Soap-free Emulsion Copolymerization Research Articles

The preparation of monodisperse P(St-BA-MAA)@disperse dye microspheres and fabrication of patterned photonic crystals with brilliant structural colors on white substrates

The black disperse dye and poly (styrene-butyl acrylate-methacrylic acid) (P(St-BA-MAA)) seed microspheres synthesized by soap-free emulsion copolymerization are regarded as main components to prepare P(St-BA-MAA)@disperse dye composite microspheres (@ means the dye is loaded on the microsphers). The influences of the concentrations of disperse dye, the concentrations of P(St-BA-MAA) seed microspheres and the preparation temperature on diameters and monodispersity of P(St-BA-MAA)@disperse dye microspheres are deeply investigated, and the prepared P(St-BA-MAA)@disperse dye microspheres are acted as the structural units to construct photonic crystals with structural colors on fabric substrates by ink-jet printing technology. Especially, the resultant photonic crystals and structural colors are detailedly characterized, and the comparison of self-assembly effect between P(St-BA-MAA)@disperse dye microspheres and pure P(St-BA-MAA) microspheres are depicted. The results showed that the monodisper P(St-BA-MAA)@disperse dye microspheres with different diameters ranging from 180 nm to 350 nm could be prepared by adjusting the concentrations of disperse dye and P(St-BA-MAA) seed microspheres and the preparation temperature. The P(St-BA-MAA)@disperse dye photonic crystals with FCC structure are regular and orderly, showing a bright and iridescent structural colors. Black disperse dye in composite microspheres plays a role in the absorption of stray light, and the structural color effect of P(St-BA-MAA)@disperse dye photonic crystals is better than pure P(St-BA-MAA) photonic crystals on white substrates. It is concluded that this research will offer theoretical basis and practical guidance for the fabrication of photonic crystals with brilliant structural colors on white substrates.

The polyurethane/polyacrylate soap-free emulsion formation: effects of hydrophilic polyurethane

The vinyl group terminated water-borne polyurethanes (WPU) with different DMPA content were prepared. Subsequently the core-shell polyurethane/polyacrylate (PUA) composite emulsions were synthesized by soap-free emulsion copolymerization. The WPU as sole surfactant was used in copolymerization, and the lowest surface tension could be achieved to 38.8 mN m−1. Furthermore, the final conversion of acrylic monomer was reached to 98% in the case of WPU reactive seed. The FTIR-ATR indirectly confirmed the core-shell structure of PUA, simultaneously combined with DSC results found that the compatibility of WPU and PA was enhanced by growing grafting efficiency. The TEM results further indicated that the amount of DMPA in WPU had a great significant role in polymerization and final morphology structure. The PUA composite particles changed from scattered structure, core-shell structure to multi-core structure with increasing DMPA content. Correspondingly, the reinforcing and toughening effects were also found in PUA films with the increase content of DMPA by tensile testing.

One-pot synthesis of mushroom-shaped polymeric Janus particles by soap-free emulsion copolymerization

The synthesis of Janus particles has been thriving in recent years, especially effective preparation strategies and amazing properties are the key focus of current academic and practical perspectives. In this work, the mushroom-shaped polymeric Janus particles (MsPJPs) with controllable morphologies and emulsifiabilities were first prepared by facile one-pot soap-free emulsion copolymerization (SfEP) based on swelling process and regulating ratio of common hydrophilic/hydrophobic monomers. Meanwhile, the nano-Ag particles were loaded onto MsPJPs with regioselectivity, which create new opportunities in a wide variety of applications, such as antibacterial medicine and medical instruments, functional coating, and catalytic materials.

