Surface-initiated Atom Transfer Radical Polymerization Of Methyl Methacrylate Research Articles

Insight into the effects of reaction conditions on metal-free surface-initiated atom-transfer radical polymerization of methyl methacrylate from SBA-15

Mesoporous silica nanoparticles/polymer hybrid materials were prepared via metal-free surface-initiated atom-transfer radical polymerization (SI-ATRP). Self-synthesized mesoporous SBA-15 with surface hydroxyl groups was modified with (3-aminopropyl)-triethoxysilane, followed by anchoring of the ATRP initiator α-bromoisobutyryl bromide onto the surface via amide reaction. The SI-ATRP of methyl methacrylate was then carried out with fluorescein (FL) as a photocatalyst and trimethylamine (TEA) as an electron donor under irradiation with blue light. Thus, polymer chains grew directly from mesoporous walls. The hybrid materials were characterized by gel permeation chromatography, N2 adsorption/desorption measurements, and thermogravimetric analysis. The effects of the ligand/photocatalyst molar ratios, solvent, and the monomer/initiator molar ratios on grafting density, molecular weight, and molecular-weight distribution were investigated. The results show that a higher TEA/FL ratio led to a higher reaction rate and better controllability of the polymerization but also to a lower grafting density. These properties were also affected by the solvent. With an increasing monomer/initiator molar ratio, the grafting rate, molecular weight, and grafting density exhibited increasing trends.

Polymer-Brush-Decorated Graphene Oxide: Precision Synthesis and Liquid-Crystal Formation.

Given the specificity of the structure and function of graphene oxide (GO), hybridization with a variety of compounds will further extend its applications. To that end, we examined a new method for introducing a polymer brush onto the GO surface. In this method, GO was surface-modified with 2-((3-((2-bromo-2-methylpropanoyl)oxy)propyl)thio)ethylamine hydrochloride, which is a newly synthesized compound that contains an initiating group for atom transfer radical polymerization (ATRP) and an amino group for reacting with the epoxy groups on the GO surface. The ATRP-initiator-functionalized GO was then used as a substrate for the surface-initiated ATRP of methyl methacrylate (MMA), which produced graft polymers of poly(MMA) (PMMA) with targeted molecular weights and narrow molecular weight distributions; the average graft density was ∼0.06 chains/nm2. Because of their high dispersibilities and structural anisotropies, the PMMA-brush-decorated GOs formed lyotropic liquid crystals in their suspensions. In addition, similar suspensions with relatively high hybrid concentrations exhibited structural color that depended on the concentration.

Preparation of Transparent Bulk TiO2/PMMA Hybrids with Improved Refractive Indices via an in Situ Polymerization Process Using TiO2 Nanoparticles Bearing PMMA Chains Grown by Surface-Initiated Atom Transfer Radical Polymerization.

Transparent TiO2/PMMA hybrids with a thickness of 5 mm and improved refractive indices were prepared by in situ polymerization of methyl methacrylate (MMA) in the presence of TiO2 nanoparticles bearing poly(methyl methacrylate) (PMMA) chains grown using surface-initiated atom transfer radical polymerization (SI-ATRP), and the effect of the chain length of modified PMMA on the dispersibility of modified TiO2 nanoparticles in the bulk hybrids was investigated. The surfaces of TiO2 nanoparticles were modified with both m-(chloromethyl)phenylmethanoyloxymethylphosphonic acid bearing a terminal ATRP initiator and isodecyl phosphate with a high affinity for common organic solvents, leading to sufficient dispersibility of the surface-modified particles in toluene. Subsequently, SI-ATRP of MMA was achieved from the modified surfaces of the TiO2 nanoparticles without aggregation of the nanoparticles in toluene. The molecular weights of the PMMA chains cleaved from the modified TiO2 nanoparticles increased with increases in the prolonging of the polymerization period, and these exhibited a narrow distribution, indicating chain growth controlled by SI-ATRP. The nanoparticles bearing PMMA chains were well-dispersed in MMA regardless of the polymerization period. Bulk PMMA hybrids containing modified TiO2 nanoparticles with a thickness of 5 mm were prepared by in situ polymerization of the MMA dispersion. The transparency of the hybrids depended significantly on the chain length of the modified PMMA on the nanoparticles, because the modified PMMA of low molecular weight induced aggregation of the TiO2 nanoparticles during the in situ polymerization process. The refractive indices of the bulk hybrids could be controlled by adjusting the TiO2 content and could be increased up to 1.566 for 6.3 vol % TiO2 content (1.492 for pristine PMMA).

