Study on the synthesis of poly(methyl methacrylate)–poly(methacrylic acid) composite latex and their humidity sensitive properties

The composite latex particles of poly(methyl methacrylate)–poly(methacrylic acid) [poly(MMA–MAA)] were synthesized through either soapless seeded emulsion polymerization or a soapless emulsion copolymerization technique. The reaction kinetics, morphology, and size of latex particles, composition, glass transition temperature (T_g), and molecular weight of polymer products were studied under different experimental conditions. Moreover, this work also focused on the humidity‐sensitive properties of the polymer films fabricated by melting under the temperature of 200°C and followed by chemical modification with aqueous solution of NaOH. It is confirmed that there exists both an optimum ratio of hydrophilic to hydrophobic monomers and the initial structure of the latex particle to provide the humidity‐sensitive polyelectrolyte film with excellent water resistivity and good sensitivity to humidity. Besides, little hysteresis and quick response were observed. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 71: 47–57, 1999     

Polymer latex containing carboxylic acid functional groups. I. Synthesis of polymer latex from MMA and AA

The polymer latex of poly(MMA‐AA) was synthesized using two techniques: soapless seeded emulsion polymerization, and the soapless emulsion copolymerization technique. The reaction kinetics, morphology, composition, and size of latex particles, as well as the structure using thin‐layer chromatographic separation techniques, glass transition temperature (T_g), and molecular weight of polymer products, were studied under different experimental conditions. The reaction of the hydrophilic AA monomer took place in two places—on or in the latex particles, and in the water phase. Therefore, the polymer latex, whose size is very small and uniform, dispersed uniformly all over the PAA continuous phase. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 74: 3111–3120, 1999     

辛醇在无皂乳液聚合中的应用

提出了在无皂乳液中加入挥发性有机物质辛醇进行聚合反应 ,以提高乳液的性能及稳定性。详细讨论了各种因素对合成无皂乳液的影响 ,得出了最佳工艺条件 :辛醇的用量为单体质量的 3 0 % ;m(CH2 CHCOOC2 H5) ∶m(C6H5CHCH2 ) =1 0 0 0∶0 2 2 9;反应温度 85℃ ;反应时间3h ;恒温时间 0 5h ;乳液的 pH =8 0。加料方式 :辛醇与单体混合 ,乳化剂与水混合。实验证明 ,挥发性有机物质与极少数乳化剂的复合使用不仅提高了乳液的稳定性 ,而且也大幅度提高了乳液聚合物的性能 ,尤其是冻融稳定性得以很大的改善     

Kinetic study on the poly(methyl methacrylate) seeded soapless emulsion polymerization of styrene. III. Seeds with crosslinking

In this work, a seeded soapless emulsion polymerization was carried out with crosslinking (XL) poly(methyl methacrylate) (PMMA) as seeds, styrene as monomer, and potassium persulfate (K₂S₂O₈) as initiator to synthesize the PMMA XL–PS composite latex, which we knew as the latex interpenetrating polymer network (IPN). The morphology of the latex IPN was observed by transmission electron microscopy (TEM). It showed a core–shell structure. The kinetic data from the early stages of the reaction of seeded soapless emulsion polymerization showed that the square root of polymer yield (W_p)^1/2 was proportional to the reaction time. The reaction rate decreased with the increase of crosslinking density of PMMA seeds. The core–shell model proposed in our previous work^1–2 was modified to predict the conversion of polymerization over the entire course of the synthesis of PMMA (XL)–PS composite latex. Our modified core–shell kinetic model fitted well with the experimental data. © 1997 John Wiley & Sons, Inc. J Appl Polm Sci 65:425–438, 1997     

The characteristic properties of poly(methyl methacrylate)/polystyrene core‐shell composite polymer latex

