Poly(ethylene glycol)‐containing cationic hydrogels with lipophilic character

Not much effort has been focused towards the development of hydrogels that swell in nonpolar solvents. We have synthesized a new set of polyelectrolyte hydrogels and demonstrated their ability to absorb a less‐polar or nonpolar organic solvent, as well as their ability to resist gel‐collapse in a predominantly nonpolar medium. The hydrogels were prepared by free radical polymerization of different molar ratios of poly(ethylene glycol) methyl ether acrylate and (3‐(methacryloylamino)propyl)‐trimethyl ammonium chloride as comonomers in an aqueous medium. Their swelling behavior in organic solvents was studied by varying the dielectric constant of the swelling medium including mixed‐solvent systems. Besides a high degree of swelling (up to 200 times) in polar solvents, some of the hydrogels also exhibited moderate swelling (up to 15 times) in less‐polar organic solvents. Hydrogels samples with high cationic content showed drastic change in swelling extent in some of the mixed‐solvent systems. It was also interesting to note that the retention of significant swelling in dimethyl sulphoxide–toluene mixture with even 90% toluene content for some compositions. These polyelectrolyte hydrogels with improved lipophilicity opens up greater opportunities for the development of even superior soft materials through proper structural optimizations that would successfully function for a wider range of solvents. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 39873.     

Reaction Factors Influencing the Synthesis of Polystyrene-Polyurethane-Polystyrene Triblock Copolymer

Polystyrene-polyurethane-polystyrene (PS-PU-PS) triblock copolymer was synthesized by two-step polymerization. The first step, polyurethane (PU) prepolymers based on 2,4-toluene diisocyanate (TDI), hydrophilic poly(ethylene glycol) (PEG), hydroxyethyl acrylate (HEA), and ethylene glycol (EG), were prepared with ethylene glycol as a chain extender, dibutyltin dilaurate as a catalyst, and toluene as a solvent. The next step, polystyrene-polyurethane-polystyrene (PS-PU-PS) triblock copolymers, were prepared by free radical copolymerization between PU prepolymer and styrene (ST) monomer. Toluene and 2,2′-azobisisobutyronitrile (AIBN) were used as solvent and initiator, respectively. Fourier transform infrared spectroscopy (FT-IR) spectroscopy was used to characterize the structure of the copolymer. Influences of reaction temperature, reaction time, catalyst sorts, isocyanate monomer sorts, solvent sorts, and the concentration of initiator on the synthesis of the triblock copolymer were studied.     

Syntheses of acrylate core/shell imbiber beads by seeded suspension copolymerization and one‐stage copolymerization for solvent absorption–desorption

Seeded suspension copolymerization or a one‐stage copolymerization was used to synthesize acrylate core/shell imbiber beads. A two‐stage polymerization technique was used for seeded suspension polymerization. The seed particles for poly(methyl acrylate) or poly(2‐ethylhexyl acrylate) were synthesized first in a mixed solvent of toluene/isooctane containing the ethylene glycol dimethacrylate (EGDMA) crosslinking agent. These beads were swollen in styrene‐EGDMA‐BPO (benzoyl peroxide) and then polymerized in the aqueous phase to produce the polystyrene (PS) shell. The one‐stage copolymerization was carried out in toluene/isooctane containing methyl methacrylate (MMA), styrene (St), EGDMA, and BPO at 75°C for 10 h to give a core/shell copolymer of St‐MMA morphology. The appearance of core/shell imbiber beads prepared from these two techniques varied from monomer to monomer. This article describes the preparation, characterization, and application of the core/shell beads for organic solvent absorption/desorption. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 85: 670–682, 2002     

Preparation of nanometer‐sized poly(methacrylic acid) particles in water‐in‐oil microemulsions

A water‐in‐oil microemulsion, water‐in‐cyclohexane stabilized by poly(ethylene glycol) tert‐octylphenyl, was developed to prepare poly(methacrylic acid) (PMAA) particles. Up to 100% conversion of the amphiphilic monomer, methacrylic acid (MAA), which could not be converted to the polymer efficiently in a dioctylsulfosuccinate sodium salt/toluene microemulsion, was achieved. The viscosity‐average molecular weight of the PMAA prepared was 1.45 × 10⁵ g/mol. The effects of some polymerization parameters, including the reaction temperature and the concentrations of the initiator and the monomer, on the polymerization of MAA were investigated. The results showed that the polymerization rate of MAA was slower than that of acrylamide in the microemulsions reported in the literature. The degree of conversion increased with the initiator concentration, reaction temperature, and monomer concentration. However, the stable microemulsions became turbid during the polymerization when the reaction temperature was at 70°C or at a high monomer concentration (40 wt %) The synthesized PMAA particles were spherical and had diameters in the range of ～50 nm. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 2497–2503, 2006     

