Tetrakis (Triphenyl Phosphite) Nickel (0) as an Initiator of Polymerization at Room Temperature

Bamford, C. H.; Hargreaves, K.

doi:10.1038/209292a0

Cited by 13 publications

(10 citation statements)

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“…Another possibility may be due to some unknown side reactions assisted by Lewis acid. Similar observations were also reported in the literature, ,,,− and these might lead to the higher polydispersity in the resulting polymer. , It is to be noted that the polydispersity of the resulting poly(NIPAM) was decreased with increasing the ratio of chain transfer agent to initiator (Table ).…”

Section: Resultssupporting

confidence: 87%

RAFT Polymerization of N-Isopropylacrylamide in the Absence and Presence of Y(OTf)₃: Simultaneous Control of Molecular Weight and Tacticity

et al. 2004

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The reversible addition−fragmentation chain transfer (RAFT) polymerization of N-isopropylacrylamide (NIPAM) was carried out successfully in the absence and presence of Lewis acid Y(OTf)3 to synthesize controlled molecular weight atactic and isotactic poly(NIPAM)s using both 1-phenylethyl phenyldithioacetate (PEPD) and cumyl phenyldithioacetate (CPDT) as the RAFT agents. The polymerization rate is about 16 times faster in the presence of the Lewis acid than that in the absence and 1.4 times faster with PEPD than with CPDT as the RAFT agent. The polymer with a higher polydispersity was obtained when prepared in the presence of the Lewis acid than that in the absence. A longer induction period was observed using CPDT than PEPD. The chain-end structure of isotactic poly(NIPAM) was determined by 1H NMR and MALDI−TOF mass spectrometry. The RAFT agent derived isotactic poly(NIPAM) was the main product as expected from the well-accepted mechanism of RAFT polymerization. Moreover, a series of stereoblock [atactic(a)-b-isotactic(i)] poly(NIPAM) with different block lengths were synthesized via a one-pot synthesis procedure: synthesis of the atactic block in the absence of the Lewis acid followed by the addition of the Lewis acid to synthesize the isotactic block. The longer is the isotactic block length, the higher is the meso dyad value of the stereoblock polymer as expected. We also successfully synthesized the diblock copolymers, a-poly(NIPAM)-b-polystyrene and i-poly(NIPAM)-b-polystyrene, starting with the atactic and isotactic poly(NIPAM) macro-RAFT agents, respectively.

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Section: Resultssupporting

confidence: 87%

RAFT Polymerization of N-Isopropylacrylamide in the Absence and Presence of Y(OTf)₃: Simultaneous Control of Molecular Weight and Tacticity

et al. 2004

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“…It is also possible that Lewis acids increase the rate of propagation by monomer/radical complexation − and also reduce the rate of exchange by coordination to the dithioester moiety. Similar observations were reported earlier, ,,− and these interactions could result in higher polydispersities of the resulting polymers. , Because the molecular weight distribution of the polymer synthesized in the presence of 0.1 equiv of Y(OTf) 3 (Table , entry 4) was found to be narrower than that for the polymer prepared using 0.1 equiv of Yb(OTf) 3 (Table , entry 5), Y(OTf) 3 was selected for further investigation. The RAFT polymerization was therefore investigated in the presence of a lower amount of Y(OTf) 3 (Lewis acid/monomer = 0.05) (Table , entry 3).…”

Section: Resultsmentioning

confidence: 99%

Stereoblock Copolymers and Tacticity Control in Controlled/Living Radical Polymerization

2003

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Three controlled/living radical polymerization processes, atom transfer radical polymerization (ATRP), reversible addition-fragmentation transfer (RAFT) polymerization, and nitroxide-mediated polymerization (NMP), were investigated for the polymerization of N,N-dimethylacrylamide in the presence of Lewis acids known to enhance isotacticity, such as yttrium trifluoromethanesulfonate (Y(OTf)(3)) and ytterbium trifluoromethanesulfonate (Yb(OTf)(3)). Poly(N,N-dimethylacrylamide) with controlled molecular weight, low polydispersity (M(w)/M(n) < 1.2), and a high proportion of meso dyads ( approximately 85%) was prepared by ATRP (with initiating system methyl 2-chloropropionate/CuCl/Me(6)TREN) and RAFT (with cumyl dithiobenzoate transfer agent) in the presence of Y(OTf)(3). The combination of NMP (using N-tert-butyl-1-diethylphosphono-2,2-dimethylpropyl nitroxide, SG1) and a Lewis acid complexation technique led to less precise control over chain architecture and microstructure ( approximately 65% meso dyads), as compared to RAFT/Y(OTf)(3) or ATRP/Y(OTf)(3). The latter two systems were used for the first one-pot synthesis of stereoblock copolymers by radical polymerization. Well-defined stereoblock copolymers, atactic-b-isotactic poly(N,N-dimethylacrylamides), were obtained by adding Y(OTf)(3) at a given time to either RAFT or ATRP polymerizations, initially started without the presence of the Lewis acid.

