Transfer Radical Polymerization Research Articles

Poly(vinylphosphonate)s as Macromolecular Flame Retardants for Polycarbonate

A series of poly(dialkyl vinylphosphonate)s (PDAVPs) have recently been reported to be available via rare earth metal-mediated group transfer polymerization (REM-GTP). We extend the existing portfolio of polyvinylphosphonates (PVPs) by presenting poly(ditolyl vinylphosphonate) (PDTVP) as the first example of a poly(diaryl vinylphosphonate) (PDArVP). Thermogravimetric analyses revealed that, for PDTVP, in contrast to the selected PDAVPs, side group cleavage does not occur. Instead, thermal decomposition takes place in a one-step mechanism at high temperatures above 350 °C. A series of PDAVPs and PDTVP were tested for their performance as flame-retardant additives (FRA) as well as flame-retardant coatings (FRC) for polycarbonate (PC). We thereby found that PDTVP is a promising FRA, because of its high thermal stability and its compatibility with polycarbonate. Poly(diisopropyl vinylphosphonate) (PDIVP) shows excellent performance as an FRC, because it forms a stable, blistered crust of poly(vinylphosphonic ...

C–H Bond Activation by σ-Bond Metathesis as a Versatile Route toward Highly Efficient Initiators for the Catalytic Precision Polymerization of Polar Monomers

Rare earth metals show high activities toward C–H bond activation of heteroaromatic substrates and even methane. In this work, we demonstrate the suitability of this synthetic approach to rare earth metallocenes and show the applicability of the resulting complexes as highly efficient initiators for rare earth metal-mediated group transfer polymerization. Bis(cyclopentadienyl)(4,6-dimethylpyridin-2-yl)methyl lanthanide complexes exhibit unprecedented initiation rates for rare earth metal-mediated dialkyl vinylphosphonate polymerization and facilitate an efficient initiation for a broad scope of Michael acceptor-type monomers.

Synthesis of Homopolymers, Diblock Copolymers, and Multiblock Polymers by Organocatalyzed Group Transfer Polymerization of Various Acrylate Monomers

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 p...

Stereospecific catalytic precision polymerization of 2-vinylpyridine via rare earth metal-mediated group transfer polymerization with 2-methoxyethylamino-bis(phenolate)-yttrium complexes

C 1-Symmetric 2-methoxyethylamino-bis(phenolate)-yttrium complexes for the stereospecific polymerization of 2-vinylpyridine.

Synthesis of AB block and A2B2 and A3B3 miktoarm star-shaped copolymers using ω-end-functionalized poly(methyl methacrylate) with a hydroxyl group prepared by organocatalyzed group transfer polymerization

The metal-free synthesis of an AB block copolymer, and A2B2 and A3B3 type miktoarm star-shaped copolymers consisting of PMMA and PDLA arms was achieved.

Synthesis of end-functionalized poly(methyl methacrylate) by organocatalyzed group transfer polymerization using functional silyl ketene acetals and α-phenylacrylates

The α and ω-end-functionalization of PMMA by organocatalyzed GTP was achieved using functional silyl ketene acetals and α-phenylacrylates.

Organic acids as efficient catalysts for group transfer polymerization of N,N-disubstituted acrylamide with silyl ketene acetal: polymerization mechanism and synthesis of diblock copolymers

The GTP of N,N-disubstituted acrylamide using organic acid and silyl ketene acetal was intensively investigated.

B(C6F5)3-catalyzed group transfer polymerization of alkyl methacrylates with dimethylphenylsilane through in situ formation of silyl ketene acetal by B(C6F5)3-catalyzed 1,4-hydrosilylation of methacrylate monomer

The B(C6F5)3-catalyzed GTP of alkyl methacrylates using hydrosilane has been studied in this study.

Visible light-induced surface initiated atom transfer radical polymerization of methyl methacrylate on titania/reduced graphene oxide nanocomposite

Visible light assisted copper catalyzed surface initiated atom radical transfer polymerization system for polymer growth from titania/reduced graphene oxide (TiO2/rGO) has been described.

