Surface grafting onto SiC nanoparticles with glycidyl methacrylate in emulsion

To improve the tribological performance of nano‐SiC particles filled epoxy composites, surface modification of the fillers is necessary. By means of soapless emulsion polymerization method, graft polymerization of glycidyl methacrylate (GMA) onto the surface of alkyl nano‐SiC was carried out, resulting in composite particles with SiC core and polymeric shell in which polyglycidyl methacrylate (PGMA) is chemically attached to the nanoparticles by the double bonds introduced during the pretreatment with a coupling agent. By analyzing the reaction mechanism, the emulsion polymerization loci were found to be situated at the SiC surface. Also, the factors affecting the grafting yielding of PGMA on the particles were investigated, including monomer concentration, initiator consumption, reaction temperature, reaction time, etc. Accordingly, an optimum grafting reaction condition was determined. It was shown that the grafted nanoparticles exhibit greatly improved dispersibility in good solvent for the grafting polymer. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 3842–3852, 2004     

Direct synthesis of amphiphilic block copolymers from glycidyl methacrylate and poly(ethylene glycol) by cationic ring‐opening polymerization and supramolecular self‐assembly thereof

Amphiphilic block copolymers composed of a hydrophilic poly(ethylene glycol) (PEG) block and a hydrophobic poly(glycidyl methacrylate) (PGMA) block were synthesized through cationic ring‐opening polymerization with PEG as the precursor. The model reactions indicated that the reactivity of the epoxy groups was higher than that of the double bonds in the bifunctional monomer glycidyl methacrylate (GMA) under the cationic polymerization conditions. Through the control of the reaction time in the synthesis of block copolymer PEG‐b‐PGMA, a linear GMA block was obtained through the ring‐opening polymerization of epoxy groups, whereas the double bond in GMA remained unreacted. The results showed that the molecular weight of the PEG precursor had little influence on the grafting of GMA, and the PGMA blocks almost kept the same length, despite the difference of the PEG blocks. In addition, the PGMA blocks only consisted of several GMA units. The obtained amphiphilic PEG‐b‐PGMA block copolymers could form polymeric core–shell micelles by direct molecular self‐assembly in water. The crosslinking of the PGMA core of the PEG‐b‐PGMA micelles, induced by ultraviolet radiation and heat instead of crosslinking agents, greatly increased the stability of the micelles. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 2038–2047, 2005     

Magnetic poly(glycidyl methacrylate) particles prepared in the presence of surface‐modified γ‐Fe2O3

Maghemite (γ‐Fe₂O₃) colloid has been synthesized by coprecipitation of ferrous and ferric salts in alkaline medium and oxidation. The obtained nanoparticles were complexed with a phosphate macromonomer—penta(propylene glycol) methacrylate phosphate (PPGMAP). Complexes with the weight ratio PPGMAP/γ‐Fe₂O₃ 0.01–10 were investigated using a range of characterization methods. The amount of PPGMAP attached to the particles was about 22 wt %. The size and size distribution of the γ‐Fe₂O₃ core particles in the dry state was measured by TEM. To complete the TEM images, the hydrodynamic size of the nanoparticles including polymer shell and the maghemite core was determined by DLS measurements in toluene. Magnetic poly(glycidyl methacrylate) (PGMA) nanospheres were obtained by Kraton G 1650‐stabilized and 2,2′‐azobisisobutyronitrile‐initiated polymerization of glycidyl methacrylate (GMA) in toluene or toluene/cyclohexane mixture in the presence of PPGMAP‐coated γ‐Fe₂O₃ colloid. The effect of Kraton G 1650 concentration on the morphology, PGMA nanosphere size and polydispersity was investigated. The particles were characterized also by both thermogravimetric analysis and magnetic measurements. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 4982–4994, 2009     

Core‐shell structured poly(glycidyl methacrylate)/BaTiO3 nanocomposites prepared by surface‐initiated atom transfer radical polymerization: A novel material for high energy density dielectric storage

