PS-b-PMMA-b-PBMA薄膜自组装形貌研究

采用原子转移自由基聚合技术制备了聚苯乙烯-b-聚甲基丙烯酸甲酯-b-聚甲基丙烯酸丁酯三嵌段共聚物。利用原子力显微镜考察了该三嵌段共聚物薄膜相结构在不同溶剂气氛中随时间的演变。结果表明:在聚苯乙烯的选择性溶剂二甲苯(甲苯)气氛中,共聚物微相结构实现了由球状结构到棒状结构的转变,并最终形成较为有序的条纹形貌。在共溶剂四氢呋喃(氯仿)气氛中,微相结构由与基底平行的层状结构演变为棒状结构。另外,通过热溶剂蒸汽退火,制备了特征尺寸为28nm、长程有序的条纹形貌。     

PEO-b-PS嵌段共聚物的合成与有序纳米膜的制备

以聚环氧乙烷-溴(PEO-Br)大分子引发剂引发苯乙烯(St)的原子转移自由基聚合(ATRP),制备了聚环氧乙烷-b-聚苯乙烯(PEO-b-PS).1H NMR分析表明嵌段共聚物中聚环氧乙烷嵌段和聚苯乙烯嵌段的数均分子量分别是5500和37000,PEO的质量分数为12.9％.考察了旋涂环境和溶剂熏蒸后处理方法对此嵌段共聚物薄膜形貌的影响,结果表明在PS的良溶剂和PEO的良溶剂共同存在下旋涂成膜,并经过两种良溶剂共同蒸汽的后处理,PEO-b-PS嵌段共聚物可以制得具有规则纳米圆柱图案的薄膜.     

聚丙烯酸对含聚氧化乙烯链段嵌段共聚物微相分离形貌的调控作用

采用原子转移自由基聚合(ATRP)制备了两嵌段共聚物聚氧化乙烯-b-聚苯乙烯(PEO-b-PS)和三嵌段共聚物聚氧化乙烯-b-聚苯乙烯-b-聚丙烯酸丁酯(PEO-b-PS-b-PBA),再将聚丙烯酸(PAA)分别与PEO-b-PS和PEO-b-PS-b-PBA进行溶液共混和旋涂成膜,通过原子力显微镜研究了PAA对2种嵌段共聚物薄膜微相分离形貌的调控作用。结果表明,PEO-b-PS/PAA共混薄膜呈现PEO/PAA为分散相以柱状形态垂直分布在PS连续相中的微相分离形貌,柱状微区尺寸随着PAA含量及相对分子质量的增加而不断增大。当PAA质量分数达到30%后,PEO/PAA分散相向层状形态转变。PEO-b-PS-b-PBA与PAA共混后,PEO/PAA相区从原先平行于薄膜表面排列的层状形态向随机取向的柱状形态转变,PS微相区在薄膜表面形成细小的锥状突起,随着PAA质量分数增加,PEO/PAA柱状微区向薄膜表面垂直排列取向得到增强,PS微相区的突起程度降低。     

嵌段共聚物PS-b-PMMA在PCHMA/PMMA共混体系中增容效果的研究:嵌段比、分子量及粘度的影响

采用熔融共混方式,利用两嵌段共聚物聚苯乙烯-b-聚甲基丙烯酸甲酯(PS-b-PMMA)来增容聚甲基丙烯酸环己酯(PCHMA)/聚甲基丙烯酸甲酯(PMMA)共混体系,主要研究PS-b-PMMA嵌段比、均聚物的分子量以及体系粘度对增容效果的影响。研究发现,非对称结构的嵌段共聚物较对称结构的嵌段共聚物更容易在体相形成胶束,胶束的形成减少了嵌段共聚物在界面的利用率。均聚物分子量增大,嵌段共聚物的胶束均增加。分散相分子量增大,造成了界面的嵌段共聚物稳定性减弱,容易扩散至分散相内部,形成胶束。连续相分子量增大致使链段溶胀力减小,嵌段共聚物胶束外围的乳化效果降低,而且连续相粘度增大,使得嵌段共聚物胶束滞留在连续相,难以迁移至界面。共混体系的混合剪切增加,粘度变小,嵌段共聚物的扩散速率加快。通过调控均聚物分子量和体系粘度,能有效地减少体相胶束的形成,增大嵌段共聚物在界面的利用率。通过Leibler干湿刷理论、焓驱溶胀聚合物刷以及Stokes-Einstein扩散理论可以解释相关的结论。     

用于组装纳米粒子密集排列点阵的嵌段聚合物自组织图案模板的可控制备

利用溶剂引导的无序-有序相转变的方法制备了形貌可控的自组织嵌段聚合物薄膜,并对影响形貌的条件进行了讨论.通过控制一系列由大变小的溶剂蒸发速率,获得了形貌依次为无序多孔、有序多孔、有序多孔和面内柱状混合结构、及面内柱状等一组自组织图案,并以之为模板引导气相沉积团簇自组装,制备了"密集排列"的纳米粒子有序点阵.     

