Separation and characterization of poly(styrene‐co‐acrylonitrile)‐graft‐poly(propylene oxide) polymer stabilizer formed in dispersion polymerization of styrene and acrylonitrile in polyether

Poly(styrene‐co‐acrylonitrile)‐graft‐poly(propylene oxide) (PSAN‐graft‐PPO), the stabilizer formed in situ in the dispersion polymerization of styrene, acrylonitrile and macromonomer PPO maleate in PPO polyol, was separated from ungrafted copolymer PSAN by liquid chromatography. After the determination of the separation conditions by thin‐layer chromatography, the effective separation of the graft polymer from copolymer PSAN was achieved by liquid column chromatography. The graft efficiency and the composition of the graft polymer was determined by UV and ¹H NMR, and the formation characteristics of the graft polymer are discussed. © 2001 Society of Chemical Industry     

Synthesis of block copolymers via redox polymerization

Polymerization and copolymerization of vinyl monomers such as acrylamide, acrylonitrile, vinyl acetate, and acrylic acid with a redox system of Ce(IV) and organic reducing agents containing hydroxy groups were studied. The reducing compounds were poly(ethylene glycol)s, halogen‐containing polyols, and depolymerization products of poly(ethylene terephthalate). Copolymers of poly(ethylene glycol)s‐b‐polyacrylonitrile, poly(ethylene glycol)s‐b‐poly(acrylonitrile‐co‐vinyl acetate), poly(ethylene glycol)s‐b‐polyacrylamide, poly(ethylene glycol)s‐b‐poly(acrylamide‐co‐vinyl acetate), poly(1‐chloromethyl ethylene glycol)‐bpoly(acrylonitrile‐co‐vinyl acetate), and bis[poly(ethylene glycol terephthalate)]‐b‐poly(acrylonitrile‐co‐vinyl acetate) were produced. The yield of acrylamide polymerization and the molecular weight of the copolymer increased considerably if about 4% vinyl acetate was added into the acrylamide monomer. However, the molecular weight of the copolymer was decreased when 4% vinyl acetate was added into the acrylonitrile monomer. Physical properties such as solubility, water absorption, resistance to UV light, and viscosities of the copolymers were studied and their possible uses are discussed. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 71: 1385–1395, 1999     

Synthesis of monodisperse crosslinked polystyrene microspheres via dispersion copolymerization with the crosslinker‐postaddition method

Monodisperse crosslinked polystyrene microspheres were prepared by the dispersion copolymerization of styrene and divinylbenzene in a mixed solvent of ethanol and H₂O. 2,2′‐Azobisisobutyronitrile and poly(N‐vinyl pyrrolidone) were used as the initiator and steric stabilizer, respectively. The crosslinker‐postaddition method was adopted through a slow addition of a crosslinking agent into the dispersion system at a certain time after the beginning of the polymerization. The effects of the postaddition recipe, postaddition beginning time, postaddition velocity, and agitation rate on the particle size, size distribution, and morphology were discussed. The resulting polymer microspheres were characterized with scanning electron microscopy and laser particle analysis. Crosslinked polystyrene microspheres with a narrow size distribution and a 12.0% crosslinker level were obtained with a size of 1.0 μm through the crosslinker‐postaddition method. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2008     

Synthesis and characterization of the novel block copolymer poly(ε‐caprolactone)‐b‐poly(4‐vinyl pyridine) by the combination of coordination and controlled free‐radical polymerizations

A novel block copolymer, poly(ε‐caprolactone)‐b‐poly(4‐vinyl pyridine), was synthesized with a bifunctional initiator strategy. Poly(ε‐caprolactone) prepolymer with a 2,2,6,6‐tetramethylpiperidinyloxy (TEMPO) end group (PCL_T) was first obtained by coordination polymerization, which showed a controlled mechanism in the process. By means of ultraviolet spectroscopy and electron spin resonance spectroscopy, the TEMPO moiety was determined to be intact in the polymerization. The copolymers were then obtained by the controlled radical polymerization of 4‐vinyl pyridine in the presence of PCL_T. The desired block copolymers were characterized by gel permeation chromatography, Fourier transform infrared spectroscopy, and NMR spectroscopy in detail. Also, the effects of the molecular weight and concentration of PCL_T on the copolymerization were investigated. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 94: 2280–2285, 2004     

亚微米级复合材料微粒合成研究

在乙醇-水混合溶剂中,用过硫酸钾(KPS)作为引发剂,通过乳液聚合作用来合成直径为375nm的聚苯乙烯(PSt)微球,并作为种子用于种子乳液聚合.用PEGm大分子单体作为稳定剂、偶氮二异丁腈作为引发剂,采用种子乳液聚合法,聚合苯乙烯和丙烯腈,制得特殊形态的亚微米尺寸的PEGm接枝共聚复合颗粒PEGm-g-PSAN.扫描电子显微镜(SEM)显示苯乙烯和丙烯腈同时促成了特殊形态.苯乙烯和丙烯腈的浓度、总单体浓度、引发剂类型和单体加入方式显著影响复合聚合物颗粒的形态.     

