TEMPO-mediated Radical Polymerization Research Articles

TEMPO-mediated radical polymerization in the synthesis of poly(methyl methacrylate) macromonomer

A new synthesis of poly(methyl methacrylate) vinylterminated macromonomer is performed using the disproportionation between propagating methyl methacrylate radical and nitroxide TEMPO. The ability of the macromonomer to polymerize and copolymerize with styrene and poly(ethylene glycol) methacrylate was confirmed by GPC and isothermal calorimetry.

Controlled Synthesis of Hyperbranched Polymers by TEMPO-Mediated Radical Polymerization

Controlled Synthesis of Hyperbranched Polymers by TEMPO-Mediated Radical Polymerization

Preparation of polydisperse polystyrene-block-poly(4-vinyl pyridine) synthesized by TEMPO-mediated radical polymerization and the facile nanostructure formation by self-assembly

This article reports a successful nanostructure formation from block copolymer having broad distribution of molecular weight. The block copolymer synthesis and the nanosphere formation are facile; therefore, it is promising for fabrication of nanostructure materials in large-scale manufactory. The polydisperse diblock copolymer of polystyrene-block-poly(4-vinyl pyridine) (PSVP) was prepared by the nitroxide-mediated radical polymerization that contains the fraction of poly(4-vinyl pyridine) block of 45 mol% and the overall polydispersity index of 2.08. The phase separation of PSVP was induced by the simple evaporation of co-solvent DMF:THF (70:30 v/v) of the PSVP solution. The SEM images of the self-assembled polydisperse PSVP display the spherical morphology with the diameter of ~ 50 nm, which is larger than that of block copolymer having narrow molecular weight distribution. By simply immersing the self-assembled film into iron chloride solution, the transformation from the spherical structure to the porous structure occurred directly without sacrificing the block copolymer component indicating the advantage of stimuli-response properties of the self-assembled PSVP. The results demonstrated that the polydisperse block copolymer could be used for the nanostructure formation by simple synthesis and evaporation procedures and, therefore, it is suitable for industrial applications.Graphical

Modeling Insights on the TEMPO Mediated Radical Polymerization of Styrene

Despite a great deal of research on nitroxide mediated radical polymerization (NMRP), its kinetic mechanism is not fully known yet. The focus of this work was to contribute further to the understanding of the kinetics of NMRP processes through refinements of a comprehensive mathematical model developed by our group for the bimolecular system. This work considered important secondary reactions that can occur during the NMRP process. It also analyzed important kinetic aspects via a sensitivity study on some key parameters of the system. It was observed that an irreversible reaction between the TEMPO controller and the chemical initiator is very important and must be considered in the NMRP mechanism, in order to be able to describe properly both conversion and average molecular weight data.

Diblock and Triblock Fluorinated Copolymers: An ARXPS Study

In this contribution we prepared (by TEMPO-mediated radical polymerization) two triblock copolymers (poly(S-b-SF8-b-SP3) and poly(S-b-SP3-b-SF8)) of the A-B-C and A-C-B types composed of hydrophobic styrene (A), hydrophobic/lipophobic fluorinated styrene (B), and hydrophilic PEG-modified styrene (C) polymer blocks with greatly varied degrees of polymerization. A diblock copolymer (poly(S-b-SF8)) was used for comparison. The resulting surface structure and organization of the polymer films were investigated by x-ray photoelectron spectroscopy at different angles (70°, 50°, and 20° being the angle between the analyzer axis and the specimen normal). Besides the wide scan spectra, detailed spectra for the C 1s, F 1s and O 1s regions and related data are presented and discussed. XPS analysis reveals the preferential surface segregation of the phase-separated fluorinated block regardless of the distinctly different macromolecular architectures of the triblock copolymers.

