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Effect of the Isothermal Crystallization Method on Amorphous Block Copolymers of Aromatic Polyamides and Their Packing Behavior in Two-Dimensional Films for Screening of Potential Crystallization Ability.

INTRODUCTION

In this study, polymer chains that cannot be aligned are arranged. That is, polymer chains with multiple [pi]-conjugated rings that would cause steric hindrance are not allowed to form amorphous materials, but instead, interactions that lead to crystalline packing are induced by control of ring arrangements.

Looking over the academic field of natural sciences, structural studies of polymers and macromolecules have unusual characteristics compared with other disciplines. At the cutting edge in the real world, the crystallization of polyethylene [1] and polypropylene [2] has been intensively investigated [3, 4]. Yet, if everyone specializing in organic synthesis were asked, "Is benzene or alcohol the subject of research now?," they would not answer "Yes." However, crystallization techniques [5, 6] of polymers can turn familiar materials into the functional materials of dreams. A representative example in recent years is "polypropylene harder than iron" [7]. Plastics showing strengths several times that of iron have been produced by careful examination of crystallization conditions (nano-oriented crystallization[8]].

The cornerstones of such occurrences in physical properties are the conformation [9], orientation [10], and arrangement [11, 12] of polymer chains. In the second half of the 1990s, the observation of one molecular chain was first achieved, in 3 days, owing to the formation of Langmuir-Blodgett (LB) films [13-15] and the use of high-resolution atomic force microscopy (AFM) technology [16]. Although there is a difference between two- and three-dimensions, it was valuable report that lamella crystals [17-19], with descriptions like those in classical textbooks, were first visualized. At the same time, the appearance of "polymerchain moving" under high temperature/high humidity conditions was also captured [20]. This "motion" of polymer chains is also shown in previous reports [21, 22], in that a crystal-lattice-formed polymer chain containing a bulky and planar 7t-conjugated ring can undergo a drastic change of arrangement and further high-density packing by the induction of interactions. In addition, there is a previous report [23] that an aramid [24] in which the hydrogen-bonding site is substituted with an alkyl side-chain among "aromatic polyamides" [25, 26] with bulky and planar [pi]-conjugated functional groups can systematically change the crystal structure depending on the side-chain lengths.

This study is based on the fact that the aramid skeleton, which we recognize as being highly crystalline here, is amorphous at any segment length, even if a flexible segment is introduced. In other words, the occurrence of side-chains must be large in order to attain crystalline packing of the main chain. However, is the aramid skeleton impossible to pack without side-chains or hydrogen-bonding sites in this case? And, as a result of active utilization of several crystallization techniques, can an effective discrimination method for "whether crystalline packing is possible or not in such an amorphous polymer" be proposed?

In this study, a novel aromatic polyamide is synthesized, in which 4-(N-methylamino)benzoic acid and terephthalic acid chloride were hard segmented and a polymer of poly(propylene glycol)bis(2-aminopropyl ether) was connected as a soft segment [27, 28]. These amorphous solid structures were evaluated and spread at the air/water interface to investigate the presence or absence of packing ability. It is considered that multiple hydrophobic aromatic rings play the role of hydrophobic moieties, even if there is no alkyl long-chain moiety, which is a particularly clear hydrophobic group. It is expected that dense packing will be caused by interaction induction between [pi]-conjugated rings arranged in the same plane. In addition, if packing in two dimensions could be confirmed, isothermal crystallization was attempted after it was judged that the polymer had packing abilities in three dimensions. For judgment of the crystallization temperature, only the properties of the oligomer in the hard segment, which is the main part of the structure formation, were evaluated and utilized. The properties of the polymer itself, which has poor thermal behavior, were not evaluated (Fig. 1). For the obtained structure, a precise packing analysis was performed by reciprocal lattice analysis.

