Cell Membrane as a Model for the Design of Ion-Active

Biomacromolecules 2002, 3, 167-181

167

Cell Membrane as a Model for the Design of Ion-Active Nanostructured Supramolecular Systems Virgil Percec* and Tushar K. Bera Roy & Diana Vagelos Laboratories, Department of Chemistry, University of Pennsylvania, Philadelphia, Pennsylvania 19104-6323 Received August 27, 2001; Revised Manuscript Received October 8, 2001

The synthesis and polymerization of six AB3 tapered self-assembling methacrylate monomers (5a, 5b, 5c, 5d, 17a, and 17b) based on first generation alkyl substituted benzyl ether monodendrons (i.e., minidendrons) containing oligooxyethylene units at their focal point and the polymerizable group on their periphery are described. The corresponding polymers (6a, 6b, 6c, 6d, 18a, and 18b) self-assemble and subsequently selforganize in supramolecular networks that form a 2-D hexagonal lattice. This network consists of a continuous phase based on a paraffin barrier material perforated in a hexagonal array by ion-active channels constructed from the oligooxyethylenic units protected by the aromatic groups of the taper. Complexation of the oligooxyethylene channels of 6a-d with LiCF3SO3 salt enhances the thermal stability of their hexagonal columnar (φh) liquid crystalline phase. The enhancement of the thermal stability of the φh phase of both monomers and polymers up to 86 °C is also achieved by shifting the placement of the polymerizable group from the 3 position to the 4 position of the 3,4,5-trisubstituted AB3 benzoate monodendrons. The design of these macromolecules was inspired by the bilayer fluid mosaic structure of the cell membrane. The lipid bilayer of the cell membrane that acts in its ordered state as a barrier to the passage of polar molecules was replaced with the paraffinic barrier, while the protein-based ionic channels were replaced with oligooxyethylenic-based channels. The resulted supramolecular material has the mechanical integrity required for the design of ion-active nanostructured supramolecular systems. Introduction The fluid mosaic model of the cell membrane1,2 consists of a lipid bilayer containing active elements constructed from proteins. In its ordered state, this lipid bilayer represents an excellent barrier to the passage of polar molecules and therefore has the ability to partition discrete metabolic aqueous compartments. The impermeability of the lipid bilayer to polar or charged molecules allows the solute concentration on each of its sides to differ dramatically. The second function of the lipid bilayer is to accommodate proteins with various tertiary structures that are able to provide the transfer of energy and materials and also act as catalysts. Simultaneously, the cell membrane has the ability to respond to changing external conditions that demand that certain molecules and ions pass through the lipid bilayer (Figure 1). Although the cell membrane is fluid, the proteins that frequently penetrate its bilayer structure are bound to the membrane mostly by hydrophobic interactions. A similar synthetic supramolecular system capable to be externally regulated could have immense technological implications for areas such as selective membranes, ionic, protonic, and electronic conductors, enzymatic-like catalysis, energy transfer and conversion, particularly if all these functions could be incorporated into the same unit. A bioinspired synthetic system must not copy the cell membrane concept but use its principles as models to create a nonnatural system that is adaptable to the current technological concepts. Therefore, the lipid bilayer barrier may be replaced

with an alternative barrier material that has the required combination of order and fluidity at least during certain stages of its self-assembly and self-organization. Simultaneously, the membrane proteins may be replaced with currently available ion-selective or ion-active elements such as crown ethers or polypodants that are equipped with the ability to spontaneously self-assemble into channels that are incorporated in the barrier part of the material. By analogy with a protein-based ionic channel, this material should be able to flux energy and materials among various compartments. New synthetic mechanisms to externally regulate the on and off states of the channel should be discovered and/or designed. Therefore, bioinspired design and synthesis are not always expected to duplicate concepts from Nature but also can be used to design new concepts that may be suitable for related or different applications. With the goal of creating ion-active self-regulated supramolecular systems, we have first pioneered the design and synthesis of conventional side-chain,2 main-chain,3 and macrocyclic4 liquid crystalline polymers and oligomers containing crown ethers and polypodants. In all cases, calamitic mesogenic groups have been employed to induce in these systems 1-D or 2-D liquidlike nematic and smectic order complemented by ionic activity. Polymerization has been used as the most frequent tool to enable mechanical integrity and provide a broad range of thermal stability of the liquid ordered state.5 Some of this research has been reviewed.6

10.1021/bm010138p CCC: $22.00 © 2002 American Chemical Society Published on Web 12/04/2001

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Figure 1. Schematic representation of the bilayer fluid mosaic model of the cell membrane. Integral proteins are embedded in the bilayer composed of phospholipids and cholesterol. Reproduced from reference 1b with permission of John Wiley & Sons, Inc. Copyright 1999, John Wiley & Sons, Inc.

Figure 2. Self-assembly and self-organization followed by polymerization or polymerization followed by self-assembly and self-organization of tapered monodendrons containing a polymerizable group at the apex (a) or on the periphery of the taper (b). The R group in (b) represents the ionic, electronic, or protonic active element.

A second more efficient class of building blocks that selfassemble into ionic channels that subsequently self-organize in a 2-D hexagonal columnar lattice was subsequently elaborated in our laboratory. This concept is based on tapered minidendritic units containing crown ethers or oligo(ethylene oxide) units in their core (Figure 2). Supramolecular ionactive systems based on both molecular6 and macromolecular7 building blocks were developed based on this concept. Enhanced conductivity along these ionic channels organized in a hexagonal columnar 2-D lattice was reported from our

laboratory.6a,b Subsequently, increased ionic conductivity in other liquid crystalline states was reported from other laboratories.8 Self-assembling tapered molecules containing crown ethers were subsequently employed in a new concept for the design of functional nanoporous membranes known as gel template leaching.9 The mono-10a,b and multifunctionalization11 of the periphery of these building blocks with polymerizable groups has been employed in the design of self-organized soluble and insoluble nanostructured ion-selective membranes. We

Biomacromolecules, Vol. 3, No. 1, 2002 169

Ion-Active Nanostructured Supramolecular Systems

believe that the self-assembling tapered groups containing active element(s) in their core and one or more polymerizable groups on their periphery can be developed to generate a multifunctional membrane that has many of the principles available in the fluid mosaic model of the cell membrane (Figure 1). The aliphatic tails of the tapered groups (Figure 2b) represent more than 80% of the entire supramolecular assembly and therefore provide an excellent and inexpensive barrier material. The functionalization of the tapered building block with one single polymerizable group on its periphery (Figure 2b) provides, after polymerization, a supramolecular soluble network that generates multiple mechanisms for the alignment of its active channels and also for processing. In addition, the introduction in the core of the taper of more than one active element followed by incorporation into a suitable macromolecular architecture could yield membranes with multiple channel functionality useful for ionic, protonic, and electronic transport, for catalysis, and for other functions. This architectural design contrasts the one in which the polymerizable group is attached to the apex of the monodendron when the resulting polymer exhibits a cylindrical structure (Figure 2a).10c-i Last but not least, the liquidlike 2-D self-organized supramolecular structure of the synthetic nanostructured material created by the architectural design described in Figure 2b may provide access to features such as self-repair and external regulation. One of the major requirements for such a nanostructured supramolecular system is that the 2-D self-organized structure should span a broad range of temperature in order to proVide sufficient thermal stability for this functional material. The preViously designed ion-selectiVe and ion-actiVe systems self-assemble in a 2-D hexagonal fluid lattice only after complexation with metal salts.10-12 The goal of this paper is to report the design and synthesis of AB3 tapered minidendritic benzyl ethers containing oligooxyethylene units with different chain lengths in their core as ion-actiVe elements and a single polymerizable group on their periphery. A rational combination of placement of the polymerizable and of the active elements in the structure of the taper will demonstrate that after polymerization, supramolecular networks with a suitable thermal stability of the 2-D hexagonal columnar phase are achievable from conventional starting materials. Although the systems designed here are only ion-active, the results reported in this publication open synthetic pathways to both ion-active and ion-selective 2-D ordered self-organized systems. Results and Discussion Synthesis of Tapered Monomers and Polymers. Scheme 1 outlines the synthesis of monomethacrylate functionalized monoesters (5a-d) of 3,4-bis(4-dodecyloxy benzyloxy)-5(1-methacryloyl undecyloxy) benzoic acid (3) with oligo (oxyethylene) groups in the core (2a-d) containing four, five, six, and nine oxyethylene units. Their corresponding polymethacrylates (6a-d) are also shown in this scheme. The starting compound, 3,4-bis(4-dodecyloxy benzyloxy)5-(11-methacryloyl undecyloxy) benzoic acid (3), was synthesized according to a previously reported procedure.12 tert-

Scheme 1

Butyldimethylsilyl (TBDMS) monoprotected ethylene glycols (2a-d) were subsequently esterified with 3. 2-{2-(2-(2-(2(tert-Butyl dimethyl siloxy)ethoxy)ethoxy)ethoxy)ethoxy}ethanol (2b) was synthesized according to a literature procedure13 from tert-butyldimethylsilyl chloride using an excess of tetraethylene glycol in dry DMF. The other TBDMS monoprotected ethylene glycols were synthesized using identical conditions with those used for 2a to produce 2b (71% yield), 2c (69% yield), and 2d (62% yield). Although 2a-d contain various amounts of TBDMS diprotected ethylene glycols (9-16%, see experimental), they were used directly without any purification in the esterification step, since TBDMS diprotected ethylene glycols remain unreacted during the esterification. The TBDMS protecting group was selected for these experiments both for its ease of introduction and its ability to be selectively cleaved under mild conditions (HF/Py)14 in the presence of benzyl ethers. Neutral conditions (DCC/DPTS) for the esterification were chosen in order to (a) protect the benzyl ether linkage of 3 from cleavage, (b) protect the TBDMS group from cleavage, and (c) prevent the initiation of the polymerization of the

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Table 1. Structural and Thermal Analysis of the Polymers 6a, 6b, 6c, 6d, 18a, and 18b thermal transition (°C) and corresponding enthalpy changes (kcal/mol)a polymer

yield (%)

Mn (GPC)

Mw/Mn (GPC)

6a

80

42 123

2.21

6b

82

46 883

1.98

6c

81

74 229

2.36

6d

82

58 683

2.19

18a

79

65 337

2.08

18b

81

103 029

2.2

heating g 8 k 20 (1.04) k 33 (1.94) i g -12 k 21 (2.57) φh 35 (0.54) i k 5 (0.32) k 17 (3.26) φh 37 (0.47) i k 16 (3.18) φh 36 (0.42) i g -24 k 20 (5.60) i g -21 k 17 (5.11) i g -20 k 17 (6.32) i g -18 k 18 (5.61) i g -19 k 24 (1.48) φh 46 (0.36) i g -11 k 25 (1.62) φh 46 (0.33) i g 14 k 49 (4.9) φh 86 (0.67) i g 14 k 49 (0.97) φh 86 (0.72) i

cooling i 27 (-0.84) φh 9 (-2.43) k i 28 (-0.50) φh 6 (-2.7) k i 6 (-3.83) k i 7 (-6.21) k i 37 (-0.33) φh k 4 (-1.20) g i 77 (-0.72) φh 25 (-0.78) k

a Data on the first line under heating were obtained during the first heating scan. Data on the second line under heating were obtained during the second heating scan.

