聚合时间、分散介质的配比对聚苯乙烯高分子微球表征的影响

本文采用分散聚合法制备聚苯乙烯(PS)高分子微球,通过正交实验对其表征进行研究,从而得出聚合时间、分散介质的配比对聚苯乙烯微球的粒径、分子量的影响。扫描电镜结果表明:制得的聚苯乙烯微球的平均粒径为2.24μm;黏度法测定聚苯乙烯高分子微球的平均分子质量为4.25×105;实验结果表明,聚合时间和分散介质配比对聚苯乙烯高分子微球的粒径和分子量有较大的影响。     

单分散窄分布聚苯乙烯微球的制备研究

以苯乙烯为单体,聚乙烯基吡咯烷酮(PVP)为分散剂,偶氮二异丁腈(AIBN)为引发剂,甲醇为分散介质,利用分散聚合法制备了微米级单分散聚苯乙烯微球。通过傅立叶红外分析(FT-IR),扫描电子显微镜(SEM),激光粒度分析(LPS)等方法对微球进行测试表征。研究了PVP用量对微球产物的影响。结果表明:单体的转化率随PVP用量的增加而增大,PS微球的粒径随着PVP用量的增大而减小,其粒径分布先变窄后变宽。当PVP用量为1.5%时微球的粒径分布最窄,单分散性最好。改变PVP用量可以得到不同粒径的PS微球。     

二氧化硅空心球的制备及研究

在乙醇/水的混合溶液中,采用聚乙烯吡咯烷酮（PVP）为分散剂,偶氮二异丁腈（AIBN）为引发剂,通过分散聚合法制备出聚苯乙烯（PS）微球。然后以微球为模板,PS粒子作为核,SiO_2作为壳,在600℃时经过热分解得到SiO_2空心球。通过热分析仪、扫描电子显微镜对制得的空心球进行了表征和分析,并讨论其影响因素。     

交联型单分散聚苯乙烯微球的制备

以聚乙烯吡咯烷酮（PVP）为分散剂，偶氮二异丁腈（AIBN）为引发剂，乙醇为分散介质，二乙烯基苯（DVB）为交联剂进行了苯乙烯（St）的分散聚合；讨论了引发剂、交联剂、分散剂、单体用量对聚合物粒径及分布的影响，制备了交联型单分散聚苯乙烯微球。实验表明：当交联剂质量分数达到单体质量分数的1％时，微球依然可以保持良好的单分散性。在聚合体系中引入抗坏血酸，使其与微量的氧结合，有效地提高了微球的均匀度。     

多孔性聚苯乙烯磁性微球的制备

以磁流体颗粒为核,采用乳液聚合法合成了聚苯乙烯磁性微球.用该微球作为种子,采用分散聚合法,以乙二醇/水为分散介质,聚乙二醇为分散剂,甲苯为制孔剂,进行二乙烯苯-丙烯酸-苯乙烯三元共聚物的合成,最终合成了粒径大小均匀、具有强磁响应性的多孔聚苯乙烯磁性微球.     

异丙醇-水介质中微米级单分散聚(苯乙烯-甲基丙烯酸)微球的制备

以苯乙烯和甲基丙烯酸为单体、PVP为分散剂,AIBN为引发剂,在异丙醇-水介质中,用分散聚合方法制备了微米级单分散的聚(苯乙烯-甲基丙烯酸)[P(St-MAA)]微球。结果表明,采用反应初期低温、中后期升温的聚合工艺可制得单分散的聚合物微球,并提高聚合反应的速率和转化率。P(St-MAA)微球的粒径及其分布可通过改变介质组成来控制。分散介质中异丙醇质量分数降低,聚合反应速率增大,转化率升高,微球的粒径减小。当分散介质中异丙醇的质量分数降低到60％时,聚合反应中有凝胶生成,粒径分布呈多分散性。     

