Well-Ordered Lamellar Microphase-Separated Morphology of an ABA

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Well-Ordered Lamellar Microphase-Separated Morphology of an ABA Triblock Copolymer Containing a Main-Chain Liquid Crystalline Polyester as the Middle Segment 2: Influence of Amorphous Segment Molecular Weight Maito Koga, Ryohei Ishige, Kazunori Sato, Toshinari Ishii, Sungmin Kang, Koichi Sakajiri, Junji Watanabe, and Masatoshi Tokita* Department of Organic and Polymeric Materials, Tokyo Institute of Technology, Ookayama, Meguro-ku, Tokyo 152-8552, Japan ABSTRACT: A series of an ABA triblock copolymer with amorphous polymethacrylate A blocks and a main-chain liquidcrystal (LC) polyester center block were prepared with the molecular weight of the amorphous blocks (Mn am) ranging from 2300 to 10 000 and that of the LC block kept constant at 10 000. Irrespective of asymmetric compositions, all block copolymers invariably formed lamellar microstructures. The LC segments were more extended perpendicular to the interface to form smectic layers parallel to the lamellae and folded to be accommodated in lamellae, whereas the amorphous segments had dimensions similar to those of segments in amorphous block copolymer microdomains. Increases in Mn,am enlarge the interfacial area between the amorphous and LC segments and increase the number of folds in LC segments. Thus, LC lamellar thickness decreases and counterbalances the increase in amorphous lamellar thickness so as to suppress the lamellar spacing increase. When the LC segment was in the isotropic phase, the lamellae in the copolymers at asymmetric fractions were disordered and developed on cooling simultaneously with LC formation. The lamellar formation is attributed to the smectic layers that prefer a flat microdomain interface from an energetic perspective.

1. INTRODUCTION Liquid crystal (LC) block copolymers composed of LC and isotropic blocks are interesting because the LC orientation owing to an external field can induce macroscopic orientation of the microdomans. Large-area amorphous cylinder alignments in LC block copolymers have been achieved by the application of a magnetic field.1−3 The anchoring of LC relative to the substrate induced orientations of lamellae or amorphous cylinders in ultrathin films.4 Under shear flow, a smectic LC aligned the layer normal parallel to the velocity gradient direction; therefore, the microcylinders immersed in the smectic LC matrix had to compromise their orientation so as to lie in the velocity gradient direction, although they could not avoid being tilted by the shear deformation.5 In addition, microdomain morphology itself can be influenced by liquid crystallinity. Upon the transition from isotropic to nematic phases in the LC segments, the amorphous segments changed their shape from spherical into cylindrical in order to avoid LC director distortion.6 Smectic LC block copolymers formed a lamellar morphology at unusually low LC compositions.7 In some smectic LC block copolymers, lamellar spacing increased with decreasing temperature in the LC temperature region corresponding to change in the LC segment configuration from a random coil to a more extended configuration in the lamellar normal direction.8−10 In most of these copolymers, LC mesogens lie parallel to the microdomain interface. Such homogeneous anchoring of the © 2012 American Chemical Society

mesogens on the interface is attributed to the chemical structure of LC segments in block copolymers. The LC segments are the sidechain type and have mesogens in the side chains. Such a combshaped LC segment tends to stretch the backbone perpendicular to the interface, so the mesogens in the side chain are parallel to the interface. If mesogenic moieties are embedded in the chain backbone as in the case of the main-chain LC polymers (MCLCPs), the mesogens as well as chain backbone will lie perpendicular to the interface to produce other types of coupling between the microdomain and LC. In a previous study,11 we reported on an LC block copolymer having a main-chain LC polyester segment. The block copolymer was an ABA triblock consisting of poly(methyl methacrylate) (PMMA) as amorphous end blocks (A) and MCLCP of BB-5(3-Me) as the LC central block (B) with the volume fraction of amorphous segment of 44%. Though the LC block was synthesized by melt condensation and has a molecular weight distribution as large as 2, these two types of segments were segregated from each other to form lamellae that showed a clear small-angle X-ray scattering (SAXS) profile. Combining the wide-angle X-ray diffraction (WAXD) pattern and the SAXS profile demonstrated that the BB5(3-Me) segment adopted the most extended conformation and lay Received: July 25, 2012 Revised: November 2, 2012 Published: November 28, 2012 9383