TEMPO-mediated radical polymerization of styrene in aqueous miniemulsion: Macroinitiator concentration effects

The control/livingness in nitroxide-mediated polymerization of styrene (S) in aqueous miniemulsion at 125°C employing a poly(S)-2,2,6,6-tetramethylpiperidinyl-1-oxy (PS-TEMPO) macroinitiator and the surfactant sodium dodecylbenzenesulfonate has been shown to depend strongly on the macroinitiator concentration for particles of approximate number-average diameter 65nm. The control/livingness was relatively poor at [PS-TEMPO]0≤0.02M due to the combined effect of enhanced spontaneous initiation and the interface effect (whereby deactivation is suppressed due to interfacial activity of TEMPO). Satisfactory control/livingness was obtained at higher [PS-TEMPO]0 as a result of the interface effect and enhanced spontaneous initiation exerting less pronounced influence per chain than at lower [PS-TEMPO]0. Polymerizations using the sulfonate surfactant DOWFAX 8390 gave similar results, indicating that the present macroinitiator concentration effects are not specific to SDBS-based systems. The results also demonstrate that TEMPO-mediated polymerization of S in miniemulsion can proceed at a higher rate than in bulk with good control/livingness.

Syntheses of AB 2 3- and AB 4 5-miktoarm star copolymers by combination of the anionic ring-opening polymerization of hexamethylcyclotrisiloxane and nitroxide-mediated radical polymerization of styrene

AB 2 3- and AB 4 5-miktoarm star copolymers were prepared by combination of the anionic ring-opening polymerization (AROP) of hexamethylcyclotrisiloxane (D 3) and the TEMPO-mediated radical polymerization of styrene (St). Initially, two kinds of dendritic multifunctional initiators were prepared. One has a 4-bromobutoxy group and two TEMPO-based alkoxyamines and the other has a 4-bromobutoxy group and four TEMPO-based alkoxyamines. Treatment of the multifunctional initiators with tert-butyllithium gave the corresponding lithiobutoxy derivatives, and AROP of D 3 by the lithiobutoxy derivatives gave poly(D 3) with M w/ M n of 1.07–1.12. Nitroxide-mediated radical polymerization of St by the poly(D 3)s at 120 °C gave AB 2 3- and AB 4 5-miktoarm star copolymers with M w/ M n of 1.15–1.28. Their structures were analyzed by means of 1H NMR and SEC measurements.

Syntheses of 12-arm star polymers and star diblock copolymers by nitroxide-mediated radical polymerization using dendritic dodecafunctional macroinitiators

Dendritic multifunctional macroinitiators having 12 TEMPO-based alkoxyamines were prepared by the reaction of a benzyl alcohol having 4 TEMPO-based alkoxyamines with 1,3,5-tris[(4-chlorocarbonyl)phenyl]benzene and 1,3,5-tris(4-isocyanatophenyl)benzene. Using the dodecafunctional macroinitiators, TEMPO-mediated radical polymerizations of styrene (St) were carried out at 120 °C, and 12-arm star polymers (star-12) with narrow polydispersities of Mw/Mn = 1.06–1.26 were obtained. To evaluate the livingness for the TEMPO-mediated radical polymerizations of St, hydrolysis of the ester bonds of the 12-arm star polymers and subsequent SEC measurements were carried out. Furthermore, using star-12 as the macroinitiator, TEMPO-mediated radical polymerization of 4-vinylpyridine (4-VP) was carried out, and well-defined poly(St)-b-poly(4-VP) 12-arm star diblock copolymers with Mw/Mn = 1.18–1.19 were obtained. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 3689–3700, 2005

Styrene-vinylferrocene random and block copolymers by TEMPO-mediated radical polymerization

Styrene-vinylferrocene random and block copolymers by TEMPO-mediated radical polymerization

Styrene-vinylferrocene random and block copolymers by TEMPO-mediated radical polymerization

TEMPO-mediated free radical polymerization was employed for homo- and copolymerization of vinylferrocene (Vfc). Homopolymerization of Vfc resulted in relatively narrow polydispersities (Mw/Mn = 1.24–1.8), however, molecular weights were limited to 4 800. Copolymerization with styrene afforded random copolymers with molecular weights (Mn) up to 10 000, narrow polydispersity (1.2 > Mw/Mn > 1.4) and up to 42 mol-% Vfc. Block copolymers with PS block and P(S-co-Vfc) block with molecular weights (Mn) in the range of 9 000 to 17 600 (Mw/Mn > 1.3) were also prepared with up to 17 mol-% vinylferrocene. DSC revealed two glass transition temperatures (Tg) evidencing phase separation.