Molecularly Designed Stabilized Asymmetric Hollow Fiber Membranes for Aggressive Natural Gas Separation

New rigid polyimides with bulky CF₃ groups were synthesized and engineered into high‐performance hollow fiber membranes. The enhanced rotational barrier provided by properly positioned CF₃ side groups prohibited fiber transition layer collapse during cross‐linking, thereby greatly improving CO₂/CH₄ separation performance compared to conventional materials for aggressive natural gas feeds.     

Azido-Functionalized Fullerenes,Perylenediimide, Perylene,and Tetraphenylethylene as Crosslinkers for Applications in Materials Science

This study presents the synthesis and characterization of novel azido molecules with demonstrated crosslinking ability when used as additives in polymer/fullerene organic solar cells. These compounds derived from fullerenes C₆₀ and C₇₀, or dyes from perylenediimide, perylene and tetraphenylethylene frameworks, bearing a different number of azido groups, are of particular interest to stabilize and increase the thermal stability of the device morphology. In particular, the electro and photoactive dye derivatives allow the introduction of additional functionality with the possibility of extending the absorption domain of the photoactive layer. In addition, and more broadly, such azido crosslinkers could find applications in the field of optoelectronic devices as a simple and cheap strategy to improve the performance and long-term stability of organic solar cells, perovskites solar cells, or organic light-emitting diodes.     

Fabrication of Insoluble Elastin by Enzyme-Free Cross-Linking

Elastin is an essential extracellular matrix protein that enables tissues and organs such as arteries, lungs, and skin, which undergo continuous deformation, to stretch and recoil. Here, an approach to fabricating artificial elastin with close-to-native molecular and mechanical characteristics is described. Recombinantly produced tropoelastin are polymerized through coacervation and allysine-mediated cross-linking induced by pyrroloquinoline quinone (PQQ). A technique that allows the recovery and repeated use of PQQ for protein cross-linking by covalent attachment to magnetic Sepharose beads is developed. The produced material closely resembles natural elastin in its molecular, biochemical, and mechanical properties, enabled by the occurrence of the cross-linking amino acids desmosine, isodesmosine, and merodesmosine. It possesses elevated resistance against tryptic proteolysis, and its Young's modulus ranging between 1 and 2 MPa is similar to that of natural elastin. The approach described herein enables the engineering of mechanically resilient, elastin-like materials for biomedical applications.     

Self-catalytic cross-linking reaction and reactive mechanism studies of α-aminomethyl triethoxysilanes for α,ω-dihydroxy poly(dimethylsiloxane)

Some kinds of aminomethyl triethoxysilanes, cross-linkers of α,ω-dihydroxy poly(dimethylsiloxane) (PDMS), can act as catalyst to self-catalyze the cross-linking reaction with PDMS, as found in our studies. Three kinds of α-aminomethylsilanes, [(diethyl)aminomethyl triethoxysilane (DMTS), anilinomethyl triethoxysilane (AMTS) and cyclohexylaminomethyl triethoxysilane (CMTS)], and two kinds of γ-aminopropyl silanes, [(γ-aminopropyl triethoxysilane (APTS) and (N-β-aminoethyl)-γ-aminopropyl triethoxysilane (AATS)] were selected to study the self-catalytic cross-linking reaction and its mechanism. The reactivity of the cross-linkers determined by n-hexane extraction experiments, was found to be DMTS > CMTS ? AMTS, but APTS and AATS could not react with PDMS without catalysis. The cross-linking degree was increased with the reactivity. The results of extraction experiments and Fourier transform infra-red (FT-IR) spectra indicated that the cross-linking reaction was an equimolar reaction between the Si-OH groups and Si-OC₂H₅ groups. Formation of electron conjugation of N and Si in α-aminomethyl triethoxysilane molecules has been proposed to elucidate the mechanism of the self-catalytic cross-linking reaction. The Modulated Differential Scanning Calorimeter (MDSC) results showed that the increase of the glass-transition temperature (T_g) of the cross-linked products was dependent on the reactivity of the cross-linkers. The thermo-gravimetric analysis (TGA) results demonstrated that the thermal stabilities of the cross-linked products were also related to the reactivity and the structures of the cross-linkers.     

基于水杨醛席夫碱锌配合物交联稳定化荧光聚合物胶束的合成及其对铜离子的荧光响应性

以S-十二烷基-S'-(α,α'-二甲基-α″-乙酸)-三硫代碳酸酯(DMAT)为链转移剂、2-羟基-5-乙烯基苯甲醛(HVB)为单体,利用可逆加成-断裂链转移自由基聚合法(RAFT)合成结构明确、数均相对分子质量可控的水杨醛聚合物(PHVB)。将PHVB直接地与单端胺基功能化聚乙二醇(m PEG-NH2)按n(—NH2group)/n(—CHO group)=0.50投料进行醛-胺缩合反应,获得接枝率为50%的两亲性接枝水杨醛席夫碱聚合物PHVB-graft-PEG。采用凝胶渗透色谱仪(GPC)和核磁共振氢谱(1H NMR)对合成的聚合物的数均相对分子质量和结构进行了确证。将PHVB-graft-PEG直接地分散于无水乙醇中,自组装形成以聚乙烯水杨醛席夫碱为核、聚乙二醇为壳的胶束,然后以所得胶束为微反应器,与Zn(OAc)2进行配位反应得到外壳为可溶性链段PEG,内核为发光水杨醛席夫碱锌配合物的PHVB-graft-PEG/Zn~(2+)交联稳定化胶束。通过紫外-可见分光光谱(UV-Vis)、荧光发射光谱(FLL)、动态光散射(DLS)和透射电子显微镜(TEM)分别对胶束的交联稳定化过程进行了表征。研究结果表明,经交联稳定化后,PHVB-graft-PEG/Zn~(2+)胶束在干燥后仍可在水和常见有机溶剂中再分散形成粒径大小约为100 nm、在约460 nm处发射出蓝光荧光的纳米粒子,并且可作为荧光传感器,在水溶液中对Cu~(2+)离子进行选择性识别,其荧光淬灭率与Cu~(2+)离子浓度(0~50μmol/L范围内)呈线性关系,最低检测下限至0.5μmol/L,而其它共存离子如Cd~(2+)、Mg~(2+)、Ni~(2+)、Pb~(2+)、Ca~(2+)、Hg~(2+)、Al3+、Mn~(2+)等对Cu~(2+)离子的荧光响应性没有干扰,即可实现对Cu~(2+)离子进行定量检测。     