Porous crosslinked copolymers of octadecyl acrylate with acrylic acid as sorbers for crude petroleum spills

Bulk and suspension polymerization were used to prepare octadecyl acrylate/acrylic acid (ODA/AA) copolymers. AA content ranged from 0 to 90 mol%. Divinyl benzene was used as a crosslinker at several concentrations (1, 4 and 10 wt%). Isopropyl alcohol or dioctyl phthalate and methyl benzoate were used as the reaction solvents in the presence of poly(vinyl alcohol) as a dispersing agent and 2,2‐azobis isobutyronitrile as the initiator. The polymers so prepared were coated onto poly(ethylene terephthalate) nonwoven (NWPET) fibers. The effects of copolymerization, feed composition, crosslinker concentration and reaction medium or solvent on morphology including porosity and the dynamic mechanical and swelling properties of the crosslinked polymers were determined. Swelling tests were performed in toluene and in 10% crude petroleum diluted with toluene. Bulk polymerization does not result in the formation of a continuous liquid absorbing material while suspension polymerization enables sorbers to be obtained with desired properties. Coating ODA/AA copolymers onto NWPET increases liquid absorption. © 2013 Society of Chemical Industry     

Preparation of narrow‐disperse or monodisperse poly{[poly(ethylene glycol) methyl ether acrylate]‐co‐(acrylic acid)} microspheres with ethyleneglycol dimethacrylate as crosslinker by distillation precipitation polymerization

Narrow‐disperse or monodisperse poly{[poly(ethylene glycol) methyl ether acrylate]‐co‐(acrylic acid)} (poly(PEGMA‐co‐AA)) microspheres were prepared by distillation precipitation polymerization with ethyleneglycol dimethacrylate (EGDMA) as crosslinker with 2,2′‐azobisisobutyronitrile as initiator in neat acetonitrile in the absence of any stabilizer, without stirring. The diameters of the resultant poly(PEGMA‐co‐AA‐co‐EGDMA) microspheres were in the range 200–700 nm with a polydispersity index of 1.01–1.14, which depended on the comonomer feed of the polymerization. The addition of the hydrogen bonding monomer acrylic acid played an essential role in the formation of narrow‐disperse or monodisperse polymer microspheres during the polymerization. Copyright © 2006 Society of Chemical Industry     

Plasma‐graft polymerization of a monomer with double bonds onto the surface of carbon fiber and its adhesion to a vinyl ester resin

Double bonds reactive with active radical species were introduced onto the surface of carbon yarn by the plasma‐graft polymerization of adipic acid divinyl ester and ethylene glycol dimethacrylate monomers to increase the adhesive strength in the interface between the carbon yarn and a vinyl ester resin. The degree of grafting increased with increasing polymerization time and polymerization temperature. The degree of grafting depended on both the solvent and the monomer species used in the polymerization, and a high degree was obtained with ethylene glycol dimethacrylate as the conjugated monomer and in a mixture of methyl isobutyrate and water. The grafted yarn, whose surface layer contained double bonds, was reacted with a vinyl ester resin containing benzoyl peroxide and N,N‐dimethylaniline. The pull‐out force of the yarn embedded in the resin increased with increasing degree of grafting. The failure in pulling out the yarn was cohesive. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 90: 2415–2419, 2003     

水性苯乙烯-丙烯酸-马来酸酐共聚物的合成及表征

以过氧化苯甲酰为引发剂、二丙二醇二甲醚为溶剂,采用自由基聚合方法,合成苯乙烯-丙烯酸-马来酸酐三元共聚物。考察单体配比、引发剂用量、反应温度对聚合物性能的影响,并用红外光谱、凝胶色谱、差示扫描量热法等对共聚物进行表征。结果表明,最佳工艺条件是:n(ST):n(AA):n(MA)=6:3:1,反应温度为85℃,引发剂为单体质量的12%;得到数均分子量为4678、分子量多分散指数为1.45的三元共聚物。     

The effects of solvent and initiator on anionic ring opening polymerization of ϵ‐caprolactone: synthesis and characterization

Anionic ring opening polymerization of ?‐caprolactone was studied by using different amounts of two potassium activated initiators containing ethylene glycol (EG) and polyhedral oligomeric silsesquioxane (POSS) diol, in tetrahydrofuran and toluene as solvents. The synthesized hydroxyl terminated macromers and linear poly(?‐caprolactone) (PCL) were characterized by proton and carbon nuclear magnetic resonance and gel permeation chromatography (GPC) techniques. Results showed an increase in molecular weight as the monomer/initiator molar ratio increased from 100 to 151 and 202, while the molecular weight distribution (MWD) showed a minimum by monomer concentration increase. Moreover, POSS‐diol‐initiated PCLs showed a higher MWD than the polymers initiated with the EG initiator. This was attributed to the formation of a vesicular structure of POSS diols which was confirmed by optical microscopy. By deconvolution of GPC peaks, the best conditions to synthesize PCL with the narrowest MWD were selected. Finally, the effects of some other parameters were studied in more detail.     

