a wide temperature window. The enzymatic hydrolysis behavior of PISFAz was assessed using lipases from Pseudomonas cepacia and Rhizopus oryzae revealing different susceptibility to enzymatic attack depending on the comonomer ratio, with a maximum degradation rate up to 61% after 30 days. These novel furanoate-based copolyesters show great potential to serve as promising green thermoplastic materials for applications requiring high Tg values.

Thiol‐yne photoclick polymerization as a method for preparing imidazolium‐containing ionene networks

AbstractHerein, the thiol‐yne photoclick reaction was utilized as a method for synthesizing imidazolium‐containing ionene networks whereby a bisalkynyl‐functionalized imidazolium [NTf2] ionic liquid was polymerized with the tetrafunctional thiol PTMP (pentaerythritol tetrakis(3‐mercaptopropionate)). The thiol:yne functional group ratio was varied in order to examine the breadth of thermal, mechanical, and conductive properties available from the resulting networks. The stoichiometric 1:1 thiol:yne network exhibited very high thiol and alkyne conversions by FT‐IR spectroscopy and a gel fraction greater than 95%. The highest Tg value (3.5°C) and stress at break (1.13 MPa) were also observed for this network. As either thiol or alkyne functional group concentration was increased, the networks were noticeably lower in Tg and stress at break with a modest increase in % elongation. Ionic conductivities were found to be on the order of 10−9 to 10−7 S/cm at 30°C. Normalization of the ionic conductivity curves did not lead to a complete collapse meaning that the observed differences in conductivity are not solely dependent upon Tg. When compared to analogous imidazolium‐containing, thiol‐ene ionene networks, the thiol‐yne networks were found to be slightly more mechanically robust, but approximately one order of magnitude lower in terms of ionic conductivity.