In this study, the poly(methyl methacrylate/polystyrene (PMMA/PS) core‐shell composite latex was synthesized by the method of soapless seeded emulsion polymerization. The morphology of the PMMA/PS composite latex was core‐shell structure, with PMMA as the core and PS as the shell. The core‐shell morphology of the composite polymer latex was found to be thermally unstable. Under the effect of thermal annealing, the PS shell region first dispersed into the PMMA core region, and later separated out to the outside of the PMMA core region. This was explained on the basis of lowing interfacial tension between the PMMA and PS phases owing to the interpenetration layer. The interpenetration layer, which was located at the interface of the core and shell region, contained graft copolymer and entangled polymer chains. Both the graft copolymer and entangled polymer chains had the ability to lower the interfacial tension between the PMMA and PS phases. Also, the effect of thermal annealing on the morphology of commercial polymer/composite latex polymer blends was examined. The result showed that the core‐shell composite latex had the ability to enhance the compatibility of the components of polymer blends. The compatibilizing ability of the core‐shell composite latex was better than that of a random copolymer. Moreover, the effect of the amount of core‐shell composite latex on the morphology of the polymer blend was investigated. The polymer blends, which contained composite latex above 50% wt, showed the morphology of a double sea‐island structure. In addition, the composite latex was completely dissolved in solvent to destroy the core‐shell structure and release the entangled polymer chains, and then dried to form the entangled free composite polymer. The entangled free composite polymer had the ability to enhance the compatibility of the components of the polymer blend as usual. The weight ratio 3/7 commercial polymer/entangled free composite polymer blend showed the morphology of the phase inversion structure. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 88: 312–321, 2003     

Kinetic study on the poly(methyl methacrylate) seeded soapless emulsion polymerization of styrene. I. Experimental investigation

In this work, methyl methacrylate (MMA) and styrene (ST) were used as monomers in the first stage and second stage of polymerization, respectively, and potassium persulfate (K₂S₂O₈) was used as the initiator to synthesize the poly(methyl methacrylate)-polystyrene (PMMA/PS) composite latex by the method of two-stage soapless emulsion polymerization, i.e., PMMA seeded soapless emulsion polymerization of styrene. The morphology of the latex particles was observed by transmission electron microscopy (TEM). It showed that the composite latex particles had a core–shell structure. The particlesize distribution of the composite latex was very uniform. The kinetic data of seeded soapless emulsion polymerization showed that the square root of polymer yield (Wp)^1/2 was proportional to the reaction time in the earlier period of the reaction. The slope of the line of (Wp)^1/2 vs. reaction time was independent of the content of the seed, but proportional to 0.5 power of the initiator concentration. The gel effect was apparent after monomer droplets disappeared. A glassy effect was found in the latter period of the reaction. The number-average molecular weight of the polymers increased but the weight-average molecular weight of the polymers decreased with decrease of the MMA/ST weight ratio. The number- and weight-average molecular weight increased with decreasing the temperature significantly. © 1995 John Wiley & Sons, Inc.     

Mechanism and grafting reactions in seeded emulsion polymerization with emulsified monomer feeding

The seeded emulsion polymerization of styrene with emulsified monomer feeding was performed by polyethyl acrylate (PEA) latex as seed emulsion. It was shown that the grafting reactions occurred between two components on the composite latex particles. The loci of seeded polymerization were studied by the kinetics of grafting reaction. The highest grafting efficiency in the initial period of seeded emulsion polymerization supported the fact that the surfaces of PEA particles are the sites of polymerization of styrene. The grafting efficiency decreased with increasing monomer‐to‐polymer ratio and initiator concentration. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 72: 1495–1499, 1999     

Preparation and surface properties of core‐shell polyacrylate latex containing fluorine and silicon in the shell

The core‐shell polyacrylate latex particles containing fluorine and silicon in the shell were successfully synthesized by a seed emulsion polymerization, using methyl methacrylate (MMA) and butyl acrylate (BA) as main monomers, dodecafluoroheptyl methacrylate (DFMA), and γ‐(methacryloxy) propyltrimethoxy silane (KH‐570) as functional monomers. The influence of the amount of fluorine and silicon monomers on the emulsion polymerization process and the surface properties of the latex films were discussed, and the surface free energy of latex films were estimated using two different theoretical models. The emulsion and its films were characterized by particle size distribution (PSD) analysis, transmission electron microscopy (TEM), Fourier transform infrared spectrum (FTIR), nuclear magnetic resonance (¹H‐NMR and ¹⁹F‐NMR) spectrometry, contact angle (CA) and X‐ray photoelectron spectroscopy (XPS), differential scanning calorimetry (DSC), and thermogravimetry (TG) analysis. The results indicate that the average particle size of the latex particles is about 160 nm and the PSD is narrow, the synthesized latex particles exist with core‐shell structure, and a gradient distribution of fluorine and silicon exist in the latex films. In addition, both the hydrophobicity and thermal stability of the latex films are greatly improved because of the enrichment of fluorine and silicon at the film‐air interface, and the surface free energy is as low as 15.4 mN/m, which is comparable to that of polytetrafluoroethylene (PTFE). © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

The influence of latex blend composition on crosslinking and mechanical properties

