Synthesis and characterization of novel jacketed polymers and investigation of their self assembly and application

Another way is to force the main chain to take a rigid conformation through the attachment of many side groups on the polymer backbone.. The concept of jacketed polymers was first propos

Chapter 2 Part1 Synthesis and characterization of novel jacketed

polymers

2.1.1 Introduction

The development of synthetic materials with controlled nanostructures is a fascinating area of scientific research in science and engineering The driving forces arise from areas such as biological, microelectronic material science and development of sensing, actuating, and control devices with components in the nano- or microscale 1 Various chemical synthesis and physical manipulation techniques are under development to meet the challenge of architectural control in nanoscale Examples include electrodepositing metals inside the pores of commercial membrane, growing polymers in the cavities of inorganic clay and sieves2-3, or self-assembly methods to develop nanostructured materials

Self-assembly of molecules through non-covalent forces including hydrophobic and hydrophilic effects, electrostatic interactions, hydrogen bonding, microphase segregation, and shape of molecules have significant potential for creating such supramolecular structures 4-5 It is relatively easy to self-assemble macromolecules into ordered morphologies covering several length-scales6

There is growing interest in the precise control of the order of macromolecules in the nano-scale through self-assembly, which may be used in improvement of the material properties, lithographic techniques, chemical sensors and so on The order of macromolecules depends largely on the primary structure and the segmental interaction of polymers It is well known that the chain stiffness of polymers offers a method of controlling the spatial arrangement of a polymer chain This stiffness may contribute to the formation of supramolecular structures and is used to demonstrate the correlation between chemical structure and performance in application There are usually two ways to make the chain stiff In one method, the main chain of the

polymer is made of rigid, interconnected groups For example, many rigid - coil block copolymers with helical rods, mesogenic rods, and conjugated rods, have been reported7 Another way is to force the main chain to take a rigid conformation through the attachment of many side groups on the polymer backbone These polymers can be considered as jacketed polymers and used as building blocks can provide valid access

to the construction of interesting architectures5-9

The concept of jacketed polymers was first proposed by Zhou et al.9-11 to describe a new type of liquid crystalline polymers in which the mesogenic units were attached laterally to the main chain via a direct connection or via short spacers The results of X-ray diffraction9 revealed that the rigid side groups spiral around the backbone of the mesogen - jacketed polymers and the morphological study showed that the polymers have a branded texture similar to that of the semi - rigid main - chain liquid crystalline polymers The authors suggested that the jacketed polymer’s main chain backbone was forced to take a stiffen conformation due to the steric repulsion between the densely grafted side chains and excluded volume effects These jacketed polymers often show liquid crystalline properties and allow the creation of highly ordered architecture

Polymacromonomers can also be considered as a kind of jacketed polymers, in which the side group is a flexible polymer chain Schmidt’s group12 reported the synthesis of polymacromonomers based on polystyrene side chains and a methacrylate main chain Such polymers adopt the conformation of a cylindrical brush The study showed that the methacrylate main chain exhibits extremely high chain stiffness in the order of

100 nm for the Kuhn statistical segment length, and it depends on the length of the side chains used

Percec et al synthesized a series of monodendron - jacketed polymers5, 7, 8, 13-15 They demonstrated a rational control of polymer conformation through self-assembly of monodendritic side - groups At low degree of polymerization (DP), the conical monodendrons assembled to produce a spherical polymer with random - coil backbone conformation At high DP, the monodendritic units changed to give a cylindrical polymer with an extended backbone This correlation between polymer conformation and DP is opposite to that seen in most synthetic and natural macromolecules This may provide a new method for the design of organized supramolecular materials for nanotechnology, functional films and fibers, and molecular devices

The Schluter group16 have reported the synthesis of poly(p-phenylene) substituted with monodendron side groups, in which the main chain is rigid and of sterically crowded The scanning tunneling microscopy (STM) investigations showed that the polymers take rigid rod type conformation

