synthesis of water soluble metalloporphyrin-cored amphiphilic … · synthesis of water soluble...

Synthesis of water soluble metalloporphyrin-coredamphiphilic star block copolymer photocatalystsfor an environmental application

Kie Yong Cho1,6 • Hyun-Ji Kim1• Xuan Huy Do1,3 • Jin Young Seo1 •

Jae-Woo Choi4 • Sang-Hyup Lee4 • Ho Gyu Yoon2 •

Seung Sang Hwang1,3 • Kyung-Youl Baek1,3,5

Received: 7 March 2017 / Accepted: 26 April 2017 / Published online: 19 February 2018

� Springer Science+Business Media B.V., part of Springer Nature 2018

Abstract Two series of water-soluble metalloporphyrin-cored amphiphilic star

block copolymers were synthesized by controlled radical polymerizations such as

atom transfer radical polymerization (ATRP) and reversible addition fragmentation

chain transfer (RAFT), which gave eight amphiphilic block copolymer arm chains

consisting of poly(n-butyl acrylate-b-poly(ethylene glycol) methyl ether methacy-

late) (PnBA-b-PEGMEMA, Mn,GPC = 78,000, Mw/Mn = 1.2, 70 wt% of PPEG-

MEMA) and poly(styrene-b-2-dimethylamino ethyl acrylate) (PS-b-PDMAEA,

Mn,GPC = 83,000, Mw/Mn = 1.2, 67 wt% of PDMAEA), yielding porphyrin(Pd)-

(PnBA-b-PPEGMEMA)8 and porphyrin(Pd)-(PS-b-PDMAEA)8, respectively.

Obtained metalloporphyrin polymer photocatalysts were homogeneously solubi-

lized in water to apply to the removal of chlorophenols in water, and was distin-

guished from conventional water-insoluble small molecular metalloporphyrin

photocatalysts. Notably, we found that the water-soluble star block copolymers with

hydrophobic–hydrophilic core–shell structures more effectively decomposed the

& Kyung-Youl Baek

[email protected]

1 Center for Materials Architecturing, Korea Institute of Science and Technology, Hwarangno

14-gil 5, Seongbuk-gu, Seoul 02792, Republic of Korea

2 Department of Materials Science and Engineering, Korea University, Seoul 02841, Republic of

Korea

3 Division of Nano & Information Technology, KIST School, Korea University of Science and

Technology, Seoul 02792, Republic of Korea

4 Center for Water Resource Cycle Research, Korea Institute of Science and Technology,

Hwarangno 14-gil 5, Seongbuk-gu, Seoul 02792, Republic of Korea

5 Center for Convergent Chemical Process, Korea Research Institute of Chemical Technology,

141, Gajeong-ro, Yuseong-gu, Daejeon 34114, Republic of Korea

6 Artie McFerrin Department of Chemical Engineering, Texas A&M University,

College Station 77843-3122, USA

123

Res Chem Intermed (2018) 44:4663–4684

https://doi.org/10.1007/s11164-018-3272-9

http://crossmark.crossref.org/dialog/?doi=10.1007/s11164-018-3272-9&domain=pdf

http://crossmark.crossref.org/dialog/?doi=10.1007/s11164-018-3272-9&domain=pdf

https://doi.org/10.1007/s11164-018-3272-9

chlorophenol, 2,4,6-trichlorophenol (2,4,6-TCP), in water under visible light irra-

diation (k = 1.39 h-1, t1/2 = 0.5 h) in comparison to the corresponding water-

soluble star homopolymer, because the hydrophobic core near the metalloporphyrin

effectively captured and decomposed the hydrophobic chlorophenols in water.

Keywords Metalloporphyrins � Amphiphilic star block copolymers � Living

radical polymerizations � Photocatalysis � Chlorophenols

Introduction

Development of industrial manufacturing based on chemical treatment processes

coincides with substantial water pollution despite strict regulations by environmen-

tal agencies including the US Environmental Protection Agency (EPA) and

European Regulatory Agencies (ERAs) governing the produced wastewater

conditions [1, 2]. Important issues to consider are that water pollution should be

reduced or eliminated for the next generations, and clean water sources should be

maintained. Chlorophenol compounds are widely used chemicals, specifically in the

fields of dyes, petrochemicals, paint, pharmaceuticals, and pesticides [3–6]. These

chemicals are known to have substantially harmful effects on water environments

and human beings because of their high resistance to biodegradation and toxicity

along with inducing mutagens and carcinogens [7–9]. To this end, much effort has

been made to remove chlorophenol compounds from water, and the development of

rational approaches still remains an important challenge.