methacryloyl group present in 3. Therefore, the esterifications of 3 with 2a-d were accomplished under mild conditions in CH2Cl2 at 22 °C. The resulting compounds were purified by column chromatography (SiO2, 2:1 hexanes/EtOAc) to afford 4a (69% yield), 4b (56% yield), 4c (58% yield), and 4d (55% yield). Quantitative deprotection of the TBDMS group of 4a-d was performed using HF/Py in THF at 0 °C without any evidence of benzyl ether cleavage. The crude products were purified by column chromatography (SiO2, 2:1 hexanes/EtOAc) to afford 5a (92% yield), 5b (81% yield), 5c (77% yield), and 5d (72% yield). Polymerization of the resulting methacrylates 5a-d was performed at 60 °C in benzene (50 wt %) using 1.0 wt % AIBN as a radical initiator. The resulting polymethacrylates 6a-d were obtained in 80-82% yields after purification by column chromatography (Al2O3, CH2Cl2 eluent to remove the unreacted monomer). Their number-average molecular weights (Mn) (relative to polystyrene standards) and polydispersities (Mw/Mn) are listed in Table 1. The synthesis of monomers 2-{2-[2-(2-hydroxy ethoxy)ethoxy]ethoxy}ethyl-4-{4′-(11-methacryloyl undecyloxy)benzyloxy}-3,5-bis(4-dodecyloxy benzyloxy) benzoate (17a) and 2-{2-[2-(2-hydroxy ethoxy)ethoxy]ethoxy}ethyl-4-{4′(11-methacryloyl undecyloxy)-benzyloxy}-3,5-bis[6-(dodecyloxy)-2-(methyloxy) naphthalene] benzoate (17b) and their corresponding polymethacrylates 18a and 18b are displayed in Schemes 2-4. The first step in this sequence of reactions involved the etherification of methyl 4-hydroxy benzoate with 11-bromoundecanol using anhydrous K2CO3 in DMF at 70 °C to yield methyl-4-(11-hydroxy undecyloxy) benzoate 7 in 96% yield after recrystallization from acetone (Scheme 2). Quantitative reduction of the ester group of 7 was accomplished by LiAlH4 in THF at 0-22 °C with basic workup to give the corresponding alcohol 8 in 90% yield. In the next step, the synthesis of 4-(11-hydroxy undecyloxy) benzyl chloride (9) requires the chlorination of the benzyl alcohol group of 8. However, 4-(11-hydroxy undecyloxy) benzyl alcohol (8) contains two alcohol groups. The chlorinated product containing both the aliphatic alcohol of 8 and the benzyl alcohol of 8 has almost the same Rf values as the benzyl alcohol chlorinated product 9. This makes the separation of 9 from the reaction mixture by column

Scheme 2

chromatography almost impossible. Recrystallization from different solvents or solvent mixtures also did not produce the expected separation. Therefore, extremely selective and also quantitative chlorination of the benzyl alcohol group of 8 was needed to produce pure 9. This was accomplished with 1.0 equiv of SOCl2 in CH2Cl2 containing a catalytic amount of DMF at 0 °C. After the reaction was completed in 1 h (confirmed by TLC and NMR), CH2Cl2 was distilled at 0 °C. The crude product was immediately purified by recrystallization from acetone to afford 9 in 82% yield. Removal of CH2Cl2 at temperatures higher than 0 °C always produces a certain amount of fully chlorinated product of 8 (5-10%). Methyl 3,4,5-triacetoxy benzoate (10) was synthesized according to a literature procedure23 from methyl 3,4,5trihydroxy benzoate and acetic anhydride using pyridine as catalyst. Alkylation of 10 with 9 was performed using anhydrous K2CO3 in dry acetone at reflux for 30 h. After complete consumption of 9 (confirmed by TLC), H2O was added to deprotect acetoxy groups from the 3 and 5 positions


Ion-Active Nanostructured Supramolecular Systems Scheme 3

Scheme 4

of methyl-4-{4′-(11-acetoxy undecyloxy)-benzyloxy}-3,5dihydroxy benzoate (11) to the corresponding free phenols. These two reactions were accomplished in one pot. The particular benefit of this reaction is that it alleviates the need of complicated and very delicate protection and deprotection steps in acidic mediums because even under very mild acidic conditions, the benzyl ether linkage of 11 cleaves. In the subsequent step (Scheme 3), the alkylation of 4-dodedyloxy benzyl chloride (12a) with 11 using anhydrous K2CO3 in DMF at 70 °C yielded methyl-4-{4′-(11-acetoxy undecyloxy)-benzyloxy}-3,5-bis(4-dodecyloxy benzyloxy) benzoate (13a) in 97% yield (after recrystallization from acetone). The synthesis of methyl-4-{4′-(11-acetoxy undecyloxy)-benzyloxy}-3,5-bis[6-(dodecyloxy)-2-(methyloxy) naphthalene] benzoate (13b) was performed under the identical reaction conditions using 6-(dodecyloxy)-2-(chloromethyl) naphthalene (12b)13 and 11 in 84% yield. The basic hydrolysis of the methyl ester groups of 13a and 13b was accomplished by aqueous KOH in 90% ethanol at reflux to produce the corresponding benzoic acids 14a (95%) and 14b (95%). The benzoic acids 14a and 14b were then esterified with methacryloyl chloride using Et3N in CH2Cl2 at 0-5 °C to produce the methacrylate monomers 4-{4′(11-methacryloyl undecyloxy)-benzyloxy}-3,5-bis(4-dodecyloxy benzyloxy) benzoic acid (15a) and 4-{4′-(11methacryloyl undecyloxy)-benzyloxy}-3,5-bis[6-(dodecyloxy)2-(methyloxy) naphthalene] benzoic acid (15b) in 72-90% yield after the mixed benzoic methacryloyl anhydride was hydrolyzed with Py/H2O at 130 °C.

The benzoic acid derivatives 15a and 15b were then esterified with TBDMS monoprotected tetraethylene glycol (2a) under neutral conditions (DCC/DPTS) identical to the synthesis of 4a to produce 2-{2-(2-(2-tert-butyl dimethyl siloxy ethoxy)ethoxy)ethoxy}ethyl-4-{4′-(11-methacryloyl undecyloxy)-benzyloxy}-3,5-bis(4-dodecyloxy benzyloxy) benzoate (16a) and 2-{2-[2-(2-tert-butyl dimethyl siloxy ethoxy)ethoxy]ethoxy}ethyl-4-{4′-(11-methacryloyl undecyloxy)-benzyloxy}-3,5-bis[6-(dodecyloxy)-2-(methyloxy) naphthalene] benzoic acid (16b) in 72-74% yield after purification by column chromatography (SiO2, 10% EtOAC in hexanes) (Scheme 4). Deprotection of the TBDMS group was conveniently performed using HF/Py in THF at 0-5 °C identical to the synthesis of 5a. After purification by column chromatography (SiO2, 10% EtOAC), monomers 17a and 17b were obtained in 72-78% yield (Scheme 4). The polymerization of the resulting methacrylates 17a and 17b was performed at 60 °C in benzene (50 wt %) using 1.0 wt % AIBN as a radical initiator. The resulting polymethacrylates 18a and 18b were obtained in 79-83% yields after purification by column chromatography (Al2O3, CH2Cl2 eluent to remove the unreacted monomers). Their molecular weights (Mn) relative to polystyrene and polydispersities (Mw/Mn) are listed in Table 1.

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Table 2. Characterization of the Complexes of 6a with Lithium Triflate (LiCF3SO3)a phase transitions (°C) and corresponding enthalpy changes (kcal/mol) (LiCF3SO3)/(6a) 0 0.2

0.4 0.6 0.8 1.0 1.2

heating

cooling

g 7.0 k 20 (1.04) k 33 (2.25) i g -12 k 21 (2.57) φh 35 (0.54) i g 1 k 21 (1.57) φh 47 (0.52) i g -14 k 21 (2.31) φh 48 (0.46) i k 21 (1.0) k 35 (0.08) φh 56 (0.49) i k 21 (2.02) φh 56 (0.46) i k 23 (1.77) φh 68 (0.30) i k 23 (1.81) φh 68 (0.34) i k 29 (3.05) φh 78 (0.15) i k 29 (2.99) φh 79 (0.14) i g 18 k 35 (0.61) i g -9 k 26 (1.50) φh 84 (0.12) i g 18.66 k 36 (1.43) i g -7 k 28 (1.36) φh 82 (0.05) i

i 27 (-0.84) φh 9 (-2.43) k i 40 (-0.61) φh 10 (-2.21) k i 48 (-0.34) φh 9 (-1.74) k i 58 (-0.15) φh 10 (-1.59) k i 66 (-0.07) φh 12 (-1.77) k i 68 (-0.05) φh 13 (1.48) k i 14 (-1.41) k

a Data on the first line under heating are determined during the first heating scan. Data on the second line under heating are determined during the second heating scan.

Table 3. Characterization of the Complexes of 6b with Lithium Triflate (LiCF3SO3)a phase transitions (°C) and corresponding enthalpy changes (kcal/mol) (LiCF3SO3)/(6b) 0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 1.0

heating

cooling

k -5 (0.32) k 17 (3.26) φh 37 (0.50) i k 16 (3.18) φh 36 (0.45) i k 19 (4.04) φh 35 (0.67) i k 19 (4.02) φh 34 (0.49) i k 17 (3.85) φh 43 (0.38) i k 18 (4.23) φh 34 (0.35) i k -18 (0.95) k 19 (4.19) φh 41 (0.91) i g -15 k 19 (4.30) φh 41 (0.65) i k 19 (4.75) φh 43 (0.63) i k 19 (3.93) φh 43 (0.49) i k -18 (0.84) k 18 (3.93) φh 40 (0.53) i g -17 k 19 (4.08) φh 43 (0.60) i g -19 k 19 (3.18) φh 52 (0.21) i g -17 k 20 (3.63) φh 56 (0.32) i k -13 (1.24) k 21 (2.82) φh 60 (0.23) i k 22 (3.47) φh 61 (0.28) i k 24 (3.72) φh 77 (0.07) i k 24 (3.70) φh 78 (0.09) i k -13 (1.50) k 24 (2.78) i k 25 (3.24) φh 56 (0.18) φh 84 (0.05) i

i 28 (-0.50) φh 6 (-2.70) k i 27 (-0.65) φh 8 (-3.90) k i 27 (-0.36) φh 8 (-3.99) k i 33 (-0.52) φh 9 (-4.07) k i 33 (-0.44) φh 8 (-4.27) k i 36 (-0.24) φh 8 (-4.12) k i 44 (-0.30) φh 9 (-3.7) k i 48 (-0.08) φh 9 (-3.5) k i 66 (-0.02) φh 11 (-3.57) k i 10 (-3.87) k


Thermal and Structural Analysis of Supramolecular Networks Resulted from Polymethacrylates 6a-d. The thermal behavior and the structural characterization of polymethacrylates 6a-d were carried out by a combination of techniques that include differential scanning calorimetry (DSC), X-ray diffraction (XRD), and thermal optical polarized microscopy (TOPM) according to procedures used in our laboratory. Transition temperatures and the corresponding enthalpy changes are summarized in Table 1. Polymers 6a and 6b display an enantiotropic hexagonal columnar (φh) liquid crystal (LC) phase. In contrast with 6a and 6b, polymers 6c and 6d are only crystalline (Table 1). Most probably, these polymers exhibit a virtual mesophase5 that is covered by the crystalline phase. A detailed discussion of virtual mesophases in liquid crystalline polymers and their thermodynamic interpretation is presented elsewhere.15

