Miscibility diblock copolymer

Chen WC et al. Self-assembly through competitive interactions of miscible diblock copolymer/homopolymer blends Poly(vinylphenol-b-methyl methacrylate)/poly(vinyl pyrrolidone) blend. Macromolecules 2008 41(4) 1401-1410. 

Let us consider the crystallization of a model polyethylene phase (PE) that is present in strongly segregated and in miscible diblock copolymers in order to compare two very different cases where conhnement or extreme dilution can both induce fractionated crystallization. 

With diblock copolymers, similar behavior is also observed. One component is enriched at the surface and depending on miscibility and composition a surface-induced ordered lamellar structure normal to the surface may be formed. Recent investigations include poly (urethanes) [111], poly(methoxy poly (ethyleneglycol) methacrylate)/PS [112] and PS/PMMA [113, 114]. In particular the last case has been extensively studied by various techniques including XPS, SIMS, NR and optical interferometry. PS is enriched at the surface depending on blockcopolymer composition and temperature. A well ordered lamellar structure normal to the surface is found under favourable conditions. Another example is shown in Fig. 6 where the enrichment of poly(paramethylstyrene), PMS(H), in a thin film of a di-... 

Abstract This article reviews results from our group of the synthesis and characterization of diblock copolymer brushes. Results from the literature are also covered. We report a wide variety of diblock compositions and compare the miscibility of the two blocks with the tendency to rearrange in response to block-selective solvents. Also, we describe the types of polymerization methods that can be utilized to prepare diblock copolymer brushes. We have compared the molecular weight of free polymer and the polymer brush based on results from our laboratory and other research groups we have concluded that the molecular weight of the free polymer and that of degrafted polymer brushes is similar. 

Diblock copolymers, especially those containing a block chemically identical to one of the blend components, are more effective than triblocks or graft copolymers. Thermodynamic calculations indicate that efficient compat-ibilisation can be achieved with multiblock copolymers [47], potentially for heterogeneous mixed blends. Miscibility of particular segments of the copolymer in one of the phases of the bend is required. Compatibilisers for blends consisting of mixtures of polyolefins are of major interest for recyclates. Random poly(ethylene-co-propylene) is an effective compatibiliser for LDPE-PP, HDPE-PP or LLDPE-PP blends. The impact performance of PE-PP was improved by the addition of very low density PE or elastomeric poly(styrene-block-(ethylene-co-butylene-l)-block styrene) triblock copolymers (SEBS) [52]. 

In the field of thermoplastic immiscible blends, the emulsifying activity of block copolymers has been widely used to solve the usual problem of large immiscibility associated with high interfacial tension, poor adhesion and resulting in poor mechanical properties. An immiscible thermoplastic blend A/B can actually be compatibilised by adding a diblock copolymer, poly(A-b-B) whose segments are chemically identical to the dissimilar homopolymers, or poly(X-b-Y) in which each block is chemically different but thermodynamically miscible with one of the blend component. Theoretical... 

The majority of polymers are immiscible and, in bulk, they phase separate to form domains of varying sizes and shapes, depending on their relative volume fraction. This happens because of the very low entropy of mixing in the case of large polymeric molecules. Therefore, unless there is a large favorable enthalpic contribution, most polymers do not form molecularly miscible systems. The same is true for block copolymers, in which the length of each block exceeds a certain critical value. As mentioned earlier, block copolymers are systems wherein two (or more) different types of homopolymers are linked to each other at the chain end(s) diblock copolymers, represented as (A) -(B) , are systems in which two homopolymers are linked to each other at one end, while triblock copolymers, represented as (A)m-(B) -(C)p, are systems in which one central homopolymer block is linked at either end with two other homopolymers. The values m, n and p, represent the... 

Presented polymer mixtures are composed of amorphous macromolecules with different molecular architecture homopolymers and random copolymers, with different segments distributed statistically along the chain, form partly miscible isotopic and isomeric model binary blends. The mixing of incompatible polymers is enforced by two different polymers covalently bonded forming diblock copolymers. Here only homopolymers admixed by copolymers are considered. The diblock copolymer melts have been described recently in a separate review by Krausch [17]. 

As reviewed in the previous section, measurements of Ti and Tip can provide an estimation of the length scale of miscibility of polymer blends. Compared with such kinds of experiments, the results of the spin-diffusion experiments are more quantitative and straightforward. The accuracy of the results of spin-diffusion experiments relies, to a large extent, on the values of spin-diffusion coefficients (7)) employed in calculation of the constituent phase components. Despite efforts that have been made, there still lacks a suitably applicable method of directly measuring the spin-diffusion coefficients, at least for polymers. For rigid polymer below Tg, 0.8 nm /ms has been turned out to be a reliable value of spin-diffusion coefficient. The difficulty left then concerns how to determine the coefficient of the mobile phase, which is very sample dependent. Recently, through studies on diblock copolymers and blend samples with known domain sizes, Mellinger et al established empirical relations between the T2 and D as follows ... 

