小粒径无皂阳离子PMMA胶乳粒子的制备与表征

采用溶剂热法,以AIBA为引发剂制得小粒径无皂阳离子PMMA胶乳纳米粒子。讨论了单体用量、引发剂用量和反应温度对胶乳粒径及乳液的粒径分布的影响;用^1H—NMR、TEM、FTIR、GPC、DTA等对聚合物进行了表征。结果表明：采用溶剂热法制得的无皂阳离子胶乳粒子粒径约为35nm,分散均匀;随着温度的升高,粒径逐渐减小;间同、无规、全同立构的相对含量分别为：55．3％、37．8％、6．9％;乳液的抗电解质稳定性好。     

溶剂热法制备小粒径无皂均聚物纳米胶乳粒子

采用溶剂热法，用过硫酸钾引发苯乙烯均聚，制备出分散性好、粒径约30nm的无皂聚苯乙烯肢乳纳米粒子。讨论了引发剂的用量、助溶剂丙酮的含量、反应温度对粒子尺寸及其粒径分布的影响。实验结果表明：在一定范围内，温度改变，粒径变化较快；引发剂、丙酮和单体用量改变时，粒径变化较缓慢。     

溶剂热法制备无皂P(St-MMA)纳米胶乳粒子

采用溶剂热法,在密闭容器内,以异丙醇-水为分散介质,过硫酸钾为引发剂引发苯乙烯(St)和甲基丙烯酸甲酯(MMA)共聚,制得了粒径约为60 nm的无皂聚(苯乙烯-甲基丙烯酸甲酯)纳米胶乳粒子[P(St-MMA)]。探讨了异丙醇用量和反应温度对P(St-MMA)粒径的影响,并对异丙醇-水和丙酮-水体系中的聚合速率进行了比较。实验结果表明:随着异丙醇用量的增加,P(St-MMA)粒径逐渐减小;随着反应温度的升高,P(St-MMA)粒径先减小后增大;异丙醇-水体系的聚合速率比丙酮-水体系的聚合速率快。     

小粒径无皂阳离子聚苯乙烯胶乳纳米粒子的制备与稳定

采用溶剂热法,以AIBA为引发剂引发苯乙烯均聚,制得了小粒径的无皂阳离子乳胶纳米粒子。讨论了温度对乳胶粒径、反应时间对转化率的影响以及乳液的抗电解质稳定性,结果表明：采用溶剂热法制得的无皂阳离子聚苯乙烯乳胶粒子粒径约为25nm,分散均匀;随着温度的升高粒径先减小后增大;乳液的稳定性好。     

溶剂热法制备小粒径无皂MMA/St共聚纳米胶乳粒子

溶剂热法制备小粒径无皂MMA/St共聚纳米胶乳粒子;溶剂热法;无皂乳液聚合;纳米粒子;聚(苯乙烯甲基丙烯酸甲酯)     

微波辐照下无皂阳离子聚(St-MMA)高分子纳米粒子的制备和表征

讨论了微波辐照下 ,以丙酮 水为分散介质 ,利用阳离子型自由基引发剂偶氮二异丁基脒盐酸盐(AIBA)引发苯乙烯 (St)和甲基丙烯酸甲酯 (MMA)共聚 ,合成出表面带正电荷的P(St MMA)共聚物纳米粒子 ,考察了丙酮用量、单体和引发剂浓度对纳米粒子粒径、粒径分布和乳液稳定性的影响 .结果表明 ,丙酮 水的体积比由 0增加到 1 2 6∶1时 ,粒子的平均水化半径从 12 2 2 1nm降低到 2 4 6 8nm ,粒径分布变宽 ,乳液抗电解质稳定性逐渐增强 ;增加引发剂和共聚单体MMA的浓度 ,粒子的水化半径逐渐减小 ,粒径分散系数增大 .     

