PbSe/聚甲基丙烯酸甲酯纳米复合材料的制备及表征

采用超声电化学法制备出水相硒化铅(PbSe)纳米晶体,并将其掺杂到聚甲基丙烯酸甲酯(polymethyl methacrylate,PMMA)材料中,通过本体聚合法制备出PbSe/PMMA纳米复合材科.用X射线衍射、透射电镜、扫描电镜对PbSe纳米晶体和PbSe/PMMA纳米复合材料的形貌进行了表征.结果表明:超声电化...     

高附着力丙烯酸阴极电泳涂料树脂的合成及应用

采用自由基溶液聚合法,以甲基丙烯酸四氢糠基酯(THFMA)、甲基丙烯酸羟乙酯(HEMA)、甲基丙烯酸二甲胺基乙酯(DMAEMA)、甲基丙烯酸异冰片酯(IBOMA)、N-羟甲基丙烯酰胺(NMA)等单体合成了高附着力丙烯酸阴极电泳涂料用树脂.研究树脂漆膜外观及性能的几种影响因素.实验结果表明:THFMA用量为15％,以偶氮二异丁腈为引发剂,槽液pH控制在5.8左右,可得到平整丰满漆膜,其附着力为0级,光泽可达130.4,膜厚为21.4μm.可广泛应用与五金、汽车等行业.     

EA-MMA共聚乳液合成工艺及优化

以丙烯酸乙酯(EA)和甲基丙烯酸甲酯(MMA)为共聚单体、过硫酸钾(KPS)为引发剂、十二烷基硫酸钠(SDS)和壬基酚聚氧乙烯醚(OP-10)为复合乳化剂,采用乳液聚合法合成出一种稳定的EA-MMA乳液。通过单因素试验法考察了乳化剂浓度、引发剂浓度、反应温度和反应时间等因素对乳液平均粒径和单体转化率的影响,并采用正交试验法进一步优选出制备EA-MMA乳液的最佳工艺条件。结果表明:当w(乳化剂)=2.0%、w(引发剂)=0.60%、反应时间为4 h和反应温度为80℃时,制成的EA-MMA乳液较稳定,并且单体转化率相对最高。     

Preparation and properties of transparent PMMA/ZrO2 nanocomposites using 2-hydroxyethyl methacrylate as a coupling agent

Transparent PMMA/ZrO₂ nanocomposites were prepared by in-situ bulk polymerization of methyl methacrylate (MMA)/ZrO₂ dispersions that were firstly synthesized using nonaqueous synthesized ZrO₂ nanocrystals and the function monomer, 2-hydroxyethyl methacrylate (HEMA), as the ligand. The dispersion behavior of ZrO₂ nanoparticles in MMA, structure, mechanical and thermal properties of the PMMA/ZrO₂ nanocomposites were investigated comprehensively. It was found that ZrO₂ nanoparticles were well dispersed in MMA with HEMA ligand, but the MMA/ZrO₂ dispersions easily destabilized in air as well as at elevated temperatures. The destabilization temperature of the dispersion is raised by increasing the molar ratio of HEMA/ZrO₂ to match the bulk polymerization temperature. The PMMA/ZrO₂ nanocomposites showed an interesting chemical structure (namely, highly cross-linked structure even at ZrO₂ content as low as 0.8 wt% and hydrogen bonding interaction between polymer matrix and ZrO₂ nanoparticles), with enhanced rigidity without loss of the toughness and improved thermal stability. The relationship between the structure and the properties of the PMMA/ZrO₂ nanocomposites based on the HEMA coupling agent was discussed.     

Polymer particles with a pomegranate-like internal structure via micro-dispersive polymerization in a geometrically confined reaction space I. Experimental study

The synthesis of micron-sized polymer particles with a core-shell pomegranate-like morphology is presented. The proposed polymerization technique takes advantage of a reaction-induced micro-phase separation within a suspended organic liquid droplet containing monomer, a chemical initiator, a steric stabilizer, and a poor solvent for the polymer. With an increase in monomer conversion, the monomer droplet suspended in a continuous aqueous medium is transformed first into a micro-capsule with a thick pericellular membrane, and eventually into a polymer particle packed with 300-500 nm polymer sub-particles. The experimentally observed evolution of particle morphology indicates that the reaction pathway is strongly influenced by micro-phase separation and transport phenomena. In the first stage of polymerization, a pseudo-homogeneous polymerization takes place at the droplet surface, followed by a starved macro-dispersive polymerization in the inner region where polymer precipitates out from the solvent phase as nano-sized sub-particles.     

