Multifunctional Macroinitiator Research Articles

Novel Glycopolymer Brushes via ATRP: 1. Synthesis and Characterization

AbstractThe synthesis and characterization of a series of glycopolymer brushes with P(methyl 6‐O‐methacryloyl‐α‐D‐glucoside) (P(6‐O‐MMAGIc)) side chains (SCs) is reported. The formation of well‐defined glycopolymer brushes is confirmed by 1H NMR spectroscopy and size exclusion chromatography (SEC) with a MALLS detector. Four multifunctional macroinitiators with different topologies and molar masses are prepared. The P(6‐O‐MMAGIc) SCs are cleaved from the backbone and analyzed by 1H NMR and SEC–MALLS, which further confirmed the synthesis of well‐defined glycopolymer brushes. The grafting efficiency of P(6‐O‐MMAGIc) from the different macroinitiators are determined to be in the range 0.37 < f < 0.55.

Synthesis of cyclohexanone formaldehyde resin‐methylmethacrylate block‐graft copolymers via ATRP

AbstractWell defined block‐graft copolymers of cyclohexanone‐formaldehyde resin (CFR) and methylmethacrylate (MMA) were prepared via atom transfer radical polymerization (ATRP). In the first step, cyclohexanone formaldehyde resin (CFR) containing hydroxyl groups were modified with 2‐bromopropionyl bromide. Resulting multifunctional macroinitiator was used in the ATRP of MMA using copper bromide (CuBr) and N,N,N′,N″,N″‐pentamethyl‐diethylenetriamine (PMDETA) as catalyst system at 90°C. The chemical composition and structure of the copolymers were characterized by nuclear magnetic resonance (1H‐NMR) spectroscopy, Fourier transform infrared (FTIR) spectroscopy, and molecular weight measurement. Molecular weight distributions of the CFR graft copolymers were measured by gel permeation chromatography (GPC). Mn values up to 19,000 associated with narrow molecular weight distributions (polydispersity index (PDI) < 1.6) were obtained with conversions up to 49%. Coating properties of synthesized graft copolymers such as adhesion and gloss values were measured. They exhibited good adhesion properties on Plexiglas substrate. The thermal behaviors of all polymers were conducted using differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA). © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012

UV generation of a multifunctional hyperbranched thermal crosslinker to cure epoxy resins

A new hyperbranched polymer (HBP) was obtained via an iterative synthetic procedure that consists of esterification and thiol-ene click reaction. This polymer was used as a latent multifunctional macroinitiator for the dual curing of a commercially available cycloaliphatic epoxy resin and this process was studied by photo-DSC and FTIR. The presence of thioether groups in the HBP structure leads, by photoirradiation, to the formation of sulfonium salts, which are thermal cationic initiating species. The materials obtained were characterized by DMTA, TGA, gel content and FESEM. By means of the last technique domains of HBP as a second phase within the epoxy matrix were observed.

Synthesis of Ladder-Like Polysilsesquioxane with Well-Defined Graft Polymers

Well-defined hybrid polymers consisting of organic polymers grafted from inorganic backbone were synthesized by atom transfer radical polymerization (ATRP). Ladder-like structured polysilsesquioxane functioned as both ATRP initiator and hard inorganic backbone, while the organic polymers grafted were hard styrene and soft n-butyl acrylate. Ladder-like structured poly(chloromethylphenylsilsesquioxane) (LCMPSQ) was synthesized using sequential two-step reactions with (ρ-chloromethyl)phenyltrimethxysilane as a monomer in one bath in the presence of K2CO3 as a base catalyst (M w = 6,000). Obtained LCMPSQ was then used as a multi-functional macroinitiator for graft polymerization of styrene (St) or/and n-butyl acrylate (nBA) monomers via ATRP using a CuCl catalyzed system, which gave three types of hybrid graft polymers: poly(styrene-g-silsesquioxane) (PS-g-PSQ), poly(nBA-g-silsesquioxane) (PnBA-g-PSQ) and poly(styrene-ran-nBA-g-silsesquioxane) (PS/nBA-g-PSQ). The hybrid graft polymers were prepared with various organic/inorganic weight fractions by changing the molecular weights of the organic graft polymers, which showed narrow molecular weight distributions (PDI < 1.4) on less than 50% of the polymerization conversion.

