Anisochemical Homopolymer/Diblock Copolymer Thin Film Blends

Abstract

We examined the effect of the addition of homopolymers tetramethylbisphenol A polycarbonate, TMPC, and poly(norbornene−methyl-d 3-carboxylate), NBMC, on the interlamellar spacing and the phase stability of symmetric poly(styrene-b-methyl methacrylate) diblock copolymer thin films on silicon substrates. The films were of thickness h, L < h < 5L, where L is the interlamellar spacing of the microphase separated PS-b-PMMA diblock copolymer. The homopolymers considered had degrees of polymerization, N TMPC and N NBMC, comparable to one-half of the degree of polymerization of the diblock. In the TMPC/diblock blend, for low TMPC homopolymer concentrations, φTMPC < 0.2, the homopolymer chains were localized in the middle of the PS micro-ordered domains, and the interlamellar spacing increased as L/(1 − φTMPC). For φTMPC > 0.2 the morphology of the diblock copolymer changed to accommodate higher volume fractions of TMPC. This behavior is contrasted with earlier observations in the PS-b-PMMA/PS homopolymer system where this diblock accommodated considerably higher PS homopolymer volume fractions while maintaining a lamellar phase. In the NBMC/diblock system the interlamellar spacing increased as L/(1 − φNBMC) for homopolymer concentrations up to φNBMC ≈ 0.05. For φNBMC > 0.05, the NBMC formed a pure layer on the substrate, with the diblock maintaining its microphase separated structure on this layer. These results are discussed in light of mean field theory and in terms of the effect of the interfacial constraints on the phase behavior.

Phase-separation dynamics of a ternary mixture coupled with reversible chemical reaction

“…[3][4][5][6][7][8][9][10] The study of phase separation of polymer blends accompanied by chemical reaction is very important from both industrial and theoretical points of view. Reactive blending and reaction injection molding are two important industrial processes, which involve chemical reaction coupled-phase separation.…”

Giant Thermal Tunability of the Lamellar Spacing in Block‐Copolymer‐Like Supramolecules Formed from Binary‐End‐Functionalized Polymer Blends

“…On the other hand, mixing of block copolymers with other polymers provides a relatively simple route; however, the controllability is usually hampered by undesirable macroscopic demixing between the constitu-ents. [24][25][26][27][28][29][30] It has recently been demonstrated that noncovalent bonds can be used in constructing block-copolymer-like molecular complexes, [31][32][33][34][35][36][37][38] so-called supramolecules, that serve equally well as building units of nanostructures. Such noncovalent bonds include hydrogen bonding, [33][34][35][36][37][38][39] ionic interactions, [32] coordination complexation, [38] and charge-transfer interactions.…”

“…The former method is often hampered by a laborious and difficult synthesis, and the latter only allows the preparation of a limited range of microphase periods (typically less than 150 %), since the addition of a large amount of homopolymer usually leads to macrophase separation between block copolymer and homopolymer instead of a microphase. [24][25][26][27][28][29][30] Hence, the thermal control of microphase dimensions via supramolecular assembly and disassembly is advantageous since the control is in situ. Such a strong temperature sensitivity of the microphase period has never been achieved previously.…”

Variations of the lamellar period in thin films of diblock copolymers by selective staining agents

“…Since the thickness increase of A lamellae was greater than the thickness decrease of B lamellae, the lamellar period was generally increased by the blending of homopolymers. [12,13,15,16] In OsO 4 staining of PS-PB thin films, OsO 4 stains the PB lamellae by chemical absorption to carbon-carbon double bonds of PB chains. [3,4] Thus, the PB chains should be expanded to accommodate OsO 4 molecules.…”

“…[2,10] Therefore, we can accurately evaluate the lamellar period and its change by staining agents from the film thickness and the terrace height, which can be conveniently measured using atomic force microscopy (AFM). [12,13] In this study, we investigated variations of the lamellar period of symmetric diblock copolymer thin films of polystyrene-polybutadiene, polystyrene-poly(methyl methacrylate), and polystyrene-poly(4-vinylpyridine), which were stained by osmium tetroxide, ruthenium tetroxide, and iodine, respectively.…”