PEO Macromonomer Research Articles

Folding and Unfolding of Individual PNIPAM-g-PEO Copolymer Chains in Dilute Aqueous Solutions

Linear poly(N-isopropylacrylamide) chains grafted with different contents of short poly(ethylene oxide) branching chains (PNIPAM-g-PEO) were prepared by free radical copolymerization of NIPAM and PEO macromonomers (Mw = 5000 g/mol) end-capped with methacrylate in water at 45 °C, higher than the lower critical solution temperature (∼32 °C) of PNIPAM homopolymer. As expected, the copolymerization led to a heterogeneous distribution of PEO on the chain backbone because PNIPAM becomes hydrophobic and fully collapsed at 45 °C. Both the folding and unfolding of individual PNIPAM-g-PEO chains in extremely dilute aqueous solutions were investigated by a combination of static and dynamic laser light scattering (LLS). Our results showed that each copolymer chain could indeed fold into a globule without any interchain association when the solution was heated from 25 to 50 °C, resulting in a core−shell nanostructure with a collapsed PNIPAM core and a swollen PEO shell. The folding of the copolymer chains with a higher PEO content involves two transitions; namely, one sharp transition at ∼33 °C and another broader one around ∼45 °C. Such two transitions also occurred in the cooling (unfolding) process. The second transition gradually disappears when we lower the PEO content. A combination of LLS and micro-differential scanning calorimetric results suggests that the first transition is related to the collapse of the PNIPAM segment between two grafted PEO chains. The second one at higher temperatures is related to the steric repulsion-induced stretching and the n-clustering-induced collapse of the hydrophilic PEO chains on the periphery of the collapsed PNIPAM core.

Novel Brush Copolymers via Controlled Radical Polymerization

AbstractSummary: A combination of reversible addition‐fragmentation chain transfer (RAFT) polymerization and atom transfer radical polymerization (ATRP) techniques were applied for the synthesis of novel polymer brushes by using the “grafting from” approach or a combination of “grafting through” and “grafting from” methods. The procedure included the following steps: (1) Synthesis of 2‐(2‐bromoisobutyryloxy)ethyl methacrylate (BIEM), (2a) RAFT homopolymerization of BIEM to obtain PBIEM as the polymer backbone. (2b) RAFT copolymerization of BIEM and PEO macromonomer (PEOMA, $\overline M _{\rm w}$ = 450 g · mol−1, $\overline {DP} _{{\rm PEO}}$ = 9) to obtain a more hydrophilic polymer backbone. Well‐controlled copolymers containing almost 25 mol‐% of PEOMA were obtained, and (3) ATRP homopolymerization of methyl acrylate (MA) and copolymerization of MA with 1‐octene using both PBIEM homopolymer and poly(BIEM‐co‐PEOMA) as polyinitiators resulted in brushes with densely grafted homopolymer and copolymer side chains, respectively. Well‐controlled copolymer side chains containing 15 mol‐% of 1‐octene were obtained. Relatively narrow molar mass distributions (MMD) were obtained for the ATRP experiments. The formation of the side chains was monitored using size exclusion chromatography (SEC) and NMR spectroscopy. The copolymer composition in the side chain was confirmed using 1H NMR spectroscopy. Contact angle measurements indicated that for the brush polymers, containing 1‐octene in the side chain, there was a decrease in the surface energy, as compared with the brush polymers containing only the homopolymer of MA in the side chain.Tapping‐mode SFM images for the poly(BIEM)‐graft‐poly(MA‐co‐octene) brush polymer, dip coated from dilute THF solution on mica.magnified imageTapping‐mode SFM images for the poly(BIEM)‐graft‐poly(MA‐co‐octene) brush polymer, dip coated from dilute THF solution on mica.