Dispersion polymerization of 2-hydroxyethyl methacrylate stabilized by a hydrophilic/CO2-philic poly(ethylene oxide)-b-poly(1,1,2,2-tetrahydroperfluorodecyl acrylate) (PEO-b-PFDA) diblock copolymer in supercritical carbon dioxide

Dispersion polymerization of 2-hydroxyethyl methacrylate (HEMA) has been successfully performed in supercritical carbon dioxide at P=370 bar and T=65 °C with azobis(isobutyronitrile) as initiator and a hydrophilic/CO₂-philic poly(ethylene oxide)-b-poly(1,1,2,2-tetrahydroperfluorodecyl acrylate) (PEO-b-PFDA) block copolymer as steric stabilizer. The PEO-b-PFDA (2K/21K) block copolymer was synthesized by reversible addition-fragmentation chain transfer (RAFT) polymerization. Spherical particles of poly(HEMA) were obtained in the range of 200-400 nm diameter size with a narrow particle size distribution (D_w/D_n<1.1). The effect of the stabilizer concentration on the dispersion polymerization was investigated from 20 w/w% down to 3.5 w/w% versus HEMA. Precipitation polymerization in the absence of stabilizer lead to the formation of large aggregates of partially coalesced particles whereas discrete spherical particles of poly(HEMA) were obtained by dispersion polymerization even at low concentration of PEO-b-PFDA (3.5 w/w% versus HEMA).     

Preparation of polyacrylamide aqueous dispersions using poly(sodium acrylic acid) as stabilizer

High‐solids, low‐viscosity, stable polyacrylamide (PAM) aqueous dispersions were prepared by dispersion polymerization of acrylamide in aqueous solution of ammonium sulfate (AS) using poly (sodium acrylic acid) (PAANa) as the stabilizer, ammonium persulfate (APS) or 2,2′‐Azobis (N,N′‐dimethyleneisobutyramidine) dihydrochloride (VA‐044) as the initiator. The molecular weight of the formed PAM, ranged from 710, 000 g/mol to 4,330,000 g/mol, was controlled by the addition of sodium formate as a conventional chain‐transfer agent. The progress of a typical AM dispersion polymerization was monitored with aqueous size exclusion chromatography. The influences of the AS concentration, the poly(sodium acrylic acid) concentration, the initiator type and concentration, the chain‐transfer agent concentration and temperature on the monomer conversion, the dispersion viscosity, the PAM molecular weight and distribution, the particle size and morphology were systematically investigated. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Dispersion polymerization of methyl methacrylate in supercritical carbon dioxide using a silicone‐containing fluoroacrylate stabilizer

Free radical dispersion polymerization of methyl methacrylate (MMA) was carried out in supercritical carbon dioxide (scCO₂) using poly{(heptadecafluorodecyl acrylate)‐co‐3‐[tris(trimethylsilyloxy)silyl]propyl methacrylate} (p(HDFDA‐co‐SiMA)) as stabilizer. Dry, fine powdered spherical poly(methyl methacrylate) (pMMA) particles with well‐defined sizes were produced. The resulting high yield of spherical and relatively uniform micron‐size pMMA particles was formed utilizing various amounts of p(HDFDA‐co‐SiMA) random copolymer. The particle diameter was shown to be dependent on the weight percent of the stabilizer added to the system. The effects of varying the concentration of stabilizer (1–7 wt%), reaction time (4–12 h) and pressure (15–35 MPa) upon the polymerization yield, molar mass and morphology of pMMA were investigated. Copyright © 2005 Society of Chemical Industry     

The synthesis of water soluble cationic microgels by dispersion polymerization: Their performance in kaolin deposition onto fiber

