Studies on Organosoluble Polyimides Based on a Series of New Asymmetric and Symmetric Dianhydrides: Structure/Solubility and Thermal Property Relationships

Haojun Fan,Ke Zeng,Qiao Guo,Shuai Gao,Dimeng Wu,Gang Yang 한국고분자학회 2012 Macromolecular Research Vol.20 No.1

A series of new asymmetric biphenyl dianhydrides, 2-phenoxy(o-methylphenoxy, m-methylphenoxy, and p-methylphenoxy)-4,4,5,5-biphenyltetracarboxylic dianhydrides, was readily synthesized using a five-step route. A new symmetric biphenyl dianhydride, 2,2-di(o-methylphenoxy)-4,4,5,5-biphenyltetracarboxylic dianhydride, was also synthesized using the similar procedure. The polyimides were prepared from such new dianhydrides and commercial diamines by high-temperature one-step polymerization. The asymmetric and symmetric substituent solubility and thermal property relationships of the resulting polyimides were investigated. Interestingly, the thermally reversible sol–gel transitions were observed for the polymer solutions of the polyimides derived from those asymmetric dianhydrides and 1,4-phenylenediamine (p-PDA). Unexpectedly, the polyimides derived from asymmetric dianhydrides did not show better organosolubility than those of the homologous polyimides derived from symmetric dianhydrides. The structures of the substituents (phenoxy, o-methylphenoxy, m-methylphenoxy and p-methylphenoxy)have a significant effect on both the solubility and the thermal properties of these polyimides. The polyimides derived from asymmetric dianhydrides show enhanced thermal properties relative to the symmetric dianhydridesderived polyimides. These results can be attributed to their different degrees of molecular packing revealed by wideangle X-ray diffraction measurements.

Thermal Sensitive Polyurethane Membranes with Desirable Switch Temperatures

Hu Zhou,Jianxian Zeng,Haojun Fan,Yuansen Liu,Jian Zhou 한국고분자학회 2010 Macromolecular Research Vol.18 No.11

Chemical synthesis and physical blending methods were used to prepare thermal sensitive polyurethanes (TSPU) with single or double thermal switches. In the design of the formula, polycaprolactone diol (PCL) with a molecular weight 10,000 and 4,000 and polytetramethylene glycol (PTMG) with a molecular weight 3,000 and 2,000 were used as the soft segments. The effects of the crystallinity and compatibility of the soft segments on the phase transition temperatures of the soft segments of TSPU (defined as switch temperature, Ts) were investigated in detail. To examine the thermal sensitivity of the thermal switch, water vapor permeability (WVP) experiments were performed to investigate the mass transport as a function of temperature. Differential scanning calorimetry (DSC)indicated that all the original TSPUs had a phase separated structure that was independent of the phase transition temperature of the soft and hard segments. The Ts values are determined mostly by the melting temperatures of the soft segments. On the other hand, for their blends, the Ts values are determined by the compatibility of the soft segments and the blending weight ratio. The blends of the PCL-based TSPUs showed good compatibility and single Ts due to the similar structure of the soft segments (just a difference in molecular weight), whereas for the PCL-based and PTMG-based TSPUs (the molecular structure is very different) blends, the Ts two independent values and blending weight ratio-dependent features due to the difference in the structure of the soft segments. Water vapor permeability analysis revealed the mass transport showed switching features to thermal stimuli, i.e. when the temperature reached the Ts, the WVPs of membranes showed rapid changes. On the other hand, the sensitivity of the thermal switch characterized by WVP improvement showed a dependence on the degree of crystallinity of the soft segments,i.e. well-organized soft segment structure is beneficial for improving the thermal sensitivity. Overall, TSPU membranes with a single Ts and different thermal sensitivity can be prepared using different crystalline poly-diols as the soft segments and blending two types of TSPUs with similar soft segments in the molecule structure, whereas TSPU with a double Ts can be achieved easily by blending two types of TSPUs with different soft segments.

Thermo-Sensitive Polyurethane Membrane with Controllable Water Vapor Permeation for Food Packaging

Zhou, Hu,Shit, Huanhuan,Fan, Haojun,Zhou, Jian,Yuan, Jixin The Polymer Society of Korea 2009 Macromolecular Research Vol.17 No.7

The size and shape of free volume (FV) holes available in membrane materials control the rate of gas diffusion and its permeability. Based on this principle, a segmented, thermo-sensitive polyurethane (TSPU) membrane with functional gate, i.e., the ability to sense and respond to external thermo-stimuli, was synthesized. This smart membrane exhibited close-open characteristics to the size of the FV hole and water vapor permeation and thus can be used as smart food packaging materials. Differential scanning calorimetry (DSC), dynamic mechanical analysis (DMA), positron annihilation lifetimes (PAL) and water vapor permeability (WVP) were used to evaluate how the morphological structure of TSPU and the temperature influence the FV holes size. In DSC and DMA studies, TSPU with a crystalline transition reversible phase showed an obvious phase-separated structure and a phase transition temperature at $53^{\circ}C$ (defined as the switch temperature and used as a functional gate). Moreover, the switch temperature ($T_s$) and the thermal-sensitivity of TSPU remained available after two or three thermal cyclic processes. The PAL study indicated that the FV hole size of TSPU is closely related to the $T_s$. When the temperature varied cyclically from $T_s-10{\circ}C$ to $T_s+10^{\circ}C$, the average radius (R) of the FV holes of the TSPU membrane also shifted cyclically from 0.23 to 0.467 nm, exhibiting an "open-close" feature. As a result, the WVP of the TSPU membrane also shifted cyclically from 4.30 to $8.58\;kg/m^2{\cdot}d$, which produced an "increase-decrease" response to the thermo-stimuli. This phase transition accompanying significant changes in the FV hole size and WVP can be used to develop "smart materials" with functional gates and controllable water vapor permeation, which support the possible applications of TSPU for food packaging.

