Effect of composition of added random copolymer on the phase behavior of block copolymer

Blends of styrene-butadiene diblock copolymer (S-B, 52 wt% styrene content) and styrene-butadiene random copolymer (SBR) of various styrene compositions were studied by small-angle X-ray scattering, light scattering, and transmission electron microscopy. The composition of random copolymer plays an important role in the solubilization of SBR in S-B. The order-disorder transition temperature, T_ODT, decreases linearly with the addition of SBR. T_ODT decreases as the symmetry in SBR composition increases and shows the highest value in the case of homopolymers. Asymmetric butadiene-rich SBR dissolves mostly into PB microdomain of S-B to increase lamella microdomain spacing, D, and its addition makes the overall microdomains of S and B in the mixture more asymmetrical. Symmetric SBR is localized into the interface of S-B microdomain to reduce unfavorable S-B contact at the interface. The phase diagram for S-B containing asymmetric SBR shows a succession of mixed mesophases of different morphologies from lamellae and cylinder to disordered liquid phases, whereas the phase diagram containing symmetric SBR shows two homogeneous phases and one region of two-phase coexistence, where macroscopically separated phases coexist together.     

Stratification and phase separation in block copolymer coatings

Stratification, i.e. spontaneous formation of separate layers from a liquid coating containing inherently incompatible resinous components, provides a means of improving the adhesion of coatings. For mixtures of conventional homogeneous resins, surface and interface tensions are considered to be the driving forces for self-stratification, leading to films with separation patterns somewhere between purely spinodal decomposition textures and neatly separated A/B double layers.

Inherently domain-forming block copolymers mixed with partly compatible resins give various different separation patterns ranging from ABA-sandwich structures to physically interpenetrating networks of co-continuous phases with homogeneous layers — sometimes monomolecular ones — at film surfaces.

Besides tailoring adhesion to difficult substrates, block copolymer binders offer chances to achieve new interesting mechanical property profiles as required, e.g. for coatings for plastics or for stone chip-resistant surfacers useful in the automotive industry.

The temperature-dependence of mechanical properties is significantly reduced in comparison with conventional homogeneous coating binders.     

Rheological and mechanical properties of PEO/block copolymer blends

Small quantities of block copolymers from two families, styrene‐butadiene‐methylmethacrylate (SBM) and methylmethacrylate‐butylacrylate‐methylmethacrylate (MAM) have been added to a polyethylene oxide (PEO) in order to improve its processability, namely increasing its elastic modulus without increasing too much its shear viscosity. The copolymers contain one block of polymethylmethacrylate (PMMA) that is compatible with PEO; the other blocks create nano phases, dispersed in the PEO matrix. Considerable efforts were devoted to finding the best blending method, either melt processing or solution casting. PEO is very sensitive to shear, and was found to degrade both in the bulk and in solution. Degradation, which cannot be avoided, was quantified through intrinsic viscosity measurements. The rheological characterization of blends containing 1, 2, and 5 wt% block copolymer was carried out. The elastic modulus was found to increase more than the complex viscosity. Blends obtained by solution casting technique gave better results. The elongational viscosity obtained for one blend containing 5 wt% of SBM showed a slight increase with respect to the pure PEO. Mechanical properties were then investigated, through tensile tests and dynamic mechanical analysis in flexion and in torsion; the copolymer generally enhanced the mechanical properties. POLYM. ENG. SCI., 45:1385–1394, 2005. © 2005 Society of Plastics Engineers     

Miscibility studies on blends of Kraton block copolymer and asphalt

Miscibility phase behavior in blends of SBS copolymers (Kraton 1101) and asphalt has been investigated through establishment of thermodynamic phase diagrams. The observed phase diagram of the SBS/asphalt blend is an upper critical solution temperature (UCST) type with a maximum at about 20% copolymer and around 200 °C. The study on kinetics of phase decomposition has been carried out by means of time resolved light scattering at the 6/94 Kraton 1101/asphalt composition. Time-evolution of structure factor has been analyzed in the context of temporal scaling laws. The growth regime is seemingly dominated by the late stage of phase decomposition where the hydrodynamic effect is dominant. As typical for a deep off-critical quench, the cessation of domain growth occurs presumably through physical pinning.     