A series of nanoparticles with phase-separated structures by 1,1-diphenylethene controlled one-step soap-free emulsion copolymerization and their application in drug release

A facile one-step approach to synthesize various phase-separated porous, raspberry-like, flower-like, core–shell and anomalous nanoparticles and nanocapsules via 1,1-diphenylethene (DPE) controlled soap-free emulsion copolymerization of styrene (S) with glycidyl methacrylate (GMA), or acrylic acid (AA) is reported. By regulating the mass ratio of S/GMA, transparent polymer solution, porous and anomalous P(S-GMA) particles could be produced. The P(S-GMA) particles turn from flower-like to raspberry-like and then to anomalous structures with smooth surface as the increase of divinylbenzene (DVB) crosslinker. Transparent polymer solution, nanocapsules and core–shell P(S-AA) particles could be obtained by altering the mole ratio of S/AA; anomalous and raspberry-like P(S-AA) particles are produced by adding DVB. The unpolymerized S resulted from the low monomer conversion in the presence of DPE aggregates to form nano-sized droplets, and migrates towards the external surfaces of the GMA-enriched P(S-GMA) particles and the internal bulk of the AA-enriched P(S-AA) particles. The nano-sized droplets function as in situ porogen, porous P(S-GMA) particles and P(S-AA) nanocapsules are produced when the porogen is removed. This novel, facile, one-step method with excellent controllability and reproducibility will inspire new strategies for creating hierarchical phase-separated polymeric particles with various structures by simply altering the species and ratio of comonomers. The drug loading and release experiments on the porous particles and nanocapsules demonstrate that the release of doxorubicin hydrochloride is very slow in weakly basic environment and quick in weakly acidic environment, which enables the porous particles and nanocapsules with promising potential in drug delivery applications.

Electrophoretic non-ionic nano-spheres (latexes) for structural coloring

Electrophoretic deposition (EPD) is one of the most important coating methods. This method has various advantages, such as being able to make a coating as a uniform film, even on a complex surface. Recently, we found that non-ionic poly(ester-sulfone) materials show anode selective electrophoretic behavior. In this paper, we performed electrophoresis of non-ionic nano particles (diameter: ca. 300 nm), prepared via soap-free emulsion copolymerization of vinyl monomers containing a sulfide linkage with styrene and subsequent oxidation to a sulfonyl group. After EPD, a structural color was observed, indicating that the monodisperse spheres had attached to the surface and exhibited specific light diffraction, in which the wavenumber is dependent on the incident angle.

Synthesis and Characterization of Poly (Methyl Methacrylate)/Polyethylenimine Grafting Core-Shell Nanoparticles for CO<sub>2</sub> Adsorption Using Soap-Free Emulsion Copolymerization

Unlike previous emulsion polymerization, we used grafting reactions in soap-free emulsion systems. In this study, we synthesized grafted PMMA/PEI core-shell nanoparticles by varying the MMA/PEI content and molecular weight of PEI (Mn = 600, 8000, and 10,000). The size and morphology of the core-shell nanoparticles were characterized by a particle size analyzer and scanning electron microscopy. The nanoparticles were 178 - 408 nm in diameter and swelled in water or methanol by 30 - 75 nm. The size of the nanoparticles increased with MMA contents, whereas the size distribution progressively became homogeneous with increasing molecular weight of PEI. Lastly, we measured CO2 adsorption capacity of the grafted PMMA/PEI core-shell nanoparticles, and we found the capacity to be limited at a level of 0.69 mg, which occurred for nanoparticles prepared from emulsions at a pH value of 11.

Monodispersepoly[BMA-co-(COPS-I)] Particles by Soap-Free Emulsion Copolymerization and Its Optical Properties as Photonic Crystals.