Recent years have seen much progress in the use of rigid components in polymers as building blocks to form interesting supramolecular structures and their intriguing properties are extensively discussed9,10,13 Generally, the rigid components are incorporated on the main chain of the polymers Further studies are required to understand the properties of jacketed polymers in which the main chain is sterically crowded with laterally attached rigid side chains17-19

Here we report the synthesis of a series of novel jacketed polymers Constitutes on the polymer backbone are designed to incorporate strong electrostatic, weak Van der Waals interactions, and shape effects, to control the self-assembly of polymer chains

in the lattice The novel polymers were characterized with GPC, DSC, TGA, FTIR,

and NMR This work show characterization about the rigid side chain organization and provide a new method to design novel macromolecular building blocks

2.1.2 Experimental section

2.1.2.1 Materials and reagents

All reagents and solvents were obtained from commercial supplies and used without further purification unless noted otherwise Tetrahydrofuran (THF) was distilled over sodium and benzophenone under N2 atmosphere N, N-dimethylformamide(DMF) was dried with 4 Å molecular sieves (Aldrich) Flash column chromatography was performed using silica gel (60-120 mesh, Aldrich)

2.1.2.2 Instrumentation

Fourier transform infrared (FT-IR) spectra were obtained using a Perkin-Elmer 1616 FT-IR spectrometer as KBr mulls 1H NMR, 13C NMR spectra were recorded on a Bruker ACF 300 MHz spectrometer Thermogravimetric analyses (TGA) and differential scanning calorimetry (DSC) traces were recorded using a TA-SDT2960 and a TA-DSC 2920 at a heating rate of 10 °C min-1 under N2 environment The XRD patterns were recorded on an X-ray powder diffractometer with a graphite monochromator using Cu-Kα radiation with a wavelength of 1.54 Å at room temperature (scanning rate: 0.05 o/s; scan range 1.5-30o) Gel permeation chromatographic (GPC) analyses were conducted with a Waters 2696 separation module equipped with a Water 410 differential refractometer HPLC system and Waters Styragel HR 4E columns using THF as eluent and polystyrene as standard Melting points (Mp) were obtained on a BÜCHI Melting Point B-540 apparatus and are uncorrected

2.1.2.3 Synthesis

Poly(5’-dodecyloxy-[1, 1’; 4’, 1’’]terphenyl-2’-yl methacrylate) (7a),

poly(5’’-dodecyloxy [1, 4’; 1’, 1’’; 4’’, 1’’’; 4’’’, 1’’’’] quinquephenyl-2’’-yl methacrylate )

(7b), poly(1, 3-bis (5'-dodecyloxy [1, 1'; 4', 1''] terphenyl-2'-yloxy) propan-2-yl methacrylate) (10a) and poly (1, 3-bis (5''-dodecyloxy [1, 4'; 1', 1''; 4'', 1'''; 4''', 1''''] quinquephenyl-2''-yloxy) propan-2-yl methacrylate) (10b)were synthesized using the

following route shown in Scheme 2.1.1:

Synthesis of monomers and polymers

2,5-dibromohydroquinone (1)

In a 1L round-bottom flask containing a teflon stir bar was placed 110.2 g hydroquinone (1 mol) and 200 ml glacial acetic acid A solution of 102.7 ml Br2 (0.99 mol) in 150 ml glacial acetic acid was added dropwise to the flask After finish the addition, the reaction mixture was kept stirring at RT for 12 h, then poured into water The precipitate was recrystallized in glacial acetic acid to yield a white crystalline solid Yield: 189.4g (71 %) 1H NMR (300MHz, DMSO-d6, δ ppm): 7.16 (s, Ar-H, 2 H), 5.16 (s, Ar-OH, 2 H)

H2C C

CH3

C O RO AIBN

H2C CCH3

C O O

H2

C CCH3

C O O

OR OR

H2C CCH3

C O Cl

OBn

OC12 H25

Br Br

OH

OC12 H25

Br Br

Glacid acetic acid

NaOH/Ethanol 12-bromoldodecane

K2CO3/Ethanol Benzylbromide

2,5-dibromo-4-dodecyloxyphenol (2)

