High Tg Research Articles

Release Enhancement by Plasticizer Inclusion for Amorphous Solid Dispersions Containing High Tg Drugs.

Plasticizers are commonly used in the preparation of amorphous solid dispersions (ASDs) with the main goal of aiding processability; however, to the best of our knowledge, the impact of plasticizers on drug release has not been explored. The goal of this study was to evaluate diverse plasticizers, including glycerol and citrate derivatives, as additives to increase the drug loading where good drug release could be achieved from copovidone (PVPVA)-based dispersions, focusing on high glass transition (Tg) drugs, atazanavir (ATZ) and ledipasvir (LED). ASDs were prepared using the high Tg compounds, atazanavir (ATZ) and ledipasvir (LED), as model drugs. Release was evaluated using surface normalized dissolution testing. Differential scanning calorimetry was used to measure glass transition temperature and water vapor sorption was performed on select samples. The presence of a plasticizer at 5% w/w for ATZ and 10% w/w for LED ASDs, led to improved drug release. For ATZ ASDs, in the absence of plasticizer, release was very poor at drug loadings of 10% w/w and above. Good release was obtained for plasticized ASDs up to a drug loading of 25%. The corresponding improvement for LED was from 5 to 20% DL. Interestingly, for a low Tg compound, ritonavir, relatively smaller improvements in release as a function of drug loading were achieved through plasticizer incorporation. The use of plasticizers represents a potential new strategy to increase drug loading in ASDs for high Tg compounds with a low tendency to crystallize and may help improve a major limitation of ASD formulations, namely the high excipient burden.

Myeloperoxidase G-463A and CYBA C242T genetic variants in gestational diabetes mellitus.

Oxidative stress plays an important role in the pathophysiology of gestational diabetes mellitus (GDM). We investigated the relationship between NADPH oxidase p22phox subunit (CYBA) C242T (rs4673) and myeloperoxidase (MPO) G-463A (rs2333227) genetic variants and GDM in 719 patients with GDM and 1205 control women. Clinical, metabolic, and oxidative stress parameters were analyzed. We found that frequencies of the A allele (15.6% vs 12.3%) and GA + AA genotype (28.5% vs 23.2%) of the MPO G-463A variation were significantly higher in patients with GDM than in the control women (OR = 1.318, 95% CI: 1.068-1.625, P = 0.010 for the dominant model; OR = 1.999, 95% CI: 1.040-3.843, P = 0.034 for the recessive model; OR = 1.320, 95% CI: 1.095-1.591, P = 0.004 for the allele model). Genotype GA + AA remained a significant predictor of GDM in a logistic regression model including age and BMI at delivery (OR = 1.282, 95% CI: 1.037‒1.583, P = 0.021). Furthermore, the ‒463A allele was associated with higher TG and the 242T allele was related to higher pre-pregnancy BMI and oxidative stress index in all subjects (P < 0.05). The 242T allele was also associated with higher homeostatic model assessment of insulin resistance but lower serum total antioxidant capacity in patients with GDM (P < 0.05). We conclude that the MPO G-463A, but not the CYBA C242T, genetic variation is associated with an increased risk of GDM in Chinese women. These two genetic polymorphisms may be linked to obesity, dyslipidemia, insulin resistance, and oxidative stress.

Abstract P133: Deficient Screening for Cardiometabolic Risk Factors in a Central Appalachian Health System

