CHINESE JOURNAL OF CHEMISTRY
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2013
·Vol. 31
·期 3
·393-400
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IF 0.917
Anna Zheng,Bo Chen,Dihang Hu,Yong Guan,Dafu Wei,Shuzhao Li,Dandan Ji
This work confirms the new view of the initiation and propagation mechanism of the anionic polymerization previously proposed, based on the investigation of anionic bulk-polymerization of styrene and α -methyl styrene with the help of a self designed microflow device and characterized by GPC and in situ 7 Li NMR. It was found that n -BuLi tended to form the hexameric-aggregated structure and even to form the huge aggregated structure based on the former. These aggregations of initiators could directly initiate the anionic polymerization and form the supramolecule aggregations. The supramolecule aggregations inevitably blocked the diffusion of the monomers to the ion-pairs and resulted in a stationary-conversion platform. Then the aggregators were dissociated completely into equal binary-aggregated species, and the polymerization continued again rapidly before the termination. Tetrahydrofuran (THF) acted as the electron donator, which could push the electron cloud to Li cation and make the aggregated ring of the active species rather loosened and facilitated the monomer to insert in. Therefore, a little THF can greatly promote the anionic polymerization. However, further addition of THF might block the channel between the ion-pairs and decrease the propagation rate. It was also found that the aggregated structure of the active species during the anionic polymerization only depends on the initiator aggregations which were formed before the polymerization.
研究领域:
化学
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高分子科学
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DOI
高影响因子
Journal of Materials Chemistry C
·
2020
·Vol. 8
·期 18
·6025-6033
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IF 7.059
Jiaye Xie,Lei Gao,Jun Hu,Qi Li,Jinliang He
Electrical treeing is regarded as the major factor that results in electrical damage of polymer insulation and thus shortens the lifetime and compromises the reliability of electrical power systems and power electronics. In bulk thermoset polymers, which are widely used as electrical insulation, self-healing of the electrical damage caused by treeing has rarely been reported. In this work, self-healing of electrical damage in a thermoset polymer, i.e., epoxy, is achieved through an anionic polymerization-based microcapsule approach. The epoxy matrix is modified with 2-ethyl-4-methylimidazole that initiates anionic polymerization of the healing agents and thereby repairs the electrical tree channels. The anionic polymerization is designed to be favoured in a moderate temperature range that matches with the working condition of many polymer insulation materials in electrical power systems, eliminating the need of additional stimuli that are usually required to trigger the healing reaction. It is substantialized that the electrical tree channels in the self-healing epoxy are re-built once they encounter and rupture the microcapsules, and the dielectric properties are completely recovered. This design of a self-healing material offers new possibilities for smart dielectrics that are needed in future electrical power systems and power electronics with a longer service lifetime and improved reliability.
研究领域:
材料科学
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电气工程
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DOI
高影响因子
JOURNAL OF POLYMER SCIENCE PART A-POLYMER CHEMISTRY
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2019
·Vol. 57
·期 10
·1130-1139
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IF 2.591
Zheng Li,Jianding Chen,Guijin Zou,Tongyuan Zhang,Dafu Wei,Xiang Xu,Yong Guan,Anna Zheng
