AIM

In the present study, our strategy is to extend the π-conjugated system from H-acceptor emitters of small molecules to light-emitting H-acceptor polymers. A series of novel homopolymeric and random-copolymeric H-acceptor emitters containing carbazole moieties (to increase Tg values and hole-transporting properties of PLEDs) and three-conjugated aromatic rings, including one pendent pyridyl terminus (as the H-acceptor site) and two lateral methoxyl groups on the middle rings (to increase solubility after polymerization), were successfully synthesized. By incorporating with different generations of OXD dendritic H-donors bearing benzoic acids, the supramolecular side-chain copolymers (i.e., H-bonded dendritic complexes) were consecutively constructed. Hopefully, supramolecular dendrimers bearing light-emitting H-acceptor polymers (in comparison with small molecular emitters) will have a better film-forming property by the spin-coating process, which may eventually be more useful in PLED device applications.

In our previous work, the mesomorphic and photophysical properties of the H-bonded trimers and polymer networks can be easily adjusted by tuning the non-photoluminescent H-donor acids (or H-donor polymers) and fluorescent H-acceptors (small molecules) in the H-bonded complexes. Unique mesomorphic properties can be introduced to these supramolecular structures containing

non-mesogenic H-acceptor emitters. In the meanwhile, the emission properties of bis-pyridyl H-acceptor emitters can be manipulated by their surrounding non-photoluminescent proton donors. Moreover, new light-emitting H-bonded side-chain dendritic complexes containing side-chain H-acceptor copolymers and electron-transporting H-donor dendrimers have been developed recently, where side-chain H-acceptor copolymers were composed of light-emitting H-acceptor and hole-transporting (carbazole) moieties. In this report, H-bonded side-chain copolymer and homopolymer complex networks containing non-photoluminescent H-donor (benzoic acid) and fluorescent H-acceptor pendants, which involve three-conjugated aromatic rings with pyridyl terminus and lateral methoxyl groups on the middle rings (to increase solubility after polymerization), were successfully synthesized. The copolymerization of H-donor (benzoic acid) and fluorescent H-acceptor monomers with different molar ratios is to avoid the spontaneous aggregation of the π-conjugated H-acceptor emitters and further to tune their emission colors. In addition, the processes of blending H-donor and H-acceptor homopolymers to form H-bonded homopolymer complexes are prepared for comparative purposes. Accordingly, H-bonded effects on the mesomorphic, photophysical, and electro-optical properties of these H-bonded polymer networks are investigated in the present work. Moreover, herein we design and synthesize a side-chain conjugated polymer with pyridyl

pendant group as receptors for analyte matirals. The selectivity and sensitivity of polymer sensor, titration experiments were conducted with an addition of various metal ions. In addition, compare the sensitivity of polymer with its complementary monomer, PL-quenching characteristics toward Cu²⁺ ion were investigated.

Chapter 2

Study of Supramolecular Side-Chain Copolymers Containing Light-Emitting H-Acceptors and Electron-Transporting Dendritic H-Donors

2.1 Abstract

A novel light-emitting hydrogen-bonded (H-) acceptor PBB (M1) containing three conjugated aromatic rings, including one pyridyl terminus and two lateral methoxyl groups (on the middle ring), was successfully synthesized via Horner-Wadsworth-Emmons (HWE) olefination and Sonogashira coupling reaction.

Moreover, different molar ratios of light-emitting H-acceptor monomer PBB (M1) and hole-transporting monomer CAZ (M2) bearing a carbazole unit were copolymerized through free radical polymerization to obtain light emitting and hole-transporting H-acceptor copolymers (P1-P5). H-acceptor copolymers P3 and P4 were complexed with different generations of dendritic H-donors (G1COOH-G3COOH) bearing 1,3,4-oxadiazole (OXD) dendrons and terminal benzoic acids via H-bonded self-assembly to form supramolecular side-chain copolymers (i.e., H-bonded dendritic complexes). In contrast to H-acceptor homopolymer P1 (HPBB), H-acceptor copolymers P2-P4 incorporated with

