Observation of Double Gyroid and Hexagonally Perforated Lamellar Phases in ABCBA Pentablock Terpolymers

Abstract

Three symmetric linear pentablock terpolymers, poly­(tert-butyl acrylate-b-styrene-b-ethylene oxide-b-styrene-b-tert-butyl acrylate) (T z S y O x S y T z ), with similar lengths of PS (S) and PtBA (T) blocks on the two sides but various lengths of the PEO (O) block in the middle, namely, T95S62O46S62T95, T105S60O90S60T105, and T107S65O136S65T107, were synthesized from their corresponding parent triblock copolymers poly­(styrene-b-ethylene oxide-b-styrene) (S y O x S y ), that is, S62O46S62, S60O90S60, and S65O136S65. The phase behaviors of T z S y O x S y T z pentablock terpolymers were studied using synchrotron small-angle X-ray scattering and transmission electron microscopy. The PEO block length was found to significantly affect the phase structures of the obtained T z S y O x S y T z pentablock terpolymers. Although all three S y O x S y parent triblock copolymers were in disordered states, very interestingly, ordered structures were formed in all three T z S y O x S y T z pentablock terpolymers. Particularly, the double gyroid (Q230) network structure was experimentally observed for the first time in a symmetric linear ABCBA-type pentablock terpolymer, that is, T105S60O90S60T105. Moreover, the hexagonal perforated lamellae (HPL) structure was also observed in unsheared T107S65O136S65T107. Temperature-variable SAXS showed that T95S62O46S62T95 maintained an ordered lamellar phase structure in the temperature range of 25–210 °C, and an order-to-disorder transition occurred for T95S62O46S62T95 at around 170 °C. The HPL phase of T107S65O136S65T107 still partially remained with decreased ordering at a temperature of up to 210 °C.

Effect of Block Number and Weight Fraction on the Structure and Properties of Poly(butylene terephthalate)-block-Poly(tetramethylene oxide) Multiblock Copolymers

“…The less-ordered phase-separation structures observed here are quite different to those of recently reported BCPs, where distinct peaks are observed from those monodispersed samples by SAXS. − However, in the elegant works reported by Bates’ group about polyolefin-based crystalline mBCPs, the ordered lamellar structure changed to a disordered bicontinuous morphology at a high block number ( n ≥ 9). , Since the block numbers in our system are high (>7) except P1-1, our results suggest the formation of a similar disordered bicontinuous morphology.…”

Formation of genus vesicles in dilute aqueous solution by PtBAx‐b‐PS130‐b‐PEO90‐b‐PS130‐b‐PtBAx amphiphilic pentablock terpolymers

“…The phase‐separation behavior of PS and P t BA blocks within the vesicle membranes is determined by the values. χ ST is the Flory‐Huggins parameter between PS (S) and P t BA (T) blocks, which is estimated via the calculation of solubility parameters using Hildebrand and Scoff equation to be 0.045 at 25°C 28 . Note that the solubility parameters of PS and P t BA 28,45 are =17.4 (J/cm 3 ) 1/2 and =16.4 (J/cm 3 ) 1/2 , respectively.…”

“…It can be calculated from , where is the reference volume, and . The specific volumes of S and T blocks, and are 99.05 and 128 cm 3 /mol, respectively 28 …”

“…In this paper, a series of ABCBA symmetrical amphiphilic pentablock terpolymers, P t BA x ‐ b ‐PS 130 ‐ b ‐PEO 90 ‐ b ‐PS 130 ‐ b ‐P t BA x (T x S 130 O 90 S 130 T x ) with various P t BA (T) block lengths of 40, 75, 100, 165, and 200 were synthesized via two‐step atom transfer radical polymerization (ATRP), by using Br‐poly(ethylene oxide)‐Br (Br‐PEO 90 ‐Br) as the macroinitiator, styrene (St) as the first monomer and tert ‐butyl acrylate ( t BA) as the second monomer 28,29 . The ABCBA pentablock terpolymer is considered as the simplest model system of multiblock copolymers, which are thought to be good candidates for understanding the solution properties of biomacromolecules 30,31 .…”

Pyrrole-Containing ABA Triblock Brush Polymers as Dual Functional Molecules to Facilely Access Diverse Mesostructured Materials

“…Compared with diblock copolymer systems, multiblock copolymer systems possess additional composition and interaction parameters as well as adjustable segment sequences, − which can substantially affect the self-assembly process and increase the complexity of their phase separation. − Thereby, using triblock copolymers rather than diblock copolymers as structure-directing agents provides more opportunities for creation of novel mesoporous materials and exhibits easier access to bicontinuous network structures with the triply periodic hyperbolic-surface structures, − noncentrosymmetric structures, hierarchical mesostructures, bilayer perforated lamellae, − novel helical structures, and so on. To date, apart from Pluronic triblock copolymers, many tailor-made ternary amphiphilic block copolymer systems have also been developed for preparing mesoporous materials with various compositions based on their unique self-assembly behavior.…”