EXPERIMENTAL

Synthesis of Block Copolymers of Aromatic Polyamides

Polypropylene glycol)bis(2-aminopropyl ether)s (abbreviated as PP[O.sub.y]. Sigma-Aldrich, y: [M.sub.n]=2,000 or 4,000) (Sch. 1) is introduced as a soft segment with a several molecular weights to one terminal-end of the "hard segment," in which the number of 4-(n-methylamino)benzoic acid (abbreviated as MAB, Wako Pure Chemical Industries, Ltd.,) units (Table 1) extending from both terminal-ends of the central terephthalic group is indicated by the letter "m." The synthesis is progressed by repeating the cycle of introducing MAB to both ends of the growing chain the required number of times and finally introducing the soft segment at one end of the obtained hard segment. The hard-segment length was varied from 11 to 21 units, and the PPO soft-segment length was randomly changed with molecular weights of 2,000 and 4,000.

Evaluation of the Crystal Structure and Packing

In order to evaluate the crystal structure, packing mode, and crystallite size of the aromatic polyamide block copolymers, wide-angle X-ray diffraction (WAXD) was used. The diffractometer (Rint-Ultima III diffractometer, Rigaku Co. Ltd.) was operated at 40 kV and 40 raA to generate Cu K[alpha] radiation ([lambda] = 0.1542 nm).

Examination of Thermal Behavior Relative to Phase Transition

The thermal degradation temperature of the block copolymers of aromatic polyamides was determined by thermogravimetric analysis (TG, Sil TG-6200 instrument with an EXSTAR6000 station; heating rate; 10[degrees]C x [min.sup.-1]). A plot of thermal degradation temperature versus length of the hard segment is shown in Supporting Information, Fig. S1a. From the results, a 250[degrees]C decomposition temperature and nondependency of the hard-segment length can be seen. The thermal properties of the aromatic polyamide block copolymers were examined by differential scanning calorimetry (DSC) by using a DSC-6200 instrument with an EXSTAR6000 station (Seiko Instruments Inc.) in the range of 25-240[degrees]C, at a heating rate of 10[degrees]C x [min.sup.-1]. In each DSC run, the sample (approximately 3.0 mg) was heated. From DSC thermograms of samples used in this study, phasetransition behavior was not confirmed, except for a glass transition at extremely low temperature (Supporting Information, Fig. Sib).

Estimation of the Long Periods of Lamellae

To estimate the long periods of lamellae of the aromatic polyamide block copolymers, small-angle X-ray scattering (SAXS) was used [29, 30]. The diffractometer (Nano-viewer, Rigaku Co. Ltd.) was operated at 40 kV and 30 mA to generate Cu K[alpha] radiation ([lambda] = 0.1542 nm).

Formation of Monolayers on a Water Surface and Transferal to the Solid Substrate

Monolayers of block copolymers of aromatic polyamides were formed by spreading a chloroform solution (ca. 1.0 X [10.sup.-4] M) on ultra-pure water (18.2 M[OMEGA] x cm). After evaporation of the chloroform for 30 min, surface-pressure-area ([pi]-A) isotherms were recorded at a compression speed of 0.08 mm x [s.sup.-] [1]. The temperature of the subphase was maintained at a constant value of 15[degrees]C by circulating thermostatically controlled water around the trough. Measurements of the monolayer properties and LB film transfer were carried out with a USI-3-22 Teflon-coated LB trough (USI Instruments). The monolayers were transferred onto mica (sample for AFM, 1 layer), glass substrates (samples for out-of plane and in-plane X-ray diffraction (XRD), 20 layers), and Ca[F.sub.2] (sample for infrared (IR) spectroscopy, 40 layers), with a ferric stearate monolayer (XRD) or 5 layers of cadmium stearate (IR) as hydrophobic underlayers, at 15[degrees]C using the LB method.