Tables 2-5 summarize the phase transitions and associated enthalpy changes of the complexes of 6a-d, respectively, as a function of the amount of LiCF3SO3 complexed. LiCF3SO3 was selected for these experiments since the triflate anion is soft and therefore produces a more soluble salt than that derived from harder anions. All polymers dissolve LiCF3SO3 salts and form stable complexes with the oligooxyethylene groups. These complexes stabilize the φh LC mesophase up to higher temperatures than those of the individual pure polymers. The assignment of the mesophase was made by X-ray scattering experiments. Figures 3-6 plot the Tg, crystalline-φh transition temperatures (Tk-φh), and φhisotropic transition temperatures (Tφh-i) obtained from the first and second heating scans and the φh-isotropic transition temperatures (Ti-φh) and φh-crystalline transition temperatures (Tφh-k) obtained from the first cooling scan of the


Ion-Active Nanostructured Supramolecular Systems Table 4. Characterization of the Complexes of 6c with Lithium Triflate (LiCF3SO3)a

phase transitions (°C) and corresponding enthalpy changes (kcal/mol) (LiCF3SO3)/(6c) 0 0.1 0.2 0.3 0.4 0.5 0.6 0.8 1.0

heating

cooling

g -24 k 20 (5.60) i g -21 k 17 (5.11) i k -12 (0.71) k 19 (3.76) φh 33 (0.36) i g -14 k 19 (3.27) φh 31 (0.19) i g -24 k 18 (5.09) φh 37 (0.60) i k 18 (3.76) φh 37 (0.47) i k -12 (1.23) k 19 (3.30) φh 41 (0.50) i g -17 k 19 (42.91) φh 41 (0.40) i g -22 k 18 (2.88) φh 43 (0.39) i g -21 k 18 (2.76) φh 43 (0.34) i k -9 (1.42) k 20 (2.54) φh 50 (0.18) i g -15 k 19 (2.20) φh 49 (0.35) i g -23 k 17 (3.25) φh 35 (0.26) i g -20 k 17 (2.95) φh 42 (0.21) i g -24 k 17 (2.78) φh 43 (0.19) i g -17 k 17 (2.71) φh 42 (0.11) i g -22 k 20 (2.82) φh 47 (0.17) i k 18 (2.32) φh 42 (0.08) i

i 7 (-3.59) k i 26 (-0.52) φh 7 (-2.72) k i 32 (-0.58) φh -11 (-3.33) k i 35 (-0.55) φh 7 (-2.72) k i 38 (-0.36) φh 6 (-2.68) k i 44 (-0.21) φh 6 (-1.70) k i 36 (-0.30) φh 5 (-2.74) k i 40 (-0.33) φh 5 (-2.44) k i 4 (-2.17) k


Table 5. Characterization of the Complexes of 6d with Lithium Triflate (LiCF3SO3)a phase transitions (°C) and corresponding enthalpy changes (kcal/mol) (LiCF3SO3)/(6d) 0 0.1 0.2 0.3 0.4 0.6 0.8 1.0 1.2

heating

cooling

g -20 k 17 (6.23) i g -18 k 18 (5.61) i k -16 (1.53) k 20 (3.93) φh 37 (1.01) i k 20 (4.28) φh 35 (0.78) i k -14 (0.55) k 20 (3.32) φh 41 (0.59) i k 20 (4.20) φh 40 (0.92) i k -13 (1.56) k 21 (3.50) φh 48 (0.94) i k 21 (4.10) φh 45 (0.77) i k -12 (1.20) k 20 (2.94) φh 57 (0.77) i g -15 k 21 (4.02) φh 57 (0.53) i k -11 (0.84) k 21 (2.77) φh 59 (0.84) i g -16 k 20 (3.62) φh 53 (0.24) φh 62 (0.21) i k -10 (1.12) k 21 (2.42) φh 65 (0.37) i g -20 k 21 (3.10) φh 57 (0.35) i k -9 (1.19) k 21 (2.25) i g -15 k 21 (2.76) φh 62 (0.17) i k 19 (3.29) i k 20 (3.36) i

i 7 (-6.16) k i 30 (-0.80) φh 9 (-3.98) k i 35 (-0.61) φh 10 (-4.2) k i 39 (-0.44) φh 9 (-4.0) k i 47 (-0.28) φh 9 (-4.01) k i 48 (-0.24) φh 8 (-3.79) k i 53 (-0.17) φh 7 (-3.56) k i 58 (-0.09) φh 7 (-3.26) k i 5 (-3.98) k


complexes of 6a-d, respectively, as a function of the LiCF3SO3 concentration. The addition of LiCF3SO3 does not increase Tg and the crystalline-φh transition temperatures (Tk-φh). However, the φh-isotropic transition temperatures (Tφh-i) increase sharply with increasing LiCF3SO3 concentration in the first and second heating and cooling scans. Nevertheless, both ∆H of melting and isotropization decrease with the increased amount of LiCF3SO3. This trend is observed for all polymers (6a-d) until a concentration of 0.9-1.0 mol equiv of LiCF3SO3 per mol of monomer unit is reached. Above this concentration, the isotropization endotherm broadens and a shift to lower temperatures of both the Tk-φh and Tk-φh transitions is observed in the first cooling and second heating scans. This is due to the thermal

decomposition of the benzyl ether linkage at elevated temperature caused by the Lewis acidity of LiCF3SO3.7c The complexes of 6a, 6b, and 6d with 0.4 mol of LiCF3SO3 were analyzed by small- and wide-angle X-ray scattering. They were characterized in the φh mesophase and below the melting temperatures. The d spacings of all reflections are presented in Table 6 together with their lattice parameter (a) and the column diameter (D). In the φh LC mesophase, 6d with 0.4 mol LiCF3SO3 salt has reflections in the ratio d0/d1 ) 1:1/x3, with only a diffuse scattering at a wide angle. This is indicative of a φh mesophase.6a,16-20 For 6a and 6b with 0.4 mol LiCF3SO3, only two sharp reflections have been observed corresponding to the spacings 54.29 and 26.00 Å for 6a and 53.72 and 27.63 Å for 6b, respectively, in the

174


Figure 3. The dependence of the phase transition temperatures of the complexes of 6a with LiCF3SO3 on the LiCF3SO3/6a molar ratio. Data from the first heating scan: ×, Tg; b, Tk-φh; 1, Tφh-i. Data from the first cooling scan: 3, Ti-φh; +, Tφh-k. Data from the second heating scan: 4, Tg; [, Tk-φh; 0, Tφh-i.

Percec and Bera

Figure 6. The dependence of the phase transition temperatures of the complexes of 6d with LiCF3SO3 on the LiCF3SO3/6d molar ratio. Data from the first heating scan: ×, Tg; b, Tk-φh; 1, Tφh-i. Data from the first cooling scan: 3, Ti-φh; +, Tφh-k. Data from the second heating scan: 4, Tg; [, Tk-φh; 0, Tφh-i. Table 6. Structural Analysis by X-ray Diffraction of the LiCF3SO3 Complexes of 6a, 6b, and 6d and of Uncomplexed 18a and 18b polymer

temp (°C)

d100 (Å)

6a + 0.04a 6b + 0.04a 6d + 0.04a 18a 18b

31 32 32 40 75

54.3 53.7 55.2 54.2 54.3

d110 (Å)

d200 (Å)

d210 (Å)

〈d100〉b

ac (Å)

Dc (Å)

20.2 20.3

53.1 54.5 54.9 53.6 53.8

61.4 62.9 63.5 61.9 62.1

61.4 62.9 63.5 61.9 62.1

26.0 27.6 31.6 26.6 26.8

a Molar % of LiCF SO . b 〈d 3 3 100〉 ) (d100 + x3 d110 + 2 d200 + x7 d210)/ 4; a ) 2〈d100〉/x3. c a ) lattice dimension; D ) column diameter.

Figure 4. The dependence of the phase transition temperatures of the complexes of 6b with LiCF3SO3 on the LiCF3SO3/6b molar ratio. Data from the first heating scan: ×, Tg; b, Tk-φh; 1, Tφh-i. Data from the first cooling scan: 3, Ti-φh; +, Tφh-k. Data from the second heating scan: 4, Tg; [, Tk-φh; 0, Tφh-i.

Figure 5. The dependence of the phase transition temperatures of the complexes of 6c with LiCF3SO3 on the LiCF3SO3/6c molar ratio. Data from the first heating scan: ×, Tg; b, Tk-φh; 1, Tφh-i. Data from the first cooling scan: 3, Ti-φh; +, Tφh-k. Data from the second heating scan: 4, Tg; [, Tk-φh; 0, Tφh-i.

small-angle and a wide-angle diffuse scattering which is indicative of a liquid crystalline mesophase. Although only two reflections were observed at low angles, with spacings

in the 2:1 ratio, the thermal optical polarized microscopy demonstrated that this is most likely a φh phase. The φh phase should also exhibit a reflection with spacing that is 1/x3 times that of the first reflection. This reflection is not observed here most probably due to its low intensity. We note that the 26.00 Å reflection for 6a and the 27.63 Å reflection for 6b are also very weak. Also, the d spacings of the first reflections, that is, 54.29 Å for 6a and 55.21 Å for 6b, indexed as d100 are in the expected range for a φh phase of similar compounds 6d (55.21 Å, d0/d1 ) 1:1/x3), 18a (54.17 Å, d0/d1/d2 ) 1:1/x4:1/x7), and 18b (54.31 Å, d0/ d1/d2 ) 1:1/x4:1/x7). The column diameter (D) increases regularly on increasing the length of the oligooxyethylene spacer, ranging from 61.36 Å for n ) 4 to 63.46 Å for n ) 9. This result matches the trend established by the increase in aliphatic tail length in the tapered group of other selfassembling molecules.13,21 Thermal and Structural Analysis of Supramolecular Networks Resulting from Polymethacrylates 18a and 18b. The transition temperatures and the corresponding enthalpy changes of 18a and 18b are summarized in Table 1. Both display an enantiotropic φh LC phase with varying thermal stability. The degree of supercooling of Ti-φh is low (9 °C which is in the expected range)6e for both 18a and 18b. This indicates thermodynamically controlled self-assembly and self-organization processes. Bragg diffraction peaks corresponding to a lattice spacing in a ratio of 1:1/x4:1/x7 which are characteristic of a 2-D lattice are exhibited at small angles by 18a and 18b in their LC phase. 18a shows roughly the


