Morphology of polystyrene/polystyrene-block-poly(methyl methacrylate)/poly(methyl methacrylate) composite particles

Polystyrene/polystyrene-block-poly(methyl methacrylate)/poly(methyl methacrylate) (PS/PS-b-PMMA/PMMA) composite particles were prepared by releasing toluene from PS/PS-b-PMMA/PMMA/toluene droplets dispersed in a sodium dodecyl sulfate aqueous solution. The morphology of the composite particles was affected by release rate of toluene, the molecular weight of PS-b-PMMA, droplet size, and polymer composition. ‘Onion-like’ multilayered composite particles were prepared from toluene droplets of PS-b-PMMA and of PS/PS-b-PMMA/PMMA, in which the weights of PS and PMMA were the same. The layer thicknesses of the latter multilayered composite particles increased with an increase in the amount of the homopolymers. PS-b-PMMA/PS composite particles had a sea-islands structure, in which PMMA domains were dispersed in a PS matrix. On the other hand, PS-b-PMMA/PMMA composite particles had a cylinder-like structure consisting of a PMMA matrix and PS domains.     

聚丙烯酸/聚丙烯酰胺/凹凸棒复合材料对亚甲基蓝的吸附性能

将聚(丙烯酸-co-丙烯酰胺)/凹凸棒复合吸附剂用于亚甲蓝的吸附,研究了时间、浓度、酸度、表面活性剂和离子强度等因素对吸附性能的影响。复合吸附剂对亚甲蓝的吸附是吸热过程,60℃时吸附量达到1 273.3 mg.g-1,吸附过程符合Langmuir单分子层吸附等温模式,并计算了热力学常数ΔG、ΔH和ΔS。在实验考察范围内吸附过程均符合准二级动力学特征。该复合吸附剂具有高吸附容量和较快的吸附速率,是良好的亚甲蓝吸附剂。     

Studies on graft copolymerization of 2-hydroxyethyl methacrylate onto poly(vinyl chloride)

Poly(vinyl chloride) was dehydrochlorinated in alkali solution and then grafted with 2-hydroxyethyl methacrylate (HEMA) using benzoyl peroxide as a free-radical initiator under a nitrogen atmosphere. The investigations involved examining the effects of grafting efficiency on various conditions, such as degree of dehydrochlorination, HEMA concentration, solvent effect, and reaction time. Maximum grafting to the extent of 57.2% was obtained. The mixed solvent grafting was attempted. © 1994 John Wiley & Sons, Inc.     

Blends of poly(2-hydroxyethyl methacrylate)/ (styrene-co-dialkyl itaconates) and poly(N-vinyl-2-pyrrolidone)/(styrene-co-dialkyl itaconates)

Summary Blends containing poly(N-vinyl-2-pyrrolidone) (PVP) and poly(hydroxyethyl methacrylate) (PHEMA) with (styrene-co-dimethyl itaconate) (Sty-co-DMI) and (styrene-co-diethylitaconate) (Sty-co-DEI) copolymers of three different compositions were studied. One Tg value over the whole range of compositions is observed for the majority of the blends, what is indicative of compatibility. The Gordon-Taylor k_GT and the Couchman k_C parameters were determined for all the blends in order to compare the strength of the interactions. The effect of the side chain structure of the copolymer on the miscibility of these blends is analyzed.     

PHEMA多孔微球和微囊的制备及生物医药应用进展

综述了聚甲基丙烯酸2-羟乙酯(PHEMA)多孔微球和微囊的研究及应用进展,重点介绍了PHEMA多孔微球和微囊的制备方法及其在生物吸附和药物载体方面的应用成果,并对其发展前景进行了展望.     