Core‐shell structured barium titanate‐poly(glycidyl methacrylate) (BaTiO₃‐PGMA) nanocomposites were prepared by surface‐initiated atom transfer radical polymerization of GMA from the surface of BaTiO₃ nanoparticles. Fourier transform infrared spectroscopy confirmed the grafting of the PGMA shell on the surface of the BaTiO₃ nanoparticles cores. Transmission Electron Microscopy results revealed that BaTiO₃ nanoparticles are covered by thin brushes (～20 nm) of PGMA forming a core‐shell structure and thermogravimetric analysis results showed that the grafted BaTiO₃‐PGMA nanoparticles consist of ～13.7% PGMA by weight. Upon incorporating these grafted nanoparticles into 20 μm‐thick films, the resultant BaTiO₃‐PGMA nanocomposites have shown an improved dielectric constant (ε = 54), a high breakdown field strength (～3 MV/cm) and high‐energy storage density ～21.51 J/cm³. AC conductivity measurements were in good agreement with Jonscher's universal power law and low leakage current behavior was observed before the electrical breakdown field of the films. Improved dielectric and electrical properties of core‐shell structured BaTiO₃‐PGMA nanocomposite were attributed to good nanoparticle dispersion and enhanced interfacial polarization. Furthermore, only the surface grafted BaTiO₃ yielded homogenous films that were mechanically stable. © 2014 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2015 , 53, 719–728     

Magnetic poly(glycidyl methacrylate) microspheres prepared by dispersion polymerization in the presence of electrostatically stabilized ferrofluids

Fine magnetite nanoparticles, both electrostatically stabilized and nonstabilized, were synthesized in situ by precipitation of Fe(II) and Fe(III) salts in alkaline medium. Magnetic poly(glycidyl methacrylate) (PGMA) microspheres with core‐shell structure, where Fe₃O₄ is the magnetic core and PGMA is the shell, were obtained by dispersion polymerization initiated with 2,2′‐azobisisobutyronitrile (AIBN), 4,4′‐azobis(4‐cyanovaleric acid) (ACVA), or ammonium persulfate (APS) in ethanol containing poly(vinylpyrrolidone) or ethylcellulose stabilizer in the presence of iron oxide ferrofluid. The average microsphere size ranged from 100 nm to 2 μm. The effects of the nature of ferrofluid, polymerization temperature, monomer, initiator, and stabilizer concentration on the PGMA particle size and polydispersity were studied. The particles contained 2–24 wt % of iron. AIBN produced larger microspheres than APS or ACVA. Polymers encapsulating electrostatically stabilized iron oxide particles contained lower amounts of oxirane groups compared with those obtained with untreated ferrofluid. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 5827–5837, 2004     

Highly efficient and well‐controlled ambient temperature RAFT polymerization of glycidyl methacrylate under visible light radiation

A range of well‐defined poly(glycidyl methacrylate) (PGMA) polymers and their corresponding block copolymers were synthesized via 2‐cyanoprop‐2‐yl(4‐fluoro) dithiobenzoate or CPFDB‐mediated ambient temperature reversible addition fragmentation chain transfer radical polymerization or RAFT polymerization under environmentally friendly visible light radiation (λ = 405–577 nm), using a (2,4,6‐trimethylbenzoyl) diphenylphosphine oxide photoinitiator. As comparison, CPFDB‐mediated ambient temperature RAFT polymerizations of glycidyl methacrylate (GMA) under both full‐wave radiation (λ = 254–577 nm) and long‐wave radiation (λ = 365–577 nm) were also studied in this article. The results indicated that CPFDB moieties were significantly photolyzed under either full‐wave radiation or long‐wave radiation, thus undermining the controlled behavior of these RAFT processes. Whereas this photolysis was significantly suppressed under visible light radiation, thus CPFDB functionalities exerted well control over RAFT process, leading to a remarkably living behavior up to 90% GMA monomer conversions. This strategy facilitates the facile synthesis of well‐defined PGMA polymers. More importantly, under visible light radiation, a relatively high initial molar ratio of GMA to CPFDB and TPO led to shortening initialization period of RAFT process and accelerating overall polymerization rate. These effects are remarkably in favor of the facile synthesis of well‐defined PGMA polymers and PGMA‐based copolymers with high molecular weights. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 5091–5102, 2007     

