The group transfer polymerization (GTP) with N-(trimethylsilyl)bis(trifluoromethanesulfonyl)imide (Me3SiNTf2) and 1-methoxy-1-triisopropylsiloxy-2-methyl-1-propene (iPr-SKA) has been studied using methyl acrylate (MA), ethyl acrylate (EA), n-butyl acrylate (nBA), 2-ethylhexyl acrylate (EHA), cyclohexyl acrylate (cHA), dicyclopentanyl acrylate (dcPA), tert-butyl acrylate (tBA), 2-methoxyethyl acrylate (MEA), 2-(2-ethoxyethoxy)ethyl acrylate (EEA), 2-(dimethylamino)ethyl acrylate (DMAEA), allyl acrylate (AlA), propargyl acrylate (PgA), 2-(triisopropylsiloxy)ethyl acrylate (TIPS-HEA), and triisopropylsilyl acrylate (TIPSA). Except for tBA and DMAEA, the GTPs of all other monomers described above proceeded rapidly in a living manner and produced well-defined homo acrylate polymers. The living nature of the GTPs of such acrylate monomers was further applied to the postpolymerizations of MA, EA, nBA, and MEA and also to the sequential GTPs of diverse acrylate monomers for preparing di- and multiblock acrylate polymers. In greater detail, the AB and BA diblock copolymers, (ABC)4 dodecablock terpolymer, (ABCD)3 dodecablock quaterpolymer, and ABCDEF hexablock sestopolymer were synthesized by sequential GTP methods using various acrylate monomers.
The group transfer polymerization (GTP) of nbutyl acrylate (nBA) using hydrosilane (R 3 SiH) and tris-(pentafluorophenyl)borane (B(C 6 F 5 ) 3 ) has been studied, which did not need to use the initiator of a silyl ketene acetal (SKA) as the starting polymerization component. B(C 6 F 5 ) 3 catalyzed the in situ 1,4-hydrosilylation of nBA by R 3 SiH to generate the corresponding SKA prior to the polymerization of nBA, which was confirmed by the 1 H NMR measurement of the model reaction. The formed SKA performed as the initiator for the B(C 6 F 5 ) 3 -catalyzed GTP of nBA leading to well-defined polymers with targeted molar masses and low dispersities. S ilyl ketene acetal (SKA) is widely used as one of the versatile reagents in many organic reactions, such as the Mannich reaction, 1 the Mukaiyama aldol reaction, 2 and the Mukaiyama-Michael reaction, 3 which are important carbon− carbon bond forming reactions. In general, SKAs are synthesized by the reaction of lithium enolates with triorganosilyl chlorides or triflates. 4 Besides, the 1,4-hydrosilylation of an α,β-unsaturated ester using hydrosilane is an alternative method for the synthesis of SKAs. 5 In polymer chemistry, SKA is mainly utilized as an initiator for the group transfer polymerization (GTP) of acrylic monomers, which proceeds through repetitive iterations of Mukaiyama-Michael reaction. 6 GTP is one of the living anionic polymerizations, in which the initial molar ratio of the monomer-to-SKA is decisive to control the molar mass of the obtained polymer. However, SKA is relatively unstable toward moisture and impurities, which causes the difficulty in producing the targeted molar mass, particularly, a high molar mass. Therefore, it is important to improve the GTP method in terms of the initiating and propagating processes.Organocatalysts have been found to be more effective for the controlled/living GTPs through fixing the SKA structures in comparison to a conventional Lewis acid and base. For instance, Taton et al. and Waymouth et al. reported that one of the organic Lewis bases, N-heterocyclic carbene, was versatile for the GTP of acrylates, methacrylates, N,N-dimethylacrylamide, and methacrylonitrile. 7 In addition, Chen et al. reported that the Lewis acid of triphenylmethyl salts, such as triphenylmethyl tetrakis(pentafluorophenyl)borate, realized the living GTPs of methacrylates, acrylates, and butyrolactone-based vinylidene monomers. 8 We also reported the Brønsted acid-catalyzed controlled/living GTPs of acrylate and acrylamide using the triisopropylsilyl ketene acetal and silyl ketene amide, respectively. 9,10 However, these well-controlled GTPs still required the use of conventional or originally designed SKAs. Accordingly, of great interest is to develop a GTP method that does not require the use of SKA as the starting polymerization component. Thus, we aimed to design a new GTP method that (1) SKA is in situ generated by the catalytic 1,4-hydrosilylation of an α,β-unsaturated ester as the monomer with a hydrosilane prior to the polymeriza...
ARTICLEThis journal is © The Royal Society of Chemistry 2015 J. Name., 2015, 00, 1-3 | 1 The group transfer polymerization (GTP) of alkyl methacrylates has been studied using hydrosilane and tris(pentafluorophenyl)borane (B(C 6 F 5 ) 3 ) as the new initiation system. For the B(C 6 F 5 ) 3 -catalyzed polymerization of methyl methacrylate (MMA) using triethylsilane, tri-n-butylsilane (nBu 3 SiH), dimethylphenylsilane (Me 2 PhSiH), triphenylsilane, and triisopropylsilane, nBu 3 SiH and Me 2 PhSiH were suitable for producing well-defined polymers with predicted molar masses and a low polydispersity. The livingness of the GTP of MMA using Me 2 PhSiH/B(C 6 F 5 ) 3 was verified by the matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS) measurement of the resulting polymers, kinetic analyses, and chain extension experiments. The B(C 6 F 5 ) 3 -catalyzed GTP using Me 2 PhSiH was also applicable for other alkyl methacrylates, such as the n-propyl, n-hexyl, n-decyl, 2-ethylhexyl, iso-butyl, and cyclohexyl methacrylates. The in situ formation of the silyl ketene acetal by the 1,4-hydrosilylation of MMA was proved by the MALDI-TOF MS and 2 H NMR measurements of the polymers obtained from the B(C 6 F 5 ) 3 -catalyzed GTPs of MMA with Me 2 PhSiH or Me 2 PhSiD, which was terminated using CH 3 OH or CD 3 OD.
The polyaddition of 4,4′‐bis[(3‐ethyl‐3‐oxetanyl)methoxy]biphenyl (4,4′‐BEOBP) and phenylphosphonic dichloride (PPDC) with quaternary onium salts as catalysts proceeded under mild reaction conditions to afford a polymer containing phosphorous atoms in its main chain. A polyphosphonate with a high number‐average molecular weight (10,300) was obtained by the reaction of 4,4′‐BEOBP and PPDC in the presence of tetraphenylphosphonium chloride (TPPC) in o‐dichlorobenzene at 130 °C for 24 h. The structure of the resulting polymer was confirmed with IR, 1H NMR, and 31P NMR spectroscopy. Furthermore, it was proved that the polyaddition of certain bis(oxetane)s with phosphonic dichlorides proceeded smoothly to give corresponding polyphosphonates with TPPC as the catalyst. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 3835–3846, 2002
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