Polyacrylonitrile Layer Research Articles

Forward osmosis zwitterionic membranes for platelet concentration – Evaluation of the feasibility of the concept

This study focuses on the development of forward osmosis (FO) membranes tailored for platelet and growth factor enrichment applications while maintaining minimal activation throughout the process. The FO membrane structure comprises a polyacrylonitrile (PAN) layer, fabricated using vapor-induced phase separation (VIPS), atop a polyethylene terephthalate (PET) substrate. Then, a polyamide (PA) layer was formed through interfacial polymerization (IP) at the PAN layer interface. The PET side of the membrane was further enhanced with coatings of antifouling copolymers, based on poly(ethylene glycol) methyl ether methacrylate (PEGMA) alone or both PEGMA and zwitterionic sulfobetaine methacrylate (SBMA). In a first step, the formation of each layer was optimized. The structure of the PAN layer was adjusted through the polymer concentration (15 wt%) and the exposure time to vapors (15 min) during the VIPS step. The PA layer was optimized by adjusting the curing temperature to 70 °C. The antifouling copolymer was selected by conducting protein adsorption tests. Subsequently, these tailored FO membranes were employed in the enrichment of plasma proteins, growth factors, and platelets from platelet-rich plasma. It is shown that the membrane modified with a copolymer made of butyl methacrylate (BMA), PEGMA and SBMA, referred to as poly(BMA-r-PEGMA-r-SBMA), enabled to reach a Human Serum Albumin concentration factor of 1.32 and a platelet concentration using PRP of 2.4. Despite partial platelet activation (12 %) due to the high cell concentration, the platelet content is much higher than in PRP or whole blood, which could benefit platelet-based therapies. In addition, the system can be applied to the concentration of growth factors, with PDGF and VEGF concentration factors of 1.92 and 2.58, respectively, which could contribute to the advancement of regenerative medicine.

Effect of heat treatment on the radial structure of coaxial polyacrylonitrile/mesophase pitch composite fiber

AbstractCoaxial composite fibers with a cortex of polyacrylonitrile (PAN) and a core layer of mesophase pitch (MP) and PAN were prepared by wet spinning, then heat‐treated in air. The effects of heat treatment on the thermal reaction characteristics, pre‐oxidation degree, radial structure, and thermal stability of coaxial composite fibers were studied by differential scanning calorometry, Raman, and thermogravimetric analysis. As the heat treatment temperature increases, the coaxial composite fibers only undergo cyclization without oxidation, the peak temperature of the thermal reaction increases from 258 to 270°C, and the enthalpy increases from 19.66 to 237.82 J g−1, the heat mainly arises from the PAN component. The Dr value of the coaxial fiber skin layer increases from 0.193 to 0.255 (330°C) and then decreases to 0.236; the core layer Dr value increases from 0.353 to 0.392 (310°C) and then decreases to 0.368. The pre‐oxidation reaction leads to an increase in sp2‐hybridized carbons and an increase in pre‐oxidation degree. When the heat treatment temperature <310°C, the pre‐oxidation degree of the composite fibers increases, leading to formation of a more stable structure compared with that at lower temperatures and an increase in the carbon residue rate.

Effect of mesophase pitch/polyacrylonitrile mixture as the core‐layer on the interphase region structure of coaxial polyacrylonitrile/mesophase pitch composite fibers

AbstractCoaxial composite fibers with a cortex of polyacrylonitrile (PAN) and a core layer of mesophase pitch (MP) and PAN have been prepared by the wet spinning method, formed in a mixed solution of N,N‐dimethylformamide and deionized water to optimize the composition of the core‐layer mixture. The XRD curves of the PAN/MP coaxial composite fibers only showed the crystalline and amorphous diffraction peaks of PAN. With increasing MP mass fraction in the mixed PAN/MP solution, the crystallinity of the coaxial composite fiber gradually decreased from 27.95% to 26.21%, because MP intermixed between the PAN macromolecules, weakening the interaction between the PAN molecular chains. In the core layer of the coaxial composite fibers, spherical MP particles were dispersed in the network structure of PAN. Different proportions of PAN/MP mixed solution will result in different core structure. The coaxial composite fiber consisted of a core layer with a low gray value, a transition layer with increasing gray value, and a cortex with a high gray value. From the core layer to the cortex, taking Group C as an example, the C content gradually decreased from 68.64% to 61.23% and the N content gradually increased from 13.68% to 22.19%, which was consistent with the gradual decrease of the MP content and the gradual increase of the PAN content. Gray‐value analysis, micro‐region EDS, and SEM showed that a transition layer structure formed at the junction of the cortex and core layer. The size and amplitude of the transition layer were related to the viscosity of the mixed PAN/MP solution, and high MP content in the mixed PAN/MP solution was conducive to formation of a stable and good interface structure.

