Hybridization of poly(4-vinyl pyridine)-b-polystyrene-b-poly(4-vinyl pyridine) aggregates in dioxane/water solution

Self-assembly of binary blends of two triblock copolymers of poly(4-vinyl pyridine)-b-polystyrene-b-poly(4-vinyl pyridine), i.e., P4VP(43)-b-PS260-b-P4VP(43) (P1) and P4VP(43)-b-PS366-b-P4VP(43) (P2), in dioxane/water solution was studied. These two triblock copolymers individually tend to form vesicles (P2) and cylindrical micelles (P1) in dilute solution. It was found that copolymer components in the blend, sample preparation method, and annealing time had significant effect on hybridization aggregate morphology. By increasing P1 content in the copolymer blends, fraction of looped and stretched cylinders increased, while fraction of bilayers decreased. Nearly no bilayer was observed when P1 content was above 85 wt%.

Crystal Growth Transition from Flat-On to Edge-On Induced by Solvent Evaporation in Ultrathin Films of Polystyrene-b-Poly(ethylene oxide)

The transition of lamellar crystal orientation from flat-on to edge-on in ultrathin films of polystyrene-b-poly(ethylene oxide) (PS-b-PEO) via solvent vapor (toluene) treatment Was investigated. When the as-prepared film was treated in saturated solvent vapor, breakout crystals could form quickly, and then they transformed from square single crystals (flat-on lamellae) to dendrites and finally to nanowire crystals (edge-on lamellae). Initially, heterogeneous nucleation tit the polymer/substrate interface dominated the structure evolution, leading to flat-on lamellar crystals orientation. And the transition from faceted habits to dendrites indicated a transition of underlying mechanism from nucleation-controlled to diffusion-limited growth. As the solvent molecules gradually diffused into the polymer/substrate interface, it will subsequently weaken the polymer-substrate interaction.

COMPATIBILIZING EFFECT OF POLY(ETHYLENE OXIDE)-B-POLYSTYRENE-B-POLY(ETHYLENE OXIDE) IN PHENOLPHTHALEIN POLY(ETHER ETHER KETONE) POLY(2,6-DIMETHYL-1,4-PHENYLENE OXIDE) BLENDS

The morphology and mechanical behaviour of phenolphthalein poly(ether ether ketone) (PEK-C)/poly(2,6-dimethyl-1,4-phenylene oxide) (PPO) blends has been investigated. A poly(ethylene oxide)-b-polystyrene-b-poly(ethylene oxide) (PEO-PS-PEO) triblock copolymer was used as compatibilizer. It was found that PEO-PS-PEO has a compatibilizing effect on the PEK-C/PPO blends. The addition of PEO-PS-PEO to the blends greatly improves phase dispersion and interfacial interfacial adhesion and also enhances the ultimate tensile strength and Young's modulus at compositions ranging from 30 to 70% PEK-C. However, all the values of the ultimate tensile strength within the whole composition range are lower than those expected by simple additivity, probably owing to the poor mechanical properties of PEO-PS-PEO copolymer.

Spontaneous condensation in DNA-polystyrene-b-poly(l-lysine) polyelectrolyte block copolymer mixtures

We investigated the condensation of calf thymus DNA by amphiphilic polystyrene(m)-b-poly(l-lysine)(n) block copolymers (PSm-b- PLys(n), m, n = degree of polymerization), using small-angle X-ray scattering, polarized optical microscopy and laser scanning confocal microscopy. Microscopy studies showed that the DNA condenses in the form of fibrillar precipitates, with an irregular structure, due to electrostatic interactions between PLys and DNA. This is not modified by the presence of hydrophobic PS block. Scattering experiments show that the structure of the polyplexes corresponds to a local order of DNA rods which becomes more compact upon increasing n. It can be concluded that for DNA/ PSm-b- PLys(n) polyplexes, the balance between the PLys block length and the excess charge in the system plays an essential role in the formation of a liquid crystalline phase.