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perpendicular to the lamellae to form smectic layers parallel to the lamellae. Thus, the mesogens established homeotropic alignment on the microdomain boundary. The LC lamellar thickness was 12 nm, which is much smaller than the contour chain length of the BB-5(3-Me) segment (52 nm), suggesting that the LC segment is folded at every seven repeats and is accommodated in the LC lamella. In this study, we examine the effects of the molecular weight of the amorphous segment on the microdomain morphology of the LC triblock copolymers. A series of the LC block copolymer were prepared using an identical BB-5(3-Me) with a molecular weight of 10 000. The amorphous segment attached to the LC segment is poly(ethyl methacrylate) (PEMA) as well as PMMA, and the molecular weight ranges from 2300 to 10 000. All copolymers formed well-ordered lamellar microdomains with the smectic layers lying parallel to the lamellae. On the other hand, when the LC segment was in the isotropic phase, the lamellae of the copolymers at fractions removed from the equal fraction were disordered, and lamellar microdomains developed on cooling simultaneously with smectic LC formation.

monochromator and a pinhole collimator. The SAXS pattern was measured using Cu Kα radiation with a Bruker AXS Nano-STAR-U. The synchrotron radiation (SR)-SAXS measurement was performed at a BL-10C beamline in Photon Factory, Tsukuba, Japan, equipped with a one-dimensional position-sensitive proportional counter having 512 channels with a camera length of ∼2 m. The scattering intensity was corrected by transmission and subtraction of background scattering and plotted against the scattering vector q = 4π sin θ/λ. Transmission electron microscopy (TEM) observation was performed using a Hitachi H-7650 Zero A. Density was measured by the sink-float method in an aqueous potassium bromide solution at 20 °C whose density was determined pycnometrically.

2. EXPERIMENTAL SECTION

Table 2. Thermal Properties of Block Copolymersa

3. RESULTS AND DISCUSSION 3.1. Phase Transition of the LC Segment. The LC segments in the block copolymers were well segregated from the polymethacrylate segments and showed phase transitions similar to those observed for the BB-5(3-Me) homopolymer used in previous studies.12−15 The BB-5(3-Me) homopolymer showed the glass transition and the isotropization of the smectic CA (SmCA) LC at Tg = 30 °C and Ti = 150 °C, respectively, in the heating DSC thermogram. The enthalpy change on the isotropization was 3.8 kJ mol−1. The block copolymers as well as precursor hydroxyl-terminated BB-5(3-Me) showed lower values for isotropization and comparable glass transition temperatures (see Table 2). These can be explained by the

2.1. Materials. ABA triblock copolymers were synthesized using our previously reported procedure.11 The melt transesterification of dimethyl p,p′-bibenzoate and excess of 3-methyl-1,5-pentanediol with isopropyl titanate catalyst at 240 °C yielded hydroxy-terminated BB-5(3-Me) polyester with a number-average molecular weight Mn = 10 000 and polydispersity index Mw/Mn = 2.03. α,ω-2-Bromoisobutyrate BB-5(3-Me) polyester telechelic was prepared by reacting the hydroxyl-terminated polyester with 2-bromoisobutyrate bromide and served as macroinitiator for the copper(I)-catalyzed atom-transfer radical polymerization (ATRP) of methyl or ethyl methacrylate at 50 °C using 1,1,1,3,3,3-hexafluoro-2-propanol as a solvent to yield polydisperse yet unimodal ABA triblock copolymers. The block copolymers are identified as xM or xE, where M and E stand for the species of the amorphous segment monomer (M and E corresponds to methyl methacrylate and ethyl methacrylate, respectively), and x is the amorphous segment weight percentage. Mn of the LC and amorphous segments (Mn,LC, Mn,am) and the polydispersity of the copolymers Mw/Mn were determined by 1H NMR spectroscopy analysis and gel permeation chromatography (GPC), respectively. Mn,LC, Mn,am, and Mw/Mn of the triblock copolymers are listed in Table 1.

a

Mn,LCa

Mn,ama

Mw/Mnb

OH-terminated-BB-5(3-Me) 50E 41M 39E 30M 26M 19E

10 000 10 000 10 000 10 000 10 000 10 000 10 000

10 000 6 800 6 500 4 300 3 500 2 300

2.03 1.99 1.74 1.76 1.88 1.74 1.85

Ti (°C), ΔHi (kJ mol−1)

