English

• Block copolymers (BCPs) are composed of two or more chemically and physically distinct linear chains with dozens to hundreds identical repeating units linked together covalently [1]. The precise control over the architecture, molecular weight, chemical composition of block copolymers and their characteristics of self-assembling into periodically ordered structures with domain size of 10–100 nm make BCPs fascinating nanostructured soft materials [2-5]. They have a great variety of potential applications in many emerging fields [6-9], such as nanophotonics [10,11], semiconductor microelectronics [12,13], energy and batteries [14,15]. The simplest and most studied architecture is the AB-type diblock copolymer. Phase behavior of block copolymer is determined by three primary factors: the degree of polymerization (N), Flory-Huggins parameter (χ) and volume fraction (f) of each block [1]. Based on the self-consistent mean-field theory, Masten et al. predicted four stable equilibrium phases: spherical in a body-centered cubic lattice (BCC), hexagonally-packed cylinders (HEX), gyroid (GYR), and lamellae (LAM) [16]. Khandpur et al. proved the existence of the four equilibrium morphologies with studies of poly(isoprene-b-styrene) diblock copolymers, and observed the hexagonally perforated layer (HPL) phase, which was proved to be metastable actually, suggesting a good agreement between experimental results and phase diagram calculated by SCFT theory [17]. As a great amount of works have been published, additional phases, such as face-centered cubic (FCC) spheres [18], and A15 phase [19] have been sporadically observed in minute portions of the phase diagram. Studies of linear AB-type diblock copolymers experimentally and theoretically have laid a solid foundation for the investigation of phase behaviors of multiblock copolymers.

  To explore more phase morphologies, a third C block is added to synthesize the linear ABC-type triblock terpolymers. With more primary factors than that of linear AB-type diblock copolymers, including χ_BC, χ_AC, N_BC, N_AC, f and the block sequence, linear ABC-type phase behaviors become more complex and many phase morphologies have been predicted theoretically [20] or observed experimentally (over 30 phases have been identified to date in bulk). Taking the block sequence into consideration, linear ABC type can be defined as frustrated and non-frustrated systems. Without frustration (χ_AC ≥ χ_BC ≥ χ_AB), ABC triblock terpolymers tend to form three-domain analogues of typical AB diblock morphologies. Matsushita et al. [21,22] synthesized a series of polyisoprene-b-polystyrene-b-poly(2-vinylpyridene) (ISP) triblock terpolymers (χ_IP ≥ χ_SP ≥ χ_IS) and observed their phase morphologies by changing the volume fractions of the middle-block polymer. Tricontinuous alternating gyroid, three-domain four-layer lamella, cylindrical structure composed of two kinds of cylindrical domains, and spherical structure compose of two kinds of spherical domain were identified, which were similar to the four conventional equilibrium phases in AB-type diblock copolymers. Hiekkatalipale et al. [23] synthesized a series of polystyrene-b-polybutadiene-b-poly(tert-butyl methacrylate) (SBT) triblock terpolymers, and observed core-shell cylinder, lamella-lamella, cylinder-in-lamella, and core-shell gyroid morphologies. Core-shell structure and three-domain analogues occupied the majority of the phase diagram because the B block spread onto T block to prevent the unfavorable S/T interface (χ_BT < < χ_ST). Frustrated ABC triblock terpolymers tend to form a great variety of novel phase morphologies and complex network structures. Krappe and his co-workers [24,25] conducted detailed studies on polystyrene-b-polybutadiene-b-poly(methyl methacrylate) (SBM) triblock terpolymers, and observed spheres on spheres, cylinders at cylinder, undulated/perforated cylinder in cylinder, and spheres on cylinder structure. Epps and his co-workers [26] carried out comprehensive studies on polyisoprene-b-polystyrene-b-poly(ethylene oxide) (ISO) triblock copolymers and observed orthorhombic O⁷⁰, alternating gyroid (Q²¹⁴⁾, core-shell gyroid (Q²³⁰) phase structures.

