Hollow Latex Particles Research Articles

Enhancing formation and retention of hollow structural integrity through intermediate and outermost layer design in seeded emulsion polymerization of hollow latex particles

AbstractThe synthesis of hollow latex particles through seeded emulsion polymerization involves a series of intricate steps, including the formation of distinct polymer layers with specific properties. Despite extensive research, preserving the desired hollow structure remains challenging due to the unclear role of the encapsulating polymer layers. This study systematically adjusts the glass transition temperature (Tg) of the intermediate layer by varying the butyl acrylate (BA) ratio in the monomer feed mixture. By controlling the reaction temperature during alkali swelling, we explore the critical influence of Tg on hollow latex particle formation from carboxylated core latex particles. To ensure long‐term hollow structure retention after drying, a rigid outer layer is polymerized onto the intermediate layer. Surprisingly, higher divinylbenzene (DVB) mass ratios (5.0 and 10.0 wt%) do not result in a highly crosslinked hollow shell due to DVB self‐nucleation. This paper emphasizes the importance of precise design parameters for both intermediate and outermost layers in achieving and maintaining hollow latex particle structures. Understanding each layer's role and optimizing their compositions contribute to advancing hollow latex particle synthesis through seeded emulsion polymerization.

Review on Synthesis of Colloidal Hollow Particles and Their Applications

Hollow latex (HL) particles of polymers or hybrid polymer/inorganic materials have advantages in efficient encapsulation of active ingredients, ability to improve opacity or hiding power, and low density. Due to the flexible design for achieving the desired functionality, polymeric HL particles serve as stimuli-responsive capsules for drug delivery and cosmetics, white pigment for coatings, as well as nanoreactors for the confined reactions. Among numerous studies on the synthesis of HL particles for specific applications, this review article summarizes the recent works on the HL particles prepared from both synthetic and natural polymers. The template-based methods using sacrificial hard or soft template, self-templating, and nonsacrificial techniques are described. Various factors affecting morphologies and properties of HL particles are discussed in detail. Their applications in coatings, cosmetics, biomedicines, electronics, and others are also presented.

One-pot synthesis of non-spherical hollow latex polymeric particles via seeded emulsion polymerization

Non-spherical (ns) hollow latex (HL) particle with a void on one side of a polymer particle surrounded by a double-layered shell was fabricated via the one-pot seeded emulsion polymerization (SEP). Start from the ns seed formed by swelling styrene (St) or methyl methacrylate (MMA) mixed with azobisisobutyronitrile into a crosslinked spherical poly(styrene/divinyl benzene/acrylic acid) P(St/DVB/AA) particle and then polymerized. The ns seed particle having two lobes of crosslinked P(St/DVB/AA) and polystyrene (PS) protrusion obtained was then swelled with MMA/DVB/AA monomers (MMA:DVB = 1:2). After polymerization, the obtained ns HL particle with a single void on the PS side was generated without the seed removal. The key success factors are the locus of polymerization at the seed surface and the fast/efficient phase separation between PS seed and shell polymers. The double-layered shell composing of PS inner shell and P(DVB/MMA/AA) outer shell prevented the collapse of hollow structure. The ns HL particles (0.79 μm in diameter and 1.04 μm in over length) as a white pigment in the coating had a hiding power better than ns solid particles (ASTM D2803-96a, 2003).

Fabrication of amino-containing hollow polymer latex and its composite with inorganic nanoparticles

Using N,N′-dimethylaminoethyl methacrylate (DMAEMA) as functional co-monomer and styrene (St) as main monomer, the amino-containing hollow latexes were fabricated via one-step emulsion copolymerization and following stepwise acid-alkali post-treatment. Influences of DMAEMA content and post-treatment condition on the morphology and volume expansion of the P(St-co-DMAEMA) latex particles were investigated based on the TEM characterization, and the hollow-forming mechanism was proposed. Results showed that the introduction of 2-butonane promoted the mobility of the polymer chains and the hollow structure generated under moderate post-treatment conditions. Many factors should be balanced to obtain fine hollow particles, an appropriate content of DMAEMA was 15 mol% to all the monomers, and the optimized post-treatment conditions were at 70 °C for 1 h both for acid treatment (initial pH 4.0) and for alkali treatment (initial pH 9.0). Under the optimized conditions, the mean diameter and volume expansion of the resulted hollow particles were 264 nm and 934%, respectively. Finally, the hollow P(St-co-DMAEMA)/laponite composite latex particles were fabricated simply by electrostatic adsorption process, and the resulted composite hollow particles loaded 4.1 wt% of laponite platelets and showed better thermal stability. This simple and facile method can be applied to fabricate the functional hollow latex particles with amino groups including polymeric and polymeric-inorganic composite materials.