Extended Lifespan of Low-Cost Metal Silicon Anodes via a One-Step Wet Ball-Milling Process for Ultra-Thin Polymer Protecting Layer and Optimal Particle Size

Silicon is a promising active material for lithium-ion batteries (LIBs) with a high theoretical capacity (∼4000 mA h g–1). However, there is a critical issue that the fabrication of the Si anode needs complicated and high-cost processes to alleviate the poor cyclic performance, such as nanostructuring. Furthermore, the Si anode requires a high component ratio of conductive agents and binder in the electrode. Herein, we report the fabrication of submicron Si particles coated by a polyacrylonitrile (PAN) layer with a highly polar nitrile group via a facile one-step wet ball-milling process. During the milling of Si particles in PAN solutions, PAN adheres to the Si surface and forms a nanometer coating layer. The nitrile groups of PAN enhance the electrolyte wettability and increase the lithium-ion pathways on the Si surface. These result in a stable solid electrolyte interphase (SEI) layer and reduce the internal resistance of the electrodes. Si anodes with an optimal particle size and PAN layer (SM-Si@PAN) exhibit a superior performance even at ultra-fast current density (50 A g–1). In addition, a full-cell with an NCM712 cathode shows an excellent performance.

Composite membranes with multifunctionalities for processing textile wastewater: Simultaneous oil/water separation and dye adsorption/degradation

In this work, we report on a novel membrane design with both photocatalysis and electrocatalysis for simultaneous oil/water separation and dye adsorption/degradation to treat oily wastewater from textile dyeing and finishing. The membrane (designated as PAN-CF/MWCNT/FeOOH) comprised a cotton fabric (CF) dopped with carbon nanotubes (MWCNT) and FeOOH and a microporous polyacrylonitrile (PAN) top layer. Under a flow-through dynamic filtration mode, the membrane allowed for separation of oil-in-water emulsions by the PAN layer via wettability sieving and coalescence demulsification, while hydrosoluble dyes were captured and degraded by the CF/MWCNT/FeOOH via adsorption and in situ electro-degradation. The kinetics of adsorptive capture and electro-induced degradation of hydrosoluble dyes on the PAN-CF/MWCNT/FeOOH membrane was determined, which confirmed that the flux decline during flow-through filtration caused by the accumulated foulant in the membrane was alleviated effectively. A flow-through filtration test with methylene blue (MB) dyed petroleum ether-in-water emulsion showed that a high removal rate of oil (99.9 %) and dyes (97.6 %) was achieved simultaneously in a single pass at a high water permeability (17.2 m3/m2.h.bar) under an operating pressure of 6.5 kPa and a DC current of 10 mA. In addition, the fouled membrane could be cleaned easily via photo-Fenton degradation under light irradiation. This novel approach to the design and fabrication of membranes with multifunctionalities is expected to offer numerous advantages for treating complex oily wastewater from textile processing.

Electroactive membrane with the electroactive layer beneath the separation layer to eliminate the interference of humic acid in the oxidation of antibiotics

Removing harmful antibiotics is essential to reclaiming water from municipal secondary effluent. Electroactive membranes are effective in the removal of antibiotics but challenged by the abundant coexisting macromolecular organic pollutants in municipal secondary effluent. To eliminate the interference of macromolecular organic pollutants in the removal of antibiotics, we propose a novel electroactive membrane with a top polyacrylonitrile (PAN) ultrafiltration layer and a bottom electroactive layer composed of carbon nanotubes (CNTs) and polyaniline (PANi). When filtering the mixture of tetracycline (TC, a typical antibiotic) and humic acid (HA, a typical macromolecular organic pollutant), the PAN-CNT/PANi membrane performed sequential removal. It retained HA at the PAN layer (by ∼96%) and allowed TC to reach the electroactive layer where it was electrochemically oxidized (e.g., by ∼92% at 1.5 V). The TC removal of the PAN-CNT/PANi membrane was marginally affected by HA, unlike that of the control membrane with the electroactive layer on the top that showed decreased TC removal after the addition of HA (e.g., decreased by 13.2% at 1 V). The decreased TC removal of the control membrane was attributed to the attachment (but not competitive oxidation) of HA on the electroactive layer that impaired the electrochemical reactivity. The HA removal prior to TC degradation realized by the PAN-CNT/PANi membrane avoided the attachment of HA and guaranteed TC removal on the electroactive layer. Long-term filtration for 9 h revealed the stability of the PAN-CNT/PANi membrane, and its advantageous structural design was conformed in the context of real secondary effluents.