Methacrylate copolymers with hydroxyl terminated caprolactone chains via ATRP. A route to grafted copolymers

A series of P(MMA- co-CLMA) copolymers with different ratios of both components were prepared by copolymerization of 6-hydroxyhexanoic acid 2-(2-methacryloyloxy)ethyl ester commercially known as caprolactone 2-(methacryloyloxy)ethyl ester (CLMA) with methyl methacrylate (MMA) via atom transfer radical polymerization (ATRP) using various catalytic and initiating systems. The narrow molecular weight distribution of the resulted functional copolymer containing small amounts of hydroxyl groups was broadened with the content of CLMA. Further, the P(MMA- co-CLMA) after modification was used as the multifunctional macroinitiator for “grafting from” polymerization of MMA. The composition of copolymers was confirmed by proton nuclear magnetic resonance ( 1H NMR) and Fourier transform infrared spectroscopy (FT-IR). Thermal analysis by differential scanning calorimetry (DSC) indicated that the addition of CLMA units into PMMA backbone lowered glass transition temperature ( T g ), whereas later it was increased by the grafting of PMMA side chains.

Hemicellulose-Based Multifunctional Macroinitiator for Single-Electron-Transfer Mediated Living Radical Polymerization

A multifunctional macroinitiator for single-electron-transfer mediated living radical polymerization (SET-LRP) was designed from acetylated galactoglucomannan (AcGGM) by α-bromoisobutyric acid functionalization of the anomeric hydroxyl groups on the heteropolysaccharide backbone. This macroinitiator, with a degree of substitution of 0.15, was used in the SET-LRP of methyl acrylate, catalyzed by Cu(0)/Me(6)-TREN in DMSO, DMF, or DMSO/H(2)O in various concentrations. Kinetic analyses confirm high conversions of up to 99.98% and a living behavior of the SET-LRP process providing high molecular weight hemicelluloses/methyl acrylate hybrid copolymers with a brush-like architecture.

Synthesis of graft copolymers from a linear polyolefin through a combination of coordination polymerization and atom transfer radical polymerization

AbstractThis article reports on a facile route for the preparation of methyl acrylate and methyl methacrylate graft copolymers via a combination of catalytic olefin copolymerization and atom transfer radical polymerization (ATRP). The chemistry first involved a transforming process from ethylene/allylbenzene copolymers to a polyolefin multifunctional macroinitiator with pendant sulfonyl chloride groups. The key to the success of the graft copolymerization was ascribed to a fast exchange rate between the dormant species and active radical species by optimization of the various experimental parameters. Polyolefin‐g‐poly(methyl methacrylate) and polyolefin‐g‐poly(methyl acrylate) graft copolymers with controlled architecture and various graft lengths were, thus, successfully prepared under dilute ATRP conditions. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010

Synthesis, characterization and properties of functional star and dendritic block copolymers of ethylene oxide and glycidol with oligoglycidol branching units

Well-defined, four-arm star block copolymers of ethylene oxide and glycidol were prepared via controlled anionic polymerization using protected glycidol. The length of the poly(ethylene oxide) block was varied from DP = 10 to 50, while the length of the short polyglycidol block remained nearly constant, at DP = 4–6. Star block copolymers with hydroxyl groups at the ends of the arms after conversion to the corresponding alkoxides were used as multifunctional macroinitiators for the sequential polymerization of ethylene oxide and protected glycidol. After deprotection, the branched block copolymers of ethylene oxide and glycidol had narrow molar mass distributions and multiple hydroxyl groups (up to 200) at the peripheries. The structure and functionality were determined using size exclusion chromatography with a light scattering detector and nuclear magnetic resonance spectroscopy. The thermal properties of the synthesized copolymers were also investigated, as well as the hydrophilic dye uptake to the hydrophobic phase containing copolymers.

New Self-Assembling Polyaspartamide-Based Brush Copolymers Obtained by Atom Transfer Radical Polymerization

A simple and efficient method for the synthesis of polyaspartamide-based brush copolymers using Atom Transfer Radical Polymerization (ATRP) is here presented. The syntheses were performed by using two subsequent steps. In the first step the macroinitiator was obtained by the conjugation of a proper number of 2-bromoisobutyryl bromide (BIB) residues to the α,β-poly(N-2-hydroxyethyl)-d,l-aspartamide (PHEA) side chains, obtaining the PHEA−BIB copolymer. PHEA−BIB copolymer was used as “multi-functional macroinitiator” for the polymerization via ATRP of hydrophilic methacrylic monomers, such as methacrylic acid (MA), obtaining PHEA−IB−poly(MA) copolymer, sodium methacrylate (MANa+), obtaining PHEA−IB−poly(MANa+) copolymer, or hydrophobic monomer such as butyl methacrylate (BMA), obtaining PHEA−IB−poly(BMA) copolymer. BMA was also homopolymerized subsequently MANa+ polymerization, extending the poly(MANa+) chains by poly(BMA) chains arising PHEA−IB−poly(MANa+)-block-poly(BMA) copolymer. Different solvent and te...