For efficient removal of chlorophenol compounds, various methods have been

applied such as biological, chemical, and thermal treatments [1, 10–12]. However,

these approaches have shown detrimental results, commonly producing toxic

intermediates and by-products [11–13]. Furthermore, high resistance to biodegra-

dation and the large energy requirements for thermal degradation led these

approaches to meet critical bottlenecks. Photocatalytic oxidation processes have

been introduced for more effective degradation of chlorophenol compounds using

metal-based catalysts than aforementioned methods [3, 5, 6, 14, 15]. In particular,

TiO2-based catalysts such as Ag, Pt, Ni, Ce, and Pd-doped TiO2 nanoparticles (NPs)

have been extensively used for degradation of chlorophenol compounds because

appropriate Fermi level differences lead to enhance photon absorption by efficient

transfer of the photoexcited electrons in the conduction band (CB) [14, 16–20]. In

addition, the benefits of heterogeneous catalysts including facile and cheap

recyclability make these catalysts cost-effectively and environmentally more

promising [21–24]. However, the dissolution of metal-doped NPs will be

accompanied during catalytic reactions because of the low stability of transition

metals, which produces other detrimental issues in safe water [21, 25–28].

Although the performance of organic photocatalysts has exhibited less efficient

photocatalysis than that of metallic catalysts, organic photocatalysts have suggested

better safety issues. In particular, high quantum yields of photoexcited triplet states,

high molar absorption coefficients, and ability to generate active singlet oxygen

4664 K. Y. Cho et al.

123

have made porphyrins a highly promising photocatalyst [29, 30]. On the basis of

beneficial features of porphyrins, porphyrin-based materials including metallopor-

phyrin and their composites have shown substantial photocatalytic performances in

degradation of chlorophenol compounds [31, 32]. However, their low solubility and

poor dispersion in water are two critical limitations for increasing catalytic activity.

To this end, much effort has contributed to grow water-soluble polymers from the

porphyrin core based on the great benefits of the core-first method for uniform

catalytic properties, including accurate control of the arm chain numbers, the core

region density, and the uniform building blocks in arm chains, compared to the arm-

first methods using controlled polymerizations [33–35]. Among several controlled

polymerizations, the controlled living radical polymerizations including atom

transfer radical polymerization (ATRP) and reversible addition fragmentation chain

transfer (RAFT) have been used to synthesize various functionalized polymers such

as random and block copolymers with well-defined molecular weight/chain length

distribution [36–40]. These strategies entail solubility manipulations of porphyrins,

as well as high adsorption/diffusion of reaction substrates near the porphyrin core, in

which the porphyrin core with adequate block copolymer designs can be a great

breakthrough as an efficient photocatalytic system [33, 35, 41, 42].

In previous reports, one good example is a porphyrin core with poly(styrene-b-N-

isopropylacrylamide) (PS-b-PNiPAM) block copolymer arm chains, exhibiting

excellent photocatalytic performance based on substantial adsorption ability derived

from the PS inner block and benzene-based substrates (benzene, toluene,

ethylbenzene, and xylene; BTEX) and water-soluble property of the PNiPAN outer

block [33, 43, 44]. The low critical solution temperature (LCST) function of

PNiPAM makes these porphyrin-cored star block copolymers a promising candidate

because of their thermoresponsive benefits, which can lead to facile recyclability by

temperature control; however, the water solubility of the PNiPAM outer layer core

and the PS inner block with porphyrin is still not sufficient. In order to overcome

this solubility issue, the development of newly designed block copolymers for arm

chains in the porphyrin-cored star polymers remains a key challenge for the efficient

photocatalytic degradation of chlorophenol compounds.