Problem: West Virginia perennially leads the US in child obesity and adult heart disease. We had screened over 100,000 school children for cardiometabolic risk factors (CMRF) in the Coronary Artery Risk Detection in Appalachian Communities (CARDIAC) program over 20 years until the 2017 economic downturn. 60,000 had lipid panels. WVU Health System includes encounters with over 200,000 WV children. We hypothesize that CMRF screening has decreased without the statewide CARDIAC Program. Methods: We queried our instance of Epic Electronic Health Record that includes much of northern WV to ascertain BMI, Total Cholesterol (TC) , Low Density Lipoprotein Cholesterol (LDL), triglyceride level (TG) and hemoglobin A1C. We also searched for use of cholesterol-lowering medicines. Results: 137,566 children under 18 years had a BMI measure and we have reported a 5%ile increase in the COVID era. Only 8498 have had a total cholesterol check (avg ± SD 159+34 mg/dl), 9964 had triglyceride (109 ± 74 mg/dl) and 4874 had LDL (92.04 ± 29.8 mg/dl). 2609 children had average HA1C 6.03 ± 1.7%. 607 children had LDL ≥ 130 mg/dl including 174 with LDL ≥ 160 mg/dl. 33 were given lipid-lowering medication and had LDL change from 248 ± 86 mg/dl to 181 ± 42 mg/dl at follow-up. Average decrease was 67 ± 79 mg/dl (p &lt; 0.0001). Conclusion: Few children are being screened for TC, LDL and TG absent the statewide CARDIAC lipid screening program in WV. Lipid-lowering medicines are sparsely used in children with significant risk of Familial Hypercholesterolemia (FH). Family history is not available for the cohort. None in FH range were below the 130 mg/dl LDL target value after treatment. In this pediatric population with usual incidence of FH and high prevalence of dyslipidemia of obesity with high BMI and TG levels, little lipid screening is occurring without the statewide school-based program. Child health care providers need to intervene to prevent even greater WV coronary disease in the future. Policy-makers can impact the future health of WV school children by promoting and funding screening for cardiometabolic risk factors now.

Diffusion‐Limited Accepter Alloy Enables Highly Efficient and Stable Organic Solar Cells

AbstractOrganic solar cells (OSCs) are designed based on a blend of polymer donor and small molecular acceptor whereby the thermodynamic relaxation of the morphology raises the concerns related to operational stability. Herein, it is demonstrated that the classical Y6‐based binary device can be stabilized by using its derivative of ZCCF3 as the third component, which is designed with the replacing of the thiadiazole group on Y6 with the trifluoromethyl substituted diazepine unit. ZCCF3 delivers not only higher glass transition temperature (Tg) than Y6 but also have hyper‐miscibility with Y6, contributing to a favorable diffusion‐limited Y6:ZCCF3 alloy when blended with polymer donor. Consequently, a champion power conversion efficiency of 18.54% is achieved in the optimal PM6: Y6: ZCCF3 devices, which can retain their 80% initial efficiency of up to 360 h. This study highlights the importance of high Tg of the third component and its derived hyper‐miscible accepter alloys in achieving highly efficient and stable OSCs.

A Comparison of Spray-Drying and Co-Precipitation for the Generation of Amorphous Solid Dispersions (ASDs) of Hydrochlorothiazide and Simvastatin

Co-processing of APIs, the practice of creating multi-component APIs directly in chemical processing facilities used to make drug substance, is gaining increased attention with a view to streamlining manufacturing, improving supply chain robustness and accessing enhanced product attributes in terms of stability and bioavailability. Direct co-precipitation of amorphous solid dispersions (ASDs) at the final step of chemical processing is one such example of co-processing. The purpose of this work was to investigate the application of different advanced solvent-based processing techniques - direct co-precipitation (CP) and the benchmark well-established spray-drying (SD) process - to the production of ASDs comprised of a drug with a high Tg (hydrochlorothiazide, HCTZ) or a low Tg (simvastatin, SIM) molecularly dispersed in a PVP/VA 64 or Soluplus® matrix. ASDs of the same composition were manufactured by the two different methods and were characterised using powder X-ray diffraction (PXRD), modulated differential scanning calorimetry (mDSC), attenuated total reflectance Fourier transform infrared spectroscopy (ATR-FTIR) and scanning electron microscopy (SEM). Both methods produced ASDs that were PXRD amorphous, with some differences, depending on the process used, in glass transition temperature and particle size distribution. Irrespective of manufacturing method used, all ASDs remained PXRD amorphous when subjected to high relative humidity conditions (75% RH, 25°C) for four weeks, although changes in the colour and physical characteristics were observed on storage for spray-dried systems with SIM and PVP/VA 64 copolymer. The particle morphology differed for co-precipitated compared to spray dried systems, with powder generated by the former process being comprised of more irregularly shaped particles of larger particle size when compared to the equivalent spray-dried systems which may enable more streamlined drug product processes to be used for CP materials. These differences may have implications in downstream drug product processing. A limitation identified when applying the solvent/anti-solvent co-precipitation method to SIM was the high antisolvent to solvent ratios required to effect the precipitation process. Thus, while similar outcomes may arise for both co-precipitation and spray drying processes in terms of ASD critical quality attributes, practical implications of applying the co-precipitation method and downstream processability of the resulting ASDs should be considered when choosing one solvent-based ASD production process over another.