Nonspherical assemblies generated from polystyrene-b-poly(L-lysine) polyelectrolyte block copolymers

This report describes the aqueous solution self-assembly of a series of polystyrene(m)-b-poly(L-lysine)n block copolymers (m = 8-10; n = 10-70). The polymers are prepared by ring-opening polymerization of epsilon-benzyloxycarbonyl-L-lysine N-carboxyanhydride using amine terminated polystyrene macroinitiators, followed by removal of the benzyloxycarbonyl side chain protecting groups. The critical micelle concentration of the block copolymers determined using the pyrene probe technique shows a parabolic dependence on peptide block length exhibiting a maximum at n = approximately 20 (m = 8) or n = approximately 60 (m = 10). The shape and size of the aggregates has been studied by dynamic and static light scattering, small-angle neutron scattering (SANS), and analytical ultracentrifugation (AUC). Surprisingly, Holtzer and Kratky analysis of the static light scattering results indicates the presence of nonspherical, presumably cylindrical objects independent of the poly(L-lysine)n block length. This is supported by SANS data, which can be fitted well by assuming cylindrical scattering objects. AUC analysis allows the molecular weight of the aggregates to be estimated as several million g/mol, corresponding to aggregation numbers of several 10s to 100s. These aggregation numbers agree with those that can be estimated from the length and diameter of the cylinders obtained from the scattering results.

Investigation by Combined Solid-State NMR and SAXS Methods of the Morphology and Domain Size in Polystyrene-b-Polyethylene Oxide-b-Polystyrene Triblock Copolymers

The microphase structure of a series of polystyrene-b-polyethylene oxide-b-polystyrene (SEOS) triblock copolymers with different compositions and molecular weights has been studied by solid-state NMR, DSC, wide and small angle X-ray scattering (WAXS and SAXS). WAXS and DSC measurements were used to detect the presence of crystalline domains of polyethyleneoxide (PEO) blocks at room temperature as a function of the copolymer chemical composition. Furthermore, DSC experiments allowed the determination of the melting temperatures of the crystalline part of the PEO blocks. SAXS measurements, performed above and below the melting temperature of the PEO blocks, revealed the formation of periodic structures, but the absence or the weakness of high order reflections peaks did not allow a clear assessment of the morphological structure of the copolymers. This information was inferred by combining the results obtained by SAXS and (1)H NMR spin diffusion experiments, which also provided an estimation of the size of the dispersed phases of the nanostructured copolymers. (C) 2009 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 48:55-64,2010

The morphology of ordered block copolymer patterns as probed by high resolution imaging

The microphase separation of block copolymer (BCP) thin films can afford a simple and cost-effective means to studying nanopattern surfaces, and especially the fabrication of nanocircuitry. However, because of complex interface effects and other complications, their 3D morphology, which is often critical for application, can be more complex than first thought. Here, we describe how emerging microscopic methods may be used to study complex BCP patterns and reveal their rich detail. These methods include helium ion microscopy (HIM) and high resolution x-section transmission electron microscopy (XTEM), and complement conventional secondary electron and atomic force microscopies (SEM and TEM). These techniques reveal that these structures are quite different to what might be expected. We illustrate the advances in the understanding of BCP thin film morphology in several systems, which result from this characterization. The systems described include symmetric, lamellar forming polystyrene-b-polymethylmethacrylate (PS-b-PMMA), cylinder forming polystyrene-b-polydimethylsiloxane (PS-b-PDMS), as well as lamellar and cylinder forming patterns of polystyrene-b-polyethylene oxide (PS-b-PEO) and polystyrene-b-poly-4-vinylpyridine (PS-b-P4VP). Each of these systems exhibits more complex arrangements than might be first thought. Finding and developing techniques whereby complex morphologies, particularly at very small dimensions, can be determined is critical to the practical use of these materials in many applications. The importance of quantifying these complex morphologies has implications for their use in integrated circuit manufacture, where they are being explored as alternative pattern forming methods to conventional UV lithography.

Preparation and characterization of PSt-b-PHEMA metal hybrids

The block copolymer polystyrene-b-poly[2-(trimethylsilyloxy)ethylene methacrylate] (PSt-b-PTMSEMA) was synthesized using atom-transfer radical polymerization (ATRP). The hydrolysis of PSt-b-PTMSEMA led to the formation of an amphiphilic block copolymer, polystyrene-b-poly(2-hydroxylethyl methacrylate) (PSt-b-PHEMA), which was characterized by GPC and H-1-NMR. TEM showed that the PSt-b-PHEMA formed a micelle, which is PSt as the core and PHEMA as the shell. Under appropriate conditions, the nickel or cobalt ion cause chemical reactions in these micelles and could be reduced easily. ESCA analysis showed that before reduction the metal existed as a hydroxide; after reduction, the metal existed as an oxide, and the metal content of these materials on the surface is more than that on the surface of the copolymer metal ion. XRD analysis showed that the metal existed as a hydroxide before reduction and existed as a metal after reduction.