Surface Morphology and Molecular Arrangement in Organized Films

The surface morphology of the transferred monomolecular layers was observed by using a scanning probe microscope (AFM Dynamic Force Mode, Seiko Instruments, SPA300 with a SPI-3800 probe station) and microfabricated rectangular Si cantilevers with integrated rectangular tips; a spring constant of 1.4 N x [m.sup.-1] was applied in this process. The long spacing of the layer structures in multilayers transferred onto glass was measured by using an out-of-plane X-ray diffractometer (Rigaku, Rint-Ultima III; Cu K[alpha] radiation, 40 kV, 40 mA) equipped with a graphite monochromator. The in-plane spacing of the two-dimensional lattice of the films was determined by using an X-ray diffractometer with different geometrical arrangements [31, 32] (Bruker AXS, MXP-BX; Cu K[alpha] radiation, 40 kV, 40 mA, an instrument especially made to order) that was equipped with a parabolic graded multilayer mirror. X-rays were incident at an angle of 0.2[degrees] and the films were slow-scanned at a speed of 0.05[degrees]/80 s. Polarized IR measurement was performed by using a TENSOR II FT-IR spectrometer (Bruker) with wire grid polarizer.

RESULTS AND DISCUSSION

Figure 2a shows the 3D and chemical structure of the block copolymers of aromatic polyamides used in this study. Samples with [MAB.sub.5-5]-b-[PPO.sub.2000], [MAB.sub.6-6]-b-[PPO.sub.2000], [MAB.sub.7-7]-b-[PPO.sub.4000], [MAB.sub.8-8]-b-[PPO.sub.2000], and [MAB.sub.10-10]-b-[PPO.sub.2000] as abbreviations were adopted as target species. The macroscopic appearance of these samples is a solid with transparency (Fig. 2b). The WAXD profiles of these polyamides are shown in Fig. 2c. Almost all polyamides showed only an amorphous halo. As illustrated in Fig. 2d, these aromatic polyamides form a completely amorphous solid aggregated structure, irrespective of the two segment lengths and their balance. As mentioned above, it was previously reported that aromatic polyamides with an alkyl chain as the side-chain systematically formed crystalline polymers with dependence on the chain length [23, 25]. In that case, the hydrogen atom of the amino group, which was originally the hydrogen-bonding site of the polyamide, was substituted with the alkyl group. When this side-chain moiety was a methyl group, monoclinic packing occurred. If the number of carbon atoms in the side-chain increased, the packing transitioned to the orthorhombic system. In addition, when the carbon number was 7 or more, the structure became amorphous. Furthermore, if the number of carbon atoms in the side-chain increased to 17, a side-chain crystal was formed, and a two-dimensional hexagonal system was indicated. Based on those results, it would not be unnatural if the newly synthesized aromatic polyamides showed high crystallinity. However, even if such a structural unit is introduced in the hard segment, crystallization might be suppressed because a flexible and highly mobile soft segment is simultaneously introduced.

As will be described later, a slight crystalline reflection was confirmed for [MAB.sub.5-5]-b-[PPO.sub.2000] in the WAXD profile. However, as shown in Supporting Information, Fig. Sib, no melting/ crystallization peaks were confirmed in the DSC thermogram, which indicates that the structure is nearly amorphous. If materials with both a highly crystalline hard segment and a flexible soft segment had been made, utilization as ionomers [33], phase-separated materials [34], etc. may have been possible. But, in reality, transparent completely amorphous substances were produced. One of the main reasons is that it is not possible to induce strong interactions between hard segments that are superior to the mobility of the soft segment.

However, it may be premature to judge that such a compound does not have any crystallization ability. In the history of crystallization studies of polymers, there are many examples in which the amorphous compound undergoes crystalline transition with refinement of the crystallization temperature and time [35-37]. On the other hand, the evaluation of crystallization ability tends to require an extremely long time and much labor. In some cases, it may take several days to induce spontaneous crystallization [38], and the crystallization temperature needs to be examined in detail in the range from room temperature to the thermal decomposition temperature or less. As a result of long-term in-depth evaluation, there is also the possibility that the corresponding compound does not have any crystallization ability at all [39]. The development of a way to easily judge whether or not the object compound has crystallization ability would be useful. In addition, even when no thermal behavior at all, including a glass transition in the high-temperature region, is observed, like in this study, a criterion for determining the optimum crystallization temperature is required. In this study, for these two points, the "method of a two-dimensional molecular film, regardless of the amphiphilicity of corresponding polymers" and the "evaluation of thermal behavior only in the main part of the structure" have been proposed [40].

