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本文采用自洽场理论模拟了AB/CD嵌段共聚物共混体系的自组装. 改变组分B与D间的相互作用, 得到了不同空间尺度上的两种层状结构和只能在非对称组成情况才能得到的核壳结构. 结果表明, 这种多尺度结构的形成是因为BD间排斥作用的减弱或者吸引 作用的增强导致二者间相互融合程度的增加. 当BD间的相互融合程度与AB和CD间的相互融合程度相当时, 体系会发生宏观层状与微观层状结构间的转变. 此外, 本文还从能量角度揭示了体系发生这种结构转变的深层次原因.
关键词:
嵌段共聚物
共混
多尺度结构
自洽场 相似文献
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用高分辨NMR对聚甲基硅氧烷-聚脲嵌段共聚物以及聚氰丙基甲基硅氧烷-聚脲嵌段共聚物结构进行表征,对NH形成的各种氢键进行详细的研究,同时观察了氢键在力学性能中的作用,结果发现氢键强烈地影响着力学性能。用固体1H宽线研究这类材料的相分离状况,并总结影响相分离的因素。保持硬段含量不变,增加软段分子量使相分离程度增加;保持软段分子量不变,增加硬段含量使相分离程度降低。软、硬段之间的相互作用(如氢键)使相分离程度降低。 相似文献
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利用耗散粒子动力学模拟研究了两类典型的星形两嵌段共聚高分子薄膜的微相分离行为. 结果表明,(Ax)4(By)4体系的相图较(AxBy)4体系具有明显的对称性,且前者比后者更易发生相分离,与体相中的情况相近,并可归因于两类星形高分子在结构上的差异;组成相同的星形共聚高分子体系在体相与薄膜中所形成的介观结构之间存在对应关系;减小薄膜厚度与加大A-B组分间排斥强度均有利于增强所形成结构的有序性. 同样是缘于分子结构差异,两类星形高分
子薄膜中的均方回旋半径随体系组分分率的变化规律几乎相反. 相似文献
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采用自洽场的方法对A2B共聚物熔体作了类似星形共聚物的处理,研究了该共聚物的相分离并给出了相图.与两嵌段共聚物的相图相比较而言,在A2B的相图中,只发现了三个经典的有序相:球状相、六角蜂窝形柱状相以及层状相.从两嵌段线形共聚物到Y形共聚物这一链结构上的变化使相图也发生了相应的改变:各相的相边界发生了很大的偏移并且层状相出现的区域被大大的拓宽了.因此,可以通过改变链的结构来控制高分子自组装的微相结构,从而代替传统的改变高分子链中各组分的比例. 相似文献
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采用固体NMR研究MPEG-PLA双嵌段共聚物的固态相区结构 总被引:3,自引:0,他引:3
采用固体核磁共振方法,研究了AB型聚(L-丙氨酸)聚乙二醇嵌段共聚物(MPEG-b-PLA)的固态微相结构. 13C核的交叉极化与直接极化实验表明,MPEG中存在晶态和非晶态两种相区结构,PLA则含有大量的α螺旋与少量的β折叠二级结构. 由交叉极化过程下的13C自旋-晶格弛豫时间(T1)测定结果进一步表明,MPEG链段由于嵌段结构使结晶过程受抑制,结晶度明显下降. PLA链段以结晶态形式存在,并由于大量α螺旋和β折叠有序结构的存在, 链段非常刚性,运动严重受限,而β位甲基因为可以自由旋转,所以运动能力较α位次甲基和羰基强. 相似文献
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Crystallization within the discrete spheres of a block copolymer mesophase was studied by time-resolved x-ray scattering. The cubic packing of microdomains, established by self-assembly in the melt, is preserved throughout crystallization by strong interblock segregation even though the amorphous matrix block is well above its glass transition temperature. Homogeneous nucleation within each sphere yields isothermal crystallizations which follow first-order kinetics, contrasting with the sigmoidal kinetics normally exhibited in the quiescent crystallization of bulk polymers. 相似文献
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The confined polymer reference interaction site model (Wall-PRISM) integral equation theory was applied to investigate the microphase separation behaviour of copolymers at a solid surface or in bulk. In particular, the effects of the solid surface on polymer conformation were taken into account for constructing a set of novel bridge functionals for different segments to improve the theory. After the integration of the bridge functionals, the theory can well reproduce the simulated density profiles at different microphase domains of flexible–flexible, flexible–rigid, and linear–branched copolymers. As a consequence, the application scope of the inhomogeneous theoretical approach has been extensively extended. This work provides a prospective way to quantitatively predict the density profiles in microphase separation for block copolymers with sophisticated conformation. 相似文献
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《Journal of Macromolecular Science: Physics》2013,52(4-6):1331-1348
A propylene homopolymer and three copolymers with 1-decene containing 1.82, 3.55, and 7.83 mol% of comonomer units, respectively, were prepared with metallocene catalyst and the phase behavior in the melt of these polymers was studied using simultaneous synchrotron small-angle x-ray scattering and differential scanning calorimetry. The results show that the phase behavior of the melt varies with comonomer content and the copolymers tend to be phase-separated with increasing comonomer content. The phase separation in the melt of the propylene–1-decene copolymers was further confirmed by the fitting of the experimental data with Teubner–Strey micro-emulsion model and a transition from the phase-separated melt to the disordered melt was observed. We tentatively attribute this phenomenon to the inhomogeneous intra-molecular composition distribution at high levels of comonomer and the incompatibility of propylene sequences with different lengths. Such a finding is consistent with the facts of multiple melting peaks and mixed γ and α crystal phases in the polymer solids. Since the phase behavior depends on temperature, the effect of annealing temperature, from which the copolymers were cooled, on the nonisothermal crystallization of the copolymers was also investigated. It is found that higher degree of phase separation accelerates the crystallization but reduces the crystallization enthalpy. 相似文献
