Block polymer preparation via both anionic and free radical polymerization

A new method of block polymer preparation using combined anionic and free radical polymerization was investigated. In the method the first monomer was polymerized anionically. The resulting polymeric anions were then reacted with an episulfide to form a polymer with mercaptan end-groups. This mercapto—polymer was mixed with a second monomer(s) in an inert solvent for the free radical polymerization. Conventional free radical initiation methods were used to initiate the polymerization of the second monomer but because of the high chain transfer constant of the mercaptan groups, a large number of the free radical chains would grow from the first polymer to form a block polymer. Block polymers difficult or impossible to make by direct anionic polymerization can thus be prepared. Several block polymers, including the new thermoplastic elastomers, poly[(styrene-co-acrylonitrile)-b-butadiene-b-(styrene-co-acrylonitrile)] and poly(bromostyrene-b-butadiene-b-bromostyrene) were prepared by this method.     

Ring‐opening polymerization of lipoic acid and characterization of the polymer

Thermal polymerization of DL ‐α‐lipoic acid (LPA) in bulk without any initiator proceeded easily above the melting point of LPA. The molecular weight polymer determined by GPC was high. From the ¹H NMR spectra of polymers, poly(LPA) obtained from polymerization of high purity LPA was to consist of cyclic structures, which was confirmed by ESI‐MS. Interlocked polymer consisting of poly(LPA) and dibenzo‐30‐crown‐10 entangled with each other was synthesized by the polymerization of LPA in the presence of dibenzo‐30‐crown‐10. From the DSC analysis of the polymers, glass transition temperature was estimated to be about ?11 °C, but melting point was not observed, indicating that poly(LPA) is an amorphous polymer. By photodecomposition of poly(LPA), M_n was rapidly decreased at the early stage of the decomposition. After that, the M_n of the polymer kept and then was almost constant even for a prolonged reaction time. On the basis of the results, it would be presumed that poly (LPA) obtained form polymerization of high purity LPA includes an interlocked structure. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2010     

Topological bonding formation between an ultra‐high molecular weight linear polymer and a prepolymer at an early stage of free‐radical crosslinking polymerization

The free‐radical crosslinking polymerization of diallyl adipate (DAA) was carried out in the presence of poly(benzyl methacrylate) (poly(BzMA)) as a chemically inactive polymer in order to clarify the topological bonding formation between linear polymer and prepolymer before gelation; we found by chance that even at an early stage of the polymerization, the topological bonding was formed between ultra‐high molecular weight poly(BzMA) and poly(DAA) prepolymer.     

Anionic polymerization of hexafluoro-1,3-butadiene and characterization of the polymer

The present review describes the anionic polymerization of hexafluoro-1,3 -butadiene (HFBD) and the characterization of the polymer. HFBD which is hardly polymerized under radical polymerization conditions yielded the polymer with cesium and rubidium compounds as initiators in moderate conditions. X-ray photoelectron spectra and Raman spectra showed the structure of the polymer was similar to that of poly(hexafluoro-2-butyne). The polymerization mechanism, an addition reaction of the propagating anion to the 2-carbon of HFBD followed by isomerization of the propagating end group to yield the polyene structure, is proposed from the results of the investigation of initiation reaction and the structure of the polymers. Poly(HFBD) shows higher thermostability than poly(tetrafluoroethylene) in spite of bearing functional -CC-groups in the polymer main chain.     

Chain-growth polycondensation for well-defined condensation polymers and polymer architecture

The historical development of our research on polycondensation that proceeds in a chain-growth polymerization manner ("chain-growth polycondensation") for well-defined condensation polymers is described. We first studied polycondensation in which change of the substituent effect induced by bond formation drove the reactivity of the polymer end group higher than that of the monomer. In this approach, well-defined aromatic polyamides, polyesters, polyethers, and poly(ether sulfone)s were obtained. The second approach was the study of the phase-transfer polymerization of a solid monomer dispersed in an organic solvent. In this type of polymerization, the solid monomer was physically unable to react with another monomer and was carried with the phase transfer catalyst into the solution phase where it reacted with an initiator and the polymer end group in the solvent in a chain polymerization manner. We also found catalyst-transfer polycondensation as a third approach to chain-growth polycondensation. In the Ni-catalyzed polycondensation of 2-bromo-5-chloromagnesiothiophenes, the Ni catalyst transferred to the polymer end group, and a coupling reaction occurred there to yield a well-defined polythiophene. This chain-growth polycondensation was applied to the synthesis of condensation polymer architectures such as block copolymers, star polymers, graft copolymers, and so on.     

