The effect of acrylic acid amount on the colloidal properties of polystyrene latex

Poly(styrene-co-acrylic acid) (St/AA) latices were prepared by using a batch soap-free emulsion copolymerisation in non-buffered medium. Polymerisation kinetics, followed by gravimetric method, revealed that increasing AA comonomer concentration was directly proportional to the copolymerisation rate, while adding AA comonomer caused a strong decrease of particle size of final St/AA latex particle without affecting the size distribution. Transmission electron microscopy indicated that the particles were monodispersed and spherical in shape irrespective of AA amount used in the investigated range. The colloidal stability of the latices was increased upon increasing the AA concentration; owing to the electrosteric stabilisation originated from AA-rich layer on the particle surface. In addition, electrophoretic mobility of formed particles versus polymerisation conversion exhibited the constancy of the surface charge density during the polymerisation process and was inferred for discussion of the polymerisation mechanism of this system.     

Preparation of micron-size monodisperse polymer particles by dispersion copolymerization of styrene with poly(2-oxazoline) macromonomer

This article describes the preparation of micron-size monodisperse polymer particles by dispersion copolymerization of styrene with a poly(2-oxazoline) macromonomer in an aqueous ethanol solution. The macromonomer acted as a comonomer as well as a stabilizer. The diameter of the particles increased as the concentration of the macromonomer decreased. The higher the molecular weight of the macromonomer, the smaller the particle size. The copolymerization in the solvent containing higher water content gave smaller polymer particles. Under the condition giving the monodisperse particles, the particles volume increased linearly with the yield of the particles. From ESCA analysis of the particle surface, poly(2-oxazoline) chains were enriched on the surface. © 1993 John Wiley & Sons, Inc.     

Amphiphilic graft copolymers - preparation and interfacial properties

Amphiphilic graft copolymers containing poly(ethylene oxide) (PEO) grafts have been prepared by various methods, for example, by coupling of reactive hydrophobic backbone polymers with end-functionalised PEO, by macromonomer copolymerisation, and by anionic graft polymerisation of EO onto polymer backbones carrying functional groups as initiator precursors. The graft copolymers are amphiphilic and were shown to accumulate at surfaces and interfaces in solution and in the solid state. Amphiphilic starch derivatives were prepared by reaction of amylose and starch with aliphatic α-epoxides.     

Control of the PEO chain conformation on nanoparticles by adsorption of PEO-block-poly(L-lysine) copolymers and its significance on colloidal stability and protein repellency

The physical adsorption of PEO(n)-b-PLL(m) copolymers onto silica nanoparticles and the related properties of poly(ethylene oxide) (PEO)-coated particles were studied as a function of the block copolymer composition. Copolymers adopt an anchor-buoy conformation at the particle surface owing to a preferential affinity of poly(L-lysine) (PLL) blocks with the silica surface over PEO blocks when a large excess of copolymer is used. The interdistance between PEO chains at particle surface is highly dependent on the size of PLL segments; a dense brush of PEO is obtained for short PLL blocks (DP = 10), whereas PEO chains adopt a so-called interacting "mushroom" conformation for large PLL blocks (DP = 270). The size of the PEO blocks does not really influence the copolymer surface density, but it has a strong effect on the PEO layer thickness as expected. Salt and protein stability studies led to similar conclusions about the effectiveness of a PEO layer with a dense brush conformation to prevent colloidal aggregation and protein adsorption. Besides, a minimal PEO length is required to get full stabilization properties; as a matter of fact, both PEO(45)-b-PLL(10) and PEO(113)-b-PLL(10) give rise to a PEO brush conformation but only the latter copolymer efficiently stabilizes the particles in the presence of salt or proteins.     

Polystyrene‐graft‐poly(ethylene oxide) copolymers prepared by macromonomer technique in dispersion. I. Liquid chromatographic separation of product mixtures

