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

A copolymerization of macromonomer poly(ethylene oxide) (PEO) with a styryl end group (PEO_S) and styrene was successfully carried out in the presence of poly(ε‐caprolactone) (PCL) with 2,2,6,6‐tetramethylpiperidinyl‐1‐oxy end group (PCL_T). The resulting copolymer showed a narrower molecular weight distribution and controlled molecular weight. The effect of the molecular weight and concentration of PCL_T and PEO_S on the copolymerization are discussed. The purity of PEO_S 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     

Influence of residual impurities on ring‐opening metathesis polymerization after copper(I)‐catalyzed alkyne‐azide cycloaddition click reaction

Bottlebrush polymers (BBPs) are three‐dimensional polymers with great academic and industrial potential owing to their highly tunable and intricate architecture. The most popular method to synthesize BBPs is ring‐opening metathesis polymerization (ROMP) with Grubbs' catalyst, allowing living grafting‐through polymerization of macromonomers of up to ultrahigh molecular weights with narrow molecular weight distribution. In this case, it has been well recognized that the purity of macromonomers (MMs) is critical for a successful ROMP reaction. For MMs synthesized from reversible‐deactivation radical polymerization, Grubbs and Xia demonstrated that the better control of ROMP reaction can be achieved when they are prepared via “growth‐then‐coupling” method that is coupling a norbornenyl group to end‐functionalized prepolymers. However, these MMs can also contain various residual impurities from previous synthetic steps, which can potentially poison the catalyst and hamper the ROMP reaction. Herein, we intentionally doped possible impurities into purified MMs to identify the most poisoning species. As a result, it was found that alkyne‐functionalized norbornene most significantly retarded the ROMP reaction due to a formation of Ru‐vinyl‐carbene intermediates having low catalytic reactivity, whereas the other reagents such as solvent, Cu‐catalyst, ligands, and azido‐terminated prepolymers were relatively inert. © 2019 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2019 , 57, 726–737     

Synthesis and Self-Assembly of 2nd Generation Dendritic Homopolymers and Copolymers of Polydienes with Different Isomeric Microstructures

Synthesis of 2^nd generation dendritic polymeric materials via anionic polymerization procedures in combination with chlorosilane chemistry, consisting either from one polydienic segment (homopolymers) or from two chemically different polydienic components (copolymers), is described. The polydienes used were poly(butadiene) (PB) with ∼90% 1,4-isomerism and poly(isoprene) (PI) with increased 3,4-isomerism (∼60%). Molecular characterization of intermediate products and the final dendritic materials was made with Gel Permeation Chromatography (GPC), Membrane and Vapour Pressure Osmometry (MO and VPO respectively), Gas Chromatography –Mass Spectroscopy (GC-MS) and ¹H-Nuclear Magnetic Resonance (¹H-NMR) Spectroscopy, leading to the conclusion that they can be considered model polymers. Morphological studies solely with Transmission Electron Microscopy (TEM) have been conducted on two of the four synthesized copolymer samples exhibiting microphase separation between the two polydiene segments.     

Dendronized Polymers via Macromonomer Route in Supercritical Carbon Dioxide

Radical polymerizations from third to fifth generation macromonomers were conducted in supercritical carbon dioxide (scCO₂). It was found that all monomers were not soluble in such a medium, and reactions occurred in the CO₂‐swollen monomer matrices. Despite the expected severe diffusion limitations, very high conversions and molecular weights were obtained. It is believed that the plasticization effect induced by the CO₂ plays a key role in these surprising findings. Scanning force microscopical analyses confirmed that mainly linear dendronized polymers were obtained and therefore chain transfer to polymer is virtually irrelevant.

