非溶剂诱导聚苯乙烯超薄膜去润湿过程中不同有序表面形貌的形成

利用原子力显微镜研究了带有自然氧化层硅基底上聚苯乙烯薄膜在不同非溶剂诱导下的去润湿过程.研究发现,非溶剂是通过渗透取代机理诱导高分子薄膜发生去润湿.薄膜的形貌取决于成孔过程与孔增长过程的相对速度.当聚苯乙烯(PS)薄膜厚度为15 nm时,随着溶剂烷基链的增长,成孔数显著降低;然而孔开始合并时孔径明显地增加.当PS薄膜厚度增加到25 nm时,随着溶剂烷基链的增长,成孔数略有降低,薄膜形貌形成长程有序的双连续的结构.当PS膜厚为35 nm时,与其它2个膜厚相比,成孔数大幅下降.此外,温度和分子量能进一步降低去润湿过程中的成孔数,从而形成分形结构形貌.     

浸泡法和旋涂法对偶氮聚电解质静电吸附自组装膜结构及性能的影响

利用浸泡和旋涂静电吸附自组装技术制备了含有偶氮生色团的聚电解质薄膜,比较了两种方法在自组装膜生长机理、膜结构以及膜光学性能方面的差异.利用紫外光谱和椭偏仪检测自组装膜的生长情况,利用原子力显微镜对膜表面结构进行了表征,并用偏振激光在膜表面进行了写光栅实验.结果表明,采用浸泡法和旋涂法都可以制备出表面光滑均匀的含偶氮生色团的聚电解质自组装膜.但是浸泡法自组装膜的生长速度要比旋涂法快.在自组装膜厚度较小的情况下,旋涂法得到的自组装膜可以写出明显的光栅而浸泡法不可以.随着自组装膜厚度的增加,两种方法得到的自组装膜都可以写出明显的光栅.这些结果说明浸泡法自组装膜内部聚电解质分子的层间穿插比较严重,而旋涂法自组装膜内分子穿插要弱得多.     

纤维素纳米晶体薄膜的制备与表征

讨论了两种新型纤维素纳米晶体(Cellulose nanocrystal,CNC)薄膜的制备方法:浸没法和旋涂法,并利用红外反射吸收光谱(Infrared reflection absorption spectroscopy,IRRAS)和原子力显微镜(Atomic force microscopy,AFM)对其进行表征。AFM高度图显示两种工艺制备的CNC薄膜均由棒状的CNC纳米颗粒交错叠加而成。实验结果显示,旋涂法制备的薄膜更加光滑,粗糙度RMS约为2.7 nm。由于带电颗粒间斥力的存在,浸没法制备的CNC膜厚度最大约为15 nm,而旋涂法可以得到更厚的CNC薄膜,其厚度可达50 nm以上。研究CNC悬浮液浓度与旋涂法CNC膜厚之间的关系后发现,可以通过改变CNC溶液的浓度对薄膜厚度进行控制。IRRAS结果也证实随着CNC悬浮液浓度的增加,旋涂薄膜的厚度随之增加。     

寡链聚苯乙烯纳米颗粒的制备及其凝聚态特征

用一种新的苯乙烯 乳化剂 引发剂体系 ,通过微乳液聚合得到了聚苯乙烯(PS)纳米粒子 (直径为 2 0～ 43nm) ,并用凝胶色谱、激光光散射、透射电子显微镜测量了PS的分子量、粒子的平均粒径和质量 ,由此计算每个PS粒子所包含的平均分子链数 (Np) .系统地考察了单体、乳化剂和引发剂浓度对分子量、粒径和Np 的影响 .以一种每个纳米粒子中平均含 4根分子链的寡链聚苯乙烯颗粒 ( 4CPS)为例 ,用调制型示差扫描量热计、Fourier红外光谱、荧光光谱、固体13 C 核磁共振分别研究了原始的 4CPS颗粒 ,以及经冷冻、玻璃化转变温度以上热处理及溶解浇铸成膜后样品的热行为、光谱和分子运动特征 .结果进一步表明 ,在原始的 4CPS中 ,链段间凝聚缠结较少 ,而经冷冻和热处理后 ,形成了更多的凝聚缠结 .     