聚苯乙烯-聚丁二烯嵌段共聚物反转相行为的研究

本论文以聚苯乙烯（PS）一聚丁二烯（PB）三嵌段和二嵌段共聚物体系为研究对象，利用聚合物的软有序化，控制聚合物分子链的取向和聚集条件，系统地考察了嵌段共聚物在由溶液成膜的过程中动力学效应和墒效应对其相结构和相转变行为的影响。并探讨了不同相结构和其力学性能之间的构效关系。设计了聚苯乙烯（PS）一聚丁二烯（PB）（PS≈30wt％）／非选择性溶剂体系，通过改变溶剂的挥发速率，控制了嵌段共聚物薄膜相结构形成的动力学过程。在快速挥发的条件下，在嵌段共聚物中观察到了特殊的反转相结构，即共聚物中含量多的组分（PB）形成了分散相，而当溶剂挥发很慢的条件下，得到的是热力学较稳定的正常相的结构。对不同分子量的一系列嵌段共聚物的研究表明，反转相的形成和分子量相关，与聚合物的链段数目无关，只有在低于临界分子量 （Mw=70-100 KDa）的嵌段共聚物中，成膜过程的动力学过程才影响嵌段共聚物薄膜的最终相态，即形成反转相。这种依赖于分子量的相转变行为，揭示了分子链运动速度与环境变化速率的匹配对嵌段共聚物薄膜有序相结构形成的重要作用，即动力学效应对聚合物软有序化的重要作用。利用冷冻干燥的方法，进一步研究了嵌段共聚物在极慢的溶剂挥发下，由溶液膜变成固体膜的过程中，随着溶液浓度的增加，不同聚合物分子链在溶液中自组织形成有序结构的过程。结果表明反转相是由稀溶液向亚浓溶液转变的过程中形成的。通过选取具有代表性的不同亲和性的溶剂：苯和环己烷及其混合溶剂，研究了溶剂对不同链段亲和性的差异对反转相形成的影响。由聚合物一溶剂相互作用参数判断，苯是体系的良溶剂，环己烷是体系的。溶剂，而苯对PS链段有较好的亲和性，与之相反环己烷对PB链段有较好的亲和性，通过对聚苯乙烯（PS）一聚丁二烯印B）二嵌段共聚物在苯和环己烷极其混合溶剂中的相转变行为的研究发现，随着溶剂对含量少的PS链段亲和性的降低，反转相不再出现。这是由于苯与PS．链段、环己烷与PB链段有更好的亲和性，嵌段共聚物在稀溶液中，在耗尽吸引的（depletion attraction）作用下，与溶剂亲和性弱的链段，在溶液中优先发生聚集，而有序聚集后导致的混合熵的损失会被更多的因有序聚集后小分子自由体积增加引起的平移嫡的增量所补偿，因此导致了嫡驱动的软有序化。最后，通过原子力显微镜纳米压印法，分别对反转相和正常相结构的纳米力学性能进行了对比研究，讨论了不同相结构间模量的差异，结果表明软段（PB）形成分散相结构时薄膜的模量总是小于硬段（PS）形成分散相结构时薄膜的模量，这主要是由嵌段共聚物不同组分的相对含量及形成的相的结构决定的。

Fabrication of fibril like aggregates by self-assembly of block copolymer mixtures via interpolymer hydrogen bonding

This paper describes the formation of fibril like aggregates from the self-assembly of block copolymer mixture (polystyrene-b-poly(4-vinylpyridine) (PS-b-P4VP) and polystyrene-b-poly(acrylic acid) (PS-b-PAA)) via interpolymer hydrogen bonding in nonselective solvent. The hydrogen bonding between P4VP and PAA in chloroform leads to the formation of complex. When all the pyridine units in P4VP were all hydrogen bonded to acrylic acid in PAA, the formed complex is insoluble, resulting in the formation of spherical micellar aggregates and nanorods.

Formation of ordered microphase-separated pattern during spin coating of ABC triblock copolymer

In this paper, the authors have systematically studied the microphase separation and crystallization during spin coating of an ABC triblock copolymer, polystyrene-b-poly(2-vinylpyridine)-b-poly(ethylene oxide) (PS-b-P2VP-b-PEO). The microphase separation of PS-b-P2VP-b-PEO and the crystallization of PEO blocks can be modulated by the types of the solvent and the substrate, the spinning speed, and the copolymer concentration. Ordered microphase-separated pattern, where PEO and P2VP blocks adsorbed to the substrate and PS blocks protrusions formed hexagonal dots above the P2VP domains, can only be obtained when PS-b-P2VP-b-PEO is dissolved in N,N-dimethylformamide and the films are spin coated onto the polar substrate, silicon wafers or mica. The mechanism of the formation of regular pattern by microphase separation is found to be mainly related to the inducement of the substrate (middle block P2VP wetting the polar substrate), the quick vanishment of the solvent during the early stage of the spin coating, and the slow evaporation of the remaining solvent during the subsequent stage. On the other hand, the probability of the crystallization of PEO blocks during spin coating decreases with the reduced film thickness. When the film thickness reaches a certain value (3.0 nm), the extensive crystallization of PEO is effectively prohibited and ordered microphase-separated pattern over large areas can be routinely prepared.

