Fluorinated monomer–styrene copolymer latex particles: I. kinetic studies in a soap-free aqueous medium

Soap-free emulsion copolymerization of 2, 2, 2-trifluoroethyl acrylate (3FEA) with styrene was carried out by using potassium persulfate as an initiator, and the effects of the weight fraction of 3FEA in the monomer feed on the kinetics and the particle size were investigated. Monomer conversions were followed by a gravimetric method, revealing that the overall polymerization rate increased exponentially with an increase in the weight fraction of 3FEA. According to dynamic light scattering measurement, the final particle size was found to decrease with an increase in the weight fraction of 3FEA. The number of particles for 3FEA homopolymerization was roughly twice as large as that at the fraction of 0.9, although both fractions had the almost same polymerization rates. These results indicate that soap-free emulsion homopolymerization of 3FEA would proceed not only inside the polymer particles but also in the aqueous phase throughout the polymerization.     

Thermal behavior of some new triazole derivative complexes

A series of new complexes with mixed ligands of the type [ML(C₃H₃O₂)₂]·nH₂O (((1) M=Mn, n=1; (2) M=Co(II), n=2; (3) M=Ni(II), n=4; (4) M=Cu(II), n=1.5; (5) M=Zn(II), n=0; L=3-amino-1,2,4-triazole and (C₃H₃O₂)=acrylate anion) were synthesized and characterised by chemical analysis and IR data. In all complexes the 3-amino-1,2,4-triazole acts as bridge while the acrylate acts as bidentate ligand except for complex (5) where it is found as unidentate. The thermal behaviour steps were investigated in nitrogen flow. The thermal transformations are complex processes according to TG and DTG curves including dehydration, acrylate ion and 3-amino-1,2,4-triazole degradation respectively. The final products of decomposition are the most stable metal oxides, except for complex (4) that leads to metallic copper.     

Copolymerization of 4‐Propanoylphenyl Acrylate with Methyl Methacrylate: Synthesis,Characterization and Reactivity Ratios

The new acrylic monomer 4‐propanoylphenyl acrylate (PPA) was synthesized and copolymerized with methyl methacrylate (MMA) in methyl ethyl ketone at 70±1°C using benzoyl peroxide as a free radical initiator. The copolymers were characterized by FT‐IR, ¹H‐NMR and ¹³C‐NMR spectroscopic techniques. The compositions of the copolymers were determined by ¹H‐NMR analysis. The reactivity ratios of the monomers were determined using Fineman‐Ross (r₁=0.5535 and r₂=1.5428), Kelen‐Tüdös (r₁=0.5307 and r₂=1.4482), and Ext. Kelen‐Tüdös (r₁=0.5044 and r₂=1.4614), as well as by a nonlinear error‐in‐variables model (EVM) method using a computer program, RREVM (r₁=0.5314 and r₂=1.4530). The solubility of the polymers was tested in various polar and non‐polar solvents. The elemental analysis was determined by a Perkin‐Elmer C‐H analyzer. The molecular weights (M_w and M_n) of the copolymers were determined by gel permeation chromatography. Thermogravimetric analysis of the polymers reveals that the thermal stability of the copolymers increases with an increase in the mole fraction of MMA in the copolymers. Glass transition temperatures of the copolymers were found to increase with an increase in the mole fraction of MMA in the copolymers.     

Poly(acrylate‐b‐styrene‐b‐isobutylene‐b‐styrene‐b‐acrylate) Block Copolymers via Carbocationic and Atom Transfer Radical Polymerizations