Preparation of macroporous functionalized polymer beads by a multistep polymerization and their application in zirconocene catalysts for ethylene polymerization

Macroporous functionalized polymer beads of poly(4‐vinylpyridine‐co‐1,4‐divinylbenzene) [P(VPy‐co‐DVB)] were prepared by a multistep polymerization, including a polystyrene (PS) shape template by emulsifier‐free emulsion polymerization, linear PS seeds by staged template suspension polymerization, and macroporous functionalized polymer beads of P(VPy‐co‐DVB) by multistep seeded polymerization. The polymer beads, having a cellular texture, were made of many small, spherical particles. The bead size was 10–50 μm, and the pore size was 0.1–1.5 μm. The polymer beads were used as supports for zirconocene catalysts in ethylene polymerization. They were very different from traditional polymer supports. The polymer beads could be exfoliated to yield many spherical particles dispersed in the resulting polyethylene particles during ethylene polymerization. The influence of the polymer beads on the catalytic behavior of the supported catalyst and morphology of the resulting polyethylene was investigated. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 41: 873–880, 2003     

Preparation of ionic liquid-encapsulated polymer particles

Encapsulation of ionic liquid, 1-hexyl-3-methylimidazolium bis(trifluoromethane sulfonyl)amide ([Hmim][TFSA]), was carried out by microsuspension polymerization of ethylene glycol dimethacrylate (EGDM) utilizing the self-assembling of phase-separated polymer method, which had been proposed by us for the preparation of hollow polymer particles. After the optimization of the polymerization conditions, ionic liquid-encapsulated polymer particles, which have smooth surface morphology and a single hollow structure, were successfully prepared. Encapsulation efficiency of [Hmim][TFSA] was significantly improved from about 20–70 % by changing the shell polymer from polyEGDM homopolymer to poly(EGDM-butyl methacrylate) (50/50, w/w) copolymer, which was likely to have relatively low affinity for [Hmim][TFSA]. Additionally, ionic liquid-encapsulated polymer particles displaying ionic conductivity were successfully prepared using triethylene glycol dimethacrylate as divinyl monomer instead of EGDM.     

Uniform polymer in synthetic polymer chemistry

The preparation of uniform polymers and their use in fundamental polymer chemistry are reviewed. A typical method of preparation is a combination of living polymerization and supercritical fluid chromatography separation. Synthetic uniform polymers allow us to solve ambiguous problems in polymer chemistry due to molecular weight distribution and are of significant importance for studies on structure–property relationships. A close inspection of an isotactic uniform chloral oligomer with a symmetrical chemical structure reveals that oligomers are the first examples of stable atropisomers of aldehyde oligomers and that their chiroptical properties are due only to their helical geometries. A molecular-level understanding of the mechanism and stoichiometry of the association process of polymer molecules is possible only with uniform polymers, and stereocomplex formation between isotactic and syndiotactic poly(methyl methacrylate)s in acetone has vigorously been studied by size exclusion chromatography (SEC) and NMR. End-functionalized uniform polymers have enabled us to prepare uniform polymer architectures, such as block, graft, comb, and star polymers. A uniform stereoblock poly(methyl methacrylate) with an isotactic (methyl methacrylate)₄₆-syndiotactic (methyl methacrylate)₄₆ structure shows a single SEC peak in chloroform but three peaks in acetone, which are ascribable to intermolecularly and intramolecularly associated complexes and nonassociated molecules. A three-arm star polymer with one isotactic chain and two syndiotactic chains shows a peculiar SEC behavior in acetone due to a braid type of intramolecular stereocomplex formation. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 416–431, 2004     

Fullerene-containing branched polymethacrylates and polymer networks: Synthesis,structure, and properties