Copolymerization of the macromonomer poly(ethylene oxide) with styryl end group and styrene in the presence of poly(ε‐caprolactone) with 2,2,6,6‐tetramethylpiperidinyl‐1‐oxy end group by controlled radical mechanism

AbstractA copolymerization of macromonomer poly(ethylene oxide) (PEO) with a styryl end group (PEOS) and styrene was successfully carried out in the presence of poly(ε‐caprolactone) (PCL) with 2,2,6,6‐tetramethylpiperidinyl‐1‐oxy end group (PCLT). The resulting copolymer showed a narrower molecular weight distribution and controlled molecular weight. The effect of the molecular weight and concentration of PCLT and PEOS on the copolymerization are discussed. The purity of PEOS exerted a significant effect on the copolymerization; when the diol contents of PEO macromonomer were greater than 1%, the crosslinking product was found. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 2093–2099, 2004

Synthesis of Block Copolymers by Changing Living Anionic Polymerization into Living Ring Opening Metathesis Polymerization

A series of AB diblock copolymers have been synthesized by transformation of living anionic polymerization into ring opening metathesis polymerization (ROMP). Ethylene oxide was polymerized anionically using diphenylmethylpotassium as the initiator and was terminated with vinylbenzyl chloride to produce a series of poly(ethylene oxide) (PEO) macromonomers with a terminal vinyl group. An alkylidene exchange reaction was then realized with ruthenium propylidene complex RuCl2(CHC2H5)(PCy3)2, transforming PEO macromonomers into ruthenium ROMP macroinitiators. A variety of norbornene derivatives were then subjected to ROMP using PEO macroinitiators to synthesize well-defined block copolymers of varying molecular weights and compositions.

Swelling behavior of PMMA- g-PEO microgel particles by organic solvents

Aqueous dispersions of cross-linked poly(methylmethacrylate)- g-poly(ethylene oxide) [PMMA- g-PEO] microgel particles have been prepared from mixtures of methylmethacrylate [MMA] and MMA–PEO macromonomer, with ethylene glycol dimethacrylate [EGDM] as the cross-linking monomer (0.2–0.5% wt%). The hydrodynamic radius of these (unswollen) microgel particles ranged from 73 to 85 nm, and the particles were essentially monodisperse with regard to their size distribution. Their swelling behavior has been investigated in the presence of both water-miscible and water-immiscible organic solvents. In general, with the addition of a water-miscible solvent, deswelling behavior was observed. However, the microgel particles were swollen on addition of 1,4-dioxan, which is a good solvent for PMMA. With water-immiscible organic solvents, the extent of swelling depended on the solvency properties of the organic liquid for PMMA. In the presence of benzene, the somewhat large increases in particle size have been attributed to weak flocculation. This has been assumed from an estimate of the van der Waals attraction energy between the swollen microgel particles.

Emulsion and dispersion polymerization of styrene in the presence of PEO macromonomers with p-vinylphenylalkyl end groups

Poly(ethylene oxide) (PEO) macromonomers with α- p-vinylphenylalkyl (propyl, pentyl, and hexyl) and ω-hydroxy end groups were applied to emulsion and dispersion polymerization of styrene as reactive emulsifiers and dispersants in water and in methanol-water mixture (9:1 v/v), respectively. Nearly monodisperse microspheres of submicron to micron size were obtained. Particle size in the emulsion system was one or half order of magnitude smaller than that in the dispersion system, while in both systems the size decreased approximately according to minus one half power of the macromonomer concentration in weight. The particle size was substantially independent on the PEO chain length and also on the spacer alkyl chain length of the α-polymerizing end group. The total weight of the PEO chains incorporated by copolymerization into the particle surfaces (shells), relative to that of styrene polymerized into the particle cores, appears to be a key factor for controlling the particle size. To cite this article: K. Landfester et al., C. R. Chimie 6 (2003).

