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Subnanoporous Highly Oxygen Permselective Membranes from Poly(conjugated hyperbranched macromonomer)s Synthesized by One-Pot Simultaneous Two-Mode Homopolymerization of 1,3Bis(silyl)phenylacetylene Using a Single Rh Catalytic System: Control of Their Structures and Permselectivities Jianjun Wang,† Jun Li,‡ Toshiki Aoki,*,†,§ Takashi Kaneko,§ Masahiro Teraguchi,§ Zhichun Shi,‡ and Hongge Jia† †

College of Materials Science and Engineering and ‡College of Chemistry and Chemical Engineering, Qiqihar University, Wenhua Street 42, Qiqihar, Heilongjiang 161006, China § Department of Chemistry and Chemical Engineering, Graduate School of Science and Technology, Niigata University, Ikarashi 2-8050, Nishi-ku, Niigata 950-2181, Japan S Supporting Information *

ABSTRACT: Novel well-defined complex polymers, polymers of acetylenetype macromonomers having silylene−vinylene−phenylene−ethynylene hyperbranches, investigated as a new class of subnanoporous oxygen permselective membrane materials, were synthesized very easily by one-pot simultaneous twomode homopolymerization of a single monomer with a single catalyst. For this “simultaneous polymerization” we synthesized AB2-type monomers (1,3bis(dimethylsilyl)phenylacetylenes) containing one terminal triple bond and two Si−H groups. The resulting poly(hyperbranched macromonomer)s had high molecular weights, low densities, high solubility, and good self-membrane forming ability. They had higher oxygen permselectivities (α = PO2/PN2) than any other reported polymers having similar oxygen permeabilities (PO2). These excellent polymer membranes could be obtained only by the simultaneous polymerization. In the one-pot simultaneous polymerization, the two different modes of polymerizations, i.e., addition polymerization of the triple bond and polyaddition of the triple bond and two SiH groups in the single monomer, occurred simultaneously by using one catalytic system, i.e., [Rh(norbornadiene)Cl]2/various amines. The ratio of the branches (RB), i.e., the addition polymerization and the polyaddition, could be controlled by changing the amine cocatalysts. Their oxygen permselectivities could be adjusted by controlling the polymer structures including RB.

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INTRODUCTION

their permselectivities and permeabilities almost always had trade-off relationships.21−23 For example, Robeson drew upper bound lines in plots of permselectivities versus permeabilities for polymers based on experimental results in the literature.21,22 Later, carbonized membranes (CBM) or molecular-sieved membranes were reported 24−33 to show much higher permselectivities exceeding Robeson’s upper lines for organic polymers.21,22 However, they were insoluble, and therefore no detailed information on their chemical structures was obtained. Therefore, it was difficult to improve their performances and to discuss the mechanism for their permeation on the basis of their chemical structures from these materials. On the other hand, since organic polymer membranes are generally soluble, the chemical structures and molecular weights can be precisely

Gas permselective membranes are very important and useful in our lives and for society as a whole because they can purify a required gas from a mixture of gases or can remove contaminants by a simple energy-saving process. For example, oxygen can be enriched from air and carbon dioxide can be removed from polluted air.1−20 Materials for gas permselective membranes should generally possess the following four properties: (1) a self-membrane forming ability that produces thin dense membranes with good mechanical strength and durability (this is the most important requirement); (2) a high gas permselectivity (for example, oxygen permselectivity, α = PO2/PN2); (3) a high gas permeability (for example, oxygen permeability, PO2); (4) the ability to control and improve their performances (1, 2, and 3) by changing their molecular structures. Although many gas permselective polymer membranes were reported because they provided good self-standing membranes, © XXXX American Chemical Society

Received: July 12, 2017 Revised: August 23, 2017

A

DOI: 10.1021/acs.macromol.7b01458 Macromolecules XXXX, XXX, XXX−XXX

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Macromolecules Table 1. Comparison of Properties of Subnanoporous Materials for Gas Separation Membranes materialsa

Conb

Stab

Mb

Sob

Perb

Desb

Synb

organic polymers CBM PI and PIM COF CMP and HCP dendrimer poly(dendron) HBP poly(HBM) (this study)

−− − + +++ ++ +++ ++ ++ ++

−− ++ − +++ ++ + + + +

+++ + ++ −− − −− + ++ +++

++ −− + −− −− + + ++ ++

+ ++++ +++ − − − ++ + +++

++ −− ++ + + +++ ++ ++ ++

++ + + + + −− − ++ ++

a

CBM: carbonized membranes; PI: polyimides; PIM: polymers of intrinsic microporosity; COF: covalent organic frameworks; CMP: conjugated microporous polymers; HCP: hyper-cross-linked polymers; HBP: hyperbranched polymers; HBM: hyperbranched macromonomer. bCon: Control of subnanopores; Sta: stability of subnanopores; M: membrane forming ability; So: solubility; Per: permselectivity; Des: ease of molecular design; Syn: ease of synthesis.

Chart 1. Chemical Structures of Silicon-Containing Phenylacetylene Monomers (1−7) and Cocatalyst Amines (TEA, PEA, and I−V) in Our Studya

a 1−3: SiH-containing AB2 type phenylacetylene monomers in this study; 4: a SiH-containing AB type phenylacetylene monomer in our previous study;68 51, 52, 53, and 6: phenyleneethynylene dendron acetylene-type macromonomers in our previous study;58−60 7: trimethylsilylphenylacetylene in our previous study;69 TEA: trimethylamine; PEA: phenylethylamine.

formed mainly between their macromolecules in their membranes. Therefore, the subnanospaces were dynamic and unstable. In other words, precise control of them was not easy. Recently, some subnanoporous polymer materials have been reported such as covalent organic frameworks (COF),34−39 conjugated microporous polymers (CMP),40,41 and hypercross-linked polymers (HCP)42−44 and other cross-linked polymer networks. Although they have well-organized regular structures containing sub-nano-sized pores, they are crystalline and/or insoluble. As a result, it was difficult to fabricate dense membranes from them. Therefore, almost no applications of such polymers to gas separation membranes have been

determined by NMR and GPC. In addition, their thin dense membranes can be easily prepared from them by wet processes (solvent casting). In particular, polyimides (PI),5−10 polymers of intrinsic microporosity (PIM),11−16 and poly(substituted acetylenes)17−19 showed good solubility and very good permselective performances, and their plots were close to or above Robeson’s upper bound lines.21,22 Those polymers showing good performances as oxygen permselective membranes, such as PI5−10 and PIM,11−16 were mainly linear, cyclolinear, or ladder-like polymers. Although they contained kink structures inside their rigid macromolecules, their subnanospaces (subnanopores), where gas molecules permeate, B


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Scheme 1. Synthesis of Poly(hyperbranched macromonomer) by One-Pot Simultaneous Two-Mode Homopolymerization (S) of 3,5-Bis{(4′-dimethylsilyl)phenylethynyl}phenylacetylene (1)a

a

p = p1 + p2: the degree of polyaddition; q: the degree of addition polymerization.

reported.45 In addition, the chemical structures of COFs were limited because only limited multifunctional monomers can form insoluble crystalline polymers under thermodynamic control conditions. The precise controls of the structures of CMP and HCP were also limited because the reaction and their products could not be controlled and monitored by NMR because of their insolubility. In summary, although COF34−39 and CMP40,41 contained well-controlled subnanopores inside their planar macromolecules, they had no membrane forming ability because they were always insoluble (Table 1). On the other hand, dendrimers46−50 were thought to be promising candidates to control chemical structures more precisely and obtain controlled subnanospaces (subnanopores) which can separate gas mixtures on the basis of molecular sieving effects.51−57 However, they had no membrane-forming ability because their backbones cannot become entangled with each other. Therefore, almost no applications of dendrimers to permeation membranes have been reported. However, if we use graft copolymers with dendrons as grafts,58−60 the two problems mentioned above, i.e., no control of subnanopores in linear polymers such as PIM and no membrane forming ability of planar polymers such as COF and dendrimers, can be solved simultaneously. Therefore, we reported that poly(dendron)s58−60 synthesized by homopolymerization of phenylene−ethynylene−acetylene-type macromonomers (Chart 1, 51, and 6) showed self-membrane forming abilities and better oxygen permselectivities than conventional poly(substituted acetylene)s. However, graft copolymers produced from higher generations of the dendron macromonomers

(Chart 1, 52 and 53)58−60 did not possess a self-membrane forming ability. In addition, since this synthetic route contained many organic reaction steps such as protection and deprotection steps, it was unsuitable for practical use. On the other hand, hyperbranched polymers (HBP)61−67 are synthesized easily by polymerization, and the syntheses are much easier than those of dendrimers, although the regularity of the molecular structure is lower. Therefore, we planned synthesis of poly(hyperbranched macromonomer)s (poly(HBM)) instead of poly(dendron macromonomer)s. All the subnanoporous materials discussed above are compared and summarized in Table 1. In the case of synthesis of the poly(HBM)s by homopolymerization of the hyperbranched macromonomer, the molecular weights of the resulting polymers were thought to be generally low due to their bulkiness (Scheme 2, (P) → (A)). Further, if the poly(HBM)s are synthesized from poly(substituted acetylene)s having SiH groups at the pendant groups, it seemed that the branches cannot be propagated perfectly due to the steric hindrance between the pendant groups (Scheme 2, (A) → (P)). Therefore, we thought that these two conventional two-step methods were not suitable for obtaining poly(HBM)s with high molecular weights and welldeveloped branches. Therefore, in this study, we report that we have found a new one-step synthesis method for poly(HBM). In this polymerization, poly(hyperbranched macromonomer)s can be produced by one-pot polymerization from one AB2-type monomer (1−3 in Chart 1) and by both of the two modes of polymerization, i.e., addition polymerization and polyaddition C