In order to break through the bottleneck of anionic polymerization, polar monomers such as methyl methacrylate (MMA), ethyl methacrylate, butyl methacrylate, and hexyl methacrylate are subjected to anionic polymerization at room temperature in tetrahydrofuran (THF) using potassium tert -butoxide ( t -BuOK) as the initiator. The polymerization of alkyl methacrylates is studied by multidetector gel permeation chromatography, proton nuclear magnetic resonance ( 1 H-NMR) and 13 C-NMR spectroscopy, and dynamic laser light scattering. It is found that t -BuOK can initiate the living anionic polymerization of polar alkyl methacrylate, and the polymerization conversion almost reaches up to 100%. t -BuOK exists into two kinds of agglomerates, whose hydrodynamic volumes are 10 and 80 nm, respectively. t -BuOK in THF is similar to emulsion and has a critical active species concentration of about 0.0265 mol L −1 and does not depend on how much t -BuOK is added. After the initiation of the polymerization, the large agglomerates of a loose and less regular structure that have occupied the main part of t -BuOK are greatly reduced, but they do not continue to decrease until they disappear according to the equilibrium theory. Similarly, the active chain after initiation also will not aggregate again. Furthermore, t -BuOK also has an active species with smaller average vibration size between cation and anion pairs, which can only initiate the polymerization of MMA with rather slow rate but cannot initiate other alkyl methacrylates. At last, because t -BuOK can make the dormant species caused by side reactions to be revived, the anionic polymerization of MMA could obtain a high yield. © 2019 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2019 , 57, 1130–1139
研究领域:
高分子化学
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材料科学
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高影响因子
CHIRALITY
·
2015
·Vol. 27
·期 8
·449-453
·
IF 1.886
Wei Hu,Jing Cao,Yi-Ling Huang,Sai Liang
Novel optically active carbon anionic initiators bearing a chiral oxazole substituent on fluorene ring, (S)-1-(9H-fluoren-2-yl)-4-isopropyl-4, 5-dihydrooxazole lithium ((S)-1-FIDD-Li) and (S)-2-(9H-fluoren-2-yl)-4-isopropyl-4, 5-dihydrooxazole lithium ((S)-2-FIDD-Li), were synthesized. Anionic polymerizations of achiral polyisocyanates with the chiral initiators were investigated and optical rotation of the obtained polymers were attributed to asymmetric induction of the chiral initiators. The crowded substituent of initiator ((S)-2-FIDD-Li) seems to reduce the polymerizability of isocyanates and yet enhances the chiral induced ability in polymerization. Chirality 27:449–453, 2015 . © 2015 Wiley Periodicals, Inc.
研究领域:
高分子化学
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有机化学
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DOI
PubMed
高影响因子
CHINESE JOURNAL OF POLYMER SCIENCE
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2019
·Vol. 37
·期 6
·598-603
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IF 2.804
Xia De-Yong,Jiang Qi-Min,Huang Wen-Yan,Yang Hong-Jun,Xue Xiao-Qiang,Jiang Li,Jiang Bi-Biao
The anionic polymerization of methyl methacrylate (MMA) was carried out using phosphazene base t -BuP 4 and ethyl acetate (EA) as the catalyst and the initiator, respectively. Gas chromatography (GC), size exclusion chromatography (SEC) measurements, and nuclear magnetic resonance (NMR) analyses were used to reveal the polymerization mechanism and to confirm the polymer structure. The results confirmed the proposed polymerization mechanism and the polymer structure, while the initiator efficiency was low. Meanwhile, the initiation by methoxy anion coming from hydrolysis of the ester bond in MMA was also observed. As a result, there is a marked deviation between the theoretical molecular weight and the measured molecular weight, and it is essential to carry out the polymerization at excessive dosage of t -BuP 4 for preparing polymers with narrow molecular weight distribution.
研究领域:
高分子化学
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材料科学
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产品关联
DOI
高影响因子
CHINESE CHEMICAL LETTERS
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2014
·
IF 1.178
Ming-Hui He,Mei-Lin Su,Zhao-Hui Yu,Guang-Xue Chen,Zhao-Hua Zeng,Jian-Wen Yang
Benzoylformamide (BFA) derivatives are proposed as new photocaged bases with good solubility in epoxy resin. Initially their structures were confirmed by 1 H NMR, 13 C NMR, and elemental analysis. Next, we detail their thermal stability, solubility behavior, and photolysis products. Furthermore, the model photo-latent anion polymerization (AP) of epoxide system in the presence of BFA-dBA ( N , N -dibenzyl-2-oxo-2-phenylacetamide) as a photocaged base has been investigated, and excellent photopolymerization profile is obtained.