Branched poly(methyl methacrylates) containing covalently and noncovalently attached fullerene C₆₀ are synthesized and characterized by IR and UV spectroscopy. The basic physicochemical characteristics of the branched poly(methyl methacrylate) comprising covalently attached fullerene and the non-functionalized branched polymer of the same composition are compared. The effect of fullerene-containing branched poly(methyl methacrylates) on the kinetics of the crosslinking radical polymerization of 1,6-hexanediol dimethacrylate and on the structural-physical (mechanical, thermomechanical, and diffusion-sorption) properties of the resulting polymers is examined. The role of fullerene attached to the branched poly(methyl methacrylate) as an inhibitor of the crosslinking radical polymerization of dimethacrylate and as a modifier of the structure and properties of the polymers is ascertained.     

Electrically conductive composite prepared by template polymerization of pyrrole into a complexed polymer

Electrically conducting polymer composite films have been synthesized by the exposure of poly(4-vinylpyridine) complexed with cupric ions to pyrrole and water vapor. To immobilize a stoichiometric amount of the oxidant inside the polymer matrix, the ratio of poly(4-vinylpyridine)/cupric ion = 1.8 was chosen. Polypyrrole was formed in this tailored structure by a template polymerization process. Opaque polymer composite films with electrical conductivity up to 60 (Ω cm)^?1 have been obtained by this method, However, slightly colored transparent composite thin films with a conductivity as high as 50 (Ω cm)^?1 were also produced. The electrically conducting polymer composite films and the metal-polymer complex have been characterized by XPS and IR spectroscopy, elemental analysis, EDX, and scanning electron microscopy. The polymerization process was also followed by use of a quartz crystal microbalance. © 1994 John Wiley & Sons, Inc.     

Facile synthesis of hollow polymer microspheres with movable cores with the aid of hydrogen-bonding interaction

Poly(divinylbenzene-co-acrylic acid) (poly(DVB-co-AA)) hollow microspheres with movable poly(DVB-co-AA) cores were prepared by a facile route. In this approach, poly(DVB-co-AA) microspheres were first used as templates to synthesize poly(DVB-co-AA)@PAA core-shell particles with a non-crosslinked PAA shell by distillation precipitation polymerization in acetonitrile. In situ polymerization to prepare poly(DVB-co-AA)@PAA@poly(DVB-co-AA) trilayer microspheres was then developed, in which the hydrogen-bonding interaction between the carboxylic acid groups played a key role as the driving force for the formation of monodisperse trilayer structure polymer microspheres. After removal of the non-crosslinked poly(acrylic acid) (PAA) midlayer of the poly(DVB-co-AA)@PAA@poly(DVB-co-AA) microspheres in ethanol under basic conditions, poly(DVB-co-AA) hollow microspheres with movable poly(DVB-co-AA) cores were obtained. Functional poly(DVB-co-AA) cores could be released successfully when the hollow structure was destroyed. The resultant core-shell, trilayer polymer microspheres and hollow polymer microspheres with movable cores were characterized by transmission electron microscopy (TEM), dynamic laser scattering (DLS), and Fourier transform infrared (FT-IR) spectra.     

Poly(silmethylene)-based polymer blends. I. In situ polymerization of 1,3-disilacyclobutanes in silicon-based polymers

The in situ polymerization of 1,1,3,3-tetraphenyl-1,3-disilacyclobutane with or without a catalyst in flexible organo-silicon polymers was demonstrated to provide poly(silmethylene)-based polymer blends. An alternative route, which implies preparation of blends via synthesis of a flexible polymer in the presence of a rigid polymer, was also promising. The resulting polymer blends were characterized by DSC, dynamic mechanical analysis, and solvent extraction. No chemical interaction is observed between component polymers of blends prepared by the in situ bulk polymerization method while formation of block or graft copolymers comprising poly(diphenylsilmethylene) and flexible polymers is suggested when in situ copper-catalyzed polymerization was employed. A morphological difference between samples synthesized by the different methods was suggested by microscopic observation. © 1997 John Wiley & Sons, Inc.     

