Living Polymerization of Isobutylene by Tertiary Alkyl (or Aryl) Methyl Ether/Boron Trichloride Complexes". Organocatalyzed Photocontrolled Radical Polymerization of Semifluorinated (Meth)acrylates Driven by Visible Light. Hyperbranched Polymers by Light-Induced Self-Condensing Vinyl Polymerization. The alkene portion of the molecule is reactive in many ways. Cationic Polymerization: From Photoinitiation to Photocontrol. The obtained materials display the tensile properties of commercial polyolefins but adhere more strongly to polar substrates by an order of magnitude, indicating their promise for next-generation engineering applications. Veronika Kottisch, Michael J. Supej, Brett P. Fors. Common additives are electron donors, salts and proton traps . In Living cationic ring-opening polymerization the monomer is a heterocycle such as an epoxide, THF, an oxazoline or an aziridine such as t-butylaziridine. Vinyl ethers undergo homopolymerization via a cationic mechanism. Honghong Gong, Yucheng Zhao, Xianwang Shen, Jun Lin, Mao Chen. With more polar solvents polyisobutylene solubility becomes a problem. Varun Kumar Singh, Changhoon Yu, Sachin Badgujar, Youngmu Kim, Yonghwan Kwon, Doyon Kim, Junhyeok Lee, Toheed Akhter, Gurunathan Thangavel, Lee Soon Park, Jiseok Lee, Paramjyothi C. Nandajan, Reinhold Wannemacher, Begoña Milián-Medina, Larry Lüer, Kwang S. Kim, Johannes Gierschner, Min Sang Kwon. C Our catalyst-controlled approach to stereoselective cationic polymerization relies on a chiral, BINOL-based counterion to bias the stereochemistry of monomer enchainment. Tianchi Xu, Kai Tu, Jiannan Cheng, Yuanyuan Ni, Lifen Zhang, Zhenping Cheng, Xiulin Zhu. They are increasingly … The resultant isotactic PVEs are semicrystalline thermoplastics with intrinsic polarity. Termination and chain transfer are minimized when the initiator counterion is both non-nucleophilic and non-basic. Please reconnect. The tacticity of vinyl polymers has a profound effect on their physical properties. This polymerization proceeds under mild conditions: a combination of a metal-free photocatalyst, a chain-transfer agent, and light irradiation enables the synthesis of various poly(vinyl ether)s with good control over molecular weight and dispersity as well as excellent chain-end fidelity. Quentin Michaudel, Veronika Kottisch, Brett P. Fors. 24 (8): 933], "A Renaissance in Living Cationic Polymerization", https://en.wikipedia.org/w/index.php?title=Living_cationic_polymerization&oldid=951327447, Creative Commons Attribution-ShareAlike License, This page was last edited on 16 April 2020, at 16:49. Sivaprakash Shanmugam, Jiangtao Xu, Cyrille Boyer. Transfer and termination do occur but in ideal living systems the active ionic propagating species are in chemical equilibrium with the dormant covalent species with an exchange rate much faster than the propagation rate. In particular, the cationic polymerization of 2,4,6-trimethylphenyl vinyl ether proceeded in a living manner under the optimized conditions. Living polymerization is more difficult to achieve because of the ease of termination by nucleophilic attack of a heteroatom in the growing polymer chain. Cansu Aydogan, Mustafa Ciftci, Yusuf Yagci. Fabian Eisenreich, Michael Kathan, Andre Dallmann, Svante P. Ihrig, Timm Schwaar, Bernd M. Schmidt, Stefan Hecht. "Living carbocationic polymerization. A photoswitchable catalyst system for remote-controlled (co)polymerization in situ. Moreover, such a Friedel–Crafts reaction was successfully … VII. Amazing achievements in vinyl ether (VE) chemistry, from the first example of VE polymerization to a plethora of recent research [2-10], facilitated enormous progress in VEs synthesis and in design of advanced polymer materials. Kennedy and Faust studied methylstyrene / boron trichloride polymerization (then called quasi-living) in 1982  and that of isobutylene (system with cumyl acetate, 2,4,4-trimethylpentane-2-acetate and BCl3) in 1984  Initiators are strong electrophiles such as triflic acid. Polymerizations with Diethylaluminium chloride rely on trace amounts of water.  It enables the synthesis of very well defined polymers (low molar mass distribution) and of polymers with unusual architecture such as star polymers and block copolymers and living cationic polymerization is therefore as such of commercial and academic interest. Living isobutylene polymerization typically takes place in a mixed solvent system comprising a non-polar solvent, such as hexane, and a polar solvent, such as chloroform or dichloromethane, at temperatures below 0 °C. In addition, the copolymerization of PhVE with p-methoxybenzaldehyde occurred via vinyl- and carbonyl-addition reactions without Friedel–Crafts reactions, resulting in a polymer with an alternating sequence. Well-Defined High-Molecular-Weight Polyacrylonitrile Formation via Visible-Light-Induced Metal-Free Radical Polymerization. Contact Us 919-843-7100
