FILLED POLYOLEFIN COMPOSITES PREPARED FROM IN-SITU POLYMERIZATION VIA A CATALYST-SUPPORTED APPROACH——Ⅰ.MORPHOLOGY OF PE IN CARBON BLACK(CB)/PE IN-SITU COMPOSITES

The morphology of PE in the in-situ CB/PE composites prepared from in-situ polymerization via a catalyst-supported approach was studied by DSC. It is found that both the melting peak temperature and crystallinity of the PE shelldecrease as filler level increases. The unexpected phenomena are ascribed to the strong interaction between PE and CB andthe very high specific area of CB. It is suggested that the lamellar thickness should be well correlated to the PE shell thickness. A two-layer PE model is successfully used to explain the experiment results.     

High Temperature Thermal Gradient Interaction Chromatography (HT-TGIC) for Microstructure Analysis of Polyolefins

Summary: High temperature thermal gradient interaction chromatography (HT-TGIC) is a newly developed technique to analyze comonomer distributions in polyolefins. This paper documents the key differences between crystallization elution fractionation (CEF) and HT-TGIC, and the advantages of using multiple detectors in HT-TGIC to provide comprehensive microstructure characterization. A demonstration of the technique using a specifically designed blend, provides comprehensive data in less than 1.5 hours of analysis time by HT-TGIC. This paper also reports that HT-TGIC has excellent short term repeatability.     

A Comprehensive Review on Controlled Synthesis of Long‐Chain‐Branched Polyolefins: Part 2, Multiple Catalyst Systems and Prepolymer Modification

Long‐chain branching plays an important role in the performance of polyolefins (POs). The existence of a very small amount of long‐chain branches (LCBs), i.e., <1 per 10 000 carbons, can significantly improve processability of the polyolefin materials, which is highly desired for those intractable polyolefins with narrow molecular weight distribution and high degree of crystallinity. Numerous literatures have been published on the controlled synthesis of long‐chain‐branched POs. In the previous paper, the major literatures of single catalyst systems have been summarized. This paper provides a comprehensive review for the binary and multiple catalyst systems and a brief summary of some other methods for the controlled synthesis of long‐chain‐branched POs. The controllability of long‐chain‐branched structures in the various preparation procedures with single or two reactor systems, and in one or two‐step processes, is analyzed and compared in‐depth.

     

呼吸图法制备聚亚甲基-b-聚甲基丙烯酸甲酯多孔薄膜

首先利用叶立德活性聚合和原子转移活性自由基聚合(ATRP)相结合制备了三个不同链段比的聚亚甲基-b-聚甲基丙烯酸甲酯(PM-b-PMMA)两嵌段聚合物. 接着以它们为原料, 利用静态呼吸图方法在四种不同溶剂中制备了一系列的具有蜂窝状表面的多孔薄膜, 用扫描电子显微镜(SEM)观察了多孔薄膜的形貌. 研究了溶剂、溶液浓度、聚合物链段长度及链段比等因素对多孔薄膜表面孔的大小和分布的影响. 结果表明: 当PM_2k-b-PMMA_2k嵌段聚合物浓度为3 wt%、溶剂为二硫化碳(CS₂)和二氯甲烷(CH₂Cl₂)时, 可以通过静态呼吸图方法制备出孔径为纳米级(520 nm)和微米级(1.1 μm)的较为规整的多孔薄膜. 多孔薄膜表面的孔径随PM-b-PMMA浓度的减小而增大|两嵌段聚合物中两个链段的长度及其链段比的变化对多孔膜表面孔径均产生较大的影响.     

Olefins and Vinyl Polar Monomers: Bridging the Gap for Next Generation Materials

The inherent differences in reactivity between activated and non‐activated alkenes prevents copolymerization using established polymer synthesis techniques. Research over the past 20 years has greatly advanced the copolymerization of polar vinyl monomers and olefins. This Review highlights the challenges associated with conventional polymerization systems and evaluates the most relevant methods which have been developed to “bridge the gap” between polar vinyl monomers and olefins. We discuss advancements in heteroatom tolerant coordination–insertion polymerizations, methods of controlling radical polymerizations to incorporate olefinic monomers, as well as combined approaches employing sequential polymerizations. Finally, we discuss state‐of‐the‐art stimuli‐responsive systems capable of facile switching between catalytic pathways and provide an outlook towards applications in which tailored copolymers are ideally suited.     

Unsaturation Characterization of Polyolefins by NMR and Thermal Gradient NMR (TGNMR) with a High Temperature Cryoprobe

Summary: It is important to identify the types of unsaturation and to quantify the amount of unsaturation in polyolefins for understanding chain termination mechanisms of polymerization with different catalysts. Unsaturation is also closely related to processibility, weatherability of polyolefin products and the level of antioxidants to be added for stabilizing purposes. However, it can be very challenging to accurately measure samples with a low level of the unsaturation within a reasonable amount of NMR acquisition time, along with some challenging technical issues, such as dynamic range with ¹H NMR. This paper reports a new method to accurately quantify unsaturation by using multi peak presaturation ¹H NMR with a high temperature NMR cryoprobe. The limit of quantification can be less than 1 unsaturation/1,000,000 carbons with about 30 min NMR acquisition. This paper also introduces a new technique, temperature gradient NMR (TGNMR) with or without substrates, to characterize unsaturation distribution directly in NMR tube upon temperature change.     