OH-terminated-BB-5(3-Me) 50E 41M 39E 30M 26M 19E

145, 3.55 143, 2.72 143, 2.95 143, 3.00 140, 2.78 140, 2.44 138, 2.78

Tg,LC (°C) Tg,am (°C) 26 33 34 32 33 32 30

70 100 b 93 b b

a

Determined from the heating DSC thermogram measured at a rate of 10 °C min−1. bNot detected.

difference in the molecular weight of the LC polymer. Mn estimated by GPC for the precursor hydroxyl-terminated BB5(3-Me) is 29 000, much lower than that of homopolymers (about 50 000). Besides these transitions in the BB-5(3-Me) segment, the glass transition of PMMA or PEMA segment was detected for some copolymers. The type of mesophase was well identified from the WAXD pattern. Figure 1a shows a typical two-dimensional WAXD pattern of the fibrous sample of the block copolymer. Here, fiber was spun from the isotropic melt at 160 °C and subsequently annealed for 12 h at 120 °C. The pattern includes an inner layer reflection with a spacing of 1.63 nm on the meridian and a broad outer reflection with a spacing of around 0.45 nm split above and below the equator. These features are characteristic of the SmCA phase of the BB-5(3-Me) polyester,12−15 indicating that the LC segment in the block copolymer formed the SmCA phase identical to that of the BB-5(3-Me) homopolymer. Thus, the LC segments in the block copolymer formed isotropic and SmCA phases and were vitrified in the order of decreasing temperature similarly to the BB-5(3-Me) homopolymer. The layer reflections appearing on the meridian demonstrate that the smectic layers lie perpendicular to the fiber axis.

Table 1. Characterization of Polymers sample

sample

Determined from 1H NMR. bDetermined from GPC.

2.2. Methods. Differential scanning calorimetry (DSC) was performed using a PerkinElmer Pyris 1 DSC calorimeter equipped with an Intracooler II under a flow of dry nitrogen. The WAXD pattern was recorded on an imaging plate using Cu Kα radiation, generated by a Rigaku UltraX18 X-ray generator equipped with a graphite crystal 9384

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The ratios of the scattering vectors (q) at the peaks are 1, 2, 3, 4, 5, and 6, indicating the existence of lamellae stacking along the fiber axis direction. The lamellae consist of LC and amorphous segments segregated from each other. These WAXD and SAXS patterns indicate that in the LC lamellae, the smectic layers are parallel to the lamellae. The scattering intensity averaged over azimuthal sectors of 10° on each side of the meridian and plotted against q is shown for all block copolymers in Figure 2. One can find that the relative heights of the peaks of the successive order differ between block copolymers. Because the relative peak height is simply associated with the relative ratio of the thicknesses of the two types of lamellae, we can estimate the thickness of each lamella by comparing the observed intensity with the scattering profile calculated numerically using the paracrystal theory. The intensity of the scattering from the lamellar structure consisting of A and B phases can be calculated by the following equation: ⎛ Δρ ⎞2 1 I1(q) = 2N ⎜ ⎟ 2 q (1 ) 4 − + g g gA gB sin 2(qd0/2) ⎝ ⎠ A B × [(1 − gA )(1 − gB)(1 − gA gB)] + 2gA (1 − gB2) sin 2(qdA /2)

Figure 1. (a) WAXD and (b) SAXS patterns of the fiber sample of 39E. The fiber sample was spun from the isotropic melt at 160 °C and annealed at 120 °C of the LC phase for 12 h. The fiber axis lies in the vertical direction.

+ 2gB(1 − gA 2) sin 2(qdB/2)]

where Δρ is the difference between the scattering length densities in the two phases, N is the number of stacking lamellae, d0 is the lamellar spacing, dA is the average of the thickness of A lamella, and gA(q) = exp[−1/2σA2q2].16 σA is the standard deviation of the thickness of A lamella. dB, gB, and σB are similar expressions for B lamellae. Assuming that the lamellar spacing is much smaller than the lateral persistent length of the lamellae, the Table 3. Structural Parameters Determined by the Simulation Method sample

d0 (nm)

dLC (nm)

dam (nm)

σLC (nm)

σam (nm)

dam/d0

φv,am

50E 41M 39E 30M 26M 19E

22.4 21.9 22.8 19.4 22.4 18.0

10.2 12.1 13.0 12.6 15.7 13.5

12.2 9.8 9.8 6.8 6.7 4.5

1.5 1.0 0.6 1.0 0.9 1.3

1.0 0.8 0.7 0.5 0.5 0.4

0.54 0.45 0.43 0.35 0.30 0.25

0.52 0.41 0.42 0.31 0.26 0.20

Figure 2. Peak intensities of the SAXS pattern (dots) against the scattering vector q (= 4π sin θ/λ). The solid curve shows the calculated intensity based on the paracrystal theory (see text).

