受限于两平行板间的对称星形共聚物Am Bm熔体相行为的格子自洽场理论研究

采用格子自洽场理论计算研究了受限于2个平行板间的对称星形共聚物AmBm(m=1,2,3,4,5)熔体形成的层状相结构.在给定的相互作用下(χNAB不变,χ为Flory-Huggins相互作用参数,NAB=(N?1)/m为单个聚合物分子中一对AB臂的总链节数目),针对平行板间距为体相周期的情况,系统考察了共聚物链长N和单个聚合物分子中A(或B)臂数目m对受限层结构细节及层取向的影响.由计算结果,当N或NAB不变时,受限层的归一化界面宽度随m的增大而减小.受限板为中性时,垂直层结构的单链自由能比平行层结构的低.随着板对共聚物中一种嵌段的选择作用Λ的增大,体系发生垂直层到平行层的转变,该转变为一阶相变.当m不变时,N越小,上述转变出现在越大的Λ值处,体系越容易保持垂直层结构.并且N越小,层状结构周期越小.当N或NAB不变时,m越大体系越容易保持垂直层结构.总之,星形共聚物的链长越短、臂数越多时,垂直层稳定的Λ区间越大、层状结构的界面宽度越小.这些结论可以指导刻蚀应用中对体系参数的选择.     

在平行板受限条件下AB两嵌段共聚物/纳米粒子复合物自组装行为的Monte Carlo模拟

采用Monte Carlo模拟方法研究了在平行板受限条件下A_(15)B_5非对称两嵌段共聚物与纳米粒子复合物的自组装行为,其中平行板对多组分嵌段A具有吸引相互作用.模拟结果表明,纳米粒子在两嵌段共聚物/纳米粒子复合物中的体积分数、嵌段共聚物不同嵌段与纳米粒子间的相互作用均对体系在平行板受限条件下的形貌结构及纳米粒子在体系中的分布有重要影响.当平行板间距一定时,未添加纳米粒子的A_(15)B_5非对称两嵌段共聚物中的A嵌段被吸附在平行板上形成层状相,而B嵌段则在平行板中形成六角堆积穿孔层状结构.加入与A嵌段不相容而与B嵌段相容的纳米粒子后,增加了纳米粒子与B嵌段的相容性,有利于保持B嵌段所形成的穿孔结构及孔洞尺寸,同时纳米粒子能够均匀地分散在B相区中.当引入的纳米粒子与A和B两嵌段均不相容时,降低纳米粒子与嵌段共聚物的不相容性同样有利于维持体系的穿孔结构.当纳米粒子与AB两嵌段共聚物间的排斥作用微弱时,即使含量较高,纳米粒子也不聚集,并且均匀分布在A相区与B相区的交界处.     

2H NMR研究嵌段共聚物溶致液晶相的结构演化与水分子动力学行为

采用2H NMR实验结合谱图线型的理论模拟方法研究了两亲性嵌段共聚物聚氧乙烯一聚氧丙烯一聚氧乙烯／氘代水／对二甲苯三元体系形成的不同液晶相的结构演化和水分子动力学行为．结果表明,对不同组分浓度的样品,2H谱线型发生明显的变化,对应体系从各向同性相、六角相和层状相间的系列结构转变．通过NMR弛豫模型获得了液晶相结构演化中序参数和分子运动相关时间的变化规律,理论模拟获得的自旋．晶格弛豫时间T1、自旋-自旋弛豫时乃等水分子动力学参数与实验测量结果吻合．结果表明：层状相四极劈裂及序参数随嵌段共聚物或二甲苯含量的增加呈现一个极大值,水分子的兀随着嵌段共聚物浓度增加而明显减小,而疋在六角相到层状相的转变中发生了明显的变化．研究表明,通过理论模拟2HNMR实验获得的谱图线型是研究液晶相结构演化和动力学的有力工具．     