Preparation and characterization of monolithic column by grafting pH-responsive polymer

A novel modified monolithic column with pH-responsive polymer chains was prepared by grafting methacrylic acid onto the poly(glycidyl methacrylate-co-ethylene dimethacrylate) monolith. The grafting polymerization was achieved in an in situ manner which was performed by pumping methacrylic acid directly through an acidic hydrolysis monolithic column using potassium peroxydisulfate initiated free-radical polymerization. The grafted monolithic column was demonstrated to be the pH-responsive to the pore structure and the chromatographic characterization. The permeability of the column and the retention factors of five benzene homologues decreased due to the conformational changes of the polymer chains when the pH of mobile phase increased from 4.5 to 7.5. Furthermore, the modified monolithic column was used as the pH-responsive stationary phase and exhibited an excellent separation of four basic proteins.     

Control of heterogeneous structure of porous polymer microspheres prepared from polymerization system and preformed polymer system

The studies on control of heterogeneous structure of porous polymer microspheres prepared for suspension polymerization system and preformed polymer system in author’s research group were reviewed. Firstly, the phase-separation behavior in O/W suspension polymerization system for preparation of porous poly(divinylbenzene) microspheres was quantitatively studied by combining transmittance and gelation point measurement, from which the morphology can be manipulated. The same method can be employed to study the pore size control in W/O hydrophilic polymerization system. Because the simple porous microsphere could not satisfy new applications, we developed new methods to prepare gigaporous microsphere, which possessed much larger pores than those obtained by general diluents, for chromatographic separation media, as well as hollow-porous microsphere for construction of cell-like microreactor. Furthermore, in order to overcome the difficulty of heterogeneous structure control for preformed polymer system, we developed special methods to obtain porous, hollow-porous, and hollow chitosan microspheres. Finally, some application results by utilizing special morphologies were introduced.     

High density cationic polymer brushes from combined “click chemistry” and RAFT‐mediated polymerization

A simple method for preparing cationic poly[(ar‐vinylbenzyl)trimethylammonium chloride)] [poly(VBTAC)] brushes was used by combined technology of “click chemistry” and reversible addition‐fragmentation chain transfer (RAFT) polymerization. Initially, silicon surfaces were modified with RAFT chain transfer agent by using a click reaction involving an azide‐modified silicon wafer and alkyne‐terminated 4‐cyanopentanoic acid dithiobenzoate (CPAD). A series of poly(VBTAC) brushes on silicon surface with different molecular weights, thicknesses, and grafting densities were then synthesized by RAFT‐mediated polymerization from the surface immobilized CPAD. The immobilization of CPAD on the silicon wafer and the subsequent polymer formation were characterized by X‐ray photoelectron spectroscopy, water contact angle measurements, grazing angle‐Fourier transform infrared spectroscopy, atomic force microscopy, and ellipsometry analysis. The addition of free CPAD was required for the formation of well‐defined polymer brushes, which subsequently resulted in the presence of free polymer chains in solution. The free polymer chains were isolated and used to estimate the molecular weights and polydispersity index of chains attached to the surface. In addition, by varying the polymerization time, we were able to obtain poly(VBTAC) brushes with grafting density up to 0.78 chains/nm² with homogeneous distributions of apparent needle‐like structures. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012     

A new temperature-sensitive polymer: Poly(ethoxypropylacrylamide)

In this study, a new temperature sensitive polymer was obtained by the solution polymerization of ethoxypropylacrylamide. The monomer, N-(3-ethoxypropyl)-acrylamide was synthesized by the nucleophilic substitution reaction of 3-ethoxy-propylamine and acryloyl chloride. The solution polymerization was performed in ethanol at 70 °C, by using azobisizobutyronitrile as the initiator. Poly(N-(3-ethoxypropyl)acrylamide), PEPA, exhibited a reversible phase transition by the temperature. The effects of polymer and salt concentrations on the lower critical solution temperature, (LCST) behaviour were investigated. LCST was found to be strongly dependent on the polymer concentration. The dynamic light scattering (DLS) measurements confirmed the formation of aggregates by the association of nucleated polymer chains at the temperatures higher than LCST. However an unusual behaviour, a marked decrease in the hydrodynamic diameter by the increasing PEPA concentration was observed below the LCST. The effect of salt concentration on the critical flocculation temperature of PEPA was reasonably similar to poly(isopropylacrylamide), PNIPA. In the ethanol-water media, the reversible phase transition behaviour was observed up the ethanol concentration of 30% v/v. This study indicated that PEPA was a new alternative thermally reversible material for PNIPA. With respect to the well-defined temperature-sensitive polymers like PNIPA, polymer concentration dependent LCST of PEPA can provide significant advantages in the applications like drug targeting, affinity separation and immobilization of bioactive agents.     