Cardo polyimides with high Tg and transparency derived from bisphenol fluorenes and 1,4-bis(4-fluorophthalimide)cyclohexanes via aromatic nucleophilic substitution

Two series of transparent cardo polyimides (PIs) derived from bisphenol fluorenes and 1,4-bis(4-fluorophthalimide)cyclohexanes (BFCH) with different ratios of trans- and cis-1,4-diaminocyclohexane were prepared via aromatic nucleophilic substitution. These PIs exhibited high glass transition temperatures (Tgs) of 271–352 °C, 5% weight loss temperatures (Td5%) of 400–433 °C in nitrogen, mechanical properties of tensile strengths of 62–107 MPa, tensile moduli of 3.0–4.4 GPa and elongations at break of 1.7–4.5% and great solubility in a variety of organic solvents. These PI films appeared excellent optical transparency, which displayed the cut-off wavelengths from 323 to 355 nm and high transmittance at 450 nm with more than 85 %. The steric effects of different substituent groups on bisphenol fluorene and different ratios of trans/cis configuration were also investigated.

Mechanical properties of reactive polyetherimide-modified tetrafunctional epoxy systems

Highly crosslinked multifunctional epoxy resins are commonly brittle. Thermoplastic toughening agents have been used to improve the fracture toughness of crosslinked epoxy resins. However, toughness improvement is limited due to poor interfacial adhesion between epoxy matrix and thermoplastic toughener. Furthermore, it is desired that toughness improvements should not come at the expense of other properties, including modulus, thermal properties and processability. In this work, amine functionalized reactive polyetherimide (rPEI) having two different molecular weights and loading levels were incorporated in tetraglycidyl-4, 4′-diaminodiphenyl methane (TGDDM) epoxy resin to study the structure-property relationship, including effects of reaction-induced phase separation on fracture toughness. Results demonstrate that the phase morphologies of rPEI in an epoxy resin can be drastically affected by the functionality, molecular weight and loading levels of rPEI. The mode-I fracture toughness (KIC) of rPEI-toughened epoxy is increased by up to 140% versus untoughened epoxy control. An investigation into the fracture mechanisms of rPEI-toughened TGDDM epoxy showed evidence of rPEI particle bridging as one of the key mechanisms of toughening. Our work further demonstrated that the rPEI-toughened TGDDM epoxy maintained both high modulus and high Tg, rendering it suitable for a wide range of applications.

Recyclable and Reprocessable Epoxy Vitrimer Adhesives

Epoxy-based vitrimers represent a promising option toward sustainability and circular economy in automotive structural applications. In this work, a series of vitrimer materials are presented to be used as recyclable and reprocessable adhesives for such applications. These formulations consist of diglycidyl ether of bisphenol A-anhydride systems with glutaric anhydride and glycerol as cocuring agents in several proportions and 1,5,7-triazabicyclo[4.4.0]dec-5-ene (TBD) or 1-methylimidazole (1MI) as catalysts. The materials obtained revealed relatively high Tg s, up to 85 °C, as well as a homogeneous network structure. They also showed complete stress relaxation in times as short as just 3.6 min at 180 °C. The presence of TBD in the vitrimer allows the fastest relaxation. The thermosets were recycled and reprocessed through alcoholysis and mechanical grinding. These formulations were also applied as adhesives for mono- and multimaterial joints showing values of single-lap shear stress as high as those shown by commercial adhesives. Reversible adhesion was also studied after joint failure and after debonding without failure. In summary, the materials and methodology presented here represent a comprehensive study of recyclable and reprocessable epoxy-based vitrimers.

