POLYMER
·
2024
·
IF 4.1
Huimin Xue,Guidong Li,Lifei Liu,Tong Feng,Chun Li,Jiayang Sui,Weizhen Zhao
The stereochemistry of polymethyl methacrylate (PMMA) has a profound influence over its material properties; however, the pursuit of high tacticity in bulk free radical polymerization presents a formidable challenge. Consequently, the procurement of a methodology that facilitates the synthesis of highly tactic polymers during bulk free radical polymerization is both desirable and challenging. In this investigation, the propagation of methyl methacrylate (MMA) within an ionic liquids (ILs) medium was employed via bulk free radical polymerization to harness tacticity. The reactivity of polymerization and the propensity for isotactic polymer formation were potentiated by the incorporation of ILs, specifically 1-octyl-3-methylimidazolium hexafluorophosphate as an additive. The resultant polymer exhibited a triad isotacticity (mm) of 33%, achieved in the presence of a 5 wt% concentration of 1-octyl-3-methylimidazolium hexafluorophosphate. The isotactic selectivity of the ILs appeared to arise from their dynamic interplay with the monomeric or polymer chains, an interaction elucidated by 1 H NMR and DFT analyses. The research imparts critical understanding into the manipulation of PMMA tacticity and presents an enaging prospect for the production of highly tactic polymers via bulk free radical polymerization.
研究领域:
材料科学
·
高分子化学
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产品关联
DOI
高影响因子
MACROMOLECULES
·
2026
·
IF 5.2
Shilong Wu,Xi Zeng,Qi-Lu Yuan,Huanhuan Yang,Wen-Sheng Xu,Quan Chen
This study examines how the segmental and chain dynamics of poly(methyl methacrylate) (PMMA) depend on tacticity. Dielectric response spectroscopy reveals a much stronger β-relaxation peak, more clearly separated from the α-relaxation process at T < Tg, for syndiotactic PMMA (sPMMA) than for isotactic PMMA (iPMMA). Linear viscoelastic measurements show similar rubbery plateaus for sPMMA and iPMMA, suggesting comparable entanglement molecular weights. In contrast, nonlinear extensional rheology exhibits substantially weaker strain hardening in sPMMA than in iPMMA. We propose that locally stiffer and more curved chain conformations in sPMMA reduce packing efficiency at T < Tg, facilitating flipping of planar ester groups that manifests as an enhanced β-relaxation in dielectric response spectroscopy. The same local stiffness probably leads to lower stretchability of the sPMMA chains, thereby leading to the weaker strain hardening at Weissenberg number much higher than one.
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DOI
高影响因子
Materials Science & Engineering C-Materials for Biological Applications
·
2012
·Vol. 32
·期 6
·1699-1703
·
IF 2.686
Jing Ma,Hou Chen,Min Zhang,Chunhua Wang,Ying Zhang,Rongjun Qu
Yb-based catalyst was used for the first time for atom transfer radical polymerization using activators generated by electron transfer (AGET ATRP) of acrylonitrile (AN) with 2-bromopropionitrile (BPN) as initiator, 2, 2′-bipyridine (bipy) as ligand, and tisn(II) bis(2-ethylhexanoate) (Sn(EH) 2 ) as reducing agent in the presence of air. With respect to AGET ATRP of AN catalyzed by CuBr 2 , an evident increase of polymer tacticity was observed for AGET ATRP of AN. The increase of syndiotacticity became more and more pronounced than the increase of isotacticity of polyacrylonitrile (PAN) along with YbBr 3 content. The block copolymer PAN-b-PMMA with molecular weight at 60,000 and polydispersity at 1.36 was successfully prepared.
研究领域:
高分子化学
·
材料科学
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催化化学
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聚合物合成
·
功能材料
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DOI
高影响因子
JOURNAL OF POLYMER SCIENCE PART A-POLYMER CHEMISTRY
·
2011
·Vol. 49
·期 13
·2924-2930
·
IF 3.894
Hou Chen,Guangxi Zong,Lingfang Chen,Min Zhang,Chunhua Wang,Rongjun Qu
Samarium powder was applied as a catalyst for single electron transfer-living radical polymerization (SET-LRP) of acrylonitrile (AN) in 1,1,1,3,3,3-hexafluoro-2-propanol (HFIP) with 2-bromopropionitrile as initiator and N,N,N ′ ,N ′-tetramethylethylenediamine as ligand. First-order kinetics of polymerization with respect to the monomer concentration, linear increase of the molecular weight with monomer conversion, and the highly syndiotactic polyacrylonitrile (PAN) obtained indicate that the SET-LRP of AN could simultaneously control molecular weight and tacticity of PAN. An increase in syndiotacticity of PAN obtained in HFIP was observed compared with that obtained by SET-LRP in N,-N -dimethylformamide (DMF). The syndiotacticity markedly increased with the HFIP volume. The syndiotacticity of PAN prepared by SET-LRP of AN using Sm powder as catalyst in DMF was higher than that prepared with Cu powder as catalyst. The increase in syndiotacticity of PAN with Sm content was more pronounced than the increase in its isotacticity. The block copolymer PAN- b -polymethyl methacrylate (52,310 molecular weight and 1.34 polydispersity) was successfully prepared. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011
研究领域:
高分子化学
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材料科学
·
有机合成
·
催化化学
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DOI
高影响因子
危险品化学品经营许可证（带存储）