Preparation of cationic polystyrene latexes in the absence of emulsifiers

Preparation of cationic polystyrene latexes has been investigated in the absence of emulsifiers. It is clarified that a stable latex can be obtained by using 2,2′-azobis(2-amidinopropane) hydrochloride as initiator (initiator process). The latex seems to be stabilized with the fragments of the initiator chemically bound to the surface of particles. More stable latexes can be obtained by copolymerizing cationic monomers such as dialkyl aminoethyl methacrylates (copolymerization process). The stability of these latexes may predominantly be attributed to cationic monomers chemically bound to the surface of particles. Stable latexes with high solids content can be obtained by using the two-step polymerization technique in the copolymerization process. The particle formation process in the initiator process and the copolymerization process is discussed.     

Characterization of polystyrene latexes

Polystyrene latexes were prepared by emulsion polymerization. Styrene was used as monomer, potassium persulfate was the reaction initiator and sodium hydrogen carbonate was used as buffer. Surfactant may or may not be used. Three types of surfactant, ie sodium dodecylbenzene sulfonate (anionic), Triton X‐100 and Vulcastab LW (nonionic), and hexadecyltrimethyl ammonium bromide (cationic), were used. The prepared latexes were characterized according to concentration, density, pH, ionic strength, particle size, particle size distribution and surface charge. For prepared latexes with anionic surfactant, the effects of temperature, initiator concentration, surfactant concentration and amount of monomer on the latex size were investigated. Scanning electron microscopy was used as a tool for latex characterization. The results show that by increasing temperature, initiator and emulsifier concentration, the latex diameter decreases. However, size increases by increasing the amount of monomer. A potentiometric titration technique was employed for determination of surface charge. It was found that for all latexes, surface charge densities are in the same range. © 2000 Society of Chemical Industry     

Cationic latex interaction with pulp fibers. II. Modification of sheet properties by styrene butadiene latex with quaternized amino groups

Unbeaten kraft fibers covered with experimental cationic latexes were formed into sheets in which direct fiber-fiber bonds are replaced by polymeric bonds. The effect on sheet properties—breaking length, elongation at break, folding endurance, opacity, and light scattering—was evaluated as a function of latex composition. The composition was altered by either the ratios of styrene to butadiene in the polymer or by mixing soft film-forming and hard nonfilming latex. It is shown that, regardless of latex composition and mechanical properties of the polymeric film, all the latexes can modify the sheet properties to a similar extent, providing that the sheets are heated above the polymer's glass transition temperature. An improvement of tensile strength is accompanied by increased elongation. As a probable mechanism of reinforcement, it is suggested that the polymer acts as a filler of the fiber's surface irregularities, thus providing a larger contact area between fibers and an improved stress transfer between them.     

Latex–fiber interaction and paper reinforcement

A model system for studying the reinforcement of paper is provided by the use of cationic latexes. The control of pH during addition of the latex to the pulp determines the uniformity of the latex deposition on the fibers. It is demonstrated, using scanning electron microscopy and mechanical testing of the sheet, that the dry and wet strength properties are improved by the more uniform distribution of a film-forming latex. Conversely, a nonfilming latex impedes bonding to the extent that the fiber surface is covered.     

用于可再分散乳胶粉的阳离子苯丙乳液的合成

采用种子乳液聚合法,以十六烷基三甲基溴化铵(CTAB)为乳化剂,偶氮二异丁眯盐酸盐(AIBA)为引发剂,引入亲水性阳离子单体甲基丙烯酰氧乙基三甲基氯化铵(DMC)及功能性单体丙烯酰胺(AM)〔m(DMC)∶m(AM)=1∶1〕来制备用于可再分散乳胶粉的阳离子苯丙乳液。探讨了聚合反应温度、乳化剂用量、引发剂用量、种子单体用量、阳离子单体用量等对乳液及可再分散乳胶粉性能的影响。确定最佳配方和工艺条件为:聚合反应温度为(80±2)℃、DMC添加量为2%(以主要聚合单体质量计,下同)、CTAB用量为2%(以单体总质量计,下同)、AIBA用量为0.53%(以单体总质量计,下同)、种子单体用量为10.0%(以单体总质量计,下同)。在该工艺条件下,合成的阳离子苯丙乳液粒径大小和分布适中、性能稳定,由其所制得的可再分散乳胶粉含水率低、平均粒径小、再分散性优良。     