53.6 g of compound 1 (0.2 mol), 12 g NaOH (0.3 mol) and 500 ml absolute ethanol

were added to a 1 L round-bottom flask, purged with N2 for 20 min, heated to 50-60

°C under N2 atmosphere and 46 ml bromododecane (0.19 mol) was added dropwise to the solution After finishing the addition, the reaction mixture was stirred for 18 h The reaction mixture was allowed to cool to RT and then filtered The solution was concentrated and poured into dilute HCl The precipitate was recrystallized in hexane

to yield a white powder Yield: 26.9 g (32.5 %) 1H NMR (300 MHz, CDCl3, δ ppm): 7.24 (s, Ar-H, 1 H), 6.90 (s, Ar-H, 1 H), 5.15 (s, Ar-OH, 1 H), 3.93 (t, J = 6.4 Hz, ArO-CH2-, 2 H), 1.80 (p, J = 6.8 Hz, R(O)-CH2-,2 H), 1.27 (b, -CH2-, 18 H), 0.8 (t, J

= 6.0 Hz, -CH3, 3 H) 13C NMR (75.4 MHz, CDCl3, δ ppm): 150.0, 120.2, 118.4, 116.2, 112.5, 108 (ArC), 70.3 (O-C-), 31.8, 29.6, 29.5, 29.4, 29.2,29.1, 28.9, 23.4, 22.6, 13.9 (-CH2-), 11.3 (-CH3) MS (EI): m/z: 438.2, 436.2 Mp:66 °C

1-benzyloxy-2, 5-dibromo-4-dodecyloxy benzene (3)

In a 1L round-bottom flask was placed 21.8 g compound 2 (0.05 mol), 10.4 g K2CO3

(0.075 mol) and 400 ml absolute ethanol The mixture was purged with N2 for 20 min, heated to 75°C under the atmosphere of nitrogen A solution of benzyl bromide 11.9

ml (0.1 mol) in 50 ml absolute ethanol was added dropwise After finishing the addition, the reaction mixture was kept stirring for 18 h, cooled to RT and filtered The solution was concentrated and poured into water The precipitate was recrystallized in ethanol to yield a white powder Yield: 20.5 g (77.9 %) 1H NMR (300 MHz, CDCl3, δ ppm): 7.47 - 7.32 (m, Ar-H, 5 H), 7.16 (s, Ar-H, 1 H), 7.11 (s, Ar-H, 1 H), 5.07 (s, ArO-CH2-, 2 H), 3.95 (t, J = 6.6 Hz, ArO-CH2-, 2 H), 1.83 (q, J = 6.8 Hz, 2H), 1.27 (b, -CH2-, 18 H), 0.89 (t, J = 6.0 Hz, -CH3, 3H) 13C NMR (75.4 MHz, CDCl3, δ ppm): 150.5, 149.5, 136.2, 128.5, 128.0, 127.2, 119.3, 118.2, 111.5,