单分散聚合物微球稳定Pickering乳液法制备大粒径微胶囊相变材料

采用二步加料的分散聚合法制备单分散聚甲基丙烯酸缩水甘油酯(PGMA)微球,并使其水解,得到水包油(O/W)型Pickering乳液稳定剂.在Pickering乳液聚合过程中,利用相分离机制,形成了聚苯乙烯(PSt)和PGMA复合为整体囊壳的微胶囊相变材料.微胶囊平均粒径达76μm,囊芯含量高达83%,相变焓达到174 J/g,具有很高的储热容量.     

Synthesis,characterization, and micellization of an epoxy‐based amphiphilic diblock copolymer of ϵ‐caprolactone and glycidyl methacrylate by enzymatic ring‐opening polymerization and atom transfer radical polymerization

Amphiphilic diblock copolymer polycaprolactone‐block‐poly(glycidyl methacrylate) (PCL‐b‐PGMA) was synthesized via enzymatic ring‐opening polymerization (eROP) and atom transfer radical polymerization (ATRP). Methanol first initiated eROP of ?‐caprolactone (?‐CL) in the presence of biocatalyst Novozyme‐435 under anhydrous conditions. The resulting monohydroxyl‐terminated polycaprolactone (PCL–OH) was subsequently converted to a bromine‐ended macroinitiator (PCL–Br) for ATRP by esterification with α‐bromopropionyl bromide. PCL‐b‐PGMA diblock copolymers were synthesized in a subsequent ATRP of glycidyl methacrylate (GMA). A kinetic analysis of ATRP indicated a living/controlled radical process. The macromolecular structures were characterized for PCL–OH, PCL–Br, and the block copolymers by means of nuclear magnetic resonance, gel permeation chromatography, and infrared spectroscopy. Differential scanning calorimetry and wide‐angle X‐ray diffraction analyses indicated that the copolymer composition (?‐CL/GMA) had a great influence on the thermal properties. The well‐defined, amphiphilic diblock copolymer PCL‐b‐PGMA self‐assembled into nanoscale micelles in aqueous solutions, as investigated by dynamic light scattering and transmission electron microscopy. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 5037–5049, 2007     

Preparation and characterization of biotinylated and enzyme‐immobilized heterobifunctional latex particles as nanobio devices

A novel biotinylated and enzyme‐immobilized nanobio device was prepared with heterobifunctional composite latex particles. Hemispherical poly(glycidyl methacrylate‐co‐divinylbenzene)/polystyrene [P(GMA‐DVB)/PSt] particles with epoxy and hydroxyl groups were prepared by soap‐free seeded emulsion polymerization with P(GMA‐DVB) seed particles. Hydroxyl groups were introduced to PSt chain terminals in the seeded stage by adding 2‐mercaptoethanol as a chain‐transfer agent. To obtain the desired hemispherical structure particles, we studied the effects of the preswelling process, the type and amount of solvents added in the seeded polymerization step, the weight ratio of the secondary monomer (styrene) to the seed particle (M/P), and the type of initiators. Under suitable conditions, heterobifunctional P(GMA‐DVB)/PSt was obtained, which was confirmed by observing the binding of streptavidin–colloidal gold with transmission electron microscopy (TEM). To obtain biotinylated and enzyme‐immobilized particles, 5‐(N‐succinimidyloxycarbonyl)pentyl D‐biotinamide was first reacted with the hydroxyl group on the PSt domain of the particle. Pyruvate kinase (PK) was then directly immobilized to the biotinylated particles through a reaction with the epoxy group in the PGMA domain. The monolayer of PK on the latex particle surface was considered to be formed by covalent binding. The activity of immobilized PK was almost conserved, even after being stored at 4 °C for 48 days. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 562–574, 2005     

