纳米SiO2增强PAM/PEI冻胶的制备及性能

以十六烷基三甲基溴化铵改性SiO2为增强剂构建C-SiO2/聚丙烯酰胺(PAM)/聚乙烯亚胺(PEI)冻胶体系,模拟油藏环境对其抗温性、抗盐性、长期稳定性进行了考察.结果表明,C-SiO2/PAM/PEI冻胶体系在酸性环境下不能成胶,当pH≥7时,C-SiO2/PAM/PEI冻胶体系成胶时间缩短,强度增强.温度由30℃提高到120℃,成胶时间由20 h缩短为1 h,冻胶强度不断提高,在120℃下最终成胶强度可达到I级.矿化度由0 mg/L上升到1.0×105 mg/L,成胶时间从3 h延缓为5 d,成胶强度由I级降为G级.在120℃下、pH为9、矿化度为7.0×104 mg/L NaCl溶液中,C-SiO2/PAM/PEI冻胶体系最终强度可达到H级,表观黏度可达6.0×105 mPa·s左右,且维持360 d以上不脱水,具有良好的长期稳定性.结果表明,C-SiO2本身的强度提高了冻胶体系的强度、耐温性和长期稳定性.     

Polyethylenimine‐Based Shape Memory Polyurethane with Low Transition Temperature and Excellent Memory Performance

Flexible shape memory polyurethanes (SMPUs) are the favorable candidates as a coating or substrate for wearable smart textiles, electronics, and biomedical applications. However, conventional SMPUs (e.g., 1,4 butanediol (BDO)‐based) are not suitable in these applications due to high rigidity, poor mechanical properties, low shape recovery, and high transition temperature. Herein, a polyethylenimine (PEI)‐based SMPU with low transition temperature and tailored properties are reported. The synthesized SMPU are characterized, and their properties are compared with BDO‐SMPUs. The chemical structure of PEI is explored to improve thermal and mechanical properties and to assess their effect on shape memory behavior. The bulky nature of PEI plays a critical role in lowering transition temperature and introduces flexibility in the structure at room temperature. A drop in Young's modulus is found from 13.6 MPa in BDO‐SMPU to 6.2 MPa in PEI‐SMPU. Simultaneously, tensile strength is increased from 3.77 MPa in BDO‐SMPU to 11.85 MPa in PEI‐SMPU. Owing to the improved mechanical properties in PEI‐SMPU, 100% shape recovery is observed, which displays a reproducible trend in ten repetitive cycles due to the presence of reversible physical crosslinks. Therefore, it is envisioned that this can serve as a potential shape memory material in smart wearable technologies.     

Stimuli-triggered structural engineering of synthetic and biological polymeric assemblies

Response to external stimuli is a fundamental and intrinsic behavior of living systems. There has been increasing interest for designing and constructing responsive polymeric superstructures by self-assembly. Stimuli-induced self-assembly and post-assembly triggering strategies provide an alternative approach for the manipulation of self-assembled architectures of either biological or synthetic polymeric materials. Stimuli-induced structural transformations may produce ensembles with new topologies or materials with exceptionally complex features inaccessible via conventional self-assembly processes. This is in contrast to materials that simply undergo stimuli-induced degradation, or disassembly processes. Since a variety of cellular processes depend on responses to environmental stimuli that lead to more complexity and increased function, and are related to structural transitions over the nano- to microscale, insights into stimuli-triggered morphogenesis can further deepen our understanding of cellular behaviors. Indeed, an understanding of these processes will likely inspire scientists to develop materials with advanced and tailored architectures for biosensing, diagnosis and therapy as well as other biomedical applications. Herein, we highlight state-of-the-art achievements in the stimuli-triggered structural manipulation of polymer assemblies. Furthermore, future developments in this nascent and growing field are briefly discussed.     

Enhanced Antimicrobial Activity of Amine-Phosphonium (N-P) Hybrid Polymers Against Gram-Negative and Gram-Positive Bacteria

The authors report synthesis, characterization and evaluation of a series of linear polyethylenimine (lPEI)-grafted butyltriphenylphosphonium bromide (LBTP) polymers (N-P hybrid polymers) for their antimicrobial activity on various Gram-positive and Gram-negative bacteria. Polymers with ～5.8–13.8% substitution of butyltriphenylphosphonium bromide (BTP) on the backbone of lPEI showed enhanced charge density as compared to native lPEI confirming the conjugation of BTP onto lPEI. These modified polymers displayed low hemolytic activity and excellent antimicrobial activity against these two types of bacteria with one of the modified polymers, LBTP-40, was found to exhibit high antimicrobial activity in all the strains.     

以聚乙烯亚胺作为电子注入层的聚合物发光器件特性研究

在传统结构与倒置结构的有机发光二极管(LED)的聚合物发光层和阴极之间加入聚乙烯亚胺(PEIE)层能够显著地提高器件的发光效率。通过采用不同厚度的PEIE层的器件发光特性研究表明:PEIE层作为电子注入层(EIL)/空穴阻挡层(HBL)来平衡器件中的电子和空穴浓度,这主要来源于PEIE作为界面偶极层,能有效地降低阴极与发光层之间的电子注入势垒。     

Folic‐Acid‐Targeted Self‐Assembling Supramolecular Carrier for Gene Delivery

A targeting gene carrier for cancer‐specific delivery was successfully developed through a “multilayer bricks‐mortar” strategy. The gene carrier was composed of adamantane‐functionalized folic acid (FA‐AD), an adamantane‐functionalized poly(ethylene glycol) derivative (PEG‐AD), and β‐cyclodextrin‐grafted low‐molecular‐weight branched polyethylenimine (PEI‐CD). Carriers produced by two different self‐assembly schemes, involving either precomplexation of the PEI‐CD with the FA‐AD and PEG‐AD before pDNA condensation (Method A) or pDNA condensation with the PEI‐CD prior to addition of the FA‐AD and PEG‐AD to engage host–guest complexation (Method B) were investigated for their ability to compact pDNA into nanoparticles. Cell viability studies show that the material produced by the Method A assembly scheme has lower cytotoxicity than branched PEI 25 kDa (PEI‐25KD) and that the transfection efficiency is maintained. These findings suggest that the gene carrier, based on multivalent host–guest interactions, could be an effective, targeted, and low‐toxicity carrier for delivering nucleic acid to target cells.     