Moisture wicking textiles with hydrophilic oriented polyacrylonitrile layer: Enabling ultrafast directional water transport

Functional textiles with high-performance directional water transport for regulating human sweat are in high demand because of growing concerns about the role of comfort in the performance of wearer. However, the fabrication of such materials remains a critical job. Here, we report a facile strategy to develop hydrophilic oriented polyacrylonitrile (HOPAN)/hydrophilic polylactic acid @polyvinylidene fluoride (HPLA@PVDF) composite membrane with surface energy gradient for enhanced directional water transport. Three step fabrication strategy involves electrospinning of oriented polyacrylonitrile (OPAN fibers) on polylactic acid (PLA) nonwoven surface followed by dip-coating in hydrophilic agent, and single-side electrospray of PVDF dilute solution on HOPAN/HPLA. Combination of highly oriented fiber structure, differential pore size and asymmetric wettability between two layers enabled instant water transport. The resultant fabricated composite membranes offer superior properties with one-way transport capacity (R) of 1117%, overall moisture management capacity (OMMC) of 0.91, and excellent water vapor transmission rate of 11.6 kg m−2 d-1. The successful preparation of these fascinating directional water transport materials offers new insight into the role of fiber alignment along with differential apertures and asymmetric chemical structure for realizing membranes for quick-drying applications.

Electrospun-nanofibrous Redox-active separator for enhancing the capacity of Lithium-ion batteries

Separator is a key component of lithium-ion battery (LIB), and a redox-active separator can enhance the capacity of LIB by participating in battery reactions. This paper reports a redox-active separator based on Fe(CN)64- doped polypyrrole (PPy) composite nanofibers fabricated by electrospinning and in-situ polymerization. The separator is composed of one layer of Polyacrylonitrile (PAN)@doped-PPy core–shell structured nanofibers and another layer of PAN nanofibers. The porosity, electrolyte uptake, and ionic conductivity of the optimized redox-active separator are 79.3 ± 7.1%, 294.6 ± 31.5%, and 1.57 ± 0.06 mS∙cm−1, respectively. These values are greater than those of a commercial PP separator, 41%, 81.5 ± 17.4%, and 0.75 ± 0.02 mS∙cm−1, respectively. Accordingly, the discharge capacity of the battery cell with the redox-active separator is up to 158.7–227.0 mAh∙g−1 at the current rates of 2.0–0.2C, outperforming conventional inert separators. The enhanced battery capacity is stemmed from the redox activity of the doped-PPy polymer, as evidenced by the wider cathodic and anodic peaks in the cyclic voltammetry. In addition, the battery cells tested with redox-active separators show gravimetric energy densities of up to 103.0 mAh∙g−1, which is 56.1% and 27.2% greater than those of a commercial PP separator and the redox-active separator reported in the literature.

A dendrite-free anode for stable aqueous rechargeable zinc-ion batteries

Due to its low cost, high specific co, and environmental friendliness, zinc is considered a potential anode material for aqueous rechargeable Zn-ion batteries. However, practical applications remain a challenge due to uncontrolled dendrite formation. Herein, we have utilized a strategy where a microporous nanofiber layer of polyacrylonitrile (PAN) is electrospun onto Cu foil and used as the current collector for the anode to inhibit dendrite generation. The polar nitrile groups on the nanofibers expedite the uniform transport of Zn2+ and allow homogenous Zn deposition, which ultimately inhibits dendrite growth. The symmetrical cell equipped with this new fabricated electrode shows over 270 stable cycles without a short circuit. The full cell formed with MnO2 as the cathode exhibits improved cycle stability up to 300 cycles at a current density of 0.5 A g−1.