Heterografted PEO–PnBA brush copolymers

A series of P[(HEMA-TMS)-co-PEOMA] graft copolymers with different amounts of incorporated macromonomer grafts were prepared by copolymerization of a PEO macromonomer (PEOMA, MWav=1100g/mol, DPPEO=23) with 2-(trimethylsilyloxy)ethyl methacrylate (HEMA-TMS) using various initial ratios of the comonomers via atom transfer radical polymerization. After transformation of the HEMA-TMS units to 2-(2-bromopropionyloxy)ethyl methacrylate (BPEM), the resulting P(BPEM-co-PEOMA) copolymers were used as macroinitiators for the controlled polymerization of nBA in a ‘grafting from’ reaction. The resulting densely heterografted brush copolymers with a uniform length of PEO grafts (DPPEO=23) and a range of lengths for the PnBA side chains (DPPnBA=15–60) depending solely on the reaction time. Analysis of the bulk properties showed that the specific architecture of the copolymers suppresses crystallization of the PEO, and consequently leads to amorphous, homogeneous materials.

Syntheses of Poly(ethylene oxide) Macromonomers Carrying Tertiary Amine and Quaternary Ammonium End Groups

p-Vinylbenzyl alcohol, partially alkoxidated with potassium naphthalene, was used successfully to initiate living polymerization of ethylene oxide to afford α-p-vinylbenzyl-ω-hydroxy poly(ethylene oxide) (PEO) macromonomers. The ω-hydroxy end-groups were quantitatively transformed to tertiary amines either by tosylation followed by reaction with potassium 2-dimethylaminoethoxide or by Williamson synthesis with 2-dimethylaminoethyl chloride in the presence of sodium hydride. ω-Quaternary ammonium-ended PEO macromonomers were also quantitatively obtained by reaction with iodomethane.

One-step synthesis of α- p-vinylphenylalkyl-ω-hydroxy poly(ethylene oxide) macromonomers by anionic polymerization initiated from p-vinylphenylalkanols

ω-( p-Vinylphenyl)alkanols, including methanol, ethanol, propanol, pentanol, and hexanol, have been partially alkoxidated with potassium naphthalene to initiate anionic polymerization of ethylene oxide (EO) in order to directly prepare the corresponding α- p-vinylphenylalkyl-ω-hydroxy poly(ethylene oxide) (PEO) macromonomers. p-Vinylphenylmethanol, i.e. p-vinylbenzyl alcohol (VBA) afforded the expected well-defined macromonomer via living polymerization mechanism and the kinetics have been examined as a function of extent of potassium-alkoxidation. Other alcohols such as p-vinylphenylpropanol (VPP), -pentanol (VPPT), and -hexanol (VPH) were also successful to afford the corresponding PEO macromonomers, while p-vinylphenylethanol (VPE) alkoxide polymerized EO to give p-divinylbenzene and poly(ethylene glycol) without p-vinylphenylethoxy end group, which were supposed to form by a very facile intramolecular chain transfer of the activated oligomeric alkoxide chain end to abstract a benzylic proton of the initiating fragment.

Architecture and solution properties of amphiphilic polymer brushes with peripheral charged ions

Functionalized poly(ethylene oxide) (PEO) macromonomers ( α-tertiary amino and ω-methacryloyl groups) were prepared by ring-opening polymerization of live PEO anions end-capped with styrene oxide using 2-[2-( N, N-dimethylamino)-ethoxy]ethanol potassium alkoxides as an initiator with methacryloyl chloride. PEO brushes were synthesized by free-radical homopolymerization of such PEO macromonomers. These brushes were converted into peripherally charged brushes by quaternization. We studied the solution properties of both types of brushes from the viewpoint of charge effect. It was found from dynamic light scattering (DLS) that the polymer brushes formed a single macromolecule in solution due to crowding of side chains. It was speculated from angular dependence measurements that the polymer brushes with large aspect ratios took a geometrical anisotropic conformation such as a cylinder. In methanol with a low dielectric constant, radius of gyration ( R G ), and cross-sectional radius of gyration ( R G,C ) of the polymer brushes with charged side chains were smaller than those of the polymer brushes without charges. In a solvent with a low dielectric constant such as methanol, ionic groups do not dissociate and condense. On the other hand, these physical values in an aqueous solution were somewhat larger than those of the polymer brushes without charges. In water with a high dielectric constant, peripherally charged brushes were strongly stabilized by electric double layers.