Hollow core-shell particles via NR latex seeded emulsion polymerization

Abstract Natural rubber (NR)-based hollow latex (HL) particles have been prepared by seeded emulsion polymerization of methyl methacrylate/divinyl benzene/acrylic acid (MMA/DVB/AA) monomers on NR seed. By using tert-butyl hydroperoxide/tetraethylene pentamine (t-BuHP/TEPA) as a redox initiator, the locus of polymerization was localized at the surface of the NR particle. After swelling with monomers, DVB in NR particle gradually moved outward to compensate the co-polymerization. Phase separation between the NR seed and the polymeric shell occurred and a void was subsequently formed at a MMA/DVB molar ratio of 2.7/1. The void cavity was enlarged when the monomer to seed (M/S) weight ratio was increased to 4/1. Without the necessity of any residual core removal, polydisperse NR-based hollow nanocomposites (298 ± 58 nm) possessing NR-P(MMA/DVB/AA) double-layered shell and a single void (155 ± 37 nm) were obtained. SEM images revealed an increase in surface roughness of the HL particle with increasing M/S weight ratios. The large specific surface area of these NR-based hollow nanocomposites (114.6 m2/g) with a 3.5 nm pore diameter indicates that the polymeric shell is mesoporous. The presence of carboxyl groups, as indicated by negative zeta potentials, can further facilitate surface functionalization. The large void cavity of these NR-based HL particles makes them particularly suited as delivery vehicle systems.

Self film‐forming and opaque hollow latexes fabricated via seeded emulsion polymerization followed by alkali post‐treatment

ABSTRACTIn order to obtain novel hollow latexes with both opaque and self film‐forming properties, the four‐layer core/shell latex particles—sequentially consisting of a high carboxyl‐containing soft core, a transition layer, a rigid supporting layer, and an outermost film‐forming layer—are first designed and prepared by emulsion polymerization, and then treated with alkali to fabricate self film‐forming hollow latexes. On the basis of the previous research on the three‐layer core/shell latex, influences of the composition and thickness of the film‐forming layer on the properties and morphologies of the four‐layer core/shell and the final hollow latexes are investigated. Results show that under optimized conditions with butyl acrylate/styrene (BA/St) mass ratio of 2/1, divinyl benzene (DVB) content of 1 wt %, and core/film‐forming layer mass ratio of 1/6 in the film‐forming layer preparation, the final hollow latex particles exhibit best morphology considering both light scattering efficiency and film‐forming capability at room temperature. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015, 132, 42541.

Effect of the intermediate layer–core ratio on the morphology and opacity ability of hollow latex particles

ABSTRACTIn this study, well‐monodispersed hollow latex particles were synthesized through semicontinuous seed emulsion polymerization, and the effect of the hollow latex particles' intermediate layer–core ratios on their morphology and opacity ability were studied. The results show that when the intermediate layer–core ratios increased from 6 to 10, the swelling degree of the hollow latex particles decreased, and the intensity gradually increased, but the opacity ability increased first and then decreased. When the intermediate layer–core ratio was 8, the opacity ability of the hollow latex particles was the best. When the intermediate layer–core ratios were 6 and 7, the surface of the hollow latex particles was rough, and they showed a great swelling degree, big cavity, and thin shell, and few of latex particles collapsed or ruptured. When the intermediate layer–core ratios were 9 and 10, the hollow latex particles had a smooth surface, thick shell, and small swelling degree and cavity, and roughly, there was no collapse or rupture of the hollow latex particles. When the intermediate layer–core ratio was 8, the swelling degree of the hollow latex particles was moderate. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015, 132, 42268.