Grafting of the acrylic acid on poly(ethylene terephthalate)

A study has been made of the effect of solvent nature, concentrations of monomer, initiator and homopolymerization inhibitors, and initial polymer structure on the modification of poly(ethylene terephthalate) (PET) films and fibers by grafting the acrylic acid (AA). AA grafting initiated by radicals formed from thermal decomposition of benzoyl peroxide. It has been established that preswelling of PET in dichloroethane leads to changes in its sorption–diffusion properties and favors an increase in the degree of grafting. Addition of the Fe(II), Ni(II), and Cu(II) salts to AA solution decreased homopolymer yield. The studied process of grafting can be described by equations of diffusion kinetics. Distribution of the poly(acrylic acid) (PAA) over the cross section of samples and a number of physical and chemical properties depend also on conditions of performing the graft polymerization.     

聚酸酐硅基酯的制备与表征

以聚己二酸酐（PAA）和氯硅氧烷Si3C6H18O2C12（Si3）和Si5C10H30O4C12（Si5）为单体合成聚己二酸酐硅基酯。所得样品用1H-NMR、DSC、TGA和测特性黏数等手段对其进行了表征。考察了反应过程中反应时间、溶剂等因素的影响。所得样品用1H-NMR，DSC-TGA进行分析，结果较理想。测得多组样品特性黏数，显示所得产物具有高分子的特性。     

Degree of conversion of a copolymer of an experimental monomer and methyl methacrylate for dental applications

The aim of this study was to determine the degree of double bond conversion of the copolymer of an experimental monomer and methyl methacrylate after photopolymerization. A mixture of an experimental monomer with four methacrylate groups and methyl methacrylate monomer (mass ratio 70 : 30) was polymerized by using various concentrations of light initiator system. The degree of conversion was determined with FTIR spectrometry. A photopolymerized 2,2‐bis[4‐(2‐hydroxy‐3‐methacryloxypropoxy)‐ phenyl]propane/triethylene glycol dimethacrylate (mass ratio 40 : 60) copolymer was used as a control material for degree of conversion. The maximum degree of conversion for the experimental monomer/methyl methacrylate copolymer was 62% and was obtained with 2 wt % initiator concentration. It was comparable to that of the control polymer (64%). The results of this study suggest that the experimental monomer/methyl methacrylate system can be polymerized by light initiator system. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 93: 1908–1912, 2004     

Dispersion copolymerization of methyl methacrylate and acrylic acid in polar media: effects of reaction parameters on the particle size and size distribution of the copolymer microspheres

Micron‐size functional crosslinked poly(methyl methacrylate) (PMMA) particles with narrow size distribution in the range of 1～5 µm were prepared by dispersion copolymerization in polar media with poly(N‐vinylpyrrolidone)(PVP) as steric stabilizer, 2,2′‐azobisisobutyronitrile(AIBN) as initiator and ethylene glycol dimethylacrylate (EGDMA) as crosslinking agent. The effects of functional comonomer acrylic acid (AA) concentration, contents in AIBN, EGDMA and PVP, media polarity as well as reaction temperature on the particle size and size distribution were investigated. Particle size initially increased, and then decreased with increasing AA concentration in the range of 0.7～3.5 mol l^?1, having a maximum of 5.01 µm at the concentration of 2.1 mol l^?1, while size distribution became broader. This was regarded as the result of different roles of PAA in the process. Particle size increased with decreasing media polarity and stabilizer concentration, and with increasing initiator concentration and reaction temperature. The resulting particle shapes were observed by transmission electron microscopy and the presence of carboxyl groups on the surface of the particles was confirmed by Fourier‐transform infrared spectroscopy. Copyright © 2003 Society of Chemical Industry     

Bipyridine copper functionalized polymer resins as support materials for the aerobic oxidation of alcohols