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Scheme 2. One-Pot Simultaneous Two-Mode Homopolymerization (S) and Two Two-Step Homopolymerization of 1−3a

a (A): addition polymerization; (P): polyaddition (hydrosilyation) polyaps(1)−polyaps(3): poly(hyperbranched macromonomer)s by S of 1−3; polya(1)−polya(3): linear homopolymers by A of 1−3; polyap(1)−polyap(3): poly(hyperbranched macromonomer)s by P of 1−3 of polya(1)− polya(3) with 1−3; polyp(1)−polyp(3): hyperbranched homopolymers (macromonomers) by P of 1−3; polypa(1)−polypa(3): poly(hyperbranched macromonomer)s by A of polyp(1)−polyp(3) (macromonomers).

occurring simultaneously. Therefore, we term it “simultaneous polymerization” (Scheme 1). We previously reported such a new polymerization of an AB-type monomer (Chart 1).68 In addition, the resulting homopolymers showed the best oxygen permselectivity (α = PO2/PN2) among the reported polymers having the same permeability (PO2). In our previous report, since the homopolymers of 1 had no self-membrane forming ability, their copolymers with 7 were used.69 In this study, in order to propose and present a new class of subnanoporous polymers having both well-controlled subnanopores and good self-membrane forming ability and to synthesize the new soluble polymers easily, the following two discoveries are reported. (1) Excellent oxygen permselectivity through membranes from new polymers of acetylene-type macromonomers having silylene−vinylene−phenylene−ethynylene hyperbranches from 1. Their oxygen permeation performances were superior to any polymers reported so far (Figure 5 and Table 6). (2) Easy synthetic method for the complicated but well-defined homopolymers by one-pot “simultaneous polymerization” of AB2-type monomers 1−3 (Chart 1 and Scheme 1). The new and well-organized complex subnanoporous polymers could be easily synthesized by this one-pot method.

they had better membrane forming abilities than dendrimers which have generally no membrane forming ability. However, poly(dendron macromonomer)s still had the two problems as described above: (1) multistep synthetic routes and low total yields and (2) poor membrane forming ability, especially for the polymers with higher generations (G). In this study to overcome the two problems, we designed and synthesized a new type of polymer, i.e., poly(hyperbranched macromonomer). In addition, we propose its new synthetic method, i.e., one-pot synthesis by “simultaneous polymerization” of two modes of polymerization of one monomer by one catalytic system. In other words, we report that we found a new complicated but well-controlled subnanoporous polymer and that the complex polymers could be easily synthesized by a onepot simple procedure. In addition, they had good oxygen permselective performance as described in section 5. Synthetic Procedure of One-Pot Simultaneous Two-Mode Homopolymerization. To begin with, we report discovery of one-pot synthesis of the new type of a polymer, poly(hyperbranched macromonomer), by simultaneous polymerization (Scheme 1) of two different modes of polymerizations, i.e., addition polymerization and polyaddition of one monomer (1 in Scheme 1) by using one catalyst, not by using the mixture of the two catalysts. Monomer 1 (Chart 1 and Scheme 1) having one terminal triple bond and two Si−H groups via an ethynylenephenylene spacer was synthesized (see Supporting Information, 2.1, Scheme S1) and polymerized with [Rh(nbd)Cl]2 as a catalyst and various amines as cocatalysts such as triethylamine (TEA) and phenylethylamine (PEA) known as a catalytic system for addition polymerization of terminal acetylenes (Chart 1, I−V). And 1 was also polymerized in polyaddition mode with RhCl(PPh3)3/NaI known as a catalyst for hydrosilylation (Scheme 2). Table 2 shows the results of polymerization of 1 together with other SiH-containing

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RESULTS AND DISCUSSION 1. One-Pot Simultaneous Polymerization of One Monomer to Poly(hyperbranched macromonomer) (Scheme 1, Figures 1−4, and Table 2). Advantages in the Synthesis of Poly(hyperbranched macromonomer) over That of Poly(dendron macromonomer). Poly(dendron macromonomer)s we reported before58−60 were valuable well-defined polymers showing better oxygen permselectivities than the corresponding linear polymers with no branches, and D


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the other two polymers, i.e., polyap(1) and polypa(1), had lower Mn values and no membrane forming abilities (Table 2). In the case of polypa(1) synthesized by homopolymerization of polyp(1) (Scheme 2), an acetylene-type macromonomer, the Mn and Mw could not become high because of the bulkiness around the acetylene group. As Figures 1d and 1e show, the conversion of the macromonomer was not high. In the case of polyap(1) which was synthesized by polyaddition of polya(1) with 1 (Scheme 2), only very small increaces in Mn and Mw were observed (Figures 1b and 1c). Only the small amount of development of the branches occurred because the bulkiness of the branches in polya(1) was already high. In summary, among the three poly(hyperbranched macromonomer)s, only polyaps(1) showed the best membrane forming ability because it had a 10 times higher Mn than the others (The detailed reason is discussed later in section 4). Therefore, it was useful for oxygen permselective membrane materials (see section 5). Evidences for the “Simultaneous Polymerization” Based on 1H NMR (Figures 2−4). In order to discuss the detailed chemical structures of the poly(hyperbranched macromonomer)s, we measured NMR spectra for all the polymers, that is, for polyaps(1), polyap(1), polypa(1), polyp(1), and polya(1). Figures 2 and 3 show 1H NMR spectra of the olefinic and aromatic region and silane (SiH) and dimethylsilyl (CH3Si) region of the polymers, respectively. Broad Peaks in the Olefin and Aromatic Region in 1H NMR (Figure 2). As shown in Figure 2, unfortunately the peaks were so broad and overlapped each other that detailed assignments were difficult for the methine peaks (δ = ca. 5.9−7.0 ppm) of the inside double bonds in the branches and the cis proton peak (δ = ca. 5.8 ppm) of the main chain of the poly(substituted acetylene) in the polymers.70 The peaks assigned to the aromatic protons (δ = ca. 6.4−7.6 ppm) were also broad and overlapped with a solvent peak. However, because peaks for aromatic protons in poly(phenylacetylene) and in the products by hydrosilylation between the triple bonds and Si−H were observed at 6.4−7.2 and 7.1−7.6 ppm, respectively (see Figure 4), the ratio of the backbone and branches could be roughly estimated. The ratios were relatively comparable to those by the following precise results based on the model reactions. Instead of broad and overlapped peaks in the olefinic and aromatic region, we decided the microstructures by silane (SiH) and dimethylsilyl (CH3Si) region in 1 H NMR (Figure 3) and confirmed them by 1H NMR of products in model reactions (Figure 4 and Scheme 3). The details are described in the following sections. Assignable Peaks in the Silane (SiH) and Dimethylsilyl (CH3Si) Region in 1H NMR (Figure 3). Although detailed and precise assignments were impossible for the peaks of the olefinic methines including the cis proton of the main chain as shown in Figure 2, fortunately peaks of silane (SiH) (δ = ca. 4.0−4.6 ppm) and dimethylsilyl (CH3Si) region (δ = ca. 0.0− 0.6 ppm) were relatively sharp, and detailed assignments were possible as follows. As model polymers for the NMR assignments of the three poly(hyperbranched macromonomer)s, i.e., for polyaps(1), polyap(1), and polypa(1), the two precursor polymers, i.e., polya(1) (Figure 3c) and polyp(1) (Figure 3e), were used. They showed clear difference in the peaks assigned to the hydrogen(SiH) and methyl (CH3Si) in the dimethylsilyl ((CH3)2SiH) groups (Figure 3). For the codes of the assignments such as Hp and MHp, see Chart 2. While the three poly(hyperbranched

phenylacetylenes (2−4 in Chart 1), dendron acetylene-type macromonomers (51, 6, 52, and 53), and trimethylsilylphenylacetylene (7) with no branch (Chart 1). Figure 1 and Figures 2 and 3 show the GPC charts and NMR spectra for the resulting polymers of 1, respectively. Role of the Cocatalyst for the Two-Mode Simultaneous Polymerization. When RhCl(PPh3)3/NaI known as a catalyst for hydrosilylation was used as a catalyst for the polymerization, 1 was polymerized only by hydrosilylation between the terminal triple bonds and the two Si−H groups in polyaddition mode ((P) in Scheme 2; P: polyaddition) to yield a hyperbranched acetylene-type macromonomer (polyp(1) (Mn = 3.0 × 103) in Scheme 2, no. 7 in Table 2 and Figures 1e and 3e) because 1 was an AB2-type monomer for polyaddition.

Figure 1. GPC traces of the homopolymers from 1: (a) polyaps(1) (Table 2, no. 2), (b) polyap(1) (Table 2, no. 4), (c) polya(1) (Table 2, no. 5), (d) polypa(1) (Table 2, no. 6), (e) polyp(1) (Table 2, no. 7). For the codes, see Scheme 2. For NMR of the five polymers, see Figure 3.