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Poly(ε-caprolactone)/poly(hydroxyethyl acrylate) networks have been investigated by thermally stimulated depolarization currents (TSDC) and differential scanning calorimetry (DSC). The introduction of hydrophilic units (HEA) in the system aiming at tailoring the hydrophilicity of the system results in a series of copolymer networks with microphase separation into hydrophobic/hydrophilic domains. Polycaprolactone (PCL) crystallization is prevented by the topological constraints HEA units imposed in such heterogeneous domains. Moreover, the mobility of the amorphous PCL chains is enhanced as revealed by the main relaxation process which becomes faster. The glass transition of PHEA-rich domains shifts to lower temperatures, as the total amount of PCL in the copolymer increases, due to the presence of PCL units within the same region. The behaviour of the copolymer networks swollen with different content of water has been investigated to analyze the interaction between water molecules and hydrophobic/hydrophilic domains and provide further insights into the molecular structure of the system. 相似文献
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Erukhimovich IY 《The European physical journal. E, Soft matter》2005,18(4):383-406
The statistical theory of microphase separation in the ternary ABC triblock
copolymers is presented and the corresponding phase diagrams are built both
for the linear and miktoarm copolymers. For this purpose the Leibler weak
segregation theory in molten diblock copolymers is generalized to multi-component monodisperse block copolymers with due regard
for the 2nd shell harmonics contributions defined in the paper. The Hildebrand approximation for the χ-parameters is used.
The physical meaning of
this and alternative choices for the χ-parameters is discussed. The symmetric
AfB1-2fCf copolymers with the middle block non-selective with respect to the side ones are shown to undergo the continuous ODT not
only into the lamellar phase but also, instead, into
various non-conventional cubic phases (depending on the middle block composition it could be the simple cubic, face-centered
cubic or non-centrosymmetric phase, which reveals the symmetry of I41 32 space group No. 214 first predicted to appear in molten block copolymers). For
asymmetric linear ABC copolymers a region of compositions is found where the weakly segregated gyroid (double gyroid) phase
exists between the planar hexagonal and lamellar or one of the non-conventional cubic phases up to the very critical point.
In contrast, the miktoarm (star) ABC block copolymers with one of its arm non-selective with respect to the two others are
shown
to reveal a pronounced tendency towards strong segregation, which is preceded by increase of stability of the conventional
BCC phase and a peculiar weakly segregated BCC phase (BCC3), where the dominant harmonics belong to the 3rd coordination sphere of the reciprocal lattice. The validity region of the
developed theory is discussed and outlined in the composition triangles both for linear and miktoarm copolymers. We present
also the list of the 2nd shell harmonics (SAXS
reflections) allowed and prohibited in some of the non-conventional morphologies due to the weak segregation considerations
and comparison of our results with the preceding SCFT treatment of the ABC copolymers by Matsen. 相似文献
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R. Sabater i Serra A. Kyritsis J. L. Escobar Ivirico J. L. Gómez Ribelles P. Pissis M. Salmerón-Sánchez 《The European physical journal. E, Soft matter》2011,34(4):37
Poly( e \varepsilon -caprolactone)/poly(hydroxyethyl acrylate) networks have been investigated by thermally stimulated depolarization currents
(TSDC) and differential scanning calorimetry (DSC). The introduction of hydrophilic units (HEA) in the system aiming at tailoring
the hydrophilicity of the system results in a series of copolymer networks with microphase separation into hydrophobic/hydrophilic
domains. Polycaprolactone (PCL) crystallization is prevented by the topological constraints HEA units imposed in such heterogeneous
domains. Moreover, the mobility of the amorphous PCL chains is enhanced as revealed by the main relaxation process which becomes
faster. The glass transition of PHEA-rich domains shifts to lower temperatures, as the total amount of PCL in the copolymer
increases, due to the presence of PCL units within the same region. The behaviour of the copolymer networks swollen with different
content of water has been investigated to analyze the interaction between water molecules and hydrophobic/hydrophilic domains
and provide further insights into the molecular structure of the system. 相似文献
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G. Reiter G. Castelein P. Hoerner G. Riess J.-U. Sommer G. Floudas 《The European physical journal. E, Soft matter》2000,2(4):319-334
Spin-coated thin films of about 100nm of low-molecular-weight hydrogenated poly(butadiene-b- ethyleneoxide) (PBh-PEO) diblock copolymers have been crystallized at various constant temperatures. Crystallization has been observed in real