carbazole (CAZ) moieties effectively enhance the glass transition temperatures (Tgs) and minimize the interchain interations of the light-emitting H-acceptor units, and similar effects occur in their H-bonded dendritic complexes. In addition, red shifts of photoluminescence (PL) emissions in H-bonded dendritic complexes can be tuned up to 61 nm. Furthermore, H-bonded dendritic complexes excited at 305 nm of OXD absorption can create a stronger fluorescence than that excited at 397 nm of PBB absorption, indicating that the intensity of the sensitized emission of PBB (by energy transfer from OXD absorption at 305 nm) is even stronger than that of a direct emission of PBB (by merely PBB absorption at 397 nm). The OXD dendritic wedges in H-bonded dendritic complexes can lower the LUMO energy levels and provide a better electron injection property. H-acceptor polymer P4 and its H-bonded dendritic complexes showed electroluminescence (EL) emissions in the range of 464-519 nm from blue to green. In addition, a PLED device containing H-bonded dendritic complex P4/G1COOH showed an EL emission of 519 nm under a turn-on voltage of 6.5 V, with a maximum luminance of 408 cd/m² at 18 V and a luminance efficiency of 0.39 cd/A at 100 mA/cm², respectively.

2.2 Introduction

In recent years, polymeric materials based on spontaneous formation of supramolecular architectures by self-assembly of various organic molecular components have attracted great attention in areas ranging from chemistry to materials science.1,2 Simple association of two complementary compounds through specific noncovalent interactions, such as hydrogen-bonded (H-bonded),^2,19-26 ionic,^27,28 and metal-coordinative^29-32 interactions between molecular components, can give rise to unique properties and phase structures, which are not possessed by the individual components. Intensive researches have been directed toward functional supramolecular systems to control the dimensionality and shape of self-assembled structures through molecular design, but it remains a challenge driven by a wide variety of potential applications in the fields of catalyzes, microelectronics, nonlinear optics, sensors, and display technologies. Since the first polymeric light-emitting diode (PLED) based on poly(p-phenylenevinylene) (PPV) was reported by Burroughes et al.,³³ various kinds of conjugated main-chain and side-chain polymers have been developed for electroluminescent (EL) devices.^34-37 Future applications of PLEDs to full-color and large-area flat panel displays become possible due to their high luminescence efficiency, low cost, high flexibility, and easy fabrication of spin-coating technique.³⁸ However, the most important problem with the π-conjugated

systems is their tendency to form aggregates/excimers via π-π interactions in the solid state, which will lead to red shifts or low-energy band gaps of emission spectra, self-quenching of excitons, and reduction of fluorescence quantum efficiencies. To overcome this problem, one of the approaches is to introduce dendritic architectures into the π-conjugated systems so as to prevent close chains from packing and thus to increase the polymer luminescent efficiency and reduce the tendency of aggregation.

For instance, Fréchet-type poly(aryl ether) dendrons attached to fluorene units were reported by Carter et al.³⁹ to demonstrate the shielding effect by attaching dendritic side chains to the conjugated polyfluorene backbones, which improved the luminescence properties of these materials due to the reduction of both aggregates/excimers in solution and solid states. Müllen et al.⁴⁰ prepared polyfluorene-based conjugated polymers with bulky polyphenylene dendritic substituents at C-9 position, which suppressed the formation of aggregates with long wavelength emissions, and thus a pure blue emission was acquired. More recently, a number of dendrimers have been reported for a wide variety of applications in such EL device^41-51 and photovoltaic (PV) cell^52,53 materials. In our previous work,⁵⁴ H-donor dendrimers with a benzoic acid terminus were singly/doubly H-bonded to mono/bis-pyridyl H-acceptor emitters to form several series of novel supramolecular dendrimers, whose emission colors could be easily adjusted by their

non-light-emitting H-donors. Moreover, the higher generation of dendritic sizes could afford stronger siteisolation and dendron-dilution effects, so better energy transfer along with higher fluorescence quantum efficiencies were achieved.