Functionalized Hyperbranched Polymers via Olefin Metathesis

Hyperbranched polymers are highly branched, three-dimensional macromolecules which are closely related to dendrimers and are typically prepared via a one-pot polycondensation of AB_(n≥2) monomers.^1 Although hyperbranched macromolecules lack the uniformity of monodisperse dendrimers, they still possess many attractive dendritic features such as good solubility, low solution viscosity, globular structure, and multiple end groups.^1-3 Furthermore, the usually inexpensive, one-pot synthesis of these polymers makes them particularly desirable candidates for bulk-material and specialty applications. Toward this end, hyperbranched polymers have been investigated as both rheology-modifying additives to conventional polymers and as substrate-carrying supports or multifunctional macroinitiators, where a large number of functional sites within a compact space becomes beneficial.

Multiple Controlled Graft Copolymers by Transition Metal-Catalyzed Living Radical Polymerization

This study is directed to the synthesis of a series of well-defined graft copolymers with the controlled lengths of both the backbone and graft chains by the ruthenium-catalysed living radical polymerisation. The backbone polymer was first synthesised by the ruthenium-catalysed living radical random copolymerisation of methyl methacrylate and 2-(trimethylsilyloxy)ethyl methacrylate followed by the in-situ transformation of the silyloxyl group into the ester with a C-Br bond, which resulted in efficient multifunctional macroinitiators for living radical graft copolymerisation. The methodology led to the novel controlled architectural copolymers, Ax-BAx-type block-graft copolymers, which can function as new building blocks for controlled nanostructures based on microphase separation and is different from that of the conventional ABA triblock copolymers. A series of well-defined Ax-BAx-type block-graft copolymers consisting of soft middle segments (dodecyl methacrylate) and hard outer graft chains (styrene) were synthesised by the ruthenium-catalysed block and graft polymerisations to exhibit characteristics of a thermoplastic elastomer.

Synthesis of Graft Copolymers by Nitroxide Mediated Radical Polymerization of Styrene and n‐Butylacrylate Using Alkoxyamine‐Functionalized Copolymers as Macroinitiators

AbstractA simple two step method for the preparation of graft copolymers is described in this paper. For the synthesis of the prepolymers the alkoxyaminemonomers 2‐methyl‐acryli‐acid‐4‐[1‐(2,2,6,6‐tetramethyl‐piperidine‐1‐yloxy)ethyl]‐benzylester(Mas‐BzEt‐TEMPO) and 2‐methyl‐acrylic‐acid‐4‐{1‐[N‐tert‐butyl‐N‐(1‐isopropyl‐2‐methyl‐propyl)‐amino‐oxy]ethyl}‐benzylester (Mas‐BzEt‐BIPNO) were utilized in radical copolymerizations with styrene, methylmethacrylate, butylmethacrylate and n‐butylacrylate. These copolymers were then used as multifunctional macroinitiators for nitroxide mediated graft polymerization of styrene and n‐butylacrylate. The polymerizations were carried out in bulk at 125 °C.

Preparation of Well-Defined Core−Shell Particles by Cu2+-Mediated Graft Copolymerization of Methyl Methacrylate from Bovine Serum Albumin

Small well-defined core-shell poly(methyl methacrylate)-bovine serum albumin (PMMA-BSA) particles have been prepared in a direct one-step graft copolymerization of MMA from BSA at 75 degrees C in water with a trace amount of Cu2+ (5 microM). Initially, BSA generates free radicals and acts as a multifunctional macroinitiator, which leads to the formation of an amphiphilic PMMA-BSA grafting copolymer. Such formed copolymer chains act as a polymeric stabilizer to promote further emulsion polymerization of MMA inside, resulting in surfactant-free stable core-shell particles, confirmed by a transmission electron microscopic (TEM) analysis. The PMMA-BSA copolymers as well as PMMA homopolymer inside the particles were isolated by Soxhlet extraction and characterized by Fourier transform infrared spectroscopy (FT-IR) and thermogravimetry (TG). The highest grafting efficiency was approximately 80%. Effects of the reaction temperature, the MMA/BSA ratio, and the concentrations of Cu2+ and BSA on such core-shell particle formation have been systematically studied. Due to their inert PMMA core and biocompatible BSA shell, these small polymer particles are potentially useful in biomedical applications.

