Influence of particle diameter on the morphology of micron-sized, monodispersed composite polymer particles produced by seeded polymerization for the dispersion of highly monomer-swollen polymer particles

 Micron-sized, monodispersed polystyrene (PS)/poly (n-butyl methacrylate) (PBMA) composite particles, in which the PS domain(s) were dispersed in a PBMA continuous phase, were produced by seeded polymerization for dispersions of n-butyl methacrylate (BMA) swollen PS particles in a wide range of PS/BMA ratios in the presence of NaNO₂ as a water-soluble inhibitor. Moreover, in order to change the diameter of the composite particles at same PS/BMA ratio, PS/PBMA (1/150 w/w) composite particles were produced using five kinds of PS particles in a range of diameters from 0.64 to 3.27 μm as seeds. The percentages of the PS/PBMA composite particles having double and triple and over PS domains, which were thermodynamically unstable morphologies, increased with the increase in the diameter of BMA swollen PS particles. There was a clear influence of the size of the swollen particles on the morphology of the PS/PBMA composite particles produced. Received: 30 September 1999/Accepted: 18 April 2000     

Production of micron-sized monodispersed core/shell composite polymer particles by seeded dispersion polymerization

 The effect of the weight ratio of seed polymer/monomer on the morphology of the poly(methyl methacrylate) (PMMA)/polystyrene (PS) monodispersed composite particles produced by batch seeded dispersion polymerization of styrene with 1.64-μm-sized monodispersed PMMA seed particles in a methanol/water medium (4/1 w/w) was examined. In the PMMA/PS weight ratios of 3/1 and 2/1, the composite particles had a clear morphology consisting of a PMMA core and a PS shell. In the ratio of 1/1, a lot of small PS domains were observed in the PMMA core though the PS shell was still formed. By stepwise addition of styrene monomer, the formation of the small PS domain was depressed and complete core/shell morphology was formed. Absorption/release treatments of toluene into/from the PMMA/PS (1/1 w/w) composite particles resulted in a drastic morphological change from the core/shell structure to a multi- layered one. Received: 2 February 1999 Accepted in revised form: 7 April     

Production of micron-sized, monodisperse composite polymer particles having epoxy groups by seeded dispersion polymerization

 Micron-sized, monodisperse polystyrene (PS)/glycidyl methacrylate–divinylbenzene copolymer core/shell composite particles having epoxy groups in the shells were produced by seeded dispersion copolymerization of glycidyl methacrylate and divinylbenzene in an ethanol/water medium with 1.65-μm-sized, monodisperse PS seed particles. By chemical modifications of epoxy groups with sodium hydrogensulfite and dimethylamine, composite polymer particles having sulfonate and dimethylamino groups, respectively, in the shells were prepared. Received: 13 September 2000 Accepted: 31 January 2001     

Production of micron-sized, monodispersed, multilayered composite polymer particles by multistep seeded dispersion polymerization

 Micron-sized, monodispersed, poly(methyl methacrylate) (PMMA)/polystyrene (PS)/PMMA/PS multilayered composite particles were successfully produced by three-step seeded dispersion polymerizations in methanol/water media. The first seeded dispersion polymerization was carried out with 2-μm-sized, monodispersed PMMA particles.     

Morphology of anomalous polystyrene/ polybutyl acrylate composite particles produced by seeded emulsion polymerization

 Recently, we found that “golf ball”-like polystyrene (PS)/polybutyl acrylate (PBA) composite particles could be produced by seeded emulsion polymerization of butyl acrylate (BA) with PS seed particles. In this article, the effects of the polymerization temperature, BA monomer concentration, and the presence of 1-octanol, which is a good solvent for PBA and a poor solvent for PS in the polymerization, on the morphology was studied. Received: 25 February 1997 Accepted: 4 October 1997     

Morphology of micron-sized monodispersed composite polymer particles produced by seeded polymerization for the dispersion of highly monomer-swollen polymer particles

 Monodispersed polystyrene (PS)/poly(n-butyl methacrylate) (PBMA) composite particles having 9.4 μm in diameter were produced by seeded polymerization for the dispersion of highly n-butyl methacrylate (BMA)-swollen PS particles, and their morphologies were examined. The highly BMA-swollen PS particles (about 150 times the weight of the PS seed particles) were prepared by mixing monodispersed 1.8 μm-sized PS seed particles and 0.7 μm sized BMA droplets prepared with an ultrasonic homogenizer in ethanol/water (1/2, w/w) medium at room temperature. After NaNO₂ aqueous solution as inhibitor was added in the dispersion, the seeded polymerization was carried out at 70 °C. In an optical microscopic observation, one or two spherical high contrast regions which consisted mainly of PS were observed inside PS/PBMA composite particles. In the PS domain, there were many fine spherical PBMA domains. Such morphologies were based on the phase separation of PS and PBMA within the homogeneous swollen particles during the seeded polymerization. Received: 04 June 1997 Accepted: 27 August 1997     