Dually stimuli‐responsive hyperbranched polyethylenimine with LCST transition based on hydrophilic–hydrophobic balance

Dually stimuli‐responsive hyperbranched polyethylenimine derivatives (HPEI‐star‐PPOs) were successfully synthesized through Michael addition of commercial HPEI, poly(propylene oxide) dimethacrylate, and 2‐mercaptoethanol. In aqueous solution, these HPEI‐star‐PPOs exhibited response to temperature and pH. The corresponding lower critical solution temperature (LCST) could be readily adjusted by changing the feed ratio of HPEI to PPO, which also presents the ratio of hydrophilicity to hydrophobicity, indicating that this LCST transition is based on hydrophilic–hydrophobic balance. Because of the tertiary amine as well as unreacted primary or secondary amine that can be protonated during pH decreases, HPEI‐star‐PPOs exhibited a pH‐dependent thermoresponse. The 3‐(4,5‐dimethyl‐thiazol‐2‐yl)‐2,5‐diphenyl tetrazolium bromide assay against COS‐7 cells demonstrated that HPEI‐star‐PPO had relatively low cytotoxicity compared to HPEI. All these characteristic suggest that this stimuli‐responsive polymer is a promising functional material for biomedical applications. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Preparation of a Facilitated Transport Membrane Composed of Carboxymethyl Chitosan and Polyethylenimine for CO2/N2 Separation

The miscibility of carboxymethyl chitosan/polyethylenimine (CMCS/PEI) blends was analyzed by FT-IR, TGA and SEM. Defect-free CMCS/PEI blend membranes were prepared with polysulfone (PSf) ultrafiltration membranes as support layer for the separation of CO₂/N₂ mixtures. The results demonstrate that the CMCS/PEI blend is miscible, due to the hydrogen bonding interaction between the two targeted polymers. For the blended membrane without water, the permeability of CO₂ gas is 3.6 × 10⁻⁷ cm³ cm⁻² s⁻¹ cmHg⁻¹ and the corresponding separation factor for CO₂ and N₂ gas is about 33 at the pressure of 15.2 cmHg. Meanwhile, the blended membrane with water has the better permselectivity. The blended membrane containing water with PEI content of 30 wt% has the permeance of 6.3 × 10⁻⁴ cm³ cm⁻² s⁻¹ cmHg⁻¹ for CO₂ gas and a separation factor of 325 for CO₂/N₂ mixtures at the same feed pressure. This indicates that the CO₂ separation performance of the CMCS/PEI blend membrane is higher than that of other facilitated transport membranes reported for CO₂/N₂ mixture separation.     

Metal Oxide Transistors via Polyethylenimine Doping of the Channel Layer: Interplay of Doping,Microstructure, and Charge Transport

Polymer doping of solution‐processed In₂O₃ with small amounts of the electron‐rich polymer, polyethylenimine (PEI), affords superior transistor performance, including higher electron mobility than that of the pristine In₂O₃ matrix. PEI doping of In₂O₃ films not only frustrates crystallization and controls the carrier concentration but, more importantly, acts as electron dopant and/or scattering center depending on the polymer doping concentration. The electron donating capacity of PEI combined with charge trapping and variation in the matrix film microstructure yields, for optimum PEI doping concentrations of 1.0%–1.5%, electron mobilities as high as ≈9 cm² V^?1 s^?1 on a 300 nm SiO₂ gate dielectric, an excellent on/off ratio of ≈10⁷, and an application optimal V _T. Importantly, these metrics exceed those of the pure In₂O₃ matrix with a maximum mobility ≈4 cm² V^?1 s^?1. Furthermore, we show that this approach is extendible to other oxide compositions such as IZO and the technologically relevant IGZO. This work opens a new means to fabricate amorphous semiconductors via solution processing at low temperatures, while preserving or enhancing the mobility of the pristine polycrystalline semiconductor.     

Spectroscopic study of the modification of cellulose with polyethylenimines

The reaction of cellulose with polyethylenimines (PEIs) was studied using diffuse reflectance ultraviolet–visible (UV–vis) spectroscopy, diffuse reflectance FTIR spectroscopy, and standard colorimetry. PEIs were applied from aqueous solutions at the natural pH (pH ～ 11) and at pH = 6. The obtained materials were exposed to different thermal treatments in air. Celluloses treated at pH = 11 suffer the reversible formation of amine bicarbonate salts. This reaction was not observed in celluloses treated at pH = 6 because of the protonation of the amine groups. In all treated celluloses, the PEI amine groups reacted with cellulose carbonyl groups at moderate temperatures to form Schiff bases, which were responsible for the yellowing of the material. At higher temperatures other oxidation products were detected in the UV–vis and infrared spectra. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 92: 2196–2202, 2004