In situ development of self-reinforced cellulose nanocrystals based thermoplastic elastomers by atom transfer radical polymerization

Recently, the utilization of cellulose nanocrystals (CNCs) as a reinforcing material has received a great attention due to its high elastic modulus. In this article, a novel strategy for the synthesis of self-reinforced CNCs based thermoplastic elastomers (CTPEs) is presented. CNCs were first surface functionalized with an initiator for surface-initiated atom transfer radical polymerization (SI-ATRP). Subsequently, SI-ATRP of methyl methacrylate (MMA) and butyl acrylate (BA) was carried out in the presence of sacrificial initiator to form CTPEs in situ. The CTPEs together with the simple blends of CNCs and linear poly(MMA-co-BA) copolymer (P(MMA-co-BA)) were characterized for comparative study. The results indicated that P(MMA-co-BA) was successfully grafted onto the surface of CNCs and the compatibility between CNCs and the polymer matrix in CTPEs was greatly enhanced. Specially, the CTPEs containing 2.15wt% CNCs increased Tg by 19.2°C and tensile strength by 100% as compared to the linear P(MMA-co-BA).

Synthesis of iron oxide rods coated with polymer brushes and control of their assembly in thin films.

We investigated the surface-initiated atom transfer radical polymerization (SI-ATRP) of methyl methacrylate (MMA) using monodisperse rod-type particles of iron oxide, β-FeOOH. The slow hydrolysis of iron(III) chloride yielded monodisperse β-FeOOH rods with an average length-to-width ratio, L/W, of 6 (L = 210 nm and W = 35 nm on average). The surfaces of the β-FeOOH rods were modified with a triethoxysilane derivative as an ATRP-initiating site, namely, (2-bromo-2-methyl)propionyloxypropyl triethoxysilane. The SI-ATRP of MMA, mediated by a copper complex, was performed using the initiator-coated β-FeOOH rods in the presence of a "sacrificial" free initiator. Well-defined poly(methyl methacrylate) (PMMA) brushes with molecular weights of up to 700,000 could be grafted on the β-FeOOH rods with a surface density as high as 0.3 chains/nm(2). The resultant polymer-brush-afforded hybrid rods exhibited high dispersibility in various solvents for PMMA without forming aggregates. Thin films were prepared by dip-coating from a suspension of the hybrid rods, and the rods were oriented in a specific direction in the films. The arrangement of the rods could be controlled by varying the chain length of the polymer brush and the withdrawal speed during the dip-coating process.

Controlled polymerization of methylmethacrylate from fumed SiO2 nanoparticles through atom transfer radical polymerization