Preparation of polymer/silica composite nanoparticles bearing carboxyl groups on the surface via emulsifier‐free emulsion copolymerization

Polymer/silica organic/inorganic composite nanoparticles bearing carboxyl groups on the surface were prepared via the emulsifier‐free emulsion copolymerization of methyl methacrylate and sodium methacrylate (NaMA). Carboxyl groups were generated by the addition of hydrochloric acid at the end of the copolymerization. Two methods of NaMA addition were studied: batch and two‐stage procedures. The batch procedure allowed only a limited number of carboxyl groups to effectively bond to the composite nanoparticles. In contrast, the number of carboxyl groups could be altered over a wide range with the two‐stage procedure. Fourier transform infrared spectroscopy and chemical titration were independently used to quantify the number of carboxyl groups, giving values close to each other and to the feed. A kinetic study indicated that the copolymerization followed a mechanism different than that found earlier. The average size of the composite nanoparticles was approximately 40 nm, as measured by both transmission electron microscopy (TEM) and laser scattering, and their polydispersity index was close to 1, indicating a fairly narrow size distribution. TEM photographs of the composite nanoparticles showed a multilayered core–shell structure with one silica bead as the core and with poly(methacrylate acid) as the outmost shell. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 2826–2835, 2005     

Synthesis and curing of poly(glycidyl methacrylate) nanoparticles

Glycidyl‐functional polymer nanoparticles [poly(glycidyl methacrylate) (PGMA)] were fabricated with microemulsion polymerization. The successful fabrication of PGMA nanoparticles was confirmed by Fourier transform infrared spectroscopy and transmission electron microscopy (TEM). A TEM image showed that the average diameter of the PGMA nanoparticles was approximately 10–28 nm and was fairly monodisperse. As the surfactant concentration increased, the average size of the nanoparticles decreased and approached an asymptotic value. A significant reduction of the nanoparticle size to the nanometer scale led to an enhanced number of surface functionalities, which played an important role in the curing reaction. The PGMA nanoparticles were cured with a low‐temperature curing agent, diethylene triamine, to produce ultrafine thermoset nanoparticles. The low‐temperature curing process was performed below the glass‐transition temperature of PGMA to prevent the coagulation and deformation of the nanoparticles. A TEM image indicated that the cured PGMA nanoparticles did not exhibit interparticle aggregation and morphological transformation during curing. The average size of the cured PGMA nanoparticles was consistent with that of the pristine PGMA nanoparticles © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 2258–2265, 2005     

Reversible addition–fragmentation chain transfer polymerization of glycidyl methacrylate with 2‐cyanoprop‐2‐yl 1‐dithionaphthalate as a chain‐transfer agent

A reversible addition–fragmentation chain transfer (RAFT) agent, 2‐cyanoprop‐2‐yl 1‐dithionaphthalate (CPDN), was synthesized and applied to the RAFT polymerization of glycidyl methacrylate (GMA). The polymerization was conducted both in bulk and in a solvent with 2,2′‐azobisisobutyronitrile (AIBN) as the initiator at various temperatures. The results for both types of polymerizations showed that GMA could be polymerized in a controlled way by RAFT polymerization with CPDN as a RAFT agent; the polymerization rate was first‐order with respect to the monomer concentration, and the molecular weight increased linearly with the monomer conversion up to 96.7% at 60 °C, up to 98.9% at 80 °C in bulk, and up to 64.3% at 60 °C in a benzene solution. The polymerization rate of GMA in bulk was obviously faster than that in a benzene solution. The molecular weights obtained from gel permeation chromatography were close to the theoretical values, and the polydispersities of the polymer were relatively low up to high conversions in all cases. It was confirmed by a chain‐extension reaction that the AIBN‐initiated polymerizations of GMA with CPDN as a RAFT agent were well controlled and were consistent with the RAFT mechanism. The epoxy group remained intact in the polymers after the RAFT polymerization of GMA, as indicated by the ¹H NMR spectrum. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 2558–2565, 2004     

