Factors Affecting Grafting Density in Surface‐Initiated ATRP: A Simulation Study

Mastan, Erlita; Li, Xi; Zhu, Shiping

doi:10.1002/mats.201500081

Cited by 24 publications

(31 citation statements)

References 34 publications

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“…b The values correspond to the termination rate coefficients between two unimers, as reported by Johnston-Hall and Monteiro [ 59 ]. c For simplicity, the nominal values of the elementary rate coefficients for chain initiation and propagation reactions on the surface (

and

) as well as termination reactions between surface-tethered and solution free macrospecies (

and

) adopt the same values as those in the lattice/solution near the surface, based on the work of Zhu and co-workers [ 47 , 48 , 52 , 60 ].…”

Section: Figurementioning

confidence: 99%

“…Here, a sufficiently fast RDRP activation/deactivation (in the brush regime) could alter the local radical concentrations to increase termination rates counteracting the confinement effect. Most stochastic models are in turn based on simplified constant reaction probabilities but allow an explicit positioning of the monomer molecules/units in lattice format, with important contributions based on the 3D bond fluctuation model (BFM) and the dynamic lattice liquid model (DLL) [ 42 , 44 , 49 , 50 , 51 , 52 , 53 , 54 , 55 , 56 ]. Arraez et al [ 15 ] very recently developed so-called matrix-based kinetic Monte Carlo ( k MC) simulations in which BFM is used to represent monomer (unit) positions in 3D but obeying for the first time synthesis time dependent reaction probabilities, as determined by explicitly tracking concentration variations for chains on the surface and in the solution region near that surface.…”

Section: Introductionmentioning

confidence: 99%

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The Competition of Termination and Shielding to Evaluate the Success of Surface-Initiated Reversible Deactivation Radical Polymerization

2020

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One of the challenges for brush synthesis for advanced bioinspired applications using surface-initiated reversible deactivation radical polymerization (SI-RDRP) is the understanding of the relevance of confinement on the reaction probabilities and specifically the role of termination reactions. The present work puts forward a new matrix-based kinetic Monte Carlo platform with an implicit reaction scheme capable of evaluating the growth pattern of individual free and tethered chains in three-dimensional format during SI-RDRP. For illustration purposes, emphasis is on normal SI-atom transfer radical polymerization, introducing concepts such as the apparent livingness and the molecular height distribution (MHD). The former is determined based on the combination of the disturbing impact of termination (related to conventional livingness) and shielding of deactivated species (additional correction due to hindrance), and the latter allows structure-property relationships to be identified, starting at the molecular level in view of future brush characterization. It is shown that under well-defined SI-RDRP conditions the contribution of (shorter) hindered dormant chains is relevant and more pronounced for higher average initiator coverages, despite the fraction of dead chains being less. A dominance of surface-solution termination is also put forward, considering two extreme diffusion modes, i.e., translational and segmental. With the translational mode termination is largely suppressed and the living limit is mimicked, whereas with the segmental mode termination occurs more and the termination front moves upward alongside the polymer layer growth. In any case, bimodalities are established for the tethered chains both on the level of the chain length distribution and the MHD.

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and

) as well as termination reactions between surface-tethered and solution free macrospecies (

and

) adopt the same values as those in the lattice/solution near the surface, based on the work of Zhu and co-workers [ 47 , 48 , 52 , 60 ].…”

Section: Figurementioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

The Competition of Termination and Shielding to Evaluate the Success of Surface-Initiated Reversible Deactivation Radical Polymerization

2020

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“…17 Typically, the grafting density lies between 0.1−0.8 nm −2 , although initiator density can exceed 1 nm −2 . 13b,22,24 Elemental analysis showed ∼1 Br/nm 2 for modified 16 nm silica nanoparticle.…”

mentioning

confidence: 99%

Enhancing Initiation Efficiency in Metal-Free Surface-Initiated Atom Transfer Radical Polymerization (SI-ATRP)

