Synthesis and characterization of novel jacketed polymers and investigation of their self assembly and application 4

Chapter 4 Synthesis and characterization of novel polymeric complexes with side-chain pyrimidine groups... Here we report the structure properties investigation of polymers poly 4-dodecy

Chapter 4

Synthesis and characterization of novel polymeric complexes with side-chain pyrimidine groups

4.1 Introduction

Polymeric complexes in the solid state are considered to be promising for the development of smart materials that are characterized by the formation of supramolecular structures through self-assembly process Self-assembled materials formed by the noncovalent bonds have attracted much interest owing to easy synthesis and high processibility 1,2

Complexes between polymers and amphiphilic surfactants through noncovalent bonding offer novel properties and phase structures not possessed by the individual components

In the solid state, the complexes self-assemble into ordered structures via a delicate balance of attractive and repulsive interactions Dynamic molecular complexes can be prepared via the self-assembly process using non-covalent bonding For example, hydrogen-bonded liquid crystal polymers, which include main-chain, side-chain, and network structures, have been prepared by the self-organization of polymers and small molecules The noncovalent interactions play a key role in the formation of assembled structures, and possibility to design novel functional materials 3

Kato et al reported first supramolecular hydrogen bonded liquid crystalline polymeric complexes4, in which polyacrylate with a benzoic acid moiety on the side chain was complexed with stilbazole ester moiety The complexes showed a nematic phase up to

252 °C Ionic interaction, metal coordination and hydrogen bonding interactions were employed to form ordered nanostructures5-10

Kato et al also reported complexes formed via poly(vinylpyridine) and nonadecylphenol exhibited layered smectic structures due to the microsegregation of different amphiphilic groups.11 Antonietti et al have studied polyelectrolyte-surfactant (eg poly(n-

alkyltrimethylammonium styrene sulfonate) complexes which show an ordered lamellar structure with ionic and nonpolar alkyl layers organized in an alternating layers12-13 Ikkala et al reported the formation of hierarchical structures from a complex prepared from polystyrene-block-poly(4-vinylpyridine), pentadecylphenol, and methane sulfonic acid14-15 Two structural changes occurred in the lattice: microseparation of block copolymers and complexation as a function of temperatures cause drastic electrical conductivity changes By tailoring the relative ratio of the components, lamellar and cylindrical structures were obtained14-20 Hollow cylinders were formed in a glassy rigid

PS medium from polystyrene-block-poly(4-vinylpyridine), and pentadecylphenol Part of the supramolecular template (pentadecylphenol) can be conveniently removed after the structure has been formed17-19

In general, when there is a good balance between attractive and repulsive interactions, microphase-segregation is induced in the system The phase behaviors of polymer-amphiphilic systems can be modified through tailoring the attractive and repulsive interactions in the systems This can be realized via modifying the length of the alkyl chain and change of the interaction of hydrogen bonding Here we report the structure properties investigation of polymers poly (4-dodecyloxy-2,5- bis(pyrimidin-5-yl)-phenyl-1-yl methacrylate), poly(4-pyrimidin-5-yl-phenyl methacrylate) with the pyrimidine group as the base functional group, study the complexes formed via host polymers with pyrimidine groups and alkyl sulfonic acid and investigate their self-assembling properties

in the solid state

4.2 Experimental section

4.2.1 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 molecular sieves (4 Å, Aldrich) Flash column chromatography was performed using 60-120 mesh silica gel (Aldrich) Dibenzoyl peroxide (BPO) was recrystallized from chloroform-methanol solution as glistening crystals, and used as initiators for

polymerization

4.2.2 Instrumentation

Fourier transform infrared (IR) spectra were obtained using a Perkin-Elmer 1616

FT-IR spectrophotometer as KBr discs 1H NMR, 13C NMR spectra were recorded on a Bruker ACF 300 MHz spectrometer Differential scanning calorimetry (DSC) and thermogravimetric analyses (TGA) were recorded using a TA-SDT2960 and a TA-DSC