两亲嵌段共聚物PS-b-PAA自组装薄膜的表面形貌与结晶性能研究

采用溶液浸渍-提拉法制备了两亲性嵌段共聚物PS-b-PAA自组装薄膜,并利用图像分析仪和X射线衍射仪研究了聚合物薄膜的表面形貌和结晶性能.研究结果表明,PS-b-PAA的溶液浓度和嵌段长度通过影响溶液中形成的反胶束数目和粒径进而造成溶剂挥发过程中反胶柬在扩散动力学上的差异,最终得到不同形貌的嵌段共聚物薄膜.结晶性能研究结果表明,室温下PS-b-PAA在玻璃基板表面的结晶是一种受膜厚影响、动力学控制的受限结晶过程.当溶液浓度达到0.1g/mL时,可制备出致密的结晶性嵌段共聚物薄膜.     

PCL-b-PMMA/PEO共混薄膜的微相分离形貌

通过聚氧化乙烯(PEO)与聚己内酯-聚甲基丙烯酸甲酯嵌段共聚物(PCL-b-PMMA)的共混来调节聚己内酯(PCL)与聚甲基丙烯酸甲酯(PMMA)嵌段的微相分离行为。采用原子力显微镜研究了PEO的质量分数和相对分子质量对PCL-b-PMMA/PEO共混薄膜微相分离形貌的影响。结果表明,共混薄膜形成了以PMMA/PEO为连续相,PCL呈柱状微区垂直于薄膜表面的微相分离形貌,PMMA/PEO链段无法在PCL柱状微区上方形成完全覆盖,导致薄膜表面形成许多孔洞。随着PEO含量增加,PCL链段聚集趋势增强,柱状微区尺寸不断增大;随着PEO相对分子质量的增加,PMMA/PEO在PCL微区上方形成的有效覆盖减少,薄膜表面的孔洞数量和尺寸增大;当PEO与不同嵌段比PCL-b-PMMA共混后,随嵌段共聚物中PCL链段体积分数增加,柱状微区向层状形态转变,薄膜表面孔洞消失。     

嵌段共聚物PEO-b-PS与聚苯乙烯共混薄膜的表面形貌及性能

通过原子转移自由基聚合(ATRP)制备了嵌段共聚物聚氧化乙烯(PEO-b-聚苯乙烯(PS)),将PEO-b-PS与PS溶液共混成膜,使用接触角测试仪(CA)和原子力显微镜(AFM)考察了PEO-b-PS含量与共混薄膜表面形貌及性能之间的关系。研究发现,嵌段共聚物在薄膜中发生微相分离并在薄膜表面形成PEO微相区,随PEO-b-PS含量增加,薄膜表面PEO相区尺寸增大,但分布密度下降。通过共混薄膜表面形貌的变化,解释了共混薄膜的亲水性和表面张力随PEO-b-PS含量增加的变化趋势。     

不同共混方式下非对称嵌段共聚物PS-b-PMMA对PCHMA/PMMA体系增容效果的研究:界面与胶束的竞争

采用熔融共混方式,利用非对称两嵌段共聚物聚苯乙烯-b-聚甲基丙烯酸甲酯(PS-b-PMMA)对聚甲基丙烯酸环己酯(PCHMA)/聚甲基丙烯酸甲酯(PMMA)共混体系进行增容。重点研究了嵌段比、共混方式以及分散相PMMA分子量对共混体系中非对称嵌段共聚物分布的影响,即嵌段共聚物稳定相界面与所形成胶束数量、位置之间的竞争关系。结果表明,在低分子量PMMA情况下共混方式对非对称嵌段共聚物的分布影响显著,改变共混方式可以有效减少分散相中的胶束数量,使嵌段共聚物主要分布在二元不相容增容体系两相界面。另一方面,增大PMMA分子量会改变非对称嵌段共聚物在两相界面的界面曲率,导致其在分散相中的溶解性增大,在界面上的稳定性减小,从而迁移至分散相内部并最终形成胶束。     

PS-b-PNIPAAm嵌段共聚物多孔薄膜的制备及形貌研究

将两亲性PS-b-PNIPAAm嵌段共聚物(BCP)溶解在四氢呋喃中配制成浓度为2%(质量分数)的溶液,旋涂后得到初生嵌段共聚物薄膜,以乙醇为退火溶剂退火后,探讨了退火时间对薄膜微孔结构的影响,结果表明,随着退火时间的延长,膜表面的微相分离越明显,微孔结构的分布更均匀。进一步将在乙醇中退火预处理的薄膜分别在乙醇或去离子水中进行溶胀处理,通过选择性溶胀成孔法制备PS-bPNIPAAm纳米多孔膜。研究了溶胀时间、温度及溶剂类型对薄膜形貌的影响,结果发现升高溶胀温度和延长溶胀时间均有助于膜表面微孔结构的形成,且该过程中乙醇的成孔作用比水的作用更为明显。     