Surface-Initiated Group-Transfer Polymerization – A Catalytic Approach to Stimuli-Responsive Silicon Nanocrystal Hybrid Materials

ABSTRACTSilicon nanocrystals are photoluminescent materials with a tremendous scope in various niche applications especially the generation of hybrid materials. Our approach for the preparation of stimuli responsive SiNC hybrid materials is based on the application of surface-initiated group-transfer polymerization. As a first step we used photografting of ethyleneglycol di(methacrylate). Then we impregnated remaining methyl acrylic surface groups with the catalyst Cp2YCH2TMS(thf). We performed polymerization studies regarding catalyst and diethyl vinylphosphonate (DEVP) concentrations, highlighting that surface grafting is dependent upon catalyst concentration and independent from added monomer amount. Furthermore, we successfully polymerized methyl methacrylate, dimethyl vinylphosphonate and diisopropyl vinylphosphonate from the SiNC surface.

Versatile 2-Methoxyethylaminobis(phenolate)yttrium Catalysts: Catalytic Precision Polymerization of Polar Monomers via Rare Earth Metal-Mediated Group Transfer Polymerization

The present study is one of the first examples for rare earth metal-mediated group transfer polymerization (REM-GTP) with non-metallocene catalyst systems. 2-Methoxyethylaminobis(phenolate)yttrium trimethylsilylmethyl complexes were synthesized and showed moderate to high activities in the rare earth metal-mediated group transfer polymerizations of 2-vinylpyridine, 2-isopropenyl-2-oxazoline, diethyl vinylphosphonate, diisopropyl vinylphosphonate, and N,N-dimethylacrylamide as well as in the ring-opening polymerization of β-butyrolactone. Reaction orders in catalyst and monomer were determined for the REM-GTP of 2-vinylpyridine. The mechanistic studies revealed that the catalyst systems follow a living monometallic group transfer polymerization mechanism allowing a precise molecular-weight control of the homopolymers and the block copolymers with very narrow molecular weight distributions. Temperature-dependent reaction kinetics were conducted and allowed conclusions about the influence of the bulky substituents around the metal center on the polymerization activity. Additional polymerization experiments concerning the combination of REM-GTP and ROP to obtain block copolymers were performed.

B(C6F5)3-Catalyzed Group Transfer Polymerization of n-Butyl Acrylate with Hydrosilane through In Situ Formation of Initiator by 1,4-Hydrosilylation of n-Butyl Acrylate.

The group transfer polymerization (GTP) of n-butyl acrylate (nBA) using hydrosilane (R3SiH) and tris(pentafluorophenyl)borane (B(C6F5)3) has been studied, which did not need to use the initiator of a silyl ketene acetal (SKA) as the starting polymerization component. B(C6F5)3 catalyzed the in situ 1,4-hydrosilylation of nBA by R3SiH to generate the corresponding SKA prior to the polymerization of nBA, which was confirmed by the 1H NMR measurement of the model reaction. The formed SKA performed as the initiator for the B(C6F5)3-catalyzed GTP of nBA leading to well-defined polymers with targeted molar masses and low dispersities.

Thermoresponsive and photoluminescent hybrid silicon nanoparticles by surface-initiated group transfer polymerization of diethyl vinylphosphonate.

We present a method to combine the functional features of poly(diethyl vinylphosphonate) (PDEVP) and photoluminescent silicon nanocrystals. The polymer-particle hybrids were synthesized in three steps through surface-initiated group transfer polymerization using Cp2 YCH2 TMS(thf) as a catalyst. This pathway of particle modification renders the nanoparticle surface stable against oxidation. Although SiNC properties are known to be sensitive toward transition metals, the hybrid particles exhibit red photoluminescence in water. The temperature-dependent coiling of PDEVP results in a change of the hydrodynamic radius of the hybrid particles in water. To the best of our knowledge, this is the first example of controlled catalytic polymerization reactions on a silicon nanocrystal surface.