Model reactive latices were synthesized by semicontinuous emulsion copolymerization of n‐butyl methacrylate and acetoacetoxyethyl methacrylate or dimethylaminoethyl methacrylate. The two functional latices were then blended in various ratios to study the influence of blend composition on crosslinking and mechanical properties of the resulting films. Crosslinking was quantified through swelling measurements. It was found that the crosslink density increased with increasing amounts of acetoacetoxy‐functional polymer. In addition, the crosslink density exhibited two maxima, at 30/70 and 70/30 (acetoacetoxy‐functional latex/amino‐functional latex) blend compositions. The mechanical properties of the films were quantified by dynamic mechanical analysis (DMA). It was shown that optimal mechanical properties occurred when the particles packed most efficiently at the 30/70 and 70/30 blend compositions. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 104: 3774–3779, 2007     

Synthesis and friction properties of copper/PMMA composites by soapless emulsion polymerization

Copper (Cu)‐doped polymethylmethacrylate (PMMA) composites were prepared by soapless emulsion polymerization. In this process, copper nanoparticles were modified by sodium oleate (SOA) and the surface property of Cu nanoparticles changed from hydrophilic to hydrophobic. The hydrophobic Cu nanoparticles could not only avoid the oxidation of Cu in air but also improve the compatibility between Cu nanoparticles and PMMA. The TEM micrographs revealed that Cu nanoparticles were encapsulated in PMMA polymer microspheres. In addition, the uniform Cu/PMMA composite microspheres could be synthesized in such a soapless emulsion polymerization process. It was worth mentioning that the friction property in oil was well improved when little nanocomposites were added into the base oil, which indicated that the composites can be widely used in lubricating oil. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Preparation and properties of poly[styrene‐co‐(butyl acrylate)‐co‐(acrylic acid)]/silica nanocomposite latex prepared using an acidic silica sol

BACKGROUND: Polyacrylate/silica nanocomposite latexes have been fabricated using blending methods with silica nanopowder, in situ polymerization with surface‐functionalized silica nanoparticles or sol–gel processes with silica precursors. But these approaches have the disadvantages of limited silica load, poor emulsion stability or poor film‐forming ability. RESULTS: In this work, poly[styrene‐co‐(butyl acrylate)‐co‐(acrylic acid)] [P(St‐BA‐AA)]/silica nanocomposite latexes and their dried films were prepared by adding an acidic silica sol to the emulsion polymerization stage. Morphological and rheological characterization shows that the silica nanoparticles are not encapsulated within polymer latex particles, but interact partially with polymer latex particles via hydrogen bonds between the silanol groups and the ? COOH groups at the surface of the polymer particles. The dried nanocomposite films have a better UV‐blocking ability than the pure polymer film, and retain their transparency even with a silica content up to 9.1 wt%. More interestingly, the hardness of the nanocomposite films increases markedly with increasing silica content, and the toughness of the films is not reduced at silica contents up to 33.3 wt%. An unexpected improvement of the solvent resistance of the nanocomposite films is also observed. CONCLUSION: Highly stable P(St‐BA‐AA)/silica nanocomposite latexes can be prepared with a wide range of silica content using an acidic silica sol. The dried nanocomposite films of these latexes exhibit simultaneous improvement of hardness and toughness even at high silica load, and enhanced solvent resistance, presumably resulting from hydrogen bond interactions between polymer chains and silica particles as well as silica aggregate/particle networks. Copyright © 2009 Society of Chemical Industry     

Synthesis and characterization of poly(fluorinated acrylate)/silica hybrid nanocomposites

The nanocomposite particles (NPs) with inorganic silica as core and fluorinated polymer shell have been in situ synthesized via emulsion polymerization. The chemical composition and core‐shell structure were characterized by Fourier‐transform infrared spectrometry and transmission electron microscopy. The results showed that silica nanoparticles were encapsulated in latex particles, with single‐ and multicore morphologies coexisting. Thermal gravimetric analysis also suggested the successful encapsulation of silica into NPs with enhanced thermal stability. The surface properties of the latex films produced from the core‐shell particles were also investigated by contact angle method and water absorption measurement. Both fluorinated polymer and silica contributed to less water absorption ratio and lower surface‐free energy, which was composed of larger polar component and smaller disperse component, just reversed as usual. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Synthesis and characterization of poly(butyl acrylate–methyl methacrylate)/polyaniline core–shell latexes

