Preparation of composite polyacrylate latex particles with in situ‐formed methylsilsesquioxane cores

Composite polyacrylate latex particles were prepared through a simple method by dissolving organosilicon monomer methyltrimethoxysilane in a monomer mixture of acrylic monomers methyl methacrylate (MMA), n‐butyl acrylate (n‐BA), and acrylic acid (AA). With the addition of water needed for hydrolysis, methyltrimethoxylsilane hydrolyzed under catalysis by AA and further condensed to form polymeric methylsilsesquioxane (MSQ). The monomer mixture containing in situ‐formed MSQ was then subjected to emulsification and emulsion polymerization. Transmission electron microscopy (TEM) images showed that the obtained latex particles had a core–shell structure. Differences between the X‐ray photoelectron spectroscopy (XPS) results of the contents of silicon atoms on surfaces of films formed at temperatures above and below glass transition temperatures (T_gs) of polyacrylate evidenced that the cores were made up of MSQ and the shells were made up of polyacrylate. The static water contact angle measurements indicated that the incorporation of MSQ can result in composite latex with higher hydrophobicity. Copyright © 2009 John Wiley & Sons, Ltd.     

Synthesis and characterization of core-shell polyacrylate particles containing hindered amine light stabilizers

A polymerizable hindered amine light stabilizer (HALS) 1,2,2,6,6-pentamethylpiperidin-4-yl acrylate (PMPA) was synthesized through transesterification of 1,2,2,6,6-pentamethylpiperidin-4-ol (PMP) with methyl acrylate (MA). Core-shell latex particles containing HALS moieties in the shell phase were prepared by two-stage seeded emulsion polymerization from n-butyl acrylate (BA), methyl methacrylate (MMA) and PMPA. The Fourier transformed infrared (FTIR) and nuclear magnetic resonance (¹H NMR) analysis showed that PMPA monomer was successfully prepared and was effectively involved in the polyacrylate particles. The surface composition was studied by X-ray photoelectron spectroscopy (XPS), and the results indicated that HALS-containing groups could be distributed on the surfaces of the particles. Transmission electron microscopy (TEM) analysis revealed that the particles obtained presented a core-shell structure with a particle size around 100 nm. Two glass transition temperatures (T_g), assigned to the core phase and the shell phase of the particles, respectively, were observed for both HALS-containing and HALS-free particles, as determined by differential scanning calorimetry (DSC). In addition, the T_g value for the shell phase of HALS-containing particles was 13 °C lower than that of HALS-free particles, indicating the presence of random copolymer between MMA monomer and PMPA comonomer in the shell phase. The thermogravimetry analysis (TGA) and differential thermal gravimetric (DTG) results showed that HALS-containing particles provided an improvement in thermal stability in comparison to HALS-free particles.     

Studies on the Pseudo Ternary Phase Diagrams of Micro-emulsion Systems and Micro-emulsion Polymerization of H-PDMS/MMA/ n-BA

The pseudo phase diagrams of the systems of (OP-10/SDS)/butanediol-hydrogen-contained polymethylsiloxane (H-PDMS)/methyl methacrylate (MMA)/n-butyl acrylate (n-BA)–water, with different amounts of H-PDMS, were drawn. PDMS/P (MMA-BA) nano-composite latex particles were prepared by micro-emulsion polymerization, and the initiator was dripped into the micro-emulsion. The experiment results showed that when the amount of H-PDMS was in the range of 2.5～3.5%, the area of O/W of micro-emulsion in pseudo phase diagram was relatively large, while when the amount of H-PDMS was less than or greater than 2.5～3.5 %, the area of O/W of micro-emulsion was relatively small. In the micro-emulsion polymerization process, the average size of latex particles was dominated by the amount of initiator and the polymerization temperature. The experiment results also indicated that the size of the PDMS/P (MMA-BA) nano-composite latex particles is in the range of 26–65 nm, with the concentration of the initiator in the range of 0.6 × 10^–2-1.46×10^?2mol/L, at temperature 60–65°C.     

