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From the journal: Chemical Society Reviews. Externally controlled atom transfer radical polymerization. You have access to this article. Please wait while we load your content Something went wrong.
Try again? Cited by. Back to tab navigation Download options Please wait Article type: Review Article. DOI: Author version available: Download author version PDF. Download Citation: Chem. Externally controlled atom transfer radical polymerization X. Pan, M. Fantin, F. Yuan and K.
Matyjaszewski, Chem. Cyclodextrins CDs have been widely used as substrate-recognition moieties in artificial enzymes [] , which have been used in the hydrolysis of activated esters [] and as phase-transfer catalysts []. Moreover, via complex formation, modern supramolecular catalysts [] have been used to achieve various highly efficient and selective reactions, including hydrolysis reactions [] , C—H bond activation [] , olefin epoxidation [] , Diels—Alder reactions [] , 1,3-dipole cycloadditions [43,44] , and polymerizations [] , among others. Selective substrate recognition and activation are essential functions of supramolecular catalysts.
CD derivatives are widely used in radical polymerization to dissolve hydrophobic monomers in aqueous solutions [] and to control the aggregation of polymers []. Although supramolecular catalysts with CDs as monomer recognition sites and catalytic active sites have been designed for polymerization reactions, relatively few reports have described a catalytic design in which the catalytic active site does not leave the CD monomer recognition site during the growing step.
In a previous design of radical initiators with CDs, the radical-initiating end group leaves the CD monomer recognition site [59,60]. With this molecular design, an included monomer is distant from the radical species and cannot be involved in the direct polymerization.
Here, we will observe the effect of monomer recognition of CD on polymerization if a supramolecular polymerization catalyst capable of inserting the monomer between the active and binding sites can be designed. Based on this concept, we have reported that CDs can include and activate lactones to yield a polymer with a single CD at the end of the polymer chain []. Subsequently, we reported ring-opening metathesis polymerization involving the use of a Ru complex with a CD-derived monophosphine ligand [47].
In the design of the supramolecular polymerization catalysts, monomers are inserted between the initiating end group and the growing polymer chain. In this study, the monomer recognition site is introduced to a reversible addition—fragmentation chain transfer RAFT polymerization system [].
(Co)polymers prepared via free radical mechanism, together with polyolefins, comprise the largest portion of the commodity plastics industry. Provides a concise source of information on synthetic techniques, purification, and characterization methods for free-radical polymers. * Presents information on .
The polymerization rate constant decreased with the addition of competitive molecules, indicating that complexation between CD-CTA and the monomer plays an important role in determining polymerization rate. Prior to studying the polymerization of vinyl monomers, we investigated the complex formation of CDs with vinyl monomers. The X-ray crystallography analysis is important to understand the complex in the condensed phase. The formation of precipitate implied the formation of a host-guest complex between them. One of the disordered pattern of DMA is shown.
Colors of the atoms are based on CPK coloring. DMA, space-filling model; CD, stick model.
As a water-soluble radical initiator, we selected 2,2'-azobis[2- 2-imidazolinyl propane] dihydrochloride VA After 24 hours, the polymer solution was lyophilized. The resulting polymers were dissolved in 8 mL MeOH or chloroform, then reprecipitated into 80 mL diethyl ether. This cycle repeated twice to remove monomer. Some end groups are formed from the VA initiator. Therefore, we chose to utilize a concentration of 0. At regular time intervals, a 0. The conversions were calculated using the ratio between the integral values for the polymer main chain and the vinyl group of the DMA monomer.
The time-conversion plots indicate the induction period in the presence and absence of C 6 diol. Kinetic rates were determined using the least-square method after the induction period.
Language: English. All Journals. Axel H. Nitroxide-mediated polymerization NMP. Once a methyltellanyl radical forms, it activates P—TeMe, giving a polymer end-radical and a ditelluride Scheme 2 , reaction 4.
Figure 3: Time-conversion curves a , kinetic plots b and plots of number-average molecular weight M n ver We studied the radical polymerization of water-soluble vinyl monomers using CD-CTA with molecular recognition property. These results indicate that the chain transfer reagent modified with a host molecule provided the site for a reaction between the end group of the growing polymer and monomers.
Currently, we are investigating the preparation of supramolecular catalysts with a chain transfer reagent with two CDs to recognize monomers and the growing polymer chain, and exploring its function mimicking a biological molecular clamp. Helmut Ritter, Beate E.
Mondrzik, Matthias Rehahn and Markus Gallei. Chinmay A. Shukla and Amol A. Twitter: BeilsteinInst. Beilstein J. Toggle navigation. Please enable Javascript and Cookies to allow this site to work correctly! Kohei Koyanagi. Yoshinori Takashima. Takashi Nakamura. Hiroyasu Yamaguchi.