Synthesis and Application of Phosphorus-containing Flame Retardant Plasticizer for Polyvinyl Chloride

Fang Wang,Siyu Pan,Peikun Zhang,Haojun Fan,Yi Chen,Jun Yan 한국섬유공학회 2018 Fibers and polymers Vol.19 No.5

A novel phosphorus-containing flame retardant plasticizer (PFRP) derived from castor oil acid methyl ester (COME) was synthesized to substitute dioctyl phthalate (DOP) for plasticizing polyvinyl chloride (PVC) products. The chemical structures of PFRP were confirmed by fourier transform infrared spectroscopy (FTIR) and 1H nuclear magnetic resonance (1H NMR). Meanwhile, the plasticizing effect, flammability and thermal stability of plasticized PVC films were investigated by dynamic mechanical analyzer (DMA), limiting oxygen index (LOI) test, scanning electron microscope (SEM) and thermogravimetric analysis (TGA). As the PFRP content increasing from 0 wt% to 50 wt% amount of plasticizers, the plasticizing efficiency and the mechanical properties showed a slightly decreasing tendency compared with that of DOP, while the LOI value of plasticized PVC increased remarkably from 21.5 % to 25.2 %, showing a combined plasticizing efficiency and flame retardancy. SEM and TGA analysis indicated that PFRP had little effect on thermal stability but was effective to promote the formation of compact carbon residue.

Prognostic Perspectives of STING and PD-L1 Expression and Correlation with the Prognosis of Epstein-Barr Virus-Associated Gastric Cancers

( Qi Sun ),( Yao Fu ),( Xiaobing Chen ),( Lin Li ),( Hongyan Wu ),( Yixuan Liu ),( Haojun Xu ),( Guoren Zhou ),( Xiangshan Fan ),( Hongping Xia ) 대한소화기기능성질환·운동학회 2022 Gut and Liver Vol.16 No.6

Background/Aims: Epstein-Barr virus-associated gastric cancers (EBVaGCs) have unique molecular and clinicopathological characteristics. The cyclic GMP-AMP synthase-stimulator of interferon genes (STING) pathway is recently recognized as the critical innate immunity against pathogens and tumors. STING is also a master regulator in the cancer-immunity cycle and targeting STING could synergize with existing immune-checkpoint therapies. However, the role of STING in GC, especially in EBVaGC, and its correlation with programmed death-ligand 1 (PD-L1) remain largely unclear. Methods: We collected 78 cases of EBVaGCs and 210 cases of EBV-negative GC (EBVnGC) from a total of 1,443 cases of GC analyzed by EBV-encoded small RNA in situ hybridization. We investigated STING and PD-L1 expression and their concomitant prognostic value in EBVaGCs and EBVnGCs using tissue microarray and immunohistochemistry. The effects of STING and PD-L1 expression on the overall survival of patients with EBVaGC or EBVnGC were assessed by univariate and multivariate analysis. Results: We found that both STING and PD-L1 exhibited significantly higher expression in the EBVaGCs than that in the EBVnGCs. The expression of STING was positively correlated with that of PD-L1 in EBVaGCs. Simultaneous negative expression of STING and PD-L1, and positive expression of STING were independent prognostic risk factors for EBVaGC and EBVnGC, respectively. Conclusions: This is the first prognostic retrospective study of STING and PD-L1 expression and the prognosis among EBVaGC and EBVnGC. The expression and prognostic value of STING and PD-L1 are different in the two types of GCs. STING and PD-L1 are promising prognostic biomarkers and therapeutic targets for EBVaGC and EBVnGC. (Gut Liver 2022;16:875-891)

Antibacterial and Antioxidant Composite Fiber Prepared from Polyurethane and Polyacrylonitrile Containing Tea Polyphenols

Ya Wen,Ruifang Zhao,Xueqian Yin,Yidong Shi,Haojun Fan,Yi Zhou,Lin Tang 한국섬유공학회 2020 Fibers and polymers Vol.21 No.1

Antibacterial and antioxidant properties exert an indispensable effect on biomedical and packaging materialswhich are mainly made of fiber-based fabrics. The current research illustrates a novel type of composite fiber which wasprepared from thermoplastic polyurethane (PU), polyacrylonitrile (PAN) and tea polyphenols (TP) through wet-spinningtechnology. The PU-PAN mass ratio was optimized upon the mechanical property; TP was incorporated into the compositefiber with different contents. The obtained fibers were fully characterized in terms of mechanical, thermal, morphologicalproperties as well as surface wettability. Additionally, in vitro TP release, antioxidant and antibacterial activity of suchcomposite fibers before and after washing were under investigation systematically and orderly. The findings showed that TPloadedcomposite fibers with an average diameter around 120 μm performed a sustained TP release behavior and desirablecytocompatibility. According to the capacity on scavenging 2, 2-diphenyl-1-picrylhydrazyl (DPPH) free radicals, theobservation of scavenging ratio reaching to 97 % proved the excellent antioxidant performance. Furthermore, the idealantibacterial activity against Gram-negative E. coli and Gram-positive S. aureus was also demonstrated. Collectively, thisstudy provides a facile strategy to design and prepare a novel type of composite fibers and fabrics, which may be put intoapplication as wound dressing and tissue conduit.