Poly(butyl acrylate–methyl methacrylate) [P(BA–MMA]/polyaniline (PANI) core–shell complex particles were synthesized with a two‐step emulsion polymerization method with P(BA–MMA) as the core and PANI as the shell. The first step was to prepare P(BA–MMA) latex particles as the core via soapless emulsion polymerization. The second step was to prepare P(BA–MMA)/PANI core–shell particles. Sodium dodecyl sulfate was fed into the P(BA–MMA) emulsion as a surfactant, and this was followed by the addition of the aniline monomer. A bilayer structure of the surfactant over the surfaces of the core particles was desired so that the aniline monomer could be attracted near the outer surface of the core particles. In some cases, dodecyl benzene sulfonic acid was added after 2 h when the polymerization of aniline was started. The final product was the desired core–shell particles. The morphology of P(BA–MMA) and P(BA–MMA)/PANI particles was observed with transmission electron microscopy. The thermal properties were studied with thermogravimetric analysis and differential scanning calorimetry. Furthermore, conductive films made from the core–shell latexes were prepared, and the electrical conductivities of the films were studied. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 104: 823–830, 2007     

Polymer/carbon nanotube composite emulsion prepared through ultrasonically assisted in situ emulsion polymerization

In this study, ultrasonic irradiation and in situ emulsion polymerization were combined to prepare stable poly(methyl methacrylate‐co‐n‐butyl acrylate) (P(MMA‐BA))/carbon nanotubes (CNTs) composite emulsion, which solves the dispersion problem of CNTs in the latex. Two stages were adopted. In Stage I, ultrasonically initiated in situ emulsion polymerization was conducted to disperse CNTs and prepare the seed emulsion containing polymer coated CNTs. In Stage II, conventional in situ emulsion polymerization was conducted to further enhance the monomer conversion and solid content. The dispersion behavior of MWCNTs in aqueous solution under ultrasonic irradiation was investigated by spectrophotometry. The effects of CNTs content on the emulsion stability and mechanical properties of composite film were studied. The results suggest that in the composite emulsion the long CNTs with a diameter of 20–40 nm are separated and dispersed by the formed polymer latex nanoparticles with a size of 20–40 nm. The spherical polymer latex nanoparticles adhere to the wall of CNTs to form a structure like “grapes on the twig.” The smooth, uniform, and flexible polymer/CNTs composite films were prepared from the composite emulsion. The CNTs can be individually dispersed in P(MMA‐BA)/CNTs composite film. Tensile tests suggest that with the increase in the CNTs content, the Young's modulus and the yield strength of the film increase. Only at 1 wt % CNTs, the Young's modulus increases from 124 to 289 MPa, and the yield strength is improved about ～14%. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 3123–3130, 2006     

The preparation and characteristics of poly(methyl methacrylate–methylacrylate acid)/nano-ZnO composite latex particles

In this work, poly(methyl methacrylate-co-methylacrylate acid)/ZnO (poly(MMA–MAA)/ZnO) composite latex particle was synthesized by three steps The first step was to synthesize poly(MMA–MAA) copolymer latex particles by soapless emulsion polymerization. Following the first step, the second step was to polymerize MMA, MAA and 3,3-(trimethoxysilyl) propyl methacrylate (MPS) in the presence of poly(MMA–MAA) seed latex particles to form the poly(MMA–MAA)/poly(MMA–MAA–MPS) core–shell latex particles. In the third step, the poly(MMA–MAA)/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)/poly(MMA–MAA–MPS)/ZnO composite latex. In this study, MPS with silanol groups essentially was used as the coupling agent to couple with ZnO nanoparticles, while the results of the study showed that there was not covalent bond existed between ZnO particles and polymer latex. The ZnO particles were adsorbed on the surface of polymer latex by electrostatic interaction. Besides, the linear poly(MMA–MAA)/crosslinking poly(MMA–MAA–MPS) core–shell latex particles which were synthesized in the second step were heated in the presence of ammonia to form the hollow poly(MMA–MAA–MPS) latex particles. The factors of heating time and concentration of crosslinking agent significantly influenced the morphology of hollow poly(MMA–MAA–MPS) latex particles.     

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.     