Thermoresponsive and Photoluminescent Hybrid Silicon Nanoparticles by Surface‐Initiated Group Transfer Polymerization of Diethyl Vinylphosphonate

AbstractWe present a method to combine the functional features of poly(diethyl vinylphosphonate) (PDEVP) and photoluminescent silicon nanocrystals. The polymer–particle hybrids were synthesized in three steps through surface‐initiated group transfer polymerization using Cp2YCH2TMS(thf) as a catalyst. This pathway of particle modification renders the nanoparticle surface stable against oxidation. Although SiNC properties are known to be sensitive toward transition metals, the hybrid particles exhibit red photoluminescence in water. The temperature‐dependent coiling of PDEVP results in a change of the hydrodynamic radius of the hybrid particles in water. To the best of our knowledge, this is the first example of controlled catalytic polymerization reactions on a silicon nanocrystal surface.

One-Pot synthesis of functional poly(methacrylate) by ATRP and 1,8-Diazacyclo-[5,4,0]undec-7-ene catalyzed transesterification

A facile one-pot 1,8-diazacyclo-[5,4,0]undec-7-ene (DBU) catalyzed transesterification/atom transfer radical polymerization (ATRP) strategy has been successfully developed through the combination of copper/DBU-catalyzed ATRP and DBU-catalyzed transesterification reactions. Well-defined poly(methacrylate)s with various side ester groups have been synthesized by ATRP and transesterification of acyl donor 2,2,2-trifluoethyl methacrylate with various alcohols, such as benzyl alcohol, n-butanol, iso-propyl alcohol, methanol, triethylene glycol monomethyl ether, propargyl alcohol, and 6-azido-1-hexanol by the one-pot process. Kinetic studies indicate that the ATRP process proceeded in a controllable manner without the interference of the transesterification reactions. Expansion of the binary system to a higher level ternary system has been successfully achieved by the combination of copper(I)-catalyzed azide–alkyne cycloaddition, transesterification, and ATRP reactions. © 2014 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2014, 52, 2998–3003

Catalytic Precision Polymerization: Rare Earth Metal‐Mediated Synthesis of Homopolymers, Block Copolymers, and Polymer Brushes

Recent studies have shown that rare earth metal‐mediated group transfer polymerization (REM‐GTP) can be applied to a variety of polar monomers, besides the classic (meth)­acrylates or (meth)acrylamides, giving access to new polymeric materials. This article highlights progress in this new field and gives a current overview of the initiation and propagation of vinylphosphonates, the extension to Michael‐type nitrogen‐coordinating monomers, and application to block copolymers, statistical copolymers, and 2D and 3D structures. Based on molecular understanding and high‐precision synthesis, REM‐GTP represents a versatile method for the preparation of new materials. image

Single-Chain Folding of Diblock Copolymers Driven by Orthogonal H-Donor and Acceptor Units

We report the precision single-chain folding of narrow dispersity diblock copolymers via pairwise orthogonal multiple hydrogen bonding motifs and single chain selected point folding. Well-defined linear polystyrene (PS) and poly(n-butyl acrylate) (PnBA) carrying complementary recognition units have been synthesized via activators regenerated by electron transfer/atom transfer radical polymerization (ARGET ATRP) utilizing functional initiators yielding molecular weights of Mn,SEC = 10900 Da, Đ = 1.09 and Mn,SEC = 3900 Da, Đ = 1.10, respectively. The orthogonal hydrogen bonding recognition motifs were incorporated into the polymer chain ends of the respective building blocks (to yield an eight shaped single chain folded polymers). Diblock copolymer formation was achieved via the Cu(I) catalyzed azide–alkyne cycloaddition (CuAAC) reaction, while the single-chain folding of the prepared linear diblock copolymer–at low concentrations–was driven by orthogonal multiple hydrogen bonds via three-point thymine–diam...