  In the present work, a series of linear PEO₁₁₃-b-PVBC₁₃₀-b-PtBS_x (E₁₁₃V₁₃₀T_x) triblock terpolymers were synthesized via a two-step reversible addition-fragmentation chain transfer (RAFT) polymerization by using poly(ethylene oxide) based chain transfer agent (PEO₁₁₃-CTA) as the first block, 4-vinylbenzyl chloride (VBC) and 4-tert-butylstyrene (tBS) as the monomers. PEO was chosen as first block because it was easily to synthesize PEO chain transfer agent for further RAFT polymerization. By choosing VBC and tBS as the second and third monomers can achieve χ_VT ≫ χ_ET > χ_EV. As a result, the obtained E₁₁₃V₁₃₀T_x triblock terpolymers were the frustrated systems. It might be expected that E₁₁₃V₁₃₀T_x triblock terpolymers can form rich phase structures depending on the PtBS block length x. Furthermore, PVBC block might be post-modified because benzyl chloride group is reactive. Five E₁₁₃V₁₃₀T_x triblock terpolymers with various x (20, 33, 66, 104, 215) were synthesized for studying the effects of PtBS block length x on the phase behavior of the triblock terpolymers by combined techniques of small angle X-ray scattering (SAXS) and transmission electron microscopy (TEM). Hexagonally-packed cylinder (HEX), hexagonally perforated layer (HPL), lamellar (LAM) phase structures were observed for E₁₁₃V₁₃₀T₆₆, E₁₁₃V₁₃₀T₁₀₄ and E₁₁₃V₁₃₀T₂₁₅, respectively, after thermal annealing. To the best of our knowledge, the stable HPL phase structure was rarely observed for triblock terpolymers by simple thermal annealing.

  Poly(ethylene oxide) (PEO₁₁₃-OH, M_n = 5000, M_w/M_n = 1.05) and 4-vinylbenzyl chloride (VBC, 98%) were purchased from Macklin. 4-tert-butylstyrene (tBS, 94%) was purchased from Alfa Aesar. VBC and tBS were purified through an alkaline alumina column (100–200 mesh) to remove inhibitor before use. 4-Cyano-4-(dodecylsulfanylthiocarbonyl)-sulfanyl pentanoic acid (CTA, 97%) was purchased from Aladdin and used as received. All other reagents, such as dichloromethane (DCM), tetrahydrofuran (THF) and toluene were of analytical grade and used as received.

  CTA (2.02 g, 5 mmol) and oxalyl chloride (2.15 mL, 25 mmol) were added into a clean glass flask with 10 mL of dry DCM and stirred at room temperature under N₂ atmosphere until no gas bubble was generated. Excess reagents were then removed under vacuum, and the residue was redissolved in dry DCM (20 mL). The flask was immersed into an ice/water bath and 25 mL of PEO₁₁₃-OH solution (0.08 mol/L in DCM) was added into the flask dropwise for about 1 h. The ice/water bath was taken away after 2 h and the reaction continued for 24 h at room temperature. The reaction mixture was concentrated and precipitated with cold diethyl ether three times. The precipitates were dried at 40 ℃ under vacuum for 12 h to give PEO based chain transfer agent (PEO₁₁₃-CTA).

  The preparation of poly(ethylene oxide-b-4-vinylbenzyl chloride) (PEO₁₁₃-b-PVBC₁₃₀) diblock copolymer was carried out by traditional RAFT method. Typically, PEO₁₁₃-CTA (0.50 g, 0.1 mmol), VBC (15.26 g, 0.1 mol), and azobisisobutyronitrile (AIBN, 1.64 mg, 0.01 mmol) were added in a 50-mL Schlenk flask containing 5.0 mL 1, 4-dioxane and stirred under nitrogen atmosphere. After the mixture was dissolved completely, three freezing-pumping-thawing cycles were performed. The Schlenk flask was then transferred to an oil bath at 80 ℃ for polymerization. After 1 h, the reaction was terminated by freezing with liquid nitrogen. The reaction mixture was precipitated with methanol for three times and the obtained diblock copolymers were dried at 40 ℃ under vacuum for 12 h.

  A similar RAFT procedure was used to synthesize the triblock terpolymers, PEO₁₁₃-b-PVBC₁₃₀-b-PtBS_x. Typically, the diblock copolymer PEO₁₁₃-b-PVBC₁₃₀ obtained above (0.50 g, 0.019 mmol), tBS (4.58 g, 28.55 mmol) and AIBN (0.31 mg, 0.0019 mmol) were added in a 50-mL Schlenk flask containing 5.0 mL toluene and stirred under nitrogen atmosphere. After the mixture was dissolved completely, three freezing-pumping-thawing cycles were performed. The Schlenk flask was then transferred to an oil bath at 90 ℃ for polymerization, and the reaction was terminated by freezing with liquid nitrogen after 1 h. The reaction mixture was dialyzed against THF for 3 days at room temperature using a dialysis membrane (MWCO 8000). The obtained solution was concentrated by rotary evaporation. The solid product was then dried at 40 ℃ under vacuum for 12 h. The triblock terpolymers PEO₁₁₃-b-PVBC₁₃₀-b-PtBS_x were abbreviated to be E₁₁₃V₁₃₀T_x, where the capital letters E, V, T represent the PEO, PVBC, and PtBS blocks, respectively, and the subscript x represents the polymerization degree of PtBS block.