无皂乳液聚合法制备非球形聚苯乙烯粒子研究

采用苯乙烯(St)、二乙烯基苯(DVB)、甲基丙烯酰氧乙基三甲基氯化铵(DMC)为单体,在乙醇和水混合介质中通过无皂乳液聚合法制备了非球形聚苯乙烯(PS)粒子。通过FT-IR、TEM和激光粒度及电位分析仪对粒子的结构、形貌、粒径以及Zeta电位进行了表征。结果表明,所合成PS粒子均含三种单体结构单元,且形貌上均为非球形;随着DVB用量的增加,PS粒子形貌更趋于球形,粒径和单分散系数均逐渐增加;随DMC用量增加,PS粒子粒径随之增加,单分散系数逐渐减小,表面Zeta电位也逐渐增加;KHCO3用量的增加能使PS粒子粒径和单分散系数均增加;随着醇水比的减小,PS粒子粒径逐渐减小,而单分散系数则逐渐增加。     

无皂乳液聚合法合成阴离子PS微球及粒径控制

以苯乙烯(St)和丙烯酸(AA)为单体,过硫酸钾(KPS)为引发剂,采用无皂乳液聚合法合成了单分散阴离子聚苯乙烯(PS)微球,并对微球结构和影响单分散性的因素进行了研究。结果表明,AA单体也已共聚到聚合物链上,AA的加入使PS微球粒径减小,并赋予PS微球表面负电性;聚合反应的活化能为42.95kJ/mol,升高聚合温度提高了反应速率;随着KPS用量的增加,PS微球粒径减小,在用量为0.6%时呈现最好单分散性;随着反应介质中丙酮含量增加,聚合物在介质中溶解度增加,使PS微球粒径有所减小,但微球粒径分布有所变宽。     

胶粒为“Salami”结构的PMMA/SiPUA乳液与膜性能研究

采用两步法,先以六亚甲基二异氰酸酯(HDI)、聚醚二元醇(N210)、端羟丙基硅油(HPMS)、端羟基丙烯酸树脂(PA-OH)为主要原料,合成了含硅聚氨酯-丙烯酸酯(Si PUA)种子乳液,然后在Si PUA乳胶粒内引入甲基丙烯酸甲酯(MMA),通过原位自由基共聚合,构筑了以Si PUA为壳,聚甲基丙烯酸甲酯(PMMA)为多核的"Salami"结构乳胶粒(PMMA/Si PUA).FTIR和DSC测试表明,聚氨酯、有机硅与丙烯酸酯发生反应,并确认了PMMA的生成;TEM结果显示,PMMA/Si PUA乳胶粒子具有"Salami"结构;随着Si PUA中HPMS含量的增加,PMMA/Si PUA乳胶粒子的粒径先增加后减小,粒径分布则从单峰窄分布变化到双峰宽分布,其乳液涂膜的水接触角呈现先增加后减小的趋势,但膜的吸水率则逐渐减小;与Si PUA相比,PMMA/Si PUA涂膜的透明性有一定下降,相分离程度增加;动态流变测试显示,PMMA/Si PUA涂膜中PMMA的存在,提高了其模量和黏度.当Si PUA中HPMS含量为10 wt%,核/壳质量比m(PMMA)/m(Si PUA)=0.5时,PMMA/Si PUA乳液的粒径较小,且为单峰分布,其涂膜的耐水性和耐高温性能较好.     

聚甲基丙烯酸甲酯乳胶膜在溶剂退火过程中的结构演变

通过乳液聚合的方法得到了单分散的聚甲基丙烯酸甲酯(PMMA)乳胶分散液,利用小角X射线散射技术得到乳胶分散液中乳胶颗粒的粒径以及粒径分布.PMMA乳胶分散液在硅片上成膜后,利用椭偏仪和扫描电子显微镜研究了其在2种溶剂退火过程中的膜厚以及结构变化.干燥后的PMMA乳胶膜在相对良溶剂丙酮的溶剂退火过程中存在粒子的形变及溶胀2个过程,而在相对不良溶剂乙醇的溶剂退火过程中仅存在粒子的溶胀过程.     

Dispersion polymerization of acrylamide. III. Partial isopropyl ester of poly(vinyl methyl ether-alt-maleic anhydride) as a stabilizer

Dispersion polymerization of acrylamide at 40 degrees C in t-butyl alcohol-water media of varying composition (50 to 90 vol% alcohol) using a partial isopropyl ester of poly(vinyl methyl ether-alt-maleic anhydride) as the stabilizer has been studied. The isopropyl ester derivative proves to be a better stabilizer than its precursor polymer. However, the particles were polydisperse in size. The number average diameter of the particles increases linearly with the solubility parameter of the dispersion medium. Dispersions of nanoparticles of polyacrylamide are produced when the t-butyl alcohol content of the dispersion medium is 90% by volume. Comparison of the particle diameter measured by transmission electron microscopy with that measured by dynamic light scattering in acetone reveals a thickness of the hairy stabilizer layer on the dispersion particles of 31 nm.     