The water soluble cationic microgels (CMG), intramolecularly cross‐linked cationic polymers of acrylamide (Am) and diallyldimethylammonium chloride (DADMAC), were synthesized with dispersion polymerization in the mixture of tert‐butanol (TBA)/water in the presence N,N′‐methylene‐bisacrylamide (MBA) as the cross‐linker, poly(N‐vinylpyrrolidone (PVP) as the stabilizer and 2,2′‐azobisisobutyronitrile (AIBN) as the initiator. The effects of monomer, cross‐linker, initiator, and stabilizer concentration on both particle size and molecular weight of CMG were investigated. The well dispersed polymer particles were produced in the range of poly dispersity index 1.1–1.4 and the molecular weight distribution with bimodal. Additionally, the efficiencies of two CMGs in the clay deposition on the bleached kraft fibers were investigated and compared with commercially widely used cationic polyacrylamide (CPAM) and poly‐diallyldimethylammonium chloride (poly‐DADMAC). The experiments showed that the CMGs were found as the effective flocculation agents and their efficiencies depended on their molecular weight and charge density. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Synthesis of amphiphilic magnetic microspheres by dispersion copolymerization of styrene and poly(ethylene oxide) macromonomer

Amphiphilic magnetic microspheres ranging in diameter from 5 to 100 µm were prepared by dispersion copolymerization of styrene and poly(ethylene oxide) vinylbenzyl (PEO‐VB) macromonomer (MPEO) in the presence of Fe₃O₄ magnetic fluid. The effects of various polymerization parameters on the average particle size were systematically investigated. The average particle size was found to increase with increasing styrene concentration and initiator concentration. It also increased with decreasing stabilizer concentration and molecular weight of MPEO. The content of the hydroxyl groups localized in the microspheres ranged from 0.01 to 0.2 mmol g^?1. © 2003 Society of Chemical Industry     

Dispersion copolymerization of acrylamide with acrylic acid in an aqueous solution of ammonium sulfate: Synthesis and characterization

Dispersion copolymerization of acrylamide with acrylic acid in an aqueous solution of ammonium sulfate using poly(2‐acrylamido‐2‐methylpropanesulfonic acid sodium) as the stabilizer and ammonium persulfate (APS) as the initiator was investigated. The influence of initiator concentration, stabilizer concentration, ammonium sulfate concentration, chain‐transfer agent concentration, and polymerization temperature on the copolymerization was discussed. The results showed that varying the ammonium sulfate concentration could affect the particle size and the intrinsic viscosity of the copolymer significantly. With increasing the stabilizer concentration, the particle size of the copolymer decreased first, and then increased, meanwhile the intrinsic viscosity of the copolymer decreased. The increase of initiator concentration, chain‐transfer agent concentration, and polymerization temperature resulted in the increase in the particle size. Polydisperse spherical particles were formed in the system, and the kinetics for the dispersion copolymerization were discussed. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102: 3685–3690, 2006     

Experimental investigation of vinyl chloride drop behavior during suspension polymerization

The effects of some polymerization conditions on poly(vinyl chloride) (PVC) particles produced by the suspension polymerization process were studied on a laboratory scale. The different stages of vinyl chloride suspension polymerization were investigated experimentally by using an on-line sample withdrawal technique during reaction. It was found that the method of addition of initiator has a great effect on the PVC particle uniformity as well as the size distribution. Furthermore, when the initiator was predispersed in the continuous phase, some latex particles were formed. The effect of the type of stabilizer was also studied with two different types of PVA [partially hydrolyzed poly(vinyl acetate)]. It was found that by changing the stabilizer, the particle size, the porosity, and the morphology could change. When H80 (PVA with a degree of hydrolysis of 80% and a molecular weight of 259,000) stabilizer was used, the rigidity of the PVC particles was weak. © 1997 John Wiley & Sons, Inc. J Appl Polym Sci 65: 127–134, 1997     

The effects of acrylate monomers and polystyrene addition on the morphology of DOP‐plasticized styrene–acrylate polymer particles prepared by SPG emulsification and suspension polymerization