高性能锂离子二次电池隔膜

随着电动汽车对锂离子电池功率要求的不断提高, 高性能锂离子电池逐渐成为了人们研究的热点。隔膜作为锂离子电池的关键部件之一, 发挥着隔离正负极材料以及为锂离子迁移提供通道的作用。此外, 隔膜的热稳定性也直接影响着锂离子电池的安全性能。聚烯烃微孔隔膜由于其出色的化学稳定性、机械强度以及价格低廉而被广泛应用于锂离子电池中。然而, 其热稳定性差以及不易湿润等缺点给高性能锂离子电池的广泛应用带来很大隐患。因此, 本文探讨了聚烯烃微孔隔膜的表面改性, 以此为出发点, 介绍了基于聚合物表面改性的聚烯烃微孔隔膜、基于无机纳米颗粒的聚烯烃微孔隔膜、基于有机-无机复合材料的聚烯烃微孔隔膜的研究进展。在基于无机纳米颗粒的聚烯烃微孔隔膜的介绍中, 本文还对原子层沉积法、化学气相沉积法、物理气相沉积法等先进表面改性方法进行了简单介绍。随后, 从湿法制备、相转化法、呼吸图法、静电纺丝法以及原位聚合法5种方法出发, 对其他聚合物微孔隔膜的研究进展进行了介绍。最后, 本文对将来高性能隔膜材料的研究方向上作出展望, 旨在为高性能锂离子二次电池隔膜材料的研究和应用提供参考。     

结构可控的聚亚甲基/聚乳酸嵌段共聚物的合成及其性能研究

报道了一种叶立德活性聚合与开环聚合(ROP)相结合的新型合成方法, 成功地合成了结构可控的聚亚甲基/聚乳酸嵌段共聚物(PM-b-PLA). 首先通过叶立德活性聚合方法合成了含有端羟基的聚亚甲基(PM-OH, M_n＝1800 g•mol^－1, PDI＝1.18), 再以PM-OH为大分子引发剂, 以辛酸亚锡[Sn(Oct)₂]为催化剂, 引发D,L-丙交酯(LA)的开环聚合, 通过核磁共振氢谱(¹H NMR), 凝胶渗透色谱(GPC)和傅里叶变换红外光谱(FT-IR)证明了PM-b-PLA嵌段共聚物的形成|利用示差扫描量热仪(DSC)测试嵌段共聚物的结晶行为, 结果显示, 聚乳酸(PLA)嵌段的引入显著影响了聚亚甲基(PM)的结晶行为|扫描电子显微镜(SEM)观察结果表明: 在低密度聚乙烯(LDPE)/PLA二元共混体系中, PM-b-PLA嵌段共聚物可作为共混相容剂改善LDPE和PLA的界面相容性|PM-b-PLA嵌段共聚物还可通过呼吸图法制备成有序多孔薄膜.     

4-甲基-1-戊烯与烯烃共聚用催化剂的研究进展

4-甲基-1-戊烯(4M1P)是烯烃工业中一种重要的支链α-烯烃,它的主要用途是用于制备均聚物和共聚物。虽然绝大部分4M1P共聚物尚未进入工业化生产阶段,但由于共聚物作为一类新型的合成树脂具有突出的力学性能和光学性能,已成为国外聚烯烃领域的一个研究热点。本文阐述了4M1P与烯烃共聚反应催化剂包括Ziegler-Natta催化剂、茂金属催化剂及后过渡金属催化剂的开发研究现状;重点阐述了催化剂的结构对共聚物分子结构的影响;同时也简要介绍了二亚胺镍催化剂催化4M1P共聚反应作用机理,展望了这一领域的发展趋势。为开发高端聚烯烃新材料提供参考。     

二醚型 Ziegler-Natta 催化剂催化丙烯与极性单体共聚

 以三乙基铝 (TEA) 为保护剂, 研究了 TiCl4/MgCl2/芴二醚/Al(C2H5)3 体系催化丙烯与十一烯醇或十一烯酸的共聚反应. 结果表明, 在极性单体存在下, 聚合反应活性随极性单体加入量的增加而降低, 但可保持丙烯均聚活性的一半以上, 反应活性衰减较小. 同时, 随着极性单体加入量的增加, 极性单体在共聚物中的含量增加. 与十一烯酸相比, 十一烯醇共聚具有更高的共聚活性和共单体含量. 随着共聚物中极性单体含量的增加, 聚合物的熔点和结晶温度都有所降低. 反应温度对丙烯和十一烯醇共聚的反应活性和共单体含量影响较小.