When [Rh(nbd)Cl]2/PEA was used, addition polymerization at the terminal triple bond occurred ((A) in Scheme 2; A: addition polymerization) to yield polya(1) (Mn = 3.3 × 104) as shown in Scheme 2 (no. 5 in Table 2 and Figures 1c and 3c). The role of PEA was also our new finding, and we reported it only for an AB-type monomer 4 (no. 18 in Table 2).68 On the other hand, when [Rh(nbd)Cl]2/TEA, 2-amino-1butanol (I), or 1-cyclohexylethylamine (II), and so on was used as a cocatalyst (Chart 1), 1 was polymerized simultaneously both in polyaddition mode and in addition polymerization mode ((S) in Scheme 2; S: simultaneous polymerization) to yield polyaps(1) (Mn = (1.35−2.44) × 105) as shown in Table 2 (nos. 1−3, 10−13, and Figures 1a and 3a). We discuss and confirm the detailed structures of polyaps(1), i.e., poly(hyperbranched macromonomer)s and the achievement of the simultaneous polymerization based on GPC (Figure 1) and NMR (Figures 2−4) in the following sections. (Note: for the definition of p, q, and polyaps(1), polyap(1), polypa(1), polyp(1), and polya(1), see Schemes 1 and 2.) Comparison of the GPC Traces for the Three Poly(hyperbranched macromonomer)s (Figure 1). Figure 1 shows the GPC traces for the three poly(hyperbranched macromonomer)s, i.e., polyaps(1), polyap(1), and polypa(1), and their two precursor polymers, i.e., polyp(1) and polya(1). Among the three poly(hyperbranched macromonomer)s, polyaps(1) had the highest Mn and Mw, and therefore it showed the best membrane forming ability. On the other hand, E


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were observed and assigned as those for SiCH3OH, their integral values were small. For example, it was only 0.26H in polyaps(1). Therefore, their influences must be low. While the precursor polymers (polya(1) (Figure 3c) and polyp(1) (Figure 3e)) showed mainly one peak for SiCH3 (the code is M, see Chart 2) and mainly one peak for SiH (the code is H, see Chart 2), in the three poly(hyperbranched macromonomer)s (polyaps(1), polyap(1), and polypa(1)), three peaks of SiCH3 (M) and two peaks of SiH (H) were observed. Finally, we decided that the three poly(hyperbranched macromonomer)s contained the two kinds of the polymer structures produced by addition polymerization and polyaddition (Scheme 2). Therefore, in the case of polymerization of 1 by [Rh(nbd)Cl]2/TEA to yield polyaps(1), we conclude that not only addition polymerization but also polyaddition by hydrosilylation happened simultaneously; that is, the “simultaneous polymerization” occurred. In addition, since the GPC curve (Figure 1a) was unimodal, we conclude that it was poly(hyperbranched macromonomer), not a mixture of the two types of polymers, polya(1) and polyp(1). To the best of our knowledge, this is the first example of the “simultaneous polymerization” of one monomer by one initiator. Assignments of Peaks in the Olefin Region in 1H NMR for the Products of Model Reactions: Confirmation of the Simultaneous Reaction by Model Reactions (Figure 4). As described above, since detailed and precise assignments were impossible for the peaks at the olefinic region as shown in Figure 2, the following five model reactions were carried out (Scheme 3). The three of them were reactions between the triple bonds and SiHs by using three kinds of catalytic systems, i.e., RhCl(PPh3)3/NaI, [Rh(nbd)Cl]2/TEA, and [Rh(nbd)Cl]2/PEA, which were the same catalytic systems used for synthesis of polyp(1) and polyap(1), polyaps(1) and polypa(1), and polya(1), respectively (Scheme 2). The three NMR spectra for the products of the three model reactions are shown in Figure 4: (1), (3), and (4). Figure 4 also contains the two other spectra (2 and 5) for the products for the same reaction by using [Rh(nbd)Cl]2 without any amines (Figure 4, 2) and the polymer product in addition hompolymerization of trimethylsilylphenylacetylene having no SiH group (7) polymerized by [Rh(nbd)Cl]2/TEA (Figure 4, 5) as references. Since in the spectra 3, 4, and 5 a peak at 5.8 ppm assigned to the cis-proton of the main chain was observed, it was found these catalytic systems produced the poly(phenylacetylene) backnbone by addition homopolymerization. On the other hand, the spectra 1, 2, and 3 contained several peaks assigned to the hydrosilylation products at ca. 5.9−7.6 ppm. Only spectrum 3 for the product by using [Rh(nbd)Cl]2/ TEA contained the peaks assigned to the products both by addition polymerization and hydrosilylation. Therefore, it was reconfirmed that the catalytic system [Rh(nbd)Cl]2/TEA can proceed simultaneously addition polymerization of a terminal acetylene and hydrosilylation, that is, “simultaneous polymerization”. It was found that the main chain of the product by addition polymerization was cis-rich. In conclusion, synthesis of a complex polymer, poly(hyperbranched macromonomer), by one-pot simultaneous polymerization of the two different modes of polymerizations, i.e., addition polymerization and polyaddition of one monomer(1) having one terminal triple bond and two Si−H groups has been achieved by using [Rh(nbd)Cl]2/various amines such as TEA and I−V. To the best of our knowledge, the two findings

Figure 2. Olefin and aromatic region (δ = 5.5−8.0 ppm) of 1H NMR spectra of the homopolymers from 1 in CDCl3: (1) polyaps(1) (Table 2, no. 2); (2) polyap(1) (Table 2, no. 4); (3) polypa(1) (Table 2, no. 6), For the codes, see Scheme 2. For GPC of the three polymers, see Figure 1.

macromonomer)s (polyaps(1), polyap(1), and polypa(1)) had two major peaks for SiH (this code is H, see Chart 2), the precursor polymers (polya(1) and polyp(1)) and the monomer (1) had only one peak. Therefore, we assigned the one signal around 4.43 ppm, which was observed similar to those for the monomer 1 and polyp(1), as Hp (see Chart 2), and assigned the other signal around 4.28 ppm, which newly appeared after addition polymerization, as Hq (see Chart 2). These assignments were also confirmed for polyaps(4).68 Similar assignments have been carried out for the peaks around 0.6−0.0 ppm. The three peaks at 0.55−0.40, 0.40−0.22, and 0.22−0.03 ppm were assigned as Mv, MHp, and MHq, respectively (see Chart 2). It was confirmed that the ratios of the integral values for Hp/ Hq were consistent with those of MHp/MHq. Therefore, these assignments were reliable. Although the peaks at ca. 0.03 ppm F


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Macromolecules Scheme 3. Model Reactions of Dimethylsilylbenzene and Phenylacetylene by Catalyst (1)−(4) (Eq A) and Homopolymerization of 7 by Catalyst (5) (Eq B)a

a

For the codes and NMR, see Figure 4.

were the first examples. In other words, we obtained the new type of complex well-controlled subnanoporous polymer (poly(hyperbranched macromonomer)) and developed the new simultaneous polymerization method of one monomer by using one catalyst to yield the complicated polymers for the first time. In addition, the resulting poly(hyperbranched macromonomer) by the one-pot simultaneous polymerization showed the best performance for oxygen permselective subnanoporous membrane materials as described in section 5. 2. Advantages in Chemical Structures of Poly(hyperbranched macromonomer) by Simultaneous Polymerization among the Three Poly(hyperbranched macromonomer)s (Scheme 2 and Tables 2−4). Advantages of Polyaps(1) by the One-Pot “Simultaneous Polymerization” in Molecular Weights and Membrane Forming Ability among the Three Poly(hyperbranched macromonomer)s. In order to investigate advantages of the one-pot simultaneous synthetic route ((S) in Schemes 1 and 2) to the new type of polymer (poly(hyperbranched macromonomer)), we compared polyaps(1) with polyap(1) and polypa(1) having similar structures synthesized by the two 2step procedures ((A) + (P) and (P) + (A), respectively, in Scheme 2). First, self-membrane forming ability is the fundamental requirement for gas separation membrane material. To realize it, high Mw and Mn and good solubility are important. Table 2 shows the results of polymerization, that is, characteristics such as Mn’s, n’s, and membrane forming abilities (M) of the poly(hyperbranched macromonomer) prepared by the simultaneous polymerization of 1 (polyaps(1)) together with those of poly(hyperbranched macromonomer)s prepared by the two-step methods (polyap(1) and polypa(1), Scheme 2) and their two precursor polymers (polya(1) and polyp(1)). The poly(hyperbranched macromonomer)s (polyaps(1)) prepared by the simultaneous polymerization had higher Mn’s than polyap(1) and polypa(1) and completely soluble. Therefore, they were fabricated to membranes by the solvent cast method. When we carried out the polymerization in higher feed concentrations, the resulting polymers were partly insoluble and showed no membrane forming ability. Therefore, we previously used their copolymers as membrane materials.71 Polyap(1) and polypa(1) had no self-membrane forming ability, and therefore only polyaps(1) had self-membrane forming ability. Polypa(1) by addition homopolymerization of polyp(1) as a macromonomer had a lower Mn value and a low

Figure 3. Dimethylsilane (SiH and SiCH3) region (δ = 0.0−4.6 ppm) of 1H NMR spectra of the homopolymers from 1. (a) polyaps(1) (Table 2, no. 2), (b) polyap(1) (Table 2, no. 4), (c) polya(1) (Table 2, no. 5), (d) polypa(1) (Table 2, no. 6), (e) polyp(1) (Table 2, no. 7), (f) 1. For the codes, see Chart 2 and Scheme 2. For GPC of the five polymers, see Figure 1. MV: 0.55−0.40 (ppm), MHp: 0.40−0.22 (ppm), MHq: 0.22−0.03 (ppm).

G


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Table 2. One-Pot Simultaneous Two-Mode (Co)polymerization (S) and Two-Step Homopolymerization of 3,5-Bis{(4′dimethylsilyl)phenylethynyl}phenylacetylene (1) and 3,5-Bis(dimethylsilyl)phenylacetylene (2) in This Study (Nos. 1−13) Together with Related Polymers in Our Previous Study (Nos. 14−19)a no.a

no. in Table 6

polymerb

coatalystb

yieldc (%)

Mnd (×104)

Mw/Mnd

nGPCd,e

pNMR&GPCf

qNMR&GPCg

RBNMRh

Mi

1 2 3 4j 5 6k 7 8 9 10 11 12 13 14 15 16 17 18 19

1 2 3

polyaps(1) polyaps(1) polyaps(1) polyap(1) polya(1) polypa(1) polyp(1) copolyaps(1/7) copolyaps(4/7) polyaps(2) polyaps(2) polyaps(2) polyaps(2) poly(51) poly(6) poly(52) poly(53) polya(4) poly(7)

TEA I II RhCl(PPh3)3/NaI PEA TEA RhCl(PPh3)3/NaI TEA TEA I II IV V TEA TEA TEA TEA PEA TEA

76.0 65.1 71.8 62.4 87.0 94.0 90.4 76.6 95.5 87.4 34.4 35.5 29.0 83.1 67.2 26.0 0.800 84.4 98.1

24.4 23.5 13.5 5.00 3.30 1.20 0.30 18.0 3.20 2.10 0.620 1.60 0.850 250 280 280 13.0 9.10 130