Chemoenzymatic Approach toward Heterografted Molecular Bottle Brushes

Heterografted molecular bottle brushes, i.e., poly(glycidol-graft-e-caprolactone-acetyl)-co-(glycidol-graft-methyl methacrylate) [P(G-graft-CLAC)-co-(G-graft-MMA)] and poly(glycidol-graft-e-caprolactone-acetyl)-co-(glycidol-graft-n-butyl methacrylate) [P(G-graft-CLAC)-co-(G-graft-BMA)] were prepared in two steps starting with a linear polyglycidol. In the first step an approximately 50% homografted polymer poly(glycidol-graft-e-caprolactone-acetyl)-co-glycidol [P(G-graft-CLAC)-co-G] was obtained via ring-opening polymerization of e-caprolactone using polyglycidol as a multifunctional macroinitiator and Novozyme 435 (Lipase B from Candida antarctica (CALB) immobilized on a macroporous resin) as a catalyst. Selective acetylation of the hydroxy groups at the graft ends was achieved via enzymatic acetylation with vinyl acetate, and the hydroxy groups at the backbone were acylated with 2-bromo-2-methylpropionyl bromide. Finally poly(methyl methacrylate) or poly(n-butyl methacrylate) grafts were attached by ato...

Synthesis and characterization of 6‐ and 12‐arm star polymers by nitroxide‐mediated radical polymerization of St and MA from dendritic TIPNO‐based hexafunctional and dodecafunctional macroinitiators

AbstractDendritic multifunctional macroinitiators having six and 12 TIPNO‐based alkoxyamines, TIPNO‐6 and TIPNO‐12, were synthesized and used in the living radical polymerization of styrene (St), methyl acrylate (MA), N,N‐dimethylacrylamide (DMAAm), and isoprene (IP). The polymerizations of St initiated with TIPNO‐6 gave 6‐arm star polymers with narrow polydispersities of 1.14–1.18. In the polymerizations of MA initiated with TIPNO‐6 and TIPNO‐12, the influences of added TIPNO on the polydispersity indexes (PDIs) of the resulting star polymers were first investigated, and this led to the successful formation of poly(MA) star polymers with narrow polydispersities (1.10–1.18). Moreover, the polymerizations of DMAAm and IP from TIPNO‐6 in the presence or absence of TIPNO were briefly investigated. The benzyl ether bonds of the poly(St) and poly(MA) star polymers were cleaved by treating with Me3SiI or Pd/C, and the resulting arm's parts were analyzed with SEC. The PDIs of the resulting arm parts were low (1.19–1.23), and the Mns agreed with the Mn,theor, indicating that the poly(St) and poly(MA) star polymers had well‐controlled arms. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 4364–4376, 2007

Syntheses and characterization of 16‐arm star and star diblock copolymer and AB8 9‐miktoarm star copolymer via NMRP and ROP from dendritic multifunctional macroinitiators

AbstractA dendritic macroinitiator having 16 TEMPO‐based alkoxyamines, Star‐16, was prepared by the reaction of a dendritic macroinitiator having eight TEMPO‐based alkoxyamines, [G‐3]‐OH, with 4,4′‐bis(chlorocarbonyl)biphenyl. The nitroxide‐mediated radical polymerization (NMRP) of styrene (St) from Star‐16 gave 16‐arm star polymers with PDI of 1.19–1.47, and NMPR of 4‐vinylpyridine from the 16‐arm star polymer gave 16‐arm star diblock copolymers with PDI of 1.30–1.43. The ring‐opening polymerization of ε‐caprolactone from [G‐3]‐OH and the subsequent NMRP of St gave AB8 9‐miktoarm star copolymers with PDI of 1.30–1.38. The benzyl ether linkages of the 16‐arm star polymers and the AB8 9‐miktoarm star copolymers were cleaved by treating with Me3SiI, and the resultant poly(St) arms were investigated by size exclusion chromatography (SEC). The SEC results showed PDIs of 1.23–1.28 and 1.18–1.22 for the star polymers and miktoarm stars copolymers, respectively, showing that they have well‐controlled poly(St) arms. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 1159–1169, 2007.

