Controlled preparation and properties of acrylic acid epoxy-acrylate composite emulsion for self-crosslinking coatings

A stable epoxy-acrylate composite latex was successfully prepared through emulsion polymerization of modified epoxy acrylic (EPAC) oligomer with acrylate monomer. The EPAC oligomer was obtained using active acrylic acid (AA) to react with epoxy resin. And by regulating the reaction degree of the active hydrogen of AA and epoxide group, there is the acquisition of terminal double bond that gives EPAC reactivity, together with the partial retention of the epoxide group that enables self-crosslinking during film formation. The structural conformation of the oligomer was ascertained by Fourier transform infrared (FTIR) spectroscopy. The factors influencing the stability of the epoxy-acrylate composite latex were investigated. The epoxy-acrylate composite latex was the most stable when methyl acrylic acid was 1.5 wt% and modified EPAC oligomer was 15 wt% of the total monomer weight. The morphology and property of the composite latex films were characterized by scanning electron microscopy, transmission electron microscopy (TEM), and temperature-modulated differential scanning calorimetry (TOPEM-DSC). The results confirm that there is successful emulsion copolymerization between modified EPAC oligomer and acrylate monomer. TEM show that the particles of epoxy-acrylate composite have a core-shell structure, and there is no free epoxy resin. The FTIR and TOPEM-DSC results reveal that the copolymer emulsion possesses self-crosslinking ability. During film formation, self-crosslinking reaction occurs between epoxide groups with carboxyl groups, giving exothermal phenomena. The thermal stability as well as the corrosion resistance of the films was analyzed. The results show outstanding thermal stability as well as corrosion resistance attributable to the crosslinking reticulation structure. It is envisaged that the epoxy-acrylate composite latex has great potential in the development of high-performance aqueous coatings.     

Monosize polystyrene latices carrying functional groups on their surfaces

In this study, monosized polystyrene (PS) latices were prepared by dispersion polymerization of styrene in isopropanol-water media using poly(acrylic acid) (PAA) as a steric stabilizer and 2,2′-azobisizobutyronitrile (AIBN) as an initiator. The effects of initiator and stabilizer concentrations, alcohol/water and monomer/dispersion medium ratio on the polymerization kinetics, and the size and monodispersity of PS latices were experimented with in a stirred reactor system. Monosize PS beads in the size range of 1.0–3.0 μm were obtained. The PS latex obtained in the first step having a diameter of 2.3 μm were used as the seed latex, and styrene/acrylate monomers, acrylic acid (AA), 2-hydroxyethyl methacrylate (HEMA), and dimethylaminoethyl methacrylate (DMAEMA) were copolymerized onto the PS latex particles. The incorporation of functional groups to the surface and bulk structure of PS was confirmed by IR, FTIR, XPS, and zeta potential measurements. © 1994 John Wiley & Sons, Inc.     

Dispersion copolymerization of methyl methacrylate and acrylic acid in polar media: effects of reaction parameters on the particle size and size distribution of the copolymer microspheres

Micron‐size functional crosslinked poly(methyl methacrylate) (PMMA) particles with narrow size distribution in the range of 1～5 µm were prepared by dispersion copolymerization in polar media with poly(N‐vinylpyrrolidone)(PVP) as steric stabilizer, 2,2′‐azobisisobutyronitrile(AIBN) as initiator and ethylene glycol dimethylacrylate (EGDMA) as crosslinking agent. The effects of functional comonomer acrylic acid (AA) concentration, contents in AIBN, EGDMA and PVP, media polarity as well as reaction temperature on the particle size and size distribution were investigated. Particle size initially increased, and then decreased with increasing AA concentration in the range of 0.7～3.5 mol l^?1, having a maximum of 5.01 µm at the concentration of 2.1 mol l^?1, while size distribution became broader. This was regarded as the result of different roles of PAA in the process. Particle size increased with decreasing media polarity and stabilizer concentration, and with increasing initiator concentration and reaction temperature. The resulting particle shapes were observed by transmission electron microscopy and the presence of carboxyl groups on the surface of the particles was confirmed by Fourier‐transform infrared spectroscopy. Copyright © 2003 Society of Chemical Industry     