Influence of the swelling state of seed polymer particles with monomer on the morphology of micron-sized monodispersed composite polymer particles produced by seeded polymerization utilizing the dynamic swelling method

 Micron-sized mono-dispersed polystyrene (PS)/poly(n-butyl methacrylate) (PBMA) composite particles (PS/PBMA=2/1 by weight) having a heterogeneous structure in which many fine PBMA domains dispersed in a PS matrix near the particle surface were produced by seeded polymerization of n-butyl methacrylate (BMA) of which almost all had been absorbed by 1.8 μm-sized monodispersed PS seed particles utilizing the dynamic swelling method. The morphology was varied by changing the PS/BMA ratio and polymerization temperature. It was concluded that the swelling state of 2 μm-sized BMA-swollen PS particles in the seeded polymerization process is one of the important factors to control the morphology of the composite particles. Received: 27 November 1996 Accepted: 21 March 1997     

Preparation of polymer particles having ethyleneurea groups at their surfaces by emulsifier-free seeded emulsion polymerization and wet adhesion of its emulsion film

Polymer emulsion having ethyleneurea groups at particle surfaces was produced by emulsifier-free seeded emulsion copolymerization of n-butyl methacrylate (BMA) and methacrylamide ethylethyleneurea (EU) with poly(BMA) seed particles utilizing the starved-fed monomer addition method. This emulsion film, prepared by casting the polymer emulsion on an alkyd resin plate, had a superior adhesion in water, as well as on stainless steel. Such superior wet adhesions seem to be based on a large amount of EU predominantly localized at the particle surfaces.Part CCXLIX of the series "Studies on suspension and emulsion"     

Estimation of surface morphology of composite polymer particles prepared by the stepwise heterocoagulation method with ζ-potential measurement

 Core-shell composite polymer particle was prepared by the stepwise heterocoagulation of cationic small polymer particles (SPs) onto an anionic large polymer particle (LP), following heat treatment at temperatures which were higher than glass transition temperature (T _g=18 °C) of SP. At pH 9 ζ-potential of the hetero-coagulated particle (HP) was negative, but it changed to positive by the heat treatment and increased with the treatment time and finally attained to that of SP. The treatment time to attain the ζ-potential of SP became short by elevating the treatment temperature. This indicates that during the heat treatment, SP continued to melt on the surface of LP and finally formed a continuous shell. Received: 3 September 1997 Accepted: 29 October 1997     

Production of micron-sized monodispersed composite polymer particles by seeded polymerization utilizing the dynamic swelling method

 In order to develop the seeded polymerization technique utilizing the dynamic swelling method (DSM) proposed by authors for the production of micron-sized mono-dispersed “composite” polymer particles consisting of two kinds of polymers, the seeded polymerization for the dispersion of ethyl methacry-late (EMA)-swollen PS particles prepared utilizing DSM was carried out. Monodispersed PS/poly(ethyl methacrylate) (PEMA) composite particles having 7 μm in diameter were produced by the addition of NaCl to lower the solubility of EMA in medium and by the addition of CuCl₂ as a water-soluble inhibitor to depress the by-production of submicron-sized PEMA particles. Received: 16 July 1996 Accepted: 10 October 1996     

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     

Synthesis of submicron-sized peanut-shaped poly(methyl methacrylate)/polystyrene particles by seeded soap-free emulsion polymerization

Submicron-sized peanut-shaped poly(methyl methacrylate)/polystyrene(PMMA/PS) particles were successfully synthesized by seeded soap-free emulsion polymerization of styrene on the spherical crosslinked PMMA seed particles.The obtained peanut-shaped particles showed a novel internal morphology:PS phase formed one domain which linked to the other domain having PMMA core encased by PS shell.     

Micron-sized monodispersed polymer particles produced by seeded polymerization for the dispersion of high swelling of polymer particles with a large amount of monomer

 Micron-sized monodispersed polystyrene (PS)/poly(n-butyl methacrylate) composite particles were produced as follows. First, 1.77 μm-sized monodispersed PS seed particles produced by dispersion polymerization were dispersed in ethanol/water (1/2, w/w) medium dissolving poly(vinyl alcohol) as a stabilizer. n-Butyl methacrylate (BMA) monomer dissolving benzoyl peroxide initiator was emulsified in ethanol/water (1/2, w/w) solution of sodium dodecyl sulfate as emulsifier with ultrasonic homogenizer, and the BMA monomer emulsion was mixed with the PS seed emulsion. The PS seed particles absorbed with a large amount of BMA (about 150 times weight of the seed particles) for 2 h to about 10 μm in diameter while keeping good monodispersity and BMA droplets disappeared finally. The seeded polymerization was carried out at 70 °C after a certain amount of water was added to depress the redissolving of BMA from the swollen particles into the medium by raising from room temperature to the polymerzation temperature. Received: 21 February 1996 Accepted: 4 September 1996     