旋涂法制备功能薄膜的研究进展

作为众多的薄膜制备方法之一,旋涂法具备薄膜厚度精确可控、高性价比、节能、低污染等优势,在微电子技术、纳米光子学、生物学、医学等领域中有着广阔的应用前景.本文简单介绍了旋涂法的模型、机理及其主要参数的估算方法,并总结了近几年来用旋涂法制备光学、微电子学等功能薄膜的新进展,最后对旋涂法的发展前景进行了展望.     

高分子量聚合物对溶剂诱导低分子量聚合物薄膜去润湿动力学的影响

采用偏光显微镜及椭偏仪等研究了单分散低分子量聚苯乙烯(PS)薄膜、 单分散高分子量PS薄膜以及将二者按不同质量比共混制备的PS薄膜, 在室温下用丙酮溶剂诱导其去润湿的过程. 实验发现, 按不同质量比共混的PS薄膜的去润湿动力学与单分散的PS薄膜去润湿动力学有较大区别. 按不同质量比共混的PS薄膜, 低分子量的PS更易于富集在薄膜的表面, 其去润湿的速度介于单分散低分子量PS薄膜与单分散高分子量PS薄膜的去润湿速度之间. 但共混薄膜的去润湿速率并非随着高分子量PS的加入呈现单调的变化, 这是由大量接触分子的形成抑制了去润湿所致.     

TiO2/十六烷基三甲基溴化铵有序交替层状纳米复合薄膜的制备与结构表征

近年来有序交替的层状纳米结构薄膜的制备吸引了研究者们的极大关注. 目前, 这类薄膜的制备方法研究得最多的是LB技术[1～3]、基于化学吸附的自组装成膜技术[4,5]和交替沉积组装技术[6～8]. 但这几种方法都有明显的缺陷[9,10], 其中,通过LB技术制备有序交替层状纳米复合薄膜需要昂贵的仪器, 而且由于层间是分子相互作用, 膜的稳定性较差; 基于化学吸附的自组装成膜技术由于需要高反应活性的分子和特殊的基底表面, 并且由于化学反应的产率很难达到100%, 因此通过这种方法制备结构有序的多层膜并不容易; 利用交替沉积的方法制备出具有实用厚度的纳米多层膜需要耗费大量的时间. 最近, 出现了一种称为蒸发诱导的超分子自组装方法, 由这种方法制备的纳米多层膜具有成膜速度快和膜有序度高等优点, 此外还可以通过改变成膜物质浓度和拉膜速度来控制薄膜的厚度, 但与LB膜相比其厚度无法在分子水平上控制. 利用这种方法制备多层膜目前的文献报道仅限于线形SiO2与有机物的组装[10～13]. 本文利用这种方法制备了TiO2/十六烷基三甲基溴化铵纳米复合薄膜并对其结构进行了表征, 结果表明所制备的薄膜具有TiO2/十六烷基三甲基溴化铵有序交替的层状结构.     

核/壳纳米复合粒子填充聚苯乙烯的流变行为

采用细乳液聚合制备了以偶联剂改性纳米二氧化硅粒子(SiO2)为核、交联聚苯乙烯(PS)为壳的SiO2@PS复合纳米粒子(SCCSN).采用透射电子显微镜(TEM)、动态光散射(DIS)法考察了SCCSN的粒子形貌特征,发现SCCSN呈球形,粒径约90 nm,均匀分散;采用热失重(TG)、调制式差示扫描量热(MDSC)与动态力学分析(DMA)研究了SCCSN的结构特征,发现PS包覆率随交联剂含量增加而升高,且玻璃化转变温度(Tg)显著升高.交联壳层不仅能够将聚合物锚固在SiO2表面,屏蔽SiO2粒子与基体PS间相互作用,而且阻止PS壳层与基体PS分子链间的缠结.MDSC结果显示,SiO2与SCCSN填充可降低复合物Tg.动态流变结果表明,填充PS熔体非线性流变行为与PS分子链解缠结有关,SiO2与SCCSN均不影响填充熔体非线性流变机理.SCCSN的SiO2核对PS的增强效应略优于SiO2,且增强效应与壳层交联度有关.     