ENOS Glu298Asp (rs1799983) and AGT Met235Thr (rs699) polymorphisms in adverse cardiometabolic phenotypes: A study among Bhil tribal population of India

BackgroundCardiometabolic adversities constitute an enormous public health challenge. Along with lifestyle/socio-cultural determinants, disease outcome is modulated by genetic variants as well. Genetic polymorphisms like eNOS Glu298Asp (rs1799983) and AGT Met235Thr (rs699) have been identified as significant contributors to cardiometabolic phenotypes (obesity, hypertension and dyslipidemia) due to their role in vascular homeostasis, endothelial function, cardiac performance, etc. However, the association of these two genetic polymorphisms with cardiometabolic phenotypes among Indian Bhil tribal population have not yet been determined. MethodsThis was a cross-sectional study conducted among Bhil tribal population from India. The study recruited 297 participants aged 25–75 years through door-to-door household survey. Data on demographic and lifestyle variables were collected using a pre-tested modified interview schedule. Anthropometric (height, weight, waist circumference and hip circumference) and physiological (systolic and diastolic blood pressure) parameters were measured to define obesity and hypertension. Fasting blood samples were collected and serum was separated for lipid profiling (TC, TG, HDL-C, LDL-C and VLDL-C) and DNA was extracted from whole blood for genetic analysis (PCR-RFLP). Multivariable logistic regression was employed to identify association of genetic polymorphisms with cardiometabolic phenotypes. ResultsThe frequency of GG, GT and TT genotypes of eNOS rs1799983 were 52.86%, 45.45% and 1.68%, respectively and 0.24 minor allele frequency (MAF). The frequency of TT, TC and CC genotypes of AGT rs699 were 37.71%, 41.41% and 20.88%, respectively and 0.42 MAF. GT genotype and T allele (GT + TT genotypes) of rs1799983 were inversely associated with high WC, prehypertension, low HDL-C, and high LDL-C (all adjusted OR values <1 and p < 0.05). Conversely, TC and C allele (TC + CC genotypes) of rs699 were significantly associated with dyslipidemia, specifically high TC, TG and VLDL-C (all adjusted OR values >1.6 and p < 0.05). Also, individuals with the combination of high TC and TC genotype or C allele of rs699 appeared to have survival disadvantage at older age. ConclusionWith high frequency of AGT rs699 mutant C allele and significant association with dyslipidemia, our study suggests screening of candidate gene polymorphisms for cardiometabolic diseases among tribal populations to identify risk genotypes or alleles, which may pave way for future pharmacogenetic therapy and precision medicine.

Recyclable bio‐based epoxy resins containing hybrid cross‐linking networks

AbstractBio‐based “thiol‐epoxides” thermosets containing dynamic cross‐linked network topologies, permanent cross‐linking and recyclability have been successfully utilized in coatings, adhesives and composites. However, these materials typically have a low glass transition temperature and limited mechanical strength. Combining excellent mechanical properties with thermal properties remains a significant challenge. In this study, we developed a recyclable itaconic acid‐based epoxy thermoset material with high glass transition temperature and tensile strength through thiol‐olefin/thiol‐epoxy click reaction and alkyl bond radical copolymerization to construct a hybrid cross‐linked network. The tensile strength reached up to (105.9 MPa) while maintaining a high Tg (93.3°C), which is the highest value reported in the literature so far. In addition, the itaconic acid‐based epoxy has excellent recyclable processing, self‐healing properties, high hardness, solvent resistance, and surface bond strength as an adhesive and coating. The results hold potential applications in achieving sustainable development in coatings and adhesives.