相转移催化剂对苯乙烯-丁二烯-苯乙烯嵌段共聚物环氧化反应的影响(英文)

研究了三辛基甲基氯化铵(MTAC)、三十二烷基三甲基氯化铵(TMAC)、十六烷基三甲基溴化铵(HTAB)、十八烷基三甲基溴化铵(OTAB)以及聚乙二醇(PEG-400)等5种相转移催化剂对苯乙烯-丁二烯-苯乙烯嵌段共聚物环氧化反应的影响.结果表明,MTAC的环氧化效果最好,当其质量分数为1.0%时,可使环氧化苯乙烯-丁二烯-苯乙烯嵌段共聚物(ESBS)的环氧基质量分数从18.1%提高到20.1%;HTAB和PEG-400有利于ESBS的环氧基质量分数的提高;而OTAB和TMAC由于自身较大的分子体积反而使ESBS的环氧基质量分数下降.傅里叶变换红外光谱分析表明,MTAC可以有效抑制环氧基开环副反应的发生.     

Monte Carlo studies of isolated AB block copolymer molecules

Recent theoretical progress in understanding conformations of AB block copolymer molecules in dilute solution is reviewed. The results of the authors' own biellipsoidal smooth density model (BEM) are compared to the findings recently reported by two independent groups, for the more rigorous self-avoiding walk models with nearest neighbor interactions (SAW). The SAW results confirm the BEM conclusions for the size and shape behavior of individual blocks under changing solvent-temperature conditions. The relative orientation and separation of the blocks depend strongly, on the magnitude of AB interactions, while the individual, block parameters are much less sensitive in this respect. Parfial segregation (or partial block mixing) is the general rule rather than the exception, and is aided by the low polymer concentrations which are, found in the overlap region in dilute solutions. A unified view of homopolymers and block copolymers emerges from these models, with homopolymers being a special case of the latter group. Inherent to BEM is the arrowhead-like overall shape of the molecules, which appears to survive under most conditions.     

Properties of a propylene-ethylene block copolymer

Although polypropylene has a unique combination of properties, its impact strength at low temperatures is sometimes insufficient. This need has been met by polypropylene/polyisobutylene blends. Today, polypropylene type copolymers (block copolymers) are available with low temperature toughness and property and processing advantages over the above blends. Ordinarily, copolymers from addition polymerization are random. In a block copolymer, the monomeric units of propylene are segregated from those of the second monomer. A block copolymer, propylene, low pressure polyethylene, ABS and polypropylene-polyisobutylene blends are compared as to general and mechanical properties, stress relaxation, stress rupture performance, low temperature performance (impact strength), high temperature performance (flexural stiffness) and processability. Not every material was used in each test. Block copolymers find applications in automotive and appliance industries, industrial parts and packages for cosmetics and food.     

PBT-PTMG嵌段共聚酯的研究

对以对苯二甲酸二甲酯、1,4-丁二醇和四氢呋喃聚醚二元醇为原料,钛酸四丁酯为催化剂制备PBT—PTMG嵌段共聚酯的工艺方法进行了研究。制备了软硬段比不同的PBT—PTMG嵌段共聚酯切片,并对其性能进行了表征。其结果显示,PBT—PTMG嵌段共聚酯的密度和硬度都随PBT含量的增大而增大,吸水率随聚醚含量增大而增大;调节PBT-PTMG嵌段共聚酯的组成可以得到具有不同力学性能的产物,且具有良好韧性。     

Temperature-composition phase diagrams of binary blends of block copolymer and homopolymer