有序大孔二氧化硅微球的制备研究

采用乳液聚合法合成了单分散改性聚苯乙烯（PS）乳胶粒,利用PS乳胶粒自组装制得胶体晶体（“蛋白石”）微球,通过溶胶-凝胶模板法制备了有序大孔SiO2（“反蛋白石”）微球,通过SEM对改性PS乳胶粒、胶体晶体微球和有序大孔SiO2微球表面形貌进行了表征。结果表明,改性PS乳胶粒呈单分散性,粒径为317 nm;胶体晶体微球表面PS乳胶粒排列有序;有序大孔SiO2微球表面呈有序多孔,其孔呈六边形,孔径分布均一,约为200 nm。     

磁性多孔聚苯乙烯微球的制备

在磁流体存在的情况下,采用改进了的乳液聚合法合成了具有磁核的微米级高分子聚苯乙烯微球。以该微球为种子,采用分散聚合法,以乙二醇／水为分散介质、聚乙二醇为分散剂、甲苯为制孔剂,进行苯乙烯-丙烯酸-二乙烯苯的三元共聚物的合成,最终合成出粒径分布均匀、磁响应性强的磁性多孔聚苯乙烯微球。     

单分散多孔聚合物微球的制备及其反相色谱应用

用分散聚合的方法制得单分散微米级聚苯乙烯微球(PS),以此聚苯乙烯微球作为种子,以邻苯二甲酸二丁酯为溶胀剂,苯乙烯为单体,二乙烯基苯为交联剂,甲苯为致孔剂,采用种子溶胀聚合的方法制得粒径分布较窄的多孔高交联的聚苯乙烯-二乙烯基苯微球(PS-DVB)。研究了交联剂与致孔剂的加入量对微球形貌、粒径及孔结构参数的影响。结果表明,所得多孔微球球形圆整,库尔特测得平均粒径为5.067~5.520μm,粒径分布窄,D90/D10为1.23~1.56,孔结构可控,并以此多孔微球作为反相色谱填料基质,理论塔板数每米可达6 000~15 000,可以用作高效液相色谱(HPLC)填料。     

空心球型二氧化硅担载Li_3PO_4催化剂的制备及催化效果研究

笔者以正硅酸乙酯(TEOS)为硅源,氨水溶液为催化剂,聚乙烯吡咯烷酮(PVP)功能化的聚苯乙烯为模板,在乙醇介质中利用一步法制得纳米空心二氧化硅,并用TEM、XRD、BET、TG、FTIR等表征手段对SiO_2粉体进行分析。首先,以苯乙烯(St)为单体,过硫酸铵为引发剂,聚乙烯吡咯烷酮为分散剂,水为分散介质,单分散聚合法制备功能化的聚苯乙烯,可得到平均粒径为90 nm的聚苯乙烯微球。以这种微球为模板,在乙醇/氨水介质中,正硅酸乙酯发生水解和缩合,在聚苯乙烯微球包覆形成SiO_2,同时PS核被溶解,得到纳米空心二氧化硅微球。研究氨水用量、TEOS用量及反应时间等因素对二氧化硅微球形貌和产率的影响。以空心纳米二氧化硅为Li_3PO_4催化剂载体,催化环氧丙烷的异构化,与以硅胶作为载体的Li_3PO_4催化剂的催化效果进行比较。结果表明,使用空心球形二氧化硅代替硅胶作为催化剂载体可提高环氧丙烷转化率和烯丙醇的选择性,降低反应温度和副产物选择性。     

Uniform Polystyrene Particles by Dispersion Polymerization in Different Dispersion Medium

Using PVP K-30 as steric stabilizer and AIBN as initiator, uniform polystyrene (PS) particles were prepared by dispersion polymerization of styrene in ethanol/water and isopropanol/ water media. The effects of initiator and stabilizer concentration, alcohol/water volume ratio on the average sizes and size range of PS particles were investigated. Unifrom PS particles in the size range of 0.7-1.7 μm were obtained. The results showed that higher stabilizer concentration led to PS particles with smaller average sizes, and higher initiator concentration caused greater average particle sizes. It was also found that the average sizes reduced and size ranges became narrow as the polarity (solubility parameter) of dispersion medium employed was increased.     