Poly(ethylene oxide) macromonomer-grafted polymer nanoparticles synthesised by emulsifier-free emulsion polymerisation

Ultrafine polymer nanoparticles based on poly(ethylene oxide) (PEO) macromonomer-grafted polystyrene (PS) have been synthesised by emulsifier-free emulsion polymerisation. In addition to the binary copolymerisation between PEO macromonomer and styrene, ternary copolymerisations were also conducted in the presence of a cationic monomer (2-(methacryloyloxy)ethyl) trimethylammonium chloride (MATMAC) as a second comonomer. The size and charge characteristics of fine nanoparticles were characterised using both photon correlation spectroscopy and transmission electron microscopy techniques as well as colloidal titration. It was found that after PEO chains (repeat unit 9 or higher) were incorporated into the PS latex, the particle size was significantly reduced owing to the steric effect contributed from grafted PEO chains. Ternary copolymerisation using MATMAC as comonomer further reduced the particle size, leading to nanoparticles as small as 60 nm. Increasing the MATMAC feed ratio gradually reduced the final size of the nanoparticle, owing to the enhancement in electrostatic stabilisation, whereas increasing the PEO macromonomer feed ratios led to slightly larger particles but significantly inhibited the agglomeration of primary particles. The formation mechanism of the nano- or microparticles with various sizes during polymerisation is discussed in terms of nucleation, agglomeration and adsorption of primary particles.

Structured degradable poly(ether) hydrogels based on linear bifunctional macromonomers

AbstractHydrogels based on poly(ethylene oxide) (PEO) are suitable materials for numerous biomedical applications. Among the different ways to design such hydrogels, homopolymerization of bifunctional PEO macromonomers represents a promising approach. The present work discusses the extension of this crosslinking procedure to prepare degradable hydrogels. Poly(1,3‐dioxolane) (PDXL) hydrogels were synthesized directly in water (or in organic solvents) by free‐radical homopolymerization of α,ω‐methacryloyloxy PDXL macromonomers. They were investigated as gels swollen to equilibrium in THF CH2Cl2 or in water. In each case, the amount of extractable material, the extent of equilibrium swelling and the uniaxial compression modulus were determined. Nethertheless, PDXL chains contain acetal groups sensitive to acidic degradation. Hydrogels constituted of hydrophilic poly(ethylene oxide) (PEO) chains containing a short central PDXL block were obtained from α,ω‐methacryloyloxy PEO‐block‐1,3‐PDXL‐block‐PEO macromonomers. The variation of the mechanical properties of pure PDXL networks, when placed in acidic media, was followed by uniaxial compression modulus measurements.© 2002 Society of Chemical Industry

Polymer microspheres with surface chains prepared by dispersion copolymerization using poly(oxyethylene) macromonomer

AbstractPolymer microspheres were prepared by dispersion copolymerization of styrene with poly(oxyethylene) (peo) macromonomer. A dispersion terpolymerization of styrene, PEO macromonomer and acrylic acid was also conducted to prepare polymer microspheres with both surface carboxyl groups and PEO polymer chains. The microspheres thus obtained were characterized with TEM, IR, and X‐ray photoelectron spectroscopy analyses. Palladium nanoparticles were then formed on the surface of these copolymer microspheres forming polymer/metal nanocomposites which were then studied by TEM and X‐ray diffraction. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 86: 2732–2736, 2002

Poly(ethylene oxide) hydrogels as semi-permeable membranes for an artificial pancreas

Poly(ethylene oxide) (PEO) hydrogels were synthesized in organic solvents, or for better results in water, via the free-radical homopolymerization of α,ω-methacryl-oyloxy PEO macromonomers. Their characteristics (amount of extractable material, equilibrium swelling degree, uniaxial compression modulus) could be controlled by the polymerization parameters (precursor molar mass, macromonomer concentration, polymerization time). In aqueous media, the hydrophobic end-standing polymerizable methacrylic units of the macromonomers self-organize, and their polymerization leads to networks with better mechanical properties than those prepared with the same macromonomers but in organic solvents. In vitro tests confirmed their good biocompatibility: almost no adhesion of cells was evident. It was confirmed that glucose diffuses through these hydrogels. Insulin diffusion was also studied but found to be more complex. Schematic representation of a device for an artifical pancreas based on a vascular system.