2920 at a heating rate of 10 °C min-1 under N2 environment Gel permeation chromatographic (GPC) analysis 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 The XRD patterns were recorded on a powder diffractometer with a graphite monochromator using 1.54 Å

Cu Kα wavelength at room temperature (scan rate: 0.05 o/s; scan range 1.5-30 o) A Zeiss Axiolab POM equipped with a Linkam LTS 350 hot stage was used to observe anisotropic textures All AFM images were recorded with a Digital Instruments (DI) Multimode SPM IIIa system in contact mode using square pyramid Si3N4 probes (25 °C,

in air) All films were prepared using spin coating of polymer solutions in THF (0.5 mg/ml) onto a glass slide at 2000 rpm Melting points (Mp) were obtained on a BÜCHI Melting Point B-540 apparatus and are uncorrected

4.2.3 Synthesis of the host polymer

The host polymers: polypyrimidin-5-yl-phenyl methacrylate) (P1), poly Dodecyloxy-2,5-di(pyridin-5-yl)phenyl-1-yl methacrylate) (P2), poly (4-Dodecyloxy- 2,5-di(pyrimidin-5-yl)phenyl-1-yl methacrylate) (P3) were synthesized according to

O O

N O

OC 12 H 25

O n

P1

BPO/THF

N

N N

N O

OC12H25O

Pd(PPh3)4Toluene/EtOH/2M K2CO3

N N

OBn

C12H25O

N N

O O

N N

(75.4 MHz, DMSO-d6, δ ppm) 157.5, 136.6, 132.1, 128.4, 127.8, 127.6, 117.1, 112.0 C), 69.4(O-CH2-Ar) MS (EI): m/z: 264.0, 262.0, 91.1, 65.0 Mp: 64 °C

(Ar-4-Benzyloxy-phenyl-2-boronic acid (3)

In a 500 ml round-bottom flask with a stirring bar was placed 10.5 g (40 mmol) of benzyloxy-4-bromobenzene and 150 ml dry THF The solution was cooled to - 78 °C and then a 1.6 M solution of butyllithium in hexanes (75 ml, 0.12 mol) was added slowly under a nitrogen atmosphere The solution was stirred at -78 °C for another 2 h, followed

1-by the dropwise addition of triisopropylborate (50 ml, 0.18 mol) After complete addition, the mixture was warmed to RT, stirred overnight, and mixed with 200 ml of deionized water The organic phase was collected and dried with MgSO4 and filtered, and the solvent was removed under reduced pressure The resulted light yellow solid was recrystallized from acetone Yield: 8.4 g (92.2 %) 1H NMR (300 MHz, DMSO-d6, δ ppm) 7.83 (s, B-OH, 2 H), 7.73-6.95 (m, Ar-H, 9 H), 5.11 (s, Ar-CH2-O, 2 H) 13C NMR (75.4 MHz, DMSO-d6, δ ppm) 161.5, 141.6, 132.1, 128.4, 127.8, 127.6, 117.1, 112.0 (Ar-C), 68.2 (O-CH2-Ar) MS (EI): m/z: 228.2, 184.2, 91.1 Mp: 185 °C

5-(4-Benzyloxyphenyl) pyrimidine (4)

A 250 ml round bottom flask equipped with a condenser was charged with 4.56 g (20 mmol) of 4-benzyloxy-phenyl-2-boronic acid and 2.12 g (13.3 mmol) of 5-bromo-pyrimidine, 60 ml toluene, 20 ml methanol and 60 ml sodium carbonate (2M) The mixture was degassed via 3 cycles, before the catalyst of 0.2g tetrakis (triphenylphosphine) palladium (2 mol%) was added in dark under argon atmosphere The flask was degassed once more and charged with argon The reaction mixture was heated to 100 °C for 48h, before being allowed to cool to RT and then 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 a silica gel using hexane and ethyl acetate (2:1) as the eluant Yield: 2.5g (44.3 %) 1H NMR (300 MHz, DMSO-d6, δ ppm) 9.2 - 9.1 (m, ArH, 3 H), 7.75 - 7.12 (m, Ar-H, 9 H), 5.19 (s, Ar-CH2-O,