Developing Reprocessable shape memory thermosetting resins with high thermal resistance and strength through building a crosslinked network based on bismaleimide and epoxy resins

AbstractIt is difficult to endow reprocessable shape memory thermosetting resins with outstanding heat resistance and high mechanical strength. Herein, a new kind of reprocessable shape memory thermosetting resins (DBE) are developed through building a crosslinked network based onN,N′‐4,4′‐diphenylmethane bismaleimide (BDM), bisphenol A epoxy resin and 4,4′‐dithiodiphenylamine. The influence of the composition of DBE resins on their structure and comprehensive properties was studied. Results show that DBE resins have multiple phase structures. With the increase of BDM content of DBE resin, the glass transition temperature (Tg), initial thermal decomposition temperature and flexural modulus increase, the impact strength and reprocessing efficiency decrease, while the flexural and tensile strengths increase initially and then decrease. 0.8DBE cannot be reprocessed, while 2DBE, 1.5DBE and 1DBE are reprocessable, and also have good shape reconfiguration and shape memory performances. Among them, 1DBE has the best integrated performance, which has attractively highTg(210°C), high tensile strength (76 ± 3.2 MPa), good reprocessability and excellent shape memory performance, its shape fixation rate and shape recovery rate reach 100% and 99.6%, respectively, overcoming the bottleneck problems of low heat resistance and insufficient mechanical strength of existing reprocessable shape memory thermosetting resins.

Poly (amino acid)s as new co-formers in amorphous solid dispersion

The drug-amino acid co-amorphous systems and amorphous solid dispersions (ASDs) are promising methods to address the poor water solubility of poorly water-soluble drugs. However, some amino acids might not be perfect co-formers for co-amorphous systems, and the relatively low drug-loading of many ASDs is one of the main disadvantages of ASDs. Thus, poly-l-lysine and polyglutamic acid were selected as the co-formers, ball milled with basic mebendazole, neutral tadalafil and acidic valsartan at different weight ratios (from 3:1 to 1:3) to prepare poly (amino acid)-based ASDs, aiming to combine the advantages of co-amorphous systems (high drug-loading) and ASDs (relatively high Tg and high physical stability). All the mixtures were converted into amorphous after milling. The powder dissolution studies showed that drug-poly (amino acid) ASDs improved the dissolution rate of the drug in different ways and to different degrees. Moreover, the two poly (amino acid)s enhanced the physical stability of amorphous drugs. It is worthy to mention that the salt formation between the drug and the poly (amino acid) does not necessarily mean better performance compared to non-salt forming systems, and salt formation is also not a prerequisite for the formation of promising drug-poly (amino acid) ASDs.

Synthesis of polystyrene derivative‐silica hybrids via in situ thiol‐ene reaction in the sol–gel process

AbstractPolystyrene derivative‐silica hybrids are synthesized via an in situ thiol‐ene reaction in the sol–gel process. Poly(p‐(3‐butenyl)styrene) (PBSt) which is a polymer having vinyl groups in its repeating units is used as an organic polymer and 3‐mercaptopropyltriethoxysilane (MPTES) is used as a photo‐induced crosslinking agent between the organic polymer and the silica matrix. MPTES is introduced to PBSt via a thiol‐ene reaction by the UV irradiation. Simultaneously, an acid catalyzed sol–gel reaction of tetraethoxysilane (TEOS) proceeds. The obtained hybrids having the organic polymer content of 30%, 50%, and 70% are optically transparent. On the other hand, the hybrids synthesized without the UV irradiation are turbid or translucent. The SEM–EDX analyses of the transparent hybrids show the homogeneity of the polymer and the silica in the hybrids. These results indicate that forming covalent bonds between PBSt and silica matrix through MPTES by the UV‐promoted thiol‐ene reaction improves the homogeneity of the hybrids. The thermal analyses of the hybrids using TGA show the silica components are almost quantitatively introduced into the resulting hybrids. The DSC measurements show that the resulting hybrids have higher Tg than the original organic polymer.

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.

Facile synthesis of intrinsically flame‐retardant epoxy thermosets with high mechanical properties from lignin derivatives