Herein, we proposed two metalloporphyrin-cored water-soluble amphiphilic star

block copolymers including PnBA-b-PEGMEMA and PS-b-PDMAEA block

copolymers as arm chains, synthesized by atom transfer radical polymerization

(ATRP) and reversible addition-fragmentation chain transfer (RAFT) methods,

respectively. Obtained well defined amphiphilic star block copolymers with

* 80,000 g/mol of the molecular weight and 70 wt% of hydrophilic block fraction

were evaluated to confirm the hydrophobic–hydrophilic core–shell effects on

photocatalytic degradation reactions of 2,4,6-TCP, which was also compared to the

hydrophilic star polymer. The hydrophobicity control in the design of the

metalloporphyrin-cored star block copolymers highly impact photocatalytic reac-

tivity because accurate core hydrophobicity with shell hydrophilicity of the star

block copolymer leads to proper interaction with hydrophobic substrates during the

reaction by diffusing out of the oxidized substrates into water after the reaction in

water [33] (Fig. 1). In detail, (1) the chlorophenol hydrophobic substrates are first

concentrated near the metalloporphyrin core by hydrophobic–hydrophobic

Synthesis of water soluble metalloporphyrin-cored… 4665

123

interaction with the hydrophobic inner layer. (2) The generated singlet oxygens

from the porphyrin core under visible light irradiation then react with the

chlorophenols in the hydrophobic inner layer. (3) Finally, the oxidized chlorophe-

nols are diffused to the polar solvent through the hydrophilic outer layer.

Experimental

Materials and characterization

All agents and solvents including dimethylformamide (DMF, [ 99.9%), triethyl

amine (TEA, [ 99.5%), tetrahydrofuran (THF, [ 99.9%), 2,4,6-trichlorophenol

(2,4,6-TCP, 98%), 4-(Dimethylamino)pyridine (DMAP, [ 99%), N,N0-dicyclo-

hexylcarbodiimide (DCC, [ 99%), copper(I) bromide (CuBr, [ 98%), cop-

per(I) chloride (CuCl, [ 99%), palladium(II) chloride (PdCl2,[ 99%) and 4,40-dinonyl-2,20-bipyridyl (dNbpy, 97%) were purchased from Sigma-Aldrich and were

used as received unless otherwise noted. Styrene (Sty, [ 99%), n-butyl acrylate

(nBA,[ 99%), and 2-(dimethylamino)ethyl acrylate (DMAEA, 98%) were purified

by vacuum distillation over CaH2. Poly(ethylene glycol) methyl ether methacrylate

(PEGMEMA) monomer was refined using the inhibitor remover resin (AL-154,

Sigma-Aldrich). 5,10,15,20-Tetrakis(3,5-bis(20-hydroxy-10-ethoxy)phenyl)por-

phyrin (Porphyrin-OH8) was synthesized based on our previous report [33].

The number average molecular weight (Mn) and molecular weight distributions

(Mw/Mn) of the samples were measured using a JASCO PU-2080 plus size exclusion

chromatography (SEC) system equipped with RI-2031 plus refractive index detector

and a UV-2075 plus UV detector (254 nm detection wavelength) using THF or

DMF as the mobile phase at 40 �C and a flow rate of 1 mL/min. The samples were

Fig. 1 Effective capture and decomposition of hydrophobic chlorophenols with hydrophobic–hydrophilic core–shell structured star block copolymers with a metalloporpyrin core in water


123

separated through four columns: Shodex-gel permeation chromatography (GPC)

KF-802, KF-803, KF-804, and KF-805 for the THF eluent system and three

columns: Shodex-GPC KD-802, KD-803, and KD-804 for the DMF eluent system.

The molecular weight and polydispersity index (PDI) were calculated based on the

calibration using polystyrene for the THF eluent system and poly (methyl

methacrylate) for the DMF eluent system. 1H-NMR spectra were taken using

CDCl3 at 25 �C on a 300 MHz Varian Unity INOVA. UV–vis absorption spectra

were measured in air with a JASCO V-670 spectrophotometer. The size distribution

of the star block copolymers in water was determined by dynamic light scattering

(DLS) (Photal, ELSZ-1000) analysis.

