Degree Of Cyclization Research Articles

Effect of temperature gradient on the chemical structure and physical morphology of polyacrylonitrile fibers during thermal stabilization process

The thermal stabilization process is a crucial stage for microstructure transformation and quality of carbon fibers, which is determined by the stabilization temperature gradient. In this work, the effect of the temperature gradient on the evolution of both chemical structures and physical morphology of polyacrylonitrile (PAN) fibers at multistage of thermal stabilization process was investigated. Combined with functional groups, oxygen element content, and aromatization index, increasing temperature reasonably shifted oxidation and cyclization reaction into early stage and the corresponding samples possessed relatively large degree of cyclization. It was worth noting that high stabilization temperature gradient could accelerate the formation of the conjugated structures at early stage and facilitate the cyclization reaction in the stabilized fibers. As for morphologies, there were aligned microfibrils and transvers lamellae in stabilized fibers. Their radial structure difference increased firstly and then decreased in the later stage. The tensile strength and tensile modulus decreased during the thermal stabilization process. Moreover, increasing temperature resulted in reduction of tensile strength and tensile modulus, which was mainly resulted by the high degree of cyclization instead of structural defects. These results guide the design and optimization of temperature program and adjusting the processing parameters for all commercially PAN fibers without any additional conditions.

Effect of cyclization degree of nitrogen thermal pretreatment on radial structure of PAN stabilized fibers

Effect of cyclization degree of nitrogen thermal pretreatment on radial structure of <scp>PAN</scp> stabilized fibers

The global distribution of Isoprenoidal Glycerol Dialkyl Diethers (isoGDDs) is consistent with a predominant degradation origin

Glycerol dialkyl diethers (GDDs) are membrane lipids and a variation of the more commonly known glycerol dialkyl glycerol tetraethers (GDGTs). GDGTs include both archaeal and bacterial membrane lipids that are both frequently used for paleoclimate reconstruction in a range of terrestrial and aquatic environments. In contrast to GDGTs, GDDs lack one of the terminal glycerol moieties. Although both isoprenoidal (iso) and branched (br) GDDs have been found, this study focuses on isoGDDs. These lipids have been found in a few terrestrial and aquatic environments. However, the origin of isoGDDs is debated and the extent of their distribution across the surface of the Earth is poorly constrained. Based on a few single site studies, previous authors hypothesised that isoGDDs are degradation products of isoGDGTs, but more recent studies that isolated isoGDDs from cultured nitrososphaerota (formerly thaumarchaeota) proposed a biological source through direct archaeal biosynthesis. Here we compiled a global dataset of isoGDD and isoGDGT abundance in environmental samples to thoroughly investigate the distribution of isoGDDs and the correlation with isoGDGTs on a global scale and across a variety of environments (peat, mineral soils, lake sediments, and marine sediments). We find that isoGDDs are present in most samples that we analysed. Their abundance is strongly proportional to isoGDGT abundance (r2 = 0.85), dominated by the GDGT-crenarchaeol/GDD-crenarchaeol ratio (r2 = 0.94) and supported by individual compound isoGDGT/isoGDD ratios (r2 = 0.56–0.94). In addition, the degree of cyclisation of isoGDDs, reflected in the ring index, is positively correlated (r2 = 0.84) with that of isoGDGTs across all environments. We conclude that isoGDDs are abundant on the surface of the Earth and predominantly originate from the degradation of isoGDGTs.

Understanding the behaviors of ZIF-67 reinforced electrospun carbon nanofibers in the preparation and stabilization

MOFs-reinforced electrospun carbon nanofibers offer a wide range of applications in the field of energy storage. In this study, ZIF-67 nanoparticles were produced and combined with polyacrylonitrile for electrospinning before being stabilized and carbonized to form a carbon nanofiber. BET, FT-IR, EA, DSC, and other techniques were used to investigate the stabilizing behaviors of PAN electrospun fiber with varying ZIF-67 concentrations at different temperatures. Under the same stabilizing settings, it was discovered that PAN electrospun fiber containing ZIF-67 nanoparticles could absorb more oxygen, promoting a higher degree of cyclization and crosslinking. Therefore, it was preferred to prepare carbon nanofibers at a lower stabilization temperature. Importantly, the degree of stability and disorder of the PAN/ZIF-67 stabilized fiber has been described by the FT-IR and the Raman spectra. This research deepens understanding about the formation of MOF-reinforced carbon nanofibers and expands our knowledge of the stability of PAN/MOF hybrid fibers.