超临界二氧化碳中N-异丙基丙烯酰胺与二乙二醇二甲基丙烯酸酯的交联聚合

采用超临界二氧化碳（scCO2）沉淀聚合法,在不添加高分子表面活性剂及共溶剂的前提下,以AIBN为引发剂,二乙二醇二甲基丙烯酸酯为交联剂,成功制备了交联的聚（N-异丙基丙烯酰胺）温度敏感型微凝胶;通过扫描电镜（SEM）、差示扫描量热分析（DSC）等方法对聚合物的微观形貌进行了表征,测定了微凝胶的相转变温度,同时也考察了...     

Effects of block copolymer self-assembly on optical anisotropy in azobenzene-containing PS-b-PMMA films

Polystyrene-b-polymethylmethacrylate (PS-b-PMMA) was selected as the host for 4-(4-nitrophenylazo)aniline (Disperse Orange 3, DO3) based on a previous study of DO3/PMMA and DO3/PS binary blends. Selective location of DO3 into the PMMA block of the copolymer was expected during self-assembly of the block copolymer since a preferential interaction of DO3 with PMMA has been demonstrated. However, surface segregation of DO3 was found during the thermal annealing used to nanostructure the copolymer. To avoid this, a thermoplastic polymer (Azo-TP) was synthesized from the bulk reaction of DO3 and diglycidyl ether of bisphenol A (DGEBA). The choice of DGEBA as a co-reactant was an attempt to encourage the selective location of azo groups in the PMMA phase of PS-b-PMMA. An inspection of solutions of Azo-TP in PS and PMMA, corroborates the preferential affinity of Azo-TP for PMMA. The Azo-TP could be satisfactorily dissolved in PS-b-PMMA. We have investigated the growth and decay processes of the optically induced birefringence in films of PS-b-PMMA containing 12?wt% Azo-TP. The resulting materials showed a good photoinduced time response, high maximum birefringence and an elevated fraction of remnant anisotropy.     

聚4-乙烯基吡啶微凝胶的绿色合成

以4-乙烯基吡啶为单体,N,N’-亚甲基双丙烯酰胺为交联剂,在超临界二氧化碳(scCO2)中,通过沉淀聚合方法制备了交联聚(4-乙烯基吡啶)的干燥粉末。考察了反应体系的引发剂浓度、交联剂浓度、反应压力、反应时间等因素对聚合反应的影响。通过红外光谱(FT-IR)和扫描电镜(SEM)对聚合物组成及形貌进行了表征。实验表明,反应压力为14MPa,温度为70℃时,在适当交联剂用量下,可获得粒径约为0.5μm-1μm的干燥粉末,所得聚合物的产率大于90%。     

超临界CO2环境中聚丙烯固相接枝甲基丙烯酸缩水甘油酯

对超临界CO2环境中聚丙烯固相接枝甲基丙烯酸缩水甘油酯反应过程进行了研究。考察了反应时间、CO2的压力、单体用量、引发剂用量以及反应温度对接枝产物接枝率和凝胶率的影响,获得了较优的接枝反应条件。结果表明,与熔融接枝和传统固相接枝过程相比,采用超临界固相接枝过程制得的接枝物具有接枝率高、凝胶率低且降解程度低等优点。同时接枝产物的接枝率和凝胶率除了可通过改变单体用量和引发剂用量进行调节外,还可通过改变CO2的压力进行调节。     

Growing TiO2 nanowires on the surface of graphene sheets in supercritical CO2: characterization and photoefficiency

Tremendous interest exists towards synthesizing nanoassemblies for dye-sensitized solar cells (DSSCs) using earth-abundant and -friendly materials with green synthetic approaches. In this work, high surface area TiO(2) nanowire arrays were grown on the surface of functionalized graphene sheets (FGSs) containing -COOH functionalities acting as a template by using a sol-gel method in the green solvent, supercritical carbon dioxide (scCO(2)). The effect of scCO(2) pressure (1500, 3000 and 5000 psi), temperature (40, 60 and 80 °C), acetic acid/titanium isopropoxide monomer ratios (HAc/TIP = 2, 4 and 6), functionalized graphene sheets (FGSs)/TIP weight ratios (1:20, 1:40 and 1:60 w/w) and solvents (EtOH, hexane) were investigated. Increasing the HAc/TIPweight ratio from 4 to 6 in scCO(2) resulted in increasing the TiO(2) nanowire diameter from 10 to 40 nm. Raman and high resolution XPS showed the interaction of TiO(2) with the -COOH groups on the surface of the graphene sheets, indicating that graphene acted as a template for polycondensation growth. UV-vis diffuse reflectance and photoluminescence spectroscopy showed a reduction in titania's bandgap and also a significant reduction in electron-hole recombination compared to bare TiO(2) nanowires. Photocurrent measurements showed that the TiO(2)nanowire/graphene composites prepared in scCO(2) gave a 5× enhancement in photoefficiency compared to bare TiO(2) nanowires.     