In order to study the surfactant-free emulsion copolymerization of benzyl methacrylate (BMA) with sodium 1-allyloxy-2-hydroxypropane sulfonate (COPS-I) and the resulting optical properties, a series of experiments was carried out at various reaction conditions such as the changes of BMA concentration, COPS-I concentration, BMA concentration under a fixed COPS-I amount, initiator and divinyl benzene (DVB) concentration. All the latices showed highly monodispersed spherical particles in the size range of 144~435 nm and the respective shiny structural colors from their colloidal photonic crystals. It is found that the changes in such polymerization factors greatly affect the number of particles and particle diameter, polymerization rate, molecular weight, zeta-potential, and refractive indices. The increase of number of particles led to the increased rate of polymerization and zeta-potential of the latices, on the other hand, to the decreased molecular weight. Refractive indices and the reflectivity increased with COPS-I concentration, on the other hand, and decreased with DVB concentration. Especially, refractive indices of the resulting poly[BMA-co-(COPS-I)] colloidal photonic crystals showed much higher values of 1.65~2.21 than that of polystyrene, due to the formation of core-shell shaped morphology. Monodisperse and high refractive index of poly[BMA-co-(COPS-I)] particles prepared in this work could be used for the study in photonic crystals and electrophoretic display.

Relationship between surface potential and particle size in soap-free emulsion copolymerization of styrene and methyl methacrylate using a water- or oil-soluble initiator

The soap-free emulsion copolymerization of styrene and methyl methacrylate (MMA) monomers using a water- or oil-soluble initiator was carried out at a constant monomer concentration to synthesize polymeric particles. The relationship between particle size and surface potential was investigated by changing the mixing ratio of MMA to styrene during the copolymerization. Both the particle sizes and zeta potentials were nearly constant when using water-soluble initiator, V-50, because the decomposition of the functional groups of the water-soluble initiator had a large influence on the surface potential. On the other hand, on increasing the molar fraction of MMA monomers, the surface potential of the particles formed during the copolymerization with an oil-soluble initiator, 2,2′-azobis(2-methylpropionitrile), decreased and the particle size increased due to coagulation between particles. This occurred because the surface potential is controlled by the presence of phenyl rings in the styrene monomer. We concluded that both particle size and surface potential can be controlled by adjusting the monomer mixture ratio in the soap-free emulsion copolymerization using an oil-soluble initiator.

Oxygen and carbon dioxide dual gas-responsive and switchable microgels prepared from emulsion copolymerization of fluoro- and amino-containing monomers.

We report herein the design and preparation of microgels that are responsive to both O2 and CO2 gases. The microgels were synthesized through soap-free emulsion copolymerization of O2-responsive monomer 2,3,4,5,6-pentafluorostyrene (FS) and CO2-responsive monomer 2-(diethylamino)ethyl methacrylate (DEA) with N,N'-methylenebis(acrylamide) (BisAM) as the cross-linker. The P(DEA-co-FS) microgels dispersed in aqueous solution could undergo volume phase transitions triggered by O2 and/or CO2 aeration. The particles were very responsive to CO2, while their responsivity to O2 was moderate. Microgels having different levels of the responsivity could be designed and prepared by varying the FS content in the copolymer. The phase transitions were also highly reversible, and the initial states of microgels could be easily recovered by "washing off" the trigger gases with N2. Multicycle O2, CO2, and N2 aerations were applied, and no loss in the dual gas responsivity and switchability was observed.

Preparation of poly(BMA-co-MMA) particles by soap-free emulsion polymerization and its optical properties as photonic crystals.

Narrowly dispersed poly(BMA-co-MMA) and PBMA latices with particle diameters ranging within 216-435 nm were synthesized successfully by surfactant-free emulsion polymerization with KPS and AIBA. The average particle diameter and particle size distribution, average molecular weight and its distribution, glass transition temperature, reflectance spectra in visible wavelength, and refractive indices for the respective poly(BMA-co-MMA) latices and their photonic crystals were systematically investigated in terms of BMA/MMA ratio, BMA content, polymerization temperature, and DVB effect. The rate of polymerization increased with increasing MMA concentration in BMA/MMA ratio. The particle diameter increased with BMA concentration in BMA/MMA ratio. The molecular weight increased with BMA concentration in BMA/MMA ratio and monomer concentration. The drying of the latices offered self-assembled shiny colloidal crystal films showing the characteristic structural colors in visible wavelength. All the poly(BMA-co-MMA) latices prepared in the study were fallen within the range of photonic grade microspheres. The reflectance measurement on the colloidal photonic crystals having different particle diameters clearly exhibited narrow stopbands. The reflection maxima (λ(max)) measured in this study were well close to the λ(max) calculated, derived from the Bragg's equation. The refractive indices of poly(BMA-co-MMA) photonic crystals were found to be almost same as the theoretical values and increased proportionally from 1.50 to 1.57 with BMA content in BMA/MMA ratios. It was, thus, found that the optical reflectance properties of the poly(BMA-co-MMA) colloidal photonic crystals can be controlled easily by adjusting the reaction conditions and BMA/MMA ratio in soap-free emulsion copolymerization of BMA and MMA.