The temperature-composition phase diagrams for six pairs of diblock copolymer and homopolymer are presented, putting emphasis on the effects of block copolymer composition and the molecular weight of added homopolymers. For the study, two polystyrene-block-polyisoprene (SI diblock) copolymers having lamellar or spherical microdomains, a polystyrene-block-polybutadiene (SB diblock) copolymer having lamellar microdomains, and a series of polystyrene (PS), polyisoprene (PI), and polybutadiene (PB) were used to prepare SI/PS, SI/PI, SB/PS, and SB/PB binary blends, via solvent casting, over a wide range of compositions. The shape of temperature-composition phase diagram of block copolymer/homopolymer blend is greatly affected by a small change in the ratio of the molecular weight of added homopolymer to the molecular weight of corresponding block (M_H,A/M_C,A or M_H,B/M_C,B) when the block copolymer is highly asymmetric in composition but only moderately even for a large change in M_H,A/M_C,A ratio when the block copolymer is symmetric or nearly symmetric in composition. The boundary between the mesophase (M₁) of block copolymer and the homogeneous phase (H) of block copolymer/homopolymer blend was determined using oscillatory shear rheometry, and the boundary between the homogeneous phase (H) and two-phase liquid mixture (L₁+L₂) with L₁ being disordered block copolymer and L₂ being macrophase-separated homopolymer was determined using cloud point measurement. It is found that the addition of PI to a lamella-forming SI diblock copolymer or the addition of PB to a lamella-forming SB diblock copolymer gives rise to disordered micelles (DM) having no long-range order, while the addition of PS to a lamella-forming SB diblock copolymer retains lamellar microdomain structure until microdomains disappear completely. Thus, the phase diagram of SI/PI or SB/PB blends looks more complicated than that of SI/PS or SB/PS blends.     

Effect of chain rigidity on block copolymer micelle formation and dissolution as observed by 1H-NMR spectroscopy

Amphiphilic copolymers poly(methyl methacrylate-b-acrylic acid), poly(methyl methacrylate-b-methacrylic acid), poly(methyl acrylate-b-acrylic acid) and poly(methyl acrylate-b-methacrylic acid) were prepared by reversible addition fragmentation chain-transfer (RAFT) polymerization. The hydrophilic polyacid blocks were either synthesized directly or formed by the hydrolysis of poly(tert-butyl acrylate) or poly(tert-butyl methacrylate) blocks. The hydrophobic blocks consisted of either the more rigid, high glass transition temperature (T _g ) poly(methyl methacrylate) or more flexible, low T _g poly(methyl acrylate) material. The hydrophilic blocks were either poly(methacrylic acid) (rigid, high T _g ) or poly(acrylic acid) (flexible, low T _g ). The micellization behavior of the polymers was studied by proton nuclear magnetic resonance (¹H-NMR) spectroscopy in mixtures of 1,4-dioxane-d₈ and D₂O. All four polymers were soluble in neat dioxane. In solutions of higher water content, the polymers with the more rigid hydrophobic blocks formed into micelles as was evidenced by broadening of the resonances resulting from the protons in those blocks. At moderate water concentration (25–50%), dissolution of the micelles was observed upon heating the solution. No micellization was observed in polymers containing the less rigid poly(methyl acrylate) hydrophobic block regardless of the identity of the hydrophilic block. As further evidence of micellization formation and dissolution, the spin-lattice (T ₁) and spin-spin (T ₂) relaxation times of protons in the hydrophobic and hydrophilic blocks were measured. Significant differences in the relaxation times as functions of temperature and solvent concentration were observed between the hydrophilic and hydrophobic blocks of the micelle-forming polymers.     

可控流变共聚PP的流变性能

用可控流变法降解共聚聚丙烯(PP)获得可控流变共聚PP。采用应力流变仪和熔体流动速率仪研究可控流变共聚PP的流变性能,考察了基础树脂、过氧化物加入量、工艺参数对最终产品流变性能的影响。在熔体流动速率大、乙烯含量低的基础树脂中加入少量过氧化物便能显著改善流动性;当过氧化物的加入量超过一定值时,低频下的聚合物复数黏度反而增加;各种工艺参数对流变性能的影响由大到小依次为:挤出温度,喂料转速,主机转速:喂料转速与主机转速之比越小,熔体流动速率越高。     

微藻油/苯乙烯-丁二烯-苯乙烯嵌段共聚物复合再生沥青流变特性及疲劳特性

将微藻油（MO）和苯乙烯-丁二烯-苯乙烯嵌段共聚物（SBS）作为复合再生剂掺入老化沥青中,以制备MO/SBS复合再生沥青。对比了复合再生沥青的基本物理性能、高低温流变特性及疲劳特性,考察了MO与SBS的配比和用量对老化沥青再生效果的影响。结果表明,纯MO再生沥青的黏弹性变形能力可在一定程度上恢复至老化前水平,但仍有一定差距;MO/SBS复合再生则可在此基础上显著提升高温抗变形性能及弹性恢复性能,且其临界温度较老化前提高1.1~9.7 ℃,同时还降低了再生沥青对疲劳应变的敏感性以提高其抗疲劳性能。但MO/SBS复合再生沥青的低温蠕变变形能力相较于基质沥青有所降低。当MO和SBS的质量分数分别为8%和4%,复合再生沥青的高低温流变及疲劳特性较佳。     