Figure 3a shows [pi]-A isotherms of monolayers on the water surface and AFM images of transferred films on solids for block copolymers of aromatic polyamides. There are two features of the isotherms. All polymers form an expanded monolayer that is extremely difficult to condense and indicate a low collapsed surface pressure. It is difficult to arrange the polymer neatly because it has many bulky aromatic rings in the molecular structure. In addition, because it does not have a clear hydrophobic group, it has poor stability on the water surface and tends to collapse to a monolayer immediately. As a monolayer-forming substance on the water surface, nonamphiphilic compounds with such bulky rigid chains are not suitable. However, in this case, the next step is important in evaluating the crystalline packing capacity. This is the transfer process onto a solid substrate. Now, the polymer is in a state in which the abundant [pi]-conjugated system is capable of inducing interactions and a small amounts of hydrogen-bonding sites are arranged in the same two-dimensional plane. When the polymer is transferred onto a solid substrate, interactions between molecular chains are induced and rearrangement may occur. As a result, if crystalline packing occurs, it can be judged that this polymer will have crystallization potential. First, in the phase before collapse, the monolayer was transferred onto a solid substrate and its morphology was observed with AFM. The criterion for determining the phase before collapse is the point before the increase of inclination of the isothermal curve where the gradient becomes continuously steep. The point at which the slope of the isotherm increases corresponds to the collapsed surface pressure [41]. [MAB.sub.10-10]-b-[PPO.sub.2000]) is shown as a typical example. Although it should be noted that it was a monolayer with poor condensability at the air/water interface, it formed a homogeneous film surface at the mesoscopic scale. Incidentally, there is a simple means to evaluate the mobility at the interface for molecules that are easy to rearrange during transfer. Though too often not done, it involves transfer and observation of the collapsed film. If a drastic form change occurs after the process of monomolecular disintegration, it will be evidence for the cooperative phenomenon of high molecular mobility. In this case, almost all of the collapsed monolayers caused a transition to a single particle layer, as shown in the [MAB.sub.8-8]-b-[PPO.sub.2000] film in Fig. 3a. When this particle film is laminated in layers, the XRD layer spacing is also confirmed and extremely homogeneous height information is exhibited [42, 43]. In either result, there is a high possibility that rearrangement of the expanded monolayer-forming polymers occurs at the time of transfer.

Clear evidence of the presence of packing ability and rearrangement during transferal [44] of the subject polyamides is shown in the in-plane XRD results of the multilayers. Figure 3b shows in-plane XRD profiles of multilayers of block copolymers of aromatic polyamides. An in-plane period [45] of 4.1--4.2 [Angstrom] clearly appears in all five polyamide multilayers evaluated at this time. These were compounds that showed only amorphous scattering in the solid state. In addition, an expanded film was also formed at the air/water interface. However, the potential packing ability among the abundant [pi]-electron systems possessed by the aromatic rings can be easily predicted. Also, this hard segment is considered to be a unit with crystallization ability according to previous reports [23, 25]. It is presumed to be the packing distance between the conjugated ring chains [46], although this distance is slightly wider than is general (Fig. 3c). Therefore, both edge-on and end-on conformations are conceivable, but the end-on conformation is stronger as the conclusion. Although this point deviates from the main objective of this paper, it is introduced below because of interesting results.

Figure 4a shows the out-of-plane XRD profiles of the LB multilayers of block copolymers of aromatic polyamides. A clear (001) long spacing is observed in almost all polyamide multilayers. A comparison of the hard-segment size with the calculated [d.sub.001] value shows that the hard segment of these polyamides is end-on conformation. This is because the period is too long to be the edge-on conformation. On the other hand, it is very interesting that the long period values of the five kinds of multilayers are almost the same. The unit length of the hard segment is different. As a supplementary experiment, polarized