环形对称两嵌段共聚物在薄膜中自组装行为的计算机模拟

采用Monte Carlo模拟方法考察了AB环形对称两嵌段共聚物受限在薄膜中的自组装行为。模拟结果表明,AB环形对称两嵌段共聚物在薄膜中自组装形成的层状结构的取向依赖于薄膜表面的选择性或膜厚。当薄膜表面无选择性或具有强选择性时,体系中层状结构的取向分别为垂直和平行于薄膜表面;当薄膜表面选择性较弱时,随着膜厚的增加层状结构的取向会发生由垂直向平行于薄膜表面的转变。这些模拟结果与文献报道中线形体系十分一致。然而值得注意的是,当薄膜表面的选择性适中时,环形体系中形成了一种在线形体系中未被观察到的具有波浪形层状结构的新颖有序结构。通过对该结构相互作用焓密度与链构象的分析发现,该结构是一种稳定态结构。此外,通过对比相同参数下环形体系与线形体系的层状结构发现,环形体系层状结构的特征尺寸明显小于线形体系。上述模拟结果表明相对于与其分子量相同的线形嵌段共聚物,环形嵌段共聚物由于其特殊的几何结构能够形成新颖的或具有更小特征尺寸的微相分离结构,而控制特征尺寸,尤其是获得尽可能小的特征尺寸,对于制备具有更小纳米结构和更高集成度的微电子器件具有重要意义。     

溶剂尺寸对ABA两亲性三嵌段共聚物在选择性溶剂中自组装行为影响的Monte Carlo模拟

采用Monte Carlo模拟方法研究了溶剂尺寸对ABA两亲性三嵌段共聚物在选择性溶剂中自组装行为的影响。模拟结果表明,溶剂尺寸是决定共聚物聚集形态的重要因素之一。随着溶剂尺寸的增大,嵌段共聚物自组装所形成的胶束可以发生从球状到棒状再到囊泡状的转变。通过对各组分的相互作用对数随溶剂尺寸变化曲线的分析发现,增大溶剂尺寸会使溶剂的溶解性变差,由此引发体系中的一系列形态转变。此外,通过对体系自组装形貌结构相图的分析发现,增大溶剂尺寸或增加疏水作用同减小亲水作用对于自组装形态的改变具有同等效果。     

棒-棒二嵌段共聚物自组装行为的自洽场研究

利用格子自洽场模型, 模拟了棒-棒二嵌段共聚物熔体系统的自组装行为, 并与线-棒二嵌段共聚物系统性质进行了对比. 结果表明, 棒-棒二嵌段共聚物系统的有序无序转变临界点低于线-棒二嵌段共聚物系统的相变临界点. 通过模拟计算, 发现薄层交叠柱状相、柱状相、层状相和Z形层状相4种稳定的有序形貌. 薄层交叠柱状相和柱状相仅在有序无序转变曲线的边缘位置出现, 层状相也仅存在于有序无序转变临界点上面的一小块区域内, 而稳定的Z形层状结构则占据了相图中较强相互作用的大部分区域.     

小角X衍射和ESR方法研究十二烷基磺酸钠/正戊醇/水三元体系的相结构

测定了十二烷基磺酸钠/正戊醇/水体系的相图,小角X衍射方法测定相图中液晶区的结构.结果表明:在一定温度下,整个液晶区均为层状液晶;液晶层间距随水含量的增大而增大,随正戊醇含量的增大而减小;液晶内水的渗透率正比于水含量,反比于正戊醇含量.ESR研究表明:自旋标记探针分子5NS整个液晶相中的结构参数为0.32±0.02;油包水和水包油胶束区内探针分子运动的各向异性程度分别随着水和油含量的增多而增加.     