Glycerol dialkyl glycerol tetraethers in surficial marine sediments across shelf-to-basin depth transects in the East China Sea: Their sources and potential as sea water temperature proxies

To better understand the compositions and sources of glycerol dialkyl glycerol tetraethers (GDGTs) and their use as proxies in the East China Sea (ECS), we analysed GDGTs in surficial sediments from the ECS outer shelf, slope and Okinawa Trough (OT) in open marine settings between 126°E and 129°E at water depths of either <100 or > 1000 m. The GDGT-0/Cren. values (0.35 ± 0.04) and methane index (MI) (0.17 ± 0.02) were generally low, indicating a negligible contribution of methanogenic Euryarchaeota GDGTs to the open marine settings in the ECS and that isoprenoid GDGTs (isoGDGTs) were mainly derived from marine planktonic Thaumarchaeota. Comprehensive analysis of the degree of cyclisation (DC) (0.34–0.53), #ringstetra (0.53–0.94), and IIIa/IIa (0.54–3.24) indices indicated that branched GDGTs (brGDGTs) may be predominantly produced in situ, with minimal soil contribution in this setting. The TEXH86-derived sea surface temperatures (SST) were closer to the annual SST than the seasonal SST from the World Ocean Atlas (WOA) 2013. The methylation of the branched tetraethers (MBT) index correlated well with the mean annual bottom water temperature (BWT) from WOA 2013. Therefore, we propose that the MBT index from open marine settings in the ECS may reflect BWT changes in marine bottom environments.

Development of non-combustible weaveable yarn through oxidative control of a textile acrylic fibre

Acrylic fibre is considered to be artificial wool in the textile industry, but in contrast with natural wool, it vigorously burns producing black smoke and toxic gases. This not only has hindered its technical applications, but also poses safety risks to the end-users of acrylic-based products. This research aims at enhancing the fire-retardancy of acrylic yarns using a facile thermal stabilisation process which is based on controlling the oxidation temperature and residence period. To this end, acrylic yarns are thermally processed according to six different time and temperature profiles ranging from 220 to 280 °C, with residence periods ranging from 22 to 28 min. The oxidised yarns were characterised using FTIR, DSC, and TGA techniques and the effects of the oxidative thermal treatment on physical characterises, and surface morphology of yarns and fibres were discussed. The results showed that the acrylic yarn undergone the oxidation process based on 240–255–270–280 °C heating profile for 28 min at each step had a sufficiently high degree of cyclisation with an excellent fire retardancy. Furthermore, the stabilised acrylic yarn was strong enough to be woven into a plain weave fabric using a laboratory scale loom while displaying non-combustible behaviour during cyclic exposure to flame. These results present a novel pathway for the development of a low cost, non-combustible fabric ideally suited for applications in extreme environments.

Environmental controls on the distribution of GDGT molecules in Lake Höglwörth, Southern Germany

Tetraether lipids, such as glycerol dialkyl glycerol tetraethers (GDGTs), are an increasingly used proxy for reconstructing paleoclimatic and paleoenvironmental dynamics. On a global scale, environmental drivers controlling the distribution of GDGTs in lake systems have been described extensively. However, the drivers that control down-core sedimentary GDGT composition within single lake systems are still poorly constrained. Here, we analysed GDGTs in a sediment core collected from Lake Höglwörth (Bavaria, Germany) covering the last ∼1100 years. The increase in ratio ΣIIIa/ΣIIa values (a ratio which captures the variation of 3 structural isomers of penta- and hexamethylated brGDGTs respectively) reflects a higher contribution of branched (br) GDGTs from aquatic sources after 1800 CE. This is synchronous with a high nutrient input as a result of increased local anthropogenic activities. The climate proxy methylation of branched tetraethers (MBT'5ME) reveals a pattern that deviates from the anticipated temperature changes during the last millennium. Instead, high MBT'5ME values from ∼880 to 1120 CE coincide with a period of increased soil input, resulting from lake damming and/or construction of the Höglwörth monastery. Decreased values after 1800 CE until present date correspond to a higher contribution of aquatic brGDGTs, with changes in the dependency between Ia and IIa suggesting a direct influence of bacterial community changes on the MBT'5ME. The proxy cyclisation of branched tetraethers (CBT') shows a linear increase with time, and a stepwise increase at 1700 CE, when a creek stream inflow channel was rerouted. Over time, MBT’5ME decreases gradually, while CBT’ and ΣIIIa/ΣIIa increase. This is hypothesized to be potentially caused by decreasing water depth over time and/or post- or syn-sedimentary production of GDGTs. The degree of cyclization (DC') shows variations on shorter timescales, possibly driven by the lake mixing regime and water column redox conditions. Our results indicate that caution must be taken when interpreting GDGTs for paleoclimate and paleoenvironmental reconstruction considering the possible influence of shifts in the provenance of brGDGTs. Further studies focusing on both sedimentary and intact polar lipids are highly recommended to constrain the source (water column, or sedimentary production) of GDGTs in lake sediments.