研究领域:
材料科学
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化学
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产品关联
DOI
高影响因子
Polymer Chemistry
·
2017
·Vol. 9
·期 1
·108-120
·
IF 5.375
Lincan Yang,Hongwei Ma,Li Han,Xinyu Hao,Pibo Liu,Heyu Shen,Yang Li
The alkynyl-functionalized 1,1-diphenylethylene (DPE) derivative DPE-yne was incorporated into a polymer chain through living anionic polymerization (LAP). An unanticipated coupling reaction occurred and could be restrained by extra feeding of DPE derivatives. Investigating the mechanism of the side coupling indicated that excess P-SLi coupled with the DPE-yne units in the chain when the feed of DPE-yne was insufficient. Although the use of excess DPE-yne can effectively restrain the side coupling during the copolymerization, these conditions afford only an alternating polymer sequence. For the diversity of sequence structure and multi-functionalization, another DPE derivative, DPE-NMe2, was introduced into the polymerization, and the use of an appropriate amount of DPE-NMe2 effectively inhibited the side coupling. Additionally, two functional groups (alkynes and amines) can be incorporated into polymer chains, and their sequence distribution was investigated. The in situ1H NMR method was applied to monitor the chain propagation during the terpolymerization in real time. The in situ1H NMR results showed that the entire sequence is a gradient structure with compositional drift from a predominant St-(DPE-yne) fraction initially to a St-(DPE-NMe2) fraction finally, and the sequence between them is a gradual transition fraction. Consistent with the special sequence distribution in the polymer chain, the terpolymerization kinetic was investigated, and the apparent kinetic constants for each monomer were obtained. The corresponding reactivity ratios (rSt) were also calculated. The rSt-Dyne and rSt-Dnme were simulated as 0.08 and 5.8 during the terpolymerization, respectively. The terpolymerization investigated here not only inhibited the side coupling reaction but also allowed the introduction of a third functional monomer; moreover, its sequence structure shows potentially novel and intriguing properties that could further the applications of functionalized polymers.
研究领域:
高分子化学
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材料科学
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高影响因子
JOURNAL OF APPLIED POLYMER SCIENCE
·
2022
·Vol. 139
·期 43
·e53061
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IF 3.057
Binglun Gao,Lianwei Sun,Xin Chen,Xiaobo Zhai,Junchi Zheng,Xin Ye,Jianmin Lu,Anchao Feng,Liqun Zhang
The focus of this paper is to report the quantitative synthesis of bis-epoxy end functionalized polyisoprene (BETPI) macromonomers by anionic polymerization and reversible addition fragmentation chain transfer (RAFT) polymerization. For anionic polymerization, more stable and sterically hindered living anions polyisoprene (Li + -PIp-Li + ) react with epichlorohydrin (ECH) for the synthesis of well-defined BETPI. For the high-pressure RAFT polymerization, a novel bis-epoxy end functionalized trithiocarbonate (BODAAT) is designed as RAFT agent for the polymerization of isoprene monomer to obtain well-defined BETPI. The functionalities of the resulting BETPI are analyzed by Fourier transform infrared spectroscopy (FT-IR), NMR, and size exclusion chromatography (SEC). Through two polymerization methods, the BETPI with 600–1000 Da of molecular weight and over 75% of epoxy end capping rate is obtained, which can be further utilized as highly reactive liquid macromonomers.
研究领域:
高分子化学
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材料科学
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产品关联
DOI
高影响因子
APPLIED SURFACE SCIENCE
·
2020
·
IF 6.182
Zhiyan He,Jian Zhao,Feixiang Li,Deli Zhang,Fuhai Guo,Hongge Guo,Xin Wang,Haiqing Hu
Owing to their inherent inertness, covalent functionalization of hexagonal boron nitride nanosheets (BNNSs) proves very difficult, greatly limiting their potential applications. Herein, we report an one-pot in-situ synthesis of polymer-modified boron nitride nanosheets via reductive functionalization. Negatively charged boron nitride nanosheets, generated by a smooth reductive treatment in an electron-rich environment, are directly employed as an initiator to trigger in situ anionic polymerization of methyl methacrylate (MMA) monomers, avoiding the use of complex initiators. The successful grafting of polymethyl methacrylate (PMMA) chains onto BNNS surfaces is evidenced by Fourier transform infrared spectroscopy (FTIR), thermogravimetric analysis (TGA) and X-ray photoelectron spectroscopy (XPS). The functionalized boron nitride nanosheets formed via B-C bonding through this facile “grafting from” method exhibit excellent dispersibility in acetone. When used as a filler, the material shows remarkable mechanical reinforcement for polymeric composites. The reductive charge provides a simple and scalable route for versatile chemical modifications of BNNSs to tailor surface properties of BNNSs , which will find important applications in sensors, catalysis, composite coating, bioimaging and drug delivery etc.