Expandable crosslinked polymer coatings on silicon nanoparticle anode toward high-rate and long-cycle-life lithium-ion battery

Porous and electrically conductive coating on silicon nanoparticles (Si NPs) anode can mitigate the volume expansion during charging or discharging in Li-ion battery (LIB) while conventional protection coating process resulted in non-uniform polymer shell which show low volumetric or areal capacities. Here, we demonstrated that ultra-thin polyacrylonitrile layer can be formed conformally by emulsion-assisted coating process and cross-linked on Si NPs (Si@x-PAN) producing stable and expandable polymer shell which showed a highly stable long-term cycling ability. Areal and specific capacities of Si@x-PAN were an ∼ 2 mAh/cm2 and a 2000 mAh/g, respectively. Importantly, we found that capacity decay was only 5 % after 100 cycles and>75 % of capacity was retained even after 1000 cycles (0.5C/0.5C) with the help of a uniform Li-ion current around the Si NPs during continuous charging and discharging. To our knowledge, this long-term stability at reasonable loading levels is one of the highest levels of performance in pure Si anode systems.

A high-flux polystyrene-reinforced styrene-acrylonitrile/polyacrylonitrile nanofibrous membrane for desalination using direct contact membrane distillation

High-flux composite MD membranes were fabricated using high-productive electroblowing and air-assisted electrospraying processes. Top layer thickness of dual-layer nanofibrous styrene-acrylonitrile (SAN)/polyacrylonitrile (PAN) membrane was designed to be as small as possible to balance the mass and heat transfer resistance to gain better permeability. In this regard, the nanofibrous PAN layer was firstly fabricated by the electroblowing process as the support layer for the SAN nanofibers. Mechanical strength and wetting resistance were improved considerably After the hot-pressing operation. Upon fabricating polystyrene (PS) microbeads on the hot-pressed SAN/PAN membrane, a superhydrophobic surface with a water contact angle (WCA) of 155.9° was formed. The single-layer SAN, dual-layer SAN/PAN, and the PS-reinforced membranes (PS/SAN/PAN) were then used for 35 g/L feed water desalination by direct contact membrane distillation (DCMD). The permeate flux (37.16–84.4 kg/m2 h) of the fabricated membranes was higher than the commercial polytetrafluoroethylene (PTFE) membrane and high salt rejection of 99.9% was measured for all of the tested membranes. Our proposed composite membranes can significantly impede the pore wetting problem and low permeation as the most pronounced challenges of the membrane distillation (MD) process.

In situ photo-thermal conversion nanofiber membrane consisting of hydrophilic PAN layer and hydrophobic PVDF-ATO layer for improving solar-thermal membrane distillation

Solar thermal membrane distillation is a promising technology for low-cost desalination and water purification. A novel photo-thermal conversion membrane composited by polyacrylonitrile (PAN) nanofiber layer and polyvinylidene fluoride (PVDF) with antimony tin oxide (ATO) as solar-thermal nanoparticles (PVDF-ATO/PAN nanofiber membrane) was fabricated by sequent electrospinning techniques. The dual-layer membrane with hydrophilic PAN and hydrophobic PVDF-ATO was examined by microscopic evaluation and contact angle measurement. In situ temperature increase on membrane superficial layer (PVDF-ATO) driven by solar light illumination was confirmed by thermal imaging system. PAN layer provides water transport channels for facilitating water flow of highly efficient membrane distillation and avoids the salting assembly during the vigorous evaporation. With the help of hydrophilic PAN layer, our PVDF-ATO/PAN nanofiber membrane can fulfill highly effective localized heating transfer with an evaporate rate of 0.93 kg m−2 h−1, showing great potential for low-cost water desalination and scalable water purification.