time by light microscopy. Detailed structural information was obtained by atomic force microscopy, mainly enabled by the large
viscoelastic contrast between amorphous and crystalline regions. The behavior in thin films is compared to the bulk properties
of the polymer. Crystallization started from an annealed microphase separated melt where optical microscopy indicated a lamellar
orientation parallel to the substrate. A small difference in the length of the crystallizable block produced significantly
different crystallization behavior, both in the bulk and in thin films. For thin films of the shortest diblock copolymer (45%
PEO content) and for an undercooling larger than about 10 degrees, crystallization created vertically oriented lamellae. These
vertical lamellae could be preferentially aligned over several micrometers when crystallization occurred close to a three-phase
contact line. Annealing at temperatures closer to the melting point or keeping the sample at room temperature for several
months allowed the formation of a lamellar structure parallel to the substrate. A tentative interpretation based on kinetically
caused chain folding and relaxation within the crystalline state, with implications on general aspects of polymer crystallization,
is presented.
Received 19 March 1999 and Received in final form 14 December 1999 相似文献
18.
We investigate pattern formation on a solid substrate of a
diblock copolymer-homopolymer mixture containing doping wettable
nanoparticles with a preferential attraction for one component of
the copolymers, using a three-order-parameter model. The
presence of doping nanoparticles under the surface-interaction
modulation breaks the isotropy in the process of
microphase-separation and macrophase-separation. This leads to the
formation of orientational microphase and macrophase structures
due to the interplay between the phase separation and wetting
particle ordering under a modulated potential at the late stage.
Simulations suggest that the microphase morphology and macrophase
morphology can be changed through adjustment of the wetting
strength, the amplitude as well as the period of the modulated
potential. It provides some important insights for changing
microphase and macrophase structures in polymer blends by
wetting-driven spinodal decomposition. 相似文献
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Antje Gottwald Dieter Jehnichen Doris Pospiech Peter Friedel Andreas Janke 《Journal of Macromolecular Science: Physics》2013,52(5-6):549-562
Multiblock copolymers (MBCPs) consisting of polysulfone (PSU) segments and segments of the liquid crystalline poly(ethyleneterephthalate-co-oxybenzoate) (PET/HBA) form rather complex morphologies. Scanning electron microscopy (SEM), small-angle X-ray scattering (SAXS), and atomic force microscopy (AFM) investigations of two block copolymers with significantly different block molecular weights proved the existence of both macro-and microphase separation. These morphologies, existing on different length scales, were found to be superimposed in the samples. A suitable fractionation procedure was used to suppress macrophase separation. Then, it was found that microphase separation is controlled by the segment molecular weights. 相似文献
20.
Li JF Fan J Zhang HD Qiu F Tang P Yang YL 《The European physical journal. E, Soft matter》2006,20(4):449-457
The spherical surface is spatially discretized with triangular lattices to numerically calculate the Laplace-Beltrami operator
contained in the self-consistent field theory (SCFT) equations using a finite volume method. Based on this method we have
developed a spherical alternating-direction implicit (ADI) scheme for the first time to help extend real-space implementation
of SCFT in 2D flat space to the surface of the sphere. By using this method, we simulate the equilibrium microphase separation
morphology of block copolymers including AB diblocks, ABC linear triblocks and ABC star triblock copolymers occurred on the
spherical surface. In general, two classes of microphase separation morphologies such as striped patterns for compositionally
symmetric block copolymers and spotted patterns for asymmetric compositions have been found. In contrast to microphase separation
morphology in 2D flat space, the geometrical characteristics of a sphere has a large influence on the self-assembled morphology.
For striped patterns, several of spiral-form and ring-form patterns are found by changing the ratio of the radius of a sphere
to the averaging width of the stripes. The specific pattern such as the striped and spotted pattern with intrinsic dislocations
or defects stems from formed periodic patterns due to microphase separation of block copolymers arranged on the curved surface. 相似文献