Atom transfer radical polymerization (ATRP) is a promising method to synthesize well-defined polymer/inorganic nanoparticles. However, the surface-initiated ATRP from commercially mass produced inorganic nanoparticles has seldom been studied. In this study, the surface-initiated ATRP of methylmethacrylate (MMA) from commercially mass produced fumed silica (SiO2) nanoparticles was investigated. Unlike the ATRP of MMA initiated from a free initiator, the controllability of ATRP of MMA from the surface of fumed silica nanoparticles was much better using ligand 2,2'-bipyridine (bpy) than N,N,N′,N′′,N′′-pentamethyldiethylenetriamine (PMDETA) as the initiator was immobilized on the surface of the SiO2 nanoparticles and the presence of the SiO2 nanoparticles made the CuCl/bpy catalyst system a homogeneous catalyst system and CuCl/PMDETA a heterogeneous one. The appropriate molar ratio of monomer and initiator was essential for preparing controlled PMMA/SiO2 nanoparticles. The entire process of ATRP of MMA from the surface of SiO2 nanoparticles was controllable when using bpy as ligand, xylene as solvent and with a monomer to initiator ratio of 300:1. The 1H NMR results indicated that the PMMA on the surface of the SiO2 was prepared via ATRP initiated from 4-(chloromethyl)phenyltrimethoxysilane. The well-defined PMMA/SiO2 nanoparticles obtained have good thermal stability and are well dispersed in organic media as proved by TGA, dynamic light scattering and transmission electron microscopy. © 2013 Society of Chemical Industry

Surface-initiated living radical polymerization from silica particles functionalized with poly(ethylene glycol)-carrying initiator

A novel yet versatile approach is described for surface-initiated living radical polymerization (SI-LRP) from silica particles (SiPs). Monodisperse SiPs were surface-modified with a newly designed surface-fixable initiator (BPEGE) having three components: a triethoxysilane moiety, a poly(ethylene glycol) (PEG) unit, and an initiation site for atom transfer radical polymerization (ATRP) in the form of a 2-bromoisobutyryl group. The surface-initiated ATRP of methyl methacrylate (MMA) mediated by a copper complex was carried out with the BPEGE-fixed SiPs. The polymerization proceeded in a living manner, producing SiPs coated with well-defined poly(MMA) of a target molecular weight with a graft density as high as 0.5 chains/nm2. Thanks to the amphiphilic property of PEG, the system was successfully applied for SI-ATRP of PEG methacrylate and sodium p-styrenesulfonate in aqueous media in which the BPEGE-fixed SiPs were highly dispersed without causing any aggregations. The formation of colloidal crystals with the polymer brush-afforded SiPs demonstrated the high uniformity and perfect dispersibility of the hybrid particles.

Synthesis of well-defined polymer brushes on the surface of zinc antimonate nanoparticles through surface-initiated atom transfer radical polymerization

Zinc antimonate nanoparticles consisting of antimony and zinc oxide were surface modified in a methanol solvent medium using triethoxysilane-based atom transfer radical polymerization (ATRP) initiating group (i.e.,) 6-(2-bromo-2-methyl) propionyloxy hexyl triethoxysilane. Successful grafting of ATRP initiator on the surface of nanoparticles was confirmed by thermogravimetric analysis that shows a significant weight loss at around 250-410 °C. Grafting of ATRP initiator onto the surface was further corroborated using Fourier transform Infrared spectroscopy (FT-IR) and X-ray photoelectron spectroscopy (XPS). The surface-initiated ATRP of methyl methacrylate (MMA) mediated by a copper complex was carried out with the initiator-fixed zinc antimonate nanoparticles in the presence of a sacrificial (free) initiator. The polymerization was preceded in a living manner in all examined cases; producing nanoparticles coated with well defined poly(methyl methacrylate) (PMMA) brushes with molecular weight in the range of 35-48K. Furthermore, PMMA-grafted zinc antimonate nanoparticles were characterized using Thermogravimetric analysis (TGA) that exhibit significant weight loss in the temperature range of 300-410 °C confirming the formation of polymer brushes on the surface with the graft density as high as 0.26-0.27 chains/nm 2 . The improvement in the dispersibility of PMMA-grafted zinc antimonate nanoparticles was verified using ultraviolet-visible spectroscopy and transmission electron microscopy.