Production of hollow polymer particles by suspension polymerization

 Polymer particles having single hollow in the inside were successfully prepared by suspension polymerization for divinylbenzene/ toluene droplets dissolving polystyrene (PS) in an aqueous solution of poly(vinyl alcohol). Such a hollow polymer particle was not obtained without PS. The hollow structure was affected by the molecular weight and the concentration of PS. Received: 3 December 1997 Accepted: 27 March 1998     

Monodisperse glycidyl-functional polymer particles in the micron-size range by seeded polymerization

Polymer particles having glycidyl ether groups were prepared through seeded polymerization in aqueous medium. The polystyrene seed particles were swollen with a mixture of n-butyl methacrylate, glycidyl methacrylate, ethylene glycol dimethacrylate, and benzoyl peroxide initiator. The particles produced after polymerization were characterized regarding the particle morphology and functionality. Optical microscopy and scanning electron microscopy showed that the particles are in the size range of 13–14 μm and are highly monodisperse with heterophase structures. Actually, the high content of glycidyl methacrylate in the second monomer mixture caused the particle phase to be homogeneous. This effect was explained in terms of the surface tension of each polymer phase. Moreover, the cross-linking of the seed particles had a significant effect on the final particle morphology. From the HCl–dioxane back titration method, it was found that about 20–30% of glycidyl ether groups still remained on the final particles. Received: 25 February 2000 Accepted: 10 November 2000     

Preparation of multihollow polystyrene particles by seeded emulsion polymerization using seed particles with incorporated nonionic emulsifier: effect of temperature

Seeded emulsion polymerizations of styrene using polystyrene (PS) seed particles with incorporated nonionic emulsifier were carried out at 40 and 70 °C to investigate the influence of temperature during the polymerization process including the swelling step of the seed particles with monomer on the formation of multihollow PS particles. An increase in the temperature during the polymerization process caused an increase in the rate of coalescence (i.e., the degree of coalescence at any given time) of the small water domains in the inside. After the coalescence proceeded excessively, the water domains were eventually discharged from the particles to the medium, resulting in nonhollow particles. The results show that it is important for the preparation of the multihollow PS particles to control the coalescence of a lot of small water domains inside the seed particles with the incorporated nonionic emulsifier, and strongly support the formation mechanism previously proposed. Part CCCXX of the series “Studies on Suspension and Emulsion”.     

Production of anomalously shaped carboxylated polymer particles by seeded emulsion polymerization

Anomalous polymer particles with a partial protuberance like octopus ocellatus were produced under alkaline conditions by seeded emulsion copolymerization for styrene and butyl acrylate, with styrene-butyl acrylate-methacrylic acid terpolymer emulsion as seed. The mechanism of production of the polymer particles was studied. By transmission electron microscopic observation of the particles at each conversion, it was observed that the anomalous polymer particles were produced by partial growth of each of the individual seed particles throughout polymerization. Ionization of the carboxyl groups and low viscosity in the growing particles during the process of polymerization were important factors for partial growth.Part CIII of the series Studies on Suspension and Emulsion.     

Synthesis of temperature-sensitive micron-sized monodispersed composite polymer particles and its application as a carrier for biomolecules

 Temperature-sensitive micron-sized monodispersed composite polymer particles were prepared by seeded copolymerization of dimethylaminoethyl methacrylate and ethylene glycol dimethacrylate with 1.77 μm-sized monodispersed polystyrene seed particles. The change in surface property at temperature above and below 35 °C was examined by differential scanning calorimetry, trypsin activity and the adsorption/ desorption behaviors of low molecular weight cationic emulsifier as well as biomolecules. Received: 6 August 1997 Accepted: 16 January 1998     

Reconstruction of morphology of micron-sized,monodisperse composite polymer particles by the solvent-absorbing/releasing method

Micron-sized, monodisperse polystyrene (PS)/poly(n-butyl methacrylate) (PBMA) (2/1 w/w) composite particles having different morphologies were prepared by the solvent-absorbing/releasing method (SARM). There was an obvious influence of the releasing rate of toluene from the toluene-swollen composite particles on the reconstructed morphology by the SARM. In the case of fast release, the reconstructed morphology was a bicontinuous structure that is similar to that formed by spinodal decomposition. On the other hand, in the case of slow release, a hemispherical structure was formed that consisted of PS and PBMA phases.Part CCLIV of the series Studies on Suspension and Emulsion