2.11 2.21 2.04 4.42 3.80 3.01 1.84 4.10 5.21 4.54 1.80 2.71 2.36 1.40 1.60 2.84 2.21 2.50 1.70

529 510 293 108 74.2 26.8 19.0 430 76.6 50.0 14.8 38.2 20.4 5340 5120 1990 55.6 222 7470

390 325 184 24.2 0 19.0 19.0 49.5 7.58 34.4 8.05 21.6 13.6 0 0 0 0 0 0

139 185 109 83.9 74.2 7.71 0 381 69.0 15.6 6.74 16.6 6.78 5340 5120 1990 55.6 222 7470

2.75 1.75 1.69 0.29 0 2.47 ∞ 0.09 0.08 2.11 1.09 1.15 1.91 0 0

+++ +++ +++ − ++ − − ++ ++ + − + − ++ ++ + − ++ ++

6

4 5

8 9

7 10

0 0

a Polymerization conditions: at room temperature in toluene and [monomer]/[cocatalyst]/[Rh(nbd)Cl]2 = 250/500/1; for nos. 1−3: [monomer] = 0.010 mol/L for 12 h; for nos. 4−7, 10−19: [monomer] or [monomer + comonomer] = 0.10 mol/L for 4 h; for nos. 8 and 9: [monomer] = 0.20 mol/L for 4 h. bFor the codes, see Scheme 2 and Chart 1. cReprecipitated in methanol. dBy GPC correlating polystyrene standard with THF eluent. e nGPC = Mn,GPC/(Mw of the monomer). fpGPC&NMR = nGPC × {1 − MHq/(Mv + MHp + MHq)} = nGPC × {1 − 1/(RBNMR + 1)} = nGPC − qGPC&NMR. g qGPC&NMR = nGPC × {MHq/(Mv + MHp + MHq) }= nGPC × { 1/(RBNMR + 1)} = nGPC − pGPC&NMR. hRBNMR = (Mv + MHp)/MHq = pGPC&NMR/ qGPC&NMR, where Mv, MHp, and MHq indicate the integral values in 1H NMR; for the assignments see Chart 2. iMembrane forming ability: +++, very tough; ++, tough; +, brittle; −, poor. jPolya(1) (no. 5) was polymerized with 1 as the precursor polymer. kPolyp(1) (no. 7) was homopolymerized as the precursor polymer.

olefinic and aromatic regions in polyaps(1), p, q, and RB (= p/ q) were determined from peaks assigned to peripherical SiCH3 (M) and SiH (H) such as Hp, Hq, MHp, MHq, and Mv (Chart 2). Advantages of Polyaps(1) by the One-Pot “Simultaneous Polymerization” in Development of the Hyperbranches over Polyap(1) from Polya(1) by the Two-Step Polymerization. The poly(hyperbranched macromonomer), polyap(1) (no. 4 in Table 2), prepared by one of the two-step methods ((A) → (P) in Scheme 2) showed much lower values of RB and p than polyaps(1). In addition, it had a low Mn and n value and poor membrane forming ability. By the formation of the branches at the second step polymerization ((P) in Scheme 2), the original good membrane forming ability of polya(1) (no. 5 in Table 2) was lost. Therefore, this polymer had only less suitability for gas permselective membrane materials compared with polyaps(1). The precursor polya(1) prepared at the first step ((A) in Scheme 2) showed poor oxygen permselectivity as described above because it had no branches to enhance the permselectivity as it had been easily expected. Advantages of Polyaps(1) by the One-Pot “Simultaneous Polymerization” in Development of the Hyperbranches over Polypa(1) from Polyp(1) by the Two-Step Polymerization. Although the poly(hyperbranched macromonomer), polypa(1) (no. 6 in Table 2), which was prepared by the other ((P) → (A) in Scheme 2) of the two-step methods, showed a similar value of RB because of the very low q value (no. 6 in Table 2). Since the original polyp(1), i.e., an acetylene-type hyperbranched macromonomer (no. 7 in Table 2) had a very bulky hyperbranched group (Scheme 4I)), the homopolymerization gave only very low q at the second step polymerization, and therefore it had a very poor membrane forming ability.

conversion due to the steric hindrance and therefore had no self-membrane forming ability. Polyap(1) by polyaddition of polya(1) with 1 had no self-membrane-forming ability although polya(1) had self-membrane-forming ability. It may be because the Mn of the original main chain was not enough to maintain the self-membrane forming ability for the resulting poly(hyperbranched macromonomer)s. Because self-membraneforming ability is a fundamental requirement for gas separation membrane materials, we conclude that the simultaneous polymerization of 1 produced the best poly(hyperbranched macromonomer) and in addition it was the easiest procedure among them because of the one-pot method. Advantages of Polyaps(1) in Development of the Branches among the Three Poly(hyperbranched macromonomer)s: Definition of Characteristic Values Such as p, q, and RB (= p/q) for the Structures of Poly(hyperbranched macromonomer)s (Table 2). Second, the ratios of the branches in poly(hyperbranched macromonomer)s are important to realize polymer membranes showing higher selectivity in permeation. Here we defined and calculated some characteristic values to estimate the ratio of the branches of the resulting polymers from observed values obtained by GPC and NMR. The ratio of the branches (RB = p/q) was newly defined in this study, where p and q are the degree of polymerization for addition polymerization and polyaddition, respectively. They were determined by GPC and NMR. For the detailed definitions and calculations, see the footnotes of Table 2. With increasing RB, the parts of the hyperbranches increase. Table 2 shows characteristics of the polymers by the simultaneous polymerization of 1 and 2 and other related polymers. As explained above, because peaks of NMR were broad in the H


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characteristic values, i.e., M, Mn, q, p, and RB values (Table 3). In addition only polyaps(1) showed good membrane forming ability because of the highest Mn value. Therefore, polyaps(1) was the best among the three poly(hyperbranched macromonomer)s. The reasons why the simultaneous polymerization gave the best structures having the best balance of p and q and polyap(1) and polypa(1) had the more incomplete structures are discussed later in section 3 (Scheme 4). Estimation of E/Z Selectivity in Hydrosilylation by Model Reactions (Figure 4 and Table 4). As described above, because the NMR peaks in olefinic region of the polymers were broad, no information were obtained on the methine protons attached to the double bonds in the polymers. Therefore, to estimate the olefin structures in the polymers, these model reactions between phenylacetylene and dimethylphenylsilane (see eq A in Scheme 3) were carried out. When RhCl(PPh3)3/NaI and [Rh(nbd)Cl]2 were used, Z-rich and E-rich products were obtained, respectively (Figures 4, 1 and 2). When amines were used as cocatalysts for [Rh(nbd)Cl]2, the reaction has changed largely(Figure 4, 3 and 4). When TEA was used, both hydrosilylation and addition polymerization of the acetylene occurred similarly, and no selectivity of Z and E configuration was observed (Figure 4, 3). On the other hand, when PEA was used, no hydrosilylation occurred and only addition polymerization of the acetylene proceeded (Figure 4, 4). Judging from these results, polyp(1), polypa(1), and polyap(1) whose branch parts were synthesized by RhCl(PPh3)3/NaI may contain Zrich branches. On the other hand, polyaps(1) synthesized by [Rh(nbd)Cl]2/TEA may contain branches having both Z and E configurations. In conclusion, the hydrosilylation product of the model reaction of the simultaneous polymerization by [Rh(nbd)Cl]2/TEA had no selectivity for E and Z configurations of β products without any α product (Figure 4, 3). Because in the absence of amines, the hydrosilylation reaction by [Rh(nbd)Cl]2 gave almost E (90%) product72 (Figure 4, 2), the cocatalyst amine had big effects. Table 4 summarizes these selectivities. 3. Advantages in Chemical Structures of Poly(hyperbranched Macromonomer) over Other Related P o l y m e r s. A d v a n t a g e s o f P o ly (h y p e r b r a n c h e d macromonomer)s from Monomer 1 over Those from Monomer 2. Instead of 1, we also synthesized and polymerized monomers 2 and 3 similarly to 1 (Scheme 2 and Chart 1; for the synthesis, see the Supporting Information). The results of polymerization are shown in Table 2, nos. 10−13. Although 2 has a structure similar to 1 (Chart 1), unfortunately the resulting polymers had only low Mn and no membrane forming ability different from those of 1. The reason is not clear, but it may be caused by the higher reactivity of polyaddition (P) than that of addition polymerization (A). On the other hand, monomer 3 gave only insoluble polymers. Advantages of Poly(hyperbranched macromonomer) over Poly(dendron macromonomer). Since the highest G value for the poly(dendron)s (nos. 14−17 in Table 2)58−60 with self-membrane-forming ability was only 1.0, the poly(hyperbranched macromonomer) (no. 1 in Table 2) with selfmembrane-forming ability must have higher amount of welldeveloped branches than the poly(dendron)s. Therefore, this synthetic method was superior to that for poly(dendron) as a preparation method for a gas permselective membrane material. In addition, this method was much easier, and the resulting polymer showed better permselectivity.

Figure 4. Olefin region (δ = 5.5−7.7 ppm) of 1H NMR spectra of products of model reactions of dimethylsilylbenzene and phenylacetylene (see eq A in Scheme 3) by (1) RhCl(PPh3)3/NaI (Table 4, no. 1), (2) [Rh(NBD)Cl]2 (Table 4, no. 2), (3) [Rh(NBD)Cl]2/TEA (Table 4, no. 3), and (4) [Rh(NBD)Cl]2/PEA (Table 4, no. 4); (5) polymerization product of 7 with [Rh(NBD)Cl]2/TEA (see eq B in Scheme 3) [assignments: 7.4 and 6.0 ppm (Ha and Hb: (Z)-protons in the products of hydrosilylation); 6.9 and 6.6 ppm (Ha′ and Hb′: (E)protons in the products of hydrosilylation); 5.8 ppm (Hc: cis-proton of the main chain of the addition polymerization); for the codes, see Chart 2.