IR measurements were performed on these multilayers and the tilted angle of each hard-segment unit with respect to the surface normal was calculated. The result shown in Supporting Information, Fig. S2 was obtained; it was found that the tilted angle varied linearly and continuously with respect to the hard-segment length. A model diagram is shown in Fig. 4b. Here, it is assumed that the soft segment has spread on the water surface as a hydrophilic group at the air/water interface, and it is also assumed that the long-segment value is not influenced even in the multilayers. In the case of [MAB.sub.7-7]-b-[PPO.sub.4000], the soft segment is doubled in length/themultilayers. In the case of [MAB.sub.7-7]-b-[PPO.sub.4000], the soft segment is doubled in length/molecular weight, but this is based on the fact that it does not deviate from the tendency for the same long-spacing value. In addition, the [D.sub.001] crystallite size calculated from the Scherrer equation [47] was also constant, regardless of the segment length, and showed a crystallite diameter of less than about 100 [Angstrom] (Fig. 4c). Presumably, there is a stability of energy minimum at a c-axis length of about 5 nm. In the lamella formation in crystalline polymers, as well as the phenomenon that the molecular chain is always folded at almost 100 [Angstrom], it is difficult to conclude clear reasons. However, it is the result of the structure formation in a very interesting organization.

Based on the investigations so far, it was clearly shown that the aromatic polyamide block copolymers used in this study have latent crystalline packing capacity. Perhaps, by examining the crystallization temperature and time, high density packing could be achieved [48, 49]. However, as shown in Supporting Information, Fig. Sib, it is difficult to determine the crystallization temperature because this is a group of compounds for which characteristic thermal behavior is not confirmed. How can we know the way to effectively promote spontaneous crystallization? Herein, we reconsider the result of the examination of the two-dimensional film. Rearrangement behavior at the interface of these polyamides is not a coincidence. The [pi]-conjugated system that induces the interaction and the hard segment retaining a slight hydrogen-bonding site dominated the formation of the structure. That is to say, in this aromatic polyamide, only the hard segment plays a role in arranged packing. In other words, it is expected that judgment of crystallization conditions will be easier by evaluating the thermal behavior of the hard segment alone and completely eliminating the influence of the soft and highly flexible soft segment. Therefore, in the synthesis process, the hard-segment oligomer (Fig. 5a) was taken out before introduction of the soft segment and thermal behavior evaluation was carried out with DSC measurements.

Figure 5b shows the DSC thermograms of oligomers with different segment lengths. All amide oligomers clearly showed a glass transition in a range from 150 to 200[degrees]C. It is characteristic of this compound that it shows similar behavior regardless of the segment length (Figs. 4 and 5c). Therefore, it was concluded that the temperature conditions that easily induce the structural transition of the hard segment are within this range. Isothermal crystallization was performed on the hot stage at 190[degrees]C for 24 h (Fig. 5d). Figure 6a and b are comparisons of WAXD profiles of aromatic polyamide block copolymers before and after isothermal crystallization. At first glance, a clear change has occurred. The completely amorphous polyamides from [MAB.sub.6-6]-b-[PPO.sub.2000] to [MAB.sub.10-10]-b-[PPO.sub.2000] achieve three-dimensional crystallization for the first time, and high-intensity/ sharp diffraction peaks with a predictable increase in crystallinity at [MAB.sub.5-5]-b-[PPO.sub.2000] are confirmed. Figure 6c shows the DSC curves after isothermal crystallization. As is apparent from a comparison with Supporting Information, Fig. Sib, a clear melting peak is confirmed in the region above 200[degrees]C, and a phase transition from a solid to a melt is confirmed. The results of a reciprocal lattice analysis on the peaks of the WAXD profiles in Fig. 6b by indexing based on previous reports and the corresponding structural model are shown in Fig. 6d. The analyzed results were packing of a monoclinic system (a = 4.85 [Angstrom], b = 6.47 [Angstrom], c = 16.03 [Angstrom], [alpha] = [gamma] = 90[degrees], [beta] = 117.9[degrees]). This is similar to the structure of the aromatic polyamide with a methylamino group previously reported. Moreover, it was inferred from estimating from the lattice spacing in the ab plane that the structure is not packed by a [pi]-[pi] stacking, as in two-dimensional films, but by the slight remaining hydrogen bonding between --NH and O=C--groups and by van der Waals interactions. Incidentally, although an analysis of the higher order structure by SAXS is shown in Fig.7a, it was inferred that the polyamides did not exhibit a lamellar period and formed extended chain crystals (ECC) like those of polytetrafluoroethylene [50]. In addition, the transparent appearance changes to opaque (Fig. 7b), making it visible that this is a crystalline material. Also, after deconvolution of each crystalline peak, the dependence of the hard-segment length of the crystallite size obtained from the (100) reflection was plotted (Fig. 7c). Again, the obtained crystallite size of 110 [Angstrom] was almost constant, regardless of the segment length.