In the present study, our strategy is to extend the π-conjugated system from H-acceptor emitters of small molecules to light-emitting H-acceptor polymers.

According to Scheme 1, a series of novel homopolymeric and random-copolymeric H-acceptor emitters containing carbazole moieties (to increase Tg values and hole-transporting properties of PLEDs) and three-conjugated aromatic rings, including one pendent pyridyl terminus (as the H-acceptor site) and two lateral methoxyl groups on the middle rings (to increase solubility after polymerization), were successfully synthesized. By incorporating with different generations of OXD dendritic H-donors bearing benzoic acids (see Figure 2.1), the supramolecular side-chain copolymers (i.e., H-bonded dendritic complexes) were consecutively constructed as shown in Figure 2.2. Hopefully, supramolecular dendrimers bearing light-emitting H-acceptor polymers (in comparison with small molecular emitters) will have a better film-forming property by the spin-coating process, which may eventually be more useful in PLED device applications. Accordingly, H-bonded effects on the thermal, photophysical, and photo-/electro-luminescent properties of these supramolecules in the solid state will be illustrated.

COOH

Figure 2.1 Different generations of dendritic H-donors (G1COOH–G3COOH)

used in H-bonded side-chain dendritic complexes.

Figure 2.2 Schematic representation of H-acceptor copolymers and H-bonded

side-chain dendritic complexes bearing different generations of dendritic H-donors (G1COOH–G3COOH).

2.3 Experimental Section

2.3.1 Measurements and Characterization

1H NMR spectra were recorded on a Varian Unity 300 MHz spectrometer using CDCl3 and DMSO-d6 as solvents. Elemental analyses were performed on a HERAEUS CHN-OS RAPID elemental analyzer. High resolution electron impact mass data were obtained on a Finnigan-MAT-95XL. Phase transition temperatures were determined by differential scanning calorimetry (DSC, model: Perkin Elmer Diamond) under N2 with a heating and cooling rate of 10 °C/min and polarizing optical microscope (POM, model: Leica DMLP) equipped with a hot stage.

Thermogravimetric analyses (TGA) were carried out on a TA Instruments Q500 thermogravimetric analyzer at a heating rate of 20 °C/min under nitrogen. Gel permeation chromatography (GPC) analyses were conducted on a Water 1515 separation module using polystyrene as a standard and THF as an eluant. Fourier transform infrared (FTIR) spectra of samples (dispersed in KBr disks) were recorded on a Perkin-Elmer Spectrum 100 Series. Synchrotron powder X-ray diffraction (XRD) measurements were performed at the beamline BL17A of the National Synchrotron Radiation Research Center (NSRRC), Taiwan (for details of the XRD installation, see Supporting Information). UV-vis absorption spectra were recorded on a HP G1103A spectrophotometer, and photoluminescence (PL) spectra were obtained on a Hitachi

F-4500 spectrophotometer in dilute THF solutions (10^-6 M). The PL quantum yields (ΦPL) of polymers were measured with 9,10-diphenylanthracene as a reference (in cyclohexane, ΦPL = 0.9).⁵⁵ Thin films in UV-vis and PL measurements were prepared by spin-coating of THF solutions (with a concentration of 10 mg/mL) at 3000 rpm on a quartz substrate. Cyclic voltammetry (CV) measurements were performed at a scanning rate of 100 mV/s in a solution of 0.1 M tetrabutylammonium hexafluorophosphate (Bu4NPF6) dissolved in acetonitrile at room temperature using an Autolab PGSTAT30 potentiostat/galvanostat with a standard three-electrode electrochemical cell. A platinum disk working electrode, a Pt wire counter electrode, and an Ag/AgCl reference electrode were used. The sample films were coated on the surface of a platinum disk by the solution-dipping process from THF solutions.