A series of polyacrylate‐polystyrene‐polyisobutylene‐polystyrene‐polyacrylate (X‐PS‐PIB‐PS‐X) pentablock terpolymers (X=poly(methyl acrylate) (PMA), poly(butyl acrylate) (PBA), or poly(methyl methacrylate) (PMMA)) was prepared from poly (styrene‐b‐isobutylene‐b‐styrene) (PS‐PIB‐PS) block copolymers (BCPs) using either a Cu(I)Cl/1,1,4,7,7‐pentamethyldiethylenetriamine (PMDETA) or Cu(I)Cl/tris[2‐(dimethylamino)ethyl]amine (Me₆TREN) catalyst system. The PS‐PIB‐PS BCPs were prepared by quasiliving carbocationic polymerization of isobutylene using a difunctional initiator, followed by the sequential addition of styrene, and were used as macroinitiators for the atom transfer radical polymerization (ATRP) of methyl acrylate (MA), n‐butyl acrylate (BA), or methyl methacrylate (MMA). The ATRP of MA and BA proceeded in a controlled fashion using either a Cu(I)Cl/PMDETA or Cu(I)Cl/Me₆TREN catalyst system, as evidenced by a linear increase in molecular weight with conversion and low PDIs. The polymerization of MMA was less controlled. ¹H‐NMR spectroscopy was used to elucidate pentablock copolymer structure and composition. The thermal stabilities of the pentablock copolymers were slightly less than the PS‐PIB‐PS macroinitiators due to the presence of polyacrylate or polymethacrylate outer block segments. DSC analysis of the pentablock copolymers showed a plurality of glass transition temperatures, indicating a phase separated material.     

Kinetic Study of Radical Polymerization VIII. A Comprehensive Study of Solution Copolymerization of Vinyl Acetate and Methyl Acrylate by 1H‐NMR Spectroscopy

Radical copolymerization reaction of vinyl acetate (VA) and methyl acrylate (MA) was performed in a solution of benzene‐d₆ using benzoyl peroxide (BPO) as the initiator at 60°C. Kinetic studies of this copolymerization reaction were investigated by on‐line ¹H‐NMR spectroscopy. Individual monomer conversions vs. reaction time, which was followed by this technique, were used to calculate the overall monomer conversion, as well as the monomer mixture and the copolymer compositions as a function of time. Monomer reactivity ratios were calculated by various linear and nonlinear terminal models and also by simplified penultimate model with r _2(VA)=0 at low and medium/high conversions. Overall rate coefficient of copolymerization was calculated from the overall monomer conversion vs. time data and k _p  . k _t ^?0.5 was then estimated. It was observed that k _p  . k _t ^?0.5 increases with increasing the mole fraction of MA in the initial feed, indicating the increase in the polymerization rate with increasing MA concentration in the initial monomer mixture. The effect of mole fraction of MA in the initial monomer mixture on the drifts in the monomer mixture and copolymer compositions with reaction progress was also evaluated experimentally and theoretically.     

Preparation and properties of water‐absorbent composites of chloroprene rubber,starch, and sodium acrylate

The effects of the amounts of starch, sodium acrylate (NaAA) and dicumyl peroxide (DCP) on the properties of chloroprene rubber (CR)/starch/NaAA composites prepared by melting method were investigated. The results showed that the addition of starch improved the mechanical properties, but decreased the water‐absorbing capacity of the composite, most likely due to the decrease in the local concentration of the main water‐absorbing material sodium polyacrylate and the increase in crosslinking density of the composite resulting from the reaction between starch and CR. This reaction was verified by the vulcanized curves, DSC curves, and the cut surface morphology. The as‐prepared composite demonstrated higher water‐absorbing capacity, resulting from the incorporation of NaAA. The mechanical properties decreased with increasing the DCP loading, and the water‐absorbing ratio is the maximum at 1.0 phr DCP. The tensile strength of the composite decreased significantly after water immersion, due to the absorbed water acting as a plasticizer. The extracted component from composites after water immersion is mainly sodium polyacrylate according to Fourier transform infrared (FT‐IR) spectroscopy analysis. The morphology of the composites before and after water immersion was observed by optical transmission microscopy (OTM). The results indicated that the starch exhibits a good dispersion state, and the water‐absorbing capacity results primarily from sodium polyacrylate. Copyright © 2010 John Wiley & Sons, Ltd.     