Interpretable machine learning assisted multi-objective optimization design for small molecule hole transport materials

Small molecule hole transport materials (SM-HTMs) play an important role in the development of perovskite solar cells (PSCs) due to the simple structure and excellent photoelectric performance. Herein, we established interpretable models for designing materials with high hole mobility (μ) and absolute hardness (η). The μ and η models were constructed by Gradient Boosting Regression (GBR) due to the better performances. The coefficient of determination (R2) for leave-one-out cross validation (LOOCV) and the test set are 0.86 and 0.86 in μ model, 0.84 and 0.89 in η model, respectively. SHapley Additive exPlanations (SHAP) analysis reveals that higher μ are more likely to be obtained with fewer C–O and N-O pairs at topological distance 9, and molecules with high degree of cyclization and less polar fragments might have higher η. New groups were designed based on the strategies and used to generate 785 virtual samples. Finally, 35 promising candidates (μ > 10−1.54 cm2 V−1 s−1 and η > 2.71 eV) with high synthesizability were screened out using high-throughput screening and pattern recognition. Our work provides an effective way to accelerate the design of prominent SM-HTMs.

Impact of organic carbon reworking upon GDGT temperature proxies during the Paleocene-Eocene Thermal Maximum

Glycerol dialkyl glycerol tetraethers (GDGTs) have been widely applied to coastal marine sediments to reconstruct past temperature variability. However, coastal environments are characterised by variability in the source, age and/or thermal maturity of different organic carbon (OC) pools and may bias various GDGT-based proxies. Here we analyse TEX86 and MBT5MEvalues within a shallow marine sediment core (South Dover Bridge, Maryland) from the Paleocene-Eocene Thermal Maximum (PETM; 56 million years ago (Ma)) to explore how changes in OC reworking influence GDGT-derived sea surface and terrestrial temperature estimates, respectively. We demonstrate that TEX86 values are unaffected by an increase in soil- and fossil organic carbon during the PETM. In contrast, we find large and unexpected variations in MBT5ME-derived temperature estimates (∼6 to 25 °C) during the onset and core of the PETM at some sites. This coincides with input of reworked terrestrial OC from the Cenomanian-aged Raritan Formation. However, there is also an increase in the degree of cyclisation of tetramethylated branched GDGTs, suggesting that branched GDGTs are also derived from marine in-situ production. These factors preclude terrestrial temperature reconstructions at this site. We explored whether OC reworking is problematic in other PETM-aged coastal environments. Using GDGT metrics and the Branched and Isoprenoid GDGT Machine learning Classification algorithm (BIGMaC), we demonstrate that TEX86 values are mostly unaffected by changes in OC sources. However, MBT5ME values are affected by marine and/or freshwater overprints, especially in environments with low terrestrial OC input. Taken together, this study highlights the importance of constraining the provenance of different GDGTs in marine and lacustrine environments.

Macrocyclizing DNA-Linked Peptides via Three-Component Cyclization and Photoinduced Chemistry.

While DNA-encoded macrocyclic libraries have gained substantial attention and several hit compounds have been identified from DNA-encoded library technology, efficient on-DNA macrocyclic methods are also required to construct DNA-linked libraries with a high degree of cyclization and DNA integrity. In this paper, we reported a set of on-DNA methodologies, including the use of an OPA-mediated three-component cyclization with native handles of amino acids and photoredox chemistries. These chemistries proceed smoothly under mild conditions in good to excellent conversions, successfully generating novel isoindole, isoindoline, indazolone, and bicyclic scaffolds.