A series of electroluminescence (EL) devices with the configuration of ITO/PEDOT:PSS/polymer (P4 or its H-bonded dendrimers complexes)/BCP/Alq3/LiF/Al were made, where BCP (i.e., 2,9-dimethyl-4,7-diphenyl-1,10-phenanthroline) was used as a hole-blocking layer and Alq3 (i.e., tris(8-hydroxyquinoline)aluminium) was used as an electron-transporting layer. ITO substrates, where glass substrates were coated with indium-tin oxide (ITO) having a sheet resistance of ~20 Ω/square and an effective individual device area of 3.14 mm², were routinely cleaned by ultrasonic treatments in

detergent solutions and diluted water, followed by rinsing with acetone and then ethanol. After drying, ITO substrates were kept in oxygen plasma for 4 min before being loaded into the vacuum chamber. The poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) films were first deposited on pre-cleaned ITO substrates by spin-coating at 6000 rpm for 1 min and subsequently cured in an oven at 120 °C for 1 h. Then, light-emitting polymers (P4 or its H-bonded side-chain dendritic complexes) in THF solutions (10 mg/mL) were spin-coated onto the PEDOT:PSS layer at 4000–5500 rpm. The thicknesses of PEDOT:PSS and LED polymers were measured by an Alfa Step 500 Surface Profiler (Tencor). BCP and Alq3 were thermally deposited at a rate of 1–2 Å/s under a pressure of ~2 × 10^-5 torr in an Ulvac Cryogenic deposition system. Under the same deposition condition, one layer of LiF was thermally deposited as a cathode at a rate of 0.1–0.2 Å/s, which was followed by capping with aluminum. The current-voltage-luminescence characteristics were measured in ambient condition by Keithley 2400 source meter and Newport 1835C optical meter equipped with 818ST silicon photodiode.

Scheme 2.1 Synthetic Routes of H-Acceptor Monomer and Polymers (P1-P5)^a

a Reagents and conditions: (i) NaBH4, MeOH/THF, room temperature, 1 h; (ii) conc.

HCl, dioxane, reflux, 10 h; (iii) P(OEt)3, reflux, 12 h; (iv) pyridine-4-carboxaldehyde, t-BuOK, THF, room temperature, 12 h; (v) 10-bromodecanol, K2CO3, KI, acetone, reflux, 48 h; (vi) 2-methyl-3-butyn-2-ol, Pd(PPh3)2Cl2, CuI, PPh3, Et3N, 70 °C, 12 h;

(vii) KOH, dioxane, reflux, 3 h; (viii) Pd(PPh3)2Cl2, CuI, PPh3, Et3N/THF, 50 °C, overnight; (ix) vinyl methacrylate, 1,3-dichloro-1,1,3,3-tetrabutyldistannoxane, 2,6-di-tert-butyl-4-methylphenol, THF, 50 °C, 48 h; (x) AIBN, THF, 60 °C, 24 h.

2.3.2 Materials

Chemicals and solvents were reagent grades and purchased from Aldrich, ACROS,

TCI, and Lancaster Chemical Co. Tetrahydrofuran (THF) and triethylamine (Et3N) were distilled to keep anhydrous before use. Azobisisobutyronitrile (AIBN) was recrystallized from methanol before use. The other chemicals were used without further purification. Different generations of dendritic H-donors (G1COOH–G3COOH), as shown in Figure 1, used in H-bonded side-chain dendritic complexes were reported in our previous work.⁵⁴ 10-Bromodecanol,⁵⁶ 1,3-dichloro-1,1,3,3-tetrabutyldistannoxane,⁵⁷ and monomer CAZ (M2)⁵⁸ were prepared by following the already published procedures.

4-Iodo-2,5-dimethoxybenyl alcohol (2). To a stirred solution of

4-iodo-2,5-dimethoxybenzaldehyde 1 (8.0 g, 27.4 mmol) in 200 mL of THF/MeOH (1:1), NaBH4 (0.52 g, 13.7 mmol) was added very slowly to react at room temperature.

