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.     

Synthesis of micron-sized poly(styrene-<Emphasis Type="Italic">co</Emphasis>-divinylbenzene) hollow particles from seeded emulsions by using swelling solvents

Hollow micron-sized poly(styrene-co-divinylbenzene) particles were produced in seeded emulsions in the presence of swelling solvents. The size and morphology of the resulting polymer particles can be altered by varying swelling solvent in seeded polymerization at elevated temperature. The effects of swelling agents, including hydrophobic solvents, hydrophilic solvents and solvent mixtures, on the microstructure of particles were investigated. The formation of hollow poly(styrene-co-divinylbenzene) particles depended significantly on a fast and effective phase separation between the cross-linked shell and the swollen core, that occurred only in the presence of an appropriate swelling solvent.     

Synthesis and properties of soap-free poly(methyl methacrylate-ethyl acrylate-methacrylic acid) latex particles prepared by seeded emulsion polymerization

In order to obtain functional polymer latex particles with clean surface and with surface carboxyl groups, P(MMA-EA) seed particles with the diameter of 335 nm were first synthesized via soap-free batch emulsion polymerization of methyl methacrylate (MMA) and ethyl acrylate (EA), and then the seeded emulsion copolymerization of MMA, EA and MAA (methacrylic acid) onto the seed particles were performed in the absence of emulsifier. Influences of ingredients and conditions on polymerization, latex particle size (D_p) and its distribution were investigated. Results showed that most of the monomers polymerized onto the seed latex particles in the second step of polymerization by using drop-wise addition method, and D_p increased from 483 nm to 829 nm with the mass ratio of core/shell monomers [C]/[S] decreased from 1:2 to 1:15. It was found that D_p decreased with the increase of MAA and initiator amounts, and the size of the latex particles became uniform with the decrease of MAA amount and with the increase of [C]/[S] value.     

Preparation of sulphonate-containing polymer particles <Emphasis Type="Italic">via</Emphasis> semi-continuous emulsion copolymerizaion of styrene and sodium styrene sulphonate

Submicron-sized P(St-NaSS) latexes were prepared via a semi-continuous emulsion copolymerization of styrene (St) and sodium styrene sulphonate(NaSS) in the presence of anionic surfactant,in which NaSS aqueous solution and St were separately dropwise charged into the polymerization system at the same time.The hydrodynamic diameter of the latex particles was measured by dynamic light scattering(DSL) method,and the NaSS unit content of the purified copolymer by water extraction was calculated based on the elementary analysis.Results showed that the copolymerization could be performed smoothly with the monomer conversion more than 96%in the absence of crosslinker,and PNaSS homopolymer could be removed from the latex product by water extraction for 28 h.The weight loss in the water extraction tended to decrease and the NaSS unit content of the purified copolymer tended to increase with the increase of monomer feeding time, and both of them increased with the increase of NaSS/St mole ratio in the charge.The introduction of divinyl benzene (DVB) could decrease the weight loss in the water extraction and increase the NaSS unit content of the purified copolymer. When 25/75 mole ratio of NaSS/St and 11 mol%DVB of total NaSS and St were used in the recipe,and the monomer feeding time was 3 h in copolymerization,the NaSS unit content of the purified copolymer reached 7.31 mol%.     

Effect of the polymerization parameters on the morphology and spherical particle size of poly(styrene-<Emphasis Type="Italic">co</Emphasis>-divinylbenzene) prepared by precipitation polymerization

Poly(styrene-co-divinylbenzene) microspheres having a diameter range of 3.0–4.5 µm were synthesized by precipitation polymerization under various conditions, then the effects of the polymerization parameters such as monomer and initiator concentration, and used cosolvents on the characteristics of the final particles were compared with those in dispersion polymerization. It was found that precipitation polymerization is more sensitive to polymerization conditions than dispersion polymerization, and that precise control of polymerization parameters is therefore essential for individually stable spherical particles. Monomer and initiator concentration, and the use of cosolvents significantly vary the morphology and the size of the final particles. However, the uniformity of the microspheres is not greatly affected by the polymerization parameters.     