Synthesis of 5,10,15,20-tetrakis(3,5-bis(2-bromopropionylethoxy)phenyl)porphyrin, porphyrin-Br8

Porphyrin-Br8 multi-armed ATRP initiator was synthesized by following Sche-

me 1a. Porphyrin-OH8 (0.59 g, 0.02 M) was added to a baked 100 mL round

bottom flask and dissolved it using 27 mL of dried THF. Thereafter, TEA (1.2 mL,

0.32 M) was added to the Porphyrin-OH8 solution. The prepared solution was

stirred in an ice bath for 20 min, and then 2-bromopropionyl bromide (0.9 mL,

0.32 M) was sequentially dropped into the main solution over 10 min under Ar gas.

The reaction was allowed for 17 h at room temperature. After evaporation of the

volatiles, 30 mL of methylene chloride was added and washed twice with 50 mL of

distilled water. The organic parts were collected and dried over using MgSO4. After

filtering of MgSO4, the concentrated reaction mixture was poured into - 75 �Cmethanol. The precipitated red powder was immediately collected with membrane

filter paper (0.2 lm pore size). Precipitations were repeated twice and the obtained

Scheme 1 Synthesis of A porphyrin(Pd)-Br8 ATRP initiator and B porphyrin(Pd)-CTA8 RAFT initiatorfor controlled living radical polymerizations


123

products dried in the vacuum oven for 48 h. 1H NMR (300 MHz, CDCl3): 9 (s, 8H),

7.42 (d, J = 2 Hz, 8H, o-aryl H), 7.05 (t, J = 2 Hz, 4H, p-aryl H), 4.60 (m, 16H,

TPP–OCH2CH2–), 4.40 (q, 8H, –CHBr), 1.84 (d, 24H, CHBr–CH3).

Synthesis of 5,10,15,20-tetrakis(3,5-bis(20-(2-dodecylsulfanylthiocarbonylsulfanyl-2-methylpropionate)-10-ethoxy)phenyl)porphyrin, porphyrin-CTA8

Porphyrin-CTA8 multi-armed RAFT initiator was synthesized by following

Scheme 1b. Porphyrin-OH8 (0.33 g, 0.021 M), 2-dodecylsulfanylthiocarbonylsul-

fanyl-2-methylpionic acid (chain transfer agent, CTA) (1.76 g, 0.333 M), and

DMAP (0.29 g, 0.166 M) were sequentially added to a baked 50 mL round bottom

flask and dissolved using 13 mL of dried THF. Thereafter, the prepared DCC (0.5 g,

0.166 M in 1.5 mL of dried THF) solution was dropped into the main solution over

10 min after the main solution was stirred for 20 min at 0 �C, followed by stirring

for an hour at 0 �C. The reaction was allowed for 12 h at room temperature. After

evaporation of the volatiles, 30 mL of methylene chloride was added and washed

with 50 mL of distilled water. The organic parts were collected and dried over using

MgSO4. After filtering of MgSO4, the concentrated reaction mixture was poured

into - 75 �C methanol. The precipitated red powder was immediately collected by

membrane filter paper (1 lm pore size). Precipitations were repeated twice and the

obtained products dried in the vacuum oven for 48 h. At room temperature, the

product state turned to a sticky gel, 5,10,15,20-Tetrakis(3,5-bis(20-(2-dodecylsul-

fanylthiocarbonylsulfanyl-2-methylpropionate)-10-ethoxy)phenyl)porphyrin. 1H

NMR (300 MHz, CDCl3,): 9 (s, 8H), 7.42 (d, J = 2 Hz, 8H, o-aryl H), 7.05 (t,

J = 2 Hz, 4H, p-aryl H), 4.52 (s, 16H, TPP–OCH2–), 4.33 (m, 16H, TPP–

OCH2CH2–), 3.22 (t, 16H), 1.71 (s, 48H), 1.6–0.95 (m, 160H), 0.83 (t, 24H).