Visualization of block copolymer distribution on a sheared drop

We have visualized a fluorescently-labeled poly(styrene-b-methylmethacrylate) (NBD-PS-b-PMMA) block copolymer on the surface of a polymethylmethacrylate (PMMA) drop in a polystyrene (PS) matrix. Confocal microscopy revealed that the block copolymer distributed uniformly on the drop surface before deformation. However, in shear flow the copolymer concentration was higher at the tips and edges of the drop. Visualization of drop deformation using a counter-rotating apparatus showed enhanced drop deformation for a drop with block copolymer resulting in larger area generation. Drops with block copolymer showed widening even for shear strains exceeding 10, in contrast to bare drops, which first widened and then shrank. These results agree qualitatively with the observed distribution of fluorescent block copolymer. Copolymer concentration is highest in the regions of high curvature, where lowering interfacial tension should be most effective in retarding drop retraction. Block copolymer on these highly curved surfaces is found to be very effective since the exact theory for zero interfacial tension by Cristini fits our drop widening results well.     

苯乙烯-丁二烯-苯乙烯嵌段共聚物的环氧化研究

采用甲酸和过氧化氢（H2O2）原位生成的过氧甲酸对苯乙烯-丁二烯-苯乙烯（SBS）进行环氧化改性，制备了环氧化SBS（ESBS）。研究了原料摩尔配比及工艺条件对其环氧基质量分数的影响，利用GPC、FT—IR、^1H—NMR等手段对ESBS的结构进行了表征。结果表明，丁二烯链段上双键的反应活性大小次序为：顺-1，4-结构〉反-1，4-结构〉1，2-结构。在SBS的环氧化反应过程中，会伴有少量环氧基发生开环副反应。当SBS中C—C双键、甲酸和H202的物质的量配比为1／0．5／0．6，反应时间为2h，反应温度为60℃时，ESBS的环氧基质量分数最高，达到了18．1％。在体系中加入少量的聚乙二醇，有利于ESBS环氧慕盾量务教的提高．     

Rheological,mechanical and thermal properties of propylene‐ethylene block copolymer/polyalphaolefins blends

The rheological, thermal, and mechanical properties of propylene–ethylene block copolymer (PPB) blends with predominantly atactic molecular structure of low molecular weight polypropylene and propylene copolymers with either ethylene or 1‐butene (APAO) have been studied. It has been found that blend properties depend on comonomer type, content, and molecular weight of APAO as well as blend composition. APAO having ethylene comonomer showed better miscibility with PPB than the other ones, and high comonomer content of APAOs gave dramatic increase in impact strength over 30 wt%. It has been concluded that APAO can be used as an effective modifier of PPB. POLYM. ENG. SCI., 47:1905–1911, 2007. © 2007 Society of Plastics Engineers     

Macrolattice structure of a block copolymer in a selective solvent

Macrolattice structure in the ordered phase of a poly(styrene-b-butadiene-b-styrene) (SBS, with the bulk morphology of spherical polystyrene microdomains in the polybutadiene matrix) dissolved in a selective solvent (dodecyl methacrylate, C₁₂MA, or a 75/25 w/w mixture of C₁₂MA and butylene diacrylate, BDA) which mixes preferentially with the polybutadiene matrix was examined by means of transmission electron microscopy. The use of C₁₂MA/BDA mixture as the selective solvent provided the opportunity of freezing the macrolattice structure upon UV-initiated polymerization of the acrylic monomers when the SBS content is above ca. 60 wt%. Results indicated clearly a body-centered cubic structure, in contrast to the simple cubic packing previously proposed.     