Water structure in poly(2-hydroxyethyl methacrylate): Effect of molecular weight of poly(2-hydroxyethyl methacrylate) on its property related to water

Low molecular weight poly(2-hydroxyethyl methacrylate) (polyHEMA) with a number average molecular weight (Mn) <22,600, were prepared by atom transfer radical polymerization. The molecular weight and end groups of the polyHEMA were varied, and the water content equilibrium moisture sorption and water structure were analyzed using differential scanning calorimetry (DSC) and X-ray diffractometry (XRD). Higher water content was observed for polyHEMA with Mn < 10,000. DSC revealed that the amounts of nonfreezing water are affected neither by the molecular weight nor by the end groups of the polyHEMA. On the other hand, the amount of freezing water was affected by both the molecular weight and end groups of polyHEMA, especially for polyHEMA with Mn < 20,000. The XRD-DSC measurements showed that water in polyHEMA form hexagonal ice and that the direction of crystal growth is dependent on the molecular weight. These findings indicate that the molecular weight of polyHEMA plays a significant role in the water structure in polyHEMA. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Effect of initiator on morphology in poly(vinyl acetate)/polystyrene and poly(butyl acrylate)/polystyrene composite latexes

Summary A simple method of related sensitivity range to predict thermodynamic equilibrium morphology of a core-shell latex particle (J Appl Polym Sci. 2004, 92, 3144), is recently explored. The article proposed that it is necessary to classify core-shell latex systems as sensitivity and no-sensitivity by their equilibrium morphology sensitivity to initiator and emulsifier. As for the sensitivity system, the final morphology may change by adjusting initiator and emulsifier, whereas, for the no-sensitivity system, it is hard to change its final morphology in this way. Equilibrium morphologies in system poly(vinyl acetate) (PVAc)/polystyrene (PSt) and poly(butyl acrylate) (PBA)/ PSt composite latexes particles were observed by changing initiator. Composite latexes of the two systems were synthesized by two-stage semi-continuous emulsion polymerization. The types or/and concentration of initiator changed in two stages in which the oil-soluble initiator 2,2-azobis(isobutyronitrile) (AIBN) and the water-soluble initiator potassium persulfate (KPS) were used respectively, the concentration of which was 0.5% or 2% based on the weight of monomer. The results showed that the two systems had different characteristics. At different experiment conditions designed, the same equilibrium morphologies with PSt as core and PVAc as shell were obtained in system PVAc/PSt, whereas, three different equilibrium morphologies, core-shell, inverted core-shell and hemisphere, were obtained in system PBA/PSt. The equilibrium morphology in system PVAc/PSt is no-sensitive to initiator, and the equilibrium morphology in system PBA/PSt is sensitive to initiator.     

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     

Nanostructure and crystallisation kinetics of poly(ethylene oxide)/poly(4-vinylphenol-co-2-hydroxyethyl methacrylate) blends

Blends of poly(ethylene oxide) (PEO) and poly(4-vinylphenol-co-2-hydroxyethyl methacrylate) (PVPh-HEM) were studied by means of synchrotron small and wide angle X-ray scattering (SAXS and WAXS, respectively) and by differential scanning calorimetry (DSC). The DSC measurements were used in the determination of the Flory–Huggins interaction parameter and also to study the isothermal and non-isothermal crystallisation kinetics of the PEO/PVPh-HEM blend. The interaction parameter, χ₁₂, was found to be negative (between −0.5 and −2.5, approximately) and presented a significant dependence on the blend composition, which is expected for a system with specific interactions such as hydrogen bonding. From the kinetic studies with Kissinger, Friedman and Avrami models, it was shown that crystallisation of PEO chains is slower in the blend than in the pure polymer, despite the decrease in the energy barrier to the crystallisation with the increase in PVPh-HEM concentration.

From the SAXS and WAXS profiles, the nanostructure of the blend was elucidated, exhibiting the formation of PEO lamellae even in the blends containing high concentrations of PVPh-HEM, which are non-crystalline (as observed by the WAXS profiles). The thickness of the PEO lamellae (R_c, approximately 8 nm) remains almost unchanged with the blend composition, while the crystalline peaks, observed at 19.78 and 23.98°, vanish, and the WAXS profile exhibits only a non-crystalline halo. For the non-crystalline blends with high concentrations of PVPh-HEM, PEO chains keep their crystalline structural memory.     