same column diameter (D ) 61.85 Å, Table 6) as the 18b (D ) 62.14 Å, Table 6). This result is not unexpected, provided the number of tapered groups per column cross section (µ) is the same, since the length of the extended chain conformation of the p-(dodecyloxy)benzyl)oxy tail for 18a and 6-(dodecyloxy)-2-methylenenaphthyl)oxy tail for 18b are identical, that is, 20.3 Å.13 However, the thermal stability of the crystalline and φh LC phases of naphthalene-substituted 18b is increased by 25 and 40 °C, respectively, from that of the phenylene-substituted 18a. This indicates the significant contribution of the aromatic component to the stabilization of the resulting supramolecular architecture. Conclusions The synthesis and structural analysis of six AB3 tapered self-assembling methacrylate monomers based on alkyl benzyl ether monodendrons containing oligooxyethylene units in their focal point and the polymerizable group on their periphery are presented. The corresponding polymers self-assemble and subsequently self-organize in supramolecular networks that form a 2-D hexagonal columnar lattice. This lattice is based on a barrier paraffin matrix that contains ion-active channels arranged in a hexagonal array that is resembling the one reported previously from individual cylindrical polymers7 or supramolecules.6 The stability of the 2-D hexagonal lattice is determined by the placement of the polymerizable group. Symmetric placement in the 4 position of the 3,4,5-trisubstituted benzyl ether favors a thermal stability of up to 86 °C. Ionic conductivity6a,b and ionic transport10a,b,11 in related systems were reported previously, and the materials reported here should behave similarly (to be published). The concept elaborated here was inspired from the fluid mosaic model of the cell membrane and will facilitate access to the design of multifunctional barrier materials with multiple and selective functions. Experimental Section Materials. 4-Dimethylamino pyridine (DMAP, 98%, Fluka), 1,3 dicyclohexyl carbodiimide (DCC, 99%, Aldrich), HCl (A.C.S. Reagents, Fisher Scientific), MgSO4 (Fisher Scientific), and LiAlH4 (95%, Aldrich) were used as received. THF (A.C.S. Reagents, Fisher Scientific) was dried over sodium/benzophenone ketyl and distilled before use. NEt3 (99%, Aldrich) was dried over CaH2 and distilled before use. DMF (A.C.S. Reagents, Fisher Scientific) was dried over CaH2 and distilled under vacuum. CH2Cl2 (A.C.S. Reagents, Fisher Scientific) was dried over CaH2 and distilled. Benzene (A.C.S., Fisher Scientific) was washed with 50 mL portions of H2SO4 until they remained relatively uncolored, washed with H2O to neutral pH, dried over MgSO4, filtered, dried again over sodium/benzophenone ketyl, and freshly distilled before use. LiCF3SO3 (97%, Aldrich) was dried at 100 °C under vacuum for 24 h. Azobisisobutyronitrile (AIBN, Fluka) was recrystallized from methanol below 40 °C. Tetraethylene glycol (99%, Aldrich) was dried over sodium and distilled under vacuum before use. Pentaethylene glycol (98+%, Lancester), hexaethylene glycol (98%, Lancester), and poly-


(ethylene glycol) (average Mw 400, DP ) 9, Aldrich) were dried azeotropically using dried toluene just before use. 4-Dimethylamino pyridinium-p-toluene sulfonate (DPTS),6a 2-{2-(2-(2-(2-(tert-butyldimethylsiloxy)ethoxy)ethoxy)ethoxy)ethanol (2a),13 3,4-bis(4-dodecyloxy benzyloxy)-5-(11-methacryloyl undecyloxy) benzoic acid (3),15 p-(dodecyloxy)benzyl chloride (12a),22 and 6-(dodecyloxy)-2-(chloro methyl)naphthalene (12b)13 were synthesized according to literature procedures. Techniques. 1H NMR (200 MHz) and 13C NMR (50 MHz) were recorded on a Varian Gemini 200 spectrometer with tetramethylsilane (TMS) internal standard for 1H NMR and 13 C. Chromatographic purification was conducted using 200400 mesh silica gel obtained from Natland International Corp., Morrisville, NC. Relative molecular weights were determined using a Perkin-Elmer Series 10 GPC, equipped with a LC-100 column oven (40 °C), Nelson Analytical 900 Series integrator data station, and two Polymer Laboratories PL gel columns of 5 × 102 and 104 Å, and THF as eluent at 1 mL/min. Detection was by UV absorbance at 254 nm. Relative weight-average (Μw) and number-average (Mn) molecular weights were calculated by using a calibration plot constructed from polystyrene standards. High-pressure liquid chromatography experiments were performed with the same instrument. Gas chromatography analysis (GC) was performed on a Hewlett-Packard 5890 gas chromatograph equipped with a packed column of 10% SP 2100 on 80/100 Supelcoport and a Hewlett-Packard 3392A integrator. Thermal transitions were determined on a Perkin-Elmer DSC-7 differential scanning calorimeter. In all cases, the heating and cooling rates were 10 °C/min. First-order transitions were reported as the maxima or minima of the endothermic and exothermic peaks during the second heating and cooling scans. Glass transition temperatures (Tg) were measured as the middle point of the change in heat capacity. Zn and In were used as calibration standards. X-ray diffraction experiments were performed using a multiwire area detector (Siemens) with Cu KR1 radiation obtained from a rotating anode (Nonius FR591) X-ray generator after passing through a set of mirrors and then a monochromator. The X-ray beam path is under low vacuum to reduce the background scattering from air. Powdered samples were held at constant temperature ((0.1 °C) in a temperature-controlled cell. An Olympus BX-40 optical polarized microscope (100× magnification) equipped with a Mettler FP 82 hot stage and a Metler FP 80 central processor was used to verify thermal transitions and to characterize the anisotropic textures. The elemental analyses of all new compounds agree with the theoretical values and are not reported. 2-{2-(2-(2-(2-(tert-Butyl dimethyl siloxy)ethoxy)ethoxy)ethoxy)ethoxy}ethanol (2b). The synthesis of monoprotected pentaethylene glycol (2b) was performed following a modified literature procedure.13 A 100 mL round-bottom flask was charged with 10 g (42.00 mmol) of pentaethylene glycol, tert-butyldimethylsilyl chloride (0.35 g, 2.30 mmol), Et3N (0.23 g, 2.30 mmol), and DMAP (0.012 g, 0.09 mmol) under N2. The reaction was continued for 1.5 h at 22 °C with vigorous stirring. 1H NMR indicated complete consumption of tert-butyldimethylsilyl chloride. The reaction

176


mixture was poured into 300 mL of CHCl3 and extracted with H2O (3 × 200 mL) and saturated NH4Cl. The CHCl3 solution was dried over Na2SO4 and filtered, and the solvent was removed using a rotary evaporator. The crude product was dissolved in Et2O and washed with H2O (2 × 100 mL) and finally with brine. The ethereal solution was dried over MgSO4 and filtered, and the solvent was removed using a rotary evaporator. The product was dried under high vacuum to yield 0.56 g (71%) of a colorless liquid. GC: 90.1% monoprotected, 9.9% diprotected. 1H NMR (200 MHz, CDCl3, 20 °C): δ 0.06 (s, 6H), 0.9 (s, 9H), 3.5-3.8 (overlapped m, 20H). 13C NMR (50 MHz, CDCl3, 20 °C): δ -5.4, 18.1, 25.8, 61.4, 62.6, 70.1-72.5 (m). 2-{2-(2-(2-(2-(2-(tert-Butyl dimethyl siloxy)ethoxy)ethoxy)ethoxy)ethoxy)ethoxy}ethanol (2c). This compound was synthesized from hexaethylene glycol using a similar procedure as the one used for 2b. Starting from 0.30 g (1.99 mmol) of tert-butyldimethylsilyl chloride and 15 g (53.19 mmol) of hexaethylene glycol, 0.42 g (69%) of 2c was obtained. GC: 84% monoprotected, 16% diprotected. 1H NMR (200 MHz, CDCl3, 20 °C): δ 0.06 (s, 6H), 0.9 (s, 9H), 3.5-3.8 (overlapped m, 24H). 13C NMR (50 MHz, CDCl3, 20 °C): δ -5.4, 18.2, 25.8, 61.4, 62.5, 70.1-72.5 (m). Mono(tert-butyldimethylsilyl) Protected Poly(ethylene glycol) (Avg Mn ) 400 DP, n ) 9) (2d). This compound was synthesized from poly(ethylene glycol) (avg Mn ) 400) using a similar procedure as the one used for 2b. Starting from 0.30 g (1.9 mmol) of tert-butyldimethylsilyl chloride and 20 g (50.0 mmol) of poly(ethylene glycol), 0.63 g (62%) of 2d was obtained. 1H NMR (200 MHz, CDCl3, 20 °C): δ 0.06 (s, 6H), 0.9 (s, 9H), 3.5-3.8 (overlapped m, 36H).13C NMR (50 MHz, CDCl3, 20 °C): δ -5.5, 18.2, 25.7, 61.5, 62.5, 70.2-72.5 (m). 2-{2-(2-(2-tert-Butyl dimethyl siloxy ethoxy)ethoxy]ethoxy}ethyl-3,4-bis(4-dodecyloxy benzyloxy)-5-(11-methacryloyl undecyloxy) Benzoate (4a). To a well-stirred solution of 3 (3.5 g, 3.65 mmol) and 2a (1.41 g, 4.57 mmol) in 50 mL of dry CH2Cl2, DCC (1.88 g, 9.14 mmol) and DPTS (0.26 g, 0.914 mmol) were added under N2. The reaction was continued for 24 h at 22 °C. The reaction mixture was diluted with hexanes (100 mL) and filtered. The solvent was evaporated in a rotary evaporator resulting in a light yellow viscous mass. The raw product was purified by column chromatography (silica gel, EtOAC/hexanes ) 1:2) to yield 3.16 g (69.54%) of 4a as a colorless liquid. Purity: 99% (HPLC). TLC: Rf ) 0.48 (2/1 hexanes/EtOAc). 1H NMR (200 MHz, CDCl3, 20 °C): δ 0.05 (s, 6H), 0.84 (s, 9H), 0.88 (m, 6H), 1.26 (m, 54H), 1.7-1.9 (m, 6H), 1.93 (s, 3H), 3.53 (t, 2H, J ) 6.8 Hz), 3.63-3.88 (m, 12H), 3.924.09 (overlapped m, 6H), 4.12 (t, 2H, J ) 6.5 Hz), 4.44 (t, 2H, J ) 6.6 Hz), 5.0 (s, 2H), 5.02 (s, 2H), 5.53 (s, 1H), 6.08 (s, 1H), 6.76 (d, 2H, J ) 8.51 Hz), 6.86 (d, 2H, J ) 8.63 Hz), 7.28-7.32 (overlapped m), 7.34 (s, 1H). 13C NMR (50 MHz, CDCl3, 20 °C): δ -5.04, 14.3, 18.5, 22.9, 24.6, 24.9-32.5 (m), 35.1, 49.8, 57.7, 62.9, 64.3, 65.0, 68.2, 69.4, 70.9, 71.3, 72.8, 74.8, 108.6, 109.2, 114.3, 114.6, 125.1, 125.3, 128.8, 129.4-130.3 (m), 152.7, 153.2, 159.2, 166.4. 2-{2-(2-(2-(2-tert-Butyl dimethyl siloxy ethoxy)ethoxy)ethoxy)ethoxy}ethyl-3,4-bis(4-dodecyloxy benzyloxy)-5-