Synthesis of Miktoarm Star Polymers via ATRP Using the “In−Out” Method: Determination of Initiation Efficiency of Star Macroinitiators

Miktoarm star polymers were synthesized via atom transfer radical polymerization (ATRP) using the “in−out” method. First, ATRP was applied to the synthesis of star polymers using the “arm-first” method with poly(tert-butyl acrylate) arms and a core formed with divinylbenzene as cross-linker. “Dormant” initiating sites were preserved in the core of the star copolymer, which was then used as a multifunctional macroinitiator (MI) for initiating an ATRP of another monomer to produce the miktoarm star polymer. Because of the congested environment in the star core, not all of the initiating sites participated in the formation of the second generation of arms, and the initiation efficiency (IE) of the star MI was less than 100%. A kinetic method was used for quantitative determination of the IE value of the star MIs. Three factors, including the arm length of star MI, the structural compactness of star MI, and the chemical compatibility of the two kinds of arms on one miktoarm star molecule, have an important effect on the IE of the star MI. It was found that the IE value of the star MI decreased with increasing arm length and structural compactness. When the two arms had the same chemical composition, the star MI had the highest IE value. The IE of the star MI varied from 5% to 54%, depending on the above three factors.

Multiarm star nanocarriers containing a poly(ethylene imine) core and polylactide arms

AbstractStar polymers (SPs) containing a hyperbranched poly(ethylene imine) (PEI; number‐average molecular weight = 10,000) core and polylactide arms were synthesized via the ring‐opening polymerization of lactide. PEI was used as a multifunctional macroinitiator for the ring‐opening polymerization of lactide. Different lactide monomer/amino‐functional group (LA/NHn; n = 1 or 2) ratios were used for preparing SPs with different molecular weights. SPs were able to encapsulate small guest molecules such as Rose Bengal; they also transported small, hydrophilic molecules from water to the organic phase. The transport capacity of all the nanocarriers depended on the LA/NHn ratio used for synthesizing the SPs. Nanocarriers with a higher LA/NHn ratio had higher transport capacities. The size of all the nanocarriers depended on the type of solvent. In chloroform, these nanoparticles had several sizes that were related to the self‐assembly of these nanocarriers, but in acetone, they were monodisperse, and their size was smaller than that in chloroform. Also, the transport of polar dyes from water to the chloroform phase was possible. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 5740–5749, 2006

Ring-Opening Polymerization of ε-Caprolactone by Means of Mono- and Multifunctional Initiators: Comparison of Chemical and Enzymatic Catalysis

Protected polyglycidols with a linear or star-shaped architecture were obtained via anionic ring-opening polymerization of protected glycidol in diglyme with potassium as counterion. Removal of the protecting groups lead to polyglycidols, which were used as multifunctional macroinitiators for the chemically and enzymatically catalyzed ring-opening polymerization of e-caprolactone. For the chemically catalyzed polymerization zinc(II) 2-ethylhexanoate was used, while Novozyme 435 (Lipase B from Candida antarctica immobilized on a macroporous resin) was used for the enzymatically catalyzed polymerization. To determine the characteristics of the two differently catalyzed polymerizations, monofunctional macroinitiators based on poly(ethylene glycol) were applied. The main difference observed was the initiator efficiency, which was explained by the different polymerization mechanism. By using multifunctional macroinitiators the difference in the initiation efficiency lead to different polymer architectures. For...

Synthesis of Dendrimer-Like Polystyrene by Atom Transfer Radical Polymerization and Investigation of Their Viscosity Behavior

The synthesis of dendrimer-like polystyrene (PS) of second and third generations by combination of atom transfer radical polymerization (ATRP) and chain end modifications is reported. Calixarene-based cores were used as initiators for ATRP of styrene yielding star polymers containing precisely 4, 6, or 8 arms. The latter were modified in two steps so as to generate PS stars carrying 8, 12, or 16 terminal bromoisobutyrate groups, respectively. These precursors served as multifunctional macroinitiators for the formation of the second generation of dendrimer-like PS. Reiteration of the aforementioned sequence of reactions allowed to derive dendrimer-like polystyrene of third generation that were constituted of 16, 24, or 32 outer arms, respectively. The chain end modification was monitored by 1H NMR spectroscopy. The dendrimer-like PS were also characterized by size exclusion chromatography equipped with a multiangle laser light scattering detector (SEC/MALLS). The actual polymer architecture and the functio...