Nanostructured latexes made by a sequential multistage emulsion polymerization

A series of linear and lightly crosslinked nanostructured latices was prepared by a sequential multistage semicontinuous emulsion polymerization process alternating styrene (S) and n‐butyl acrylate (BA) monomer feeds five times, that is ten stages, and vice versa, along with several control latices. Transmission electron micrographs of the RuO₄‐stained cross sections of nanostructured and copolymer latex particles and films showed that their particle morphologies were not very different from each other, but the nanostructured latex particles were transformed into a nanocomposite film containing both polystyrene (PS) and poly(n‐butyl acrylate) (PBA) nanodomains interconnected by their diffuse polymer mixtures (i.e. interlayers). The thermal mechanical behaviors of the nanostructured latex films showed broad but single T_gs slightly higher than those of their counterpart copolymer films. These single T_gs indicated that their major component phases were the diffuse interlayers and that they behaved like pseudopolymer alloys. The minimum film formation temperatures of nanostructured latices capped with PBA and PS, respectively, were 15 °C lower than and equal to those of their counterpart copolymer latices, but their T_gs were about 10 °C higher. Consequently, nanostructured latices enabled us to combine good film formation with high strengths for adhesives and coatings applications. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 2826–2836, 2006     

Structure and properties of novel fluorinated polyacrylate latex prepared with reactive surfactant

The novel fluorinated polyacrylate latex was successfully prepared by emulsion polymerization of perfluorononylene allyl ether, butyl acrylate and methyl methacrylate initiated by potassium persulfate in water and emulsified with the reactive surfactant. Films of the novel fluorinated polyacrylate latex were prepared by coating the latex directly on the clean glass sheet and allowed to dry at 80°C in the bake oven. The characteristics of the film such as hydrophobicity and glass transition temperature were studied; its structure was investigated by FTIR spectrometry and NMR. The influence of the fluorinated monomer content on the emulsion polymerization and performance of the latex were also studied. It was shown that the hydrophobicity and glass transition temperature of the latex are improved when the fluorinated monomer is introduced to copolymerize with other monomers, however, the stability of emulsion polymer and the conversion rate is decreased with the increase of its content.     

Synthesis of polytetrafluoroethylene/polyacrylate core-shell nanoparticles via emulsifier-free seeded emulsion polymerization

Polytetrafluoroethylene (PTFE)/polyacrylate core-shell nanoparticles were produced via the emulsifier-free seeded emulsion polymerization of acrylate monomers with PTFE latex as seed. The monomer conversions under different synthesis parameters were monitored by a gravimetric method. The polymerization conditions for preparing PTFE/polyacrylate core-shell nanoparticles were surveyed and optimized. The chemical component of the PTFE/polyacrylate particles was confirmed by comparing the Fourier-transform infrared spectra of PTFE and PTFE/polyacrylate particles. The core-shell structure of the resulting PTFE/polyacrylate nanocomposite particles was investigated by transmission electron microscopy. The water contact angles of the films prepared from PTFE/polyacrylate nanocomposite particles showed that the films were hydrophilic, which confirmed that polyacrylate covered the surface of the PTFE particles. This kind of PTFE/polyacrylate core-shell nanoparticles might advance the compatibility of PTFE with other materials due to the covering of the polyacrylate shell on the surface of PTFE, which would make them promising in various fields.     