Percec and Bera

(11-methacryloyl undecyloxy) Benzoate (4b). This compound was synthesized from 2b using a similar procedure as the one used for 4a. Starting from 2.7 g (2.82 mmol) of 3, 1.19 g (3.37 mmol) of 2b, 2.09 g (10.14 mmol) of DCC, 0.305 g (1.014 mmol) of DPTS, and 40 mL of dry CH2Cl2, 2.03 g (55.9%) of 4b was obtained as a colorless viscous product. Purity: 99% (HPLC). TLC: Rf ) 0.51 (2/1 hexanes/ EtOAc). 1H NMR (200 MHz, CDCl3, 20 °C): δ 0.05 (s, 6H), 0.84 (s, 9H), 0.88 (m, 6H), 1.26 (m, 54H), 1.7-1.9 (m, 6H), 1.93 (s, 3H), 3.53 (t, 2H, J ) 6.8 Hz), 3.63-3.88 (m, 16H), 3.92-4.09 (overlapped m, 6H), 4.12 (t, 2H, J ) 6.5 Hz), 4.44 (t, 2H, J ) 6.6 Hz), 5.0 (s, 2H), 5.02 (s, 2H), 5.53 (s, 1H), 6.08 (s, 1H), 6.76 (d, 2H, J ) 8.51 Hz), 6.86 (d, 2H, J ) 8.63 Hz), 7.28-7.32 (overlapped m), 7.34 (s, 1H). 13C NMR (50 MHz, CDCl3, 20 °C): δ -5.04, 14.3, 18.5, 22.9, 24.6, 24.9-32.5 (m), 35.1, 49.8, 57.7, 62.9, 64.3, 65.0, 68.2, 69.4, 70.9, 71.3, 72.8, 74.8, 108.6, 109.2, 114.3, 114.6, 125.1, 125.3, 128.8, 129.4-130.3 (m), 152.7, 153.2, 159.2, 166.4. 2-{2-(2-(2-(2-(2-tert-Butyl dimethyl siloxy ethoxy)ethoxy)ethoxy)ethoxy)ethoxy}ethyl-3,4-bis(4-dodecyloxy benzyloxy)-5-(11-methacryloyl undecyloxy) Benzoate (4c). This compound was synthesized from 2c using a similar procedure as the one used for 4a. Starting from 2.75 g (2.87 mmol) of 3, 1.48 g (3.73 mmol) of 2c, 1.77 g (8.61 mmol) of DCC, 0.25 g (0.861 mmol) of DPTS, and 40 mL of dry CH2Cl2, 2.22 g (58%) of 4c was obtained as a colorless viscous product. Purity: 99% (HPLC). TLC: Rf ) 0.50 (2/1 hexanes/EtOAc). 1H NMR (200 MHz, CDCl3, 20 °C): δ 0.05 (s, 6H), 0.84 (s, 9H), 0.88 (m, 6H), 1.26 (m, 54H), 1.7-1.9 (m, 6H), 1.93 (s, 3H), 3.53 (t, 2H, J ) 6.8 Hz), 3.63-3.88 (m, 20H), 3.92-4.09 (overlapped m, 6H), 4.12 (t, 2H, J ) 6.5 Hz), 4.44 (t, 2H, J ) 6.6 Hz), 5.0 (s, 2H), 5.02 (s, 2H), 5.53 (s, 1H), 6.08 (s, 1H), 6.76 (d, 2H, J ) 8.51 Hz), 6.86 (d, 2H, J ) 8.63 Hz), 7.28-7.32 (overlapped m), 7.34 (s, 1H). 13C NMR (50 MHz, CDCl3, 20 °C): δ -5.04, 14.3, 18.5, 22.9, 24.6, 24.9-32.5 (m), 35.1, 49.8, 57.7, 62.9, 64.3, 65.0, 68.2, 69.4, 70.9, 71.3, 72.8, 74.8, 108.6, 109.2, 114.3, 114.6, 125.1, 125.3, 128.8, 129.4-130.3 (m), 152.7, 153.2, 159.2, 166.4. Mono(tert-butyldimethylsilyl) Protected Poly(ethylene glycol) (Avg DP, n ) 9) 3,4-Bis(4-dodecyloxy benzyloxy)5-(11-methacryloyl undecyloxy) Benzoate (4d). This compound was synthesized from 2d using a similar procedure as the one used for 4a. Starting from 2.75 g (2.87 mmol) of 3, 1.91 g (3.73 mmol) of 2d, 1.77 g (8.61 mmol) of DCC, 0.25 g (0.861 mmol) of DPTS, and 40 mL of dry CH2Cl2, 2.3 g (55%) of 4c was obtained as a colorless viscous product. Purity: 99% (HPLC). TLC: Rf ) 0 (2/1 hexanes/ EtOAc). 1H NMR (200 MHz, CDCl3, 20 °C): δ 0.05 (s, 6H), 0.84 (s, 9H), 0.88 (m, 6H), 1.26 (m, 54H), 1.7-1.9 (m, 6H), 1.93 (s, 3H), 3.53 (t, 2H, J ) 6.8 Hz), 3.63-3.88 (m, 32H), 3.92-4.09 (overlapped m, 6H), 4.12 (t, 2H, J ) 6.5 Hz), 4.44 (t, 2H, J ) 6.6 Hz), 5.0 (s, 2H), 5.02 (s, 2H), 5.53 (s, 1H), 6.08 (s, 1H), 6.76 (d, 2H, J ) 8.51 Hz), 6.86 (d, 2H, J ) 8.63 Hz), 7.28-7.32 (overlapped m), 7.34 (s, 1H). 13C NMR (50 MHz, CDCl3, 20 °C): δ -5.04, 14.3, 18.5, 22.9, 24.6, 24.9-32.5 (m), 35.1, 49.8, 57.7, 62.9, 64.3, 65.0, 68.2, 69.4, 70.9, 71.3, 72.8, 74.8, 108.6, 109.2, 114.3, 114.6, 125.1, 125.3, 128.8, 129.4-130.3 (m), 152.7, 153.2, 159.2, 166.4.


2-{2-(2-(2-Hydroxy ethoxy)ethoxy]ethoxy}ethyl-3,4-bis(4-dodecyloxy benzyloxy)-5-(11-methacryloyl undecyloxy) Benzoate (5a). The deprotection of 4a was performed using a modified literature procedure.14 To a solution of 4a (1.8 g, 1.44 mmol) and dry THF (20 mL) in a 100 mL polypropylene flask containing a Teflon-coated magnetic star bar, HF‚pyridine (1 mL, 35 mmol) was added at 0 °C under N2. The reaction was continued for 2 h. The reaction mixture was diluted with 100 mL of Et2O. The ether solution was washed with H2O (1 × 100 mL), 0.1 (N) HCl (1 × 100 mL), 0.1 (N) NaHCO3 (2 × 100 mL), H2O (1 × 100 mL), and brine (2 × 100 mL) and finally dried over MgSO4. The solution was filtered and the solvent was evaporated in vacuo, resulting in a light yellow solid. The crude product was purified by column chromatography (silicagel, EtOAC/ hexane ) 1:2) to yield 1.48 g (92%) of 5a as a colorless solid. Purity: 99% (HPLC). TLC: Rf ) 0 (2/1 hexanes/ EtOAc). 1H NMR (200 MHz, CDCl3, 20 °C): δ 0.89 (m, 6H), 1.27 (m, 54H), 1.7-1.9 (m, 6H), 1.94 (s, 3H), 3.55 (t, 2H, J ) 6.5 Hz), 3.63-3.78 (m, 12H), 3.92-4.10 (overlapped m, 6H), 4.12 (t, 2H, J ) 6.7 Hz), 4.45 (t, 2H, J ) 6.8 Hz), 5.0 (s, 2H), 5.02 (s, 2H), 5.53 (s, 1H), 6.09 (s, 1H), 6.77 (d, 2H, J ) 8.31 Hz), 6.86 (d, 2H, J ) 8.56 Hz), 7.277.33 (overlapped m, 5H), 7.34 (s, 1H). 13C NMR (50 MHz, CDCl3, 20 °C): δ 14.4, 23.0, 26.4, 28.0-32.2 (m), 64.4, 65.1, 68.3, 69.5, 70.6, 70.9, 71.5, 74.9, 108.7, 109.4, 114.4, 114.8, 125.3, 125.4, 129.0-130.4 (m), 152.5, 153.2, 159.4, 166.3. DSC: first heating, k 32.1 i; second heating, k 32.2 i; first cooling, i 12.87 k. 2-{2-(2-(2-(2-Hydroxy ethoxy)ethoxy)ethoxy)ethoxy}ethyl-3,4-bis(4-dodecyloxy benzyloxy)-5-(11-methacryloyl undecyloxy) Benzoate (5b). This compound was synthesized from 4b using a similar procedure as the one used for 5a. Starting from 1.8 g (1.39 mmol) of 4b, 1 mL (35.0 mmol) of HF‚pyridine, and 20 mL of dry THF, 1.68 g (81.2%) of 5b was obtained. Purity: 99% (HPLC). TLC: Rf ) 0 (2/1 hexanes/EtOAc). 1H NMR (200 MHz, CDCl3, 20 °C): δ 0.88 (m, 6H), 1.27 (m, 54H), 1.7-1.9 (m, 6H), 1.93 (s, 3H), 3.55 (t, 2H, J ) 6.6 Hz), 3.61-3.76 (m, 16H), 3.9-4.10 (overlapped m, 6H), 4.12 (t, 2H, J ) 7.1 Hz), 4.45 (t, 2H, J ) 6.8 Hz), 5.01 (s, 2H), 5.02 (s, 2H), 5.52 (s, 1H), 6.09 (s, 1H), 6.78 (d, 2H, J ) 8.21 Hz), 6.86 (d, 2H, J ) 8.44 Hz), 7.27-7.31 (overlapped m, 5H), 7.31 (s, 1H). 13C NMR (50 MHz, CDCl3, 20 °C): δ 14.5, 23.0, 26.4, 28.0-32.3 (m), 64.4, 65.1, 68.3, 69.5, 70.6, 70.9, 71.5, 74.9, 108.7, 109.4, 114.4, 114.8, 125.3, 125.4, 129.2-130.4 (m), 152.5, 153.2, 159.4, 166.2. DSC: first heating, k -0.73 k 30.61 i; second heating, k 28.68 i; first cooling, i 10.15 k. 2-{2-(2-(2-(2-(2-Hydroxy ethoxy)ethoxy)ethoxy)ethoxy)ethoxy}ethyl-3,4-bis(4-dodecyloxy benzyloxy)-5-(11-methacryloyl undecyloxy) Benzoate (5c). This compound was synthesized from 4c using a similar procedure as the one used for 5a. Starting from 2.0 g (1.49 mmol) of 4c, 1 mL (35.0 mmol) of HF‚pyridine, and 20 mL of dry THF, 1.44 g (77%) of 5c was obtained as a colorless viscous product. Purity: 99% (HPLC). TLC: Rf ) 0 (2/1 hexanes/EtOAc). 1H NMR (200 MHz, CDCl , 20 °C): δ 0.88 (m, 6H), 1.27 3 (m, 54H), 1.7-1.9 (m, 6H), 1.93 (s, 3H), 3.55 (t, 2H, J )