After 1 h, the solution was cooled to 0 °C by ice bath, acidified with dilute HCl solution, and extracted with ethyl acetate. The resulting materials in organic phase were combined and washed with water. Afterward, the organic extracts were dried over Na2SO4 and evaporated. The purified residue was recrystallized from dichloromethane/2-propanol to give a colorless crystal. Yield: 7.6 g (95%). ¹H NMR (300 MHz, CDCl3): δ (ppm) 7.25 (s, 1H), 6.85 (s, 1H), 4.65 (d, J = 6.3 Hz, 2H), 3.85

(s, 3H), 3.82 (s, 3H), 2.22 (t, J = 6.6 Hz, 1H).

1-Iodo--4-chloromethyl-2,5-dimethoxybenzene (3). To a stirred solution of 2 (7.0

g, 23.8 mmol) in 1,4-dioxane (200 mL), concentrated HCl (20 mL) was added to reflux for 10 h. After the reaction was completed, the crude mixture was added with water. The organic layer was extracted with ethyl acetate, dried over Na2SO4, and evaporated. The residual product was purified by flash column chromatography (silica gel, n-hexane/ethyl acetate 40:1) to give a white solid. Yield: 6.8 g (92%). ¹H NMR (300 MHz, CDCl3): δ (ppm) 7.29 (s, 1H), 6.86 (s, 1H), 4.60 (s, 2H), 3.85 (s, 3H), 3.83 (s, 3H).

4-Iodo-2,5-dimethoxybenzyldiethylphosphonate (4). Compound 3 (6.0 g, 19.2

mmol) was mixed with an excess of triethyl phosphite (20 mL), and the mixture was heated to reflux and reacted for 12 h. The excess of triethyl phosphite was removed under reduced pressure, and the crude product was purified by washing with hot hexane to give a white solid. Yield: 7.2 g (90%). ¹H NMR (300 MHz, CDCl3): δ (ppm) 7.25 (s, 1H), 6.9 (s, 1H), 4.08−3.99 (m, 4H), 3.83 (s, 3H), 3.80 (s, 3H), 3.20 (d, J = 21.6 Hz, 2H), 1.24 (t, 6.9 Hz, 6H).

1-Iodo-2,5-dimethoxy-4-[2-(4-pyridyl)ethenyl]benzene (5). To a solution of

pyridine-4-carboxaldehyde (1.86 g, 17.4 mmol) in anhydrous THF (10 mL), a suspension of 4 (6.0 g, 14.5 mmol) and t-BuOK (2.93 g, 26.1 mmol) in anhydrous

THF (60 mL) under nitrogen was slowly added. The mixture was stirred to react at room temperature for 12 h. After the reaction was completed, it was quenched with water and extracted with dichloromethane. After that, the organic layer was dried over Na2SO4 and evaporated. The crude product was purified by column chromatography (silica gel, dichloromethane/acetone 30:1) to give a yellow solid. Yield: 3.2 g (60%).

1H NMR (300 MHz, CDCl3): δ (ppm) 8.55 (d, J = 4.5 Hz, 2H), 7.57 (d, J = 16.5 Hz, 1H), 7.37 (d, J = 4.5 Hz, 2H), 7.30 (s, 1H), 7.01 (d, J = 16.5 Hz, 1H), 7.00 (s, 1H), 3.88 (s, 3H), 3.84 (s, 3H).

10-(4-Bromophenoxy)-decan-1-ol (6). To a stirred solution of 4-bromophenol (4.0

g, 23.1 mmol) in acetone (200 mL), potassium carbonate (9.6 g, 69.3 mmol), 10-bromodecanol (6.6 g, 27.7 mmol), and a few amounts of potassium iodide (ca. 10 mg) were added to reflux for 48 h under nitrogen. After cooling to room temperature, the solvent was removed under reduced pressure, and the residue was taken up in water and extracted with ethyl acetate. Next, the organic layer was dried over Na2SO4

and evaporated. The crude product was purified by column chromatography (silica gel, n-hexane/ethyl acetate 3:1) to give a white solid. Yield: 6.1 g (80%). ¹H NMR (300 MHz, CDCl3): δ (ppm) 7.33 (d, J = 9.0 Hz, 2H), 6.75 (d, J = 9.0 Hz, 2H), 3.89 (t, J = 6.3 Hz, 2H), 3.62 (t, J = 6.6 Hz, 2H), 1.78−1.69 (m, 2H), 1.59−1.50 (m, 2H), 1.41−1.29 (m, 12H).