Preparation of sulphonate-containing core/shell latex particles via seeded emulsion copolymerization

<正>In this study,P(St-MAA) seed latex particles were first prepared via soap-free emulsion polymerization of styrene(St) and methacrylic acid(MAA),then the seed particles were allowed to swell with St at room temperature,and the P(St-MAA)/P(StNaSS) core/shell latex particles were then synthesized via seeded emulsion copolymerization of St and sodium styrene sulphonate (NaSS) using AIBN as initiator in the presence of N,N'-methylenebisacrylamide(BAA,water-soluble crosslinker).Results showed that the polymerization could be carried out smoothly when the ratio of BAA to total monomers was less than 3 mol%,the narrow dispersed P(St-MAA) seed particles with the diameter of 150 nm and the P(St-MAA)/P(St-NaSS) core/shell latexes with the particle size of about 200 nm were synthesized.When the 25/75 mole ratio of NaSS/(St + MAA) and 2 mol%of BAA were used in the seeded emulsion polymerization,the resulted P(St-MAA)/P(St-NaSS) latex product showed a low weight loss after water extraction,and the NaSS unit content in the whole particle and in the shell reached 11.7 mol%and 34.6 mol%,respectively.     

Enhanced thermal properties of highly monodispersed ZnO nanoparticle/poly(styrene-<Emphasis Type="Italic">co</Emphasis>-acrylonitrile) nanocomposite

Chemical based approach for the synthesis of poly(styrene-co-acrylonitrile)/ZnO nanocomposites with different ZnO nanoparticle content by in situ emulsion polymerization is discussed. A significant increase in the thermal degradation temperature, melting and crystallization temperatures in all nanocomposite is observed. Increasing ZnO loading to polymer matrix enhances the flame retardant ability of polymer matrix with an appreciable increase in thermal degradation temperature of pristine polymer.     

Preparation of ASA (acrylonitrile-styrene-acrylate) structural latexes via seeded emulsion polymerization

Acrylonitrile-styrene-acrylate (ASA) structural latexes were synthesized in a two-stage seeded emulsion polymerization. In the first-stage, partially cross-linked poly (n-butyl acrylate) (PnBA) and poly (n-butyl acrylate-stat-2-ethyl hexyl acrylate) P (nBA-stat-2EHA) (75/25 by wt) rubber cores were synthesized, and then in the second-stage, a hard poly (styrene-stat-acrylonitrile) (SAN) (70/30 by wt) shell was grafted on to the rubber seeds. The effects of surfactant type and second-stage monomer addition mode have been investigated on the final morphology of two-stage emulsion particles. The results indicated that an application of anionic surfactant, that is, sodium dodecyl sulfonate (SDS), along with sodium persulfate (KPS) initiator for both stages, and with first-stage tert-butyl hydroperoxide (t-BHP) and second-stage KPS initiators led to a hemisphere particle morphology. On the other hand, raspberry and core-shell structures were observed for the structural latexes, which were prepared using a non-ionic surfactant, that is, nonylphenol ethoxylated polyethylene glycol (Igepal CO-850), accompanying KPS initiator for both stages. It is clear, however, that the relative surface hydrophilicity of the core phase, altered by the surfactant type considerably affected the type of morphology formed. For obtained structural latexes, the gradual addition of the second-stage monomers to the core latexes resulted in a fairly real core-shell structure with a higher shell thickness. On the contrary, a raspberry structure in which the rubber phase was enlarged by the second-stage polymer microdomains was observed for the second-stage monomer addition batch. In fact, the shell semi-batch polymerization conditions lower the shell plasticizing effect, and increase the kinetic barrier to prevent from further second-stage monomer diffusion and microdomain formation within the rubbery phase.     

Novel Preparation of Monodisperse Poly(styrene-<Emphasis Type="Italic">co</Emphasis>-divinylbenzene) Microspheres by Controlled Dispersion Polymerization

Poly(styrene-co-divinylbenzene) particles possessing uniform properties are attractive for various chromatographic applications. However, their preparation by dispersion polymerization is rather complicated. Our aim was to prepare monodisperse PS microspheres by dispersion polymerization of styrene with controlled addition of 1 wt % of divinyl benzene. The reaction occurs in a mixture of ethanol with 2-methoxyethanol or 2-ethoxyethanol and is stabilized and initiated by hydroxypropyl cellulose and dibenzoyl peroxide, respectively. The effects of the medium polarity based on changing of the solvent mixture ratio and several modes of divinyl benzene addition, including simple one-shot and continuous divinyl benzene post-addition, on the particle size and morphology are investigated. Slow continuous dosing of 1 wt % of divinyl benzene one hour after the start of the styrene polymerization produce monodisperse spherical PS particles 5.4 μm in size. Such microspheres might be suitable as precursor for a solid adsorbent for harmful and carcinogenic organic vapors.     