Dynamic covalent exchange in methacrylic anhydride copolymers

Methacrylic anhydride (MAA)-based copolymers were synthesized to probe how the molecular environment around the anhydride moieties impacts the ability of dynamic covalent exchange between anhydrides impacts the ability to recyclable the crosslinked (co)polymers. The comonomers methyl methacrylate (MMA) and n-butyl acrylate (BA) were copolymerized with MAA to yield crosslinked copolymers with varying compositions and their thermal and physical properties were studied as a function of the number of recycling events and copolymer composition. Dynamic covalent exchange was studied via recycling through repetitive grinding and compression molding at elevated temperatures and pressures (130 °C and 152 MPa for 2 h). It is concluded that adjacent anhydride moieties can undergo exchange to produce cyclic anhydrides, as observed through IR spectroscopy after heat treatments. Peak deconvolution was utilized to determine the degree of cyclization. Significant increases in monomer conversion occurred and anhydride cyclization was apparent during the first recycling process. Additional recycling processes continued to change the degree of cyclization, but the extent was dependent on the comonomer type. The degree of cyclization was found to be lower in the copolymers compared to the homopolymer, probably because the interruption of MAA units by the comonomer units along the backbone reduces the ability to cyclize. Thermal properties (glass transition temperature, Tg) of the polymers were also impacted, however the static material properties (modulus and hardness) did not exhibit any dependence on cyclization due to the immobile nature of the highly crosslinked network at room temperature.

Influence of acid concentration on thermomechanical, tensile and thermal properties of cyclized natural rubber

Properties of cyclized natural rubbers (NR) with various degrees of cyclization (∼4-22%) were investigated in this study. Prior to compounding with rubber additives, the cyclized rubbers were initially prepared by dropping various concentrations of acid (5-30 wt%) to the NR latex, followed by coagulation and drying. The results revealed that the degree of cyclization increased with acid concentration. Increased ring structure formation in the modified NR tended to increase the torque difference during crosslinking, as the cyclic ring structures acted as steric hindrances. The crosslink density was found to decrease with increasing cyclization level due to the loss of active sites for crosslink formation, increasing swelling capability of the cyclized rubbers. The 100% and 300% moduli, tensile strength and extensibility of the NR reduced with increasing degree of cyclization due to a reduction of crosslink density. As a result of cyclic structure formation and a reduction of unsaturated double bonds in the NR, the stability of cyclized NR at elevated temperatures was improved over the pure NR, in a manner dependent on the level of cyclization. Single glass transition temperature was seen in the NR while two glass transition temperatures were noticed in the cyclized NR. The thermal stability of 22% cyclized NR was 50°C higher than that of the pure NR and the aging properties of the cyclized NRs were also greater mainly due to a reduction of unsaturated double bonds. This suggests that cyclized NR may find applications in products requiring thermal resistance.

Study on the relationship between ring formation and properties of pre-oxidized polyacrylonitrile-based fibres

The relationship between the degree of ring formation and the overall properties of the pre-oxidized fibre was studied by treating PAN precursor with KClO3/H2SO4 solution and different pre-oxidation techniques. PFs are polar materials and the dielectric constant increases after solution treatment. The bulk density of Cl-MSFs is always higher than that of MSFs and CSFs in the same temperature zone. The bulk density of Cl-MSFs5 is 1.401 g/cm3, which is 1.6% higher than that of MSFs5. The EOR value of Cl-MSFs5 is 0.767, which is 11.97% higher than the value of MSFs5. The modified polyacrylonitrile precursor showed a high degree of cyclization during microwave heat treatment. The temperature can be reduced by about 40 °C by modifying and microwave heat treatment to achieve the same level of cyclization. Cl-MSFs5 has a higher O content than MSFs5. The microscopic morphology shows that the number of "grooves" and fibre diameter of Cl-MSFs5 is significantly smaller than that of MSFs5, indicating that it has a higher degree of stability. There is no Cl element on the surface of Cl-MSFs5, which indicates that the structure of the pre-oxidized fibre is not affected after the pre-oxidation treatment. In addition, the structural transformation of KClO3-modified PFs during microwave pre-oxidation is proposed. The cyclization reaction occurs first, followed by dehydrogenation and oxidation reactions. In the carbon fibre production process, the pre-oxidation stage takes a long time and consumes a lot of energy. The new composite treatment technology used in this study can effectively reduce the treatment temperature and shorten the treatment time in the pre-oxidation stage, which provides a reference for the development of low-cost and efficient pre-oxidation process.