氯丁胶乳-聚甲基丙烯酸甲酯复合乳胶粒结构形态

以氯丁胶乳（Pa）为种子乳液,甲基丙烯酸甲酯（Pb）为第二单体,采用种子乳液聚合法,制备了氯丁胶乳-聚甲基丙烯酸甲酯复合乳胶粒。 热力学分析表明,当Pb的体积分数Φb＜0.69时,可同时形成Pa-Pb型正核-壳和（Pa＋Pb）分离型乳胶粒,当Φb＞0.69时,形成Pb-Pa型翻转型核壳结构乳胶粒,并伴有Pa-Pb型正核-壳结构乳胶粒的形成。 动力学分析表明,引发剂类型、第二单体的加入方式、种子乳胶粒的交联、单体/聚合物质量比是影响乳胶粒形态的主要因素。 采用水溶性引发剂过二硫酸钾（KPS）,以饥饿态方式加入单体,氯丁胶乳 聚甲基丙烯酸甲酯(PCR-PMMA)复合乳胶粒呈现正核-壳结构,以充溢态方式加入单体则不能形成明显的核-壳结构;而以油溶性偶氮二异丁腈（AIBN）为引发剂时,单体无论以充溢态方式加入还是饥饿态加入均倾向于形成翻转核-壳型粒子。 在种子乳胶粒中加入一定量交联剂二缩三乙二醇二甲基丙烯酸酯,有利于形成明显的正核壳结构。 以饥饿态进料,KPS为引发剂时,随着单体用量增加,壳层变厚,仍呈正核-壳结构,与热力学分析结果相吻合;以AIBN为引发剂时,随着单体用量增加,PCR-PMMA复合乳胶粒逐渐由翻转核壳型结构变为互穿结构。     

Synthesis and Characterization of Nano-silica/Polyacrylate Composite Emulsions by Sol-gel Method and in-situ Emulsion Polymerization

Organic nano-silica was firstly synthesized by sol-gel method with methyl methacrylate (MMA) and butyl acrylate (BA) in the micelles as dispersing media, tetraethoxysilicate (TEOS) as precursor, hydrochloric acid as catalyst and methacryloylpropyl trimethoxysilane (A174) as modifier. Subsequently, the nano-silica/polyacrylate composite emulsions were directly prepared by in-situ emulsion polymerization under the action of the initiator. The structure and properties were characterized by Fourier transform infrared spectroscopy (FTIR), dynamic light-scattering (DSL), thermogracvimetry (TG) and transmission electron microscopy (TEM). The results showed that A174-modified nano-silica was successfully synthesized in the acrylate-based emulsions by the sol-gel method. The nano-silica was encapsulated by polyacrylate, and the composite latex particles exhibited an apparent core-shell structure. The A174 could improve the lipophilicity of nano-silica and increase the grafting efficiency of polyacrylate on nano-silica particles. The nano-silica/polyacrylate composite latex film had better thermal stability, and the composite latex particles had greater average size and broader size distribution in contrast to those of pure polyacrylate emulsions.     

Preparation and characterization of gradient distribution of silicon in emulsion blend films

In this work, a functional gradient polymeric material derived from silicon-containing acrylate blend emulsion film is prepared in two steps. Firstly, 3-[tris(trimethylsilyloxy)silyl] propyl methacrylate (TRIS)-modified acrylate latex is prepared using multiple emulsifiers by the two-stage semicontinuous emulsion copolymerization method. Next, blend latexes composed of TRIS-containing and TRIS-free acrylate latexes are obtained. Detailed studies on the effects of the film-formation temperature and the glass transition temperature (T _g) differences on the compositional gradient film are conducted. Surface energy analysis shows that silicon elements enriched at the film-air (F-A) interface and T _g differences facilitate the fabrication of silicon gradient in emulsion blend films. Scanning electron microscopy-energy dispersive X-ray further reveals that the concentration of silicon components varies in a gradient-like manner along the overall transaction of the film when the film-formation temperature is 55 °C. However, excessive temperature creates the formation of a segmental gradient distribution of silicon in the emulsion blend films.     

Monitoring the formation of polystyrene/silica nanocomposites from vinyl triethoxysilane containing copolymers

Random copolymers of polystyrene-co-polyvinyl triethoxysilane (PS-co-PVTES) were prepared via semi-batch emulsion polymerization with different feed monomer compositions and evaluated as precursors of polystyrene (PS)/silica nanocomposites. Small-angle X-ray scattering (SAXS) profiles acquired from 20 °C to 180 °C showed that, at temperatures higher than glass transition temperature (T _g) of PS, the latex particles aggregate. On thermal annealing at 180 °C, silica-rich domains are formed, as corroborated by scanning electron microscopy. Infrared spectroscopy and differential scanning calorimetry analyses showed a reduction of the silanol concentration and an increase in the T _g value, respectively. The silica long domain spacing, measured by SAXS, depends on the concentration of vinyl triethoxysilane (VTES) in the feed; this value varied from 35 to 57 nm when the weight ratio of the monomers (styrene/VTES) was 50:50 and 90:10, respectively.     