Therefore, this polymer also had only less suitability for gas permselective membrane materials compared with polyaps(1). Because polyap(1) and polypa(1) had no self-membrane forming ability, they could not be used as oxygen permselective membrane materials. In conclusion, as it can be summarized in Table 3, most of the characteristic values such as Mn, RB = p/q, and M values of polyap(1) (Figures 1b and 3b) and polypa(1) (Figures 1d and 3d) obtained by the two-step procedures were not better than those of polyaps(1) by the one-pot simultaneous method. In other words, the “simultaneous polymerization” product, polyaps(1), had the highest value at once for all the I


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Macromolecules Chart 2. Codes of assignments of protons of the poly(hyperbranched macromonomer)a

Q: Structures formed by addition polymerization; P: Structures formed by polyaddition; M: −Si(CH3)2−; MV: −CH=CH−Si(CH3)2− in P, MHp: HSi(CH3)2− in P, MHq: HSi(CH3)2− in Q. H: −HSi(CH3)2−; Hp: −HSi(CH3)2− in P, Hq: HSi(CH3)2− in Q. A: −C=CH− (main chain of polyacetylene); Ap: −C=CH− in P, Aq: −C=CH− in Q; D, L, and T: dendritic, linear, and terminal parts, respectively, in P.

a

Scheme 4. Effects of the Three Synthetic Routes [(I): (P) + (A) (Two Steps); (II): (A) + (P) (Two Steps); (III): (S) (One Step)] on the Chemical Structures of the Three Poly(hyperbranched macromonomer)sa

a

For the codes and their definitions, see Scheme 2 and the footnotes in Table 2.

Advantages of Polymers of Macromonomers Having Silylene−Vinylene−Phenylene−Ethynylene Hyperbranches over Polymers of Macromonomers Having Phenylene− Ethynylene Dendrons. Compared with the polymers having only phenylene−ethynylene units such as the dendron part of the poly(dendron)s (Chart 1, 51 and 6; nos. 14−17 in Table 2), the poly(hyperbranched macromonomers) having silylene− vinylene−phenylene−ethynylene in this study showed better

solubility and better membrane forming ability because alkyl silylene groups added some thickness to the original very planar molecular structure of phenylene−ethynylene and the groups prevented the polymers from strong stackings. In this view, the new polymer structure was better for oxygen permselective membrane materials. 4. Possible Mechanisms of One-Pot Simultaneous Polymerization of One Monomer with One Catalyst J


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Macromolecules

between the branches was less than that in homopolymerization of polyp(1) macromonomer with a high content of Z configuration. Finally polyaps(1) having both higher RB and higher Mn values could be successfully obtained (Scheme 4, III). Possible Roles of the Cocatalyst Amines and Mechanism for the Simultaneous Polymerization (Scheme 5 and Table 5). As mentioned above, RB (= p/q) values, that is, the ratio of the two kinds of polymerization, i.e., polyaddition and addition polymerization, in the simultaneous polymerization could be controlled by changing the kinds of amines (Table 2, nos. 1−3, 10−13) used as cocatalysts, which can promote addition polymerization (A) and suppress polyaddition (P) (hydrosilylation). In the presence of PEA, almost no polyaddition (P) (hydrosilylation) of 1 occurred, and only addition polymerization (A) proceeded to produce polya(1) although the Mn was not high (no. 5 in Tables 2 and 3). On the other hand, in the presence of TEA and I−V (Chart 1), addition polymerization (A) of 1 proceeded together with polyaddition (P) (hydrosilylation) to produce polyaps(1) (nos. 1−3, 10−13 in Table 2). These observations have been confirmed by the corresponding model reactions described above. The amines I− V are more bulky than PEA and less bulky than TEA. Therefore, they showed intermediate effects on the polymerization. These results are summarized in Table 5.

Table 3. Summary of Comparison of Chemical Structures among Three Poly(hyperbranched macromonomers) (Polyaps(1), Polyap(1), and Polypa(1)) with Their Precursor Polymers(Polya(1) and Polyp(1)) no.

polymera

Mb

Mn

Qc

pc

RBc

Table 2

1 2 3 4 5

polyaps(1) polyap(1) polypa(1) polya(1) polyp(1)

+++ − − ++ −

+++ ++ + ++ −

++ + − + 0

+++ + + 0 +

+++ − +++ 0 ∞

nos. 1−3 no. 4 no. 6 no. 5 no. 7

a

For the codes, see Scheme 2. bMembrane forming property. cFor the definitions, see the footnotes of Table 2.

Table 4. Summary of E/Z Selectivity in the Hydrosilylation of Silanes to Acetylenes by Different Rhodium Catalyst System72 no.

catalysta

E/Z selectivityb

E:Z ratiob

Figure 4

1 2 3 4

RhCl(PPh3)3 /NaI [Rh(NBD)Cl]2 [Rh(NBD)Cl]2/TEA [Rh(NBD)Cl]2/PEA

Z rich E rich no selectivity no hydrosilylation

2:8 9:1 5:5

1 2 3 4

a

For the abbreviations, see Chart 1. bFor the assignments, see the footnotes of Figure 4.

(Schemes 4 and 5 and Table 5). Possible Reason and Mechanism for the Formation of the Best Structure of Polyaps(1) by Simultaneous Polymerization (Scheme 4). Although the two poly(hyperbranched macromonomer)s, i.e., polyap(1) and polypa(1), were also synthesized by the twostep methods other than the simultaneous method, polyap(1) had a very low RB (= p/q) caused by the lower p, and polypa(1) had a very low q and low p (although the RB was high), and both the polymers had no membrane forming ability as described above (Tables 2 and 3). In addition, since the Z configuration of the double bonds was rich in polyp(1), the terminal acetylene at the focal point in the macromonomer (polyp(1)) prepared by RhCl(PPh3)3/NaI may be surrounded by the branches as shown in Scheme 4, I. The branches may suppress the following addition homopolymerization to give polypa(1) (Scheme 4, I). As a result, Mn (or q) of polypa(1) was very low (Figure 1d). In the case of polyaddition of polya(1) with 1 by RhCl(PPh3)3/NaI yielding polyap(1), because of the high Z configuration ratio, development of the branches can be also suppressed (Scheme 4, II)). Therefore, p of polyap(1) was not high and less than that of polyaps(1) (Figure 1b). On the other hand, polyaps(1)s had higher RB, higher Mn values and good membrane forming abilities (Tables 2 and 3 and Figure 1a). We speculated the reason why the simultaneous polymerization gave such the best poly(hyperbranched macromonomers) and drew the polymerization reaction in Scheme 4, III. At first, the macromonomer (polyp(1)) in Scheme 4, III), which had a low Mn and a more ratio of E configuration whose steric hindrance was less than Z configuration, initially formed by polyaddition (P).73 And second, random addition copolymerization (A) of the formed polyp(1) with the remaining 1 gave polypa(1) with a high Mn and higher RB value because they each can avoid the steric hindrances during polymerization. Then polyaddition (P) of the resulting polypa(1), having branches of more ratio of E configuration, with 1 proceeded smoothly because the steric hindrance

Table 5. Summary of Effects of Cocatalyst Amine on Chemical Structures of Poly(hyperbranched macromonomers) (Polyaps(1)) Synthesized by the One-Pot Simultaneous Polymerization no.

aminea

Ab

Pb

Scheme 5

Table 2

1 2 3 4

none PEA I−V TEA

− + ++ ++

+ − + ++

A B C C

nos. 5, 18 nos. 2, 3, 10−13 no. 1

a

Figure 4 2 4 3

b

For the codes, see Chart 1. For the definitions, see Scheme 2.

The difference may occur because of the following reasons. The possible mechanisms and roles of the amines are drawn in Scheme 5. Because PEA has a stronger coordination ability than TEA due to less bulkiness of primary amines, it can predominantly and strongly coordinate to Rh to form a disubstituted complex (Scheme 5B). As a result, oxidative addition of SiH, which is a key step of hydrosilylation, was suppressed because the complex was saturated. In addition, the first step of (A), substitution of Cl by 1, was strongly promoted by the coordinated PEAs. Therefore, almost no (P) happened and (A) was the major pathway (Scheme 5B). On the other hand, although in the case of absence of amines only hydrosilylation occurred and no addition polymerization proceeded (Scheme 5A and Table 5), both (A) and (P) polymerization happened simultaneously in the presence of TEA and amines I−V (Scheme 5C), since substitution of Cl by 1 was promoted by the coordinated TEA and also oxidative addition of SiH was able to occur. 5. Excellent Oxygen Permselectivity of a New Class of Subnanoporous Polymer Membranes (Figure 5 and Table 6). Novel Polymers of Acetylene-Type Macromonomer Having Silylene−Vinylene−Phenylene−Ethynylene Hyperbranches. Oxygen (PO2) and nitrogen (PN2) permeability and oxygen permselectivity (α = PO2/PN2) through the polyK


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Scheme 5. Possible Effects and Roles of the Cocatalysts (PEA and TEA) in the Catalytic System for the One-Pot Simultaneous Two-Mode Homopolymerizationa

a

In scheme A, “S” means a solvent molecule.

Figure 5. Excellent oxygen permselectivity through self-supporting membranes of polyaps(1)s (★; nos. 1−3 in Table 6) in this study together with silicon-containing poly(phenylacetylene)s (■; nos. 4−9 in Table 6) we reported before and other polymers (○; nos. 11−13 in Table 6 and others) showing the best oxygen permselectivity reported in the literature. For the numbers, see Table 6. (A) An enlarged graph and (B) a whole graph of PO2/PN2 versus PO2 plots (*Robeson’s upper bounds from refs 21 and 22).