Study on preparation of high cyclization degree and high strength pre-oxidized fiber by nitration

Study on preparation of high cyclization degree and high strength pre-oxidized fiber by nitration

Transformation of phosphorus species during phosphoric acid-assisted pyrolysis of lignocellulose

Phosphoric acid-assisted pyrolysis (PAAP) is a pyrolysis technique with potential for the engineered and environmental application. Nevertheless, the volatilisation, immobilisation, and dissolution of phosphorus (P) species have been neglected during PAAP of lignocellulose. Therefore, we compared the transformation of P species with direct-pyrolysis and PAAP system, using multiple techniques including gas chromatography tandem mass spectrometry (GCMS) and 31P nuclear magnetic resonance (NMR). It was also investigated that the properties of pyrogenic and modified carbons obtained from lignocellulose pyrolysis at 200–650 °C. As the temperature increased, volatile P species evolved into gas-phase during PAAP, inhibiting the formation of the macromolecular volatile components. Compared with pyrogenic carbons, modified carbons with more aromatic structures experienced a higher degree of dehydration and cyclisation via catalytic crosslinking reaction. PAAP system facilitated more generation of persistent free radical (PFR) below 500 °C and the attenuation of PFR signals was observed at 500–650 °C, which may be associated with the sequestration and elimination of P species between carbon matrix. Notably, three configurations of C3PO, CPO, and COP were the major combinations of P and C elements on modified carbons. Increased gaseous P and decreased soluble P were observed with elevated temperatures in PAAP system. The species proportion of immobilised P clearly demonstrated the transformation of partial P species from inorganic to organic through pyrolysis. The immobilised P could serve as a potential sustained-release source participating in P biogeochemical cycles. These findings are fundamental for the technical design of lignocellulose pyrolysis.

Utilization of CO2 in supercritical conditions for the synthesis of cyclic poly (N-isopropylacrylamide) via emulsion and homogeneous reactions

In this study, cyclic poly (N-isopropylacrylamide) (cPNIPAAM) was synthesized in supercritical carbon dioxide (SC-CO2) using emulsion and homogeneous reactions for the first time. This was accomplished by applying free radical polymerization and nitroxide compounds to produce low molecular weight precursors in the SC-CO2 solvent. The cyclization reaction occurred in a homogeneous phase in the SC-CO2 solvent, with dimethylformamide (DMF) serving as a co-solvent for dissolving the linear precursor. This reaction was also conducted in emulsion of SC-CO2 in water. The effects of pressure and time on the morphology, molecular weight, and yield of a difunctionalized chain were investigated, where a higher pressure led to a higher yield. The maximum yield was 64% at 23 MPa, and the chain molecular weight (Mw) was 4368 (gr/mol). Additionally, a lower pressure reduced the solubility of materials (particularly terminator) in SC-CO2 and resulted in a chain with a higher molecular weight 9326 (gr/mol), leading to a lower conversion. Furthermore, the effect of cyclization reaction types on the properties of cyclic polymers was investigated. In cyclic reactions, the addition of DMF as a co-solvent resulted in the formation of a polymer with a high viscosity average molecular weight (Mv) and a high degree of cyclization (100%), whereas the CO2/water emulsion resulted in the formation of a polymer with a lower Mv and increased porosity. Polymers were characterized by 1HNMR, FTIR, DSC, TLC, GPC, and viscometry tests. The results were presented and thoroughly discussed.