  Gel permeation chromatography (GPC) was performed to determine the molecular weight distribution (M_w/M_n) of E₁₁₃V₁₃₀T_x triblock terpolymers by using a Waters GPC system calibrated with standard polystyrenes. It was measured with an elution rate of 1.0 mL/min using THF as the eluent. ¹H NMR spectra of E₁₁₃V₁₃₀T_x triblock terpolymers were recorded on a Bruker DMX-400 MHz instrument running at room temperature with tetramethylsilane (TMS) as the internal standard and CDCl₃ as the solvent. Differential scanning calorimetry (DSC) measurements were conducted using a TA Q200 instrument. Typically, 3–4 mg of E₁₁₃V₁₃₀T_x samples were sealed in an aluminum pan, which was first heated to 180 ℃ for about 5 min to erase the thermal history of samples and then cooled to −80 ℃ and reheated to 180 ℃. The heating and cooling rates were 10 ℃/min. The data curve of second heating procedure was taken for analysis. Thermogravimetric analysis (TGA) was conducted on a TA Q50 thermogravimeter under a nitrogen atmosphere with a heating rate of 10 ℃/min and a nitrogen flow rate of 20 mL/min.

  Temperature-variable small-angle X-ray scattering (SAXS) measurements of E₁₁₃V₁₃₀T_x triblock terpolymers were performed at BL16B1 beamline in Shanghai Synchrotron Radiation Facility (SSRF), China. The wavelength of the X-ray is 1.24 Å and the sample-to-detector distance was set as 2000 mm. The E₁₁₃V₁₃₀T_x triblock terpolymers were dissolved in chloroform to obtain clear solutions with a concentration of 1% w/v. The polymer solutions were slowly dried by evaporating CHCl₃ at room temperature for one week. The obtained films were annealed under vacuum at 180 ℃ for 24 h. The annealed samples were then used for SAXS measurements. Samples were heated to the setting temperature by using a Linkam hot stage with a heating rate of 10 ℃/min and then held for 2 min under nitrogen atmosphere before SAXS measurements. The exposure time was set as 20 s for data acquisition. The scattering vector was calibrated with the bull tendon. The two-dimensional (2D) SAXS patterns and one-dimension (1D) SAXS profiles were obtained by Fit2d software.

  Transmission electron microscopy (TEM) measurements were performed by using a Hitachi HT-7700 TEM operated at 80 kV. TEM sample slices with thickness of ca. 50 nm were obtained by embedding the annealed E₁₁₃V₁₃₀T_x triblock terpolymers in epoxy resin and then ultramicrotoming at about −120 ℃ using a Leica EM UC7 microtome. The sample slices were collected on copper grids and stained with osmium tetroxide (OsO₄) and ruthenium tetroxide (RuO₄) aqueous solutions (0.5% stabilized aqueous solution) for 4 h, respectively, before TEM observation.

  In order to study effects of PtBS (T) block length on the phase structure of E₁₁₃V₁₃₀T_x triblock terpolymers, five E₁₁₃V₁₃₀T_x triblock terpolymers with the same polymerization degrees of E and V blocks and different polymerization degrees of the third T block were synthesized via a two-step RAFT process, as summarized in Scheme S1 (Supporting information). The number-average molecular weights (M_n) and volume fractions of each block (f_E, f_V and f_T) of E₁₁₃V₁₃₀T_x triblock terpolymers were determined by ¹H NMR spectra, as shown in Fig. S1 (Supporting information). The molecular weight distributions (M_w/M_n) of E₁₁₃V₁₃₀T_x triblock terpolymers were measured by GPC, as shown in Fig. S2 (Supporting information). The GPC traces indicated that the five triblock terpolymers exhibited relatively narrow molecular weight distribution. Table 1 summarized the values of M_n, M_w/M_n, f_E, f_V and f_T of five E₁₁₃V₁₃₀T_x triblock terpolymers studied here [27].