Effects of glycidyl methacrylate content and addition sequence on the acrylic latexes with carboxyl groups

Acrylic latexes with epoxy and carboxyl groups have been synthesized via a two-stage emulsion polymerization process. Different contents of glycidyl methacrylate (GMA) were introduced by three addition modes to copolymerize with methyl methacrylate, butyl acrylate, acrylic acid (AA) in the presence of K₂S₂O₈. To obtain stable latexes, NaHCO₃ was employed as a buffer to compensate for the acidity from the thermal dissociation of K₂S₂O₈, and triethylamine was used to neutralize the carboxyl acid from AA. The results showed that the stable latexes with core/shell structure were synthesized by this method, and higher GMA content or addition at earlier stage led to forming the latexes with higher content of coagulum and bigger sized particles. During the formation of films, the polymer epoxy groups underwent the crosslinking reaction with carboxyl acid. When the GMA content increased or GMA was introduced at a later stage, high crosslinking extent was formed in the films. As a result, the crosslinking provided the films with improved water resistance, chemical resistance, tensile strength, hardness, abrasion resistance, and thermal stability.     

New crosslinked polymer from a rapid polymerization of acrylic acid with triaziridine‐containing compound

A triaziridine containing compound, trimethylolpropane tris(1‐aziridinepropionate) (TMPTA‐AZ), is prepared from a Michael addition of aziridine (AZ) with trimethylolpropane triacrylate (TMPTA). A rapid polymerization of acrylic acid (AA) with TMPTA‐AZ occurred at ambient temperature without catalyst. This polymerization process involves three subsequent reactions are proposed: (1) An exothermic neutralization takes place between AA and TMPTA‐AZ. (2) That neutralization heat triggers AZ ring‐opening reaction and that carboxyl group (of AA) plays as a nucleophile and results in an amino ester bond formation. (3) A final crosslinked polymer is obtained from that amino group reacts with its acrylic double bond via an intermolecular Michael addition reaction. These new crosslinked polymers with various performance properties are obtained from a mixture of AA and TMPTA‐AZ in different ratios and post‐heating. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 104: 809–815, 2007     

聚丙烯蜡固-固相变材料的制备与工艺优化

针对聚丙烯蜡相变材料难以乳化分散、离子交联定型的问题,利用聚丙烯酸（PAA）羧基的亲水性,易离子化特性,设计了低聚合度聚丙烯酸（PAA）接枝聚丙烯蜡,以自乳化方法制备聚丙烯蜡乳液,通过常温离子交联,在水介质中、短周期内制备了聚丙烯蜡固-固相变材料（PPW SS-PCMs）。首先利用红外光谱仪、核磁共振波谱仪、扫描电子显微镜分析测试,探讨了丙烯酸的浓度及瞬时浓度对聚丙烯蜡（PPW）接枝产物自乳化能力的影响。然后,利用偏光显微镜、X射线衍射仪、差示扫描量热仪、热重分析仪对PPW接枝产物及PPW SS-PCMs的结晶性能、热稳定性做了测试和分析。结果表明：随着丙烯酸（AA）质量占比升高,定型相变材料的相变焓随AA含量的提升而下降。在一定范围内,通过提高AA瞬时浓度能提高改性PPW的自乳化能力,减少定型组分添加量。当AA、PPW、BPO质量比为0.36∶1∶0.05及滴加速率为9mL/min时,所制备的PPW SS-PCMs的结晶温度为52.46℃,结晶焓为-53.61J/g,储能效率为81.26%,具有较好的热稳定性。     

The diacetone acrylamide crosslinking reaction and its influence on the film formation of an acrylic latex