Fairly uniform copolymer particles of methyl acrylate (MA), butyl acrylate (BA), or butyl methacrylate (BMA) were synthesized via Shirasu porous glass (SPG) membrane and followed by suspension polymerization. After a single‐step SPG emulsification, the emulsion composed mainly of the monomers. Hydrophobic additives of dioctyl phthalate (DOP), polystyrene molecules, and an oil‐soluble initiator, suspended in an aqueous phase containing poly(vinyl alcohol) (PVA) stabilizer and sodium nitrite inhibitor (NaNO₂), were subsequently subjected to suspension polymerization. Two‐phase copolymers with a soft phase and a hard phase were obtained. The composite particles of poly(St‐co‐MA)/PSt were prepared by varying the St/PSt ratios or the DOP amount. The addition of PSt induced a high viscosity at the dispersion phase. The molecular weight slightly increased with increasing St/PSt concentration. The multiple‐phase separation of the St‐rich phase and PMA domains, observed by transmission electron microscopy, was caused by composition drift because the MA reactivity ratio is greater than that of St. The addition of DOP revealed the greater compatibility between the hard‐St and soft‐MA moieties than that without DOP. The phase morphologies of poly(St‐co‐MA), poly(St‐co‐BMA), and their composites with PSt were revealed under the influence of DOP. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 99: 1195–1206, 2006     

Formation of monodisperse polyacrylamide particles by dispersion polymerization: particle size and size distribution

Highly monodisperse polyacrylamide microparticles were directly prepared by dispersion polymerization in aqueous alcoholic media initiated by 2,2′‐azobisisobutyronitrile using poly(N‐vinylpyrrolidone) as a steric stabilizer. Monomer conversion was studied dilatometrically and polymer molecular weight was determined viscometrically. The hydrodynamic diameter of polymer particles and its distribution were measured with a dynamic laser light scattering spectrometer. The number of the nuclei produced in the early stage of the polymerization was found to be constant during the remainder of the polymerization. The influences of various polymerization parameters, such as initiator concentration, monomer concentration, stabilizer content, medium polarity, and polymerization temperature on the particle size and size distribution were systematically investigated. Copyright © 2003 Society of Chemical Industry     

Synthesis of spike‐ball‐like polystyrene/poly(methyl methacrylate) composite particles via seeded polymerization

A synthesis method for the production of novel spike‐ball‐like polymer particles is presented based on seeded dispersion polymerization of methyl methacrylate monomer in the presence of polystyrene seeds with poly(vinyl alcohol) as stabilizer and myristyl peroxydicarbonate as initiator. The particles resulting from the controlled aggregation of swollen particles during polymerization showed a salami‐like morphology with polystyrene cores and poly(methyl methacrylate) shells. The long spikes had the same morphology and were formed by the step‐by‐step addition of smaller particles on the surface of the larger particles during polymerization. The resulting particles have potential applications as templates to make micron‐sized electronics and biomaterials. © 2017 Society of Chemical Industry     

Preparation of poly(vinyl acetate) microspheres with narrow particle size distributions by low temperature suspension polymerization of vinyl acetate

To estimate influences of suspension polymerization conditions including conversion, polymerization temperature, stirring rate, initiator concentration, monomer concentration, and suspending agent concentration on the volume average diameter (D_avg) and particle size distribution (PSD) of poly(vinyl acetate) (PVAc) microspheres, vinyl acetate (VAc) was suspension‐polymerized at low temperature using 2,2′‐azobis(2,4‐dimethylvaleronitrile) as an initiator. The effects of each condition, on D_avg of PVAc microspheres, were expressed as follows, D_avg = [conversion]^a[temperature]^b[rpm]^c[ADMVN]^d[VAc]^f [suspending agent]^g. Logarithms of D_avg were linearly proportional to those of polymerization conditions, and their exponents, a, b, c, d, f, and g were calculated as 0.27, ?13.7, ?1.37, ?0.21, 0.58, and 0.29, respectively. Variations of PSDs, according to polymerization conditions, were examined by considering polymerization rate, droplet or suspension viscosity, and droplet break‐up/coagulation equilibrium. From these results, PVAc microspheres with various sizes and narrow PSDs were obtained effectively under carefully controlled polymerization conditions, which can be used as promising precursors of novel PVA microspheres through heterogeneous surface saponification. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 101: 4064–4070, 2006     

Novel synthesis of poly(methyl methacrylate) brush encapsulated silica particles

Silica (SiO₂)‐crosslinked polystyrene (PS) particles possessing photofunctional N,N‐diethyldithiocarbamate (DC) groups on their surface were prepared by the free‐radical emulsion copolymerization of a mixture of SiO₂ (diameter = 20 nm), styrene, divinyl benzene, 4‐vinylbenzyl N,N‐diethyldithiocarbamate (VBDC), and 2‐hydroxyethyl methacrylate with a radical initiator under UV irradiation. In this copolymerization, the inimer VBDC had the formation of a hyperbranched structure by a living radical mechanism. The particle sizes of such core–shell structures [number‐average particle diameter (D_n) = 35–40 nm] were controlled by the variation of the feed amounts of the monomers and surfactant, or emulsion system. The size distributions were relatively narrow (weight‐average particle diameter/D_n ≈ 1.05). These particles had DC groups on their surface. Subsequently, poly(methyl methacrylate) brush encapsulated SiO₂ particles were synthesized by the grafting from a photoinduced atom transfer radical polymerization approach of methyl methacrylate initiated by SiO₂‐crosslinked PS particles as a macroinitiator. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Concentrated emulsion copolymerization of butyl acrylate and vinyl acetate initiated by a redox initiator at lower temperature