微米级单分散聚苯乙烯微球的制备

以苯乙烯(St)为单体、偶氮二异丁腈(AIBN)为引发剂、聚乙烯吡咯烷酮(PVP)为分散稳定剂,在乙醇-水反应介质中,采用分散聚合法制备了微米级单分散聚苯乙烯(PS)微球。分别用电镜扫描和激光粒度仪表征了PS微球表面形貌、粒径及粒度分布,探讨了影响PS微球粒径及粒度分布的诸多因素。结果表明,AIBN用量(以单体质量计,下同)大于5.0%或PVP用量(以单体质量计,下同)小于2%时,PS粒子间有聚并现象;当St浓度为10%、AIBN用量为2.5%、PVP用量为5.5%、醇水质量比为90∶10、聚合温度为70℃时,制备的PS微球粒径为1.612μm、粒度分散系数为0.357,微球单分散性及球形度最佳。     

Seeded dispersion polymerization

Micron‐size poly(n‐butyl acrylate) (PBA) and polystyrene (PSt) particles were used as seed in second‐stage seeded dispersion polymerizations. The effects of various polymerization parameters on the morphology of the structured particles resulting from the second‐stage seeded dispersion polymerizations were studied, and a series of uniform micron‐size structured particles was successfully prepared. In addition to the polymerization medium, the type of stabilizer (i.e., the molecular weight of the polyvinylpyrrolidone [PVP] stabilizer) that was used in the seed preparation and the subsequent seeded dispersion polymerization was found to be important. The final outcome of a seeded dispersion polymerization, that is, the morphology of the structured particles and the formation of secondary particles, was found to be primarily governed by thermodynamic factors. It was also found that the latex particles in these dispersion systems are virtually stabilized by the small amount of grafted PVP molecules. The dispersions maintain colloidal stability after repeated washing of the particles, which removes all of the soluble PVP. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 84: 2710–2720, 2002     

Dispersion polymerization of n‐butyl acrylate

The dispersion polymerization of n‐butyl acrylate (BA) was investigated using alcohol/water mixtures as the dispersion medium, 4,4′ ‐azobis‐(4‐cyanopentanoic acid) as the initiator, and polyvinylpyrrolidone (PVP) as the stabilizer. The effects of polymerization parameters, such as the alcohol/water ratio in the medium and the type and concentration of the polymeric stabilizer, on the resulting particle size and size distribution were studied. The final particle size and the stability of the dispersion system were found to be greatly influenced by the type of alcohol used in the mixture; that is, methanol or ethanol, even though the apparent solubility parameters are almost the same for the two types of mixtures. Poly(butyl acrylate) particles with controlled size and size distribution (monodisperse), and gel content were successfully prepared in a 90/10 methanol/water medium. It was found that the particle size decreased with increasing initiator concentration. This is the opposite of what was previously reported in the dispersion polymerizations of styrene and methyl methacrylate. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 84: 2692–2709, 2002     

表面处理方式对纳米SiO_2/PS复合粒子粒径及分布的影响

纳米SiO2粒子进行表面处理时所用表面活性剂的种类及用量直接影响二氧化硅/聚苯乙烯(SiO2/PS)复合粒子的粒径及分布。纳米SiO2粒子在超声波场作用下经十六烷基三甲基溴化胺(CTAB)处理后,可在纳米SiO2粒子表面形成单体和引发剂的富集区,在适当条件下引发以纳米SiO2粒子为核心的原位分散聚合反应。当纳米SiO2粒子对CTAB的吸附与初级粒子对聚乙烯吡咯烷酮(PVP)K-30的吸附达到动态平衡时,制备出的SiO2/PS复合粒子表面光滑,分散性好,仅有少量的游离纳米SiO2粒子存在,大部分纳米SiO2粒子被PS包裹。     

