Perspective: Comments on “Theory of block copolymers. I. Domain formation in A-B block copolymers,” by D. J. Meier,J. Polym. Sci., C26, 81 (1969)

Abstract

At the time this seminal paper by Meier was published, many papers on the colloidal properties of block copolymer solutions had already appeared. The studies involved monomolecular and polymolecular micelles in solution, the possibility of intramolecular phase separation, polymeric oil-in-oil emulsions in systems composed of an A-B block copolymer, a homopolymer and/or B homopolymer in a solvent, and so on.' However, little had been done on the morphology of bulk block copolymers. The state of the art at that stage may be seen in the volumes based on some symposia on block copolymers, e.g., those at the California Institute of Technology in 1967,' in which the Meier's paper was presented, the ACS National Meetings in New York City (1969)3 and Chicago (1970).4 There were quite a number of papers on the thermal and mechanical behavior of block copolymers as thermoplastic elastomer~.'-~ These papers suggested the existence of "microdomain" structures as a consequence of the "microphase separation" between constituent block chains of A and B. However, unequivocal identifications of the microdomain morphologies in bulk block copolymers could not be achieved until the osmium tetraoxide staining method was first introduced to this field by Kato5 in 1967. This technique coupled with transmission electron microscopy on ultrathin sections clearly revealed the phase-separated microdomain structures that were typically a few hundred angstrom in size.'-' Moreover, it showed qualitatively that size and shape of the structures depended on molecular weights of the constituent block chains. These findings naturally led people to recognize that block copolymers can provide "tailormade" supermolecular structures and properties. However, how the domain morphology and its thermodynamic stability depend on molecular and thermodynamic variables was still totally unexplored, though understanding this point is crucial for the rational design of the structures and hence properties of block copolymers. Meier developed the pioneering theory of microdomain morphology in block copolymers and gave a rigorous free energy expression for the microdomain formation." The theory describes criteria for the formation of spherical microdomains and their size in terms of molecular and thermodynamic variables. Further developments of this theory for other microdomain morphologies were reviewed by him." The appearance of his theory was quite timely and stimulated basic experimental studies of (i) the domain size as a function of molecular weight, temperature, and block copolymer concentration when the neutral solvents are used; (ii) the thickness of the interface between two coexisting microdomains; (iii) a long-range order of the microdomains; (iv) morphology as a function of molecular weight ratios of the constituent blocks, and so 0n.12-14Meier's theory also stimulated further developments of fundamental statistical mechanical theories of microdomain morphology, such as those by Helfand,I5 Helfand and Wasserman,16 Leibler,17 Noolandi and Hong," S e m ...

Dynamic mechanical relaxation behavior of block copolymers at high temperatures

“…Block copolymers have attracted much attention during the past few decades 1–4. Block copolymers can exhibit a variety of morphologies, such as alternating lamellar, cylindrical, and spherical microdomains, according to the relative contributions of the different blocks 5–7.…”