Last but not least, PVF2 has also been melt-blended successfully with another engineering polymer, like Noryl (PPE + PS) using a PS-PMMA diblock copolymer (41), since it is known that PPE and PS are miscible (6). Scanning... 

In other reports, solvents immiscible with water were used to form polymeric vesicles. Feijen and coworkers reported on vesicle formation for diblock copolymers of PEO and polyesters or poly(carbonates) with both water-miscible and immiscible solvents [155], In some cases it is very difficult to remove the organic solvent and experiments with vesicles formed in water-immiscible solvents are limited to some extent. 

Morphological study, together with DMTA and DSC results, confirms the expectation of miscibility of the diblock copolymer with each component of the blend. This miscibility occurs at the interphases between the components of blends, allowing enhanced interphase interactions and better stress transfer in the blend system. This is probably due to the anchoring of each sequence of the block with its corresponding component of the blend, which is in good... 

Enhanced interphase interactions, deduced from thermal and dynamic mechanical properties and morphology observed by SEM, demonstrate the efficient compatibilizing effect of iPS-fo-iPP copolymer on iPS-iPP blends. Each sequence of the iPS-fc-iPP diblock copolymer can probably penetrate or easily anchor its homopolymer phase and provide important entanglements, improving the miscibility and interaction between the iPS and iPP phases. This is in good agreement with what is inferred from the mechanical properties of the iPS-fo-iPP-iPS-iPP polyblends. 

More recently, in a series of papers [84-86], Brown has analyzed the improvement in adhesion between two immiscible polymers [i.e., poly(methyl methacrylate) (PMMA) and polyphenylene oxide (PPO)] by the presence of polystyrene-PMMA diblock copolymers. Since one of the blocks is PMMA and the other is polystyrene (PS), which is totally miscible with PPO, it was reasonably expected that the copolymer organizes at the... 

The change in volume of the copolymer as the system goes from a miscible to an immiscible state has been utilized as a qualitative measure of its ability to compatibilize a biphasic blend. This can be quantified by using the difference between the volume of the copolymer in the miscible system and the volume of the copolymer in the phase separated system at its deepest quench as a measure of the effectiveness of the copolymer as a compatibilizer. This value is plotted vs. the sequence distribution, Px in Figure 2. This data quantifies the trend that is described above the alternating and diblock copolymers are the best compatibilizers, however within the random structures, the more blocky structures is a more effective interfacial modifier than the statistically random copolymer which is more effective than an alternating-random structure. 

Test of time-temperature superposabillty for the dielectric P data of low-M and middle-M poly-isoprene/poly(p-feri butyl styrene) (PI/PtBS) miscible blends as indicated. In panels (a)-(d), the sample code numbers of the blends denote Kh M of the components. The reference temperature is T, = 90°C for aU blends. The solid curves indicate the e" data of bulk PI corrected for the PI volume fraction in the blends. These curves are shifted along the axis to match their peak frequency with that of the blends. (Etata taken, with permission, from Chen, Q., Y. Matsumiya, Y. Masubuchi, H. Watanabe, and T. Inoue. 2008. Component dynamics in polyisoprene/ poly(4-tert-butylstyrene) miscible blends. MacrvmoJeades 41 8694-8711 Chen, Q., Y. Matsumiya, Y. Masubuchi, H. Watanabe, and T. Inoue. 2011. Dynamics of polyisoprene-poly(p-tert-butylstyrene) diblock copolymer in disordered state. Macnmiolecules 44 1585-1602 Chen, Q., Y. Matsumiya, K. Hiramoto, and H. Watanabe. 2012. Dynamics in miscible blends of polyisoprene and poly(p-terf-butyl styrene) Thermo-rheological behavior of components. Polymer ]. 44102-114.)... 

Starting in the 1980 s, a number of governmental recycling policies created a demand for recycled thermoplastic olefin (TPO) for post-consumer applications. Since polystyrenes and TPOs are not miscible, polystyrene-TPO diblock copolymers are being developed to reduce the interfacial tension in PS/TPO blends. TPOs are tough materials with low stififiiess properties. If blended with polystyrene, they improve the toughness of polystyrenes. If compatibilized, the properties of PS/TPO should be similar to styrene-hydrogenated polybutadiene rubbers. 

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