One-pot synthesis of organic-inorganic hybrid hollow latex particles via Pickering and seeded emulsion polymerizations

Hybrid hollow latex (HL) particles possessing poly(styrene-co-acrylic acid) (P(St/AA)) as the inner shell, poly(divinyl benzene) (PDVB) as the outer shell, and silica nanoparticles (SiNPs) as the stabilizer were conveniently prepared via the combined Pickering and seeded emulsion polymerizations. P(St/AA) particles (435 nm) were used as seeds, DVB as a swollen and crosslink monomer, 2,2′-azobis(2-methylpropionamidine) dihydrochloride as initiator, and SiNPs as Pickering stabilizer. Without core removal, solvent evaporation, and surface modification steps, the spherical, monodisperse, and non-collapsed HL-SiNPs particles (722 nm) with double shell polymer layer and a large void cavity (400 nm) were obtained. The presence of large cavity and double shell may enable these hybrid HL-SiNPs particles to be used as lightweight filler and/or white pigment in coatings.

Optical properties of hollow latex particles as white pigment in paint film

Hollow latex (HL) particles consisting of poly(methyl methacrylate-co-divinyl benzene-co-acrylic acid) were synthesized and used as an alternative white pigment in paint film. The opacity of the coating film prepared from a mixture of HL or solid particles, poly(styrene-co-acrylic acid) and poly(styrene-co-methyl methacrylate-co-acrylic acid), was determined using the reflectometric method, which measures the hiding power of coatings. The film containing HL particles, allowing multiple light scattering, showed better hiding efficiency compared to coatings containing solid particles. The opacity of HL containing coating film linearly increased with the content of HL particles. For the adsorption of formaldehyde, the HL particles were further functionalized with amine containing compounds, i.e., chitosan and polyethyleneimine (PEI). HL–chitosan particles were well dispersed in coating film in contrast to the HL–PEI particles that were present as aggregates. Therefore, HL–chitosan particles with highest coating opacity at 15 wt.% have the potential for utilization as an opacifying agent or white pigment for special indoor coating applications.

A facile fabrication of amphiphilic Janus and hollow latex particles by controlling multistage emulsion polymerization

In this paper, we found that morphology controllable compound latex particles could be prepared by controlling the multistage emulsion polymerization. Influences of the content of methacrylic acid (MAA) on preparing the hydrophilic cores and the particles were investigated with the observation of dynamic light scattering (DLS) and transmission electron microscope (TEM) results. The acorn-like latex particles were synthesized by partially encapsulated with hydrophobic polystyrene (PSt)-layer. With adding moderate polarity polymethylmethacrylate (PMMA) interlayer, the hydrophilic cores could be fully encapsulated by the hydrophobic PSt-layer, and the core–shell structure formed. After alkali treatment, the acorn-like and core–shell latex particles evolved into amphiphilic Janus and hollow latex particles, respectively. The morphology of latex particles was investigated by TEM, and the forming mechanism of amphiphilic Janus and hollow latex particles was proposed.

Effect of the shell crosslinking level and Core/Shell ratio on the morphology of latex particles in the preparation of hollow latexes

Three-layer core/shell latex particles with various shell crosslinking level and shell thickness were prepared by multistep emulsion polymerization, and the hollow latex particles with different morphologies were then obtained after alkali post-treatment. Influences of divinyl benzene (DVB) content and the core/shell mass ratio on emulsion polymerization and particle morphology were investigated. Results showed that with the increase of DVB content, the percentage of total amount of -COOH on the particle surface and free in aqueous phase (PSF a) decreased, and the morphology of the post-treated particles underwent evolution from cracked, intact hollow to deficient swelling structure. Decreasing the core/shell mass ratio could not only make more carboxyl groups encapsulated by the shell, but also increase the shell resistance to the swelling of the core. The uniform hollow latex particles with intact morphology were obtained when the DVB content was 3.54 wt% and the core/shell mass ratio was 1/6.