3.2. SAXS. The SAXS patterns indicate that all block polymers form lamellar microdomains. Figure 1b shows the SAXS pattern of the fibrous 39E copolymer. The pattern includes multiple sharp peaks on the meridian parallel to the fiber axis.

Figure 3. TEM micrographs of (a) 50E, (b) 41M, (c) 39E, (d) 30M, (e) 26M, and (f) 19E. BB-5(3-Me) domains are stained with RuO4 vapor to appear black while polymethacrylate domains are white. 9385

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3.3. TEM. TEM corroborates the lamellar morphology assignments for these samples derived from the SAXS profiles. While SAXS profiles shown in Figure 2 were measured for the fibrous samples with macroscopic LC and lamellar orientations, TEM observations were performed for the sample quenched from the isotropic phase and annealed at 120 °C for 12 h. Thus, the samples had a thermal history similar to that applied to the SAXS measurement but no macroscopic orientation. The bulk samples were exposed to RuO4 vapor at ambient temperature to selectively stain the LC domains and then microtomed into ultrathin sections. As seen in Figure 3, all samples formed clearly lamellar microphase-separated structures. However, the thickness ratio of the LC lamellae (dLC/d0) seems larger than that determined by SAXS. The LC lamellae may be swollen by RuO4. Thus, the lamellar microdomain morphologies are confirmed by TEM as well as by SAXS for all LC block copolymers. It is noteworthy that a lamellar structure can be formed by the block copolymer with an amorphous segment weight fraction as low as 0.19. 3.4. Density. The density of the block copolymer can be interpreted in terms of a stacked lamella model. It is assumed that (a) the LC and amorphous segments are all contained within the LC and amorphous lamellae, respectively; (b) the LC and amorphous lamellae are of uniform thicknesses dLC and dam, respectively; and (c) the interfaces between the alternating LC and amorphous lamellae are discrete. In this model, dam/d0 should be equal to φv,am which is calculated from Mn and the density of each segment. In practice, dam/d0 is comparable to φv,am as found in Table 3 and explains the density of the block copolymer ρ by the simple additive relation of ρ = ρam(dam/d0) + ρLC(1 − dam/d0), where ρam is the density of PMMA or PEMA homopolymer (1.19 and 1.12 g cm−3 for PMMA and PEMA, respectively) and ρLC is the density of BB-5(3-Me) homopolymer (1.23 g cm−3). ρ is plotted as a function of dam/d0 in Figure 4, where the solid line shows the density expected by the additive relationship. ρ of the block copolymer having PEMA segments shows good consistency with the additive relationship, whereas ρ of the block copolymers having PMMA segments are somewhat deviated from the calculated values. This implies that the interface between the LC and PMMA lamellae is not as sharp as that between the LC and PEMA lamellae. In other words, the PMMA segment may not be segregated from the LC segment as strongly as the PEMA segment. Such a difference in the microdomain interface can influence the SAXS intensity profile at large q and may be shown quantitatively by analyzing the profile in detail.17,18 3.5. Molecular Weight Dependence of Lamellar Thicknesses. Well-ordered lamellar microdomains were formed by a series of ABA triblock copolymers. With ranging values of Mn,am, the lamellar structure varies in spacing as well as in each lamellar thickness. In Figure 5, d0, dLC, and dam are plotted

Figure 4. Density of triblock copolymer (ρ) having PMMA (closed circle) or PEMA (open circle) as functions of the ratio of the amorphous lamellar thickness to the lamellar spacing (dam/d0). Solid lines show the density calculated for the copolymer using the density of PMMA (1.19 g cm−3), PEMA (1.12 g cm−3), and BB-5(3-Me) (1.23 g cm−3).