AbstractPreparing bio‐based epoxy resins with high performance is crucial to sustainable development. However, seeking renewable and flame‐retardant epoxy resins with high mechanical properties are still challenging. Here, we reported a facile way to transform lignin derivatives to intrinsic flame‐retardant epoxy resins with satisfactory mechanical properties. Two guaiacol‐based novolac epoxy resins (i.e., GTEP/DDM and GPEP/DDM) were prepared as alternatives for petroleum‐based DGEBA/DDM. The cured GTEP/DDM product showed a high Tg of 209.5°C, a high tensile modulus of 3.13 GPa, and a high LOI of 28.6% with UL‐94 V‐1 rating, which outperformed DGEBA/DDM system. Specially, GPEP/DDM resin possessed more superior mechanical properties (e.g., tensile strength of 73.9 MPa, and tensile modulus of 5.85 GPa) owing to additional interactions (i.e., π–π interactions and hydrogen bonds), and outstanding anti‐flammability (e.g., LOI of 31.2% with UL‐94 V‐0 rating) due to the endow of phosphorus‐containing groups. The mechanical reinforcement and flame‐retardant mechanisms were clarified based on structural evolution and performance variation. This work provides an efficient synthesis route to achieve a high‐performance thermoset, which is a promising alternative for substituting conventional bisphenol‐A epoxy resin for use as fireproof materials.

Liquid crystalline polybenzoxazines for manufacturing of technical textiles: Water repellency and ultraviolet shielding

Herein, the presented approach was investigated a unique technique for manufacturing water repellent/UV-protective cotton fabrics through in-situ/thermal polymerization of benzoxazine (BZs) within cotton matrix. Two BZs abbreviated as Ph-p-BZ and Ph-o-BZ were initially synthesized, and their chemical formulas were verified with FTIR, 1HNMR, and 13CNMR spectral mapping data. For Ph-p-BZ, the endothermic peak was observed at 65 ᵒC, to indicate its highly/purified crystalline structure. DSC data for poly-(Ph-p-BZ) and poly-(Ph-o-BZ) showed that, their high Tg was estimated at 210 ᵒC and 195 ᵒC, respectively, due to their highly crystalline/cross-linked network structure. In-situ/thermal polymerization of Ph-p-BZ and Ph-o-BZ as within cotton matrix was subsequently proceeded. Contact angle was observably increased to 125.0° for the fabric coated with four layers of poly-(Ph-p-BZ) (cotton modified with four layers of poly-(Ph-o-BZ); 120.3°). Wetting of water droplets was not significantly observed even after 8 min. Ultraviolet protection factor (UPF) was significantly increased from 1.4 for untreated cotton to 37.9 and 48.2 after modification of cotton with 4-layers of poly-(Ph-o-BZ) and poly-(Ph-p-BZ) polymers, respectively. Eventually, poly-benzoxazines derivatives could be applicable for manufacturing of water repellent/UV-protective fabrics that might be beneficial for military clothes.

D−π−A Strategy to boost dielectric breakdown strength of polyimide insulation

Polyimide (PI) possesses multiple advantages including excellent thermal stability, mechanical property and chemical resistance, which has been considered as one of the promising candidates for high-performance electrical insulation materials. Optimizing the polymer structure such as extending the band gap can yield high intrinsic breakdown strength, attributed to the inhibition of impact ionization. However, in most cases, large band gap is achieved at the cost of reducing the backbone coplanarity and rigidity or the intermolecular interaction, resulting in undesirable thermal and mechanical performance. Herein, we introduce an effective strategy to produce thermally stable and mechanically strong polyimide insulation with high breakdown strength through introducing aromatic donor groups into the main chains to construct a D−π−A structure. On the one hand, the formation of D−A effect increases the materials polarization and enhances dipole-induced scattering. On the other hand, enhanced intermolecular interaction via π−π stacking decreases free volume in PIs. Then, increased conjugation degree of the backbone and high packing density between the polymer chains benefit to thermal stability and mechanical properties. Based on this strategy, N-arkyl carbazole groups are preferred, in which the soft alkyl side groups can occupy the pores between the polymer chains to further decrease free volume. As a result, we afford polyimide insulation with significantly improved breakdown strength from 291 kV mm−1 to 570−632 kV mm−1, as compared to the reference PI ODA-PMDA. Simultaneously, the resultant PIs, such as PI-Bu, preserve high Td5% above 524 ℃, high Tg above 364 ℃ and tensile strength above 80 MPa.