N-[Salicylidene-1,2-ethanediaminoethyl]-2-bromoisobutyramide as initiator for atom transfer radical polymerization and surface-initiated ATRP of methyl methacrylate on copper

N-[Salicylidene-1,2-ethanediaminoethyl]-2-bromoisobutyramide (SEB) was synthesized and characterized by elemental analysis, FT-IR and 1H NMR. It had been successfully used as a bidentate initiator for the atom transfer radical polymerization (ATRP) of methyl methacrylate with CuBr/2,2′-bipyridine as the catalyst and N,N-dimethylformamide as the solvent at 70 °C. The kinetics was first order in monomer and the number-average molecular weight of the polymer increased linearly with monomer conversion, indicating the ‘living’/controlled nature of the polymerization. The polymerization reached high conversions producing polymers with a low molecular weight distribution (Mw/Mn = 1.34). The obtained poly(methylmethacrylate) (PMMA) functionalized with salicylidene-1,2-ethanediaminoethyl and ω-Br as the end groups were characterized by FT-IR spectroscopy. They can be used as macroinitiators for chain-extension reaction. Then, PMMA coatings were grafted from copper substrates by surface-initiated ATRP from a surface-bound SEB initiator. The electrochemical impedance spectroscopy measurements and potentiodynamic electrochemical experiments confirmed the successful grafting of the polymer coatings. Greatly improved short-term anticorrosive properties for PMMA modified electrodes were demonstrated by substantially increased resistance of the film for a period of 24 h as compared to bare copper.

N-[2-(8-heptadecenyl)-4,5-dihydro-1H-imidazole-1-ethyl]-2-bromoisobutyramide as initiator for atom transfer radical polymerization (ATRP) and surface-initiated ATRP of methyl methacrylate on iron

N-[2-(8-heptadecenyl)-4,5-dihydro-1H-imidazole-1-ethyl]-2-bromoisobutyramide (IEB) was synthesized and characterized by elemental analysis, FT-IR, and 1H NMR. It had been successfully used as a bidentate initiator for the ATRP of methyl methacrylate with CuBr/2,2′-bipyridine as the catalyst, and N,N-dimethylformamide as the solvent at 70 °C. The kinetics was first order in monomer and the number-average molecular weight of the polymer increased linearly with the monomer conversion, indicating the ‘living’/controlled nature of the polymerization. The polymerization reached high conversions producing polymers with a low molecular weight distribution (Mw/Mn = 1.319). The obtained poly(methylmethacrylate) (PMMA) functionalized with 2-(8-heptadecenyl)-4,5-dihydro-1H-imidazoleyl and ω-Br as the end groups were characterized by FT-IR spectroscopy. They can be used as macroinitiators for chain extension reaction. Then, PMMA coatings were grafted from iron substrates by surface-initiated ATRP from a surface-bound IEB initiator. The EIS measurements confirmed the successful grafting of the polymer coatings. Greatly improved short-term anticorrosive properties for PMMA-modified electrodes were demonstrated by substantially increased resistance of the film for a period of 24 h as compared to bare iron.

Monodisperse Silica Particles Grafted with Concentrated Oxetane-Carrying Polymer Brushes: Their Synthesis by Surface-Initiated Atom Transfer Radical Polymerization and Use for Fabrication of Hollow Spheres

An oxetane group-carrying methacrylate, 3-ethyl-3-(methacryloyloxy)methyloxetane (EMO), was polymerized via copper-mediated atom transfer radical polymerization (ATRP) initiated from the surface of monodisperse silica particles (SiPs). The polymerization proceeded in a living manner producing SiPs grafted with well-defined poly(EMO) (PEMO) of target molecular weight up to about 400K with a graft density as high as 0.36 chains/nm2. The surface-initiated ATRP of methyl methacrylate (MMA) with PEMO-grafted SiPs as macroinitiator afforded SiPs grafted with block copolymer of the type PEMO-b-PMMA ((PEMO-b-PMMA)-SiPs). The PEMO layer of (PEMO-b-PMMA)-SiPs, located between the PMMA shell and the SiP core, was cross-linked by cationic ring-opening reaction of the oxetane groups of the EMO moieties. The removal of the SiP core of the cross-linked (PEMO-b-PMMA)-SiPs by HF etching gave polymeric hollow spheres having size uniformity and good dispersibility in organic solvents.