Synthesis and characterization of asymmetric centipede‐like copolymers with two side chains at each repeating unit via ATRP and ring‐opening polymerization

A series of well‐defined centipede‐like copolymers with poly(glycidyl methacrylate) (PGMA) as main chain and poly(L ‐lactide) (PLLA) and polystyrene (PSt) as side chains have been synthesized successfully by combination of ring‐opening polymerization and atom transfer radical polymerization (ATRP). The synthetic process includes three steps. (1) Synthesis of PGMA via ATRP; (2) preparation of macroinitiator with one bromine group and a hydroxyl group at every GMA unit of PGMA; (3) ring‐opening polymerization of LLA and ATRP of St to obtain the asymmetric centipede‐like copolymers. The number–average degrees of polymerization of PGMA backbone, PLLA and PSt side chains were determined by ¹H‐NMR spectra, and the molecular weights of the resultant intermediates and centipede‐like copolymers were measured by gel permeation chromatography. The molecular weight distributions were narrow and the molecular weights of both the backbone and the side chains were controllable. The thermal behavior of the centipede‐like copolymers was investigated by differential scanning calorimeter. With the increase of PSt side chain length, the glass transition temperature of PLLA side chains shifted to high temperature, and crystallization ability of PLLA side chains became poor. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 5580–5591, 2008     

Encapsulation of silica nanoparticles by miniemulsion polymerization

Hybrid silica/polystyrene nanoparticles were synthesized by miniemulsion polymerization. With the objective to prepare core‐shell hybrid nanoparticles having narrow particle size distributions (PSDs) as well as a high degree of silica encapsulation, the effect of adding surface modifiers, the size of silica nanoparticles, the ratio styrene/silica, the surfactant concentration, and the presence of ethanol in the reaction mixture were studied. A synergistic effect was observed using oleic acid (OA) together with 3‐(trimethoxysilyl)propyl methacrylate (TPM) in the compatibilization step between the organic phase (monomer) and inorganic nanoparticles (silica). Mono and multinuclear eccentric core‐shell hybrid nanoparticles were obtained. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 935–948, 2009     

Effects of surfactants on the morphology of composite polymer particles produced by two‐stage seeded emulsion polymerization

Poly(methyl methacrylate) (PMMA)–polystyrene (PS) composite polymer particles were synthesized in the presence of a surfactant by two‐stage seeded emulsion polymerization. The first stage was the synthesis of PMMA particles by soapless emulsion polymerization; the second stage was the synthesis of the PMMA–PS composite polymer particles with the PMMA particles as seeds. In the second stage of the reaction, three kinds of surfactants—sodium laurate sulfate (SLS), polyoxyethylene (POE) sorbitan monolaurate (Tween 20), and sorbitan monolaurate (Span 20)—were used to synthesize the PMMA–PS composite particles. Both the properties and concentrations of the surfactants influenced the morphology of the composite particles significantly. Core–shell composite particles, with PS as the shell and PMMA as the core, were synthesized in the presence of a low concentration of the hydrophilic surfactant SLS. This result was the same as that in the absence of the surfactant. However, a low concentration of Tween 20 led to composite particles with a core/strawberry‐like shell morphology; the core region was a PS phase, and the strawberry‐like shell was a PS phase dispersed in a PMMA phase. With an increase in the concentration of SLS, the morphology of the composite particles changed from core (PMMA)–shell (PS) to core (PS)–shell (PMMA). Moreover, the effects of a high concentration of Tween 20 or Span 20 on the morphology of the PMMA–PS composite particles were investigated in this study. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 2224–2236, 2005     