2 H) 13C NMR (75.4 MHz, DMSO-d6, δ ppm) 158.5, 157.5, 154.0, 136.6, 132.7, 128.4, 128.1, 127.8, 127.6, 126.0, 115.0 (Ar-C), 69.3(O-CH2-Ar) MS (EI): m/z: 262.1, 172.1, 91.1 Mp: 295 °C

4-(Pyrimidin-5-yl) phenol (5)

To a 100 ml round-bottomed flask containing 10 % Pd/C (1.0g) in 50 ml THF was added 5-(4-benzyloxyphenyl) pyrimidine (2.17 g, 8 mmol) The flask was charged with nitrogen, and a balloon filled with H2 was fitted to the flask The nitrogen gas was briefly evacuated from the flask, and the H2 gas was charged above the solution The reaction mixture was stirred for 24 h at ambient temperature and then filtered through a glass frit containing a small layer of celite powder After the solid was washed with THF (3 × 25 ml), the organic phrases were combined and the solvent was then removed with a rotary evaporator to yield a light yellow solid The resulting crude product was purified by column chromatography on a silica gel column using hexane and ethyl acetate (1:4) as the eluant Yield: 1.4 g (98.2 %) 1H NMR (300 MHz, DMSO-d6, δ ppm) 9.10 - 9.04 (m, ArH, 3 H), 7.63 (d, J = 8.4 Hz, Ar H), 6.90 (d, J = 8.2 Hz, Ar H), 6.87 (b, O-H, 1 H) 13C NMR (75.4 MHz, DMSO-d6, δ ppm) 148.8, 136.6, 128.4, 127.8, 127.6, 119.6, 108.3(Ar-C) MS (EI): m/z: 172.1, 118.1, 91.1 Mp: 116 °C

4-(Pyrimidin-5-ylphenyl) methacrylate (6)

Triethylamine (2.5 ml, 17.9 mmol) and 4-(pyrimidin-5-yl) phenol (1.0 g, 5.8 mmol) were dissolved in 30 ml dry THF placed in a 100 ml round-bottom flask This solution was cooled to 0 °C, and added a solution of methacryloyl chloride (1.2 ml, 12 mmol) in 4 ml THF After finishing the addition, the reaction mixture was warmed to room temperature and stirred 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, followed by water (3 × 50 ml) The organic layer was dried over anhydrous magnesium sulfate and filtered The excess solvent was removed under reduced pressure and the resulted compound was purified using flash column chromatography on a silica gel column with hexane and ethyl acetate (1:1) as the eluent

to yield the monomer Yield: 0.85 g (61.0 %) 1H NMR (300 MHz, CDCl3, δ ppm) 9.20 (s, ArH, 1H), 8.95 (s, ArH, 2H), 7.63 (d, J = 8.4 Hz, ArH, 1 H), 6.90(d, J = 8.2 Hz, ArH,

1 H), 6.39 (s, C=CH2, 1 H), 5.80 (s, C=CH2, 1 H), 2.09 (s, -CH3, 3H) 13CNMR (75.4 MHz, CDCl3, δ ppm) 157.5, 154.8, 151.7, 129.1, 128.0, 127.7, 123.8, 122.8, 121 (Ar-C), 18.2(-CH3) MS (EI): m/z: 240.1, 172.1, 118.1, 84.0 Mp: 127 °C

1-Benzyloxy-4-dodecyloxy-2, 5-di(pyridin-5-yl) benzene (7)

Compound 7 was synthesized according to the procedure described for the synthesis of