温度及pH敏感共聚/粘土纳米复合水凝胶的合成与性能研究

以无机粘土为交联剂制备了具有温度、pH双重敏感性的聚（N-异丙基丙烯酰胺-co-甲基丙烯酸-β-羟乙酯）/粘土纳米复合水凝胶（P（NIPA-co-HEMA）/clay）,并用红外和X衍射对其结构和形态进行了表征。在弱碱性（pH=7.4）和25℃条件下,分别研究了温度和不同pH缓冲溶液对该凝胶溶胀度的影响,测定了纳米复合水凝胶的力学性能。结果表明：水凝胶的粘土已被剥离成单片层,且均匀分散在凝胶网络中,起交联作用;P（NIPA-co-HEMA）/clay具有良好的温度、pH双重敏感特性;凝胶的断裂伸长率〉1000%。     

Well-defined poly(2-hydroxyethyl methacrylate) and its amphiphilic block copolymers via acidolysis of anionically synthesized poly(2-vinyloxyethyl methacrylate)

Summary A novel approach to a well-defined poly(2-hydroxyethyl methacrylate) [poly(HEMA)] and to its amphiphilic block copolymers was developed. The selective living anionic polymerization of the methacryloyl group of the bifunctional monomer 2-vinyloxyethyl methacrylate (VEMA) generated a functional polymer with a controlled molecular weight and a narrow molecular weight distribution (M_w/M_n= 1.05–1.09). This polymer is very stable under normal conditions. Being soluble in the common organic solvents, its characterization could be carried out easily. The unreacted vinyl groups in the side chains of the resulting polymer were further reacted with hydrochloric acid. This acidolysis changed poly(VEMA) to a well-defined poly(HEMA). In addition, the anionic block copolymerization of VEMA with styrene or methyl methacrylate also proceeded smoothly, generating the corresponding block copolymers. After acidolysis, these copolymers were turned into amphiphilic block copolymers containing a hydrophilic poly(HEMA) block. Received: 22 June 2001/Revised version: 15 August 2001/Accepted: 15 August 2001     

Free volume microprobe studies on poly(methyl methacrylate)/poly(vinyl chloride) and poly(vinyl chloride)/polystyrene blends

Blends of Poly(methyl methacrylate) (PMMA)/Poly(vinyl chloride) (PVC) and Poly(vinyl chloride) (PVC)/Polystyrene (PS) of different compositions were prepared by solution casting technique. The blends were characterized using Differential Scanning Calorimetry (DSC), Fourier Transform Infrared Spectroscopy (FTIR), and Positron Lifetime Spectroscopy. DSC data were found to be inadequate to describe whether PMMA/PVC blends are miscible or not, possibly because of the small gap in their glass transition temperatures. On the other hand, PVC/PS blends were clearly found to be immiscible by DSC. FTIR results for PMMA/PVC indicate the possible interactions between the carbonyl group of PMMA and α‐hydrogen of PVC. Free volume data derived from Positron lifetime measurements showed that the PMMA/PVC blends to be miscible in low PVC concentration domain. For the first time, the authors have evaluated the hydrodynamic interaction parameter α, advocated by Wolf and Schnell, Polymer, 42, 8599 (2001), to take into account the friction between the component molecules using the free volume data. This parameter (α) has a high value (?57) at 10 wt% of PVC, which could be taken to read miscibility for PMMA/PVC blends to be high. In the case of PVC/PS blends, the positron results fully support the DSC data to conclude the blends to be immiscible throughout the range of concentration. As expected, the hydrodynamic interaction parameter α does not show any change throughout the concentration in PVC/PS blends, further supporting the idea that α is another suitable parameter in the miscibility study of polymer blends. POLYM. ENG. SCI., 46:1231–1241, 2006. © 2006 Society of Plastics Engineers     

Phase distribution and separation in poly(2-acetoxyethyl methacrylate)/polystyrene latex interpenetrating polymer networks