利用反向原子转移自由基聚合反应合成聚甲基丙烯酸缩水甘油酯

以偶氮二异丁腈为引发剂,CuBr2/bpy为催化体系,甲基丙烯酸缩水甘油酯(GMA)通过反向原子转移自由基聚合反应合成了聚甲基丙烯酸缩水甘油酯(PGMA),其结构经1H NMR,IR和GPC确证。聚合反应符合活性自由基聚合特征,在聚合过程中GMA转化率和PGMA分子量随反应时间的延长而增大,分子量分布较窄。     

Immobilization of RAFT agents on silica nanoparticles utilizing an alternative functional group and subsequent surface‐initiated RAFT polymerization

Silica–polystyrene core‐shell particles were successfully prepared by surface‐mediated reversible addition fragmentation chain transfer (RAFT) polymerization of styrene monomer from the surfaces of the silica‐supported RAFT agents. Initially, macro‐RAFT agents were synthesized by RAFT polymerization of γ‐methacryloxypropyltrimethoxysilane (MPS) in the presence of chain transfer agents (CTAs). Immobilization of CTAs onto the silica surfaces was then performed by reacting silica with macro‐RAFT agents via a silane coupling. Grafting of polymer onto silica forms core‐shell nanostructures and shows a sharp contrast between silica core and polymer shell in the phase composition. The thickness of grafted‐polymer shell and the diameter of core‐shell particles increase with the increasing ratio of monomer to silica. A control experiment was carried out by conventional free radical emulsion copolymerization of MPS‐grafted silica and styrene under comparable conditions. The resulting data provide further insight into the chemical composition of grafted‐polymers that are grown from the silica surface through RAFT process. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 467–484, 2009     

Preparation of Cross‐Linked Micelles from Glycidyl Methacrylate Based Block Copolymers and Their Usages as Nanoreactors in the Preparation of Gold Nanoparticles

This study reports the synthesis of poly(ethylene glycol)methyl ether‐block‐poly(glycidyl methacrylate) (MPEG‐b‐PGMA) diblock, and poly(ethylene glycol)methyl ether‐block‐poly(glycidyl methacrylate)‐block‐poly(methyl methacrylate) (MPEG‐b‐PGMA‐b‐PMMA) triblock copolymers via atom transfer radical polymerization and their self‐assembly behaviors in aqueous media by using acetone as cosolvent. These block copolymers formed near monodisperse core–shell micelles having cross‐linkable cores. Two types of cross‐linked micelles, namely spherical MPEG‐b‐PGMA core cross‐linked (CCL) micelles and MPEG‐b‐PGMA‐b‐PMMA interlayer cross‐linked (ILCL) micelles, were also successfully prepared from these block copolymers by using various bifunctional cross‐linkers such as hexamethylenediamine (HMDA), ethylenediamine (EDA), and 2‐aminoethanethiol (AET). Cross‐linking was successfully carried out via ring‐opening reactions of epoxy residues of hydrophobic‐cores with primary amine or thiol groups of bifunctional cross‐linkers. Finally, these cross‐linked micelles were successfully used as nanoreactors in the synthesis of gold nanoparticles (AuNPs) in aqueous media. Both CCL and ILCL micelles were found to be good stabilizers for AuNPs in aqueous media. Both CCL‐ and ILCL‐stabilized AuNP dispersions were stable for a long time without any size changes and flocculation at room temperature. These cross‐linked stabilized AuNPs exhibited good catalytic activities in the reduction of p‐nitrophenol. © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2018 , 56, 514–526.     

Preparation of SiO2/PMMA composite particles via conventional emulsion polymerization

A series of SiO₂/PMMA composite particles with different morphologies were prepared by conventional emulsion polymerization by the aid of acid–base interaction between the silanol groups of unmodified silica particles and the amino groups of 4‐vinylpyridine. In this approach, no surface treatment for nanosilica particles was required. The morphologies of composite particles, for example, multicore–shell, raspberry‐like, and conventional core–shell, could be controlled by modulating emulsifier content, monomer/silica ratio, silica size, and monomer feed method. The possible particle formation mechanisms were discussed. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 3807–3816, 2006