5-(4-benzyloxy-phenyl) pyrimidine Yield: 4.8 g (65.2 %) 1H NMR (300 MHz, CDCl3, δ ppm): 8.66 - 8.64 (m, Ar-H, 4 H), 7.54 - 7.26 (m, ArH, 9 H), 7.06 (s, ArH, 1 H), 7.00 (s, ArH, 1 H), 5.05 (s, O-CH2-Ar, 2 H), 3.96 (t, J = 6.3 Hz, O-CH2-, 2 H), 1.76 (p, J = 7.5 Hz, C(O)-CH2-, 2 H), 1.26 (b, -CH2- 18 H), 0.88 (t, J = 6.7 Hz, -CH3, 3 H) 13C NMR (75.4 MHz, CDCl3, δ ppm): 157.0, 156.7, 150.8, 149.5, 140.9,131.5, 128.6, 128.2, 127.2,

20.4,115.9, 114.6, 106.2 (Ar-C), 71.7, 69.5 (O-CH-), 318, 29.5, 29.4, 29.3, 29.2, 29.1, 29.0, 25.9, 22.6 (-CH2-), 14.8 (-CH3) MS (EI): m/z: 522.4, 353.1, 263.1, 91.1 Mp: 129.5

°C

4-Dodecyloxy-2, 5-di(pyridin-5-yl) phenol (8)

Compound 8 was synthesized according to the procedure described for the synthesis of compound 5 From 4.0 g (7.7 mmol) of compound 7 was obtained 2.8 g of light yellow

powder Yield: 2.8 g (84.1 %) 1H NMR (300 MHz, CDCl3, δ ppm): 8.60 - 8.57 (m, ArH,

4 H), 7.60 - 6.95 (m, Ar-H, 6 H), 3.92 (t, J = 6.3 Hz, O-CH2-, 2 H), 3.60 (b, O-H, 1 H), 1.73 (q, J = 6.4 Hz, C(O)-CH2-, 2 H), 1.25 (b, -CH2- 18 H), 0.87 (t, J = 6.0 Hz, -CH3, 3 H) 13C NMR (75.4 MHz, CDCl3, δ ppm): 150.2, 149.0, 148.6, 148.0, 124.4, 122.0, 117.5, 114.8, 106.4 (Ar-C), 68.8 (O-CH2-), 31.2, 28.9, 28.8, 28.7, 28.6, 28.5, 28.2, 25.4, 22.2, 20.2 (-CH2-), 14.1 (-CH3) MS (EI): m/z: 432.3, 264.1, 237.1 Mp: 150 °C

4-Dodecyloxy-2, 5-di(pyridin-5-yl) phenyl-1-yl methacrylate (9)

Monomer 9 was synthesized according to the procedure described for the synthesis of monomer 6 From 2.5 g (5.8 mmol) of compound 8 and 1.6 ml (11.6 mmol) methacryloyl

chloride was obtained 0.65 g (26.0 %) of monomer

1H NMR (300 MHz, CDCl3, δ ppm): 8.65 - 7.2 (m, Ar-H, 10 H), 6.17 (s, CH=C, 1 H),

5.65 (s, C=CH, 1 H), 4.00 (t, J = 6.0 Hz, -O-CH2-C-, 2 H), 1.90 (s, C=C-CH3, 3 H), 1.74 (p, J = 6.5 Hz, R(O)-CH2-, 2 H), 1.24 (b, -CH2-, 18 H), 0.86 (t, J = 6.5 Hz, -CH3, 3 H)

13C NMR (75.47 MHz, CDCl3, δ ppm): 171, 149.80, 149.45, 141.17, 137.08, 136.62,

135.76, 134.62, 134.49, 133.79, 130.59, 129.33, 128.88, 126.63, 124.90, 124.07, 123.45, 113.72, 77.33, 76.91, 76.48, 69.11, 31.79, 30.79, 29.51, 29.11, 25.98, 22.56, 21.11, 18.13,

14.02 EI-MS: m/z: 500.2, 345, 331.9, 263, 86, 69

Poly(4-Dodecyloxy-2, 5-di(pyrimidin-5-yl)phenyl-1-yl methacrylate) (P1)

P1 was described in chapter 2 as P03

Poly(4-(pyrimidin-5-yl )phenyl methacrylate) (P2)