Synthesis and Characterization of Large Dimension PBA-P(MMA-ITA) Latex Particles with Core-Shell Morphology

In this paper, a novel large dimension poly(n-butyl acrylate)-poly(methyl methacrylate-itaconic acid) (PBA-P(MMA-ITA)) core-shell latex particles (CSR) with diameter of 200 nm～300 nm were successfully synthesized via pre-emulsion and semi-continuous seeded emulsion polymerization process. The analysis on the surface tension and coagulation rate of polymeric system, size and distribution of latex particles indicated that the composite emulsifier of sodium dodecyl sulfonate/polyoxyethylene nonyl phenyl ether (SDS/OP-10) had the best emulsified effect. The optimal ratio of SDS/OP-10 was 1:1 and its optimum dosage was 1.0% of monomer amount. FTIR analysis results confirmed that ITA participated in the copolymerization reaction and the chemical bond between P(MMA-ITA) copolymer and PBA core existed in the interfacial of core and shell. DSC analysis results showed that the glass transition temperature (T _g) of P(MMA-ITA) copolymer increased with the increase of the ITA dosage and decreased with the increase of the core shell mass ratio. TEM images revealed that CSR particles had core-shell morphology indeed, but the particles’ core-shell morphology would be changed at higher ITA dosage and core shell mass ratio. The size of CSR particles was 330 nm, and the diameter of PBA core was 290 nm. ITA content in the shell of CSR particles was analyzed by non-aqueous acid-base titration. ITA content was the highest at 6% of ITA dosage, ITA amount which chemically bonded with PBA core was the highest at 8% of ITA dosage. When the core shell mass ratio was 60/40, ITA content and ITA amount which grafted onto PBA core were both the highest. ITA content of CSR particles achieved above 1.11% in this work, and it is completely possible for using CSR particles toughening and compatibilizing polyamide 6 (PA 6).     

光致变色含氟丙烯酸酯涂层的制备及性能

选取十二烷基硫酸钠(SDS),辛基苯基聚氧乙烯醚(OP-10)为复合乳化剂,过硫酸钾(KPS)为引发剂,将2-(全氟己基)乙基甲基丙烯酸酯(PFM)与丙烯酸酯类单体采用预乳化-半连续种子乳液聚合法进行乳液共聚,再将羟基螺吡喃(SPOH)与乳液进行物理共混,制得光致变色含氟丙烯酸酯乳液。 通过多种表征手段研究丙烯酸正丁酯(n-BA)和甲基丙烯酸甲酯(MMA)软硬单体的质量比,SPOH的用量对聚合反应和乳胶膜性能的影响。 结果表明,加入含氟单体后乳胶膜与水、油的接触角提高,热稳定性提高;加入SPOH的质量分数为1.25%时,乳胶膜具有较好的光致变色性能。     

SEED SEMICONTINUOUS EMULSION MULTI-COPOLYMERIZATION OF (METH) ACRYLATES WITH HIGH-SOLID CONTENT: EFFECT OF THE OPERATION CONDITIONS

The seeded semicontinuous emulsion multi-copolymerization of butyl acrylate (BA),2-ethylhexyl acrylate (2EHA), methyl methacrylate (MMA), 2-hydroxyl propyl acrylate(HOPA) and acrylic acid (AA) was used to prepare the acrylic latexes with high-solidcontent. The effects of monomer emulsion feed rates (R_a) and (R/E)_E values, the ratio ofemulsifier amount between the initial charge (R) and the addition monomer emulsion (E),on the polymerization reaction features, the viscosities, surface tensions,particle sizes andparticle sizes distributions of latexes,T_g and the insoluble fractions of films, the 180° peelstrength, tack and holding power of pressure-sensitive adhesive (PSA) tapes, preparedfrom the latexes, were studied. Experimental study shows that the grafting and cross-linking fraction in the PSA tapes must be controlled within a suitable range to keep thebalance of the 180° peel strength, tack and holding power.     