表面荷正电聚苯乙烯胶体颗粒界面电性质的研究

以偶氮二异丁脒盐酸盐V50(AIBA)为引发剂[1],水为分散介质,采用无皂乳液聚合法制备聚苯乙烯颗粒,制备出颗粒粒径为500 nm左右单分散性的聚苯乙烯颗粒。研究结果表明:在一定条件下用该方法制备的胶体颗粒zeta电位曲线均出现在平台pH2.0~6.0,说明在一定条件下聚苯乙烯胶体颗粒具有良好的稳定性。     

Effect of PVP in dispersion and seeded dispersion polymerizations

The outcome of seeded dispersion polymerizations of n‐butyl acrylate (BA) and styrene (St) in terms of the success of growing the seed particles without nucleating new particles or generating coagulum was found to be dependent on the seed type (poly[n‐butyl acrylate] [ PBA] or polystyrene [PSt]), the second‐stage monomer (BA or St), and the type of polyvinylpyrrolidone (PVP) stabilizer (PVP K30 or PVP K90). All seeds were first cleaned of excess stabilizer by medium replacement before the seeded polymerizations. In general, successful particle growth was achieved when the second‐stage polymerization employed PVP K30 (1 wt%) as the stabilizer. In contrast, nearly all reactions employing PVP K90 (1 wt%) as the second‐stage stabilizer resulted in the nucleation of a second crop of particles. These phenomena were further investigated by carrying out dispersion polymerizations using the supernatant obtained by separating the seeds from the second‐stage media (containing monomer). The results paralleled those in the seeding studies and were explained by the presence of small amounts of grafted PVP created in situ during the preparation of the seeds. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 84: 2721–2732, 2002     

Solvent effect on TEMPO-mediated living free radical dispersion polymerization of styrene

Living free radical dispersion polymerization of styrene in the presence of 2,2,6,6-tetramethylpiperidin-1-oxyl (TEMPO) and 2,2-azobisisobutyronitrile (AIBN) was conducted in various glycol media having different solubility parameters. Genuine heterogeneous polymerization nature was observed from the initial stage of the reaction. The solubility parameter of the media was found to significantly influence the living characteristics of the polymerization including the polymerization kinetics and the molecular weight evolution at a fixed concentration of TEMPO. A grafting of stabilizer molecules onto monomer and a possible partitioning of TEMPO between the continuous medium and particle phase were postulated for the deviation of the experimentally obtained molecular weight from the calculated value. For a poor medium for styrene, such as diethylene glycol, the living nature was achieved by increasing the amount of TEMPO. The polystyrene (PS) microsphere was well obtained in all tested glycol media and the average size was increased with enhanced affinity of the media to styrene and with decreasing concentration of TEMPO.     

Molecular miscibility and chain dynamics in POSS/polystyrene blends: Control of POSS preferential dispersion states

Polyhedral oligomeric silsesquioxane (POSS)/polystyrene nanocomposites with two different POSS molecules, octaisobutyl POSS (Oib-POSS) and trisilanolphenyl POSS (Tsp-POSS), were prepared via solution blending in toluene. Solution dynamics analysis indicates random coil conformation of neat PS and POSS/PS blends. Morphology analysis (AFM/TEM) revealed differences in the preferential dispersion states of Tsp- and Oib-POSS molecules. Tsp-POSS, with its greater predicted solubility in PS, exhibited nanoscale dispersion throughout the bulk leading to transparent films. In contrast, Oib-POSS, with its reduced predicted solubility in PS, exhibited preferential surface segregation, aggregation of POSS particles and hazy films. Estimated fractional surface coverage for the materials, based on surface energy measurements, indicated 15% coverage by Tsp-POSS and 78% for Oib-POSS. Solid-state NMR relaxation studies suggest aggregation of Oib-POSS molecules. Additional NMR studies, including silicon CP/MAS, 2D HETCOR, and WISE, indicate close spatial proximity and interaction of Tsp-POSS molecules with PS chains, contrasting with poor interaction and immiscibility of Oib-POSS with PS.