Synthesis of α-, ω-, and α,ω-End-Functionalized Poly(n-butyl acrylate)s by Organocatalytic Group Transfer Polymerization Using Functional Initiator and Terminator

The α-functionalized (hydroxyl, ethynyl, vinyl, and norbornenyl), ω-functionalized (ethynyl, vinyl, hydroxyl, and bromo), and α,ω-functionalized polyacrylates were precisely synthesized by the N-(trimethylsilyl)bis(trifluoroethanesulfonyl)imide (Me3SiNTf2)-catalyzed group transfer polymerization (GTP) of n-butyl acrylate (nBA). The α-functionalization and ω-functionalization were carried out using the functional triisopropylsilyl ketene acetal as the initiator (initiation approach) and 2-phenyl acrylate derivatives as the terminator (termination approach) for the organocatalytic GTP, respectively. All the polymerizations precisely occurred and produced well-defined end-functionalized poly(n-butyl acrylate)s which had predictable molecular weights and narrow molecular weight distributions. High-molecular-weight polyacrylates were easily synthesized using both approaches. In addition, the α,ω-functionalized (hetero)telechelic polyacrylates were synthesized by the combination of the initiation and termination approaches. The structure of the obtained polyacrylates and degree of functionalization were confirmed by the 1H NMR and matrix-assisted laser desorption/ionization time-of-flight mass spectroscopy (MALDI-TOF MS) measurements. The spectra of the 1H NMR and MALDI-TOF MS showed that the end-functionalization quantitatively proceeded without any side reactions.

Poly(vinylphosphonate)s functionalized polymer microspheres via rare earth metal-mediated group transfer polymerization

We demonstrate a facile, yet efficient method for the functionalization of crosslinked polystyrene (PS) microspheres with biocompatible poly(vinylphosphonate)s via the combination of a UV grafting polymerization and a surface-initiated group transfer polymerization. Self-initiated photografting and photopolymerization of ethylene glycol dimethacrylate results in direct photografting of poly(ethylene glycol dimethacrylate) on the PS microspheres with dangling methacrylate functionalities, which are used to immobilize ytterbocene complexes to form the surface-bound rare-earth metal catalyst system. The surface-initiated GTP of dialkyl vinylphosphonates from the initiator system leads to the functionalization of PS microspheres with poly(vinylphosphonate) brushes. Polymerization kinetic investigation indicates that surface-initiated GTP leads to a constant and remarkably rapid weight gain of the microsphere (a microsphere weight increase of 600% within 3 min), owing to the highly living and efficient character of GTP. The surface-initiated GTP occurring inside the microsphere causes an accumulation of the tension between the polymer chains in the microsphere, which eventually induces fracture of the microsphere for longer polymerization time. © 2014 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2014, 52, 2919–2925

Plasma‐brominated cyclo‐olefin polymer slides: Suitable macroinitiators for activator regenerated by electron transfer/atom radical transfer polymerization

ABSTRACTActivators regenerated by electron transfer–atom radical transfer polymerization (ATRP) as a controlled living polymerization are distinguished by their acceptance of small amounts of transition‐metal complexes and oxygen and by their tolerance of reducing agents at a high concentration. The precondition of all ATRP applications is the use of homolytic or heterolytic cleavable halides as a dormant species; this allows the propagation of monomer chains. Hence, alkyl bromides are slightly cleavable and are the preferred initiators for ATRP. The bromination of polymer slides used as macroinitiators was carried out under gentle bromoform plasma conditions. This led to an oxidation‐resistant stable bromine layer. More than 20 bromines per 100 carbons on the polymer scaffold were permanently bound to the substrate after plasma treatment. The resulting amounts of secondary and tertiary bromines on the polymer scaffold exhibited a suitable macroinitiator concentration for the surface‐initiated polymerization of methyl methacrylate and glycidyl methacrylate. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014, 131, 40662.