4-[4-(10-Hydroxy-decyloxy)-phenyl]-2-methyl-3-butyn-2-ol (7). A solution of 6

(4.0 g, 12.1 mmol), PPh3 (63.1 mg, 0.24 mmol), and CuI (45.6 mg, 0.24 mmol) in dry Et3N (80 mL) was degassed with nitrogen for 5 min. Then, the solution was added with 2-methyl-3-butyn-2-ol (2.0 g, 24.2 mmol) and Pd(PPh3)2Cl2 (84.1 mg, 0.12 mmol) at room temperature, and the reaction mixture was stirred to react at 70 °C for 12 h. The mixture was filtered and the solvent was removed in vacuum. The crude mixture was extracted using ethyl acetate, and the extract was washed with water, dried over Na2SO4, and then evaporated. Subsequently, the crude product was purified by column chromatography (silica gel, n-hexane/ethyl acetate 1:1) to give a light yellow solid. Yield: 3.14 g (78%). ¹H NMR (300 MHz, CDCl3): δ (ppm) 7.31 (d, J = 9.0 Hz, 2H), 6.79 (d, J = 9.0 Hz, 2H), 3.92 (t, J = 6.6 Hz, 2H), 3.62 (t, J = 6.6 Hz, 2H), 1.77−1.70 (m, 2H), 1.60 (s, 6H), 1.58−1.50 (m, 2H), 1.42−1.29 (m, 12H).

4-Ethynyl-1-(10-hydroxydecan-1-yloxy)benzene (8). A stirred solution of 7 (2.5 g,

7.5 mmol) and finely powdered KOH (1.26 g, 22.5 mmol) in 1,4-dioxane (80 mL) was refluxed under nitrogen for 3 h. After cooling to room temperature, the solvent was removed under reduced pressure and the residue was taken up in water, and then the mixture was extracted with ethyl acetate and acidified with 3 N HCl (150 mL).

The organic solution was washed with water, dried over Na2SO4, and then evaporated.

Afterward, the crude product was purified by column chromatography (silica gel,

n-hexane/ethyl acetate 5:1) to give a light yellow solid. Yield: 1.75 g (85%). ¹H NMR (300 MHz, CDCl3): δ (ppm) 7.39 (d, J = 9.0 Hz, 2H), 6.80 (d, J = 9.0 Hz, 2H), 3.92 (t, J = 6.6 Hz, 2H), 3.62 (t, J = 6.6 Hz, 2H), 2.97 (s, 1H), 1.80−1.70 (m, 2H), 1.57−1.50

(m, 2H), 1.42−1.29 (m, 12H).

1-{[4-(10-Hydroxy-decyloxy)-phenyl]-ethynyl}-2,5-dimethoxy-4-[2-(4-pyridyl)e

thenyl]benzene (9). A solution of 5 (1.0 g, 2.72 mmol), 8 (0.78 g, 2.85 mmol), and

PPh3 (14.1 mg, 0.054 mmol) in 80 mL of dry Et3N/THF (1:1) was degassed with nitrogen for 5 min. Then, the solution was added with CuI (10.3 mg, 0.054 mmol) and Pd(PPh3)2Cl2 (19.1 mg, 0.027 mmol) at room temperature, and it was stirred to react at 50 °C overnight. The mixture was filtered and the solvent was removed in vacuum.