Research progress on the preparation and application of monodisperse cationic polymer latex particles

This review is focused on the features, preparation and applications of uniform cationic polymer latex particles, as well as on the formation mechanism of uniform latex particles. Substantial progress in the size and shape control of polymer latex particles has been made using several methods such as dispersion polymerization, conventional emulsion polymerization, surfactant‐free emulsion polymerization and seeded emulsion polymerization. Uniform cationic polymer latex particles have wide applications such as drug carriers, diagnostics, templates and additives. However, two major problems are the inhomogeneous size and low surface charge density, which limit further functionalization and the application of cationic polymer latex particles. Finally, the future trends and perspectives are described. Copyright © 2012 Society of Chemical Industry     

Polysiloxane/polyacrylate composite latexes with balanced mechanical property and breathability: Effect of core/shell mass ratio

Polysiloxane/polyacrylate (PSi/PA) core/shell latexes are fabricated, and the particle morphology, the film structure, as well as the properties of the latex films are investigated by comparing with blend latexes, and the relationship between structure and property is proposed. Results indicate that the structure and property of the latex films heavily depend on the particle morphology. The sea–island latex films with uniform distribution of PSi phases can be formed from the PSi/PA core/shell latexes, and with the mass ratio from 1:1 to 1:4, their tensile strength and elongation at break are close to the pure PA latex film, while the elastic recovery and water vapor permeability improve notably. It is found that the phase segregation occurs in the blend latex films, and although the blend latex films provide better water vapor breathability, their mechanical properties sacrifice obviously. Therefore, the various properties must be balanced for practical applications and the core/shell latexes are competitive for meeting the balanced requirements. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 45258.     

阳荷性天然乳胶的制备

本文选择一种阳离子表面活性剂为制取阳荷性天然胶乳的稳定剂,直接把天然胶乳与这种表面活性剂的溶液混合,制取阳荷性天然胶乳,拓宽了天然胶乳的应用范围。     

Determination of surface basic groups in cationic polystyrene latexes

Basic groups chemically bound to the surface of particles (surface basic groups) in cationic polystyrene latexes prepared by using 2,2′-azobis(2-amidinopropane) hydrochloride as initiator (initiator process) or by copolymerizing dialky aminoethyl methacrylates (copolymerization process) have been determined. It is clarified that in the initiator process amidino endgroups of polymers are effectively localized on the surface of particles and the latex is sufficiently stabilized with surface amidino groups. In the copolymerization process, the neutralized form of dialkylaminoethyl methacrylates is preferably localized on the surface of particles and the latex is sufficiently stabilized with surface amino groups. A particle formation process in both cases has been proposed.     

Anchored block-copolymer surfactants for the synthesis of redispersible polystyrene latexes

Redispersible polystyrene (PS) latexes of particle sizes in the range of 200–220 nm was prepared using low-molecular-weight amphiphilic block copolymer surfactants. Latex powders were obtained by sun drying of the prepared PS latexes and were reintroduced into the solution by simple mechanical agitation/stirring without any additives. DLS and SEM analysis were carried out for pristine/sun-dried latexes to compare the size and shape of the particles. A series of block copolymers with 2-methyl-2-oxazoline and 2-butyl-2-oxazoline or 2-phenyl-2-oxazoline with repeat units 30/20, 60/20, 15/30, and 15/45 were synthesized through cationic ring opening polymerization (CROP) and were used as nonionic surfactants (NIS) in the preparation of poly(styrene) latexes by emulsion polymerization. In this work, we investigated the role of anchoring ability of butyl/phenyl groups of the block copolymer in providing stability and redispersibility of the latex by comparing with simply cetyl and stearyl surfactants that are devoid of such functionality. The ready redispersibility and retainment of size and shape as that of original latexes confirmed the role of anchoring groups. PS latexes prepared by block-copolymer surfactants that are devoid of anchoring units showed lesser stability and no redispersibility compared to anchored surfactants. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2020 , 137, 48875.