Film-forming ability and mechanical properties of coalesced latex blends

The film-forming ability of latex blends (hard latex + soft latex) and the mechanical behavior at finite strain of latex blend films (soft matrix with tough inclusions) has been investigated. The maximum weight fraction of hard latex particles (ϕ_max) which still gives rise to transparent and crack-free films has been used as film-forming ability criterion. It was shown that when the T_g of the soft latex is low (T_g(soft) < 0°C), ϕ_max is constant and equal to 0.55 because the film-forming ability is controlled by contacts between hard particles. Nevertheless, the expected effect of T_g(soft) on film-forming ability is observed (i.e., ϕ_max decreases when T_g(soft) increases) when T_g(soft) is above 0°C. From the mechanical behavior point of view, it was shown that the two main parameters controlling the mechanical behavior of latex blend films are: the mechanical properties of the soft polymer because it represents the continuous matrix and the weight fraction of hard latex particles since they enhance the local deformation of matrix under load. However, it was also proven that debounding between the T_g latex particles and low T_g matrix occurs rapidly (at an elongation ratio ≈ 30%) during uniaxial strain experiments and has to be taken into account in order to gain a thorough understanding of the mechanical behavior of these biphasic films. © 1997 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 35: 2093–2101, 1997     

Poly(Alkyl Glycidate Carbonate)s as Degradable Pressure‐Sensitive Adhesives

Insertion of CO₂ into the polyacrylate backbone, forming poly(carbonate) analogues, provides an environmentally friendly and biocompatible alternative. The synthesis of five poly(carbonate) analogues of poly(methyl acrylate), poly(ethyl acrylate), and poly(butyl acrylate) is described. The polymers are prepared using the salen cobalt(III) complex catalyzed copolymerization of CO₂ and a derivatized oxirane. All the carbonate analogues possess higher glass‐transition temperatures (T_g=32 to ?5 °C) than alkyl acrylates (T_g=10 to ?50 °C), however, the carbonate analogues (T_d≈230 °C) undergo thermal decomposition at lower temperatures than their acrylate counterparts (T_d≈380 °C). The poly(alkyl carbonates) exhibit compositional‐dependent adhesivity. The poly(carbonate) analogues degrade into glycerol, alcohol, and CO₂ in a time‐ and pH‐dependent manner with the rate of degradation accelerated at higher pH conditions, in contrast to poly(acrylate)s.     

Elaboration of fluorescent and highly magnetic submicronic polymer particles via a stepwise heterocoagulation process

Using the stepwise heterocoagulation concept, fluorescent and highly magnetic submicronic core-shell polymer particles were prepared. For this purpose a negatively charged oil-in-water magnetic emulsion was first modified by adsorbing the poly(ethyleneimine) (PEI). Secondly, low glass transition temperature (T _g=10°C) anionic film-forming nanoparticles were adsorbed onto the cationic magnetic droplets. Finally the encapsulation was induced by heating the heterocoagulates above the T _g of the film-forming nanoparticles. To produce labeled magnetic particles, fluorescent nanoparticles and film-forming nanoparticles were simultaneously adsorbed. PEI adsorption was investigated. Also investigated was the influence of the amount of film-forming nanoparticles and fluorescent nanoparticles on the encapsulation efficiency.     

Preparation and characterization of polysiloxane-poly(butyl acrylate-styrene) composite latices and their film properties

Gamma ray induced seeded emulsion co-polymerization of styrene and butyl acrylate was carried out in the presence of polymerizable polysiloxane seed latex which was obtained by the ring opening co-polymerization of octamethyl cyclotetrasiloxane (D₄) and tetramethyl tetravinyl cyclotetrasiloxane (VD₄) catalyzed by dodecylbenzene sulphonic acid (DBSA). A series of polysiloxane seed latices with different molecular weight, vinyl content, and particle size were used. The conversion-time curve showed that the polymerization rate was accelerated much by the seed latex. The obtained composite latices also showed good storage stability, mechanical stability and high electrolyte resistance ability. The morphology of the composite latex particles was found to be a quite uniform fine structure by transmission electron microscope (TEM). The graft polymerization between polymerizable polysiloxane and butyl acrylate or styrene was confirmed by the Fourier transform infrared spectroscopy (FT-IR) and the graft efficiency was also studied. The influence of seed content, molecular weight, vinyl content of the polysiloxane and seed latex particles size to the mechanical performance, water absorption ratio, surface properties, transparency and UV resistance of the latex films, was also investigated.     