Investigation of cationic soapless P(St-<Emphasis Type="Italic">co</Emphasis>-DMAEMA) latex and its electrostatic adsorption of laponite

Cationic poly(styrene-co-N,N-dimethylaminoethyl methacrylate) (P(St-co-DMAEMA)) latexes were prepared in the absence of surfactant by using 2,2’ -azobis (2-methylpropionamidine) dihydrochloride (AIBA) as the initiator. The effects of the AIBA concentration, HCl/DMAEMA molar ratio and DMAEMA amount on the emulsion polymerization and the latex properties were investigated. The particle morphology and size, the zeta potential and the amino distribution of the P(St-co-DMAEMA) latexes were characterized by transmission electron microscope (TEM), dynamic light scattering (DLS) and conductometric titration, respectively. Results showed that the emulsion polymerization performed smoothly with high monomer conversion and narrow particle size distribution under the optimized conditions with AIBA concentration of 1 wt%, HCl/DMAEMA molar ratio of 1.2 and DMAEMA content of 5 wt%. The diameter of the dried latex particles decreased and the density of amino groups on the particle surfaces increased with increasing the DMAEMA content. The zeta potential of the P(St-co-DMAEMA) latexes was pH-dependent and the zero point was around at pH 7.2. A facile method was developed to fabricate P(St-co-DMAEMA)/laponite hybrid nanoparticles via electrostatic adsorption, in which the loading capacity of laponite platelets reached 17.7 wt%, and the resultant hybrid nanoparticles showed good thermal stability.     

Preparation,characterization and morphological study of poly(<Emphasis Type="Italic">m</Emphasis>-toluidine-<Emphasis Type="Italic">co</Emphasis>-<Emphasis Type="Italic">m</Emphasis>-aminoacetophenone) conductive copolymer

A new series of copolymers of poly(m-toluidine-co-m-aminoacetophenone) were synthesized by the chemical oxidative method in acid medium. The copolymers were characterized by UV–Vis and FTIR spectroscopy. X-ray diffraction analysis revealed the partial crystalline nature of copolymer. The morphological study by SEM analysis indicated that the surface of the copolymer had the granular structure of agglomerated morphology with average particle size of 200 nm. The conductivity of the copolymers ranged from 2 × 10^–4 to 3.3 × 10^–8 S/cm and the conductivity decreased with the increase of comonomer concentration. The resultant copolymers showed an enhanced solubility and an improved processability when compared with pure polyaniline.     

Preparation and polymerization mechanism of dihydroxy-capped PCL,poly(CL-<Emphasis Type="Italic">b</Emphasis>-PEG-<Emphasis Type="Italic">b</Emphasis>-CL) and poly(DTC-<Emphasis Type="Italic">b</Emphasis>-CL-<Emphasis Type="Italic">b</Emphasis>-DTC)

The ring opening polymerization of ε-caprolactone (CL) was initiated by glycol and yttrium tri(2,6-di-tert-butyl-4-methylphenolate)s (Y(OAr)₃), preparing dihydroxy-capped poly (ε-caprolactone) (PCL) with controllable molecular weight. ¹H NMR and SEC analyses indicate that two kinds of active species and corresponding PCL with different structures exist in the system. Increasing the ratio of glycol to Y(OAr)₃ benefits the formation of monofunctional active species. However, poly(ethylene glycol) (PEG)/Y(OAr)₃ system only contains sole bifunctional active species to synthesize copolymer of CL with PEG (poly(CL-b-PEG-b-CL)). Dihydroxycapped PCL as macroinitiator can further initiate the polymerization of 2,2-dimethyltrimethylene carbonate (DTC). Thus, triblock copolymer of CL with DTC (poly(DTC-b-CL-b-DTC)) has been prepared.     

Potential of poly(styrene-<Emphasis Type="Italic">co</Emphasis>-divinylbenzene) monolithic columns for the LC-MS analysis of protein digests

Two polystyrene-based capillary monolithic columns of different length (50 and 250 mm) were used to evaluate the effects of column length on gradient separation of protein digests. A tryptic digest of a 9-protein mixture was used as a test sample. Peak capacities were determined from selected extracted ion chromatograms, and tandem mass spectrometry data were used for database matching using the MASCOT search engine. Peak capacities and protein identification scores were higher for the long column with all gradients. Peak capacities appear to approach a plateau for longer gradient times; maximum peak capacity was estimated to be 294 for the short column and 370 for the long column. Analyses with similar gradient slope produced a ratio of the peak capacities of 3.36 for the long and the short column, which is slightly higher than the expected value of the square root of the column length ratio. The use of a longer monolith improves peptide separation, as reflected by higher peak capacity, and also increases protein identification, as observed from higher identification scores and a larger number of identified peptides. Attention has also been paid to the peak production rate (PPR, peak capacity per unit time). For short analysis times, the short column produces a higher PPR, while for analysis times longer than 40 min, the PPR of the 250-mm column is higher.     