A series of latex interpenetrating polymer networks (LIPNs) were prepared via two-stage soap-free emulsion polymerization of styrene on cross-linked poly(2-acetoxyethyl methacrylate) (PAEMA) seed latexes, using potassium persulfate as initiator. It was found that a compositional gradient was present when PAEMA seeds cross-linked either lightly or highly were used. The polystyrene (PS) phase is localized near the particle center in the former case, while it is segregated near the surface in the latter case. A uniform distribution of PS phase in LIPN was formed, if moderately cross-linked PAEMA seed was used. All the LIPNs appeared to be microphase-separated, and increase of cross-linking degree in seed latexes decreased the PS-rich domain size. The results were explained by the particle growth mechanism that involved the formation of surface-active oligomeric radicals in water phase, adsorption of the radicals onto monomer-swollen particle/water interface, and chain propagation in the interface with subsequent phase migration dominated by the competitive effects of thermodynamics and kinetics.     

Thermoelasticity of the poly(2-hydroxyethyl methacrylate) gel

Anomalous thermoelastic behaviour has been reported by Warren and Prins for water swollen gels of poly(2-hydroxyethyl methacrylate) (PHEMA) subjected to simple tension. The central feature of the assertion that the molecular deformation mechanism in this polymer differs radically from that of all other known long range elastomers has been the claim that the entropic component of the tensile load is negative (f_s < 0; $\text{f}{}_{\mathrm{e}}\text{f}\text{> 1}$) for certain temperatures in the range 30°–80°C. The experiments described here utilize a new technique to demonstrate, conversely, that the elasticity of the PHEMA gel is conventionally rubber-like in displaying a decrease in entropy on stretching. While confirming the similarity between PHEMA and other polymeric elastomers in this respect we note, however, an unusually large energy contribution to the tensile load ($\text{f}{}_{\mathrm{e}}\text{f}\text{= 0.78}$) which distinguishes PHEMA from all other elastomers for which the energy component of force has been measured. It is suggested that the hydrophilicity of the PHEMA molecule may account for this.     

Dynamic mechanical properties of polymer-fluid systems: characterization of poly(2-hydroxyethyl methacrylate) and poly(2-hydroxyethyl methacrylate-co-methyl methacrylate) hydrogels

The complex shear moduli of crosslinked poly(2-hydroxyethyl methacrylate) and poly(2-hydroxyethyl methacrylate-co-methyl methacrylate) hydrogels were measured as a function of water content, temperature and frequency using dynamic mechanical spectroscopy. The effect of increasing water content on both the storage and loss moduli is to lower the temperatures at which mechanical transitions occur. There is a significant decrease in the storage moduli and increase in the loss moduli dispersions with increasing water content. These data could be well correlated by a multiple-mechanism, time-temperature superposition procedure. Between 2% and 28% water content in the copolymer sample, the relaxation spectra and shift function characterizing the glassy-rubbery state transition become independent of water content when properly referenced to the observed transition temperature. At lower temperatures where the β transition occurs, the mechanical viscoelastic spectra depend much more strongly on water content although the shift factors collapse to a single curve when referenced to the observed β transition temperature.     

Grafting of 2-hydroxyethyl methacrylate and methyl methacrylate onto chrome tanned collagen fibers

Grafting of 2-hydroxyethyl methacrylate and methyl methacrylate onto chrome tanned collagen fibers, initiated by the bisulfite/pesulfate redox system, has been investigated. Using the method of statistical planning of experiments, regression equations have been obtained describing the effects of the monomers concentration and the composition of the initiating system on the monomers conversion, degree of grafting and on physical properties of grafted collagen. The relationship between the polyacrylate content in the composites prepared and their swelling ability, water absorption capacity, and the tensile strength is discussed.     