(hyperbranched macromonomer)s (polyaps(1)s, Scheme 1) synthesized by one-pot “simultaneous polymerization” (the details of the syntheses are described in section 1) of 1 were determined by a gas chromatographic method using air as a feed gas. These results are shown in Figure 5 and Table 6 together with related data. As shown in Figure 5, some plots of polyaps(1)s (nos. 1−3, star symbols) lie above Robeson’s 1991 upper bound21 but below Robeson’s 2008 upper bound.22

However, as shown in Figure 5A, polyaps(1)s (nos. 1−3, star symbols) had actually the highest α values among all the polymers with similar PO2 values (= 50−150 barrer) reported in all the literature (nos. 11−13,74−76 open circles in Figure 5A, which are polymers showing the best α values in this PO2 region reported so far; for their chemical structures see Chart S1).77 As described in the Introduction, most of the organic polymers which lie close to or beyond Robeson’s 1991 upper bound are L


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Table 6. Excellent Oxygen Permselectivity through Self-Supporting Membranes of (Co)polyaps(1) (Nos. 1−5) in This Study Together with Our Silicon-Containing Polyphenylacetylenes (Nos. 6−10) and Polymers (Nos. 11−16) Showing the Best Oxygen Permselectivity in the Literaturea,b no.

no. in Table 2

polymersa

densityb (g/cm3)

FFVc

RBNMRd

PO2e (barrer)

PO2/PN2e

DO2f (×10−6)

DO2/DN2f

ref

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16

1 2 3 8 9 5 18 14 15 19

polyaps(1) polyaps(1) polyaps(1) copolyaps(1/7) copolyaps(4/7) polya(1) polya(4) poly(51) poly(6) poly(7) PI, A PI, B PI, C PIM, D PIM, E PIM, F

0.982 0.976 0.968

0.308 0.314 0.319

2.75 1.75 1.69 0.09 0.08 0 0

58.7 106 112 113 184 126 76.0 67.7 76.0 171 52.0 116 132 156 190 201

5.00 4.46 4.38 3.76 3.40 3.35 4.17 3.49 3.80 2.71 4.20 4.00 3.57 4.70 4.50 4.20

1.06

2.31

1.63

1.74

2.26

1.34

0.620

3.87

this study this study this study 71 71 this study 68 58−60 58−60 69 74 75 76 78 79 80

1.01 1.01

1.21

0.220

For the codes, see Chart 1, Schemes 1 and 2, and Chart S1; for the polymerization condition, see Table 2. bDetermined by a floating method (see Supporting Information, 7.1). cFFV (fractional free volume) (see Supporting Information, 7.2). dRBNMR = pGPC&NMR/qGPC&NMR = (Mv + MHp)/MHq, where Mv, MHp, and MHq indicate the integral values in 1H NMR, for the assignments, see Scheme 2 and for the definitions of pGPC&NMR and qGPC&NMR, see the footnote of Table 2. ePermeability coefficient determined by gas chromatographic method in barrer (= 10−10 cm3 (STP) cm cm−2 s−1 cmHg−1). fDiffusion coefficient determined by the time lag method in cm2 s−1. a

polyimides (PI, for example, nos. 11−13)74−76 and polymers of intrinsic microporosity (PIM, for example, nos. 14−16).78−80 In other words, these new subnanoporous polymers (polyaps(1)s) showed performances better than or comparable to PI and PIM. Therefore, we can affirm that a new class of subnanoporous polymer membrane materials, poly(hyperbranched macromonomer)s (polyaps(1)s, Scheme 1), have been successfully developed.81 Although many ring-containing planar insoluble polymers such as COF and CMP and highly cross-linked insoluble polymers such as HCP have been reported as described in the Introduction, the polyaps(1)s synthesized in this work were soluble and therefore easily fabricated to form thin dense tough membranes by the usual solvent cast method. Therefore, we propose this is a new class of valuable subnanoporous polymer materials which is suitable for gas separation membranes. Advantages in Permselectivities of the Homopoly( h y p e r b r a nc he d m a c r om o no m e r ) o v e r C o p o l y (hyperbranched macromonomer). The copolymers of 1 with 7 (copolyaps(1/7), no. 4) showed a better oxygen permselectivity than the homopolymer of 7 (poly(7), no. 10). However, it was much lower than the homoplymers of 1 (polyaps(1)s) as shown in Figure 5A. It may be because the RB (= p/q) values, i.e., the ratio of the branches, were very low (= 0.09; no.4, Table 6 and Figure 5) (for the detail of the RB, see section 2 and the footnotes of Table 2). The ratio of the 7 unit in the copolymers should have been enhanced to keep selfmembrane forming ability. A similar tendency was observed for copolyaps(4/7) (no. 4).71 Advantages in Permselectivities of the Poly(hyperbranched macromonomer) over Poly(dendron macromonomer). We previously reported poly(first generation of dendron macromonomer)s (G (generation of the dendron) = 1) (poly(51), Table 6, and Figure 5, no. 8) showed a much better α value (= 3.49) than a conventional poly(phenylacetylene) (poly(7), α = 2.71, no. 10) as described in

the Introduction. It was caused by a higher DO2/DN2 value (= 1.74) for poly(51) than that (= 1.34) for poly(7) (Table 6). Therefore, in order to enhance the DO2/DN2 value and then the α (= PO2/PN2) value more largely, the polymers of higher generation (second and third) of dendron macromonomers were synthesized. However, poly(second or third generation of dendron macromonomer)s (G = 2 and 3) had no membrane forming ability. We noticed the limit of the application of these dendron polymers to gas membrane permeation.58−60 On the other hand, in this study we obtained poly(welldeveloped hyperbranched macromonomer)s with self-membrane forming ability. Therefore, this method is also significant in this view. In fact, polyaps(1)s showed much higher α values (= 5.00−4.38) (nos. 1−3) than the corresponding poly(dendron macromonomer)s (α = 3.49 and 3.80) (poly(51) and poly(6)) (nos. 8 and 9). This was caused by a much higher DO2/DN2 value (= 2.31) for polyaps(1) than that (= 1.74) for poly(51) (Table 6). Because polyaps(1) contains welldeveloped branches, it seems to have more numbers of subnanopores which have better effects on molecular sieving. Control of the Permselectivity by Changing the Ratios of the Hyperbranches, RB (= p/q). The α values of polyaps(1)s were controlled when the poly(hyperbranched macromonomer)s (polyaps(1)s) with a different RB (= p/q) were used.82 When increasing RB values, α values increased (Table 6 and Figure S2, nos. 1−3). Since polyaps(1) with a high RB had a high ratio of branches, their higher α may be caused by molecular-sieving effects by the subnanopores formed between the hyperbranches. In fact, this was supported by the fact that the DO2/DN2 value for polyaps(1) with the highest RB value (no. 1) was very high (= 2.31, Table 6). In summary, with increasing RB values, the DO2/DN2 value and then PO2/PN2 values increased (Table 6, nos. 1−3). M


Macromolecules

■

High FFV of the Poly(hyperbranched macromonomer)s. A s s h o w n in Table 6 , t h e p o l y ( h y p e r b r a n c hed macromonomer)s had very low densities and high FFV values. T h e y were l o we r t ha n t hos e f o r p oly ( d en dr on macromonomer)s and PIM D (Table 6, nos. 8, 9, 14). This must be caused by the large numbers of subnanopores formed between the well-developed hyperbranches. This unique structure must have good effects on permselectivities. In conclusion, we have developed a new class of subnanoporous polymers showing very good performance as oxygen permselective membrane materials such as good solubility, high Mn, high α, high DO2/DN2, high FFV values, and good membrane forming ability. In addition, we found a new convenient synthetic method for the new polymers, that is, one-pot “simultaneous polymerization” (Scheme 1). The discovery of the new synthetic method and detailed structures of the resulting polymers are described in the sections 1−3.

ACKNOWLEDGMENTS Partial financial support through a Grant-in-Aid for Scientific Research (B) (No. 16H04153) from the Japan Society for the Promotion of Science and Youth Academic Backbone of the Education Department of Heilongjiang Province of China (No. 135109304) is acknowledged.

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CONCLUSIONS Novel well-controlled complex polymers, polymers of acetylene-type macromonomers having silylene−vinylene−phenylene−ethynylene hyperbranches, were synthesized very easily by a one-pot simultaneous polymerization method. In the one-pot simultaneous polymerization, two different modes of polymerizations, i.e., addition polymerization of terminal triple bonds and polyaddition of terminal triple bond and SiH in a single monomer having one terminal triple bond and two Si−H groups, occurred simultaneously by using one catalytic system, [Rh(norbornadiene)Cl]2/various amines. The resulting poly(hyperbranched macromonomer) showed high solubility, good membrane-forming ability, and higher oxygen permselectivity than any other reported polymers having a similar oxygen permeability. This is a new class of subnanoporous highly oxygen permselective membrane material. The detailed structures were estimated by NMR and GPC. In addition, the polymer structures and then their permselectivities were controlled by the ratio of the two polymerizations, i.e., the ratio of the branch (RB) which could be changed by choosing different amine cocatalysts. Because the complex structures can be determined and controlled effectively, these polymers are very suitable for the design of subnanoporous polymer membrane materials. ASSOCIATED CONTENT

S Supporting Information *

The Supporting Information is available free of charge on the ACS Publications website at DOI: 10.1021/acs.macromol.7b01458. Full experimental data and additional figures (PDF)