利用Breath Figure法制备具有Honeycomb结构的有机/无机复合膜

以聚苯乙烯和正硅酸乙酯的有机溶液为铸膜溶液, 利用Breath Figure法制备了PS/SiO2Honeycomb结构复合膜. 采用SEM对复合膜进行了形貌分析, 探讨了聚合物浓度、 PS/TEOS配比、聚合物的结构、溶剂等对膜Honeycomb结构的影响. 研究结果表明, 聚合物浓度在20～50 mg/mL, PS/TEOS质量比大于2∶1的条件下可以制备结构完整的多孔膜, 且制备的Honeycomb结构在0.8 cm2内无缺陷; 采用双羧基封端的聚苯乙烯成膜效果好于单羧基封端的成膜效果; 以氯仿和苯作为溶剂均可以制备完全Honeycomb结构的复合膜, 但以苯为溶剂制备的多孔膜孔径较大. 成膜中TEOS水解不完全, 复合膜中混杂着未完全水解的TEOS以及SiO2. EDS面扫描分析表明, Si和O均匀地分散在复合膜中.     

TiO2-SiO2二维大孔薄膜的制备及其光催化活性研究

本文采用改进的溶胶-凝胶法制备了具有锐钛矿晶型结构和较小晶粒尺寸的TiO₂-SiO₂溶胶,并以聚苯乙烯(PS)小球为模板,采用旋涂法制备了新型大孔TiO₂-SiO₂复合薄膜,探究了煅烧温度、不同硅钛比以及溶胶添加量对所制备的大孔薄膜形貌及光催化活性的影响,并考察了该薄膜真空活化前后(Ti³⁺掺杂后)在紫外及模拟太阳光下光催化降解有机污染物罗丹明B的活性。通过Raman、DRS、SEM、EPR等方法对薄膜进行表征,发现制备的复合薄膜具有高透明度、良好附着力及优异的光催化活性。     

基底界面效应对聚苯乙烯薄膜分子运动行为的影响

本文研究了Si／Si02、Si／Si—H基底与聚苯乙烯（Ps）之间的界面相互作用对Ps薄膜的玻璃化转变及相关力学性能的影响．结果显示,无论何种基底,Ps薄膜的玻璃化转变温度（L）都随其厚度降低而降低．但相同厚度（〈110nm）下,以Si／Si-H为基底时Ps薄膜的瓦比以Si／Si02为基底的PS薄膜高．Si／Si02表面Ps薄膜疋开始下降的临界厚度为110nm,远高于以Si／Si—H为基底时的40nm．对Ps薄膜的膨胀系数和弹性模量进行研究,也得到相似的临界厚度．另外,与Si／Si02基底相比,在Si／Si-H上的Ps薄膜具有更低的膨胀系数以及较高弹性模量．可能原因是Si／Si-H与Ps具有较强的相互作用,限制了该界面分子的运动能力,导致基底／PS界面效应对薄膜分子运动的影响力增强,造成该薄膜瓦的厚度依赖性下降,并呈现出相对较硬的力学特征．     

Viscoelastic dewetting of constrained polymer thin films

Thin films of fluids are playing a leading role in countless natural and industrial processes. Here we study the stability and dewetting dynamics of viscoelastic polymer thin films. The dewetting of polystyrene close to the glass transition reveals unexpected features: asymmetric rims collecting the dewetted liquid and logarithmic growth laws that we explain by considering the nonlinear velocity dependence of friction at the fluid/solid interface and by evoking residual stresses within the film. Systematically varying the time so that films were stored below the glass-transition temperature, we studied simultaneously the probability for film rupture and the dewetting dynamics at early stages. Both approaches proved independently the significance of residual stresses arising from the fast solvent evaporation associated with the spin-coating process. © 2006 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 44: 3022–3030, 2006     