研究领域:
材料科学
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化学工程
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DOI
高影响因子
JOURNAL OF PHYSICAL CHEMISTRY B
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2011
·
IF 3.603
Huan Liu,Zien Fu,Kai Xu,Hualun Cai,Xin Liu,Mingcai Chen
A study of the structure–property relationship of the highly π-conjugated Schiff-base moiety in polymerization of a liquid crystal (LC) diepoxide oligomer (PBMBA) and mesophases stabilization has been investigated. We first proposed two exothermic peaks distinctly observed in nonisothermal polymerization curves for thermal copolymerization of PBMBA monomer with a diamine comonomer that corresponded to two different reactions, namely, an epoxy-amine polymerization and anionic polymerization. For PBMBA, note that an unexpected homopolymerization accompanying an appearance of enantiotropic mesophase transitions had taken place in the absence of any initiators, evidencing the possibility of an anionic mechanism yielding a homopolymer. A novel Schiff-base model compound (SBM) was synthesized and used to induce the polymerization of different types of epoxies. Based on the structure–property relationship, we considered a specific role of highly π-conjugated Schiff-base moieties in the anionic polymerization of PBMBA and hoped the mesophases could be stabilized using this mechanism, which may provide a key strategy for design of the polymer-dispersed liquid crystal (PDLC) materials via a chemical process.
研究领域:
材料化学
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高分子科学
·
液晶材料
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产品关联
DOI
PubMed
高影响因子
Polymer Chemistry
·
2024
·Vol. 15
·期 45
·4637-4649
·
IF 4.1
Guicun Guo,Jiali Wu,Jingwei Zhang,Peng Zhou,Ding Shen,Penghan Li,Guowei Wang
Nano-objects generated via a scalable polymerization-induced self-assembly (PISA) process can serve as organic nanofillers, replacing the widely used inorganic nanofillers in composites. In this contribution, polyisoprene (PI)-b-polystyrene (PS) (PI-b-PS) or PI-b-PS/PS nano-objects were prepared via a living anionic polymerization-induced self-assembly (LAPISA) process or a derived process of living anionic polymerization-induced cooperative assembly (LAPICA) using nonpolar n-heptane as a solvent, which facilitated the control over morphologies and sizes. After the living species in the core region were in situ crosslinked by divinylbenzene (DVB) monomers, stabilized PDVB@(PI-b-PS) or PDVB@(PI-b-PS/PS) nano-objects were generated. After hydroxylated or epoxidized nano-objects were obtained through thiol–ene or epoxidation reactions on the double bonds of the PI stabilizer, the miscibility between the nano-objects and epoxy resin was improved, and the functionalized nano-objects could be introduced into epoxy resin. Differential scanning calorimetry (DSC), thermogravimetric analysis (TGA) and thermomechanical analysis (TMA) results affirmed that the organic nano-objects could improve the thermal properties of the composites, which were obviously superior to commercial inorganic silica nano-objects. In particular, the composites with smaller spherical nano-objects had a higher glass transition temperature (Tg) than those with larger spherical ones or worm-like ones. Transmission electron microscopy (TEM) measurements verified the uniform distribution of organic nano-objects and the formation of sufficiently integrated interfaces between the epoxy resin and nano-objects, thereby improving the thermal properties of the composites.
研究领域:
材料科学
·
化学工程
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DOI
高影响因子
CHEMICAL ENGINEERING JOURNAL
·
2018
·
IF 6.735
Xiangrui Zheng,Zhenhao Xi,Ling Zhao
Living cationic polymerization provides a controllable route to prepare a versatile hybrid biomaterial, poly(dichloro)phosphazene. However, the conversion of this multi-step reaction is limited and the mechanistic understanding of the process is incomplete. Thus, the geometric and energetic properties of three process models were designed to determine the interaction mechanism based on Density Functional Calculations. The internuclear distance among counterions and monomers visually demonstrated that [PCl 6 ] − restricted the reactivity of cationic polymerization through interacting with cationic species. The counterion effect was ascertained to be obvious at the beginning of the propagation on the basis of NBO, frontier molecular orbital and thermodynamic analysis. Besides, solvent effect was quantitatively described and solvents were effective for regulating the negative interaction. Therefore, a rational solvent screening model was established based on the solvent polarity and reactivity of monomers. Selected solvents were carried out to prepare oligomeric dichlorophosphazenes and poly(dichloro)phosphazenes to prove the reliability and practicability of the model, showing a significant improvement in conversion and molecular weight of product with the increase in solvent polarity. The findings of this study will provide new insights into the living cationic polymerization of trichloro(N-silyl)phosphoranimine and will be very relevant for a broader community working on polymerization with rational solvent screening via Density Functional Calculations.
研究领域:
高分子化学
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计算化学
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DOI
高影响因子
危险品化学品经营许可证（带存储）