Microphase separation in block copolymers

LeiblerL., Theory of microphase separation in block copolymers. Macromolecules, 13, 1602, 1980. Eoerster S., Khandpur A.K., Zhao J., Bates E.S., Hamley I.W., Ryan A.J., and Bras W. Complex phase behavior of polyisoprene-polystyrene diblock copolymers near the order-disorder transition. Macromolecules, 21, 6922, 1994. 

Leibler L. Theory of microphase separation in block copolymers. Macromolecules 1980 13 1602-1617. 

Gaur, U. and Wunderlich, B. Study of microphase separation in block copolymers of styrene and alpha-methylstyrene in the glass transition region using quantitative thermal analysis. Macromolecules 13, 1618 (1980)... 

The phase diagram for weakly segregated diblocks was first computed within the Landau mean field approximation by Leibler (1980). Because it has proved to be one of the most influential theories for microphase separation in block copolymers, an outline of its essential features is given here.The reader is referred to the original paper by Leibler (1980) for a complete account of the theory. 

Recently, a theoretical description of microphase separation in block copolymer by Semonov has assumed significant chain stretching [185]. This work demonstrated that this assumption simplifies the description of the thermodynamics of block copolymers un-... 

These five sets of observations, plus knowledge of the phenomenon of microphase separation in block copolymers leads to a model of reverse osmosis or ion exchange membranes in which the hydrophobic portions of the polymer chains have come together to form one more or less continuous microphase, while the hydrophilic portions of the polymer chains (ionic groups, -OH groups, -NH2 or > NH groups) have "dissolved" in a small amount of water to form another more or less continuous microphase when the meni>rane is swollen in water. The hydrophilic groups, in most cases, probably form clusters but not continuous microphases in the dried membranes. 

Section 2.5). In this case the blocks A and B try to separate from each other. However, a macroscopic phase separation is impossible because the A and B blocks are tightly linked to each other within the chains. As a result, we get a pattern of micro-domains which contain mainly A blocks or B blocks, separated by fairly thin interphase regions (Figures 4.8 and C4.9). This effect is known as microphase separation in block-copolymers, and the structure that emerges is called a micro-domain structure. 

L. Leibler, Theory of Microphase Separation in Block Copolymers," Macromoiecuies. 13,1602-1617 (1980). 

Gaur U, Wunderlich B (1980) Study of Microphase Separation in Block Copolymers of Styrene and a-Methylstyrene in the Glass Transition Region using Quantitative Thermal Analysis. Macromolecules 13 1618-1625. 

Block copolymers. The multi-component systems are intramolecular, with each component occupying a certain length of chain sequences, as shown in Fig. 2.8a. They can be diblock, triblock or even multi-block copolymers. Upon the change of composition, the microphase separation in block copolymers can fabricate various geometries of regularly packed microdomain patterns with nano-scale resolution, as will be introduced in Sect. 9.3. 

Regular microstructured melts of block copolymers have been known since the 1960s [80, 81]. The main force for microphase separations in block copolymer systems is the unfavorable interaction energy between the segments of the different blocks. However, these interactions cannot be minimized by macrophase separation (as discussed in the previous chapters), because of the chemical bonds between the blocks. Hence, phase separation is restricted (at least in one direction of space) to domains which cannot be much larger than the blocks. The minimization of the interface between the domains (Le. minimization of unfavorable interactions) leads to a regular structure. The microphases formed are different in macroscopic architecture, e.g. lamellae, sphere or cylinders. Thus, the term mesophase is commonly used to describe them. 

G. Floudas, N. Hadjichristidis, M. Stamm, A.E. Likhtman, A.N. Semenov, Microphase separation in block copolymer/homopolymer blends theory and experiment. Journal of Chemical Physics 106 (1997) 3318-3328. 

In our previous beam time (RB510315) we observed a strong scattering peak at low Q in the various PUs (see Fig. 2.10) which is consistent with the microphase separation in block copolymers predicted by Leibler [203]. The phase domain dimensions varied between 10-20 nm, depending on the PUs specific composition. After straining to 300% (Fig. 2.10) the morphology is clearly disrupted with a reduction or in some PUs a total loss of domain structure. 

In this contribution, we shall discuss improvements which incorporate fluctuations into the SCF theory. Those fluctuations are particidarly important (i) in the vicinity of phase transitions (e.g., the immixing transition in a binary blend or the onset of microphase separation in block copolymers) or (ii) at interfaces, where the translational symmetry is broken and the... 

Fredrickson, G. H., and Helfand, E., Fluctuation effects in the theory of microphase. separation in block copolymers, J. Chem. Phys., 87, 697-705 (1987). 

Mixtures of two or more polymers in polymer blends are another combination of different macromolecules. The different polymer components are normally incompatible and thus show phase separation, with the minor component usually in the form of the dispersed phase and the major component as the matrix. Close to the composition of 50 50, interpenetrating structures or networks are formed. This phase separation corresponds to the microphase separation in block copolymers but-owing to the absence of covalent bonds between the components-with coarser structures. Several processes are used to enhance the compatibility between the polymer phases, including grafting, mixing with compatibilizers, or reactive blending. Compatibilizers (block copolymers, graft polymers) cause a reduction in particle size of the minor component in the matrix. Between the components, separate interfaces (only thin boundaries) and interphases (thicker layers with often an own structure) exist. 

Microphase separation in block copolymer/homopolymer blends ... 

Loshe, D.J. and Hadjichristidis, N. (1997) Microphase separation in block copolymers. Current Opinion in Colloid and... 

DYNAMICS SIMULATIONS OF MICROPHASE SEPARATION IN BLOCK COPOLYMERS... 

---