111.0 (ArC), 72.0, 70.1 (O-CH-), 32.8, 29.6, 29.4, 29.3, 29.2, 29.0, 25.8, 22.6, 14.0

(-CH2-), 11.3 (-CH3) MS (EI): m/z: 526.1, 524.2 Mp: 152 °C

2’-Benzyloxy-5’-dodecyloxy [1, 1’; 4’, 1’’] terphenyl (4a) 20

A 500 ml round-bottomed flask equipped with a condenser was charged with 10.52 g

compound 3 (20 mmol), 7.32 g phenyl boronic acid (60 mmol), 80 ml toluene, 20 ml

methanol and 100 ml 2M sodium carbonate solution The mixture was degassed before the catalyst tetrakis(triphenylphosphine) palladium (1 g, 5 mol%) was added in dark under argon atmosphere The reaction mixture was heated to 100 °C for 48 h, cooled to RT and filtered The liquid layer was separated with a separation funnel, and the aqueous layer was extracted with toluene (100 ml × 2) The toluene layer was combined and washed with 3× 100 ml water and dried over MgSO4 The solvent was then removed under reduced pressure, and the resulting crude product was purified using column chromatography on silica gel column with hexane and dichloromethane (4:1) as the eluant Yield: 4.6g (44.3%) 1H NMR (300 MHz, CDCl3, δ ppm): 7.65 - 7.29 (m, ArH, 15 H), 7.06 (s, Ar-H, 1 H), 7.00 (s, Ar-H, 1 H), 4.99 (s, ArO-CH2-, 2H), 3.92 (t, J = 6.5 Hz, ArO-CH2-, 2 H), 1.68 (p, J = 6.5 Hz, R(O)-CH2-, 2 H), 1.26 (b, -CH2-, 18 H), 0.8 (t, J = 6.3 Hz, 3 H) 13C NMR (75.4 MHz, CDCl3, δ ppm): 150.7, 149.7, 149.5, 148.3, 148.2, 148.1, 138.3, 138.2, 131.4, 130.7, 129.5, 129.4, 128.3, 127.9, 127.8, 127.5, 127.3, 127.3, 127.1, 126.9, 126.8, 117.4, 116.1 (ArC), 77.8, 69.4(O-CH-), 31.8, 29.6, 29.5, 29.5, 29.3, 29.2, 28.9, 25.9, 22.6, 14.0 (-CH2-), 12.5 (-

CH3) MS (EI): m/z: 520.6, 429.4, 352.3, 261.1, 215.2, 183.1,83.0 Mp: 76 °C

2’’-Benzyloxy-5’’-dodecyloxy [1, 4’; 1’, 1’’; 4’’, 1’’’; 4’’’, 1’’’’] quinquephenyl (4b)

Compound 4b was synthesized according to the procedure described for the synthesis

of 4a Yield: 4.5 g (33.6 %) 1HNMR (300 MHz, CDCl3, δ ppm): 7.72 - 7.30 (m,

Ar-H, 23 H), 7.26 (s, Ar-Ar-H, 1 H), 7.07 (s, Ar-Ar-H, 1 H), 5.06 (s, ArO-CH2-, 2 H), 3.98 (t, J

= 6.3 Hz, ArO-CH2-, 2H), 1.73 (p, J = 6.8 Hz, R(O)-CH2-, 2H), 1.24 (b, -CH2-,18 H), 0.87 (t, J = 6.0 Hz, -CH3, 3H) 13C NMR (75.4 MHz, CDCl3, δ ppm): 150.8, 149.8, 140.9, 139.8, 139.7, 137.3, 130.9, 130.3, 129.9, 129.8, 128.7, 128.3, 127.6, 127.2, 128.7, 128.7, 128.3, 127.6, 127.1, 127.0, 126.9, 126.7, 126.6, 117.3, 115.9, 98.1 (ArC), 71.9, 69.5 (O-CH), 31.8, 29.6, 29.6, 29.5, 29.3, 29.2, 26.0, 22.6, 14.0 (-CH2-), 11.3 (-CH3) MS (ESI): m/z: 672.4, 581.6, 413.2, 306.2, 289.2, 228.2, 153.1 Mp: 143

°C

5’-Dodecyloxy [1, 1’, 4’, 1’’] terphenyl-2’-ol (5a) 21

To a 100 ml round-bottom flask containing 10% Pd/C (2.5 g) in 50 ml THF was

added 4a (2.6 g, 5 mmol) The flask was charged with nitrogen, and a balloon filled

with H2 was fitted to the flask The nitrogen was briefly evacuated from the flask, and