Chemical fluid deposition of monometallic and bimetallic nanoparticles on ordered mesoporous silica as hydrogenation catalysts

A simple and green method of depositing monometallic (Ru, Rh, Pd) and bimetallic nanoparticles (Ru-Rh, Ru-Pd and Rh-Pd) on an ordered mesoporous silica support (MCM-41) in supercritical carbon dioxide (scCO2) is described. Metal acetylacetonates were used in the experiments as CO2-soluble metal precursors. Suitable temperature and pressure conditions for synthesizing each kind of nanoparticles were applied in this study. The characterizations of these nanocomposites were performed by transmission electron microscopy (TEM), X-ray diffraction (XRD) and energy dispersive X-ray spectroscopy (EDS). The nanoparticles had average sizes varying from 2 nm to 8 nm. The Ru nanoparticles were clearly shown to be inside the mesopores of MCM-41 from the TEM image. These nanocomposites used as catalysts for hydrogenation was demonstrated. The efficiency of the scCO2 prepared Ru/MCM-41 catalyst was nearly 8 times than that of a Ru/MCM-41 catalyst prepared by conventional impregnation method.     

High-pressure total internal reflection fluorescence apparatus

Important interfacial processes in disciplines ranging from medicine to the separations sciences occur over a wide range of pressures, temperatures, and time scales. In this paper we report a new high-pressure total internal reflection fluorescence (HP-TIRF) apparatus that allows rapid fluorescence measurements of sub-monolayers in contact with liquids and supercritical fluids between 293 K and 353 K and up to 250 bar with picosecond time resolution. We use the HP-TIRF system to study the in-plane rotational reorientation dynamics of the fluorescent probe BODIPY 494/503 (C(2v) symmetry) covalently attached to silica surfaces that have been silanized with n-propyltrimethoxysilane (C(3)-TMOS) or 3,3,3-trifluoropropyltrimethoxysilane (CF(3)-TMOS) when the interface is subjected to pure supercritical carbon dioxide (scCO(2)). The in-plane BODIPY 494/503 rotational reorientation dynamics are assessed by using the Debye-Stokes-Einstein expression. As the scCO(2) density increases the local microviscosity surrounding the tethered BODIPY 494/503 molecule decreases. The terminal group (CH(3) versus CF(3)) within the silane monolayer governs the onset and absolute magnitude of the observed viscosity changes. The results are explained in terms of the wellknown solubility of fluorine-containing species in scCO(2).     

2DCOR-GC: an application of the generalized two-dimensional correlation analysis as a route to optimization of continuous flow supercritical fluid reactions

A new approach for optimization and monitoring of continuous reactions has been developed using 2D correlation methods for the analysis of GC data (2DCOR-GC). 2DCOR-GC maps are obtained following perturbation of the system that allow the effect of changing reaction parameters such as time, temperature, pressure, or concentration to be both monitored and sequenced with regard to changes in the raw GC data. In this paper, we describe the application of the 2DCOR-GC technique to monitoring the reverse water-gas shift reaction in scCO(2). 2DCOR-GC is combined with FT-IR data to validate the methodology. We also report the application of 2DCOR-GC to probe the mechanism of the alkylation of m-cresol with isopropyl alcohol in scCO(2) using Nafion SAC-13 as the catalyst. These results identify coeluting peaks that could easily be missed without exhaustive method development.     

Determination of gallium in human urine by supercritical carbon dioxide extraction and graphite furnace atomic absorption spectrometry

This study presents supercritical carbon dioxide (scCO(2)) extraction as an inherently safer and cleaner sample treatment method for identifying trace gallium in urine samples. Extraction is performed in the presence of a fluorinated beta-diketones chelating agent, 2,2-dimethyl-6,6,7,7,8,8,8-heptafluoro-3,5-octanedione (HFOD), by unmodified scCO(2). Quantitative extractions are conducted at 80 degrees C and 20.7 MPa with 15 min static plus 15 min dynamic extractions, and are followed by analysis via graphite furnace atomic absorption spectroscopy (GFAAS). The proposed procedure is successfully applied to determine the concentrations of gallium in real urine samples spiked with various levels of gallium with satisfactory recoveries of 90.8-100.3% (n=6) and relative standard deviations <10%. A standard reference material (SRM), Seronorm Trace Elements Urine, is used to validate the accuracy of the proposed method.