The crude mixture was extracted using dichloromethane, and the extract was washed with water, dried over Na2SO4, and then evaporated. After that, the crude product was purified by column chromatography (aluminum oxide, dichloromethane/acetone 40:1) to give a yellow solid. Yield: 1.28 g (92%). ¹H NMR (300 MHz, CDCl3): δ (ppm) 8.56 (d, J = 4.5 Hz, 2H), 7.66 (d, J = 16.5 Hz, 1H), 7.50 (d, J = 9.0 Hz, 2H), 7.39 (d, J

= 4.5 Hz, 2H), 7.11 (s, 1H), 7.04 (d, J = 16.5 Hz, 1H), 7.04 (s, 1H), 6.87 (d, J = 9.0 Hz, 2H), 3.99 (t, J = 6.6 Hz, 2H), 3.97 (s, 3H), 3.89 (s, 3H), 3.62 (t, J = 6.6 Hz, 2H), 1.81−1.72 (m, 2H), 1.57−1.51 (m, 2H), 1.41−1.30 (m, 12H).

1-{[4-(10-Methacryloyloxy-decyloxy)-phenyl]-ethynyl}-2,5-dimethoxy-4-[2-(4-p

yridyl)ethenyl]benzene, PBB (M1). To a Schlenk tube, compound 9 (1.0 g, 1.95

mmol), vinyl methacrylate (0.55 g, 4.88 mmol), 1,3-dichloro-1,1,3,3-tetrabutyldistannoxane (43.12 mg, 0.078 mmol), and 2,6-di-tert-butyl-4-methylphenol (25.78 mg, 0.117 mmol) in dry THF (2 mL) were purged with nitrogen for 15 min at room temperature. The tube was sealed and heated with stirring at 50 °C for 2 days. After cooling to room temperature, the reaction mixture was extracted using dichloromethane, and the extract was washed with water, dried over Na2SO4, and then evaporated. The crude product was purified by column chromatography (aluminum oxide, n-hexane/dichloromethane 1:1) and then washed with hexane to give a light yellow solid. Yield: 0.97 g (85%). ¹H NMR (300 MHz, CDCl3): δ (ppm) 8.57 (d, J = 4.5 Hz, 2H), 7.66 (d, J = 16.5 Hz, 1H), 7.50 (d, J = 9.0 Hz, 2H), 7.39 (d, J = 4.5 Hz, 2H), 7.11 (s, 1H), 7.04 (d, J = 16.5 Hz, 1H), 7.04 (s, 1H), 6.87 (d, J = 9.0 Hz, 2H), 6.10 (s, 1H), 5.55 (s, 1H), 4.14 (t, J = 6.6 Hz, 2H), 3.97 (t, J

= 6.6 Hz, 2H), 3.96 (s, 3H), 3.89 (s, 3H), 3.62 (t, J = 6.6 Hz, 2H), 1.95 (s, 3H), 1.81−1.75 (m, 2H), 1.58−1.53 (m, 2H), 1.42−1.30 (m, 12H). HRMS (EI): calcd for C37H43NO5, 581.3141; found 581.3146. Anal. Calcd for C37H43NO5: C, 76.39; H, 7.45;

N, 2.41. Found: C, 76.15; H, 7.37; N, 2.44.

General Procedure for the Syntheses of Homopolymers and Copolymers

(P1-P5). All polymerization procedures were carried out according to the free radical

polymerization described by the following steps. To a Schlenk tube, 1.5 g of monomers M1, M2, or the mixture of M1 and M2 were dissolved in dry THF (7.5 mL) with 20 wt% of monomer concentration and AIBN (2 mol% of total monomer concentration) as an initiator. The solution was degassed by three freeze-pump-thaw cycles and then sealed off. The reaction mixture was stirred and heated at 60 °C for 24 h. After polymerization, the polymer was precipitated into diethyl ether. Then, the precipitated polymer was collected, washed with diethyl ether, and dried under high vacuum.

P1 (HPBB). ¹H NMR (300 MHz, DMSO-d6): δ (ppm) 8.44 (br, 2H), 7.53−6.77 (br, 10H), 3.80 (br, 10H), 1.66−1.24 (br, 21H).