Products of the radical dispersion copolymerization of methacryloyl‐terminated poly(ethylene oxide) (PEO) macromonomer and styrene were separated and characterized by size exclusion chromatography (SEC), full adsorption‐desorption (FAD)/SEC coupling and eluent gradient liquid adsorption chromatography (LAC). In dimethylformamide, which is a good solvent for PEO side chains but a poor solvent for polystyrene (PS), amphiphilic PS‐graft‐PEO copolymers formed aggregates, which were very stable at room temperature even upon substantial dilution. The aggregates disappeared at high temperature or in tetrahydrofuran (THF), which is a good solvent for both homopolymers and for PS‐graft‐PEO. FAD/SEC procedure allowed separation of homo‐PS from graft‐copolymer and determination of both its amount and molar mass. Effective molar mass of graft‐copolymer was estimated directly from the SEC calibration curve determined with PS standards. Presence of larger amount of the homo‐PS in the final graft‐copolymer products was also confirmed with LAC measurements. The results indicate that there are at least two or maybe three polymerization loci; namely the continuous phase, the particle surface layer and the particle core. The graft copolymers are produced mainly in the continuous phase while PS or copolymer rich in styrene units is formed mostly in the core of monomer‐swollen particles. © 2000 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 38: 2284–2291, 2000     

Synthesis of cross-linked core-shell polymer particles by free-radical dispersion copolymerization of 4-vinylpyridine with polystyrene macromonomers in nonaqueous media

Cross-linked core-shell polymer particles were synthesized by free-radical dispersion copolymerization of 4-vinylpyridine (4VP) and various kinds of cross-linking reagents with methacryloyl-terminated polystyrene (PS) macromonomers in nonaqueous media such as 1,4-dioxane and cyclohexane. Well-defined particles were obtained by copolymerization of 4VP with ethylene glycol dimethacrylate (EGDM) in a dioxane medium. The particle diameters (D(n)=40-990 nm) decreased drastically both with increasing the feed concentration ratio of macromonomer to 4VP, [PS-M]/[4VP], and with increasing molecular weight of PS-M macromonomers. The particle size distribution (D(w)/D(n)) was in the range 1.02-1.10. PS-M macromonomers acted not only as comonomers but also as stabilizers. The particle diameters obtained in dioxane were smaller than those obtained in cyclohexane. Thus, we observed a tendency to smaller particle size as the media became more soluble for PS-M macromonomer.     

Agglomération contrôlée de latex par formation de complexes tensioactifs anioniques : copolymères à blocs à base de poly(oxyde d’éthylène)

For polystyrene–poly(ethylene oxide) (PS–PEO) diblock copolymers, as micellar dispersions in aqueous medium, the formation of complexes with anionic surfactants, such as sodium dodecylsulfate (SDS) could be confirmed. The number of SDS molecules fixed per EO unit is close to the values reported for the SDS–PEO homopolymer interaction. Advantage of this type of complexation was taken to develop a controlled agglomeration process for SDS stabilized PS and PVC latexes by using as agglomerants ‘hairy’ latexes of PS and PVC that have been synthesized in the presence of PS–PEO block copolymers and that carry therefore a fringe of PEO sequences on their surface. The complexation of SDS by these surface-anchored PEO chains leads to the destabilization of the anionic latex, which has a tendency to precipitate onto the surface of the agglomerant latex. The average particle size and the size distribution of the agglomerated particles were studied as a function of the weight and number ratio of the two types of latexes involved in the agglomeration process, as well as in function of the surface coverage by SDS and PEO respectively. By adjusting these parameters, it was possible to obtain, with an efficiency of almost 100%, latex agglomerates with a monomodal distribution in the size range of 1 to 40 μm. An agglomeration mechanism could be outlined taking into account the complexation capacity and the specific surface of the agglomerating ‘hairy’ latex. To cite this article: P. Peter et al., C. R. Chimie 6 (2003).     

Segregation of Coronal Chains in Micelles Formed by Supramolecular Interactions

Summary: Spherical micelles have been formed by mixing, in DMF, a poly(styrene)‐block‐poly(2‐vinylpyridine)‐block‐poly(ethylene oxide) (PS‐block‐P2VP‐block‐PEO) triblock copolymer with either poly(acrylic acid) (PAA) or a tapered triblock copolymer consisting of a PAA central block and PEO macromonomer‐based outer blocks. Noncovalent interactions between PAA and P2VP result in the micellar core while the outer corona contains both PS and PEO chains. Segregation of the coronal chains is observed when the tapered copolymer is used.

Inclusion of comb‐like chains with short PEO teeth in the corona triggers the nanophase segregation of PS and PEO as illustrated here (PS = polystyrene; PEO = poly(ethylene oxide)).     