Preparation of Well-Defined Star Polymer from Hyperbranched Macroinitiator Based Attapulgite by Surface-Initiated Atom Transfer Radical Polymerization Technique

To prepare the well-defined star polymer grafted attapulgite nanofibrillar clay (WSP-ATP) with hydrophilic core and hydrophobic shell and higher percentage of grafting, the postgraft polymerization of vinyl polymer from hyperbranched macroinitiator based attapulgite (HMI-ATP) via the surface-initiated atom transfer radical polymerization (SI-ATRP) technique was investigated for the first time. The HMI-ATP, with bromoacetic ester surface groups, was prepared by the bromoacetylation of the surface hydroxyl groups of the hyperbranched aliphatic polyester grafted attapulgite (HAPE-ATP). The HAPE-ATP was prepared by the one-pot polycondensation of the AB2-type monomer 2,2-bis(hydroxymethyl)propionic acid (bis-MPA), from the surfaces of the amino group modified attapulgite nanofibrillar clay (A-ATP) with p-toluenesulfonic acid (p-TSA) as catalyst. Then the SI-ATRP of methyl methacrylate (MMA) was conducted from the HMI-ATP made in the presence of 1,10-phenanthroline and Cu(I)Br as catalyst in toluene. The postg...

Synthesis of Monodisperse Silica Particles Coated with Well-Defined, High-Density Polymer Brushes by Surface-Initiated Atom Transfer Radical Polymerization

Monodisperse silica particles (SiPs) of diameter between 100 and 1500 nm were surface-modified in a mixture of ethanol/water/ammonia with a newly designed triethoxysilane having an atom transfer radical polymerization (ATRP) initiating site, (2-bromo-2-methyl)propionyloxyhexyltriethoxysilane. The surface-initiated ATRP of methyl methacrylate (MMA) mediated by a copper complex was carried out with the initiator-fixed SiPs in the presence of a “sacrificial” (free) initiator. The polymerization proceeded in a living manner in all examined cases, producing SiPs coated with well-defined PMMA of a target molecular weight up to 480K with a graft density as high as 0.65 chains/nm2. These hybrid particles had an exceptionally good dispersibility in organic solvents. Transmission electron microscopic and atomic force microscopic observations of their monolayers prepared at the air−water interface revealed that they formed an ordered 2-dimensional lattice extending throughout the monolayer.

Surface-initiated atom transfer radical polymerization of methyl methacrylate on magnetite nanoparticles

The synthesis of magnetite nanoparticles coated with a well-defined graft polymer is reported. The magnetite nanoparticles with an initiator group for copper-mediated atom transfer radical polymerization (ATRP), 2-(4-chlorosulfonylphenyl) ethyltrichlorosilane (CTCS) chemically bound on their surfaces were prepared by the self-assembled monolayer-deposition method. The surface-initiated ATRP of methyl methacrylate (MMA) was carried out with the CTCS-coated magnetite nanoparticles in the presence of free (sacrificing) initiator, p-toluenesulfonyl chloride. Polymerization proceeded in a living fashion, exhibiting first-order kinetics of monomer consumption and a proportional relationship between molecular weight of the graft polymer and monomer conversion, thus providing well-defined, low-polydispersity graft polymers with an approximate graft density of 0.7 chains/nm 2. The molecular weight and polydispersity of the graft polymer were nearly equal to those of the free polymer produced in the solution, meaning that the free polymer is a good measure of the characteristics of the graft polymer. The graft polymer possessed exceptionally high stability and remarkably improved dispersibility of the magnetite nanoparticles in organic solvent.