Fluorescence Probe and Scanning Force Microscopic Studies of Water Soluble Comb-Shaped Copolymers Consisting of a Hydrophobic Poly(p-alkylstyrene) Main Chainand Hydrophilic Poly(ethylene oxide) Grafted Chains

Solution properties of regular amphiphilic comb-shaped polymers have been studied in water by means of fluorescence technique using pyrene as a probe, dynamic light scattering, 1H NMR, and scanning force microscopy (SFM). They consist of a hydrophobic poly(p-alkylstyrene) as a main chain and hydrophilic poly(ethylene oxide) (PEO) chains as a graft chain. Two types of the comb-shaped polymers have been explored, which were prepared by micellar, organized homopolymerization of amphiphilic PEO macromonomers (1) (C1-EOn-(CH2)m-S, with a p-alkylstyrene ((CH2)m-S) end group, with m=1 and 7, and a PEO chain with n=18, 46, 115, and 469) and by copolymerization of C1-EO18-(CH2)7-S with styrene in water, respectively. Partitioning, I1/I3, and excimer formation of pyrene were studied for their dilute aqueous solutions, and rationalized with the local concentration and structure of the comb-shaped polymers. Hydrophobic pyrene molecules were principally dissolved into the vicinity of the hydrophobic p-heptylstyrene main chain of the comb-shaped polymers. The nature of the hydrophobic main chain of poly(styrene-co- C1-EO18-(CH2)7-S) was found to be essentially similar to that of a series of poly(C1-EOn-(CH2)m-S). Direct observation of single macromolecule of poly(C1-EO46-(CH2)7-S) by SFM revealed a high molecular weight, cylindrical brush-like conformation with ca. 12.8 nm in thickness. In contrast, small fine particles were observed for poly(styrene-co-C1-EO18-(CH2)7-S), suggesting the formation of a unimolecular micelle in water.

Free radical homopolymerization, in heterogeneous medium, of linear and star-shaped polymerizable amphiphilic poly(ethers): a new way to design hydrogels well suited for biomedical applications

The synthesis and the properties of selected macromolecular structures based on poly(ethylene oxide), (PEO) are discussed in the present paper. The first part deals with the development of efficient multifunctional anionic initiators aimed to design well-defined functionalizable star-shaped PEO's. Different approaches providing access to branched species of controlled hydrophilic /hydrophobic balance will be considered. The second part is devoted to the homopolymerization of amphiphilic bifunctional PEO macromonomers as an efficient way to yield PEO hydrogels directly in water. The extension of that approach to degradable PEO hydrogels or to the copolymerization of macromonomers with star-shaped PEO's partially functionalized with polymerizable entities will be briefly mentioned. These hydrogels served as semipermeable membrane for an artificial pancreas and as a template for the growth of nervous cells.

Nanofiltration membranes prepared by direct microemulsion copolymerization using poly(ethylene oxide) macromonomer as a polymerizable surfactant

A novel polymer membrane with nanosized pore structures has been prepared from the direct copolymerization of acrylonitrile (AN) with a polymerizable nonionic surfactant in water-in-oil (w/o) or bicontinuous microemulsions. This polymerizable surfactant is ω-methoxy poly(ethylene oxide)40 undecyl-α-methacrylate macromonomer [CH3O(CH2CH2O)40(CH2)11OCO(CH3)CCH2, abbreviated: C1-PEO-C11-MA-40]. Besides PEO macromonomer, AN, and crosslinker ethyleneglycol dimethacrylate, the microemulsion system contained varying amount of water that formed w/o microemulsions having water droplet structures and bicontinuous microemulsions consisting of interconnected water channel. The polymerized membranes prepared in this study have pore radii ranging from 0.38 to 2.4 nm as evaluated by PEG filtration. The pore size appears to vary linearly with water content in precursor microemulsions. But a sharp change in the gradient of the linear relationship is observed around 25 wt % water content. Membranes made from bicontinuous (>25 wt % water) microemulsion polymerization have a larger and interconnected (open-cell) nanostructures. In contrast, much smaller closed-cell (disinterconnected) nanostructures were obtained from w/o (<25 wt % water) microemulsion polymerization and the membrane exhibited a permselectivity toward water in pervaporation separation of high ethanol (>50 wt %) aqueous solutions. The separation factor (α) for 95% ethanol aqueous solution by the membrane derived from the microemulsion containing 10 wt % water is about 20. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 77: 2785–2794, 2000