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REFERENCES

(1) Sanders, D. F.; Smith, Z. P.; Guo, R.; Robeson, L. M.; McGrath, J. E.; Paul, D. R.; Freeman, B. D. Energy-efficient Polymeric Gas Separation Membranes for a Sustainable Future: A Review. Polymer 2013, 54, 4729−4761. (2) Nagai, K.; Masuda, T.; Nakagawa, T.; Freeman, B. D.; Pinnau, I. Poly[1-(trimethylsilyl)-1-propyne] and Related Polymers: Synthesis, Properties and Functions. Prog. Polym. Sci. 2001, 26, 721−798. (3) Ghosal, K.; Freeman, B. D. Gas Separation using Polymer Membranes: An overview. Polym. Adv. Technol. 1994, 5, 673−697. (4) Freeman, B. D.; Pinnau, I. Separation of Gases using SolubilitySelective Polymers. Trends Polym. Sci. 1997, 5, 167−173. (5) Kanehashi, S.; Sato, S.; Nagai, K. Synthesis and Gas Permeability of Hyperbranched and Cross-Linked Polyimide Membranes. Membrane Gas Separation 2010, 1−27. (6) Liaw, D. J.; Wang, K. L.; Huang, Y. C.; Lee, K. R.; Lai, J. Y.; Ha, C. S. Advanced Polyimide Materials: Syntheses, Physical Properties and Applications. Prog. Polym. Sci. 2012, 37, 907−974. (7) Xiao, Y.; Low, B. T.; Hosseini, S. S.; Tai, S. C.; Paul, D. R. The Strategies of Molecular Architecture and Modification of PolyimideBased Membranes for CO2 Removal from Natural GasA review. Prog. Polym. Sci. 2009, 34, 561−580. (8) Stern, S. A.; Mi, Y.; Yamamoto, H.; Clair, A. K. S. Structure/ Permeability Relationships of Polyimide Membranes. Applications to the Separation of Gas Mixture. J. Polym. Sci. J. Polym. Sci., Part B: Polym. Phys. 1989, 27, 1887−1909. (9) Wind, J. D.; Paul, D. R.; Koros, W. J. Natural Gas Permeation in Polyimide Membranes. J. Membr. Sci. 2004, 228, 227−236. (10) Liu, Y.; Wang, R.; Chung, T. S. Chemical cross-linking modification of polyimide membranes for gas separation. J. Membr. Sci. 2001, 189, 231−239. (11) McKeown, N. B.; Budd, P. M. Polymers of Intrinsic Microporosity (PIMs): Organic Materials for Membrane Separations, Heterogeneous Catalysis and Hydrogen Storage. Chem. Soc. Rev. 2006, 35, 675−683. (12) McKeown, N. B.; Budd, P. M. Polymers of Intrinsic Microporosity. ISRN Mater. Sci. 2012, 2012, 150−151. (13) Zhang, J.; Kang, H.; Martin, J.; Zhang, S.; Thomas, S.; et al. The Enhancement of Chain Rigidity and Gas Transport Performance of Polymers of Intrinsic Microporosity via Intramolecular Locking of the Spiro-Carbon. Chem. Commun. 2016, 52, 6553−6556. (14) Rose, I.; Carta, M.; Malpassevans, R.; Ferrari, M. C.; Bernardo, P.; Clarizia, G.; Jansen, J. C.; McKeown, N. B. Highly Permeable Benzotriptycene-Based Polymer of Intrinsic Microporosity. ACS Macro Lett. 2015, 4, 912−915. (15) Ghanem, B. S.; Hashem, M.; Harris, K. D. M.; Msayib, K. J.; Xu, M.; Budd, P. M.; Chaukura, N.; Book, D.; Tedds, S.; Walton, A.; McKeown, N. B. Triptycene-Based Polymers of Intrinsic Microporosity: Organic Materials That Can Be Tailored for Gas Adsorption. Macromolecules 2010, 43, 5287−5294. (16) Budd, P. M.; Ghanem, B. S.; Makhseed, S.; McKeown, N. B.; Msayib, K. J.; Tattershall, C. E. Polymers of Intrinsic Microporosity (PIMs): Robust, Solution-Processable, Organic Nanoporous Materials. Chem. Commun. 2004, 2, 230−231. (17) Masuda, T.; Nagai, K. Synthesis and Permeation Properties of Substituted Polyacetylenes for Gas Separation and Pervaporation. Materials Science of Membranes for Gas and Vapor Separation 2006, 231. (18) Yampolskii, Y. A Current Position of Polyacetylenes Among Other Highly Permeable Membrane Materials. Polym. Rev. 2017, 57, 200−212.

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AUTHOR INFORMATION

Corresponding Author

*E-mail [email protected] (T.A.). ORCID

Toshiki Aoki: 0000-0002-2536-7373 Takashi Kaneko: 0000-0001-7955-9023 Notes

The authors declare no competing financial interest. N


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Macromolecules (19) Masuda, T. Substituted Polyacetylenes. J. Polym. Sci., Part A: Polym. Chem. 2007, 45, 165−180. (20) Aoki, T. Macromolecular Design of Permselective Membranes. Prog. Polym. Sci. 1999, 24, 951−993. (21) Robeson, L. M. Correlation of Separation Factor versus Permeability for Polymeric Membranes. J. Membr. Sci. 1991, 62, 165− 185. (22) Robeson, L. M. The Upper Bound Revisited. J. Membr. Sci. 2008, 320, 390−400. (23) Swaidan, R.; Ghanem, B.; Pinnau, I. Fine-Tuned Intrinsically Ultra Microporous Polymers Redefine the Permeability/Selectivity Upper Bounds of Membrane-Based Airand Hydrogen Separations. ACS Macro Lett. 2015, 4, 947−951. (24) Petersen, J.; Matsuda, M.; Haraya, K. Capillary Carbon Molecular Sieve Membranes Derived from Kapton for High Temperature Gas Separation. J. Membr. Sci. 1997, 131, 85−94. (25) Suda, H.; Haraya, K. Gas Permeation through Micropores of Carbon Molecular Sieve Membranes Derived from Kapton Polyimide. J. Phys. Chem. B 1997, 101, 3988−3994. (26) Kita, H.; Yoshino, M.; Tanaka, K.; Okamoto, K. Gas Permselectivity of Carbonized Polypyrrolone Membrane. Chem. Commun. 1997, 11, 1051−1052. (27) Singh-Ghosal, A.; Koros, W. J. Air Separation Properties of Flat Sheet Homogeneous Pyrolytic Carbon Membranes. J. Membr. Sci. 2000, 174, 177−188. (28) Steel, K. M.; Koros, W. J. Investigation of Porosity of Carbon Materials and Related Effects on Gas Separation Properties. Carbon 2003, 41, 253−266. (29) Kusakabe, K.; Yamamoto, M.; Morooka, S. J. Gas Permeation and Micropore Structure of Carbon Molecular Sieving Membranes Modified by Oxidation. J. Membr. Sci. 1998, 149, 59−67. (30) Kim, Y. K.; Park, H. B.; Lee, Y. M. Preparation and Characterization of Carbon Molecular Sieve Membranes Derived from BTDA-ODA Polyimide and their Gas Separation Properties. J. Membr. Sci. 2005, 255, 265−273. (31) Zhang, B.; Shen, G.; Wu, Y.; Wang, T.; Qiu, J.; Xu, T.; Fu, C. Preparation and Characterization of Carbon Membranes Derived from Poly(phthalazinone ether sulfone) for Gas Separation. Ind. Eng. Chem. Res. 2009, 48, 2886−2890. (32) Ma, X.; Swaidan, R.; Teng, B.; Tan, H.; Salinas, O.; Litwiller, E.; Han, Y.; Pinnau, I. Carbon Molecular Sieve Gas Separation Membranes Based on An Intrinsically Microporous Polyimide Precursor. Carbon 2013, 62, 88−96. (33) Kiyono, M.; Williams, P. J.; Koros, W. J. Effect of Polymer Precursors on Carbon Molecular Sieve Structure and Separation Performance Properties. Carbon 2010, 48, 4432−4441. (34) Ding, S. Y.; Wang, W. Covalent Organic Frameworks (COFs): from Design to Applications. Chem. Soc. Rev. 2013, 42, 548−568. (35) Waller, P. J.; Gándara, F.; Yaghi, O. M. Chemistry of Covalent Organic Frameworks. Acc. Chem. Res. 2015, 48, 3053−3063. Feng, X.; Ding, X.; Jiang, D. Covalent Organic Frameworks. Chem. Soc. Rev. 2012, 41, 6010−6022. (36) Kalidindi, S. B.; Fischer, R. A. Covalent Organic Frameworks and their Metal Nanoparticle Composites: Prospects for Hydrogen Storage. Phys. Status Solidi B 2013, 250, 1119−1127. (37) Côté, A. P.; Benin, A. I.; Ockwig, N. W.; O’Keeffe, M.; Matzger, A. J.; Yaghi, O. M. Thermodynamics of An Incommensurate Quantum Crystal. Science 2005, 310, 1164−1166. (38) Wan, S.; Guo, J.; Kim, J.; Ihee, H.; Jiang, D. A belt-Shaped, Blue Luminescent and Semiconducting Covalent Organic Framework. Angew. Chem., Int. Ed. 2008, 47, 8826−8830. (39) Spitler, E. L.; Colson, J. W.; Uribe-Romo, F. J.; Woll, A. R.; Giovino, M. R.; Saldivar, A.; Dichtel, W. R. Lattice Expansion of Highly Oriented 2D Phthalocyanine Covalent Organic Framework Films. Angew. Chem., Int. Ed. 2012, 51, 2623−2627. (40) Xu, Y.; Jin, S.; Xu, H.; Nagai, A.; Jiang, D. ChemInform Abstract: Conjugated Microporous Polymers: Design, Synthesis and Application. Chem. Soc. Rev. 2013, 42, 8012−8031.