Motion of integrated CdS nanoparticles by phase separation of block copolymer brushes

A new method of reversibly moving US nanoparticles in the perpendicular direction was developed on the basis of the phase separation of block copolymer brushes. Polystyrene-b-(poly(methyl methaerylate)-co-poly(cadmium dimethacrylate)) (PS-b-(PMMA-co-PCdMA)) brushes were grafted from the silicon wafer by surface-initiated atom transfer radical polymerization (ATRP). By exposing the polymer brushes to H2S gas, PS-b-(PMNlA-co-PCdNlA) brushes were converted to polystyrene-b-(poly(methyl methacrylate) -co-poly(methacrylic acid)(CdS)) (PS-b-(PMMA-co-PMAA(CdS))) brushes, in which US nanoparticles were chemically bonded by the carboxylic groups of PMAA segment. Alternating treatment of the PS-b-(PMMA-co-PMAA(CdS)) brushes by selective solvents for the outer block (a mixed solvent of acetone and ethanol) and the inner PS block (toluene) induced perpendicular phase separation of polymer brushes, which resulted in the reversible lifting and lowering of US nanoparticles in the perpendicular direction. The extent of movement can be adjusted by the relative thickness of two blocks of the polymer brushes.

Solvent-induced crystallization of spherical micelles formed by copolymer blends

We have followed the morphological evolution and crystallization process of spherical micelles formed by the mixture of polystyrene-b-poly(acrylic acid) (PS-b-PAA) and polystyrene-b-poly(2-vinylpyridine)b-poly(ethylene oxide) (PS-b-P2VP-b-PEO) (the core of the spherical micelles was made of P2VP and PAA blocks through hydrogen bonding in neutral solvent N,N-dimethylformamide, DMF) via DMF vapor treatment. Different phenomena, such as rupture of the film, formation of cylinder aggregates and regular square lamellae, were observed when the micelle film was treated in DMF for different times. At the early stage of annealing in DMF vapor, the micelle film became unstable and ruptured. Cylinder aggregates, within which the PEO blocks achieved the association and primary chain folding, formed as the mesophases before the nucleation of the PEO single crystals at this stage. Further treatment in DMF vapor resulted in the nucleation of the PEO blocks at the corners of quasi-square lamellae. Then a quite regular "sandwich" lamellar structure, constructed by a PEO single-crystal layer covered by two tethered layers of other amorphous blocks on the top and bottom crystal basal surfaces, formed when the film of micelles was annealed in DMF vapor for sufficient times.

Polymer concentration, shear and stretch field effects on the surface morphology evolution during the spin-coating

Polymer concentration and shear and stretch field effects on the surface morphology evolution of three different kinds of polymers (polystyrene (PS), polybutadiene (PB) and polystyrene-b-polybutadiene-b-polystyrene (SBS)) during the spin-coating were investigated by means of atomic force microscopy (AFM). For PS and SBS, continuous film, net-like structure and particle structure were observed at different concentrations. For PB, net-like structures were not observed and continuous films and radial array of droplets emerged. Moreover, we compared surface morphology transitions on different substrate locations from the center to the edge. For PS, net-like structure, broken net-like structure and irregular array of particles were observed. For SBS, net-like structure, periodically orientated string-like structure and broken-line structure appeared. But for PB, flower-like holes in the continuous film, distorted stream-like structure and irregular distributions of droplets emerged. These different transitions of surface morphologies were discussed in terms of individual material property.

THE VISCOSITY BEHAVIOUR OF SEP BLOCK COPOLYMER SOLUTION DURING ITS MICELLIZATION

The viscosities of polystyrene-b-poly (ethylene/propylene) diblock copolymer in mixed solvent of n-octane and benzene were measured. The influences of the constitution of the mixed solvent, temperature and concentration were on the viscosity investigated. During the micellization the solution viscosity increases rapidly. The results are consistent with the study on the micellization by light scattering. The average mass of micelleswas measured and the hydrodynamic radius of gyrations were calculated.