纳米复合水凝胶的力学行为与刺激响应性

纳米复合水凝胶（nanocomposite hydrogels,NC凝胶）由于其简便的制备方法、独特的组成、优异的力学性能、高光学透明度以及良好的溶胀/去溶胀性等,引起了广泛的关注.近年来,本课题组在NC凝胶的力学行为及刺激响应性NC凝胶的制备方面取得了可喜的研究成果.观察到新合成的和溶胀平衡的聚N-异丙基丙烯酰胺（PNIPAm）-锂藻土LaponiteNC凝胶的超拉伸性,发现了在大应变下的应变硬化现象;发现利用Mooney-Rivlin方程可以描述NC凝胶的压缩应力-应变,但不能描述较大的应变硬化;Creton模型能很好地描述NC凝胶在大形变下的应力-应变曲线,特别是凝胶的应变硬化;从NC凝胶小应变下的平衡剪切模量得到了有效交联密度,观察到NC凝胶形变-回复过程的迟滞现象,测定了NC凝胶的松弛指数.我们认为NC凝胶具有超拉伸性的原因是其较低的交联密度和适度的松弛速率;在响应性NC凝胶的制备方面,发现了溶胶型Laponite的水分散液的稳定窗口,避免了加入离子性单体引起的聚集沉淀;通过共聚制备了具有超拉伸性、pH响应或温度和pH双响应的透明NC凝胶.本文主要综述了我们课题组在NC凝胶力学行为及响应性NC凝胶领域的一些研究进展,并分析了NC凝胶研究领域仍然未解决的科学问题,以及今后可能的发展方向.     

医用壳聚糖膜的制备和性能研究

研究了壳聚糖膜的制备方法和性能。探讨了壳聚糖浓度、甘油和戊二醛用量对壳聚糖膜性能的影响,并考察了膜的体外降解过程。结果表明w=．02的壳聚糖溶液成膜效果较好;甘油和戊二醛能王著改善壳聚糖膜的力学性能和尺寸稳定性能;溶茼酶-林格氏液中浸泡40d后膜的降解率为41．98％。满足引导组织再生材料的基本要求。该膜作为一种潜在的生物医用材料,将具有较广阔的应用前景。     

利用二氧化碳的缓慢释放控制聚丙烯酰胺在含柠檬酸铬水溶液中的粘度

Partially hydrolyzed polyacrylamide (HPAM) has been widely used for water shut-off and profile control to enhance oil recovery. Herein, we reported a novel technique by which the crosslinking between HPAM and Cr³⁺ in aqueous solutions at 60 ℃ can be delayed effectively. Citric acid was selected as an organic complexing agent of Cr³⁺ so that the crosslinking between HPAM and Cr³⁺ can be prevented completely. Due to the decomposition of the bicarbonate (HCO₃^-) embedded in solution, CO₂ released from solution and the pH value of solution increased gradually. The degree of ionization of HPAM and its ability to complex with Cr³⁺ increased accordingly. When the complexation of Cr³⁺ with HPAM is stronger than that with citric acid, the viscosity of the HPAM solution increased significantly. Under the closed condition, together with the existence of potassium dihydrogen phosphate (KH₂PO₄), the release of CO₂ was very slow and the condition was highly controlled so that the ionization of HPAM was prevented initially. Furthermore, the hydrogen bonding interactions between HPAM and melamine embedded in solution previously also postponed the ionization of HPAM. As a result, the crosslinking between HPAM and Cr³⁺ can be delayed for almost one month, completely meeting the requirements for deep water shut-off and profile control to enhance oil recovery.     

Influences of Plasma Treatment and 60Co γ-Ray Radiation on the Over-Voltage Positive Temperature Coefficient of High Density Polyethylene/Carbon Black Nano Composites

Argon plasma-pretreated high-density polyethylene (PHDPE) was blended with the conductive nano carbon black (CB) and inorganic flame retardant (magnesium hydroxide, Mg(OH)₂) was added. Influences of the CB content, plasma treatment time, plasma treatment power, and dosage of ⁶⁰Co γ-ray radiation on positive temperature coefficient (PTC) behaviors of composite were studied. In addition, the over-voltage resistance behavior of the composites was also investigated. The free radical of PHDPE was measured by 1,1-diphenyl-2-picryhydrazyl (DPPH) method. The gel contents of composite were measured by solvent extraction method. The results showed that the room-temperature volume resistivity and PTC effect of composite were improved significantly with plasma treatment. The PHDPE composite with ⁶⁰Co γ-ray radiation eliminated the negative temperature coefficient (NTC) effect in the composites effectively, and the PTC intensity of composite was increased. With increasing of radiation dosage from 20 Mrads to 80 Mrads, the gel content of composites increased up to 83.84% and the response temperature of composites shifted to low temperature (127.5 °C to 114.8 °C). In this work, the composites also successfully passed the over-voltage resistance test, and possessed good reproducibility.