Olivary particles: unique carbon microstructure synthesized by catalytic pyrolysis of acetone

Olivary (olive-shaped) carbon particles (OCPs) with a diameter of approximately 1.5-2 mum at the middle and a length of approximately 3-4 mum were synthesized by pyrolysis of acetone with metallic zinc as the catalyst at 600 degrees C. The content of the OCPs in the product is related to the catalyst, the pyrolysis temperature, and the time of ultrasonic dispersion before pyrolysis. The content of the OCPs was over 90% of the product under the optimum condition. Mg, Ni, Fe, Cu, Zn, and Cd powder were used as catalysts in the experiments, respectively, in which the metallic zinc powder was outstanding in the pyrolyzing process; the metallic iron and cadmium powder also improved the formation of the olivary carbon particles; however, magnesium, nickel, and copper could not operate the catalysis. Through Fourier transform infrared spectroscopy analysis, the mechanism of the formation of the olivary carbon particles was suggested to be an indirectly catalytic and self-assemble process. By high-resolution transmission electron microscope observation, an interesting arrangement of crystal planes of carbon was found that (002) planes of graphite near the surface are vertical to the surface of the OCPs and not parallel as usual.     

亲水单体对聚氨酯-含氟丙烯酸酯复合乳液颗粒和表面性能的影响

为了提高聚氨酯-丙烯酸酯聚合物的耐水性和耐溶剂性, 将N-甲基二乙醇胺(MDEA)扩链的交联聚氨酯丙酮溶液作为反应介质, 以苯乙烯、丙烯酸丁酯、含氟丙烯酸酯(FA)为单体, 过氧化苯甲酰为引发剂, 通过溶液聚合相转化法制得新型阳离子聚氨酯-含氟丙烯酸酯复合乳液. 研究了MDEA对聚合物水分散液的乳胶粒径、Zeta电位以及乳胶膜表面性能的影响, 并用FTIR, TEM对聚合物的结构和乳胶粒形态进行了表征. 结果表明, MDEA的添加利于降低乳胶粒径, 但对乳胶膜的疏水性能有不利影响, 当MDEA的质量分数为13.15%时, FPUA乳胶粒的形态呈球形, 粒径约为253 nm, 乳胶膜的表面自由能低于25.1 mJ/m², 接触角衰减速率约为0.38 (º)/min. 另外, 乳胶膜的高温处理能够使表面自由能降低11.5%以上.     

Structure and rheology of reverse micelles in dipentaerythrityl tri-(12-hydroxystearate)/oil systems

We report the formation of reverse rod-like micelles and their rheological properties in novel nonionic surfactant, dipentaerythrityl tri-(12-hydroxystearate) (designated as WO-6)/oil systems without external water addition. Small-angle X-ray scattering (SAXS) was used to investigate the structure of the micelles and their flow properties were studied by rheological measurements. We found that WO-6 spontaneously self-assembles into reverse micelles in a variety of organic solvents at ambient conditions, their structure depending on solvent molecular architecture, surfactant concentration, and temperature. Rod-like micelles with a maximum length of ca. 12 nm and a cross section diameter of ca. 2 nm were observed in cyclohexane. When cyclohexane was replaced with a linear chain octane, the length and the cross section diameter were simultaneously increased. With a further increase of hydrocarbon chain length of solvent oils from octane to hexadecane, the rod-like micelles grew axially, keeping the cross section diameter (ca. 3 nm) virtually constant. Increasing surfactant concentration also favored one-dimensional micellar growth. On the other hand, micelles shrunk with the rise of temperature, which is similar to a rod-to-sphere transition, and is essentially the opposite temperature dependence to that often observed in aqueous micellar systems. A structural picture drawn by SAXS is well supported by rheology; the relative (zero-shear) viscosity of the WO-6/oil systems was found to be markedly greater than that expected for a dispersion of spherical particles due to the elongated micellar structure, despite quantitative inconsistency with semi-empirically predicted values for rigid rod-like particles.     