New insights into contribution of aromatic ring versus aliphatic ring to thermal transition temperatures of heat resistant polyamides: A comparison study of PA 10T and t-PA 10C

In order to understand the differences in the contribution of aromatic (p-phenylene) ring versus aliphatic (trans-1,4-cyclohexylene) ring to the thermal transition temperature of heat-resistant polyamides, a comparison study is both experimentally and computationally implemented on a typical aromatic-heat-resistant polyamide PA 10T containing p-phenylene moieties and a typical alicyclic-heat-resistant polyamide t-PA 10C containing trans-1,4-cyclohexylene moieties. DSC, WAXD, solid state-NMR, computational simulations, and in-situ FTIR were utilized in sequence to reveal the differences in thermal performance, crystal structure, chain conformation, cohesive energy, interchain interaction, and melting process of PA 10T and t-PA 10C. t-PA 10C displays 30 °C-higher Tm and 50 °C-higher Tg than PA 10T. As indicated by the hydrogen bonding dissociation process, the enthalpy change dominates the difference in Tm as the gap in the entropy change between PA 10T and t-PA 10C is negligible. Computational simulation indicates that the energy-favorable hydrogen bonding conformation and dense trans-1,4-cyclohexylene-associated chain packing endow the formation of stronger interchain interactions in t-PA 10C which results in larger cohesive energy and greater cohesive energy density. The higher melting enthalpy change in the melting process derived from in-situ FT-IR experiment also verifies the simulated energy results. Henceforth, the question that WHY can the building block change, from rigid planar aromatic unit (PA 10T) to conformation-switchable nonplanar aliphatic unit (t-PA 10C), in the two polyamides induce so large improvement in Tg and Tm is systematically answered.

Trajectories of 24-Hour Physical Activity Distribution and Relationship with Dyslipidemia.

The association between physical activity (PA) and dyslipidemia is well known, but the relationship between a temporal pattern of PA and dyslipidemia remain unknown. Here, we aimed to identify the intensity and temporal patterns of PA clustered by the trajectory model and their relationship with dyslipidemia. The participants were 701 adults (305 males) aged 18−60 years undergoing continuous measurement of PA with Actigraph GT3X+ accelerometers for at least 3 days. A trajectory analysis was applied based on moderate-to-vigorous intensity physical activity (MVPA) accumulated values over every period per day. The association between PA and dyslipidemia was estimated using a logistic regression model. Four distinct PA trajectory groups in the population were identified (continued low, stable and moderate, late increasing, and early increasing). Specifically, the “moderate and stable group” was associated with a decreased rate of high TG (p < 0.05) and the “moderate and stable group” and “late increasing group” were associated with decreased rates of low HDL-C (p < 0.05). In conclusion, there were four activity trajectory groups in this population and the continued low PA trajectory was associated with a high prevalent rate of an abnormal lipid profile, and continued and moderate activity or late afternoon increasing activity might have lower HDL-C distribution.

Enhanced energy storage performance of polyetherimide-based sandwich-structured dielectric films in elevated temperature range via using cyanoethyl cellulose layer

In order to satisfy the application of electronic device in the harsh environment, polymer-based dielectrics should have high discharge energy density (Ud) and high-temperature resistance synchronously. Herein, a series of sandwich-structured polymer films consisting of cyanoethyl cellulose (CEC) and polyetherimide (PEI) were fabricated by the solution casting method. The PEI-based sandwich-structured dielectric films showed high dielectric constant because of highly polarized CEC layer and the macroscopical interfacial polarization. In addition, the polymer films displayed the improved breakdown strength owning to the insulating PEI, barrier effect of the interface, and electric field redistribution. As a result, the maximal Ud of a positive sandwich-structured P–5C–P film with outer PEI layer and central CEC layer reached 6.8 J/cm3 (151% of pure PEI) along with charge-discharge efficiency of 80%. More importantly, at 100 °C and 150 °C, a high Ud of 5.5 J/cm3 and 3.0 J/cm3 were achieved in the P–5C–P film due to both high glass transition temperature (Tg) of PEI and CEC, which was 1.72 times and 1.36 times than that of pristine PEI, respectively. This work provides a new method for the preparation of high-performance sandwich-structured polymer dielectrics via selecting highly polarized central polymer layer with high Tg.