The synthesis of core-shell monodisperse P(St-MAA) microspheres and fabrication of photonic crystals Structure with Tunable Colors on polyester fabrics

The core-shell monodisperse P(St-MAA) microspheres with different diameters ranging from 200 nm to 400 nm were prepared by soap-free emulsion copolymerization, in which styrene (St) and methacrylic acid (MAA) were polymerizable monomers, and ammonium persulfate (APS) acted as initiator. The diameters and monodispersity of P(St-MAA) microspheres could be controlled by adjusting the concentrations of styrene, methacrylic acid and ammonium persulfate. The core-shell structure and chemical component distribution of the P(St-MAA) microspheres were confirmed by TEM and XPS. The photonic crystals on polyester fabrics with three-dimensionally ordered arrangement were fabricated by self-assembly of gravitational sedimentation with P(St-MAA) microspheres and exhibited brilliant structural colors without any chemical dyes and pigments. SEM, TEM and crystallographic analysis were applied to confirm a face centered cubic (fcc) structure of the photonic crystals on polyester fabrics. The versatile structural colors of the photonic crystals were dependent on the photonic band-gap which could be regulated by the spherical size of P(St-MAA) microspheres and viewing angles. This technology may provide a new strategy to color the fabrics and reduce the pollution in the current textile industry.

A novel approach to prepare core/shell polymer latex particles with high sulphonate contents

Crosslinked x-P(St-MAA) seed latex was first prepared via soap-free emulsion copolymerization of styrene (St) and methyl methacrylic acid (MAA) with divinyl benzene as crosslinker and ammonium persulfate as initiator, and x-P(St-MAA)/x-P(St-NaSS) core/shell latex particles were then synthesized through a novel seeded emulsion copolymerization of St and sodium styrene sulphonate (NaSS) in the presence of water-soluble crosslinker N,N′-methylene bisacrylamide (BAA) using oil-soluble 2,2-azobis isobutyronitrile as initiator. TEM observation indicated that narrow dispersed core/shell latex particles were obtained, and element analysis showed that NaSS unit content in the whole particle and in the shell reached 22.8 wt% and 51.2 wt%, respectively.

Polymer photonic crystal band-gap modulation using PbS quantum dots

This study aims to present the manufacture of polymer photonic crystals (PCs) and the study of the influence of PbS quantum dots on their optical properties. Monodisperse latexes resulting from the polymerization of styrene and acrylic acid were obtained by a soap-free emulsion copolymerization process and their optical response was modified using PbS high refractive index nanoparticles. A stop-band modulation was achieved by controlling the nanoparticles concentration that resulted in the altering of the self-assembly process. Thus, at low PbS concentrations, a blue-shift of the band-gap was registered, whereas at high concentrations, a red-shift was measured. The hybrid materials were investigated by DLS, SEM, HRTEM, UV-VIS and XRD analyses.

Preparation and Water/Oil Repellency Properties of Waterborne Cationic Perfluorinated Polyacrylate

A series of waterborne cationic perfluorinated polyacrylate (WCFPA) were prepared by the reaction of styrene (St), methacrylatoethyl trimethyl ammonium chloride (DMC), butyl acrylate (BA), octadecyl acrylate (ODA) and 2-(perfluorooctyl)ethyl acrylate (FEA) by soap-free emulsion copolymerization and then the films of the WCFPA were prepared. Their structure and water/oil repellency properties, such as surface property, water and chemical resistance of their membrane were characterized by fourier transform infared spectrometer (FT-IR), interfacial tension instrument (IT), contact angle (CA) and spot test. The results reveal that WCFPA was endowed with low surface energy of its film. It was also found that the fluorinated polyacrylate had outstanding water and chemical resistance. Increasing the FEA amount in the emulsion was as sociated with larger contact angle and better water and oil repellency.