Comparative study between core-shell and interpenetrating network structure polyurethane/polyacrylate composite emulsions

Anionic aqueous polyurethane dispersion was prepared by using carboxyl acid group to make the polyurethane dispersible, and then nanograde core-shell and crosslinked IPN structure polyurethane/polyacrylate composite latex (PUA) were synthesized by soap-free emulsion polymerization method with polyurethane dispersion as seed. FTIR, DSC, dynamic light scattering, TEM, ESCA, TGA, electronic tensile machine were employed to investigate the structures and properties of the composite latex and their polymers. Meanwhile the core-shell composite PUA emulsion and the crosslinked IPN composite PUA emulsion were compared. The results showed that the particle morphology of PUA composite emulsion is inverted core-shell structure with polyacrylate as the core and with polyurethane as the shell. The morphology of the crosslinked PUA emulsion was multi-core structure. The surface in core-shell PUA contains rich PU phase. The phase structure of the crosslinked PUA is more uniform. Three transition temperatures are observed for the core-shell composite PUA, two transitions are observed for the film from the crosslinked PUA. The TGA curves of core-shell PUA and crosslinked PUA exhibit two stages, the first stage corresponds to the thermal decomposition of hard segments in seed polyurethane; the second stage corresponds to the decomposition of soft segments in PUA and decomposition of polyacrylate. With the increase of glycidyl methacrylate (GMA) amounts in PUA composite emulsions, the tensile strength of the PUA films as well as the average diameter of the PUA composite emulsion particles increase, the elongation at break of the PUA films decreases.     

Properties and characterization of novel cationic polyacrylate latex containing fluorine and silicon prepared with soap-free emulsion polymerization

The novel cationic polyacrylate latex containing fluorine silicon was successfully prepared via soap-free emulsion polymerization of butyl acrylate, methyl methacrylate, vinyltriethoxysilane and hexafluorobutylmethacrylate in water phase, which were initiated with water soluble azo initiator and emulsified with the mixed surfactants polymerizable emulsifier and OP-10. The films of the resultant latex were characterized by Fourier transform infrared spectroscopy (FTIR), thermogravimetric analysis (TGA), differential scanning calorimetry (DSC) and contact angle (CA) determinator, respectively. In comparison with the conventional polyacrylate latex, the thermal stability and water resistance of novel latex film are improved. The conditions of preparing the novel cationic acrylate latexes were optimized. The optimum conditions of preparing the novel latex are as follows: the amount of emulsifiers and the initiator are 6.0% and0.3%, respectively; both the amount of VETS and amount of HFMA are 6.0%. In this case, the conversion is high and the polymerization stability is good.     

醇溶性聚丙烯酸酯乳液的合成及性能研究

以丙烯酸乙酯(EA)、甲基丙烯酸甲酯(MMA)和甲基丙烯酸(MAA)为主单体,采用过硫酸盐作引发剂,经预乳化乳液聚合工艺合成了聚丙烯酸酯乳液.讨论了乳化剂种类、单体种类以及功能性单体、引发剂加入工艺对乳液聚合过程及乳液产品性能的影响.结果表明:单体组成为m(MMA)∶m(EA)∶m(MAA)=45∶40∶15所得乳液聚合物能满足使用性能要求;种子引发剂加入质量控制在单体总质量的0.3%,而总的引发剂用量占单体总质量的0.8%较适宜.用差热分析仪和凝胶渗透色谱仪对乳液聚合物进行了表征.