  Table 1

  

  Table 1.  Characterization Data of E₁₁₃V₁₃₀T_x.

  DownLoad: CSV

  TGA measurements were carried out to determine the degradation temperature and thermal stability of the triblock terpolymers. Fig. S3 (Supporting information) shows the TGA curves of E₁₁₃V₁₃₀T_x triblock terpolymers. The temperature with 5% of weight loss was set as degradation temperature. The degradation temperature of E₁₁₃V₁₃₀T₁₀₄ triblock terpolymer was determined to be about 240 ℃. All E₁₁₃V₁₃₀T_x triblock terpolymers exhibited similar degradation temperature. Therefore, the following DSC and SAXS experiments were conducted below 240 ℃ to avoid the degradation of triblock terpolymers

  DSC experiments were conducted to measure the glass transition temperature of E₁₁₃V₁₃₀T_x triblock terpolymers and investigate the crystallization behavior of PEO block. Fig. S4 (Supporting information) shows the DSC curves of five E₁₁₃V₁₃₀T_x triblock terpolymers. No melting endothermic peak was observed for the five triblock terpolymers, suggesting that the PEO block of E₁₁₃V₁₃₀T_x was non-crystalline. These results indicated that PVBC and PtBS blocks hindered the crystallization of PEO block in E₁₁₃V₁₃₀T_x triblock terpolymers. For E₁₁₃V₁₃₀T_x triblock terpolymers with x = 20, 33, 66 and 104, only one glass transition temperature was observed and the T_g values were smaller than those of the PVBC and PtBS homopolymers. The Flory-Huggins parameters of PEO and PVBC blocks (χ_EV), PEO and PtBS blocks (χ_ET), PVBC and PtBS blocks (χ_VT) can be estimated by Hildebrand and Scoff equation [28]:

  (1)

  where ν_ref is the segment volume, which can be calculated by ν_ref = (ν_Aν_B)^1/2. ν_A and ν_B are specific volumes of block A and B, and it can be calculated by ν = M/ρ, where M is the molecular weight of each block and ρ is the density of monomer. R is the gas constant, 8.314 J mol^-1 K^-1. T is the absolute temperature. δ_A and δ_B are the Hilderbrand solubility parameters of block A and B. The specific volumes of PEO (ν_E), PVBC (ν_V) and PtBS (ν_T) blocks were about 39.11, 140 and 169 cm³/mol, respectively. The solubility parameters of PEO (δ_E), PVBC (δ_V) [29] and PtBS (δ_T) [30] were 19.1, 20.24 and 16.6 (J/cm³)^1/2, respectively. The Flory-Huggins parameters χ_EV, χ_ET, and χ_VT were then calculated to be about 0.045, 0.064 and 0.822 at 298 K. The values of χ_EV and χ_ET indicated that the PEO block showed good compatibility with PVBC and PtBS blocks, respectively, leading to the observation of single T_g for E₁₁₃V₁₃₀T_x triblock terpolymers with x = 20, 33, 66 and 104. However, when the PtBS block was long enough (x = 215), the second T_g was observed and its value is 123 ℃, which is similar to the reported T_g of PtBS homopolymer (T_g = 130 ℃ [31]).

  The phase structures of E₁₁₃V₁₃₀T_x triblock terpolymers were investigated by SAXS and TEM. Fig. 1 shows the SAXS profiles of E₁₁₃V₁₃₀T_x triblock terpolymers with various lengths of PtBS block (x = 20, 33, 66, 104, 215) at 30 ℃ and the corresponding E₁₁₃V₁₃₀ diblock copolymer. No scattering peak was observed for E₁₁₃V₁₃₀, suggesting that the phase structure of E₁₁₃V₁₃₀ was totally disordered. For E₁₁₃V₁₃₀T₂₀ and E₁₁₃V₁₃₀T₃₃, a broad scattering peak was observed from their SAXS profiles, suggesting that E₁₁₃V₁₃₀T₂₀ and E₁₁₃V₁₃₀T₃₃ exhibited disordered phase structure (DIS). The scattering peak of E₁₁₃V₁₃₀T₃₃ was stronger and sharper than that of E₁₁₃V₁₃₀T₂₀. For E₁₁₃V₁₃₀T₆₆, four scattering peaks were observed at q/q* = 1, 3^1/2, 2, 7^1/2 with the primary scattering peak centered at q* = 0.287 nm^-1, indicating that E₁₁₃V₁₃₀T₆₆ exhibited a hexagonally packed cylindrical (HEX) phase structure. For E₁₁₃V₁₃₀T₂₁₅, four scattering peaks were observed at q/q* = 1, 2, 3, 4 with the primary scattering centered at q* = 0.164 nm^-1, indicating that E₁₁₃V₁₃₀T₂₁₅ exhibited a lamellar (LAM) phase structure. Interestingly, for E₁₁₃V₁₃₀T₁₀₄, four scattering peaks were observed at q = 0.239, 0.253, 0.489 and 0.729 nm^-1. These scattering peaks can be indexed according to a hexagonally perforated lamellar (HPL) structure by calculating the crystal surface spacing d of the hexagonal lattice [32]:

  Figure 1

  

  Figure 1.  SAXS profiles of E₁₁₃V₁₃₀T₂₀, E₁₁₃V₁₃₀T₃₃, E₁₁₃V₁₃₀T₆₆, E₁₁₃V₁₃₀T₁₀₄ and E₁₁₃V₁₃₀T₂₁₅ triblock terpolymers at 30 ℃.

  DownLoad: Full-Size Img PowerPoint

  (2)

  where h, k, l are the Miller indices, and a, c are lattice parameters of the unit cell. The four observed scattering peaks can be indexed as (101), (003), (105), (215) by adopting a trigonal ABCABC… stacking sequence with a = 32.5 nm, c = 73.4 nm. The obtained lattice parameter ratio c/a was 2.25, which is similar to those reported in literature for HPL phase structure [33,34] with the same trigonal ABCABC… stacking sequence. Loo et al. [35] observed a highly regular HPL structure in polystyrene-poly(ethylene-alt-propylene) diblock copolymer with the ratio c/a = 2.24. Zin et al. [33] observed a shear-induced HPL structure in polystyrene-polyisoprene diblock copolymer with the ratio c/a = 2.20. The above results indicated that the phase structure of E₁₁₃V₁₃₀T_x triblock terpolymers became more ordered with increasing the length x of PtBS block. With increasing x from 20 to 215, the phase structure of E₁₁₃V₁₃₀T_x triblock terpolymers changed from disordered structure, HEX, HPL to LAM phase structures. The Flory-Huggins parameter χ_VT (0.822) was much larger than χ_EV (0.045) and χ_ET (0.064). The relationship of χ_VT ≫ χ_ET > χ_EV indicated that the E₁₁₃V₁₃₀T_x triblock terpolymers were frustrated systems [34], meaning that more E/T interfaces could occur easily. Increasing the length of PtBS block will thus enhance the phase separation of E₁₁₃V₁₃₀T_x triblock terpolymers, leading to the formation of enhanced ordered phase structures.

  The corresponding 2D SAXS patterns of E₁₁₃V₁₃₀T₆₆, E₁₁₃V₁₃₀T₁₀₄, and E₁₁₃V₁₃₀T₂₁₅ were showed in Fig. 2. The 2D SAXS patterns containing whole circles suggested that the formed HEX, HPL, and LAM structures were highly ordered and isotropic. The HEX and LAM phase structures are thermodynamic equilibrium phases for block copolymers and can be obtained by thermal annealing [36]. However, the HPL phase was usually obtained by shearing the melt sample of block copolymer because the HPL phase is considered to be thermodynamically metastable [37-39]. In the present work, the 2D SAXS pattern and 1D SAXS profile indicated that the HPL structure was obtained for E₁₁₃V₁₃₀T₁₀₄ only by thermal annealing without any shearing, which might suggest that the HPL phase of E₁₁₃V₁₃₀T₁₀₄ was thermodynamically stable.

  Figure 2

  

  Figure 2.  2D SAXS patterns of (a) E₁₁₃V₁₃₀T₆₆, (b) E₁₁₃V₁₃₀T₁₀₄ and (c) E₁₁₃V₁₃₀T₂₁₅ at 30 ℃.