Effect of monomer feeding mode on the preparation of hollow latexes with high MAA content in the core latex preparation

In order to prepare hollow latex particles with optimum morphology based on osmotic swelling principle, three- layer core/shell latex particles with 40 wt% MAA in the core were first prepared via multistep seeded emulsion copolymerization, in which monomers were added by a semi-continuous process with monomer addition under two different forms: pure monomers' mixture (monomer addition), and pre-emulsified monomers (pre-emulsion addition). Then, the hollow latex particles with different morphologies were obtained after alkali post-treatment. Influences of the monomer feeding mode on the emulsion polymerization and the particle morphology were investigated. Results showed that the pre- emulsion addition could significantly improve the polymerization stability in each step, and greatly enhance the uniformity of shell encapsulation. The sizes of the core and core/shell latex particles obtained by the pre-emulsion addition were smaller and more uniform than those synthesized by the monomer addition, and the hollow latex particles with intact morphology were generated by alkali post-treating of the core/shell latexes prepared from the pre-emulsion addition. As the core size increased, the morphology of the post-treated particles underwent evolution from hollow to collapse. Moreover, the mechanism of the particle morphological evolution was proposed.

Synthesis and characteristics of poly(methacrylic acid-co -N -isopropylacrylamide) thermosensitive composite hollow latex particles and their application as drug carriers

In this work, the poly(methacrylic acid-co-N-isopropylacrylamide) thermosensitive composite hollow latex particles was synthesized by a three-step reaction. The first step was to synthesize the poly(methyl methacrylate-co-methacrylic acid) (poly(MMA-MAA)) copolymer latex particles by the method of soapless emulsion polymerization. The second step was to polymerize methacrylic acid (MAA), N-isopropylacrylamide (NIPAAm), and N,N′-methylenebisacrylamide in the presence of poly(MMA-MAA) latex particles to form the linear poly(methyl methacrylate-co-methacrylic acid)/crosslinking poly(methacrylic acid-co-N-isopropylacrylamide) (poly(MMA-MAA)/poly(MAA-NIPAAm)) core–shell latex particles. In the third step, the core–shell latex particles were heated in the presence of ammonia solution to form the crosslinking poly(MAA-NIPAAm) thermosensitive hollow latex particles. The morphologies of poly(MMA-MAA)/poly(MAA-NIPAAm) core–shell latex particles and poly(MAA-NIPAAm) hollow latex particles were observed. The influences of crosslinking agent and shell composition on the lower critical solution temperature of poly(MMA-MAA)/poly(MAA-NIPAAm) core–shell latex particles and poly(MAA-NIPAAm) hollow latex particles were, respectively, studied. Besides, the poly(MAA-NIPAAm) thermosensitive hollow latex particles were used as carriers to load with the model drug, caffeine. The effect of various variables on the amount of caffeine loading and the efficiency of caffeine release was investigated. © 2013 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2013, 51, 5203–5214

Hollow latex particles functionalized with chitosan for the removal of formaldehyde from indoor air

Chitosan and polyethyleneimine (PEI) functionalized hollow latex (HL) particles were conveniently fabricated by coating poly(methyl methacrylate-co-divinyl benzene-co-acrylic acid) (P(MMA/DVB/AA)) HL particles with 5wt% chitosan or 14wt% PEI. The materials were used as formaldehyde adsorbent, where their adsorbent activity was examined by Fourier Transform Infrared (FTIR) spectroscopy. The nucleophilic addition of amines to carbonyls generated a carbinolamine intermediate with a characteristic band at 1020cm−1 and Schiff base product at 1650cm−1, whose intensity increased with prolonged formaldehyde exposure times. The major products observed in HL-chitosan were carbinolamine and Schiff base, whereas a small amount of Schiff base was obtained in HL-PEI particles, confirming a chemical bond formation without re-emission of formaldehyde. Compared to HL-PEI, HL-chitosan possesses higher formaldehyde adsorption efficiency. Besides providing opacity and whiteness, the multilayer HL-chitosan particles can effectively remove indoor air pollutants, i.e., formaldehyde gas, and, hence, would be useful in special coating applications.