Effects of annealing temperature on electrochemical performance of SnSx embedded in hierarchical porous carbon with N-carbon coating by in-situ structural phase transformation as anodes for lithium ion batteries

Tuned tin chalcogenides rooted in hierarchical porous carbon (HPC) with N-carbon coating layers are prepared by thermal shock under various temperatures (denoted as HPC-SnS2-PAN-Various T). With the increase of annealing temperature, the morphology and phase structure of SnS2, as well as the cyclization degree of polyacrylonitrile (PAN), are significantly changed, which leads to the formation of rod-like SnS and ordered structure of conductive N-carbon layer. By combining HPC, N-carbon coating derived from the cyclization of PAN, with 1D SnS nanorods generated from structural phase transformation of SnS2, the optimized composite (HPC-SnS2-PAN-500) as anode for lithium ion batteries (LIBs) provides buffer space for volume changes during alloying/dealloying process, builds a highly conductive network as well as decreases irreversible capacity from solid electrolyte interphase and enhances the ion/electron transport. Attributed to the above merits from composition regulation and architecture modification by sulfur depletion and PAN cyclization, this target anode exhibits an extraordinary cycling stability with a high specific capacity of 652.5 mA h/g at 0.5 A/g after 900 cycles. It suggests that rod-like SnS embedded in HPC with cyclized PAN layers by thermal treatment approach renders a potential structural design of anode materials for LIBs.

A Wearable, Bending-Insensitive Respiration Sensor Using Highly Oriented Carbon Nanotube Film

Recently, wearable electronics for health monitoring have been demonstrated with considerable benefits for early-stage disease detection. This article reports a flexible, bending-insensitive, bio-compatible and lightweight respiration sensor. The sensor consists of highly oriented carbon nanotube (HO-CNT) films embedded between electro-spun polyacrylonitrile (PAN) layers. By aligning carbon nanotubes between the PAN layers, the sensor exhibits a high sensitivity towards airflow (340 mV/(m/s)) and excellent flexibility and robustness. In addition, the HO-CNT sensor is insensitive to mechanical bending, making it suitable for wearable applications. We successfully demonstrated the attachment of the sensor to the human philtrum for real-time monitoring of the respiration quality. These results indicate the potential of HO-CNT flow sensor for ubiquitous personal health care applications.

Eco-facile application of electrospun nanofibers to the oil-water emulsion separation via coalescing filtration in pilot- scale and beyond

In the present environmental study, different polymer nanofibers as coalescing filters and the effect of their type on the separation of secondary oil emulsion from oily wastewater were investigated in a semi-industrial scale. Polystyrene (PS), polyacrylonitrile (PAN), and polyamid6 (PA6) were used to be electrospun on the polyester (PET) nonwoven substrates. These nanofibers were fabricated in various spinning times. Filtration variables were examined and a system was designed. By adding the nanofiber layer to the nonwoven substrate, pressure drop and coalescing filter efficiency increased in all samples. The separation efficiency for three nanofibrous coalescing filters in 20 min electrospinning of different polymers at the same condition on polyester nonwoven as substrate such as two nonwoven layers of PET and one layer of PAN, two nonwoven layers of PET, and one layer of PA6, two nonwoven layers of PET and one layer of PS were 89.3 %, 83.3 % and 69.8 % respectively. This value was 60.6 % for the blank sample (nonwoven polyester). Hence, the mixture of two nonwoven layers of PET and one layer of PAN was selected as the suitable filter. Using the suitable coalescing filter COD decreased significantly. It diminished the potential risks related to oil discharge to the environment.

Electrospun Bilayer PAN/Chitosan Nanofiber Membranes Incorporated with Metal Oxide Nanoparticles for Heavy Metal Ion Adsorption

Bilayer nanofiber membranes with enhanced adsorption and mechanical properties were produced by combining a layer of polyacrylonitrile (PAN) functionalized with metal oxides (MO) of ZnO or TiO2 with a layer of chitosan (CS) via consecutive electrospinning. The adsorption properties of the bilayer PAN/MO–CS nanofiber membranes against lead (Pb(II)) and cadmium (Cd(II)) ions were investigated, including the effects of the solution pH, initial ion concentrations, and interaction time. The integration of a CS layer into PAN/MO nanofibers increased the adsorption capacity of lead by 102% and cadmium by 405%, compared to PAN/MO single layer. The nonlinear optimization method showed that the pseudo-second-order kinetic model and Langmuir isotherm equation better described the adsorption results. More importantly, the incorporation of a supportive CS nanofiber layer enhanced the tensile strength of PAN/MO–CS bilayer by approximately 68% compared to the PAN/MO single layer, owing to the strong interaction between the fibers at the interface of the two layers.