(41) Cooper, A. I. Conjugated Microporous Polymers. Adv. Mater. 2009, 21, 1291−1295. (42) Davankov, V. A.; Tsyurupa, M. P. Structure and Properties of Hypercrosslinked Polystyrene-the First Representative of a New Class of Polymer Networks. React. Polym. 1990, 13, 27−42. (43) Fontanals, N.; Marce, R. M.; Borrull, F.; Cormack, P. A. G. Hypercrosslinked Materials: Preparation, Characterisation and Applications. Polym. Chem. 2015, 6, 7231−7244. (44) Dawson, R.; Cooper, A. I.; Adams, D. J. Nanoporous Organic Polymer Networks. Prog. Polym. Sci. 2012, 37, 530−563. (45) Biswal, B. P.; Chaudhari, H. D.; Banerjee, R.; Kharul, U. K. Chemically Stable Covalent Organic Framework (COF)-Polybenzimidazole Hybrid Membranes: Enhanced Gas Separation through Pore Modulation. Chem. - Eur. J. 2016, 22, 4695−4699. (46) Dykes, G. M. Dendrimers: a Review of their Appeal and Applications. J. Chem. Technol. Biotechnol. 2001, 76, 903−918. (47) Kainz, Q. M.; Reiser, O. Polymer- and Dendrimer-Coated Magnetic Nanoparticles as Versatile Supports for Catalysts, Scavengers and Reagents. Acc. Chem. Res. 2014, 47, 667−677. (48) Steffensen, M. B.; Hollink, E.; Kuschel, F.; Bauer, M.; Simanek, E. E. Dendrimers Based on [1,3,5]-Triazines. J. Polym. Sci., Part A: Polym. Chem. 2006, 44, 3411−3433. (49) Hedrick, J. L.; Trollsås, M. C.; Hawker, J.; Atthoff, B.; Claesson, H.; Heise, A.; Miller, R. D.; et al. Dendrimer-like Star Block and Amphiphilic Copolymers by Combination of Ring Opening and Atom Transfer Radical Polymerization. Macromolecules 1998, 31, 8691− 8705. (50) van Hest, J. C.; Delnoye, D. A.; Baars, M. W.; van Genderen, M. H.; Meijer, E. W. Polystyrene-Dendrimer Amphiphilic Block Copolymers with a Generation-Dependent Aggregation. Science 1995, 268, 1592−1595. (51) Suda, H.; Haraya, K. Gas Permeation through Micropores of Carbon Molecular Sieve Membranes Derived from Kapton Polyimide. J. Phys. Chem. B 1997, 101, 3988−3994. (52) Tanco, M. A. L.; Tanaka, D. A. P.; Rodrigues, S. C.; Texeira, M.; Mendes, A. Composite-Alumina-Carbon Molecular Sieve Membranes Prepared from Novolac Resin and Boehmite. Part I: Preparation, Characterization and Gas Permeation Studies. Int. J. Hydrogen Energy 2015, 40, 5653−5663. (53) Suda, H.; Haraya, K. Alkene/Alkane Permselectivities of a Carbon Molecular Sieve Membrane. Chem. Commun. 1997, 1, 93−94. (54) Zhou, W.; Yoshino, M.; Kita, H.; Okamoto, K. Carbon Molecular Sieve Membranes Derived from Phenolic Resin with a Pendant Sulfonic Acid Group. Ind. Eng. Chem. Res. 2001, 40, 4801− 4807. (55) Barsema, J. N.; Balster, J.; Jordan, V.; van der Vegt, N. F. A.; Wessling, M. Functionalized Carbon Molecular Sieve Membranes Containing Ag-Nanoclusters. J. Membr. Sci. 2003, 219, 47−57. (56) Zhou, W.; Yoshino, M.; Kita, H.; Okamoto, K. Preparation and Gas Permeation Properties of Carbon Molecular Sieve Membranes Based on Sulfonated Phenolic Resin. J. Membr. Sci. 2003, 217, 55−67. (57) Wey, M. Y.; Tseng, H. H.; Chiang, C. K. Effect of MFI Zeolite Intermediate Layers on Gas Separation Performance of Carbon Molecular Sieve(CMS) Membranes. J. Membr. Sci. 2013, 446, 220− 229. (58) Kaneko, T.; Horie, T.; Asano, M.; Aoki, T.; Oikawa, E. Polydendron: Polymerization of Dendritic Phenylacetylene Monomers. Macromolecules 1997, 30, 3118−3121. (59) Aoki, T.; Kaneko, T. New Macromolecular Architectures for Permselective Membranes-Gas Permselective Membranes from Dendrimers and Enantioselectively Permeable Membranes from One-handed Helical Polymers. Polym. J. 2005, 37, 717−735. (60) Kaneko, T.; Yamamoto, K.; Asano, M.; Teraguchi, M.; Aoki, T. Synthesis of Poly(phenylacetylene)-Based Polydendrons Consisting of a Phenyleneethynylene Repeating Unit, and Oxygen/nitrogen Permeation Behavior of their Membranes. J. Membr. Sci. 2006, 278, 365−372. O


Article

Macromolecules (61) Peter, J.; Khalyavina, A.; Kříž, J.; Bleha, M. Synthesis and Gas Transport Properties of ODPA-TAP-ODA Hyperbranched Polyimides with Various Comonomer Ratios. Eur. Polym. J. 2009, 45, 1716−1727. (62) Wang, N.; Ding, L. Cyclodextrin-Based Hyperbranched Polymers by Acyclic Diene Metathesis Polymerization of an ABn Monomer: Molecule Design, Synthesis, and Characterization. J. Polym. Res. 2012, 19, 1−8. (63) Fang, J.; Kita, H.; Okamoto, K. Hyperbranched Polyimides for Gas Separation Applications. 1. Synthesis and Characterization. Macromolecules 2000, 33, 4639−4646. (64) Yates, C. R.; Hayes, W. Synthesis and Applications of Hyperbranched Polymers. Eur. Polym. J. 2004, 40, 1257−1281. (65) Jikei, M.; Kakimoto, M. Hyperbranched Polymers: a Promising New Class of Materials. Prog. Polym. Sci. 2001, 26, 1233−1285. (66) Gao, C.; Yan, D. Hyperbranched Polymers: from Synthesis to Applications. Prog. Polym. Sci. 2004, 29, 183−275. (67) Kong, L. Z.; Sun, M.; Qiao, H. M.; Pan, C. Y. Synthesis and Characterization of Hyperbranched Polystyrene via Click Reaction of AB2 Macromonomer. J. Polym. Sci., Part A: Polym. Chem. 2010, 48, 454−462. (68) Li, J.; Wang, J.; Aoki, T.; Kaneko, T.; Teraguchi, M. Selective Polymerization of Dimethylsilylphenylacetylene and the Gas Permselectivity of the Resulting Polymer Membranes. Chem. Lett. 2015, 44, 182−184. (69) Aoki, T.; Nakahara, H.; Hayakawa, Y.; Kokai, M.; Oikawa, E. Trimethylsilyl-Group Containing Polyphenylacetylenes for Oxygen and Ethanol Permselective Membranes. J. Polym. Sci., Part A: Polym. Chem. 1994, 32, 849−858. (70) The broadening may be caused both by the rigid and planar conjugated branch structures and by the rigid conjugated main chain. Such phenomena were often observed in 1H NMR for conventional poly(substituted acetylene)s. In these cases of the poly(conjugated hyperbranched macromonomer)s, because the branches were also rigid in addition to the main chain, the main chain became more rigid than usual poly(substituted acetylene)s without branches. Therefore, the peaks resulted in showing very broad peaks. (71) Li, J.; Wang, J.; Zang, Y.; Aoki, T.; Kaneko, T.; Teraguchi, M. Enhanced Gas Permselectivity of Copoly(Hyperbranched Macromonomer) Synthesized by One-pot Simultaneous Copolymerization of Dimethylsilyl-Containing Phenylacetylenes. Chem. Lett. 2012, 41, 1462−1464. (72) No hydrosilyation occurred at the double bonds of the polyacetylene backbone and almost no α-adduct formed by 2,1addition judging from the NMR of these model reactions. (73) To promote this situation, a low monomer concentration in the feed was selected. (74) Qiu, W.; Xu, L.; Chen, C.; Paul, D.; Koros, W. Gas Separation Performance of 6FDA-Based Polyimides with Different Chemical Structures. Polymer 2013, 54, 6226−6235. (75) Ma, X.; Salinas, O.; Litwiller, E.; Pinnau, I. Novel Spirobifluorene- and Dibromospirobifluorene-Based Polyimides of Intrinsic Microporosity for Gas Separation Applications. Macromolecules 2013, 46, 9618−9624. (76) Lin, W. H.; Chung, T. S. Gas permeability, Diffusivity, Solubility, and Aging Characteristics of 6FDA-Durene Polyimide Membranes. J. Membr. Sci. 2001, 186, 183−193. (77) No polymers showing higher α than these polyaps(1)s have been reported according to an exhaustive search of the literature (for the total plots and refs 74−76, 78−80 see the Supporting Information (Figure S1), although these three star plots are located below Robeson’s 2008 upper bound. Judging from Robeson’s paper in 2008, there are not many polymers above the upper bound 1991. Also judging from our searching this time, there are only a few polymers above the upper bound 1991. In fact, there are no polymers above the upper bound 1991 especially at the region of PO2 = 40 − 150 and >3000 barrer (see Figure S1). (78) Du, N.; Robertson, G. P.; Song, J.; Pinnau, I.; Thomas, S.; Guiver, M. D. Polymers of Intrinsic Microporosity Containing

Trifluoromethyl and Phenylsulfone Groups as Materials for Membrane Gas Separation. Macromolecules 2008, 41, 9656−9662. (79) Budd, P. M.; Msayib, K. J.; Tattershall, C. E.; Ghanem, B. S.; Reynolds, K. J.; McKeown, N. B.; Fritsch, D. Gas Separation Membranes from Polymers of Intrinsic Microporosity. J. Membr. Sci. 2005, 251, 263−269. (80) Du, N.; Robertson, G. P.; Song, J.; Pinnau, I.; Guiver, M. D. High-Performance Carboxylated Polymers of Intrinsic Microporosity (PIMs) with Tunable Gas Transport Properties. Macromolecules 2009, 42, 6038−6043. (81) Although conventional subnanoporous polymers such as PIM and PI have “subnanopores” between their macromolecules, poly(HBM)s in this study have “subnanopores” between their conjugated rigid hyperbranches inside macromolecules. Therefore, we can estimate the size as pores inside a macromolecule by using molecular modeling calculation (Spartan’08 v1.2.0) based on the welldefined molecular structure. For example, a 3D model in the Graphical Abstract was calculated for one macromolecule having RB = 2.75. (82) The synthetic method for controlling the RB values is discussed in section 2.

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NOTE ADDED AFTER ASAP PUBLICATION This paper was published ASAP on September 13, 2017, with production errors in the caption of Chart 2. The corrected version was reposted on September 14, 2017.

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