Polymerization of monomer 6 was performed according to the procedure described for

P1 From 0.8 g (2.0mmol) of monomer 6 was obtain a light yellow powder Yield: 0.5 g

(62.5%) 1H NMR (300 MHz, DMSO-d6, δ ppm) 9.20-6.90 (m, ArH, 7 H), 1.95 (b, -CH-,

2 H), 1.74 (b, -CH3, 3 H) FT-IR (KBr, cm-1): 3041 (ArH stretching), 2958 (-CH2- stretching), 1745 (ester C=O stretching), 1555, 1508, 1415 (Ar, C=C, C=N stretching)

1259, 1170, 1101 (C-O-C stretching) Mn: 0.60 × 104; Mw: 0.89 × 104; PD: 1.5

Poly(4-Dodecyloxy-2, 5-di(pyridin-5-yl) phenyl-1-yl methacrylate) (P3)

Polymer P3 was performed according to the procedure described for polymer P1 From 0.5 g (1 mmol) of compound 9 was obtained as light yellow polymer Yield: 0.2 g (40%)

1H NMR (300 MHz, CDCl3, δ ppm): 8.65 - 6.97 (b, ArH, 10 H), 4.00 (b, -O-CH2-, 2 H), 1.75-1.65 (m, -CH2-, 4 H), 1.24 (b, -CH2-, 18 H), 0.86 (b, -CH3-, 6 H)

FT-IR (KBr, cm-1): 3041 (ArH stretching), 2958 (-CH2- stretching), 1745 (ester C=O stretching), 1595, 1548, 1410(Ar, C=C, C=N stretching) 1274, 1170, 1101 (C-O-C stretching) Mn: 0.62 × 104; Mw: 1.16 × 104; PD: 1.9

4.2.4 Preparation of complexes

Appropriate amounts of host polymer and dodecylbenzenesulfonic acid (DBSA) were

separately dissolved in appropriate solvent (for P1, in THF; for P2, P3, in DMF) The

concentration of the solution was 50 mg/ml The DBSA solution was added dropwise to the host polymer solution and the mixture was kept stirring for 2 days in room temperature before evaporating the solvent The complexes were further dried at 50 °C in

high vacuum for two days The complexes are marked as Pn(DBSA)x, where x is the number of DBSA molecules per repeating unit of the host polymer

4.3 Results and Discussion

is weaker base than pyridine, usually the second C=N groups in pyrimidine ring are very

difficult to protonate after the first protonation

1223 cm -1

P1 x= 0.5 x= 1.0 x= 2.0

Figure 4.1 FTIR spectra of P1(DBSA)x and the host polymer P1

The stretching peak at 1552 cm-1 from pyrimidine groups of the host polymer is strongly affected with the formation of the complexes With the increase of the content of the DBSA, the peak at 1552 cm-1 decreases and a new peak at 1619 cm-1 appears It is known

that a strong acid such as DBSA is capable of protonating the pyridine ring to form a pyridinium ring7 Similiarly, it is reasonable to attribute the peak at 1619 cm-1 to the vibration of the pyrimidinium groups When x = 2.0, it is expected that all pyrimidine groups were protonated by DBSA, and the peak at 1552 cm-1 was observed to all shifted

to the 1619 cm-1 It is also noted that the peak at about 1220 cm-1 increases with the increase of DBSA This may be due to the increase of the SO3- in DBSA with the deprotonation of –SO3H It is important to note that a large shift of 66 cm-1 was observed upon full complexation This evidence supports that the acidic proton of DBSA is completely transferred to the pyrimidine ring, the interaction has strong ionic character between the positively charged pyrimidinium ring and negatively charged sulfonate anion Therefore, the proton transfer rather than hydrogen bonding is expected to take place

Figure 4.2 shows the FTIR spectra of P2(DBSA)x, where the x is 0.3, 0.75 and 1.0 respectively

1185 cm -1

P2 x= 0.3 x= 0.75