     

Controlled cyclopolymerization of 4,5-disubstituted 1,7-octadiynes and its application to the synthesis of a dendronized polymer using Grubbs catalyst

Cyclopolymerization of 1,7-octadiynes using a ruthenium-based Grubbs catalyst, to produce conjugated polymers containing six-membered rings as repeat units is generally much slower than the corresponding polymerization of 1,6-heptadiynes, and thus it is considered less useful. Here, we demonstrate the regioselective cyclopolymerization of 4,5-disubstituted 1,7-octadiynes with considerably enhanced reactivity. Using a third generation Grubbs catalyst with a rapid initiation step, various conjugated polymers with low polydispersity indices (PDIs) could be synthesized under optimized conditions. Among the various monomers tested, those with bulky substituents underwent controlled polymerization within 1 h at room temperature, which was a significant improvement over previous reports. This led us to a more efficient preparation of fully conjugated block copolymers. Finally, owing to the fast cyclopolymerization, a synthetically challenging dendronized polymer was successfully prepared from a macromonomer containing two second generation dendrons at the 4 and 5 positions of 1,7-octadiyne, and its rod-like conformation was visualized using atomic force microscopy. © 2014 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2015 , 53, 274–279     

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.     

Dispersion copolymerization of poly(oxyethylene) macromonomers and styrene

The kinetics of dispersion copolymerization of methacryloyl-terminated poly(oxyethylene) (PEO-MA) and p-vinylbenzyl-terminated (PEO-St) polyoxyethylene macromonomers and styrene (St), initiated by a water- and/or oil-soluble initiator, was investigated using conventional gravimetric and NMR methods at 60°C. The batch copolymerizations in the water/ethanol continuous phase were conducted to high conversion. The rate of polymerization was described by the curve with a maximum at very low conversion. The initial rate of polymerization and the number-average molecular weight were found to decrease with increasing [PEO-MA], and the decrease was more pronounced in the range of a high macromonomer concentration. The rate per particle (at ca. 20% conversion) was found to be proportional to the −1.55th, the particle size to the −0.92nd, and the number of particles (at final conversion) to the 3.2nd power of [PEO-MA], respectively. At the beginning of polymerization the continuous phase is the main reaction locus. As the polymerization advances, the reaction locus is shifted from the continuous phase to the polymer particles. The transform of the reaction loci from the continuous phase to the polymer particles increases the rate of polymerization and the polymer molecular weights. The increase of the weight ratio PEO-MA/St favors the formation of monodisperse polymer particles, the colloidal stability of dispersion, and the formation of a larger number of polymer particles. © 1997 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 35: 3131–3139, 1997     

Reactive surfactants in heterophase polymerization. Part XXI—kinetics of styrene dispersion polymerization stabilized with poly(ethylene oxide) macromonomers

The kinetics of styrene dispersion polymerization, using poly(ethylene oxide) macromonomers as precursors for the stabilization, has been studied. The conversions of both styrene and macromonomers have been determined. The effects of various parameters such as the polarity of the medium, the nature and the amount of macromonomer and the concentrations of the reactants have been studied. A strong gel effect was observed, the main polymerization process taking place inside the particles where the average number of radicals per particle may be more than a thousand. © 1997 John Wiley & Sons, Ltd.     

One-step synthesis of macromonomers catalyzed by phosphazene base

Herein, we report one-step synthesis of polymethacrylates-based macromonomers (MMs) in the presence of an organocatalyst phosphazene base (t-BuP₄) and a functional initiator N-butyl-4-vinylbenzamide (N-BVBA) containing a secondary amide and a styrenic double bond. A series of styrenic MMs with controlled molecular weight and relatively narrow polydispersity were synthesized under mild conditions. Detailed NMR analyses of the initiation process suggested that the anionic polymerization was initiated by nitrogen anion generated from abstraction of the proton from the secondary amide. NMR and MALDI-TOF MS analyses confirmed: (1) the selective polymerization of methacrylate-type double bonds, (2) controlled chain-end functionality of MMs with an unreacted styrenic double bond, as well as (3) the absence of transesterification between N-BVBA and methacrylate monomers. Furthermore, the homopolymerization and copolymerization of the MMs with comonomers were carried out for the preparation of graft copolymers. Through conventional radical polymerization, graft copolymers with different grafting densities were obtained at high MMs conversions, indicating the high reactivity of MMs. Thus, the one-step approach demonstrates a simple metal-free access to the controlled synthesis of MMs, and the prepared MMs can polymerize efficiently to convert into graft copolymers.