Crystallization behavior and hydrophilicity of poly (vinylidene fluoride) (PVDF)/poly (styrene-<Emphasis Type="Italic">co</Emphasis>-acrylonitrile) (SAN) blends

Poly (styrene-co-acrylonitrile) (SAN) is a hydrophilic non-crystalline copolymer, which is initially used in this paper to improve the hydrophilicity of poly (vinylidene fluoride) (PVDF). Investigation of the crystallization behavior of PVDF/SAN blends showed that the samples presented only α phase regardless of SAN content as cooling from the melt. A double-melting phenomenon was related to the perfection or crystal size of PVDF crystals. As the SAN content is increasing, crystallization of PVDF was limited, leading to a decreased crystallinity and lamellar growth. Besides, the hydrophilicity of PVDF was improved by blending with SAN. The sample containing 70 wt.% SAN performed a similar surface property of the neat SAN owing to the besieging of the PVDF phase by SAN. Observed from the cross section of the blends, PVDF/SAN blends were partially miscible with less than 50 wt.% SAN addition. As the SAN content was more than 50 wt.%, the crystalline PVDF particles clearly dispersed in the amorphous matrix.     

Nanocomposite particles with core-shell morphology IV: an efficient approach to the encapsulation of Cloisite 30B by poly (styrene-<Emphasis Type="Italic">co</Emphasis>-butyl acrylate) and preparation of its nanocomposite latex via miniemulsion polymerization

In this work, miniemulsion polymerization was applied for encapsulation of Cloisite 30B, an organically modified montmorillonite, inside poly (styrene-co-butyl acrylate) nanocomposite through an efficient and optimized procedure. The primary miniemulsions were prepared by dispersing Cloisite 30B in the monomers mixture (styrene and butyl acrylate) in the presence of sodium dodecyl sulfate and Span 80 as surfactants and hexadecane as costabilizer by using ultrasonication. The stability of both miniemulsion and the obtained latex depends on premixing procedures, time and pulsed cycle of ultrasonication, and more importantly on the applied surfactants. The synthesized products were characterized by dynamic light scattering, X-ray diffraction, transmission electron microscopy, scanning electron microscopy, induced coupled plasma, and Zeta potential measurement. Its prepared film shows an excellent transparency, which is indicative of full exfoliation of Cloisite 30B platelets by poly (styrene-co-butyl acrylate) latex particles through miniemulsion polymerization technique with 73% efficiency. No armored latex particle was observed.     

Synthesis and properties of organic-inorganic hybrid P(NIPAM-<Emphasis Type="Italic">co</Emphasis>-AM-<Emphasis Type="Italic">co</Emphasis>-TMSPMA) microgels

Utilizing the hydrolysis and condensation of the methoxysilyl moieties, organic-inorganic hybrid poly(N-isopropylacrylamide-co-acrylamide-co-3-(trimethoxysilyl)propylmethacrylate) P(NIPAM-co-AM-co-TMSPMA) microgels were prepared via two different methods. The first method was that the microgels were post-fabricated from the crosslinkable linear P(NIPAM-co-AM-co-TMSPMA) terpolymer aqueous solutions above the lower critical solution temperature (LCST) of the terpolymer. For the second method, the microgels were directly synthesized by conventional surfactant free emulsion copolymerization of NIPAM, AM, and TMSPMA. The hydrodynamic diameter and stability of the resultant P(NIPAM-co-AM-co-TMSPMA) microgels strongly depend on the pH and temperature of the microgel aqueous solution. The hydrodynamic diameters of the microgels decreased with increasing the measuring temperature. The phase transition temperature of the microgels was found to be around 34°C, which was independent of the initial terpolymer concentration and shifted to lower temperature with increasing the preparation temperature. Increasing the initial amount of AM will enhance the instability of the microgels at high pH values. Moreover, the P(NIPAM-co-AM-co-TMSPMA) microgels obtained from the linear terpolymer had more homogeneous microstructures as compared with the corresponding NIPAM/AM/TMSPMA microgels prepared by one step emulsion copolymerization as revealed by light scattering measurements.     