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“…in which kp, kt are the velocity coefficients of propagation and total termination, respectively, M represents the monomer and v is the mean kinetic chain length. If chain-transfer is negligible, as in the present system, v is given in terms of the numberaverage degree of polymerization P, by the relation The mean value of kpk;-+ obtained from (4), ( 5 ) is 0.054 mole-*l.*sec-*, in good agreement with previous values for the free radical polymerization of methyl methacrylate at 25OC.179 18 This is further evidence that the polymerization is a freeradical reaction, and also shows that retardation is effectively absent.…”

Section: Resultsmentioning

confidence: 99%

Initiation of polymerization by bis(triphenyl phosphine) nickel dicarbonyl

Bamford¹,

Hargreaves²

1967

Trans. Faraday Soc.

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The initiation of the free-radical polymerization of methyl methacrylate by bis(tripheny1 phosphine) nickel dicarbonyl in association with carbon tetrachloride has been studied in detail at 25°C. A few experiments have also been carried out with ethyl trichloracetate as the halide component. These systems are considerably more active than those involving nickel tetracarbonyl, and, unlike other carbonyl systems studied, do not inhibit at high concentrations.In benzene solution the rate-determining step of the initiation reaction is first order in monomer concentration. The primary process involves the sN2 displacement of a comparatively labile triphenylphosphine ligand by a monomer molecule to form a complex (I), which subsequently reacts with the organic halide giving a free radical capable of initiating polymerization. Addition of triphenylphosphine to the reaction mixture reverses the primary step, thus reducing the rate of initiation. Carbon monoxide also causes inhibition by the deactivation of complex (I). The nature of the initiation proms has been confirmed by experiments designed to measure the evolution of carbon monoxide under a variety of experimental conditions. The activation energy for the primary step is 21.2 kcal mole-1 and the frequency factor has a value close to the normal for a bimolecular reaction.Measurement of polymer yields has shown that a maximum of one free radical is formed for each initiator molecule which decomposes, corresponding to the oxidation NiO -+NiI. Kinetic parameters have been evaluated from equations derived for steady-state relationships.

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Tetrakis (Triphenyl Phosphite) Nickel (0) as an Initiator of Polymerization at Room Temperature

Cited by 13 publications

References 4 publications

RAFT Polymerization of N-Isopropylacrylamide in the Absence and Presence of Y(OTf)₃: Simultaneous Control of Molecular Weight and Tacticity

RAFT Polymerization of N-Isopropylacrylamide in the Absence and Presence of Y(OTf)₃: Simultaneous Control of Molecular Weight and Tacticity

Stereoblock Copolymers and Tacticity Control in Controlled/Living Radical Polymerization

Initiation of polymerization by bis(triphenyl phosphine) nickel dicarbonyl

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Tetrakis (Triphenyl Phosphite) Nickel (0) as an Initiator of Polymerization at Room Temperature

Cited by 13 publications

References 4 publications

RAFT Polymerization of N-Isopropylacrylamide in the Absence and Presence of Y(OTf)3: Simultaneous Control of Molecular Weight and Tacticity

RAFT Polymerization of N-Isopropylacrylamide in the Absence and Presence of Y(OTf)3: Simultaneous Control of Molecular Weight and Tacticity

Stereoblock Copolymers and Tacticity Control in Controlled/Living Radical Polymerization

Initiation of polymerization by bis(triphenyl phosphine) nickel dicarbonyl

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Product

Resources

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RAFT Polymerization of N-Isopropylacrylamide in the Absence and Presence of Y(OTf)₃: Simultaneous Control of Molecular Weight and Tacticity

RAFT Polymerization of N-Isopropylacrylamide in the Absence and Presence of Y(OTf)₃: Simultaneous Control of Molecular Weight and Tacticity