6.6 Hz), 3.61-3.76 (m, 20H), 3.9-4.10 (overlapped m, 6H), 4.12 (t, 2H, J ) 7.1 Hz), 4.45 (t, 2H, J ) 6.8 Hz), 5.01 (s, 2H), 5.02 (s, 2H), 5.52 (s, 1H), 6.09 (s, 1H), 6.78 (d, 2H, J ) 8.21 Hz), 6.86 (d, 2H, J ) 8.44 Hz), 7.27-7.31 (overlapped m, 5H), 7.31 (s, 1H). 13C NMR (50 MHz, CDCl3, 20 °C): δ 14.5, 23.0, 26.4, 28.0-32.3 (m), 64.4, 65.1, 68.3, 69.5, 70.6, 70.9, 71.5, 74.9, 108.7, 109.4, 114.4, 114.8, 125.3, 125.4, 129.2-130.4 (m), 152.5, 153.2, 159.4, 166.2. Monohydroxy Poly(ethylene glycol) (Avg Mn ) 400 DP, n ) 9) 3,4-Bis(4-dodecyloxy benzyloxy)-5-(11-methacryloyl undecyloxy) Benzoate (5d). This compound was synthesized from 4d using a similar procedure as the one used for 5a. Starting from 2.0 g (1.36 mmol) of 4d, 1 mL (35.0 mmol) of HF‚pyridine, and 20 mL of dry THF, 1.31 g (72%) of 5d was obtained as a colorless viscous product. Purity: 99% (HPLC). TLC: Rf ) 0 (2/1 hexanes/EtOAc). 1 H NMR (200 MHz, CDCl3, 20 °C): δ 0.88 (m, 6H), 1.27 (m, 54H), 1.7-1.9 (m, 6H), 1.93 (s, 3H), 3.55 (t, 2H, J ) 6.6 Hz), 3.61-3.76 (m, 32H), 3.9-4.10 (overlapped m, 6H), 4.12 (t, 2H, J ) 7.1 Hz), 4.45 (t, 2H, J ) 6.8 Hz), 5.01 (s, 2H), 5.02 (s, 2H), 5.52 (s, 1H), 6.09 (s, 1H), 6.78 (d, 2H, J ) 8.21 Hz), 6.86 (d, 2H, J ) 8.44 Hz), 7.27-7.31 (overlapped m, 5H), 7.31 (s, 1H). 13C NMR (50 MHz, CDCl3, 20 °C): δ 14.5, 23.0, 26.4, 28.0-32.3 (m), 64.4, 65.1, 68.3, 69.5, 70.6, 70.9, 71.5, 74.9, 108.7, 109.4, 114.4, 114.8, 125.3, 125.4, 129.2-130.4 (m), 152.5, 153.2, 159.4, 166.2. Methyl-4-(11-hydroxy undecyloxy) Benzoate (7). Methyl-4-hydroxy benzoate (23 g, 0.15 mol), 11-bromoundecanol (40 g, 0.16 mol), K2CO3 (51.3 g, 0.37 mol), and 200 mL of DMF were mixed in a 500 mL two-necked flask under N2. The reaction mixture was degassed for 20 min by N2 and heated at 70 °C for 24 h. After cooling to 22 °C, the reaction mixture was poured into 1.0 L of ice-water. The white solid compound was filtered and dried. Recrystallization from acetone yielded 46.85 g (96%) of 7 as white crystals; mp: 78-79 °C. Purity: 99% (HPLC). TLC: Rf ) 0 (2/1 hexanes/ EtOAc). 1H NMR (200 MHz, CDCl3, 20 °C): δ 1.30 (m, 16H), 1.76 (m, 2H), 3.64 (q, 2H, J ) 6.2 Hz), 3.88 (s, 3H), 4.0 (t, 2H, J ) 6.5 Hz), 6.9 (d, 2H, J ) 8.8 Hz), 7.97 (d, 2H, J ) 8.8 Hz). 13C NMR (50 MHz, CDCl3, 20 °C): δ 26, 29.5, 32.9, 52.0, 63.2, 68.3, 114.2, 122.4, 131.7, 163.1, 167.1. 4-(11-Hydroxy undecyloxy) Benzyl Alcohol (8). A 1 L two-necked flask containing a Teflon-coated magnetic stir bar and a nitrogen inlet was charged with LiAlH4 (6.56 g, 0.17 mol) and dry THF (350 mL) under N2. The reaction mixture was cooled to 0 °C, and 7 (46.85 g, 0.14 mol) was freshly added to it as a solid under N2. After stirring vigorously at 22 °C for 2 h, excess LiAlH4 was quenched by slow addition of H2O followed by addition of 50% (wt) NaOH (0.19 mol) aqueous solution. The organic phase was separated by filtration and evaporated in vacuo. Recrystallization from acetone yielded 38.5 g (90%) of 8 as white crystals; mp: 84-85 °C. Purity: 99% (HPLC). TLC: Rf ) 0 (2/1 hexanes/EtOAc). 1H NMR (200 MHz, CDCl3, 20 °C): δ 1.30 (m, 16H), 1.77 (m, 2H), 3.63 (q, 2H, J ) 6.5 Hz), 3.95 (t, 3H, J ) 6.5 Hz), 4.6 (s, 2H), 6.88 (d, 2H, J ) 6.6 Hz), 7.27 (d, 2H, J ) 8.5 Hz). 13C NMR (50 MHz, CDCl3, 20 °C): δ 26.1, 29.6, 33.0, 63.3, 65.2, 68.2, 114.7, 128.8, 133.2, 159.0.

178


4-(11-Hydroxy undecyloxy) Benzyl Chloride (9). A 500 mL three-necked flask containing a Teflon-coated magnetic stir bar and a N2 inlet was charged with compound 8 (32.24 g, 0.11 mol) and dry CH2Cl2 (200 mL) under N2. The reaction mixture was cooled to 0 °C, and few drops of DMF were added. After 15 min of stirring, SOCl2 (8.0 mL, 0.11 mol) dissolved in dry CH2Cl2 (200 mL) was added dropwise. The reaction was continued for 1 h at 0 °C, and the solvent was evaporated in vacuo at 0 °C. The crude product was recrystallized from acetone to produce 9 (28.2 g, 82%) as white crystals; mp: 71-72 °C. Purity: 99% (HPLC). TLC: Rf ) 0.1 (4/1 (v/v), hexanes/EtOAc). 1H NMR (200 MHz, CDCl3, 20 °C): δ 1.30 (m, 16H), 1.77 (m, 2H), 3.64 (t, 2H, J ) 6.5 Hz), 3.95 (t, 3H, J ) 6.5 Hz), 4.56 (s, 2H), 6.86 (d, 2H, J ) 6.6 Hz), 7.29 (m, 2H). 13C NMR (50 MHz, CDCl3, 20 °C): δ 26.1, 29.6, 33.0, 46.6, 63.2, 68.2, 114.9, 129.6, 130.2, 159.4. Methyl-3,4,5-triacetoxy Benzoate (10). A 250 mL twonecked flask containing a Teflon-coated magnetic stir bar and a N2 inlet was charged with methyl-3,4,5-trihydroxy benzoate (20 g, 108.6 mmol) and acetic anhydride (37.69 g, 369.0 mmol) under N2. Dry pyridine (29.18 g, 369.0 mmol) was added slowly through an addition funnel to this reaction mixture at 0 °C with constant stirring. When the addition was complete, the temperature of the reaction mixture was raised to 22 °C and the stirring was continued for 16 h. The reaction mixture was poured into a mixture of ice and water (1 L). The compound was separated by filtration, washed several times with H2O, and finally dried under air. Recrystallization from EtOAc/hexanes produced 32.45 g (96.4%) of 10 as white crystals; mp: 123-125 °C (lit23 mp 122124 °C). Purity: 99% (HPLC). 1H NMR (200 MHz, CDCl3, 20 °C): δ 2.24 (s, 9H), 3.9 (s, 3H), 7.93 (s, 2H). Methyl-4-{4′-(11-acetoxy undecyloxy)-benzyloxy}-3,5dihydroxy Benzoate (11). A 100 mL two-necked flask containing a Teflon-coated magnetic stir bar and a N2 inlet was charged with 9 (2.0 g, 5.80 mmol), 10 (1.5 g, 4.83 mmol), K2CO3 (3.2 g, 23.20 mmol), and 60 mL of dry acetone under N2. The reaction mixture was refluxed for 30 h with constant stirring under N2. The reaction mixture was cooled to 22 °C and was poured into 500 mL of H2O with vigorous stirring. The aqueous phase was extracted with Et2O two times, and the organic phases were combined and washed with 10% HCl solution followed by H2O two times and finally with brine. The ethereal solution was dried over MgSO4 and concentrated by rotary evaporation. The crude product was recrystallized from acetone to yield 1.79 g of 22 as white crystals (74%). Purity: 99% (HPLC); mp: 7884 °C. TLC: Rf ) 0 (2:1 hexanes/EtOAc). 1H NMR (200 MHz, CDCl3, 20 °C): δ 1.1-1.9 (overlapped m, 18H), 2.1 (s, 3H), 3.87 (s, 3H), 3.88-4.0 (t, 2H, J ) 6.22 Hz), 4.014.1 (t, 2H, J ) 6.96 Hz), 5.0-5.1 (s, 2H), 5.8 (s, 2H), 6.86.9 (d, 2H, J ) 8.43 Hz), 7.2-7.3 (d, 2H J ) 8.7 Hz). 13C NMR (90 MHz, CDCl3, 20 °C): δ 21.2, 26.0, 26.2, 28.7, 29.3-29.6 (m), 32.7, 52.4, 65.0, 68.2, 75.4, 109.7, 114.5114.9 (m), 126.0, 128.4, 129.3-130.5 (m), 137.5, 149.3, 159.9, 167.2, 171.9. Methyl-4-{4′-(11-acetoxy undecyloxy)-benzyloxy}-3,5bis(4-dodecyloxy benzyloxy) Benzoate (13a). To a round-