Synthesis of microspheres stabilized sterically with two-component grafted chains by dispersion copolymerizations using mixture of two macromonomers in nonaqueous media

The polymer microspheres were synthesized by dispersion copolymerization of divinylbenzene (DVB) with two vinylbenzyl-terminated poly(ethylene glycol methylether) (PEG)/poly(t-butyl methacrylate) (PBMA) macromonomer blends in methanol. In these systems of two macromonomer blends as the emulsifier, the polymer microspheres formed had a very narrow particle size distribution. Two macromonomers formed comicelles with DVB monomer and acted not only as the comonomer but also as the stabilizer. Such polymer microspheres were stabilized sterically with two-component grafted chains, such as PEG and PBMA, in methanol.     

The polymerisation of functionalised methacrylate monomers in supercritical carbon dioxide

This paper describes the homopolymerisations of isobornyl methacrylate (IBMA) and poly(ethylene glycol) methacrylate (PEGMA) in supercritical carbon dioxide (scCO₂) and copolymerisation with methyl methacrylate (MMA). We have used two different stabiliser systems poly(dimethyl siloxane) monomethylacrylate (PDMS-MMA) and Krytox 157FSL, both of which have been shown previously to be highly effective stabilisers for dispersion polymerisation in scCO₂. The effect of initiator concentration and copolymer composition is studied. For the copolymerisation of IBMA and MMA, under optimised conditions it is possible to form discrete particles with diameters in the range 1.4-3.6 μm. The PDMS-MMA macromonomer was found to be less effective as a stabiliser, causing particle aggregation due to the low solubility of this stabiliser in the monomers. The copolymers of PEGMA and MMA are also studied. The materials have interesting solubility properties with a transition in solubility from aqueous to organic media on increasing the MMA content.     

交联苯乙烯/丙烯酰胺共聚微球的制备及其C_(60)功能化初探

以二乙烯基苯 (DVB)为交联剂 ,利用一次投料分散共聚合的方法合成了交联的苯乙烯 (St) /丙烯酰胺 (Am )共聚微球 .实验发现 ,共聚单体Am的投料量和介质的极性对微球的形态有着显著的影响 .在反应过程中交联PS链段和PAm链段发生相分离 ,使粒子产生异形 .随后 ,通过微球上的酰胺基团与C60 的反应 ,将C60 引入微球表面 .初步的光电导性能测试表明 ,带有C60 的微球具有较好的光电导性能     

粒径可控阳离子型聚苯乙烯纳米粒子的制备及表征

在采用阳离子型双子（gemini）表面活性剂作为乳化剂,不使用任何助乳化剂的条件下,通过改进微乳液聚合工艺制备了窄分布粒径可控的阳离子型聚苯乙烯（PS）纳米乳液。 改进微乳液聚合的主要特点是：大部分苯乙烯以预乳液的形式恒速滴入引发聚合的微乳液中,使用具有高乳化性能的gemini表面活性剂作为乳化剂能明显降低乳胶粒粒径。 实验结果表明,少量阳离子单体三甲基烯丙基氯化铵作为共聚单体能够明显减小Z均粒径、降低粒度分布,乳化剂用量、引发剂用量和反应温度均能影响制备乳胶粒的粒径及其粒度分布。 乳化剂和引发剂用量分别为苯乙烯质量的5%~10%和1.0%~1.5%、反应温度为70~75 ℃时,能够制备粒径小分布窄的阳离子型聚苯乙烯纳米粒子。 Z均粒径与苯乙烯质量之间的线性关系表明,Z均粒径可以通过苯乙烯用量来控制。 不同聚合工艺下制备的聚合物粒度分布曲线表明,改进微乳液聚合工艺（半连续预乳化工艺）在制备窄分布的聚合物纳米粒子方面具有很强的优越性。     

Surface modification of iron oxide nanoparticles by a phosphate‐based macromonomer and further encapsulation into submicrometer polystyrene particles by miniemulsion polymerization