The influence of Ni nanoparticles and Ni (II) on the growth of Ag dendrites immobilized on the chelating copolymer membrane

Preparation of Ag dendrites on the surface of chelating copolymer membranes (PBAGI), which was synthesized by using the soap-free emulsion copolymerization of n-butylacrylate (BA) and acrylonitrile (AN), as well as 2-methacrylic acid 3-(bis-carboxymethylamino)-2-hydroxy-propyl ester (GMA-IDA) that was used as a chelating group, is presented in this study. The characteristics of polymer membranes were investigated by Fourier transform infrared (FTIR) spectroscopy and elementary analysis (EA). The weight fraction of GMA-IDA in the polymer was 4.2wt% as revealed by elemental analysis. The chelating group, –N(CH2COO−Na+)2 on the polymer was used to coordinate different amounts of Ni(II), controlled by different chelating times and subsequently reduced to Ni nanoparticles, as templates for growing Ag nanocrystals from 1.67wt% AgNO3 aqueous solution with 55.7 ppm poly(vinyl pyrrolidone) (PVP) added. In addition, the effect of Ni2+ concentration on the growth of the Ag dendrites was studied. Crystallinity and morphology of Ag dendrites were examined with X-ray diffraction (XRD) and scanning electronic microscopy (SEM), respectively. Amount of Ag dendrites increased with the increasing of Ni nanoparticles on the PBAGI membrane or the dose of Ni2+ present in the aqueous solution. Notable, under higher amount of Ni nanoparticles (over 200mmol Ni2+/g PBAGI membrane), Ag dendrites could be successful grown on the membrane. However, higher dose of Ni2+ (over 41.3ppm) might inhibit the growth of Ag dendrites.

Synthesis, characterization, and temperature-dependent colloidal stability of poly(N-isopropylacrylamide)-grafted polystyrene/poly(styrene-co-4-vinylbenzyl N, N-diethyldithiocarbamate) hairy particles

Poly(N-isopropylacrylamide)-grafted polystyrene/ poly(styrene-co-4-vinylbenzyl N, N-diethyldithiocarbamate) (PNIPAM-grafted PS/P(St-co-VBDC)) hairy particles were synthesized by photo-polymerizing N-isopropylacrylamide monomer in the presence of PS/P(St-co-VBDC) core par- ticles. Here, the VBDC unit, which was incorporated into the surface of core particles by seeded soap-free emulsion copolymerization, acted as a photo-iniferter. By varying the polymerization conditions, a series of hairy particles having different grafting heights and grafting densities was success- fullyobtained.Thehairyparticlesexhibitedwell-definedcore/ shell morphology. PS/P(St-co-VBDC) formed the core which was surrounded by PNIPAM shell. The determination of critical coagulation concentration (CCC) indicated that the hairy particles were stabilized via both electrostatic and steric mechanisms (i.e., electrosteric mechanism) at a temperature lower than LCST of PNIPAM. However, these particles gave muchlowerCCCs whenheatedtothe temperature higherthan LCST, exhibiting temperature-dependent colloidal stability.