Here, we report the first polymer resin supported Cu(I)/bipyridine/N ‐oxyl catalyst systems for the aerobic oxidation of alcohols at room temperature with ambient air. We chose polystyrene‐poly(ethylene glycol) copolymer (TentaGel®) and Merrifield resin as support materials because of their different swelling properties in polar and nonpolar solvents. The bromo functionalized TentaGel resin TG1 or Merrifield resin MR1 were functionalized with 4,4′‐dimethoxy‐2,2′‐bipyridine (^MeObpy) to give the ligand modified polymer resin TG2/MR2 that was loaded with Cu^I(Br) to give the final Cu^I(Br)/bipyridine support TG3/MR3. These resins were characterized by Fourier transform infrared, SEM, SEM energy dispersive X‐ray spectroscopy and elemental analysis. Catalytic activity and recyclability of TG3 was investigated in acetonitrile and cyclohexane and displayed high activities in acetonitrile but also high metal leaching. In cyclohexane as solvent leaching was reduced to 1% ? 2%, and catalytic activity was still at 75% after the fifth run. MR3 was consequently tested in cyclohexane and toluene. In both solvents low metal leaching was observed with higher activity in toluene as solvent, showing still over 90% conversion after the seventh run with 9‐azabicyclo[3.3.1]nonane N ‐oxyl (ABNO) and 80% with 2,2,6,6‐tetramethyl‐1‐piperidinyloxyl (TEMPO). © 2016 Society of Chemical Industry     

Time-resolved gel permeation chromatographic study on poly(N-isopropylacrylamide)-block-poly(ethylene glycol) prepared by soap-free emulsion polymerization

To synthesize an amphiphilic block copolymer of poly(N-isopropylacrylamide)-block-poly(ethylene glycol) (NE), an aqueous soap-free emulsion polymerization system was employed where poly(N-isopropylacrylamide) (PNIPA), polymerized from the radically activated chain ends of poly(ethylene glycol) (PEG), forms micelle cores stabilized by PEG brush chains emanating there from. When this polymerization was carried out at temperatures equal to or higher than 34 °C, narrowly-dispersed NE, which cannot be obtained by solution polymerization, was successfully obtained. To elucidate the living nature of the soap-free emulsion polymerization, time-dependent monomer conversion and molecular weight of NE was investigated by time-resolved gel permeation chromatography (GPC). The results indicate that the compartmentalization of end radicals into micelles cores leads to the quasi-living behavior of the polymerization.     

Preparation and characterization of poly{[α‐maleic anhydride‐ω‐methoxy‐poly(ethylene glycol)]‐co‐(ethyl cyanoacrylate)} copolymer nanoparticles

Poly{[α‐maleic anhydride‐ω‐methoxy‐poly(ethylene glycol)]‐co‐(ethyl cyanoacrylate)} (PEGECA) copolymers were prepared by radical polymerization of macromolecular poly(ethylene glycol) monomers (PEGylated) and ethyl 2‐cyanoacrylate in solvent. The structures of the copolymer were characterized by Fourier‐transform infrared (FTIR) and proton nuclear magnetic resonance (¹H‐NMR). The morphology and size of the PEGECA nanoparticles prepared by nanoprecipitation techniques were investigated by transmission electron microscopy (TEM) and photon correlation spectroscopy (PCS) methods. The results show that the PEGECA can self‐assemble into highly stable nanoparticles in aqueous media, and inner core and outer shell morphology. The size of the nanoparticles was strongly influenced by the solvent character and the copolymer concentration in the organic solvents. A hydrophobic drug, ibuprofen, was effectively incorporated into the nanoparticles, which provides a delivery system for ibuprofen and other hydrophobic compounds. Copyright © 2005 Society of Chemical Industry     

Synthesis and aggregation behavior of four types of different shaped PCL‐PEG block copolymers

Biodegradable, amphiphilic, linear (diblock and triblock) and star‐shaped (three‐armed and four‐armed) poly[(ethylene glycol)‐block‐(ε‐caprolactone)] copolymers (PEG–PCL copolymers) were synthesized by ring‐opening polymerization of ε‐caprolactone (CL) with stannous octoate as a catalyst, in the presence of monomethoxypoly(ethylene glycol) (MPEG), poly(ethylene glycol) (PEG), three‐armed poly(ethylene glycol) (3‐arm PEG) or four‐armed poly(ethylene glycol) (4‐arm PEG) as an initiator, respectively. The monomer‐to‐initiator ratio was varied to obtain copolymers with various PEG weight fractions in a range 66–86%. The molecular structure and crystallinity of the copolymers, and their aggregation behavior in the aqueous phase, were investigated by employing ¹H‐NMR spectroscopy, gel permeation chromatography and differential scanning calorimetry, as well as utilizing the observational data of gel–sol transitions and aggregates in aqueous solutions. The aggregates of the PEG–PCL block copolymers were prepared by directly dissolving them in water or by employing precipitation/solvent evaporation technique. The enthalpy of fusion (ΔH_m), enthalpy of crystallization (ΔH_crys) and degrees of crystallinity (χ_c) of PEG blocks in copolymers and the copolymer aggregates in aqueous solutions were influenced by their PEG weight fractions and molecular architecture. The gel–sol transition properties of the PEG–PCL block copolymers were related to their concentrations, composition and molecular architecture. Copyright © 2006 Society of Chemical Industry     