超分子模板法合成层状中孔结构氧化铝

利用烷基硫酸钠作为模板剂在室温下合成了层状中孔结构氧化铝,考察了表面活性剂碳链长度和表面活性剂混合比例对层状氧化铝中孔相结构参数的影响.当使用单一表面活性剂作为模板剂时,层状中孔结构氧化铝的层间距d及其层状结构的长程有序度随着表面活性剂碳链长度的增加而增加;若使用C₈H₁₇SO₄Na与C₁₄H₂₉SO₄Na混合表面活性剂作为混合模板剂,当C₁₄H₂₉SO₄Na摩尔分数x处在0～0.5时,层间距基本恒定,接近于具有二者平均碳链长度(n=11)的单一表面活性剂作为模板剂时的情形;当x>0.5时,层间距随x的增大而逐渐增大.通过提出的混合表面活性剂在无机层中的分子排列结构模型对该结果做了解释.     

平行板间高分子链构象熵的动力学Monte Carlo模拟

用动力学Monte Carlo方法模拟了受限于两平行板之间的高分子链,并用扫描法计算了链的构象熵S,研究了构象熵相对于自由链的减小量(S0-S)与平行板间距D和高分子链长n的关系.结果证实了de Gennes的自由能标度关系,并给出了标度关系适用的范围.当D非常小时,高分子链受到强烈限制,S0-S与n成正比,表明单链节受到平行板的平均排斥作用力与链长无关.随着D增大,平行板对构象熵的影响越来越弱,单链节受到平行板的平均排斥作用力随链长的增长而增大.当D比较大时,平行板对构象熵的影响近似可以忽略,高分子链构象熵与自由空间中的结果一致.     

多分散性对两亲性两嵌段共聚物在选择性溶剂中自组装行为影响的Monte Carlo模拟

采用Monte Carlo模拟方法研究了多分散性AB两亲性两嵌段共聚物在选择性溶剂中的自组装行为.模拟结果表明,嵌段共聚物的多分散性对体系在选择性溶剂中自组装所形成的胶束形貌结构有很大影响.当AB两嵌段共聚物的多分散系数由1.0增加至1.4时,体系中自组装所形成的胶束将会发生由囊泡到片层直至球状的一系列形态转变.通过统...     

丁二烯/苯乙烯/4-乙烯基吡啶共聚物蒙脱土嵌入混杂材料的研究

用聚合物乳液与蒙脱土的水分散体共混共凝的方法制备混杂材料.在混合过程中乳胶粒与蒙脱土晶层相互穿插,用盐酸絮凝,带正电的共聚物能够嵌入带负电的蒙脱土层间.萃取实验发现在混杂材料中蒙脱土吸附了大量的共聚物,说明蒙脱土晶层与共聚物之间存在静电吸附作用.XRD实验发现在混杂材料中蒙脱土的晶层结构发生了膨胀,并且变得混乱,而在共混物中蒙脱土晶层结构几乎不变.用TEM观察在混杂材料中蒙脱土晶层均匀分散于共聚物基体中,蒙脱土的层间距大于6nm.共聚物嵌入蒙脱土的层间,受到蒙脱土晶层的限制作用,共聚物的T_g发生了变化.交联以后的混杂材料的性能比共聚物有了较大的提高,蒙脱土晶层在共聚物基体中起到很好的补强作用.     

Covalently attached sandwich structure from colloidal particles and diazoresin

A covalently attached sandwich structure between layers and particles has been fabricated from z.sbnd;COOH-containing copolymer latex particles and z.sbnd;N(2)(+)-containing polymers by self-assembly combined with a UV irradiation technique. The ionic bonds involving the layers and particles change to covalent bonds under UV irradiation and the sandwich structure become very stable toward polar organic solvents and electrolyte aqueous solutions.     