A new strategy relying on the use of a phosphate‐based macromonomer (PAM200) to modify the surface of iron oxide nanoparticles was developed for the synthesis of submicrometer polystyrene (PS) magnetic particles. First, iron oxide nanoparticles were synthesized using the coprecipitation of ferrous and ferric salts in alkaline medium. Besides the classical oleic acid (OA)/octane‐based ferrofluid, styrene‐based ferrofluids were elaborated with either OA or PAM200 as the stabilizer. In all cases, maghemite (γ‐Fe₂O₃) was clearly identified, with nanoparticles rather spherical in shape but exhibiting broad particle size distribution (PSD). Both OA and PAM200 led to stable maghemite‐based ferrofluids showing superparamagnetic properties. Further use of these ferrofluids in styrene miniemulsion polymerization resulted in inhomogeneous distribution of maghemite among and inside the polymer particles with OA‐based ferrofluids, whereas PAM200/styrene‐based ferrofluids led to magnetic particles with homogeneous distribution of maghemite inside PS particles. Broad PSD and small nonmagnetic particles were however observed. The true mechanisms operating in these systems are still to elucidate, but this study validates PAM200 as an efficient compatibilizing agent between hydrophilic maghemite and hydrophobic PS. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 327–340, 2008     

High molecular weight monodisperse polystyrene microspheres prepared by dispersion polymerization,using a novel bifunctional macromonomer

A novel bifunctional vinyl‐terminated polyurethane macromonomer was applied to the dispersion polymerization of styrene in ethanol. Monodisperse polystyrene (PS) microspheres were successfully obtained above 15 wt % of macromonomer relative to styrene. The steep slope from the reduction of the average particle size reveals that the macromonomer can efficiently stabilize higher surface area of the particles when compared with a conventional stabilizer, poly(N‐vinylpyrrolidone). The stable and monodisperse PS microspheres having the weight‐average diameter of 1.2 μm and a good uniformity of 1.01 were obtained with 20 wt % polyurethane macromonomer. The grafting ratio of the PS calculated from ¹H NMR spectra linearly increased up to 0.048 with 20 wt % of the macromonomer. In addition, the high molecular weights (501,300 g/mol) of PS with increased glass transition and enhanced thermal degradation temperature were obtained. Thus, these results suggest that the bifunctional vinyl‐terminated polyurethane macromonomer acts as a reactive stabilizer, which gives polyurethane‐grafted PS with a high molecular weight. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 3566–3573, 2005     

The influence of nano‐PS particle on structure evolution and electrical properties of PP/PS

The polypropylene‐g‐polystyrene (PP‐g‐PS) copolymers with different grafting ratios are used as compatibilizers to control the size of polystyrene (PS) particles at nanometer scale in polypropylene (PP) matrix. Then the PP/PS insulating nanocomposites (containing 10 wt % PS calculated from PS and PP‐g‐PS) are manufactured. With the increase in grafting ratio of PP‐g‐PS, the size of PS particle is reduced and the interfacial adhesion is enhanced. Meanwhile, the dielectric properties, DC breakdown strength and volume resistivity are increased with the decreasing of PS particle size. The spherulite size of PP is decreased and the boundary between crystals and amorphous regions is blurred or even disappears due to the presence of PS nanoparticles. This evolution of PP structure is attributed to the serious entanglements of PP and PS molecular chains. Finally, the correlation between morphological structure and electrical properties is ultimately established based on the in‐depth understanding of the molecular chain movement, crystal structure, and phase morphology. © 2018 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2018 , 56, 706–717     

Synthesis of monodisperse anionic submicron polystyrene particles by stabilizer-free dispersion polymerization in alcoholic media

In this work, monodisperse polystyrene (PS) particles were synthesized in ethanol/water medium using sodium salt of styrene sulfonic acid and 2,2′-azobis(isobutyronitrile) as ionic comonomer and nonionic initiator, respectively. The polymerization was carried out at low agitation speed, and no stabilizer (or surfactant) was added to the polymerization medium. This polymerization system (stabilizer-free dispersion polymerization) was initiated as a homogeneous solution of monomer, comonomer, medium, and initiator. With the production of free radicals, polymerization developed into a heterogeneous system. The effect of various polymerization conditions on the size and size distribution of the obtained particles was evaluated. The experimental results showed that with an increase in ethanol content, the size of the particles increased while no significant change was observed in particle size distribution. Furthermore, with increasing ionic comonomer content, the size of the particles decreased and their size distribution became broader. Moreover, it was observed that addition of an electrolyte to the polymerization medium also increased the particles’ size and broadened their size distribution. It is noteworthy to point out that the coagulation occurred in higher amounts of electrolyte. Finally, it is concluded that the polar component of Hansen solubility parameter of the polymerization medium affects the particle size and particle size distribution greatly.     