Two-dimensional crystallization of cyclopolymers

Free-standing 2D polymer materials with graphene-like crystalline layers hold great promise for many state-of-art applications. However, their fabrication remains challenging. A ferrocene tethered cyclopolymer (pFcMMA) is synthesized via the free radical polymerization of a divinyl monomer in this work. PFcMMA has a high degree of cyclization, but is not a stereo-regular structure like most vinyl polymers synthesized in free radical polymerization. PFcMMA can crystallize on the surface to form 2D crystals, which is evidenced by the birefringence phenomena, DSC and XRD analysis, and microscopic observation. Powder XRD of crystalline pFcMMA shows sharp interlayer diffraction, indicative of a highly crystalline phase. The crystallization process is supposed to follow the nonclassic crystallization pathway, i.e. the orientation of cyclopolymer main chains followed by the conformation transition of the side groups to form 2D crystalline layers. Variable temperature XRD combined with DSC analysis and polarizing optical microscopic observation demonstrate that the 2D crystalline phase begins to transition to a 3D crystalline phase at about 45 °C, the latter has a melting point at about 60 °C. The solid-solid crystalline transition is reversible and without intermediate melting, and the 2D crystalline phase is more stable at room temperature than the 3D phase. It is rationalized that nucleation from solutions is predominantly an entropy-driven process, while interactions between side groups and those between far separated main chains also benefit the formation of 2D crystalline phase. The commonalities of the crystallization processes of cyclopolymers are discussed. • A ferrocene tethered cyclopolymer forms 2D crystals on water surface. • The 2D crystalline phase undergoes a reversible solid-solid transition. • The 2D form appears to be the stable form at room temperature. • Formation of a 3D crystal at higher temperatures is observed. • The 2D crystallization process is entropy driven benefiting from group interactions.

Evolution and Regulation of Radial Structure of PAN Pre-Oxidized Fiber Based on the Fine Denier Model.

Affected by ambient oxygen and thermal diffusion mechanism, the radial structural distribution of polyacrylonitrile (PAN) fiber during the pre-oxidation process will be inherited to the carbon fiber, which had a remarkable effect on the mechanical properties of carbon fiber. It is important to understand the evolution mechanism of radial structure evolution of PAN fiber during the pre-oxidation process to manufacture the high-performance carbon fiber. In this paper, a series of fine denier model fibers were prepared by adjusting the oxygen concentration to describe the structural characteristics at different radial regions of pre-oxidized fibers. The evolution mechanism of the radial structure of pre-oxidized fiber, with the increase of heat treatment temperature, was studied by the methods of optical microscope, C13 nuclear magnetic resonance (13C-NMR), and thermogravimetric analyzer (TGA). The results showed that along the radial direction of pre-oxidized fiber from skin to core layer, the degree of cyclization changed little while the dehydrogenation and oxygen-containing structure gradually decreased. Specifically, the oxygen-containing functional groups in the core decreased to the lowest level or even disappeared. A moderate increase of temperature in the initial and middle pre-oxidation processes could effectively promote the formation of cyclized structure and stabilize cross-linked ladder structure in the skin region of the fiber. With it, the thermal stability of obtained pre-oxidation fiber was improved.

Constructing Stable Chromenoquinoline-Based Covalent Organic Frameworks via Intramolecular Povarov Reaction.

Chemically stable chromenoquinoline (CQ)-based covalent organic frameworks (COFs) were constructed by postsynthetic conversion of imine COFs. The key step of an intramolecular Povarov reaction can transform a preintegrated alkyne group to bridge the benzene rings on both sides of the imine linkage via chemical bonds, affording a ladder-type CQ linkage. This novel approach achieves a high cyclization degree of 80-90%, which endows the CQ-COFs with excellent chemical stability toward strong acid, base, and redox reagents. The synthetic approach can be applied to various monomers with different symmetries and functional core moieties. The absorption and fluorescence intensities of CQ-COFs are sensitive to acid, which allows for dual-mode sensing of strongly acidic environments.

Study on the structural evolution of polyacrylonitrile fibers in stepwise heat treatment process and its relationship with properties

AbstractThe structural evolution of polyacrylonitrile fibers in stepwise heat treatment process and its relationship with properties were investigated systematically. Results demonstrated that the cyclization degree and dehydrogenation index of fibers reached 84.13% and 1.361, respectively after stabilization at 265°C. The oxygen reaction was enhanced after stabilized at 245°C. Refinement of the microcrystalline structure took effect during stabilization and low temperature carbonization, while growth of microcrystalline dominated during high temperature carbonization. The results of surface topography study not only provided the evolution characteristics of surface microstructure under the influence of chemical reaction, but also further complements the internal aggregation structural rearrangement process from the side. Additionally, the temperature zone from 245 to 265°C was the key stage of the formation of the skin‐core structure, which would be transmitted to the resultant carbon fiber. Tensile strength and tensile modulus decreased during stabilization stage, reaching 4.273 GPa and 221.132 GPa, respectively after high temperature carbonization. The elongation at break which first increased and then decreased proved a toughness failure to brittleness failure. The investigation elucidated the relationship between the mechanical property with chemical and physical microstructure. And the possible rearrangement process of the aggregation structure was proposed.