Selective localization of multi-wall carbon nanotubes in homopolymer blends and a diblock copolymer. Rheological orientation studies of the final nanocomposites

In this study, pristine as well as polystyrene (PS) and poly(2-vinylpyridine) (P2VP) functionalized multi-wall carbon nanotubes (MWCNTs) were selectively incorporated in homopolymer binary blends of PS/P2VP and diblock copolymer (BCP) of the PS-b-P4VP type [P4VP: poly(4-vinylpyridine)]. Studies on the blends verified the chemical affinity of PS and P2VP grafted MWCNTs to the corresponding phase. Based on the results obtained from the blend systems, MWCNTs were incorporated in a PS-b-P4VP copolymer matrix with lamellar morphology and large amplitude oscillatory shear (LAOS) experiments were performed to achieve orientation of the BCP lamellae. The PS grafted MWCNTs (MWCNT-g-PS) were selectively sequestered in the PS phase and the P2VP grafted MWCNTs (MWCNT-g-P2VP) in the P4VP phase of the diblock copolymer. Unfunctionalized pristine MWCNTs were localized on the PS phase of the blend system and no special preference was observed towards the diblock copolymer PS domains. Small angle X-ray scattering (SAXS) analysis revealed the orientation of the alternating lamellae formed by the diblock copolymer when studied by LAOS. The localization of PS and P2VP grafted MWCNTs on the corresponding blend and BCP phase was also verified by transmission electron microscopy (TEM) studies.     

Influence of block lengths and symmetries of block copolymers on phase behavior of polymer A/polymer B/block copolymer ternary blends

Monte Carlo simulations were used to investigate the compatibilizing effects of diblock copolymers in A/B/A-B diblock copolymer ternary blends and triblock copolymers in A/B/triblock copolymer ternary blends, respectively. The volume fraction of homopolymer A was 19% and was the dispersed phase. The simulation results show that diblock copolymers with longer A-blocks are more efficient as compatibilizers, and symmetric triblock copolymers with a shorter middle block length are easily able to bridge each other through the association of the end blocks. This kind of triblock copolymers have relatively high ability to retard phase separation as compatibilizers.     

Combination of temperature and saturated vapor annealing for phase separation of block copolymer

Phase separation of block copolymer films is a perspective technique for the creation of nanostructured templates. The phase separation can be induced by thermal or vapor solvent annealing. However, a standardized and reproducible technique of the phase separation is still missing, even though many papers describing various experimental conditions. In this article we have tried to develop standardized and reproducible technique of the phase separation, which can be easily scaled up. For this purpose we used the combination of the thermal and vapor annealing of poly(styrene‐b‐4‐vinylpyridine) copolymer films on a glass substrate under static conditions. The technique was tailored by the choice of optimal solvent for the vapor annealing, based on the solvent–polymer interaction. Finally, the films were reconstructed by immersing in methanol or ethanol and stretching of the P4VP component during the reconstruction was investigated by the angle‐resolved X‐ray photoelectron spectroscopy. Morphology of the films was investigated by the atomic force microscopy and confocal microscopy. The kinetics of the phase separation was also studied. The presented combined technique of the thermal and vapor annealing can be easily temperature‐controlled for reproducibly obtaining the films of a desired morphology. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 41853.     

Crystallization and coalescence of block copolymer micelles in semicrystalline block copolymer/amorphous homopolymer blends

Crystallization of two oxyethylene/oxybutylene block copolymers (E₇₆B₃₈ and E₁₅₅B₇₆) from micelles in block copolymer/amorphous homopolymer blends was studied by differential scanning calorimetry (DSC) and time-resolved small angle X-ray scattering (SAXS). Unlike the simultaneous crystallization and formation of superstructure in crystallization from an ordered structure, crystallization of block copolymer from micelles can be divided into two steps. The core of the micelles firstly crystallizes individually, with first-order crystallization kinetics and homogeneous nucleation mechanism. The SAXS revealed that crystallization-induced deformation occurs for the micelles, which strongly depends on microstructure of the block copolymers. For the shorter block copolymer E₇₆B₃₈, larger deformation induced by crystallization was observed, leading to coalescence of the micelles after crystallization, while for the longer block copolymer E₁₅₅B₇₆ the micelles show little deformation and the morphology of micelle is retained after crystallization.