The role of cationic monomers in emulsion polymerization

[2-(methacryloyloxy)ethyl] trimethylammonium chloride (MATMAC), and vinylbenzyl trimethyl ammonium chloride (VBTMAC) were chosen to be used as ionic comonomers in the emulsion polymerization of styrene. The cationic nature of the two comonomers is the same (quaternary ammonium salts), however the styrene derivate (VBTMAC) is more hydrophobic than the methacrylic one (MATMAC). With the more hydrophobic cationic comonomer (VBTMAC) higher conversions were obtained due to the in situ creation of an amphiphilic copolymer with styrene and faster rates of polymerization were observed by increasing the cationic comonomer concentration. The same behavior was observed with the more hydrophilic cationic comonomer (MATMAC) at concentrations up to 0.012 M. At higher concentrations the ionic strength controls the colloidal stability of the system and coagulation occurs.     

Emulsion and dispersion polymerization of styrene in the presence of PEO macromonomers with p-vinylphenylalkyl end groups

Poly(ethylene oxide) (PEO) macromonomers with α-p-vinylphenylalkyl (propyl, pentyl, and hexyl) and ω-hydroxy end groups were applied to emulsion and dispersion polymerization of styrene as reactive emulsifiers and dispersants in water and in methanol-water mixture (9:1 v/v), respectively. Nearly monodisperse microspheres of submicron to micron size were obtained. Particle size in the emulsion system was one or half order of magnitude smaller than that in the dispersion system, while in both systems the size decreased approximately according to minus one half power of the macromonomer concentration in weight. The particle size was substantially independent on the PEO chain length and also on the spacer alkyl chain length of the α-polymerizing end group. The total weight of the PEO chains incorporated by copolymerization into the particle surfaces (shells), relative to that of styrene polymerized into the particle cores, appears to be a key factor for controlling the particle size. To cite this article: K. Landfester et al., C. R. Chimie 6 (2003).     

Ag Nanocomposite Particles: Preparation,Characterization and Application

Summary Herein, we report that different core-shell particles could be successfully used as the carrier systems for the deposition of silver nanoparticles. Firstly, thermosensitive core-shell microgel particles have been used as the carrier system for the deposition of Ag nanoparticles, in which the core consists of poly (styrene) (PS) whereas the shell consists of poly (N-isopropylacrylamide) (PNIPA) network cross-linked by N, N′-methylenebisacrylamide (BIS). Immersed in water the shell of these particles is swollen. Heating the suspension above 32 °C leads to a volume transition within the shell, which is followed by a marked shrinking of the network of the shell. Secondly, “nano-tree” type polymer brush can be used as “nanoreactor” for the generation of silver nanoparticles also. This kind of carrier particles consists of a solid core of PS onto which bottlebrush chains synthesized by the macromonomer poly (ethylene glycol) methacrylate (PEGMA) are affixed by “grafting from” technique. Thirdly, silver nanoparticles can be in-situ immobilized onto polystyrene (PS) core-polyacrylic acid (PAA) polyelectrolyte brush particles by UV irradiation. Monodisperse Ag nanoparticles with diameter of 8.5 nm, 7.5 nm and 3 nm can be deposited into thermosensitive microgels, “nano-tree” type polymer brushes and polyelectrolyte brush particles, respectively. Moreover, obtained silver nano-composites show different catalytic activity for the catalytic reduction of p-nitrophenol depending on the carrier system used for preparation.     

Design of polyglycidol-containing microspheres for biomedical applications

The paper presents a short review on the synthesis, characterisation and selected medical applications of poly(styrene/α-tert-butoxy-ω-vinylbenzyl-polyglycidol) (P(S/PGL)) microspheres. The soap-free emulsion-polymerisation of styrene and α-tert-butoxy-ω-vinylbenzyl-polyglycidol macromonomer (PGL) in water yielded core-shell microspheres with a low particle-diameter dispersity (ratio of the weight average particle diameter and the number average particle diameter). The interfacial fraction of PGL units, estimated by XPS, was in the range of 0–42 mole % depending on the concentration of the macromonomer in the polymerisation feed. The studies of adsorption of model proteins showed that the surface fraction of adsorbed protein was significantly reduced when the PGL interfacial fraction was higher than 40 mole %. The P(S/PGL) particles with covalently immobilised proteins were used for the preparation of photonic crystal assemblies suitable for applications in optical biosensors and the medical diagnostic test for the detection of Helicobacter pylori antibodies in the blood serum.