The concentrated emulsion copolymerization of butyl acrylate and vinyl acetate with an ammonium persulfate/sodium hydrogen sulfate mixture as a redox initiator, with a sodium dodecyl sulfate/cetyl alcohol mixture as a compound surfactant, and with poly(vinyl alcohol) as a liquid film reinforcer was carried out at lower temperature. In less than 3 h, the polymerization conversion was greater than 95%. The effects of the surfactant, the initiator, the volume fraction of the monomer, and the temperature on the stability of the concentrated emulsion, the kinetic process, and the average size of the latices were examined. The morphology of the polymer particles was observed by transmission electron microscopy, and the average size and distribution of the particle diameter were measured by photon correlation spectroscopy. The kinetic equation was R_p = k[M]^0.38[I]^0.89[E]^?0.80 at 30°C (where R_p is the polymerization rate, [I] is the initiator concentration, [M] is the monomer concentration, and [E] is the concentration of the compound surfactant), and the apparent activation energy was 22.69 kJ/mol. The thin‐layer polymerization of the concentrated emulsions, which enabled the removal of the heat of polymerization, was performed first. In comparison with test‐tube polymerization, thin‐layer polymerization provided a more regular morphology of the polymer particles. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 91: 570–576, 2004     

Non‐catalyst synthesis and in vitro drug release property of poly(5,5‐dimethyl‐1,3‐dioxan‐2‐one)‐block‐methoxy poly(ethylene glycol) copolymers

A series of poly(5,5‐dimethyl‐1,3‐dioxan‐2‐one)‐block‐methoxy poly(ethylene glycol) (PDTC‐b‐mPEG) copolymers were synthesized by the ring‐opening polymerization of 5,5‐dimethyl‐1,3‐dioxan‐2‐one (DTC) in bulk, using methoxy poly(ethylene glycol) (mPEG) as initiator without adding any catalysts. The resulting copolymers were characterized by Fourier transform infrared spectra, ¹H NMR and gel permeation chromatography. The influences of some factors such as the DTC/mPEG molar feed ratio, reaction time and reaction temperature on the copolymerization were investigated. The experimental results showed that mPEG could effectively initiate the ring‐opening polymerization of DTC in the absence of catalyst, and that the copolymerization conditions had a significant effect on the molecular weight of PDTC‐b‐mPEG copolymer. In vitro drug release study demonstrated that the amount of indomethacin released from PDTC‐b‐mPEG copolymer decreased with increase in the DTC content in the copolymer. © 2013 Society of Chemical Industry     

Fe‐mediated ICAR ATRP of styrene and acrylonitrile in polyethylene glycol

In this contribution, random copolymers of p(styrene‐co‐acrylonitrile) via initiators for continuous activator regeneration (ICAR) in atom transfer radical polymerization (ATRP) (ICAR ATRP) of styrene and acrylonitrile (SAN) were synthesized at 90°C in low molecular weight polyethylene glycol (PEG‐400) using CCl₄ as initiator, FeCl₃·6H₂O as catalyst, succinic acid as ligand and thermal radical initiator azobisisobutyronitrile (AIBN) as thermal free radical initiator. In this system, well‐defined copolymer of SAN was achieved. The kinetics results showed that the copolymerization rate obeyed first‐order kinetics model with respect to the monomer concentration, and a linear increase of the molecular weights with the increasing of monomer conversion with narrow molecular weight distribution was observed in the range of 1.1–1.5. The conversion decreased with increasing the amount of FeCl₃·6H₂O and increased with increasing the molar ratio of [St]₀/[AN]₀/[CCl₄]₀ and temperature. AIBN has a profound effect on the polymerization. The activation energy was 55.67 kJ mol^?1. The living character of copolymerization was confirmed by chain extension experiment. The resultant random copolymer was characterized by ¹H‐NMR and GPC. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40135.