淀粉接枝丙烯酸乙酯及其增容性

研究了在挤出机中采用高温和剪切力的作用直接引发淀粉与丙烯酸乙酯的接枝共聚合反应．讨论了反应条件对接枝反应的影响，研究了接枝物在淀粉与聚乙烯共混物中的增容作用．实验结果表明，高温和剪切力可以引发淀粉与丙烯酸乙酯的接枝共聚合反应．接枝物作为增容剂，可以明显地改善淀粉与聚乙烯共混物的力学性能和流变性能．     

基于石墨烯的毒死蜱分子印迹电化学传感器的制备及对毒死蜱的测定

利用分子印迹技术,以马来松香丙烯酸乙二醇酯为交联剂,使用自由基热聚合法在石墨烯修饰的玻碳电极表面合成毒死蜱( CPF)分子印迹聚合膜,制得了CPF分子印迹电化学传感器。采用循环伏安法、线性扫描伏安法和电化学交流阻抗法等,考察了此CPF分子印迹膜的电化学性能。在最佳检测条件下,传感器的峰电流与CPF浓度在2.0×10-7~1.0×10-5mol/L范围内呈线性关系,线性方程为Ip(μA)=-7.1834-0.2424C (μmol/L),相关系数r2=0.9959,检出限为6.7×10-8 mol/L(S/N=3)。构建了CPF分子印迹电化学传感器的动力学吸附模型,测得印迹传感器的印迹因子β=2.59,结合速率常数k=12.2324 s。传感器表现出良好的重现性和稳定性,并成功用于实际水样和蔬菜样品中CPF的测定,加标回收率为94.1%~101.4%。     

Novel photopolymerizable biodegradable triblock polymers for tissue engineering scaffolds: synthesis and characterization

For use in micro-patterned scaffolds in tissue engineering, novel diacrylated triblock macromers (PLA-b-PCL-b-PLA, PGA-b-PCL-b-PGA and PCL-b-PEO-b-PCL) were synthesized and characterized by Fourier transform infrared spectroscopy (FTIR), nuclear magnetic resonance spectroscopy (NMR) and gel permeation chromatography (GPC). All diacrylated polymers were designed as triblock copolymers and involved biodegradable blocks of relatively non-polar epsilon-caprolactone (CL) and polar monomers such as glycolide (GA), lactide (LA) or ethylene oxide (EO). All triblock polymers were prepared in molecular weights of a few kilo daltons via the anionic ring-opening polymerization (ROP) of the corresponding lactide, glycolide or caprolactone using stannous octoate [Sn(Oct)(2)] as catalyst. The polymers had low polydispersity indices, ranging from 1.23 to 1.56. Biodegradable polymeric networks were prepared with conversions of 72-84% via photopolymerization of the triblock diacrylated polymers with 2,2-dimethoxy-2-phenylacetophenone (DMPA) as photoinitiator. PLA-b-PCL-b-PLA copolymers crumbled easily and were not suitable for micro-patterning. PGA-b-PCL-b-PGA copolymers had higher water contact angles than PCL-b-PEO-b-PCL and were also cytocompatible with Fibroblasts 3T3.     

热处理对超疏水性含氟丙烯酸酯共聚物膜表面性能的影响

以微乳液聚合法和溶液聚合法制备丙烯酸全氟烷基乙基酯和甲基丙烯酸甲酯的共聚物, 以1,1,2-三氟三氯乙烷为溶剂, 采用溶剂挥发成膜法直接制备出超疏水膜, 并研究120 ℃热处理对超疏水膜表面性能的影响. 对于用乳液聚合方法制备的超疏水膜, 随着热处理时间的延长, 滚动角表现出先逐渐增大直至完全不能滚动, 然后重新回复到极小滚动角的特殊变化过程, 而静态接触角只是略微减小, 完全不同于热处理对平滑的含氟聚合物表面接触角的影响. 扫描电镜结果显示, 聚合物膜表面形貌对应出现从微/纳复合粗糙结构到微孔粗化并重新形成微/纳复合多层粗糙结构的变化.