Synthesis of porphyrin(Pd)-Br8 and porphyrin(Pd)-CTA8

Synthesis of palladium contained porphyrin initiators with porphyrin-CTA8 or –Br8/

PdCl2 (1/3) is as follows: Porphyrin-CTA8 (0.5 g, 5.1 mM) or porphyrin-Br8 (0.5 g,

10.0 mM) and PdCl2 (0.069 g, 15.5 mM for the porphyrin-CTA8 and 0.133 g,

30.0 mM for the porphyrin-Br8 were sequentially added to a baked round bottom

(RB) flask under Ar. These solid reagents were dried at room temperature for 2 h

under vacuum. After purging with Ar, DMF (25 mL) was added, and then the

reaction was allowed to continue by refluxing at 110 �C for 20 h. After the

temperature decreased to room temperature, DMF was removed, and the remaining

solid was dissolved in 200 mL of methylene chloride and washed thrice with

400 mL of distilled water and then dried with MgSO4. After removing methylene

chloride, the resulting solid was dissolved in 10 mL of THF, and then the solution

was dropped into cold methanol under strong stirring. The wine color precipitates

were filtered and dried at 30 �C for a day under vacuum.


123

Polymerization of porphyrin(Pd)-cored poly(n-butyl acrylate) via ATRP,porphyrin(Pd)-(PnBA)8

According to the typical ATRP technique, the reagents porphyrin(Pd)-Br8 (0.05 g,

0.02 mmol) CuBr (0.025 g, 0.18 mmol), dNbpy (0.143 g, 0.35 mmol), and nBA

(5 mL, 0.032 mol) were sequentially added to the baked 30 mL RB flask under Ar.

The reaction mixture was stirred at 80 �C for 34 h, and around 26% conversion was

observed. For its purification, the reaction solution was quenched upon cooling to

- 78 �C immediately using liquid nitrogen and then diluted with 50 mL of THF.

This solution was passed through an aluminium oxide column with extra THF. After

concentration of the collected solution under reduced pressure, the solution was

dropped into cold hexane. Thereafter, the precipitates were separated from the liquid

by a decantation process. The obtained precipitates were dissolved in THF, and then

the precipitation process was repeated three cycles. Finally, the obtained

porphyrin(Pd)-(PnBA)8 star polymer was dried at RT for 48 h under vacuum,

yielding Mn,GPC = 31,000 and Mw/Mn = 1.11.

Polymerization of poly(n-butyl acrylate-b-poly(ethylene glycol) methylether methacrylate) star block copolymers via ATRP, (I) porphyrin(Pd)-(PnBA-b-PPEGMEMA)8

According to the typical ATRP technique, the reagents porphyrin(Pd)-(PnBA) 8 (0.

2 g, 1.2 mM), CuCl (3.5 mg, 12 mM), dNbpy (29.2 mg, 70 mM), PEGMEMA

(0.16 mL, 0.24 M), and anisole (3 mL) for (Porphyrin(Pd)-(PnBA-b-

PPEGMEMA)8 were sequentially added to the baked 30 mL RB flask under Ar.

The reaction mixtures were stirred at 90 �C for 24 h, and [ 95% conversion was

observed in both reactions. For its purification, the reaction solution was quenched

upon cooling to - 78 �C immediately using liquid nitrogen and then diluted with

50 mL of THF. This solution was passed through an aluminium oxide column with

extra THF. After concentration of the collected solution under reduced pressure, the

solution was dropped into cold hexane. Thereafter, the precipitates were separated

from the liquid by a decantation process. The obtained precipitates were dissolved

in THF, and then the precipitation process was repeated three cycles. The obtained

precipitates were filtered and dried at room temperature for 48 h under vacuum,

yielding porphyrin(Pd)-(PnBA-b-PPEGMEMA)8 with Mn,GPC = 78,000, Mw/

Mn = 1.2, 70 wt% of PPEGMEMA.