Hydrophilic chain length dependence of the ionic amphiphilic polymer monolayer structure at the air/water interface

Detailed analysis of an interesting poly(methacrylic acid) (PMAA) brush structure in water of a diblock copolymer [(Et(2)SB(m)-b-(MMA)(n), where Et(2)SB is diethylsilacyclobutane] monolayer reported previously was performed by X-ray and neutron reflectometry and indicated that the hydrophilic layer formed with a relatively long PMAA chain is not a simple layer but is divided into two layers, that is, a "carpet"-like dense PMAA layer near the hydrophobic layer and a polyelectrolyte brush layer. The hydrophilic chain length dependence of the diblock copolymer monolayer was analyzed using m:n = 30:x polymer samples, especially of the PMAA double layer structure. With the increase in PMAA chain length in polymer samples, a carpet layer is mainly formed up to n approximately 50. With further increase in the PMAA chain length beyond n approximately 50, a well-defined brush layer appears. On the other hand, the variation in hydrophobic layer thickness with methacrylic acid unit is minimum at the critical PMAA length, that is, n approximately 50 under a constant surface pressure condition. It is strongly suggested that the two discrete layers contribute differently to surface pressure. Furthermore, from the comprehensive viewpoint, the major factor for brush formation was clarified not to be the absolute length of the PMAA chain, but the ratio of PEt(2)SB and PMAA chain length is an important factor.     

Monte Carlo simulation on symmetric ABA/AB copolymer blends in confined thin films

The effects of blend composition on morphology, order-disorder transition (ODT), and chain conformation of symmetric ABA/AB copolymer blends confined between two neutral hard walls have been investigated by lattice Monte Carlo simulation. Only lamellar structure is observed in all the simulation morphologies under thermodynamic equilibrium state, which is supported by theoretical prediction. When the composition of AB diblock copolymer (phi) increases, both lamellar spacing and the corresponding ODT temperature increase, which can be attributed to the variation of conformation distribution of the diblock and the triblock copolymer chains. In addition, both diblock and triblock copolymer, chains with bridge conformation extend dramatically in the direction parallel to the surface when the system is in ordered state. Finally, the copolymer chain conformation depends strongly on both the blend composition and the incompatibility parameter chiN.     

Flow mechanisms in the face-centred cubic micellar gel of a diblock copolymer

The mechanisms of flow of a face-centred cubic micellar phase were investigated using small-angle X-ray scattering (SAXS) for samples under either steady or oscillatory shear in two different geometries: Couette cell and planar shear sandwich. The system studied was a gel formed by a poly(oxyethylene)–poly(oxypropylene) diblock copolymer in water. SAXS indicated that under steady shear in a Couette cell, flow occurs via sliding of hexagonal close-packed (hcp) layers with a close-packed [110] direction along the shear direction. Under oscillatory shear in the planar shear sandwich, coexistence between this orientation and one in which the hcp layers are rotated by 30° (and flow is in a [211] direction) was observed; however, when subject to oscillatory shear in the Couette cell, flow only occurred along a [110] direction. This observation of flow in a non-close-packed direction may be due to alignment induced by the walls of the shear sandwich. Received: 24 February 2001 Accepted: 21 March 2001     

Evaporation-induced Morphology Pattern of Triblock Copolymer A5B10C5 in Thin Film： a Multibody DPD Simulation Study

We used multibody dissipative particle dynamics method,by which the attractive and repulsive interactions can be effectively considered,to investigate the evaporation-induced morphology patterns of triblock copolymer A5B10C5 in thin film.With changing attractive interactions between solvent vapor and triblock copolymer that represent various selective solvents,lamellar morphology,sandwich lamellar morphology,spherical morphology and disorder morphology patterns of the thin films were obtained for both coil-coil-coil and rod-coil-coil chain architectures,respectively.The order parameter and the film thickness were calculated during the process for characterizing the film properties,and it was found that the rigid A-block of the triblock copolymer hinders the formation of an ordered structure.     