Synthesis of PEGylated poly(amino acid) pentablock copolymers and their self‐assembly

Pentablock copolymers with an ABCBA architecture were synthesized by ring‐opening polymerization of N‐carboxyanhydrides of l ‐leucine and γ‐benzyl l ‐glutamate using an α, ω‐diamino poly(ethylene glycol) (PEG) as macroinitiator. Three different PEGs with molecular weights of 2000, 4600 and 10 000 Da were used and the poly(amino acid) (PAA) block lengths were set to a combined 10 and 40, respectively, repeat units for p(l ‐Leu) and 40 repeat units for p(l ‐Glu). The molecular architecture of the resulting pentablock copolymers was determined by the order of monomer addition. The living character of the N‐carboxyanhydride ring‐opening polymerization enables the formation of multiblock copolymers. The degree of polymerization for the PAA blocks matched the monomer/initiator ratio. A structural switch element, which controls the hydrophilicity of the pentablock copolymers, was incorporated in the form of the p(l ‐Glu) blocks. The pentablock copolymers became water soluble after hydrolyzing the benzyl ester protective groups. The pentablock copolymers self‐assembled into polymeric aggregates ranging in size between 160 and 340 nm. Hydrogels formed readily if the central PEG block had a molecular weight of at least 4600 Da and the terminal A‐blocks consisted of p(l ‐Leu). SEM images confirmed the size ranges of the polymeric aggregates and showed non‐distinct spherical aggregates. © 2016 Society of Chemical Industry     

Effects of the solvent polarity on the atom transfer radical polymerization of methyl methacrylate initiated by 4‐(chloromethyl)phenyltrimethoxysilane

The controllability of the atom transfer radical polymerization of methyl methacrylate in the polar solvent N,N‐dimethylformamide and the nonpolar solvent xylene with 4‐(chloromethyl)phenyltrimethoxysilane as an initiator and with CuCl/2,2′‐bipyridine and CuCl/4,4′‐di(5‐nonyl)‐2,2′‐bipyridine as catalyst systems was studied. Gel permeation chromatography analysis established that in the nonpolar solvent xylene, much better control of the molecular weight and polydispersity of poly(methyl methacrylate) was achieved with the CuCl/4,4′‐di(5‐nonyl)‐2,2′‐bipyridine catalyst system than with the CuCl/2,2′‐bipyridine as catalyst system. In the polar solvent N,N‐dimethylformamide, unlike in xylene, the polymerization was more controllable with the CuCl/2,2′‐bipyridine catalyst system than with the CuCl/4,4′‐di(5‐nonyl)‐2,2′‐bipyridine catalyst system. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 104: 2751–2754, 2007     

Highly efficient reversible addition–fragmentation chain‐transfer polymerization in ethanol/water via flow chemistry

Utilization of a flow reactor under high pressure allows highly efficient polymer synthesis via reversible addition–fragmentation chain‐transfer (RAFT ) polymerization in an aqueous system. Compared with the batch reaction, the flow reactor allows the RAFT polymerization to be performed in a high‐efficiency manner at the same temperature. The adjustable pressure of the system allows further elevation of the reaction temperature and hence faster polymerization. Other reaction parameters, such as flow rate and initiator concentration, were also well studied to tune the monomer conversion and the molar mass dispersity (?) of the obtained polymers. Gel permeation chromatography, nuclear magnetic resonance (NMR), and Fourier transform infrared spectroscopies (FTIR) were utilized to monitor the polymerization process. With the initiator concentration of 0.15 mmol L^?1, polymerization of poly(ethylene glycol) methyl ether methacrylate with monomer conversion of 52% at 100 °C under 73 bar can be achieved within 40 min with narrow molar mass dispersity (D) ? (<1.25). The strategy developed here provides a method to produce well‐defined polymers via RAFT polymerization with high efficiency in a continuous manner. © 2017 Society of Chemical Industry