Nonspherical dented poly(methyl methacrylate)/poly(styrene-co-divinylbenzene) particles formed in seeded soap-free emulsion copolymerization

In this study, nonspherical poly(methyl methacrylate)/poly(styrene-co-divinylbenzene) [PMMA/P(St-co-DVB)] particles having multiple dents on the surface were prepared by seeded soap-free emulsion copolymerization of St and DVB (used as a crosslinker) on spherical linear PMMA seed particles. The effect of various polymerization parameters on particle morphology, as well as polymerization kinetics and morphological evolution, were investigated in detail. It was found that, to prepare this kind of nonspherical particles, it was necessary to conduct the polymerization at a relatively low temperature, using batch monomer addition mode and PMMA seed of relatively high molecular weight. The formation of the nonspherical particles was attributed to the phase separation between the second-stage monomers and the crosslinked P(St-co-DVB) network being formed during polymerization.

Poly(styrene-acrylamide-acrylic acid) copolymer fluorescent microspheres with improved hydrophilicity: preparation and influence on protein immobilization

Poly(styrene-acrylamide-acrylic acid) copolymer fluorescent microspheres (PSAAFMs) with improved surface hydrophilicity were synthesized through an improved soap-free emulsion copolymerization method, in which the proportion of acrylamide on the surface of the microspheres was increased. Azidocarbonyl groups, which can be rapidly coupled with proteins under mild conditions, were introduced onto the PSAAFMs using an azido reaction. The PSAAFMs were characterized using a fluorescence microscope, an ultraviolet/visible spectrometer, a Fourier transforms infrared spectrometer, a transmission electron microscope (TEM), a size analyzer, and a fluorescence spectrophotometer. Furthermore, covalent linking through the azidocarbonyl groups and physical nonspecific attachments of bovine serum albumin (BSA), trypsin, and human chorionic gonadotropin (HCG) onto the surface of the microspheres were also determined to evaluate the influence of improved surface hydrophilicity on nonspecific protein adsorption. Results from the TEM and size analyzer showed that the PSAAFMs maintained spherical shapes with an average diameter of 2.5 ± 0.22 µm. Fluorescence measurement indicated that the maximum emission wavelength underwent a slight blue shift from 514 to 512 nm. Environmental factors, such as pH value, imposed certain effects on fluorescence intensities. The linear relationship between fluorescence intensity and microspheres' concentration, which ranged from 1 × 10−3 to 10 × 10−3 g L−1, suggest their quantitative application. The significant decrease in the physical nonspecific adsorption of BSA, trypsin, and HCG in comparison with the microspheres without improved hydrophilicity suggest the increased amount of acrylamide on the surface of the microspheres. The protein covalent immobilization experiments revealed significant increases in BSA and HCG immobilization in comparison with the nonspecific physical attachment. The combination of high hydrophilicity and electrostatic repulsion could severely inhibit nonspecific protein attachment onto the surface of the microspheres.

Preparation and Charcterisation of PSt/GMA/DVB Microspheres by Soap-Free Emulsion Polymerization

PSt/GMA/DVB microspheres were prepared by soap-free emulsion co-polymerization of St, GMA and DVB monomers. The fractional conversion of polymerizations was characterized by gravimetric methods. All the fractional conversions of polymerization exceeded 90 percentages. The amounts of epoxy groups on the microspheres were measured by hydrochloric acid- acetone method. The results showed that the added time of GMA monomers had little influence on the amounts of epoxy groups in the microspheres; however, with the increasing of GMA monomers, the epoxy groups increased; with the increasing of DVB monomers, the epoxy groups drastically decreased.

High Solids Content, Soap‐Free, Film‐Forming Latexes Stabilized by Laponite Clay Platelets

High solids content film-forming poly[styrene-co-(n-butyl acrylate)] [poly(Sty-co-BuA)] latexes armored with Laponite clay platelets have been synthesized by soap-free emulsion copolymerization of styrene and n-butyl acrylate. The polymerizations were performed in batch in the presence of Laponite and a methyl ether acrylate-terminated poly(ethylene glycol) macromonomer in order to promote polymer/clay association. The overall polymerization kinetics showed a pronounced effect of clay on nucleation and stabilization of the latex particles. Cryo-transmission electron microscopy observation confirmed the armored morphology and indicated that the majority of Laponite platelets were located at the particle surface. The resulting nanostructured films displayed enhanced mechanical properties.