Interaction forces between adsorbed polymer layers

The interaction forces between adsorbed polymer layers were investigated. Two types of graft copolymers that were adsorbed on hydrophobic surfaces have been investigated: (i) a graft copolymer consisting of polymethylmethacrylate/polymethacrylic acid back bone (the B chain) on which several poly(ethylene oxide) chains are grafted (to be referred to as PMMA/PEO_n); and (ii) a graft copolymer consisting of inulin (linear polyfructose with degree of polymerization > 23) (the A chain) on which several C₁₂ chains are grafted (INUTEC SP1). In the first case adsorbed layers of the graft copolymer were obtained on mica sheets and the interaction forces were measured using the surface force apparatus. In the second case the interaction forces were measured using Atomic Force Microscopy (AFM). For this purpose a hydrophobically modified glass sphere was attached to the tip of the cantilever of the AFM and the glass plate was also made hydrophobic. Both the sphere and the glass plate contained an adsorbed layer of INUTEC SP1.In the surface forces apparatus one essentially measures the energy E(D)–distance D curves for the graft copolymer of PMMA/PEO_n between mica surfaces bearing the graft copolymer and this could be converted to interaction energy between flat surfaces. Using the de Gennes scaling theory, it is possible to calculate the interaction energy between the polymer layers. The same graft copolymer was used in latex dispersions and the high frequency modulus G′_∝ was measured as a function of the volume fraction ? of the dispersion. This high frequency modulus could be related to the potential of mean force. In this way one could compare the results obtained from rheology and those obtained from direct measurement of interaction forces.In the AFM method, the interaction forces are measured in the contact area between two surfaces, i.e. a spherical glass particle and a glass plate. Both glass spheres and plates were hydrophobized using dichlorodimethylsilane. Results were obtained for adsorbed layers of INUTEC SP1 in water and in the presence of various concentrations of Na₂SO₄ (0.3, 0.8, 1.0 and 1.5 mol dm^{− 3}). All results showed a rapid increase of force with a decrease of separation distance and the forces were still repulsive up to the highest Na₂SO₄ concentration. This explains the high stability of dispersions when using INUTEC SP1 as stabilizer.     

Étude par rayons X de copolymères téléchéliques butadiène acide méthacrylique

The telechelic polybutadiene–methacrylic acid copolymer (Hycar CTB) containing 2 mole percent acid and neutralized (5–100%) by alkali ions, Na⁺, K⁺, and Cs⁺, has been studied by small-angle x-ray scattering. Salt groups form clusters, and the average value of the radii of gyration is approximately 8 Å; this value seems to be independent of the nature of the cation and the degree of neutralization. The existence of a low-angle maximum in the scattering intensity gives evidence of a mean distance of 80 Å between clusters in the fully neutralized sample. This distance increases slightly with a decreasing degree of neutralization. A more precise analysis of the small-angle scattering curve gives further information on the cluster structure: the ionic groups may form small bilayer disks while the polymer chains maintain a regular distance of 80 Å between the disks.     

Hierarchical Structure‐Within‐Structure Morphologies in A2‐star‐(B‐alt‐C) Molecules

We employ dissipative particle dynamics (DPD) to examine the self‐assembly behavior of A₂‐star‐(B‐alt‐C) molecules. We successfully observe various types of hierarchical structure‐within‐structures, such as A‐formed spheres in the matrix formed by B and C alternating layers, hexagonally packed A‐formed cylinders in the matrix with B and C segregated layers, B and C alternating layers‐within‐lamellae, coaxial B and C alternating domains within hexagonally packed BC‐formed cylinders in the A‐matrix, and co‐centric BC‐alternating domains within BC‐formed spheres in the A‐matrix, by increasing the A composition. Generally speaking, the small length‐scale B and C segregated domains are in parallel to the large length‐scale structures. This hierarchical periodicity along the same axis as well as the various characteristic structures, that the A₂‐star‐(B‐alt‐C) copolymers display, are quite different from those in A‐block‐(B‐graft‐C) coil‐comb copolymers. Moreover, it is interesting to find that when the copolymer chain length increases, though the hierarchical structure type is maintained, the number of small length‐scale lamellae that can form within the large length‐scale structure increases. These hierarchical structures under various compositions are reported theoretically for the first time in the copolymer systems consisting of the alternating blocks, and are in good agreement with the most recent experimental work by Matsushita and co‐workers (Macromolecules 2007 , 40, 4023).