聚乙二胺改性壳聚糖微球吸附汞和铀

利用反相悬浮分散法制备壳聚糖微球,经聚乙二胺改性以提高氨基含量,考察了它对Hg2+和UO2+2的吸附性能.结果表明,吸附剂氨基含量6.52 mmol/g,粒径很小(＜10 μm),因此可快速吸附金属离子.pH＜3时可选择性分离Hg2+和UO2+2,对Hg2+和UO2+2的饱和吸附容量qm为2.20、1.41 mmol/g.动力学数据采用Lagergrent拟合,吸附速率常数kad(min-1)分别为Hg2+ 0.088,UO2+2 0.056.UO2+2和Hg2+可用1 mol/L H2SO4脱附,UO2+2还可用2 mol/L HCl脱附,脱附率＞90%.     

Preparation of heat resisting poly(methyl methacrylate)/graphite composite microspheres used as ultra‐lightweight proppants

Ultra‐lightweight heat resisting poly(methyl methacrylate) (PMMA)/graphite microspheres were successfully prepared via in situ suspension polymerization. The Fourier transform infrared and X‐ray powder diffraction results confirmed the successful preparation of the composite microspheres. Field emission scanning electron microscope analysis illustrated that the graphite particles were dispersed in microspheres and the PMMA/graphite composite microspheres had good sphericity and roundness. Furthermore, density analysis indicated that the apparent density of composites microspheres was about 1.055–1.135g/cm³ which was suitable for the transmission with water carrying. The results from thermodynamic test revealed that the thermal stability of the composite was significantly improved with increasing graphite content, which could be used as ultra‐lightweight proppant in deep underground. In addition, the crushing rate decreased to 0.5% with graphite ratio of 3.0% at the pressure of 69 MPa. Therefore, PMMA/Graphite composite microspheres exhibit a promising application in petroleum or gas exploitation as water carrying fracturing proppants. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 41924.     

Rheology and porosity control of poly(2-hydroxyethyl methacrylate) hydrogels

Swelling and dynamic mechanical behavior in a broad frequency range of homogeneous and porous poly(2-hydroxyethyl methacrylate) gels were studied in relation to their matrix structure, gel morphology and nature of the swelling medium. Very lightly cross-linked gels showed up relatively large mechanical losses caused by slow relaxation of hydrophobic physical associates still proceeding at frequency 10^?3 Hz. The macroporous gels of fused-spheres type morphology contained many dangling aggregates not bearing the stress which caused concentration of the stresses in the load bearing paths through the matrix. This is the reason for the sudden drop of storage modulus. In the α-relaxation region, the loss factors for homogeneous and porous gels merged into a single master curve. Reswelling of gels in a poor solvent caused a decrease of the swelling degree and shifted their α-relaxation to lower frequencies; reswelling in good solvent shifted the maximum of α-relaxation to higher frequencies.     

Synthesis and characterization of polypropylene-based polymer hybrids linking poly(methyl methacrylate) and poly(2-hydroxyethyl methacrylate)

Isotactic polypropylene-based polymer hybrids linking poly(methyl methacrylate) (PMMA) and poly(2-hydroxyethyl methacrylate) (PHEMA) were successfully synthesized by a graft copolymerization from maleic anhydride-modified polypropylene (PP-MAH). PP-MAH reacted with ethanolamine to produce a hydroxyl group containing polypropylene (PP-OH) and the thus obtained PP-OH was treated with 2-bromoisobutyryl bromide and converted to a 2-bromoisobutyryl group containing polypropylene (PP-Br). The metal-catalyzed radical polymerization of MMA with PP-Br was performed using a copper catalyst system in o-xylene solution at 100 °C to give the PP-based polymer hybrids linking PMMA segments (PP-PMMA hybrids). Thus obtained PP-PMMA hybrids demonstrated higher melting temperature than PP-Br and microphase-separation morphology at the nanometer level owing to the chemical linkage between both segments. On the other hand, the polymer hybrids linking PHEMA segment (PP-PHEMA hybrids) were also obtained by the radical polymerization of HEMA with PP-Br in o-xylene slurry at 25 °C. TEM observation suggested that the polymerization mainly initiated on the surface of the PP-Br powder, led to the peculiar core-shell-like morphology. These PP-PHEMA hybrid powders showed a good affinity with water due to the hydrophilicity of the PHEMA segments.