Preparation of a novel polymer monolith with functional polymer brushes by two‐step atom‐transfer radical polymerization for trypsin immobilization

Novel porous polymer monoliths grafted with poly{oligo[(ethylene glycol) methacrylate]‐co‐glycidyl methacrylate} brushes were fabricated via two‐step atom‐transfer radical polymerization and used as a trypsin‐based reactor in a continuous flow system. This is the first time that atom‐transfer radical polymerization technique was utilized to design and construct polymer monolith bioreactor. The prepared monoliths possessed excellent permeability, providing fast mass transfer for enzymatic reaction. More importantly, surface properties, which were modulated via surface‐initiated atom‐transfer radical polymerization, were found to have a great effect on bioreactor activities based on Michaelis–Menten studies. Furthermore, three model proteins were digested by the monolith bioreactor to a larger degree within dramatically reduced time (50 s), about 900 times faster than that by free trypsin (12 h). The proposed method provided a platform to prepare porous monoliths with desired surface properties for immobilizing various enzymes.     

Poly(carbon suboxide): A photosensitive paramagnetic ladder polymer

Carbon suboxide was found to give, on photo- and thermal-polymerization, a photosensitive paramagnetic polymer. Studies of the kinetics of the ESR signal growth accompanying the polymerization process complement documented results obtained from monitoring the rate of polymer production and monomer disappearance. The spin concentration of the polymer increases with higher reaction temperature, reaching 2 × 10¹⁹ spin/g at a polymerization temperature of 105°C. The paramagnetism of poly(carbon suboxide) follows the Curie—Weiss law. Relaxation behavior at room temperature and g values for the spin systems have been obtained. The 105°C polymer shows a Weiss constant equal to 17°K and an extremely narrow ESR line width, ca. 10 mG, at 5°K. The ¹³C coupling constant from the selectively labeled polymer indicates π-electron delocalization over the ladder polymer. The polymer paramagnetism can be further reversibly enhanced by visible light irradiation. The steady-state concentration of the photo-ESR signal is proportional to the square root of incident light intensity, with a quantum yield at room temperature for charge accumulation equal to 5% at an incident light level of 10¹⁵ photons/sec-cm². Fluorescence and excitation spectra of the soluble fraction of poly(carbon suboxide) are presented together with the quantum yield. The polymer has also been found to be an effective photopolymerization initiator at wavelengths longer than 340 nm.     

Nanoscale evaluation of lubricity on well-defined polymer brush surfaces using QCM-D and AFM

For preparing a “highly lubricated biointerface”, which has both excellent lubricity and biocompatibility, we investigated the factors responsible for resistance to friction during polymer grafting. We prepared poly(2-methacryloyloxyethyl phosphorylcholine) (PMPC), poly(2-hydroxyethyl methacrylate) (PHEMA), and poly(methyl methacrylate) (PMMA) brush layers with high graft density and well-controlled thickness using atom transfer radical polymerization (ATRP). We measured the water absorptivity in the polymer brush layers and the viscoelasticity of the polymer-hydrated layers using a quartz crystal microbalance with dissipation monitoring (QCM-D) measurements. The PMPC brush layer had the highest water absorptivity, while the PMPC-hydrated layer had the highest fluidity. The friction properties of the polymer brush layers were determined in air, water, and toluene by atomic force microscopy (AFM). The friction on each polymer brush decreased only when a good solvent was chosen for each polymer. In conclusion, the brush layer possessing high water absorptivity and fluidity in water contributes to reduce friction. PMPC grafting is an effective and promising method for obtaining highly lubricated biointerfaces.