Controlled release of Capreomycin sulfate from pHresponsive nanocapsules

Abstract The synthesis of polymeric nanocapsules loaded with the antituberculosis drug Capreomycin sulphate is presented in this work. The pHresponsive polymeric nanocapsules were successfully synthesized using the RAFT-based vesicle templating approach in the presence of Capreomycin sulphate. Anionic small polyelectrolytes comprising randomly distributed butyl acrylate and acrylic acid units were adsorbed on cationic vesicles of dimethyldioctadecyl ammonium bromide (DODAB). N,N-(dimethylamino)ethyl methacrylate (DMAEMA) and methyl methacrylate (MMA) or tertiary butyl methacrylate (tBMA) and MMA were used for the formation of the polymeric shells. Subsequently the tBMA was hydrolyzed to obtain negatively charged nanocapsules. The nanocapsule morphology for both approaches was characterized by DLS and TEM. The most stable hollow latex particles were obtained with the monomer composition of DMAEMA:MMA = 1:1. These nanocapsules were found to be colloidally stable and pH-responsive. The entrapment efficiency of drug determined by UV-Vis-spectroscopy was 70 %. The drug release rate from nanocapsules at pH 6.5 was found to be relatively fast (substantial release within one hour already), however we believe slower release can be achieved by using a thicker polymer shell.

Synthesis and characteristics of poly(N-isopropylacrylamide-co-methacrylic acid)/Fe3O4/poly(N-isopropylacrylamide-co-methacrylic acid) two-shell thermosensitive magnetic composite hollow latex particles

In this study, the poly(N-isopropylacrylamide-methylacrylate acid)/Fe3O4/poly(N-isopropylacrylamide-methylacrylate acid) (poly(NIPAAm-MAA)/Fe3O4/poly(NIPAAm-MAA)) two-shell magnetic composite hollow latex particles were synthesized by four steps. The poly(methyl methacrylate-co-methylacrylate acid) (poly(MMA-MAA)) copolymer latex particles were synthesized first. Then, the second step was to polymerize NIPAAm, MAA, and crosslinking agent in the presence of poly(MMA-MAA) latex particles to form the linear poly(MMA-MAA)/crosslinking poly(NIPAAm-MAA) core–shell latex particles. Then, the core–shell latex particles were heated in the presence of NH4OH to dissolve the linear poly(MMA-MAA) core to form the poly(NIPAAm-MAA) hollow latex particles. In the third step, the Fe3O4 nanoparticles were generated in the presence of poly(NIPAAm-MAA) hollow polymer latex particles and formed the poly(NIPAAm-MAA)/Fe3O4 magnetic composite hollow latex particles. The fourth step was to synthesize poly(NIPAAm-MAA) in the presence of poly(NIPAAm-MAA)/Fe3O4 latex particles to form the poly(NIPAAm-MAA)/Fe3O4/poly(NIPAAm-MAA) two-shell magnetic composite hollow latex particles. The effect of various variables such as reactant concentration, monomer ratio, and pH value on the morphology and volume-phase transition temperature of two-shell magnetic composite hollow latex particles was studied. Moreover, the latex particles were used as carriers to load with caffeine, and the caffeine-loading characteristics and caffeine release rate of latex particles were also studied. © 2013 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2013, 51, 2880–2891

Highly charged hollow latex particles prepared via seeded emulsion polymerization

The carboxylated hollow latex (HL) particles possessing high surface charge density were conveniently prepared by using poly(styrene-co-acrylic acid) (P(St/AA)) as seed particles and methyl methacrylate (MMA)/divinylbenzene (DVB)/AA as monomers. Without seed removal, the hollow structure was simply tuned by adjusting the monomer/seed ratio and the monomer content. The monodisperse, spherical, and non-collapsed HL particles with double shell having the void of 280nm were obtained from P(St/AA) seeds of 300nm. The conductimetric back titration, SEM, TEM, and dynamic light scattering measurement revealed that the surface charge density, surface roughness, and size of HL particles significantly increased when applying the stepwise charging monomers/initiator. The highly charged HL particles would be well dispersed in coating film providing good optical properties, for example, opacity and whiteness.