Figure 8 summarizes the above discussion. This study considers the amorphous nature of block copolymers of aromatic polyamides that are expected to be crystalline packed for their molecular structure. The presence or absence of latent packing ability based on making full use of crystallization technology can be judged by the method of interfacial films, which arranges the functional parts in the same plane, even for a molecule that is not amphipathic. Then, if the functional part is found to dominate the formation of the structure, a way to control the physical properties of the objective polymers as a whole is developed by evaluating the properties of the unit selectively. In this system, [pi]-[pi] interactions between conjugated rings are induced in the two-dimensional film, resulting in high-density packing. Based on the packing ability proved here, only the hard segment, which is responsible for the structure formation, was taken out and the thermal behavior was evaluated. Furthermore, based on the isothermal crystallization conditions obtained from this process, three-dimensional crystallization was achieved and the monoclinic packing from partial hydrogen bonds was analyzed. Structural control of polymers was achieved by intermolecular interactions. Structure formation leads to control of physical properties/functionality, and materials with excellent performance are produced. Although the method of interfacial molecular films and isothermal crystallization are classical techniques, it can be said that the possibility of polymer nanostructure control widens infinitely by making full use of these with the wisdom of recent years.

CONCLUSIONS

Three-dimensional crystalline formation of aromatic polyamide block copolymers with a high tendency to form amorphous materials has been achieved by the induction of intermolecular interactions. Aromatic polyamides with a hydrogen-bonding part that is mostly substituted easily form amorphous materials because of steric hindrance and weak intermolecular interactions. These aromatic polyamide block copolymers with hard and soft segments were completely amorphous, regardless of the lengths of each unit. Independently of the presence or absence of obvious hydrophobic parts like a long hydrocarbon chain, the aromatic rings arranged in the same plane could be stacked by [pi]-[pi] interactions by the method of organized molecular films. Layer spacing in the multilayers of the aromatic polyamides was not dependent on the length of the hard and soft segments and always indicated a constant value. Isothermal crystallization was performed for block copolymers of aromatic polyamides at the temperature of glass transition of only the hard segment, which played a dominant role in structure formation. After isothermal crystallization for 1 day, these polyamides clearly crystallized, regardless of segment length. The occurrence of a monoclinic packing and interactions between the slight remaining hydrogen-bonding parts was suggested from a reciprocal lattice analysis. The obtained crystals had monoclinic packing, formed extended chain crystals, and were opaque. In this study, we have presented a method for screening the crystallization ability of amorphous polymers and a method for determining the optimum crystallization temperatures.

ACKNOWLEDGMENTS

The authors greatly appreciate The Ministry of Education, Culture, Sports, Science and Technology (MEXT), for a Grant-in-Aid for Scientific Research (C, 25410219 (A. F.)). Finally, A. F. offer my heartfelt condolence to my mentor Professor Hiroo Nakahara, Saitama University, who died on December 6, 2016.

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Yusaku Shidara, (1) Takeru Yunoki, (2) Shuntaro Miura, (1) Yuji Shibasaki, (3,4) Atsuhiro Fujimori (iD) (1)

(1) Graduate School of Science and Engineering, Faculty of Engineering, Saitama University, 255 Shimo-okubo, Sakura-ku, Saitama, 338-8570, Japan

(2) Department of Functional Materials Science, Faculty of Engineering, Saitama University, 255 Shimo-okubo, Sakura-ku, Saitama, 338-8570, Japan

(3) Department of Chemistry, Faculty of Science & Engineering, Iwate University, 4-3-5 Ueda, Morioka, Iwate, 020-8552, Japan

(4) Department of Biological Sciences, Faculty of Science & Engineering, Iwate University, 4-3-5 Ueda, Morioka, Iwate, 020-8552, Japan

Additional Supporting Information may be found in the online version of this article.