et al. 2016

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Well-defined polymer-inorganic hybrid materials were prepared via metal-free surface-initiated atom transfer radical polymerization (SI-ATRP) with 10-phenylphenothiazine (PhPTZ) as the photocatalyst and 2-bromo-2-phenylacetate initiator tethered to silica surfaces. Initiation efficiency and, hence, graft density were significantly enhanced by this very reactive initiator. The polymerization kinetics, effect of initiator structures, particle sizes, and catalyst concentrations were investigated. Well-defined hybrid particles were prepared at a low catalyst concentration (0.02 mol % or 0.1 mol % to monomer). Poly(methyl methacrylate) (PMMA) with number-average molecular weight of 3.65 × 10 4 , dispersity of 1.43, and graft density of 0.60 chain/ nm 2 was grafted from the surface of silica nanoparticles. The hybrid materials were characterized with size exclusion chromatography (SEC), thermogravimetric analysis (TGA), dynamic light scattering (DLS), and transmission electron microscopy (TEM). I n the past two decades, atom transfer radical polymerization (ATRP) has emerged as one of most versatile and robust methods for preparation of polymers with controlled molecular weight (MW), molecular weight distribution (MWD), architectures, and functionality. 1 However, the use of ATRP metal catalysts, such as copper complexes, results in the presence of an inevitable metal residue in final product. The presence of metal impurities in the products may limit the use of these polymers in electronic and biomedical applications. Extensive research has been carried out on catalyst removal from ATRP products. 2 Indeed, various low-ppm catalyst ATRP methods were developed to avoid time-consuming and costly catalyst removal, including activator regenerated by electron transfer (ARGET) ATRP, 3 use of Cu(0) as supplementary activator and reducing agent (SARA) ATRP, 4 initiators for continuous activator regeneration (ICAR) ATRP, 5 electrochemical ATRP (eATRP), 6 or photoinduced ATRP (photo-ATRP). 7 In addition to copper catalysts, other metal complexes, such as ruthenium, 8 iridium, 9 and iron 10 catalysts were used for ATRP. Although some recent developments utilizing less toxic iron-based catalyst in ATRP improved the biocompatibility of the products, they still have some limitations. 11 Recently reported, a photoinduced metal-free ATRP using an organic catalyst eliminated residual metal in the product. 12 A wide range of monomers, including methacrylates and acrylonitrile were successfully polymerized via metal-free ATRP. A photoexcited 10-phenylphenothiazine (PhPTZ) acted as the activator and the resulting radical cation served as the deactivator, resembling Cu(I) and Cu(II) species in conventional ATRP (Scheme 1).Surface-initiated ATRP (SI-ATRP) is an important synthetic technique for preparation of polymer−inorganic hybrid materials. 13 The development of metal-free techniques eliminates metal impurities from various functional materials prepared via SI-ATRP, including porous carbon for catalysis 14 and porous titania for dye ...

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“…Even in a simple batch reactor of milliliter scale, a wide spectrum of macrospecies with a different composition and/or topology is formed and the level of molecular heterogeneity can significantly alter as a function of reaction time and conditions . For example, polymerization reactions that are on an intrinsic basis sufficiently fast can become prone to diffusional limitations, typically once the reaction mixture becomes too viscous .…”

Section: Introductionmentioning

confidence: 99%

In Silico Tracking of Individual Species Accelerating Progress in Macromolecular Engineering and Design

D’hooge¹

2018

Macromol. Rapid Commun.

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The beneficial use of computer simulations to track the microstructural evolution of individual species is highlighted in view of macromolecular engineering and design, considering two case studies on catalytic polymerization, and both "low" (<100) and "high" (>100) chain lengths, that is, i) atom transfer radical copolymerization of n-butyl acrylate and styrene aiming at the synthesis of functional macrospecies of "identical' chain length; and ii) chain shuttling polymerization of ethylene and 1-octene toward the production of segmented block copolymers with "soft" and "hard" segments. Model parameters are validated and/or tuned based on literature data. The modeling strategy supports the future identification of chemical structure-polymer property relationships and is based on the combination of principles from polymer reaction engineering, chemistry, and physics.

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Factors Affecting Grafting Density in Surface‐Initiated ATRP: A Simulation Study

Cited by 24 publications

References 34 publications

The Competition of Termination and Shielding to Evaluate the Success of Surface-Initiated Reversible Deactivation Radical Polymerization

The Competition of Termination and Shielding to Evaluate the Success of Surface-Initiated Reversible Deactivation Radical Polymerization

Enhancing Initiation Efficiency in Metal-Free Surface-Initiated Atom Transfer Radical Polymerization (SI-ATRP)

In Silico Tracking of Individual Species Accelerating Progress in Macromolecular Engineering and Design

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