Percec and Bera

bottom flask equipped with a N2 inlet-outlet, containing a degassed stirring mixture of 11 (3.0 g, 5.96 mmol) and K2CO3 (6.58 g, 47.68 mmol) in 60 mL of DMF at 60 °C, was added 12a (3.7 g, 11.92 mmol) in small portions over 10 min under N2. After 24 h at 60 °C, the reaction mixture was poured into a 500 mL ice-water mixture. The aqueous phase was extracted with Et2O two times, and the organic phases were combined and washed with 10% HCl solution followed by H2O twice and finally with brine. The ethereal solution was dried over MgSO4 and concentrated by rotary evaporation. The crude product was recrystallized from acetone to yield 6.1 g of 13a as white crystals (97.4%). Purity: 99% (HPLC); mp: 62-64 °C. TLC: Rf ) 0.54 (2:1 hexanes/ EtOAc). 1H NMR (200 MHz, CDCl3, 20 °C): δ 0.8-1.0 (m, 6H), 1.1-1.9 (overlapped m, 64H), 2.1 (s, 3H), 3.8-4.1 (overlapped m, 11H), 3.88-4.0 (t, 2H, J ) 6.22 Hz), 5.0 (s, 2H), 5.1 (s, 4H), 6.7-6.8 (d, 2H, J ) 8.06 Hz), 6.81-6.92 (d, 4H, J ) 8.6 Hz), 7.2-7.4 (m, 8H). 13C NMR (90 MHz, CDCl3, 20 °C): δ 14.3, 21.2, 26.1-26.2 (m), 28.7-29.8 (m), 32.1, 52.3, 64.8, 68.1, 68.2, 71.2, 74.8, 109.3, 114.2, 114.6, 125.1, 128.7-130.4 (m), 152.8, 159.2, 166.8, 171.3. Methyl-4-{4′-(11-acetoxy undecyloxy)-benzyloxy}-3,5bis [6-(dodecyloxy)-2-(methyloxy) naphthalene] Benzoate (13b). To a round-bottom flask equipped with a N2 inletoutlet, containing a degassed stirring mixture of 11 (6.0 g, 11.93 mmol) and K2CO3 (5.95 g, 43.09 mmol) in 100 mL of DMF at 60 °C, was added 12b (8.61 g, 23.87 mmol) in small portions over 10 min under N2. After 24 h at 60 °C, the reaction mixture was poured into a 500 mL ice-water mixture. The aqueous phase was extracted with Et2O two times, and the organic phases were combined and washed with 10% HCl solution followed by H2O twice and finally with brine. The ethereal solution was dried over MgSO4 and concentrated by rotary evaporation. The crude product was recrystallized by acetone to yield 11.55 g of 19 as white crystals (84%). Purity: 99% (HPLC); mp: 103-104 °C. TLC: Rf ) 0.49 (2:1 hexanes/EtOAc). 1H NMR (200 MHz, CDCl3, 20 °C): δ 0.8-1.0 (t, 6H, J ) 6.6 Hz), 1.1-1.9 (overlapped m, 56H), 2.1 (s, 3H), 3.7-3.9 (overlapped m, 4H), 4.0-4.1 (q, 6H, J ) 6.67 Hz), 5.0-5.1 (s, 2H), 5.25.3 (s, 4H), 6.6-6.7 (d, 2H, J ) 8.67 Hz), 7.1-7.9 (overlapped m, 16H). 13C NMR (90 MHz, CDCl3, 20 °C): δ 14.3, 21.2, 22.8, 26.0, 26.2, 26.3, 28.7, 29.4-29.8 (m), 32.1, 52.3, 64.8, 68.0, 68.2, 71.6, 75.0, 106.6, 109.3, 114.2, 119.4, 126.1, 126.6, 127.2, 128.7, 129.6, 130.3, 131.8, 134.5, 141.2, 152.9, 157.5, 158.4, 167.1. 4-{4′-(11-Hydroxy undecyloxy)-benzyloxy}-3,5-bis(4dodecyloxy benzyloxy) Benzoic Acid (14a). In a 250 mL round-bottom flask containing a Teflon-coated magnetic stir bar was placed 13a (6.24 g, 5.90 mmol), 60 mL of 90% EtOH, and KOH pellets (1.32 g, 23.62 mmol). The mixture was refluxed for 2 h. The reaction mixture was cooled to 22 °C, and EtOH was removed by rotary evaporation. The resulting solid was dissolved in 200 mL of hot THF with stirring. The THF solution was cooled and acidified with concentrated HCl at 0 °C. The acidified THF solution was poured into a mixture of ice-water and extracted with Et2O (3 × 100 mL). The combined ethereal solution was washed with H2O twice and finally with brine. The ethereal solution


was dried over MgSO4 and concentrated by rotary evaporation. The crude product was recrystallized by acetone to yield 5.87 g of 14a as white crystals (95%). Purity: 99% (HPLC); mp: 89-91 °C. TLC: Rf ) 0 (2:1 hexanes/EtOAc). 1H NMR (200 MHz, CDCl3, 20 °C): δ 0.8-1.0 (m, 6H), 1.1-1.9 (overlapped m, 64H), 3.6-3.7 (t, 2H, J ) 6.23 Hz), 3.84.0 (overlapped m, 8H), 5.0 (bs, 6H), 6.7-6.8 (d, 2H, J ) 7.7 Hz), 6.81-6.92 (d, 4H, J ) 7.8 Hz), 7.2-7.4 (m, 8H). 13C NMR (90 MHz, CDCl , 20 °C): δ 14.3, 18.5, 22.9, 26.2, 3 28.8, 29.4-29.8 (m), 32.1, 65.0, 68.2, 71.2, 74.9, 109.8, 114.2, 114.6, 125.3, 128.4, 129.4, 129.6, 130.4, 136.7, 152.8, 159.2. 4 -{4′-(11-Hydroxy undecyloxy)-benzyloxy}-3,5-bis[6(dodecyloxy)-2-(methyloxy) naphthalene] Benzoic Acid (14b). In a 250 mL round-bottom flask containing a Tefloncoated magnetic stir bar was placed 13b (11.0 g, 9.5 mmol), 60 mL of 90% EtOH, and KOH pellets (1.32 g, 23.62 mmol). The mixture was refluxed for 2 h. The reaction mixture was cooled to 22 °C, and EtOH was removed by rotary evaporation. The resulting solid was dissolved in 200 mL of hot THF with stirring. The THF solution was cooled and acidified with concentrated HCl at 0 °C. The acidified THF solution was poured into a mixture of ice-water and extracted with Et2O (3 × 100 mL). The combined ethereal solution was washed with H2O twice and finally with brine. The ethereal solution was dried over MgSO4 and concentrated by rotary evaporation. The crude product was recrystallized by acetone to yield 9.9 g of 14b as white crystals (95%). Purity: 99% (HPLC); mp: 138-140 °C. TLC: Rf ) 0 (2/1 hexanes/EtOAc). 1H NMR (200 MHz, CDCl3, 20 °C): δ 0.8-1.0 (m, 6H), 1.1-1.9 (overlapped m, 56H), 3.5-3.7 (t, 2H, J ) 6.6 Hz), 3.7-3.9 (t, 2H, J ) 3.3 Hz), 4.0-4.2 (m, 6H), 5.1 (s, 2H), 5.2-5.3 (s, 4H), 6.6-6.7 (d, 2H, J ) 7.1 Hz), 7.1-7.9 (overlapped m, 16H). 13C NMR (90 MHz, CDCl3, 20 °C): δ 14.3, 22.9, 25.9, 26.2, 26.3, 29.4-29.8 (m), 32.1, 32.9, 63.2, 68.0, 68.2, 71.6, 75.0, 106.6, 109.8, 114.3, 119.5, 126.2, 126.7, 127.2, 128.8, 129.6, 130.4, 131.7, 134.5, 141.3, 152.9, 157.5, 158.4. 4-{4′-(11-Methacryloyl undecyloxy)-benzyloxy}-3,5-bis(4-dodecyloxy benzyloxy) Benzoic Acid (15a). Methacryloyl chloride (1.57 g, 15.04 mmol) was slowly added to a cold (0 °C) solution of 14a (4.8 g, 4.82 mmol) and Et3N (1.52 g, 15.10 mmol) in 50 mL of CH2Cl2 under N2. The ice-cooling was removed, and the reaction mixture was stirred for 24 h at 22 °C. The reaction mixture was concentrated at 0 °C and diluted with 200 mL of Et2O. The ethereal solution was washed with H2O (2 × 100 mL), 2 N NaOH (3 × 100 mL), 2 N HCl (2 × 100 mL), H2O (2 × 100 mL), and finally with brine. The ethereal solution was dried over MgSO4 and concentrated by rotary evaporation. The crude product was dissolved in 60 mL of pyridine, and 10 mL of deionized H2O was added to this reaction mixture. The reaction mixture was heated at 130 °C for 2 h. The reaction mixture was cooled to 22 °C and poured into a mixture of ice-H2O and acidified with concentrated HCl at 0 °C. The acidified aqueous phase was extracted with Et2O (3 × 100 mL). The combined ethereal solution was washed with H2O three times and finally with brine. The ethereal solution was dried over MgSO4 and concentrated by rotary


evaporation. The crude product was recrystallized by acetone to yield 4.6 g of 15a as white crystals (89.8%). Purity: 99% (HPLC); mp: (unstable during heating due to polymerization). TLC: Rf ) 0 (2:1 hexanes/EtOAc). 1H NMR (200 MHz, CDCl3, 20 °C): δ 0.8-1.0 (m, 6H), 1.1-1.9 (overlapped m, 64H), 2.0 (s, 3H), 3.8-4.0 (overlapped m, 8H), 4.0-4.2 (t, 2H, J ) 6.6 Hz), 5.0 (bs, 6H), 5.5 (s, 1H), 6.1 (s, 1H), 6.7-6.8 (d, 2H, J ) 7.7 Hz), 6.81-6.92 (d, 4H, J ) 7.85 Hz), 7.2-7.4 (m, 8H). 13C NMR (50 MHz, CDCl3, 20 °C): δ 14.3, 18.5, 22.9, 26.3, 28.8, 29.5, 29.8, 32.1, 65.0, 68.2, 71.2, 74.9, 109.8, 114.3, 114.6, 124.2, 125.3, 128.6, 129.5, 130.4, 152.8, 159.2, 166.0. 4-{4′-(11-Methacryloyl undecyloxy)-benzyloxy}-3,5-bis[6-(dodecyloxy)-2-(methyloxy) naphthalene] Benzoic Acid (15b). Methacryloyl chloride (1.93 g, 18.55 mmol) was slowly added to a cold (0 °C) solution of 14b (8.5 g, 7.78 mmol) and Et3N (1.87 g, 18.55 mmol) in 50 mL of CH2Cl2 under N2. The ice-cooling was removed, and the reaction mixture was stirred for 24 h at 22 °C. The reaction mixture was concentrated at 0 °C and diluted with 200 mL of Et2O. The ethereal solution was washed with H2O (2 × 100 mL), 2 N NaOH (3 × 100 mL), 2 N HCl (2 × 100 mL), H2O (2 × 100 mL), and finally with brine. The ethereal solution was dried over MgSO4 and concentrated by rotary evaporation. The crude product was dissolved in 60 mL of pyridine, and 10 mL of deionized H2O was added to this reaction mixture. The reaction mixture was heated at 130 °C for 2 h. The reaction mixture was cooled to 22 °C, poured into a mixture of ice-H2O, and acidified with concentrated HCl at 0 °C. The acidified aqueous phase was extracted with Et2O (3 × 100 mL). The combined ethereal solution was washed with H2O three times and finally with brine. The ethereal solution was dried over MgSO4 and concentrated by rotary evaporation. The crude product was recrystallized by acetone to yield 6.5 g of 15b as white crystals (72%). Purity: 99% (HPLC); mp: (unstable during heating due to polymerization). TLC: Rf ) 0 (2/1 hexanes/EtOAC). 1H NMR (200 MHz, CDCl3, 20 °C): δ 0.8-0.9 (t, 6H, J ) 7.4 Hz), 1.12.0 (overlapped m, 56H), 2.0 (s, 3H), 3.7-3.9 (t, 2H, J ) 6.5 Hz), 4.0-4.2 (m, 8H), 5.1 (s, 2H), 5.2-5.3 (s, 4H), 5.5 (s, 1H), 6.1 (s, 1H), 6.6-6.8 (d, 2H, J ) 8.34 Hz), 7.1-7.9 (overlapped m, 16H). 13C NMR (50 MHz, CDCl3, 20 °C): δ 14.4, 18.6, 22.9, 26.4, 28.8, 29.5, 29.7, 29.9, 32.2, 65.1, 68.1, 68.3, 71.7, 75.1, 106.7, 109.9, 114.4, 119.5, 124.4, 125.4, 126.2, 126.8, 127.3, 128.9, 129.7, 130.4, 131.8, 134.6, 141.0, 153.0, 157.6, 159.6, 171.7. 2-{2-(2-(2-tert-Butyl dimethyl siloxy ethoxy)ethoxy)ethoxy}ethyl-4-{4′-(11-methacryloyl undecyloxy)-benzyloxy}3,5-bis(4-dodecyloxy benzyloxy) Benzoate (16a). To a wellstirred solution of 15a (3.5 g, 3.29 mmol) and 2a (1.21 g, 3.94 mmol) in 50 mL of CH2Cl2, DCC (2.03 g, 9.85 mmol) was added under N2. DPTS (0.115 g, 0.394 mmol) was then added last. The reaction mixture was stirred for 24 h at 22 °C. The reaction mixture was diluted with 100 mL of hexanes and filtered. Evaporation of the solvent gave an oily residue. Purification by column chromatography (silica gel, 10% EtOAc in hexanes) gave 16a (3.2 g, 72%) as a light yellow oil. Purity: 99% (HPLC). TLC: Rf ) 0.53 (2:1 hexanes/ EtOAc). 1H NMR (200 MHz, CDCl3, 20 °C): δ 0.05-0.1