High tough and highly porous graphene/carbon nanotubes hybrid beads enhanced by carbonized polyacrylonitrile for efficient dyes adsorption

Abstract Dyes pollution poses severe threat to ecological system and presents a great challenge for global sustainability. High efficient adsorbent for dyes pollution is urgently demanded. Herein, highly porous graphene/carbon nanotubes hybrid beads (HPGCB) with strong mechanical stability are developed as high efficient adsorbent, in which the synthesis involves three steps: (1) emulsifying and self-assembling the graphene/carbon nanotubes into spherical hydrogel, (2) coating of polyacrylonitrile (PAN) and (3) KOH activated carbonization. As for the proposed strategy, while the carbonized PAN layer strengthens effectively the mechanical stability and cyclic resilient property of HPGCB, the KOH activation creates lots of nanopores (0.8–2 nm) on graphene network and offers large specific surface area (1270 m2/g). By adsorption evaluation, HPGCB reaches maximum adsorption capacity of 521.5 mg/mL for methylene blue (MB), which is superior to other similar adsorbents. The adsorption kinetics of MB on HPGCB is analyzed by both pseudo second-order and intra-particle diffusion models, which confirm its fast adsorption rate for dyes adsorption. Taken together these properties, the proposed HPGCB has great potential in the remediation of water pollution.

Artificial solid electrolyte interphase based on polyacrylonitrile for homogenous and dendrite-free deposition of lithium metal**Project supported by the National Natural Science Foundation of China (Grant Nos. 51822211 and 51802342) and the State Grid Technology Project, China (Grant No. DG71-17-010).

High chemical reactivity, large volume changes, and uncontrollable lithium dendrite growth have always been the key problems of lithium metal anodes. Coating has been demonstrated as an effective strategy to protect the lithium metal. In this work, the effects of polyacrylonitrile (PAN)-based coatings on electrodeposited lithium have been studied. Our results show that a PAN coating layer provides uniform and dendrite-free lithium deposition as well as better cycling performance with carbonate electrolyte. Notably, heat treatment of the PAN coating layer promotes the formation of larger deposit particle size and higher coulombic efficiency (85%). The compact coating layer of heat-treated PAN with a large Young modulus (82.7 GPa) may provide stable protection for the active lithium. Improved homogeneity of morphology and mechanical properties of heat-treated PAN contribute to the larger deposit particles. This work provides new feasibility to optimize the polymer coating through rational modification of polymers.

Membrane layers intensifying quorum quenching alginate cores and its potential for membrane biofouling control

Quorum quenching (QQ) has been proved to be an efficient method to mitigate biofouling in membrane bioreactors (MBRs). In this paper, in order to enhance practicability of QQ microcapsules, we prepared three types microcapsules with same alginate cores (SAs). The microcapsules with polyacrylonitrile (PAN) layer showed excellent performance in preventing cell leakage from the microcapsules, increasing service life and improving mechanical strength. And confocal laser scanning microscopy images demonstrated that there were very little dead bacteria in the microcapsules with both chitosan and PAN layer than microcapsules with only PAN layer because chitosan layer can protect bacteria entrapped in cores from the hurt caused by poisonous PAN solution. At the same time, the microcapsules with PAN layer presented more efficient anti-biofouling ability in the physical washing test. At last, the bacterial microcapsules coated with both chitosan and PAN layer showed an obvious biofouling mitigation during the MBRs operation.

The Effect of Nonwoven Electrospun PAN Nanofiber Mat on Mechanical and Thermal Properties of Epoxy Composites

In this study mechanical and thermal properties of epoxy resin reinforced with different numbers of nanofiber layers which produced with electrospinning method was investigated. Solution of 10 wt% of polyacrylonitrile (PAN) in N,N-dimethylformamide (DMF) was used for electrospinning. The diameters of the obtained nanofibers were in the range of 380-420 nm. The average thickness of the produced nanofiber layer was about 200 µm. The special molds were prepared to produce the laminated composite plates. The tensile tests show that the using of nanofiber PAN layers increase the tensile force 34.54% and decrease the elongation 8.87% in comparison with neat epoxy. The fracture surfaces of the specimens were inspected by using optical and scanning electron microscopy (SEM). The thermal properties of the nanofiber layered composites were determined by thermo gravimetric analysis (TGA) and differential scanning calorimetry (DSC) analysis. It was observed that the glass transition temperature increased parallel to this as the number of PAN layers increased and rose up to 86ᵒC, while the thermal stability did not show much effect of PAN layers.