Attapulgite@polymer particles with double‐layer polymer shell via soapless seeded emulsion polymerization

Attapulgite needle encapsulated with double‐layer polymer shell (ATP@DP) were prepared by the soapless seeded emulsion polymerization of the second monomer styrene in the dispersion of the attapulgite needle encapsulated with poly(methyl methacrylate) (ATP@PMMA), which was also conducted by the soapless seeded emulsion polymerization of the first monomer methyl methacrylate with the cetyltrimethylammonium bromide (CTAB) modified attapulgite needle (org‐ATP) as seeds. The different morphologies of ATP, ATP@PMMA particles, and ATP@DP particles were characterized by transmission electron microscopy, and the encapsulation mechanism was also discussed. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Morphology,thermal property,and mechanical property of core–shell latex polymers. I. Effect of heating and pressuring on PBA/PS linear composite polymer

In this work, butyl acrylate and styrene were used as monomers in the first stage and second stage of polymerization, respectively, and potassium persulfate (K₂S₂O₈) was used as the initiator to synthesize the poly(butyl acrylate)–polystyrene (PBA/PS) composite latex by the method of two-stage soapless emulsion polymerization. The morphology of the latex particles was observed by transmission electron microscopy (TEM), which showed that the composite latex particles had a core–shell structure. The particle-size distribution of the composite latex was very uniform. A thin layer of a PBA-graft-PS copolymer was formed in between the core (PBA) and shell (PS) regions, which thus increased the compatibility between the PBA and PS phases. The process of heating and pressuring influenced the morphology, mechanical properties, and thermal properties of the PBA/PS composite polymer. © 1998 John Wiley & Sons, Inc. J Appl Polym Sci 69: 13–23, 1998     

Study on synthesis and morphology control of poly(4‐vinylpyridine‐co‐butyl acrylate)/poly(styrene‐co‐butyl acrylate) composite microspheres

Monodispersed crosslinked cationic poly(4‐vinylpyridine‐co‐butyl acrylate) [P(4VP‐BA)] seed latexes were prepared by soapless emulsion polymerization, using 2,2′‐azobismethyl(propionamidine)dihydrochloride (V₅₀) as an initiator and divinylbenzene (DVB) or ethylene glycol dimethacrylate (EGDMA) as a crosslinker. The optimum condition to obtain monodispersed stable latex was investigated. It was found that the colloidal stability of the P4VP latex can be improved by adding an adequate amount of BA (BA/4VP = 1/4, w/w), and adopting a semicontinuous monomer feed mode. Subsequently, poly(4‐vinylpyridine‐co‐butyl acrylate)/Poly(styrene‐co‐butyl acrylate) [P(4VP‐BA)/P(ST‐BA)] composite microspheres were synthesized by seeded polymerization, using the above latex as a seed and a mixture of ST and BA as the second‐stage monomers. The effects of the type of crosslinker, the degree of crosslinking, and the initiators (AIBN and V₅₀) on the morphology of final composite particles are discussed in detail. It was found that P(4VP‐BA)/P(ST‐BA) composite microspheres were always surrounded by a PST‐rich shell when V₅₀ was used as initiator, while sandwich‐like or popcorn‐like composite particles were produced when AIBN was employed. This is because the polarity of the polymer chains with AIBN fragments is lower than for the polymer with V₅₀ fragments, hence leading to higher interfacial tension between the second‐stage PST‐rich polymer and the aqueous phase, and between PST‐rich polymer and P4VP‐rich seed polymer. As a result, the seed cannot be engulfed by the PST‐rich polymer. Furthermore, the decrease of T_g of the second‐stage polymer promoted phase separation between the seeds and the PST‐rich polymer: sandwich‐like particles formed more preferably than popcorn‐like particles. It is important knowledge that various morphologies different from PST‐rich core/P4VP‐rich shell morphology, can be obtained only by changing the initiator, considering P4VP is much more hydrophilic than PST. The zeta potential of composite particles initiated by AIBN in seeded polymerization shifted from a positive to a negative charge. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 83: 1190–1203, 2002     

葡萄糖基可聚合乳化剂的合成及其在乳液压敏胶中的应用

丙烯酸酯乳液压敏胶是一类应用广泛的低VOC含量环保胶黏剂。本文合成了一种葡萄糖基可聚合乳化剂-丁基葡萄糖苷马来酸酯（BGMAH）,并采用半连续种子乳液聚合工艺制备了BGMAH改性的丙烯酸酯乳液压敏胶。通过系统考察BGMAH的结构及用量等因素对乳液粒径、乳胶膜耐水性和粘接性能的影响发现,当复合乳化剂质量分数保持3%不变,m(BGMAH):m(OP-10):m(SDS)=2:1.5:0.5时,乳胶膜的粘接性能和耐水性能最佳。红外、热稳定性等分析表明丙烯酸酯乳液在改性过程当中发生了共聚交联反应,且改性后聚合物体系相容性良好,乳胶膜的玻璃化转变温度和热稳定性均提高,同时对聚合体系的反应机理也进行了研究。