Relaxing nonequilibrated polymers in thin films at temperatures slightly above the glass transition

We have studied the dewetting process of thin polystyrene films on nonwettable substrates in the viscoelastic regime slightly above the glass transition temperature. The evolution of the shape of the dewetting rim for varying film thickness, molecular weights and dewetting temperatures allowed us to determine the relaxation rates of residual stresses, which originated from nonequilibrated polymer chain conformations formed during film preparation by spin‐coating. For long chain polymers, we found rates notably faster than the longest bulk relaxation processes, highly independent of molecular weight and temperature. Our study demonstrates that dewetting is a powerful tool for sensitive characterization of nonequilibrium properties of thin polymer films. © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2017 , 55, 515–523     

Size effects on miscibility and glass transition temperature of binary polymer blend films

After determining the size dependent miscibility of binary polymer blend films using molecular dynamics simulation and thermodynamics, the size dependent glass transition temperatures Tg(w,D) of several polymer blend films in miscible ranges are determined by computer simulation and the Fox equation where w is the weight fraction of the second component and D denotes thickness of films. The Tg(w,D) function of a thin film can decrease or increase as D decreases depending on their surface or interface states. The computer simulation results are consistent with available experimental results and theoretical results for polymer blend films of PPO/PS [poly(2,6-dimethyl-1,4-phenylene oxide)/polystyrene] and stereoregular PMMA/PEO [poly(methyl methacrylate)/poly(ethylene oxide)]. The physical background of the above results is related to the root of mean square displacement of thin films in their different regions.     

Direct measurement of molecular motion in freestanding polystyrene thin films

An optical photobleaching technique has been used to measure the reorientation of dilute probes in freestanding polystyrene films as thin as 14 nm. Temperature-ramping and isothermal anisotropy measurements reveal the existence of two subsets of probe molecules with different dynamics. While the slow subset shows bulk-like dynamics, the more mobile subset reorients within a few hundred seconds even at T(g,DSC) - 25 K (T(g,DSC) is the glass transition temperature of bulk polystyrene). At T(g,DSC) - 5 K, the mobility of these two subsets differs by 4 orders of magnitude. These data are interpreted as indicating the presence of a high-mobility layer at the film surface whose thickness is independent of polymer molecular weight and total film thickness. The thickness of the mobile surface layer increases with temperature and equals 7 nm at T(g,DSC).     

Difference in Glass Transition Behavior Between Semi Crystalline and Amorphous poly(lactic acid) Thin Films

Summary: Semi crystalline and amorphous poly(lactic acid) (PLA) thin films exhibit different glass transition temperature and behaviour, as revealed by ellipsometry. For semi-crystalline poly(L-lactic acid) (PLLA) thin film (with crystalline content between 40 and 60%), the glass transition temperature (T_g) is found to decrease below a film thickness of 50 nm. This depression was interpreted in term of disentenglement effect which is likely to occur upon confining the amorphous PLA phase near a non interacting surface. New results performed on non completed films, i.e. isolated objects, also reveal the lower transition temperature, thus underlying the importance of the entanglement state of the polymer chains on their mobility. For amorphous PLA thin film, obtained from the L and D copolymer, two distinct glass transitions were observed, with the highest Tg attributed to the presence of some nano-phase domains, formed by a possible cooperation of the D and L blocks to form stereocomplexes sequences, within the film. Furthermore, if these T_g remained constant as film thicknesses decrease down to 50 nm, they were also found to slightly decrease for isolated objects, thus supporting the importance of the entanglement hypothesis on the glass transition.     