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  To further investigate the stability of HEX, HPL and LAM phases formed for E₁₁₃V₁₃₀T₆₆, E₁₁₃V₁₃₀T₁₀₄, and E₁₁₃V₁₃₀T₂₁₅, respectively, the evolution of phase structure with increasing temperature were studied by SAXS. Fig. S5 (Supporting information) shows the SAXS profiles of E₁₁₃V₁₃₀T₆₆, E₁₁₃V₁₃₀T₁₀₄, and E₁₁₃V₁₃₀T₂₁₅ at various temperatures. It can be seen from Fig. S5 that the SAXS profiles of E₁₁₃V₁₃₀T₆₆, E₁₁₃V₁₃₀T₁₀₄, and E₁₁₃V₁₃₀T₂₁₅ were almost unchanged in the temperature range of 30 ℃ to 170 ℃. No order-to-disorder transition and order-to-order transition were observed. These results indicated that the HEX, HPL and LAM phase structures of E₁₁₃V₁₃₀T_x triblock terpolymers obtained by thermal-annealing were thermodynamically stable at 30–170 ℃.

  The phase morphologies of E₁₁₃V₁₃₀T₆₆, E₁₁₃V₁₃₀T₁₀₄, and E₁₁₃V₁₃₀T₂₁₅ triblock terpolymers were further verified by TEM observation, as shown in Fig. 3. The PEO and PVBC blocks were stained dark with RuO₄ and OsO₄, respectively. For E₁₁₃V₁₃₀T₆₆, the HEX morphology with the smaller PtBS block packing into the interiors of cylinders was observed (Fig. 3a). The domain spacing measured from TEM image was about 20.8 nm, which was close to the value of 21.9 nm calculated by d = 2π/q* from the corresponding SAXS profile. For E₁₁₃V₁₃₀T₂₁₅, the lamellar morphology containing light and dark stripes was observed (Fig. 3b). The domain spacing of LAM morphology from TEM image was about 36.8 nm, which was in good agreement with that of 38.3 nm obtained from SAXS profiles. For E₁₁₃V₁₃₀T₁₀₄, the alternate lamellae perpendicular to the projection of perforated layers without perforations were observed (Fig. 3c). The domain spacing of perforated layers from TEM image was about 26.3 nm, which well agreed with that of 26.3 nm determined from SAXS profiles. However, we were not able to observe the regions where the lamellae were perforated by hexagonally arranged domains. Nevertheless, the TEM images were consistent with the SAXS results.

  Figure 3

  

  Figure 3.  TEM images of (a) E₁₁₃V₁₃₀T₆₆, (b) E₁₁₃V₁₃₀T₂₁₅ and (c) E₁₁₃V₁₃₀T₁₀₄.

  DownLoad: Full-Size Img PowerPoint

  In summary, a series of E₁₁₃V₁₃₀T_x triblock terpolymers with the same lengths of PEO (E) and PVBC (V) blocks but various lengths x (20, 33, 66, 104, 215) of PtBS (T) block were synthesized via a two-step RAFT process. The obtained E₁₁₃V₁₃₀T_x triblock terpolymers were non-crystalline because the PVBC and PtBS blocks strongly hindered the crystallization of PEO block. With increasing x from 20 to 215, the phase structure of E₁₁₃V₁₃₀T_x triblock terpolymers became more ordered and changed from disordered structure, HEX, HPL to LAM phase structures. Such HEX, HPL and LAM phase structures of E₁₁₃V₁₃₀T_x triblock terpolymers obtained by thermal-annealing were thermodynamically stable in the temperature range of 30–170 ℃.

  Declaration of competing interest

  The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.

  Acknowledgment

  The authors thank the National Natural Science Foundation of China (Nos. 21875214, 21674097 and 21774111) for financial support and the beamline BL16B1 at SSRF for providing the beam time.

  Supplementary materials

  Supplementary material associated with this article can be found, in the online version, at doi:10.1016/j.cclet.2022.07.033.

  
  
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  Figure 1  SAXS profiles of E₁₁₃V₁₃₀T₂₀, E₁₁₃V₁₃₀T₃₃, E₁₁₃V₁₃₀T₆₆, E₁₁₃V₁₃₀T₁₀₄ and E₁₁₃V₁₃₀T₂₁₅ triblock terpolymers at 30 ℃.

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  Figure 2  2D SAXS patterns of (a) E₁₁₃V₁₃₀T₆₆, (b) E₁₁₃V₁₃₀T₁₀₄ and (c) E₁₁₃V₁₃₀T₂₁₅ at 30 ℃.

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  Figure 3  TEM images of (a) E₁₁₃V₁₃₀T₆₆, (b) E₁₁₃V₁₃₀T₂₁₅ and (c) E₁₁₃V₁₃₀T₁₀₄.

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  Table 1.  Characterization Data of E₁₁₃V₁₃₀T_x.

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