H2 was charged above the solution The mixture was stirred for 24 h at ambient temperature and filtered through a glass frit containing a small layer of celite powder After the solid was washed with THF (3 × 25 ml), the organic fractions were combined and the excess solvent was removed under reduced pressure to yield a white powder Yield: 2.02 g (93 %) 1H NMR (300MHz, CDCl3, δ ppm): 7.42 - 7.40 (m, Ar-H, 6 H), 7.38 - 7.32 (m, Ar-H, 4 H), 4.90 (s, Ar-OH, 1H), 3.88 (t, J = 6.2 Hz, ArO-CH2-, 2 H), 1.67 (p, J = 6.8 Hz, R(O)-CH2-, 2 H), 1.25 (b, -CH2-, 18 H), 0.88 (t,

J = 6.6 Hz, 3 H) 13C NMR (75.4 MHz, CDCl3, δ ppm): 150.1, 146.3, 142.7, 140.7, 137.9, 137.2, 132.0, 131.8, 131.7, 131.2, 129.4, 129.1, 128.9, 127.8, 127.3, 126.9, 118.0, 115.3, 98.1 (ArC), 69.6 (O-CH-), 31.8, 29.6, 29.5, 29.5, 29.3, 29.2, 29.2, 25.9, 22.6, 14.1 (-CH2-), 13.9 (-CH3) MS (ESI): m/z: 430.2, 262.2, 149.0, 66.0 Mp: 61 °C

5’’-Dodecyloxy [1, 4’; 1’, 1’’; 4’’, 1’’’; 4’’’, 1’’’’] quinquephenyl-2’’-ol (5b)

Compound 5b was synthesized according to the procedure described for the synthesis

of 5a From 4.3 g of 4b was obtained 3.5 g of white powder Yield: 3.4 g (93 %) 1H NMR (300 MHz, CDCl3, δ ppm): 7.73 - 7.46 (m, Ar-H, 18 H), 7.26 (s, Ar-H, 1 H), 7.07 (s, Ar-H, 1 H), 5.10 (s, Ar-OH, 1 H), 3.94 (t, J = 6.5 Hz, ArO-CH2-, 2 H), 1.72 (p, J = 6.7 Hz, -CH2-, 2 H), 1.24 (b, -CH2- 18 H), 0.89 (t, J= 4.0 Hz, 3 H) 13C NMR (75.4 MHz, CDCl3, δ ppm): 150.3, 146.3, 140.9, 129.8, 129.2, 128.8, 128.7, 127.8, 127.5, 127.1, 127.0 126.9, 126.5, 120.6, 118.8, 115.3, 98.1, 89.6 (ArC), 69.6 (O-CH), 31.8, 29.6, 29.5, 29.5, 29.3, 29.2, 28.8, 27.6, 26.0, 22.6 (-CH2-), 13.9 (-CH3) MS (ESI): m/z: 582.4, 414.3 Mp: 146 °C

5’-Dodecyloxy [1, 1’, 4’, 1’’] terphenyl-2’-yl methacrylate (6a)

Triethylamine (1.5 ml, 11 mmol) and compound 5a (2.15 g, 5 mmol) were dissolved

in a 50 ml dry THF placed in a 100 ml round-bottom flask This solution was cooled with ice, and a solution of methacryloyl chloride (1 ml, 10 mmol) in 4 ml THF was added dropwise After finishing the addition, the reaction mixture was stirred at room temperature for 4 hr, filtered and the volatile components were removed under reduced pressure The resulting crude product was dissolved in dichloromethane, washed with sodium bicarbonate solution and followed by water (3 × 50 ml), and the organic layer was dried over anhydrous magnesium sulfate Filtered the solution, and the solvent was removed under reduced pressure to yield the monomer Yield: 1.7 g (68 %) 1H NMR (300 MHz, CDCl3, δ ppm): 7.65 -7.28 (m, Ar-H, 10 H), 7.21(s, Ar-