Figure 5. Lamellar spacing d0 (square) and the thicknesses of LC and amorphous lamellae (dLC and dam) (circle and triangle) of xM (closed marks) and xE (open marks) copolymers as functions of the numberaverage molecular weight of the amorphous segment (Mn,am). The lines serve as an eyeguide and have slopes of 0.13, −0.21, and 0.68 for d0, dLC, and dam, respectively.

observed scattering intensity is Iobs(q) = q−2I1(q). The solid curves in Figure 2 represent the best-fitted calculated profiles. There deviations of the first- and second-order peaks from the calculated profile were allowed because these peaks at smaller q can be smeared due to the finite resolution of instrument. The thicknesses of the amorphous and LC lamellae (dam and dLC) can be estimated with high accuracy because a slight variation in dam and dLC at a constant lamellar spacing d0 (= dam + dLC) can be sensitively detected in the profile feature. dam and dLC can be distinguished from each other by the weight fractions. dam, dLC, d0, and the standard deviations of each lamellar thickness (σLC and σam) are listed in Table 3.

Figure 6. Pseudo-two-phase models for the lamellar microdomain structures depicted for (a) 19E and (b) 50E. The LC segment with a contour length of 50 nm is folded two and four times to be accommodated in the lamella with thicknesses of 13.5 and 10.2 nm, respectively. 9386

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Figure 7. SR-SAXS profiles collected on cooling (a) 50E, (b) 41M, (c) 39E, (d) 26M, and (e) 19E from 160 to 100 °C at a rate of 1.0 °C min−1.

amorphous segment increases in volume with Mn,am and enlarges the interface with the LC segment. In the lamellar microdomains, the LC segment with a constant molecular weight has to occupy the same interfacial area as the amorphous segment. Such a condition results in a decrease in dLC with increasing Mn,am. It is interesting to note how LC segment is accommodated in the LC lamella with decreasing dLC. MCLCP segments penetrate the smectic layers lying parallel to lamellae with the most extended configuration. Thus, the average contour length lLC of

as functions of Mn,am. dam shows an increase with Mn,am, whereas dLC decreases and counteracts the increase in dam to reduce the increase in d0. dLC decreases with increasing Mn,am because the lamellar microdomain requires the LC segment to share the interface with the amorphous segment. dam increases with Mn,am according to the relationship dam ∼ Mn,am0.68, indicating that the amorphous segment has dimensions comparable to those of the segments in the amorphous block copolymers (∼M2/3).17 Thus, the 9387

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Figure 8. Position (open circle) and intensity (closed circle) of the primary peak in the SAXS profile (shown in Figure 7) plotted against temperature. The graph below shows the corresponding DSC thermogram measured at the same cooling rate.

folding of MCLCP has been discussed theoretically19,20 and estimated experimentally.12,15,21−27 On decreasing dLC, the LC segment can be accommodated in the lamella by increasing the

the MCLCP chains can be calculated to be 50 nm from Mn,LC and the smectic layer spacing. lLC is much larger than dLC, indicating that the LC segment must fold at lamellar boundaries. Chain 9388

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prepared with Mn,am values ranging from 2300 to 10 000. These copolymers invariably formed lamellar microdomains when the BB-5(3-Me) segment formed SmCA LC with layers parallel to the lamellae and exhibited SAXS profiles including several scattering maxima. Comparing the observed profile with the profile calculated from the paracrystal theory allowed estimating the thicknesses of each lamella, dam and dLC. dam increases with Mn,am as dam ∼ Mn,am0.68, indicating that the amorphous segments have dimensions similar to the segments in the amorphous block copolymers. Increasing Mn,am enlarges the area of the interface with the LC segment, decreases dLC, and slightly increases d0. The LC segment, which has a much greater contour length than dLC, is more stretched while being perpendicular to the lamella but folded to be accommodated in the LC lamella. The number of hairpin folds per LC segment increases from 2 to 4 with increasing Mn,am. The lamellar morphology was affected by the phase of the LC segment and the species of the amorphous segment. When the LC segment transformed into the isotropic liquid phase, 39E and 50E copolymers maintained lamellar microdomains, whereas 19E, 26M, and 41M copolymers were disordered. Although 41M and 39E have similar compositions, only 39E preserved the lamellar microdomain at T > Ti, suggesting that the PEMA segment is segregated from BB-5(3-Me) more strongly compared with the PMMA segment. On cooling the disordered melt of 19E, 26M, and 41M, lamellar microdomains developed simultaneously with the smectic LC formation in the LC segment. Therefore, the well-ordered lamellar microdomain formations in the block copolymers at asymmetric compositions are attributed to the formation of the smectic layers lying along the microdomain interface that prefer flat microdomain boundary from energetic considerations. The microdomain structures in the LC block copolymers with φw,am greater than 0.50 are now under investigation.