Instabilities during the formation of electroactive polymer thin films

The solvent-induced film structure of poly(n-vinyl carbazole) (PVK) thin films on indium tin oxide (ITO)-coated glass was examined. PVK thin films were prepared via spin-coating using five different solvents. We investigated the relationship between the solvent characteristics and film properties, including surface roughness and structure, film thickness, and density. The spin-coated polymer thin films are not in thermodynamic equilibrium; rather, the film properties are affected by the dynamics of the spin-coating process. We found that water present in tetrahydrofuran (THF) induces dewetting of PVK films during the spin-coating process. Solvents with a high evaporation rate lead to high surface roughness due to Marangoni convection. The results show that the surface roughness and structure of the films are dominated by the dynamics of the film formation process, rather than thermodynamic interactions between the polymer and solvents.     

Specific heat and dielectric relaxations in ultra-thin polystyrene layers

The effect of thickness on the glass transition dynamics in ultra-thin polystyrene (PS) films (4 nm < L < 60 nm) was studied by thin film ac-calorimetry, dielectric spectroscopy (DRS) and capacitive dilatometry (CD). In all PS-films, a prominent α-process was found in both the ac-calorimetric and dielectric response, indicating the existence of cooperative bulk dynamics even in films as thin as 4 nm. Glass transition temperatures (T_g) were obtained from ac-calorimetric data at 40 Hz and from capacitive dilatometry, and reveal a surprising, marginal thickness dependence T_g(L). These results, which confirm recent data by Efremov et al. [Phys. Rev. Lett. 91 (2003)] but oppose many previous observations, is rationalized by differences in film annealing conditions together with the fact that our techniques probe exclusively cooperative dynamics (ac-calorimetry) or allow the effective separation of surface and “bulk”-type mobility (CD). Two other observations, a significant reduction in c_p towards lower film thickness and the decrease in the contrast of the dilatometric glass transition, support the idea of a layer-like mobility profile consisting of both cooperative “bulk” dynamics and non-cooperative surface mobility.     

聚3-羟基丁酸酯薄膜结晶的ATR-FTIR研究

使用匀胶机(spincoater),通过溶液铸膜的方法,在铝箔基板上制备出具有不同厚度的聚3羟基丁酸酯(PHB)薄膜.20℃室温条件下,通过衰减全反射傅立叶红外光谱(ATRFTIR)原位观测了不同厚度薄膜的结晶过程,并通过偏光ATRFTIR对薄膜中PHB分子的取向进行了研究.ATRFTIR原位观测结果显示,PHB在薄膜中的结晶速率以及结晶度均随着薄膜厚度的减小而逐渐降低;同时,偏光ATRFTIR测试结果表明,随膜厚减小,薄膜中结晶部分的PHB分子逐渐倾向于沿垂直于基板表面方向取向,膜越薄,倾向越明显.可以认为,PHB分子与基板间的相互作用以及扩散控制结晶导致了上述现象的产生.     

AFM characterization of spin-coated multilayered dry lipid films prepared from aqueous vesicle suspensions

We present a detailed AFM study on multilayered dry lipid films prepared from aqueous vesicle suspensions. Different preparation techniques were applied in order to optimize the preparation of homogeneous lipid films of various film thicknesses. Suspensions of preformed DOPC/DPPC vesicles were adsorbed onto indium tin oxide-coated glass coverslips, a substrate also commonly employed for the formation of giant liposomes. We found that the homogeneity of the lipid films could substantially be improved when applying a spin-coating step during the film preparation. These films were much more homogeneous than those prepared by conventional drop-casting and in addition the film thickness could be controlled. When using a combination of vesicle adsorption and spin-coating the quality and thickness of the films depended crucially on the lipid concentration of the vesicle suspension, the adsorption temperature and the adsorption time. For lipid films prepared by direct spin-coating the lipid concentration and the applied spin-coating sequence were critical parameters for the quality and thickness of the deposited lipid films.