H, 1 H), 7.03 (s, Ar-H, 1 H), 6.22 (s, CH2=C-, 1 H), 5.65 (s, CH2=C-, 1 H), 4.02 (t, J = 6.4 Hz, ArO-CH2-, 2 H), 2.0 (s, =C-CH3, 3 H), 1.68 (p, J = 6.9 Hz, R(O)-CH2-, 2 H), 1.25 (b, -CH2-, 18 H), 0.90 (t, J = 6.6 Hz, -CH3, 3 H) 13C NMR (75.4 MHz, CDCl3, δ ppm): 171 (C=O), 153.8, 141.2, 137.1, 136.6, 135.8, 134.6, 134.5, 133.8, 130.6, 129.3, 128.9, 128.8, 128.6, 128,6, 128.5, 126.6, 124.6, 114.5, (ArC, C=C), 62.9 (O-

CH-), 31.8, 29.6, 29.5, 29.4, 29.1, 29.0, 26.0, 25.9, 25.5, 21.1 (-CH2-), 18.2, 14.0

(-CH3) MS (EI): m/z: 498.5, 430.5, 330.3, 289.2, 261.2 Mp: 45 °C

5’’-Dodecyloxy [1, 4’; 1’, 1’’; 4’’, 1’’’; 4’’’, 1’’’’] quinquephenyl-2’’-yl methacrylate (6b)

Monomer 6b was synthesized according to the procedure described for the synthesis

of 6a From 2.2 g (3 mmol) of compound 5b was obtained 1.28 g of 6b Yield: 1.28 g

(64.1 %) 1H NMR (300 MHz, CDCl3, δ ppm): 7.73 - 7.36 (m, Ar-H, 18 H), 7.24 (s, Ar-H, 1 H), 7.04 (s, Ar-H, 1 H), 6.18 (s, CH2=C-, 1 H), 5.65 (s, CH2=C-, 1 H), 3.98 (t, J= 6.5 Hz, ArO-CH2-, 2 H), 2.02 (s, C=C-CH3, 3 H), 1.73 (p, J = 6.6 Hz, R(O)-CH2-,

2 H), 1,26 (b, -CH2-, 18 H), 0.87 (t, J = 6.7 Hz, -CH3, 3H) 13C NMR (75.4 MHz, CDCl3, δ ppm): 166 (C=O), 150.3, 146.3, 140.9, 129.8, 129.1, 128.8, 128.7, 127.8, 127.5, 127.1, 127.0 126.9, 126.5, 120.7, 118.7, 115.2, 98.1, 89.6 (ArC), 69.4 (O-CH-),31.8, 29.6, 29.5, 29.4, 29.2, 29.1, 28.7, 27.5, 26.0, 22.6 (-CH2), 18.4, 14.0 (-CH3)

MS (EI): m/z: 650.4, 581.4, 482.2, 413.1, 69.1 Mp: 115 °C

Poly(5’-dodecyloxy [1, 1’, 4’, 1’’] terphenyl-2’-yl methacrylate) (7a)

Monomer 6a (1.5 g, 3 mmol) and 2, 2’-azobisisobutyronitrile (AIBN) (0.02 g, 0.01

mmol, 0.3 mol%) were dissolved in 20 ml dry THF Purged with nitrogen for 30 min,

heated to 70-80 ºC and stirred for 18 h under nitrogen flush The polymer 7a was

isolated via precipitation from methanol Yield: 1.22 g (81 %) 1H NMR (300MHz, CDCl3, δ ppm): 7.66 - 7.32(b, Ar-H, 10 H), 7.07-7.00(b, Ar-H, 2 H), 3.95(b, ArO-

CH2- 2 H), 1.75-1.65(b, R(O)-CH2-, 4 H), 1,24(b, -CH2-, 18 H), 0.87(b, -CH3, 6 H) FT-IR (KBr, cm-1): 3030 (ArH stretching), 2928 (-CH2- stretching), 1724 (ester C=O stretching), 1515, 1478, 1390, 1370 (Ar, C=C stretching), 1268, 1165, 1020 (C-O-C stretching)