number of folds per chain. In the range of the block copolymers investigated, we can depict the MCLC segment accommodated in the lamella with increasing the average number of hairpin folds (lLC/dLC − 1) from 2 to 4 (see Figure 6). 3.6. Microphase Behavior. While the copolymers with the LC segment in the SmCA phase form well-ordered lamellar microdomains, the microdomain morphology with the LC segment in the isotropic liquid phase was dependent on x and the species of the amorphous segment. Figure 7 shows the SR-SAXS profiles measured for the 50E, 41M, 39E, 26M, and 19E copolymers on decreasing the sample temperature at a rate of 1.0 °C min−1 over the isotropic−smectic transition. In the comparison of these SAXS profiles, the copolymers can be divided into two categories: (1) 50E and 39E which exhibited scattering maxima in the entire temperature range and (2) 41M, 26M, and 19E which showed no scattering maximum at high temperatures. 50E and 39E exhibited a SAXS peak at T > Ti, suggesting that the lamellar microdomain sustained when the LC segment was in the isotropic liquid phase. The peak intensity (I) increased and the peak position (q*) shifted toward a smaller q value simultaneously with smectic LC formation. This can be clearly observed from Figure 8, where I and q* are plotted and compared with the DSC thermogram measured at the same rate as that in the SR-SAXS measurement (1.0 °C min−1). Increase of peak intensity is expected from the fact that the difference in electron densities between the isotropic liquid and LC is larger than that between two isotropic liquids. The peak position shift indicates that d0 increases on LC formation. LC orientational order will elongate the LC segments perpendicular to the lamellae to thicken the LC lamellae. Although such an LC lamellar thickening might entail a decrease in the interfacial area so as to increase the amorphous lamellar thickness, the lack of high-order scattering maxima in the SAXS profiles prevents further discussion. 41M, 26M, and 19E exhibited no SAXS maximum at T > Ti and began to develop it simultaneously with the appearance of an exothermic DSC peak and became saturated at the end of the DSC peak. The onset temperatures for the development of the SAXS peak and DSC exothermic peak decrease with decreasing x. In the SAXS profiles of 19E, the development of a scattering maximum at q* is followed by growth of a scattering maximum at 2q*. Thus, the lamellar microdomains developed directly from the disordered state similarly to other LC block copolymers.28,29 Simultaneously, smectic layers are assumed to be formed parallel to the interface. In such circumstances, a lamellar microdomain is preferred because the smectic layers will involve energetically unfavorable defects and deformations if the microdomains have curved interfaces to form spherical and cylindrical microdomains. Finally, we may note that the type of amorphous segment affects microdomain behavior. At T > Ti, 39E exhibited a SAXS maximum whereas 41M did not, although they have similar compositions. This indicates that the microphase separation of the LC block copolymer is affected by the type of amorphous segment as well as the type of phase in the LC segment. Thus, PEMA can be segregated more strongly from BB-5(3-Me) compared with PMMA. This is consistent with the suggestion derived from the correspondence of the density with that calculated by the two-phase model.

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AUTHOR INFORMATION

Corresponding Author

*Tel +81-3-5734-2834, Fax +81-3 + 5734-2888, e-mail [email protected]. Notes

The authors declare no competing financial interest.

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ACKNOWLEDGMENTS The SR-SAXS measurement has been performed under the approval of the Photon Factory Program Advisory Committee (Nos. 2009G649 and 2011G633). TEM studies were performed by Mr. Jun Koki (Technical Department, Tokyo Institute of Technology), who is gratefully acknowledged.

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REFERENCES

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4. CONCLUSIONS ABA LC triblock copolymers having a main-chain BB-5(3-Me) smectic LC segment with Mn LC = 10 000 as the central B block and PMMA or PEMA segments as the end A blocks were 9389

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