Novel terpolymers of poly(<Emphasis Type="Italic">p</Emphasis>-dioxanone-<Emphasis Type="Italic">co</Emphasis>-trimethylene carbonate-<Emphasis Type="Italic">co</Emphasis>-L-phenylalanine): Synthesis,characterization, thermal properties and copolymerization mechanism

In order to exploit the biological functions of materials, a series of new random terpolymers were synthesized by the ring-opening polymerization of p-dioxanone, trimethylene carbonate, and L-phenylalanine N-carboxyanhydride (L-Phe- NCA) in the presence of stannous octoate. The terpolymers were characterized by ¹H-NMR, ¹³C-NMR, FTIR, and gel permeation chromatography. The effects of the reactant ratio, catalyst dosage, reaction temperature and time on the copolymerization were investigated, and were found to regulate the composition of the terpolymer. Increases in the reaction temperature, polymerization time, L-Phe-NCA monomer amount, and catalyst content generated a product with a slightly decreased molecular weight. The crystallinity of the terpolymer was investigated by differential scanning calorimetry and polarized optical microscopy. A reasonable mechanism for the polymerization was proposed based on the obtained results.     

Horseradish peroxidase-catalyzed polymerization of<Emphasis Type="Italic"> p</Emphasis>-hydroxycinnamic acid for synthesis of reactive microspheres

In this article, we report the experimental synthesis of reactive polymer microspheres of poly(p-hydroxycinnamic acid). Enzyme-catalyzed polymerization of poly(p-hydroxycinnamic acid) using horseradish peroxidase as a catalyst and hydrogen peroxide as an oxidant took place in a mixture solution of methanol and phosphate buffer solution; it was found that the fraction of methanol in the mixture solution strongly affected the yield of powdery polymer materials. The chemical structure of the polymers was characterized by ¹H-NMR and FT-IR spectroscopies, and the molecular weight was measured by gel permeation chromatography. The ¹H-NMR chart of the obtained polymer was almost the same as that of the monomer; FT-IR spectra indicated the existence of carboxyl groups. The weight-average molecular weight of the soluble part in tetrahydrofuran was found to be 1,451. Dispersion polymerization of p-hydroxycinnamic acid was carried out in a mixture solution of methanol and phosphate buffer solution by adding a dispersion stabilizer. Of the several such polymers tested, poly(vinyl alcohol) was found to be the most effective in producing reactive poly(p-hydroxycinnamic acid) microspheres.     

Synthesis,characterisation, and electrical properties of novel nanostructured conducting poly(aniline-<Emphasis Type="Italic">co</Emphasis>-<Emphasis Type="Italic">m</Emphasis>-chloroaniline) with incorporated silver particles

Novel copolymers of poly(aniline-co-m-chloroaniline)-doped dodecylbenzenesulphonic acid (DBSA) with embedded silver nanoparticles were synthesised using the in situ chemical oxidative method. The structural properties of the copolymers were characterised using the UV-VIS and FTIR spectroscopic methods. The crystalline nature of the copolymer was demonstrated by way of the X-ray diffraction (XRD) pattern. Scanning electron microscopy (SEM) revealed the presence of particle agglomerates measuring 50 nm to 100 nm on the surface of the nanocomposites. The electrical conductivity of the copolymer was dependent on the monomer composition and was found to be in the range of 10^?2 S cm^?1 to 10^?6 S cm^?1 with an increasing chloroaniline content and exhibiting improved solubility.     

The influence of the synthesis pressure on the chromatographic properties of poly(divinylbenzene-<Emphasis Type="Italic">co</Emphasis>-ethylvinylbenzene-<Emphasis Type="Italic">co</Emphasis>-2-hydroxyethyl methacrylate) monolithic columns

Monolithic columns based on copolymer of divinylbenzene (DVB), ethylvinylbenzene (EVB), and 2-hydroxyethyl methacrylate (HEMA) were prepared and applied to the separation of low-molecular-weight aromatic compounds. The monoliths were synthesized via thermally initiated free-radical polymerization in confines of stainless steel tubes with dimensions of 100 × 4.3 mm. In order to compensate for the polymer shrinkage during the synthesis and prevent the monolith from detachment from the column wall, the polymerization was conducted under nitrogen pressure. The excess pressure was varied from 0 bar to 9 bar. The synthesis under pressure was shown to improve the peak shapes and column efficiency in comparison with the synthesis in the closed tube. The optimum pressure for poly(DVB-co-EVB-co-HEMA) monoliths was found to be 3 bar. The efficiency of the column obtained at 3 bar is 13 500 TP/m for propylbenzene (k′ = 6) and 38 300 TP/m for uracil (k′ = 0).