Waterborne colloidal polymers (i.e. latex) represent a promising alternative to organic solvent-based systems in coatings applications. The development of mechanical strength and hardness is often enhanced by chemical crosslinking that creates a three-dimensional network. If extensive crosslinking occurs within the particles prior to their coalescence, however, interdiffusion will be prevented. A weaker product will result. We have explored the inter-relationship between coalescence, crosslinking, and surfactant exudation in an acrylic latex containing diacetone acrylamide exploiting the “keto-hydrazide” crosslinking reaction. The complementary use of spectroscopic techniques on a model system determined that the crosslinking reaction yields an imine, not an enamine as has been proposed in some literature. Gel fraction measurements were used to probe the rate and amount of crosslinking and identified a slower rate in larger particles, suggesting that the transport of crosslinking agent is rate-limiting. The keto-hydrazide reaction was found to be acid catalyzed and favored at lower water concentration. Measurement of the latex pH relative to the polymer mass fraction during film formation clarified the expected point of onset for crosslinking in relation to particle packing. Atomic force microscopy was used to follow surface leveling relative to the competing influence of crosslinking. The rate and total amount of surfactant exudation were found to be influenced by crosslinking, particle deformability (as determined by the temperature relative to the polymer glass transition temperature), and the evaporation rate (as controlled by the relative humidity). There is evidence that surfactant exudation can be triggered by the particle deformation that occurs at film formation temperatures well above the glass transition temperature. 2007 Roon Awards winner, presented at 2007 FutureCoat! Conference, sponsored by Federation of Societies for Coatings Technology, October 3–5, 2007, in Toronto, Ontario, Canada.     

交联甲基丙烯酸甲酯/丙烯酸共聚微球羧基分布研究

用分散聚合法制备了交联甲基丙烯酸甲酯/丙烯酸(PMMA/AA)共聚微球,以电导滴定法研究了不同聚合反应条件对微球不同区域羧基分布的影响。研究结果表明增大配方中丙烯酸浓度或引发剂浓度,表面结合与被包埋的羧基含量增大,游离羧基含量降低;提高反应温度,表面结合羧基含量减小,被包埋的与游离羧基增大。 采用分散聚合法制备了交联甲基丙烯酸甲酯/丙烯酸(PMMA/AA)共聚微球,以电导滴定法研究了不同聚合反应条件对微球不同区域羧基分布的影响。研究结果表明增大配方中丙烯酸浓度或引发剂浓度,表面结合与被包埋的羧基含量增大,游离羧基含量降低;提高反应温度,表面结合羧基含量减小,被包埋的与游离羧基增大。     

Crosslinking reaction of poly(vinyl alcohol) with poly(acrylic acid) (PAA) by heat treatment: Effect of neutralization of PAA

The crosslinking reaction of poly(vinyl alcohol) (PVA) by esterification using poly(acrylic acid) (PAA) as a crosslinking reagent was investigated to obtain highly insoluble PVA materials. Blend films of PVA and PAA (PVA/PAA = 8/2) were prepared to examine the effect of degree of neutralization (DN) in PAA and heat‐treatment conditions on the degree of crosslinking reaction. The degree of crosslinking reaction varied significantly when the DN of PAA changed. The optimum DN for the crosslinking reaction was in the range of 5 to 10 mol %. In the case of unneutralized PAA, the degree of crosslinking reaction was at most 15 mol % by heat treatment for 20 min at 200°C. Applying partially neutralized PAA (DN = 10 mol %) raised the degree to about 40 mol % under the same heat‐treatment conditions. FTIR analysis revealed that the hydroxyl group of PVA in the film blended with unneutralized PAA was degraded to a greater degree than that with partially neutralized PAA as a result of heat treatment. It was found that heat treatment at a low pH condition enhances the degradation of the hydroxyl group of PVA, resulting in a decrease of the number of crosslinking sites by esterification. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 90: 2420–2427, 2003     

