Phase Behavior of Polystyrene-b-poly(methyl methacrylate) Diblock Copolymer

Abstract

The phase behavior of polystyrene-b-poly(methyl methacrylate) (PS-b-PMMA) copolymers of various molecular weights has been studied by using small-angle X-ray scattering (SAXS) and depolarized light scattering (DLS). The empirical Flory χ, determined from scattering intensity profiles for a fully disordered PS-b-PMMA copolymer, was shown to behave differently depending on temperature range. χ was described mostly by enthalpic contribution at higher temperatures, but a dominant entropic contribution appeared in χ at lower temperatures. The order−disorder transition (ODT) temperatures for the series of copolymers with the controlled molecular weights were directly measured through SAXS and DLS. The resultant ODTs were then compared with a compressible random-phase approximation theory to determine cross interactions between block components. It was found that effective χ from theory is also mostly described by enthalpic contribution, which yields a moderate change in ODT upon the increase of copolymer molecular weight. In addition, we discussed the pressure response of the copolymer using χ from theory.

Technological strategies for self-assembly of PS-b-PDMS in cylindrical sub-10 nm nanostructures for lithographic applications

“…Topographical [46][47][48] or chemical pre-pattering [49,50] of the substrate allows registering the in-plane orientation of the nanodomains thus further improving the lateral order. While PS-b-PMMA copolymers show a remarkable technological potential, their low χ AB value (0.06 at 300 K) [51] limits the minimum domain dimension to approximately 12 nm [52,53]. Consequently, DBCs with higher χ AB were developed scaling down the domain resolution well below 10 nm.…”

Dielectric and molecular dynamics study of the secondary relaxations of poly(styrene-co-methylmethacrylate) copolymers: Influence of the molecular architecture

“…More recently, Ahn et al [15] have studied the phase behaviour of polystyrene-b-poly(methyl methacrylate) (PS-b-PMMA). In the case of poly(styrene-co-alkyl acrylate) copolymers, the acrylate monomers have a dielectric strength one hundred times higher that of the styrene monomers [16]).…”

Temperature dependence of χ and interfacial tension in the mixtures of PS and PMMA

“…For the last two decades, χ for this system has been known to possess a strong entropic a with a weak enthalpic b. [5][6][7][8] It was not until a year ago that a hidden truth regarding χ for this system was found: 9 For the PS-b-PMMA copolymer melt of M n =20,000, χ S-MMA at lower temperatures was shown to be similar to literature values, but that at higher temperatures reveals a strong enthalpic b on the contrary. Further investigation of order-disorder transition temperatures for the copolymers of various chain sizes was found to support also the enthalpically domi-…”

“…8 Meanwhile, the present author and co-workers reconsidered the whole problem for PS-b-PMMA. 9 They measured SAXS for the disordered copolymer and those exhibiting ordering transition temperatures with finely tuned molecular weights. It was found that χ for the copolymer possesses two different stages as It is seen that χ at lower temperatures is similarly anomalous to those reported previously, but χ at higher temperatures is more or less like those for typical block copolymers such as PS-b-polyisoprene, 18 which is enthalpically oriented.…”

“…It was then conjectured that the anomalously entropic χ for the PS/PMMA system originates in some role of the polar ester group of PMMA either by weak directional interaction between it and phenyl ring of PS or by potential moisture uptake to minutely alter the cross interactions between them. 9 In classical thermodynamics, it has been known that a mixture with a planar interface should satisfy the following differential for interfacial tension γ : 17,19 (3)…”