Correspondence to: A. Fujimori; e-mail address: fujimori@fms.saitama-u.ac.jp Contract grant sponsor: The Ministry of Education, Culture, Sports, Science and Technology (MEXT); contract grant sponsor: Grant-in-Aid for Scientific Research; contract grant number: C, 25410219 (A. F.).

DOI 10.1002/pen.24812

Published online in Wiley Online Library (wileyonlinelibrary.com).

Caption: SCHEME 1. Condensation reaction for the synthesis of block copolymers of aromatic polyamides.

Caption: FIG. 1. Schematic illustration of the research strategy and the actual progression of this study. [Color figure can be viewed at wileyonlinelibrary.com]

Caption: FIG. 2. (a) 3D and chemical structure of the block copolymer of aromatic polyamides used in this study, (b) Photograph showing the appearance of the sample texture (amorphous state), (c) WAXD profiles of polyamide derivatives ([MAB.sub.6-6]-b-[PPO.sub.2000], [MAB.sub.7-7]-b-[PPO.sub.4000], [MAB.sub.8-8]-b-[PPO.sub.2000], and [MAB.sub.10-10]-b-[PPO.sub.2000]). (d) Simple illustrations of the structural balance of the samples. [Color figure can be viewed at wileyonlinelibrary.com]

Caption: FIG. 3. (a) [pi]-A isotherms of monolayers of block copolymers of aromatic polyamides on a water surface and AFM images of transferred films with schematic illustrations, (b) In-plane XRD profiles of multilayers of block copolymers of aromatic polyamides, (c) Model diagram of packing for block copolymers of aromatic polyamides. [Color figure can be viewed at wileyonlinelibrary.com]

Caption: FIG. 4. (a) Out-of-plane XRD profiles of the LB multilayers of block copolymers of aromatic polyamides, (b) Schematic illustrations of layer structure and tilted angles of the hard segment of block copolymers of aromatic polyamides. (c) Plot of hard-segment length in multilayers versus crystallite sizes calculated by the Scherrer equation. [Color figure can be viewed at wileyonlinelibrary.com]

Caption: FIG. 5. (a) Chemical structure of MAB oligomers used in this study, (b) DSC thermograms of MAB oligomers (m = 5-10) with schematic models, (c) Schematic illustration of the experimental procedure for isothermal crystallization. [Color figure can be viewed at wileyonlinelibrary.com]

Caption: FIG. 6. WAXD profiles of block copolymers of aromatic polyamides (a) before and (b) after isothermal crystallization. (c) DSC thermograms of block copolymers of aromatic polyamides after isothermal crystallization, (d) Reciprocal lattice analysis of WAXD data of block copolymers of aromatic polyamides and the resultant packing model with lattice constant. [Color figure can be viewed at wileyonlinelibrary.com]

Caption: FIG. 7. (a) Typical example of the SAXS pattern and profile of block copolymers of aromatic polyamides after isothermal crystallization in bulk, with a schematic illustration of the ECC model inferred by this analysis, (b) Photograph of the appearance of the sample texture after isothermal crystallization (crystalline state), (c) Plot of hard-segment length versus crystallite sizes calculated by the Scherrer Equation in the bulk state after isothermal crystallization. [Color figure can be viewed at wileyonlinelibrary.com]

Caption: FIG. 8. Schematic illustration of model diagrams for the structure formation of block copolymers of aromatic poly. amides in two and three dimensions. [Color figure can be viewed at wileyonlinelibrary.com]
TABLE 1. Monomers and raw materials used in this study.

Monomer and
raw materials                Chemical structure           Abbrev.

p-Methyl aminobenzoic acid   [formula not reproducible]   MAB

Polypropylene oxide                                       PPO
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Author:Shidara, Yusaku; Yunoki, Takeru; Miura, Shuntaro; Shibasaki, Yuji; Fujimori, Atsuhiro
Publication:Polymer Engineering and Science
Article Type:Report
Date:Nov 1, 2018
Words:5669
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