PAA/PEG复合水凝胶膜的制备及其性能

以丙烯酸(AA)为单体、聚乙二醇(PEG)为大分子模板、N,N-亚甲基双丙烯酰胺为交联剂、过硫酸铵为引发剂,通过自由基溶液聚合法原位聚合制备了聚丙烯酸(PAA)/PEG复合水凝胶膜,研究了PEG用量对复合水凝胶成膜性、热稳定性、溶胀性能和力学性能的影响。结果表明:成功制备了PAA/PEG复合水凝胶膜;适量PEG的引入有利于复合水凝胶成膜;PAA/PEG复合水凝胶膜的热稳定性良好;PEG的引入对水凝胶膜的吸水溶胀性能不利;适量PEG有利于提高凝胶的力学性能,复合水凝胶膜软而韧;PEG与AA质量比为0.4的PAA/PEG复合水凝胶的拉伸强度和断裂标称应变最大,分别为1.58 MPa,414%。     

Influences of feeding strategies on AA and MAA carboxylated latexes

Semibatch, power feed, and shot‐addition feeding strategies were employed to synthesize carboxylated latex under acidic conditions, using emulsion polymerization. As a source of carboxyl groups, acrylic (AA) or methacrylic acid (MAA) was used. The distribution of carboxyl groups between feeding strategies were investigated using rheology, potentiometric/conductometric titrations, transmission electron microscopy, and FT‐IR spectroscopy. Upon alkalization, particle swelling was observed using dynamic light scattering. With increasing pH, both the AA‐ and MAA‐based latexes showed significant increase in hydrodynamic diameter as a consequence of the dissociation state of carboxyl groups. However, only MAA‐based latexes exhibit very pronounced increase in viscosity and storage modulus, and were therefore characterized as gels. The effect of feeding strategies was found to be more pronounced with the MAA functionalized latexes. By employing mentioned three procedures, significant differences in the rheological behavior of the neutralized dispersions were detected. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 42062.     

Role of acrylic acid in the synthesis of core‐shell fluorine‐containing polyacrylate latex with spherical and plum blossom‐like morphology

The core‐shell fluorine‐containing polyacrylate latex was successfully synthesized by two‐stage semicontinuous emulsion copolymerization of methyl methacrylate (MMA), butylacrylate (BA), acrylic acid (AA), and dodecafluoroheptyl methacrylate (DFMA). The fluorine‐containing polyacrylate latex was characterized by Fourier transform infrared spectroscopy (FTIR), transmission electron microscopy (TEM), dynamic light scattering (DLS), zeta potential, thermal gravimetric analysis (TGA), differential scanning calorimetry (DSC). The effects of AA content on monomer conversion, polymerization stability, particle size, corsslinking degree, carboxyl groups distributions (latex surface, aqueous phase or buried in latex), as well as mechanical properties and water absorption rate of latex film were investigated. The obtained fluorine‐containing polyacrylate latex exhibited core‐shell structure with a particle size of 120–150 nm. The introduction of AA was beneficial for the increase of monomer conversion and the polymerization stability, and had little effects on the mechanical property of latex film. However, the hydrophilicity of AA made the water resistance of latex film get bad. With the increase of AA content, the carboxyl groups preferred to distribute on aqueous phase, and the possibility of homogeneous nucleation increased and more oligomers particles were formed. Moreover, the oligomers would distribute to the latex and continued to grow up, making the latex morphology changed from spherical to plum blossom‐like. The core‐shell latex had two T_g corresponding to the rubber polyacrylate core and hard fluorine‐containing polyacrylate shell, and the latex film possessed excellent thermal stability. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 42527.     

Application of Fourier transform infrared spectroscopy to study the interactions of poly(acrylic acid) and mixtures of poly(acrylic acid) and polyacrylamide with bone powders and hydroxyapatites