Nanostructured thermosets from epoxy and poly(2,2,2-trifluoroethyl acrylate)-block-poly(glycidyl methacrylate) diblock copolymer: Demixing of reactive blocks and thermomechanical properties

Poly(2,2,2-trifluoroethyl acrylate)-block-poly(glycidyl methacrylate) (PTFEA-b-PGMA) diblock copolymer was synthesized via sequential reversible addition-fragmentation chain transfer (RAFT) polymerization. The reactive diblock copolymer was incorporated into epoxy to obtain the nanostructured thermosets. The morphology of the thermosets was investigated by means of atomic force microscopy (AFM) and small-angle X-ray scattering (SAXS). It is identified that the demixing of the reactive subchain (viz. PGMA) out of epoxy matrix occurred in the process of curing reaction, which exerted a profound impact on the glass transition temperatures of the nanostructured thermosets. The static contact angle measurements showed that the nanostructured thermosets displayed a significant enhancement in surface hydrophobicity as well as a reduction in surface free energy. The improvement in surface properties was attributed to the enrichment of the fluorine-containing block (i.e., PTFEA) of amphiphilic diblock copolymer on the surface of the thermosets, which was further evidenced by surface atomic force microscopy (AFM). The measurement of critical stress intensity factor (K_1C) showed that the fracture toughness of the materials was significantly enhanced by the inclusion of a small amount of PTFEA-b-PGMA diblock copolymer.     

聚丙烯酸-丙烯酸丁酯-甲基丙烯酸二甲胺乙酯共聚物水性颜料分散剂的合成及应用

以丙烯酸(AA)、丙烯酸丁酯(BA)和甲基丙烯酸二甲胺乙酯(DM)为单体,合成了AA-BA-DM三元共聚物分散剂,研究了其对二氧化钛颜料的分散效果;讨论了分散剂黏度、分散剂用量对颜料分散体系的影响;同时考察了该共聚物分散剂对不同颜料的分散稳定性。结果表明,当n(AA):n(BA):n(DM)=1.25:1:0.15,引发剂占单体总质量的1%,链转移剂占单体总质量的4%,为聚合物分散剂的最佳合成条件,所得共聚物分散剂对二氧化钛分散效果最佳,分散力达97.5%,且分散剂的用量占颜料总质量的0.80%时分散效果较好。通过对酞菁绿、二氧化钛及铬红分散效果的考察,该分散剂对颜料酞菁绿的分散效果最好,二氧化钛次之,对铬红的分散效果较差。     

PMMA成膜特性的研究

研究了PMMA膜的成膜方法、成膜特性以及作为气敏材料的应用。实验结果表明,PMMA的表面粗糙度与转速密切相关,转速越大,表面粗糙度越小。PMMA的膜厚符合液体动力学方程,旋涂速度越大,膜厚越薄。当旋涂速度为6000rpm时,可得到厚度为42nm的PMMA膜,完全符合气敏材料对膜厚的要求。     

Graft copolymerization of methyl methacrylate onto cellulosic biofibers

In this article, we have used the potassium persulfate to initiate the graft copolymerization of methyl methacrylate onto cellulosic biofibers in aqueous medium. Different reaction parameters, such as reaction time, initiator molar ratio, monomer concentration, amount of solvent, and reaction temperature, were optimized to get the maximum percentage of grafting (50.93%). The graft copolymers thus formed were characterized by Fourier transform infrared, scanning electron microscopy, X‐ray diffraction, and thermogravimetric, differential thermal analysis, and derivative thermogravimetric techniques. A mechanism is proposed to explain the generation of radicals and the initiation of graft copolymerization reactions. On grafting, percentage crystallinity decreases with reduction in its stiffness and hardness. The effect of grafting percentage on the physicochemical properties of raw as well as grafted fibers has also been investigated. The graft copolymers have been found to be more moisture resistant and also showed better chemical and thermal resistance. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011.     

Effect of surface functionalization on the physicomechanical properties of a novel biofunctional copolymer

The physicomechanical properties of functionally active poly(hydroxyethyl methacrylate‐co‐methyl methacrylate) [poly(HEMA‐co‐MMA)] are evaluated. It has been reported that the surface phosphorylated poly(HEMA‐co‐MMA) is capable of eliciting direct bone bonding when implanted in vivo. Hence, it is important to examine the physicomechanical property of the copolymer as a function of surface modification. The properties assessed are differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), equilibrium swelling, compressive strength, and dynamic mechanical analysis. According to the DSC data, the glass transition temperature, T_g of poly(HEMA‐co‐MMA) is not significantly altered by surface phosphorylation. The TGA results demonstrated that unmodified and surface phosphorylated copolymers have similar degradation profile. The differential thermal analysis further supports the data. The equilibrium swelling of functionalized poly(HEMA‐co‐MMA) in phosphate buffer saline ascertained that surface phosphorylation significantly increased the hydrophilicity of the copolymer. The study further illustrated that the percentage of equilibrium swelling appreciably increases with increase in HEMA content in the copolymer and reached a plateau after 100 h. Both compressive strength and compressive modulus of poly (HEMA‐co‐MMA) decreased due to surface phosphorylation while dynamic storage modulus value was not altered. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011