Three‐Dimensionally Ordered Macroporous Syndiotactic Polystyrene: Preparation and Characterization

Summary: Three‐dimensionally ordered macroporous (3DOM) syndiotactic polystyrenes with pore size in the range of 71–286 nm were fabricated by means of silica templates using (dbm)₂Ti(OPh)₂/MAO catalytic system. The resulting materials were characterized by NMR, SEM, powder X‐ray diffraction, GPC and DSC. The results indicated that the 3DOM syndiotactic polystyrenes were highly syndiotactic, and the pore contraction increased when the average pore diameter decreased. Compared with bulk syndiotactic polystyrenes, 3DOM syndiotactic polystyrene possessed lower molecular weight, narrower molecular weight distribution, and lower crystallinity and melting temperature.

SEM image of 3DOM syndiotactic polystyrene, the inset shows the detail of the cavities.     

高浓度窄分布无皂高分子纳米粒子胶乳的制备

在微波辐照和丙酮存在下,进行了苯乙烯(ST)和甲基丙烯酸甲酯(MMA)的无皂乳液聚合.当丙酮的含量在50％以下时,可以得到稳定的窄分布的纳米粒子胶乳.丙酮的含量由0增加到50％,粒子的平均水化半径由278nm降低到35.4nm.在一定的浓度范围内,固定引发剂过硫酸钾（KPS）的用量,则粒子的平均水化半径与单体的浓度成正比;当单体浓度一定时,随着引发剂浓度的增加,粒子平均水化半径从25nm减少到22nm然后又增大.考虑到引发剂既是粒子表面电荷的来源,又增加了体系的离子强度,在粒子形成过程中,起着稳定和絮凝的双重作用,我们得到了一个简单的公式用以描述粒子的平均水化半径<R     

自成核对间同立构1,2-聚丁二烯结晶行为的影响

间同立构 1 ,2 -聚丁二烯自 1 95 5年问世以来 ,引起人们的广泛关注 ,但其形态结构方面的研究却很少报道 [1] .原因是间同立构 1 ,2 -聚丁二烯分子侧链含有大量双键 ,在较高温度下 ( >1 5 0℃ )很容易产生热交联 ,严重影响该聚合物的结晶行为 .我们曾报道了结晶性间同立构 1 ,2 -聚丁二烯的合成和溶液浇铸膜的板条状结构以及单晶结构 [2 ,3] .本文研究了间同立构 1 ,2 -聚丁二烯的自成核过程、结晶行为和形态结构 .自成核 ( Self- seeding nu-cleation)是指聚合物自身的微小晶粒作为晶核而诱导结晶生长的一种成核方式 ,它具有很高的成核效…     

Effects of guest microparticles on the swelling behavior of polyacrylamide gels

We report the effects of guest particles on the swelling properties of bulk polyacrylamide gels. The guest particles were the spheres of poly(N‐isopropylacrylamide) gel with submicrometer diameter, which were synthesized by an emulsion‐polymerized reaction in water. Polyacrylamide gels were prepared by a free radical polymerization reaction, immobilizing the gel microparticles with different concentrations at gelation. The macroscopic swelling ratio of this hybrid gel in a cylindrical shape was measured as functions of temperature and acetone concentration. The presence of guest particles was found to strongly affect the swelling behavior in the bulk gels when the concentration of incorporated particles exceeded a threshold. The experimental results indicated that the macroscopic volume in response to the temperature change should be determined by the guest particles above the threshold. On the other hand, the hybrid gel could not evidently shrink by adding acetone when the concentration of guest particles exceeded the threshold. To make clear the distribution of guest particles in the bulk networks, the fractured surfaces of dried gels were imaged by tapping mode atomic force microscopy. The guest particles were found to aggregate in the bulk homogeneous networks to form microdomains with densely connected structure, which became larger with increasing particle concentration. The roles of bulk networks as well as guest particles on the swelling behavior of hybrid gels were qualitatively discussed on the basis of the incorporated structure of guest particles, depending on the concentration of guest particles. © 2005 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 43: 1696–1704, 2005     

Immobilized Enzyme Particles Prepared by Radiation Polymerization of Polyurethane Prepolymer

The immobilization of enzymes such as cellulase by radiation polymerization of dispersed polyurethane prepolymer was studied using tolylene-2,4-diisocyanate and 2-hydroxyethyl methacrylate. The polyurethane particles were obtained by the dispersion of polyurethane prepolymer followed by radiation polymerization, in which the enzyme was immobilized on its surface by convalent bonding. The particle diameter of immobilized enzyme particles varied with monomer concentration and composition. The enzymatic activity of immobilized enzyme particles varied with the temperature of dispersion and irradiation, and decreased with increasing particle diameter.