Fourier transform infrared (FTIR) spectroscopy was used to study the interactions of aqueous solutions of poly(acrylic acid) (PAA) and mixtures of aqueous solutions of PAA and polyacrylamide (PAAm) with chemically and thermally treated bone powders (BPs) and two commercial hydroxyapatites (HAs). An analysis of the spectra of the precipitates that resulted from the mixtures of PAA and the chemically treated samples of BP revealed that the spectra exhibited three new bands at 1544, 1552, and 1661 cm^?1. The first band was attributed to the formation of calcium–polycarboxylate resulting from the interaction between the carboxylic acid groups of PAA and the calcium ions of BP. The appearance of the other two bands, in addition to the disappearance of the band corresponding to the absorption of the acid groups of PAA, provided strong evidence for the existence of other interactions between the carboxylic acid groups and the amide groups of the organic matrix of BP. On the other hand, the FTIR spectra of the samples that resulted from the mixture of PAA and thermally treated BP and the two commercial HAs showed only a new absorption band at 1544 cm^?1. The interactions of mixtures of the aqueous solutions of PAA and PAAm, adjusted at low or high pH values, with the different BPs and HAs were examined. The mixtures of the aqueous solutions of PAA and PAAm interacted with the different BPs and two HAs, resulting in the formation of ternary PAA–BP–PAAm and PAA–HA–PAAm complexes. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2007     

Functionalization of Polyacrylic Acid with Tetrahydroxybenzene via a Homolytic Pathway: Application to Metallic Adsorption

Poly(acrylic acid) (PAA) was synthesized and chemically modified with 1,2,4,5-tetrahydroxybenzene (THB) or benzene-1,2,4,5-tetrol applying the reaction conditions of Minisci. A degree of modification of as high as 55% was obtained under optimal conditions: temperature of 70–80°C, time of 4 h, and [DHBQ]/[AA] ratio of 1.25. The synthesized PAA and its modified form, THB-PAA, were characterized by UV-visible, FT-IR, and ¹³C NMR spectroscopy. A severe degradation of the modified PAA was observed as revealed by viscometric measurements. The glass transition temperature of THB-PAA was found to be lower than that of pristine PAA, 123 versus 151°C. Potentiometric titrations of PAA and its modification, and their copper (II)-complexed polymers Cu-PAA and Cu-THB-PAA with 0.1 N aqueous NaOH, showed peculiar profiles. Study of copper (II) adsorption by the crosslinked PAA and THB-PAA resins varied with the following parameters: pH, time, temperature, ionic strength, sorbent mass, and initial copper (II) concentration. Optimal copper sorption extents of 5.5 and 23 mg/g for PAA and THB-PAA resins, respectively, were found for a pH of 5.4, a time of 3 h, a temperature of 45°C, and an ionic strength of 0. A new way of crosslinking poly(acrylic acid) and its modified form has been conceived via an oxidative decarboxylation process.     

Characteristics of poly(vinyl pyrrolidone)/poly(acrylic acid) interpolymer complex prepared by template polymerization of acrylic acid: Effect of reaction solvent and molecular weight of template

Poly(vinyl pyrrolidone) (PVP)/poly(acrylic acid) (PAA) interpolymer complexes were prepared, in ethanol or dimethylformamide (DMF), by template polymerization of acrylic acid in the presence of PVP (MW: 42.5 or 1100 K) used as the template. FTIR analysis showed that the complexes were formed through hydrogen bonding between the carboxyl groups of the PAA and the carbonyl groups of the PVP. The glass‐transition temperature (T_g) of the complex, prepared in ethanol, was higher than that of the component polymers, whereas the T_g of the complex, prepared in DMF, was located between that of the component polymers. The dissolution rate of the complex was affected by the molecular weight of the PVP and the reaction solvent. The release rate of ketoprofen from the complexes showed a pH dependency, and was slower at a lower pH. The ketoprofen release rate from the complex was controlled mainly by the dissolution rate of the complex above the pK_a of PAA (4.75) and by the diffusion rate below the pK_a. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 94: 2390–2394, 2004     

Bio- and bioelectro-catalytic properties of polyaniline/poly(acrylic acid) composite films bearing covalently-immobilized acid phosphatase