Co-initiators are boron trichloride, tin tetrachloride and organoaluminum halides. Highly efficient organic photocatalysts discovered via a computer-aided-design strategy for visible-light-driven atom transfer radical polymerization. email@example.com. Solution methods require rigorous purification of monomer and solvent although conditions are not as strict as in anionic polymerization. Tengfei Niu, Jiayu Jiang, Siyuan Li, Bangqing Ni, Xuemin Liu, Mingqing Chen. Mustafa Ciftci, Gorkem Yilmaz, Yusuf Yagci. Despite the well-developed stereoselective methods for the polymerization of propylene and other nonpolar α-olefins, stereoselective polymerization of polar vinyl monomers has proven more challenging. Vinyl ethers (CH2=CHOR, R = methyl, ethyl, isobutyl, benzyl) are very reactive vinyl monomers. Despite the well-developed stereoselective methods for the polymerization of propylene and other nonpolar α-olefins, stereoselective polymerization of polar vinyl monomers has proven more challenging. The tacticity of vinyl polymers has a profound effect on their physical properties. The active electrophile is then a proton and the counter ion the remaining alkoxide which is stabilized by the Lewis acid. Living cationic ring-opening polymerization, Mishra, Munmaya K.; Kennedy, Joseph P. (1987). In the iodine/HI system the electrophile is again a proton and the carbocation is stabilized by the triiodide ion. nucleophiles, Lewis bases) for example dimethylsulfide and dimethylsulfoxide are believed to stabilize the carbocation. 125 The cationic polymerization of vinyl ethers with a … Electron donors (e.g. This mode of reactivity is analogous to the way vinyl acetate and vinyl chloride can be polymerized to form polyvinyl acetate and polyvinyl chloride, respectively. Initiators can be alcohols, halides and ethers. Monomer addition occurs at either face of the oxocarbenium ion. Polar monomers are typically not compatible with this mechanism because of catalyst poisoning.
Common monomers are vinyl ethers, alpha-methyl vinyl ethers, isobutene, styrene, methylstyrene and N-vinylcarbazole. Photochemical regulation of a redox-active olefin polymerization catalyst: controlling polyethylene microstructure with visible light. Poly(vinyl ether)s with a T g as high as 100 °C have been obtained in the living cationic polymerization of vinyl ethers with a bulky tricyclodecane or tricyclodecene unit using HCl/ZnCl 2 in toluene at –30 °C. Et2O” into RAFT radical polymerization to form poly(alkyl vinyl ether)-b-polyvinyl alcohol amphiphiles. Electro-Controlled Living Cationic Polymerization. Intramolecular termination is called backbiting and results in the formation of cyclic oligomers. Department of Chemistry
B The achiral chain end in the cationic polymerizations of vinyl ethers provides no inherent mode for stereoinduction. This approach overrides conventional chain-end stereochemical bias to achieve catalyst-controlled stereoselective polymerization. No person, on the basis of protected status, shall be excluded from participation in, be denied the benefits of, or be subjected to unlawful discrimination, harassment, or retaliation under any University program or activity, including with respect to employment terms and conditions. A The chiral ligand environment in coordination-insertion polymerizations enables stereoselective monomer enchainment by directing facial addition at the propagating polymer chain end. Me, methyl. Journal of Macromolecular Science Part A - Chemistry. More polar solvents promote ion dissociation and hence increase molar mass. It is prone to polymerization, leading to formation of polyvinyl ethers. the Altmetric Attention Score and how the score is calculated. 124 The fast living cationic polymerization of vinyl ethers with SnCl 4 combined with EtAlCl 2 in the presence of an ester as an added base was reported. Campus Box 3290
Vinyl ethers (CH2=CHOR, R = methyl, ethyl, isobutyl, benzyl) are very reactive vinyl monomers. The method was developed starting in the 1970s and 1980s with contributions from Higashimura on the polymerization of p-methoxystyrene using iodine or acetyl perchlorate, on the polymerization of isobutyl vinyl ether by iodine  and with Mitsuo Sawamoto by iodine/HI  and on the formation of p-methoxystyrene - isobutyl vinyl ether block copolymers.. Efficient initiators that resemble the monomer are called cationogens. The basic reaction steps are: Living cationic polymerization is characterised by defined and controlled initiation and propagation while minimizing side-reactions termination and chain transfer. Ion dissociation into free ions lead to non-living polymerization. Enhancing Temporal Control and Enabling Chain‐End Modification in Photoregulated Cationic Polymerizations by Using Iridium‐Based Catalysts.