Synthesis and characteristics of poly(methyl methacrylate-methacrylic acid-3,3-(trimethoxysilyl) propyl methacrylate) hollow latex particles and their application to drug carriers

In this study, the hollow latex particle was synthesized by three processes. The first process was to synthesize the poly(methyl methacrylate-co-methacrylic acid) (poly(MMA-MAA)) copolymer latex particles by the method of soapless emulsion polymerization. Following the first process, the second process was to polymerize MMA, MAA, 3,3-(trimethoxysilyl) propyl methacrylate (MPS), and ethylene glycol dimethacrylate in the presence of poly(MMA-MAA) latex particles to form the linear poly(MMA-MAA)/crosslinking poly(MMA-MAA-MPS) core–shell latex particles. In the third process, the core–shell latex particles were heated in the presence of ammonia to form the poly(MMA-MAA-MPS) hollow latex particles. A sufficient heating time and high-heating temperature were necessary for the ammonia to dissolve the linear poly(MMA-MAA) core to form a perfect hollow structure. The crosslinking poly(MMA-MAA-MPS) shell was a barrier for the ammonia to diffuse into the latex particles so that the latex particle with the high-crosslinking shell showed an imperfect hollow structure. Besides, the hollow poly(MMA-MAA-MPS) latex particles reacted with ZnO nanoparticles, which were synthesized by a traditional sol-gel method, to form the polymer/inorganic poly(MMA-MAA-MPS)/ZnO composite hollow latex particles. With the increase of crosslinking degree would increase the amount of ZnO bonding. Moreover, the poly(MMA-MAA-MPS) hollow latex particles were used as carriers to load with the model drug, caffeine. The release of caffeine from poly(MMA-MAA-MPS) hollow latex particles was investigated.

Synthesis and characteristics of poly(N -isopropylacrylamide-co -methacrylic acid)/Fe3 O4 thermosensitive magnetic composite hollow latex particles

In this study, the poly(NIPAAm–MAA)/Fe3O4 hollow latex particles were synthesized by three steps. The first step was to synthesize the poly(methyl methacrylate-co-methylacrylate acid) (poly(MMA-MAA)) copolymer latex particles by the method of soapless emulsion polymerization. Following the first step, the second step was to polymerize N-isopropylacrylamide (NIPAAm), MAA, and crosslinking agent (N,N'-methylene-bisacrylamide (MBA)) in the presence of poly(MMA-MAA) latex particles to form the linear poly(MMA-MAA)/crosslinking poly (NIPAAm-MAA) core-shell latex particles. After the previous processes, the core-shell latex particles were heated in the presence of NH4OH to dissolve the linear poly(MMA-MAA) core in order to form the poly(NIPAAm-MAA) hollow latex particles. In the third step, Fe2+ and Fe3+ ions were introduced to bond with the COOH groups of MAA segments in the poly(NIPAAm-MAA) hollow polymer latex particles. Further by a reaction with NH4OH and then Fe3O4 nanoparticles were generated in situ and the poly(NIPAAm-MAA)/Fe3O4 magnetic composite hollow latex particles were formed. The concentrations of MAA, crosslinking agent (N,N'-methylene bisacrylamide), and Fe3O4 nanoparticles were important factors to influence the morphology of hollow latex particles and lower critical solution temperature of poly(NIPAAm–MAA)/Fe3O4 magnetic composite hollow latex particles. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012

Synthesis and characteristics of poly(methacrylic acid–co–N-isopropylacrylamide)/Nano ZnO thermosensitive composite hollow latex particles

In this work, the poly(methacrylic acid–co–N-isopropylacrylamide)/Nano ZnO thermosensitive composite hollow latex particles was synthesized by three processes. The first process was to synthesize the poly(methyl methacrylate-co- methacrylic acid) (poly(MMA–MAA)) copolymer latex particles by the method of soapless emulsion polymerization. The second process was to polymerize MAA, N-isopropylacrylamide (NIPAAm) and N,N′-Methylenebisacrylamide (MBA) in the presence of poly(MMA–MAA) latex particles to form the linear poly(MMA–MAA)/crosslinking poly(MAA-NIPAAm) core–shell latex particles, and then the core–shell latex particles were heated in the presence of ammonia solution to form the poly(MAA-NIPAAm) thermosensitive hollow latex particles. In the third process, the poly(MAA-NIPAAm) hollow latex particles reacted with ZnO nanoparticles to form the poly(MAA-NIPAAm)/ZnO thermosensitive composite hollow latex particles on which the ZnO nanoparticles were adsorbed. Besides, a novel process was used to synthesize the poly(MAA-NIPAAm)/ZnO composite latex particles in which the ZnO nanoparticles were encapsulated. The effects of various variables on the morphology of poly(MAA-NIPAAm)/ZnO composite hollow latex particle were studied.