Conducting films composed of polyaniline (PANI) and poly(acrylic acid) (PAA) were prepared by electrochemical polymerization of aniline in the presence of various concentrations of PAA. The content of PAA moiety on the surface of the composite films (PANI/PAA films) was estimated by determination of carboxyl groups and found to be controlled by the concentration of PAA in polymerization solution. Acid phosphatase (ACP) was immobilized covalently on the PANI/PAA films by the condensation reaction with the carboxyl groups on the films. It was confirmed that the enzyme activity of the ACP-immobilized PANI/PAA film increased with increasing content of PAA moiety on the surface of the film, accompanying an increase in the amount of the immobilized ACP. The activity of the covalently immobilized ACP was significantly higher than that of the ACP adsorbed on the PANI/PAA film. By use of the ACP-immobilized PANI/PAA film as an enzyme electrode, bioelectrocatalytic oxidation of L-ascorbic acid 2-phosphate (ASA2P) was examined. The enzyme electrode gave the current due to the oxidation of ASA2P in proportion to the content of PAA moiety on the surface of the PANI/PAA film used, which was relevant to the activity of the covalently immobilized ACP.     

Crosslinking of latex polymers

The physicomechanical properties and processes of thermal crosslinking of latex acrylic polymer films containing functional groups of different chemical nature were studied. Improvement of properties characteristic of latex copolymers containing methylolamide groups is explained by orientated location of hydrophilic groups on the surface of latex particles during emulsion copolymerisation, that, in its turn, leads to a more ordered arrangement of macrochains. An optimum content of methylolamide groups as regards crosslinking processes was established and explained by steric location of these groups on the surfaces of latex particles. A similar optimum is not observed for crosslinking by watersoluble resin of latex copolymers containing groups of hydrophobic glycidylmethacrylate.     

Novel degradable superabsorbent materials of silicate/acrylic‐based polymer hybrids

Novel superabsorbent materials, inorganic–organic hybrids, were synthesized by polymerizing acrylic acid or acrylamide with sodium silicate without any other crosslinking agent. The crosslinking bonds of Si? O? C form through the reaction of carboxyl groups with silanol groups (Si? OH) existing in reaction system. Results of FTIR, swelling, and degrading experiments show that the crosslinking degree increased as the mol ratio of silicate increased in a certain range. The hybrids possess the properties of high absorbency and high absorption rate in both distilled water and normal saline solution. Because of the hydrolysis of Si? O? C bonds in aqueous solution, the hybrid hydrogels can degrade in days, and maybe beneficial to environment protection. This property is quite different from those superabsorbent polymer crosslinked with organic crosslinking agent. By monitoring the temperature of the reaction system, sodium silicate was also found to facilitate the trommsdorff effect in polymerization process. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 91: 936–940, 2004     

羧甲基纤维素制备高吸水性树脂的研究

以羧甲基纤维素(CMC)、丙烯酸(AA)、2-丙烯酰胺-2-甲基丙磺酸(AMPS)为原料,用过硫酸钾为引发剂,N,N’-亚甲基双丙烯酰胺为交联剂,经接枝共聚制备高吸水性树脂,讨论了反应时间、丙烯酸中和度、引发剂用量等对反应的影响。结果表明,最优工艺条件为:CMC、AA、AMPS的量分别为1,8,3.5 g,引发剂量为0.15 g,交联剂量为0.02 g,AA中和度为80%,在50℃下反应2 h。所得产物吸水倍率为580 g/g,吸水速率为80 g/m in。     

Fabrication,characterization and drug loading of pH‐dependent multi‐morpho‐ logical nanoparticles based on cellulose

This paper investigates the pH‐dependent micellization of (hydroxyethyl cellulose)‐graft‐poly(acrylic acid) (HEC‐graft‐PAA), the crosslinking of the pH‐induced nanoparticles and the drug loading of the crosslinked multi‐morphological nanoparticles. The hydrodynamic diameter (〈D_h〉) of the pH‐induced micelles was found dependent on both temperature and concentration in dynamic light scattering studies. After the crosslinking of PAA segments in the micelles, shape‐persistent nanoparticles were obtained, which exhibited multiple morphologies from nano‐cage to hollow sphere, and a homogeneous swollen microgel in neutral medium with an increase of the degree of crosslinking. To investigate the drug loading of these shape‐persistant nanoparticles, diminazene aceturate was chosen as a model drug. The loading efficiency and the drug release behavior against water and 0.1 mol L^?1 NaCl were studied using UV absorption spectroscopy. Copyright © 2007 Society of Chemical Industry