P2 (PBB-CAZ1). ¹H NMR (300 MHz, DMSO-d6): δ (ppm) 8.46 (br, 2H), 7.97−6.75 (br, 18H), 3.88 (br, 14H), 1.43−1.08 (br, 26H).

P3 (PBB-CAZ5). ¹H NMR (300 MHz, DMSO-d6): δ (ppm) 8.48 (br, 2H), 7.92−6.76 (br, 50H), 4.33−3.83 (br, 30H), 1.43−-0.06 (br, 46H).

P4 (PBB-CAZ9). ¹H NMR (300 MHz, DMSO-d6): δ (ppm) 8.48 (br, 2H), 7.88−6.76 (br, 80H), 4.34−3.83 (br, 45H), 1.43−-0.16 (br, 65H).

P5 (HCAZ). ¹H NMR (300 MHz, DMSO-d6): δ (ppm) 7.89 (br, 2H), 7.32−7.00 (br, 6H), 4.34−3.94 (br, 4H), 0.99−-0.15 (br, 5H).

Sample Preparation of Supramolecular Side-Chain Copolymers (i.e.,

H-Bonded Side-Chain Dendritic Complexes). H-bonded side-chain dendritic

complexes were made of appropriate (fully H-bonded) molar ratios of H-acceptor copolymers (P3 and P4) and dendritic H-donors (G1COOH–G3COOH) in THF solutions, and then the solvent was removed by slow evaporation and followed by drying under vacuum at 50 °C.

2.4 Results and Discussion

2.4.1 Syntheses and Characterization of Polymers

The syntheticroutes of monomer PBB (M1) and polymers P1-P5 are shown in Scheme 1. The starting material 1 (i.e., 4-iodo-2,5-dimethoxybenzaldehyde) was synthesized by following a reported procedure⁵⁹ via iodination of 2,5-dimethoxybenzaldehyde with iodine and silver nitrate in the presence of methanol.

The aldehyde group of compound 1 was further reduced to a benzyl alcohol and then was transformed into a benzyl chloride group with hydrochloric acid in the presence of 1,4-dioxane to givecompound 3, which was converted to the corresponding phosphonate ester 4 by Michaelis-Arbuzov reaction under the triethyl phosphite treatment with a yield of 90%.⁶⁰ Compound 5 was prepared by means of Horner-Wadsworth-Emmons (HWE) olefination reaction between compound 4 and pyridine-4-carboxaldehyde using potassium tert-butoxide as a base in THF to give 60% yield.⁶¹ Compound 6 in 80% yield was obtained by reaction of 4-bromophenol

with 10-bromodecanol under Williamson etherification condition (K2CO3/acetone).

The latter Sonogashira (Pd-catalyzed) coupling reaction of compound 6 with 2-methyl-3-butyn-2-ol afforded compound 7 in the presence of a catalytic amount (1 mol %) of Pd(PPh3)2Cl2 in Et3N with a yield of 78%,⁶² which was then deprotected with KOH/1,4-dioxane to acquire compound 8 in 85% yield. Subsequently, the three-conjugated rings of compound 9 with a yield of 92% was prepared through a second Sonogashira coupling reaction between compounds 8 and 5 in Et3N/THF (1:1).

Finally, monomer PBB (M1) with a high yield of 85% was obtained by transesterification reaction⁶³ between compound 9 and an excess amount (2.5 equiv) of vinyl methacrylate in the presence of a higher concentration of 1,3-dichloro-1,1,3,3-tetrabutyldistannoxane as a catalyst and 2,6-di-tert-butyl-4-methylphenol as an inhibitor in THF. The yield is much better than that reported⁶⁴ by our previous esterification reaction. The final chemical structure of monomer PBB (M1) was confirmed by ¹H NMR spectroscopy, HRMS, and elemental analysis (see Experimental Section and Appendix A1).

The polymerization reactions with good yields (ranging 73-88%) were carried out

The polymerization reactions with good yields (ranging 73-88%) were carried out