180


(s, 6H), 0.8-1.0 (bs, 9 H), 1.1-1.9 (overlapped m, 64H), 2.0 (s, 3H), 3.5 (t, 2H, J ) 6.5 Hz), 3.6-3.8 (overlapped m, 12 H), 3.81-4.0 (overlapped m, 6H), 4.0-4.2 (t, 2H, J ) 6.8 Hz), 4.4 (t, 2H, J ) 6.7 Hz), 5.0 (m, 6H), 5.5 (s, 1H), 6.1 (s, 1H), 6.7-6.8 (d, 2H, J ) 7.7 Hz), 6.81-6.92 (d, 4H, J ) 7.8 Hz), 7.2-7.4 (m, 8H). 13C NMR (50 MHz, CDCl3, 20 °C): δ 5.09, 14.3, 18.5, 22.7, 26.1, 28.5, 29.5, 29.6, 32.1, 62.8, 64.3, 65.0, 68.2, 70.8, 71.6, 72.8, 74.9, 109.8, 114.2, 114.8, 124.6, 125.5, 128.1, 129.7, 130.4, 152.8, 159.1, 166. 2-{2-[2-(2-tert-Butyl dimethyl siloxy ethoxy)ethoxy]ethoxy}ethyl-4-{4′-(11-methacryloyl undecyloxy)-benzyloxy}3,5-bis[6-(dodecyloxy)-2-(methyloxy) naphthalene] Benzoic Acid (16b). To a well-stirred solution of 15b (3.0 g, 2.58 mmol) and 2a (0.91 g, 2.96 mmol) in 50 mL CH2Cl2, DCC (1.52 g, 7.4 mmol) was added under N2. DPTS (0.174 g, 0.59 mmol) was then added last. The reaction mixture was stirred for 24 h at 22 °C. The reaction mixture was diluted with 100 mL of hexanes and filtered. Evaporation of solvent gave an oily residue. Purification by column chromatography (silica gel, 10% EtOAc in hexanes) gave 16b (2.58 g, 69%) as a light yellow oil. Purity: 99% (HPLC). TLC: Rf ) 0.51 (2:1 hexanes/EtOAc). 1H NMR (200 MHz, CDCl3, 20 °C): δ 0.1 (s, 6H), 0.8-0.9 (m, 15H), 1.1-2.0 (overlapped m, 56H), 2.1 (s, 3H), 3.5-3.9 (overlapped m, 16H), 4.0-4.2 (m, 8H), 4.3-4.5 (t, 2H, J ) 5.04 Hz), 5.1 (s, 2H), 5.2-5.3 (s, 4H), 5.5 (s, 1H), 6.1 (s, 1H), 6.6-6.8 (d, 2H, J ) 8.67 Hz), 7.1-7.9 (overlapped m, 16H). 13C NMR (50 MHz, CDCl3, 20 °C): δ -5.09, 14.3, 18.5, 22.8, 26.3, 28.7, 29.4, 29.6, 29.8, 32.0, 62.8, 64.3, 64.9, 68.0, 68.2, 69.4, 70.8, 71.6, 72.8, 75.0, 106.6, 109.6, 114.2, 119.4, 125.2, 126.4, 126.6, 127.2, 128.8, 129.5, 130.3, 131.8, 134.5, 141.1, 152.8, 157.5, 159.1, 166.2. 2-{2-[2-(2-Hydroxy ethoxy)ethoxy]ethoxy}ethyl-4-{4′(11-methacryloyl undecyloxy)-benzyloxy}-3,5-bis(4-dodecyloxy benzyloxy) Benzoate (17a). The deprotection of 16a was performed as described in the synthesis of 4a. Deprotection of 2.0 g (1.47 mmol) of 16a resulted in 1.37 g (75%) of 17a as a white solid after purification by column chromatography (silica gel, 10% EtOAc in hexanes). Purity: 99% (HPLC). TLC: Rf ) 0 (2:1 hexanes/EtOAc). 1H NMR (200 MHz, CDCl3, 20 °C): δ 0.8-1.0 (bs, 9 H), 1.1-1.9 (overlapped m, 64H), 2.0 (s, 3H), 3.5 (t, 2H, J ) 6.5 Hz), 3.6-3.8 (overlapped m, 12 H), 3.81-4.0 (overlapped m, 6H), 4.0-4.2 (t, 2H, J ) 6.8 Hz), 4.4 (t, 2H, J ) 6.7 Hz), 5.0 (m, 6H), 5.5 (s, 1H), 6.1 (s, 1H), 6.7-6.8 (d, 2H, J ) 7.7 Hz), 6.81-6.92 (d, 4H, J ) 7.8 Hz), 7.2-7.4 (m, 8H). 13C NMR (50 MHz, CDCl3, 20 °C): δ 14.3, 18.5, 22.6, 26.4, 28.2, 29.4, 32.1, 62.8, 64.3, 65.0, 68.1, 70.8, 71.5, 72.6, 74.9, 109.8, 114.2, 114.6, 124.6, 125.5, 128.1, 129.6, 130.4, 152.8, 159.3, 166.1. DSC: first heating, k 40.32 i; second heating, k 39.01 i; first cooling, i 21.29 k. 2-{2-[2-(2-Hydroxy ethoxy)ethoxy]ethoxy}ethyl-4-{4′(11-methacryloyl undecyloxy)-benzyloxy}-3,5-bis[6-(dodecyloxy)-2-(methyloxy) naphthalene] Benzoate (17b). The deprotection of 16b was performed as described in the synthesis of 4a. Deprotection of 2.0 g (1.37 mmol) of 16b resulted in 1.32 g (72%) of 17b as a white solid after purification by column chromatography (silica gel, 10% EtOAc in hexanes). Purity: 99% (HPLC); mp: (unstable

Percec and Bera

during heating due to polymerization). TLC: Rf ) 0 (2:1 hexanes/EtOAc). 1H NMR (200 MHz, CDCl3, 20 °C): δ 0.80.9 (t, 6H, J ) 6.62 Hz), 1.1-2.0 (overlapped m, 56H), 2.1 (s, 3H), 3.5-3.9 (overlapped m, 16H), 4.0-4.2 (m, 8H), 4.3-4.5 (t, 2H, J ) 5.04 Hz), 5.1 (s, 2H), 5.2-5.3 (s, 4H), 5.5 (s, 1H), 6.1 (s, 1H), 6.6-6.8 (d, 2H, J ) 8.67 Hz), 7.17.9 (overlapped m, 16H). 13C NMR (50 MHz, CDCl3, 20 °C): δ 14.3, 18.4, 22.8, 26.3, 28.7, 29.4, 29.6, 29.8, 32.0, 61.8, 64.3, 64.9, 68.0, 68.2, 69.4, 70.4, 70.7, 71.7, 72.6, 75.0, 106.6, 109.6, 114.2, 119.4, 125.2, 126.2, 126.6, 127.2, 128.8, 129.5, 130.3, 131.9, 134.5, 141.2, 152.8, 157.5, 159.1, 166.2. Polymerization of Monomers 5a, 5b, 5c, 5d, 17a, and 17b. All monomers were polymerized as 50% (w/v) solutions in benzene under argon at 60 °C for 48 h. AIBN (1% w/w) was used as a radical initiator. The polymerization solutions were degassed by three freeze-pump-thaw cycles before polymerization. All polymers were separated from unreacted monomers by column chromatography (neutral alumina, CH2Cl2). The yield and molecular weight distributions and DSC of the polymers obtained are shown in Table 1. Poly(2-{2-(2-(2-hydroxy ethoxy)ethoxy)ethoxy}ethyl3,4-bis(4-dodecyloxy benzyloxy)-5-(11-methacryloyl undecyloxy) benzoate) (6a). 1H NMR (200 MHz, CDCl3, 20 °C): δ 0.9 (br, 6H), 1.3-2.1 (br, 63H), 3.5 (br, 2H), 3.64.2 (br, 20H), 4.5 (br, 2H) 5.1 (br, 4H), 6.8-7.3 (br, 10 H). Poly(2-{2-(2-(2-(2-hydroxy ethoxy)ethoxy)ethoxy)ethoxy}ethyl-3,4-bis(4-dodecyloxy benzyloxy)-5-(11-methacryloyl undecyloxy) benzoate) (6b). 1H NMR (200 MHz, CDCl3, 20 °C): δ 0.9 (br, 6H), 1.3-2.1 (br, 63H), 3.5 (br, 2H), 3.6-4.2 (br, 24H), 4.5 (br, 2H) 5.1 (br, 4H), 6.8-7.3 (br, 10 H). Poly(2-{2-(2-(2-(2-(2-hydroxy ethoxy)ethoxy)ethoxy)ethoxy)ethoxy}ethyl-3,4-bis(4-dodecyloxy benzyloxy)-5-(11methacryloyl undecyloxy) benzoate) (6c). 1H NMR (200 MHz, CDCl3, 20 °C): δ 0.9 (br, 6H), 1.3-2.1 (br, 63H), 3.55 (br, 2H), 3.6-4.2 (br, 28H), 4.5 (br, 2H) 5.1 (br, 4H), 6.8-7.3 (br, 10 H). Poly(monohydroxy poly(ethylene glycol) (Avg DP, n ) 9) 3,4-bis (4-dodecyloxy benzyloxy)-5-(11-methacryloyl undecyloxy) benzoate) (7d). 1H NMR (200 MHz, CDCl3, 20 °C): δ 0.9 (br, 6H), 1.3-2.1 (br, 63H), 3.55 (br, 2H), 3.6-4.2 (br, 40H), 4.5 (br, 2H) 5.1 (br, 4H), 6.8-7.3 (br, 10 H). Poly(2-{2-[2-(2-hydroxy ethoxy)ethoxy]ethoxy}ethyl-4{4′-(11-methacryloyl undecyloxy)-benzyloxy}-3,5-bis(4dodecyloxy benzyloxy) benzoate) (17a). 1H NMR (200 MHz, CDCl3, 20 °C): δ 0.8-2.0 (br, 76 H), 3.5-4.2 (br, 22H), 4.4 (bs, 2H), 5.0 (br, 6H), 6.7-6.9 (br, 6H), 7.2-7.4 (br, 8H). Poly(2-{2-[2-(2-hydroxy ethoxy)ethoxy]ethoxy}ethyl-4{4′-(11-methacryloyl undecyloxy)-benzyloxy}-3,5-bis[6(dodecyloxy)-2-(methyloxy) naphthalene] benzoate) (17b). 1H NMR (200 MHz, CDCl , 20 °C): δ 0.8-2.1 (br, 65H), 3 3.5-4.5 (br, 26H), 5.0-5.3 (bs, 6H), 6.6-7.9 (br, 18H). Complexes of Polymers with LiCF3SO3. All complexes were prepared as reported previously.2j-l,6a,b Acknowledgment. Financial support by the Office of Naval Research and National Science Foundation is gratefully acknowledged.


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