One-pot Synthesis of Pd/Azo-polymer as an Efficient Catalyst for 4-Nitrophenol Reduction and Suzuki-Miyaura Coupling Reaction

The porous polymer matrix with good stability and confined microenvironment is considered as ideal support to stabilize isolated metal centers for catalysis. Herein, we report a “one-pot” method to prepare a kind of palladium complexed with azo porous organic polymer nanospheres (Pd-azo-POPs). The method combines the synthesis of azo-POPs with the reduction of the Pd ion, where azo serves as an anchoring group to limit the growth of Pd. The unique structure is conductive to the formation of a uniform active center and provides improved electron transfer. Pd-azo-POPs-80 exhibits a high catalytic activity and cycling stability both in 4-nitrophenol reduction and Suzuki-Miyaura coupling. The k_nor for the 4-nitrophenol reduction was 174.7 min⁻¹ mM⁻¹ and the conversion remains above 90% after 6 cycles. Meanwhile, the yield was still up to 94.5% after 5 cycles for the Suzuki-Miyaura coupling reaction of benzene derivatives with I/Br under mild conditions.     

离子液体/石墨烯复合光固化涂层的制备及性能研究

石墨烯在聚合物基体中分散不良是制约其应用的一个重要原因，尤其在石墨烯含量较高时，团聚不可避免。本文通过季铵化、亲核取代和阴离子置换反应，合成了双官光聚合离子液体单体。将其与石墨烯混合分散后，再和光固化环氧丙烯酸树脂6215-100复配，制备不同比例的复合涂层配方，并采用UV固化的方式在玻璃基材上成膜。利用衰减傅里叶全反射红外（ATR-FTIR）和核磁氢谱（¹HNMR）对可聚合离子液体单体进行结构表征，而复合配方的光聚合动力学、涂层的热性能和石墨烯的分散情况则通过实时红外（RTIR）、热重分析（TGA）和显微镜等手段进行表征。结果表明，光聚合离子液体对于石墨烯的分散具有良好的促进作用，涂层在1%和3%石墨烯含量的情况下表现出良好的热性能。     

Tailoring the Crystallization Behavior and Mechanical Property of Poly(glycolic acid) by Self-nucleation

Chinese Journal of Polymer Science - Biocompostable poly(glycolic acid) (PGA) crystallizes slowly under fast cooling condition, leading to poor mechanical performance of the final products. In this...     

双亲性石墨烯量子点的合成及对L-薄荷醇的缓释作用

将柠檬酸和直链烷基胺混合后热解, 制备了烷基胺功能化的双亲性石墨烯量子点. 研究结果表明, 烷基碳链长度对石墨烯量子点的表面活性有较大影响. 采用十二烷基胺为功能试剂时, 石墨烯量子点的表面张力降低到30.8 mN/m, 与典型的阴离子表面活性剂十二烷基苯磺酸钠相当. 此双亲性石墨烯量子点被用作固体粒子表面活性剂稳定L-薄荷醇/水Pickering乳液时, 所形成的乳液具有较高的稳定性, 液滴平均粒径为10 μm. 该乳液冷却至室温后析出结晶, 将晶体过滤、 干燥后得到负载L-薄荷醇的石墨烯量子点. 采用热风吹扫方式研究石墨烯量子点对L-薄荷醇的缓释行为. 在80 ℃下, 负载型样品完全释放薄荷醇所需要的时间分别为混合型样品和空白样品的4.6倍与9.2倍, 表明石墨烯量子点对L-薄荷醇具有明显的缓释作用.     

聚合物纳米组装体修饰丝网印刷电极构建过氧化氢传感器

通过在聚合物结构中同时引入生物亲和单体和电活性单体,使得聚合物组装体在修饰丝网印刷电极时兼具提高比表面积、保持酶活和促进电子转移功能,从而发展了一种简单、高效构建电化学传感器的方法。 以苯乙烯(St)、丙烯酸(AA)、N-乙烯基咔唑(VCz)和甲基丙烯酸二甲氨基乙酯(DMAEMA)为单体自由基聚合合成双亲性无规共聚物Poly(St-co-AA-co-VCz-co-DMAEMA)(PSACD),将聚合物在选择性混合溶剂DMF/H₂O中自组装得到聚合物纳米粒子PSACD NPs。 利用纳米粒度分析仪、扫描电子显微镜(SEM)对其进行表征。 依次将PSACD NPs水分散液、辣根过氧化物酶(HRP)溶液和全氟磺酸-聚四氟乙烯共聚物(Nafion,NF)溶液滴涂在丝网印刷碳电极(SPCE)上,制备得到过氧化氢生物传感器。 通过计时电流法对传感器性能进行研究,表明该传感器对H₂O₂在0.02~7.48 mmol/L有良好的线性响应,且响应时间短(<2 s),具有良好的选择性和稳定性。     

Divergent synthesis of spirocyclopentene-pyrazolones and pyrano[2,3-c]-pyrazoles via Lewis base controlled annulation reactions

An effective Lewis base catalyst-controlled α-regioselective annulation reaction of γ-substituted allenoates with unsaturated pyrazolones has been developed, affording various spirocyclopentene-pyrazolones and pyrano[2,3-c]pyrazoles. The combination of PPh₃ and K₂CO₃ promoted the [3+2] annulation to access the spirocyclopentene-pyrazolones in moderate to good yields (up to 90%) with excellent diastereoselectivities (dr >19:1), while [4+2] annulations to generate pyrano[2,3-c]pyrazoles were successfully achieved by employing DBU as catalyst (in up to 92% yield). Of importance, the asymmetric synthesis of spirocyclopentene-pyrazolone was realized by using our previously reported chiral ferrocenylphosphine catalyst.     

IMDA reaction in a synthetic approach towards a natural kijamicin aglycon analog

In our program of new macrocyclic antibiotic derivatives synthesis, a natural kijamicin analog was isolated, disclosing important antibiotic and antiviral properties, which are under investigation. In this paper we describe a synthesis of the bottom half C1-C14 (n = 1) of its aglycon. This strategy was based on the preparation of a tetraene derivative via a palladium catalyzed Stille coupling reaction, the final step involving an IMDA cyclization key step.     

Preparation of microporous membranes by paste method

Microporous membranes were prepared by the paste method. Certain properties of the resultant microporous membranes such as porosity, pore size, specific surface area, and N₂ gas permeability were estimated. Furthermore, the membrane structure was observed with the aid of scanning electron microscopy. It was elucidated that the membranes consist of aggregates of minute spherical particles, made up of poly(styrene-divinylbenzene) with micropores.     

Selective C-C bonds formation,N-alkylation and benzo[d]imidazoles synthesis by a recyclable zinc composite

Earth abundant metals are much less expensive, promising, valuable metals and could be served as catalysts for the borrowing hydrogen reaction, dehydrogenation and heterocycles synthesis, instead of noble metals. The uniformly dispersed zinc composites were designed, synthesized and carefully characterized by means of XPS, EDS, TEM and XRD. The resulting zinc composite showed good catalytic activity for the N-alkylation of amines with amines, ketones with alcohols in water under base-free conditions, while unsaturated carbonyl compounds could also be synthesized by tuning the reaction conditions. Importantly, it was the first time to realize the synthesis of 2-aryl-1H-benzo[d]imidazole derivatives by using this zinc composite under green conditions. Meanwhile, this zinc catalyst could be easily recovered and reused for at least five times.