Nanofiltration membranes prepared by direct microemulsion copolymerization using poly(ethylene oxide) macromonomer as a polymerizable surfactant

A novel polymer membrane with nanosized pore structures has been prepared from the direct copolymerization of acrylonitrile (AN) with a polymerizable nonionic surfactant in water-in-oil (w/o) or bicontinuous microemulsions. This polymerizable surfactant is ω-methoxy poly(ethylene oxide)40 undecyl-α-methacrylate macromonomer [CH3O(CH2CH2O)40(CH2)11OCO(CH3)CCH2, abbreviated: C1-PEO-C11-MA-40]. Besides PEO macromonomer, AN, and crosslinker ethyleneglycol dimethacrylate, the microemulsion system contained varying amount of water that formed w/o microemulsions having water droplet structures and bicontinuous microemulsions consisting of interconnected water channel. The polymerized membranes prepared in this study have pore radii ranging from 0.38 to 2.4 nm as evaluated by PEG filtration. The pore size appears to vary linearly with water content in precursor microemulsions. But a sharp change in the gradient of the linear relationship is observed around 25 wt % water content. Membranes made from bicontinuous (>25 wt % water) microemulsion polymerization have a larger and interconnected (open-cell) nanostructures. In contrast, much smaller closed-cell (disinterconnected) nanostructures were obtained from w/o ( 50 wt %) aqueous solutions. The separation factor (α) for 95% ethanol aqueous solution by the membrane derived from the microemulsion containing 10 wt % water is about 20. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 77: 2785–2794, 2000

Dispersion copolymerization of polyoxyethylene macronomer and styrene 4. Solution properties of polystyrene-graft-polyoxyethylene copolymers

The graft copolymers (polystyrene-graft-polyoxyethylene) (PSt-graft-PEO) were prepared by the radical dispersion copolymerization of methacryloyl (MA)-terminated PEO macromonomer and styrene. By means of size-exclusion chromatography, liquid chromatography at the critical adsorption point, and light scattering, the molecular weight parameters and the solution properties of PSt-graft-PEO were investigated. The apparent average molecular weight and the molecular weight distribution (MWD) of graft copolymers were found to decrease with increasing molecular weight of PEO-MA macromonomer. This decreased molecular weight was attributed to the chain transfer to PEO unit and increased contribution of the solution polymerization. The broad MWD varied with the ratio of the polymerization in the continuous phase and the polymer particles. The number of PEO grafts per PSt backbone decreased with increasing molecular weight of the PSt-graft-PEO copolymer, which was attributed to the intramolecular association of PEO segments. The intrinsic viscosity or the coil size of graft copolymer molecules varied with temperature as a result of the dehydration of PEO segments. © 1999 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 37: 3087–3097, 1999

Controlled Radical Copolymerization of Styrene and the Macromonomer of PEO with a Methacryloyl End Group

The amphiphilic copolymer with uniform poly(ethylene oxide) as side chains was prepared by initiating of AIBN polymerization of methacryloyl-terminated PEO macromonomer (PEOM) and styrene (St) in the presence of 4-hydroxyl-2,2,6,6-tetramethylpiperidine-1-oxy (HTEMPO). The copolymerization is controllable, the molecular weight of the copolymer and the conversion of the monomer increase with the polymerization time, and the distribution is rather narrow and is in the range 1.23−1.33. It was confirmed that the relative reactivity of PEOM macromonomer decreases with an increase in its molecular weight, and the variation of concentration of HTEMPO and AIBN can affect the copolymerization greatly.