Polymerization of porphyrin(Pd)-cored polystyrene star polymer via RAFT,porphyrin(Pd)-PS8

Porphyrin-CTA (0.1 g, 0.0258 mmol) and AIBN (0.42 mg, 0.00258 mmol) were

added to the baked 30 mL RB flask and dried under vacuum for an hour. Thereafter,

styrene (4.3 g, 0.0413 mol) was injected into the RB flask under Ar and then stirred

until observing the clear solution. The reaction solution was degassed by a freeze–

pump–thaw method. After 12 h, the reaction solution was quenched by immersing

into liquid nitrogen, which was then poured into methanol after dilution with 10 mL


123

of THF. The precipitates were filtered and then dried at room temperature for 48 h

under vacuum, yielding 22.2% conversion of PS with Mn,GPC = 37,000, Mw/

Mn = 1.1 in the porphyrin(Pd)-PS8.

Polymerization of porphyrin(Pd)-cored poly(styrene-b-2-dimethylaminoethyl acrylate) amphiphilic star block copolymer via RAFT, (II)porphyrin(Pd)-(PS-b-PDMAEA)8

A 50 mL RB flask was baked under vacuum. After purging with argon gas,

Porphyrin(Pd)-PS8 (300 mg, 0.02 M) and AIBN (0.41 mg, 2 mM) were added and

dried under vacuum for an hour. Thereafter, DMF (1.24 mL) and DMAEA (3.0 mL,

16 M) were sequentially injected under Ar and then stirred for a clear solution. The

reaction solution was degassed by a freeze–pump–thaw method. The reaction was

allowed by heating at 90 �C. After 24 h, the reaction solution was quenched by

using liquid nitrogen and diluting with 10 mL of THF. Porphyrin(Pd)-(PS-b-

PDMAEA)8 amphiphilic star block copolymer was purified by pouring into cold

hexane under stirring. Thereafter, precipitates were separated from the liquid by a

decantation process. The obtained precipitates were dissolved in THF, and the

precipitation process was repeated three cycles. The obtained precipitates were

filtered and dried at room temperature for 48 h under vacuum, yielding 59.3%

conversion of PDMAEA with Mn,GPC = 83,000, Mw/Mn = 1.2, 67 wt% of

PDMAEA.

Polymerization of porphyrin(Pd)-cored poly(poly(ethylene glycol) methylether methacylate) starpolymers, (III) porphyrin(Pd)-(PPEGMEMA)8

According to the typical ATRP technique, the reagents porphyrin(Pd)-Br8 (0.02 g,

1.2 mM), CuCl (8.7 mg, 12 mM), dNbpy (72 mg, 24 mM), PEGMEMA (1.42 mL,

0.42 M), and anisole (7.3 mL) for porphyrin(Pd)-(PPEGMEMA)8 were sequentially

added to the baked 30 mL RB flask under Ar. The reaction mixtures were stirred at

90 �C for 24 h, and[ 95% conversion was observed in the both reactions. For its

purification, the reaction solution was quenched upon cooling to - 78 �Cimmediately using liquid nitrogen and then diluted with 50 mL of THF. This

solution was passed through an aluminium oxide column with extra THF. After

concentration of collected solution under reduced pressure, the solution was

dropped into cold hexane. Thereafter, precipitates were separated from the liquid by

a decantation process. The obtained precipitates were dissolved in THF, and the

precipitation process was repeated three cycles. The obtained precipitates were

filtered and dried at room temperature for 48 h under vacuum, yielding

porphyrin(Pd)-(PPEGMEMA)8 with Mn,GPC = 86,000, Mw/Mn = 1.2.

Typical procedure for photocatalytic degradation of 2,4,6-trichlorophenol

In order to investigate the photocatalytic reactivity of porphyrin-based star block

copolymers, photocatalytic batch reactions were performed in degradation of 2,4,6-

trichlorophenol (2,4,6-TCP). Photoreactor vessels containing 40 mL of


123

an individual aqueous solution of the 2,4,6-TCP (30 lM) and star polymers (5 lM)

were placed in a photoreactor chamber, with a cooling fan for adjusting the air

temperature (25 �C), a stirrer and a darkroom. Photocatalytic degradation was

performed using six visible light lamps (Philips PL-L; 4 W; emission wavelength:

350–650 nm). The light intensity was measured with a pyranometer (Apogee, PYR-

P) and determined to be 1.105 mW/cm2. Tests for investigation of visible-light

activation were carried out with a UV cut-off filter which blocks irradiation of UV

fractions below 400 nm spectrum. Porphyrin-based star polymers (5 lM) were

injected into the chlorophenol solutions and stirred at 300 rpm. After predetermined

intervals, the 1 mL sample was taken from the reactors and filtered through a

syringe filter (a 0.45 lm pore size) to measure the residual chlorophenol

concentration by HPLC. An HPLC instrument (Perkin Elmer, MA, USA), equipped

with a C18 column (Zorbax Eclipse XDB-C18) and a fluorescence detector at an

excitation wavelength of 230 nm, was used to perform the analysis. Elution was

carried out using 20:80 v/v of 1% phosphoric acid:acetonitrile at a flow rate of

1 mL/min. The column temperature was retained at 40 �C.

Results and discussion

Synthesis of metalloporphyrin-cored ATRP and RAFT initiators

In the synthesis of the metalloporphyrin-cored amphiphilic star block copolymers,

controlled radical polymerization methods are adopted because the controlled

composition of amphiphilic arm chains can be synthesized, which is important for

an efficient photocatalytic reaction. To this end, we designed two different

octafunctional initiators based on a porphyrin core for ATRP and RAFT. For this,

the hydroxyl groups terminated porphyrin-OH8 was first synthesized based on our

previous report [33], and then ATRP and RAFT initiators were introduced by

acylation of the peripheral hydroxyl groups of porphyrin-OH8 with bromopropionyl

bromide and 2-dodecylsulfanylthiocarbonylsulfanyl-2-methylpionic acid (CTA),

respectively (Scheme 1).

The acquired octafunctionalized porphyrin initiators for ATRP and RAFT were

characterized by using 1H NMR (Fig. 2a, b, respectively). The absorption peak at

9 ppm (a) was corresponding to eight protons of connected four pyrrole units

(Fig. 2a). The two characteristic absorption peaks corresponding to aryl groups

connected to the methane bridges of a porphyrin were observed at 7.42 (b) and

7.05 ppm (c), which are eight protons and four protons from ortho and para-aryl

positions, respectively (Fig. 2a). The peripheral hydroxyl groups of porphyrin-OH8

appeared at 4.99 ppm (g), and ethoxy groups followed at 4.25 (d) and 3.86 ppm

(e) (Fig. 2a). The bromopropionyl groups terminated octafunctional ATRP initiator

showed the new absorption peaks at 4.4 (h) and 1.84 ppm (i), which corresponded to

methyl bromide and methyl groups, respectively (Fig. 2b). In addition, the peak at

4.99 ppm corresponding to hydroxyl groups completely disappeared, and the ethoxy

groups (d and f) showed upfield shifts to 4.6 and 4.4 ppm because of electron

donating effects derived from the acryl groups (Fig. 2b). Similar chemical shifts


123

were also observed in the 1H NMR spectrum of porphyrin-CTA8 (Fig. 2c). In

particular, the ethoxy groups (d and f) in porphyrin-CTA8 showed upfield shifts to

4.52 and 4.33 ppm (Fig. 2c). The new characteristic absorption peaks derived from

the CTA were observed at 1.71 ppm (j) corresponding to dimethyl groups and 3.22

(k) and broad 1.6–0.83 ppm (l) corresponding to dodecyl groups (Fig. 2c). To

confirm the completion of metalloporphyrin-cored octafunctional initiators, the

integration ratios of 1H NMR absorption peaks of the porphyrin-Br8 and the

porphyrin-CTA8 were applied and calculated using a and i peaks for the porphyrin-

Br8 and a and k for the porphyrin-CTA8 resulting in ca. 8 bromopropionyl and CTA

groups on a porphyrin core, respectively, which indicated that the octafunctional

ATRP and RAFT initiators were successfully synthesized.

The UV–Vis absorption and color of porphyrins are originated from the highly

conjugated p electrons, and their UV–Vis absorption spectra can be changed by

alteration in the conjugation pathway and symmetry of the porpyrin [45]. The UV–

Vis absorption spectrum of porphyrins can be explained regarding the four-orbitals

including two highest occupied p orbitals and two lowest unoccupied p* orbitals,

which can impact the charge localization on electronic photophysical properties

[46]. Based on the four-electron theory, the absorption spectrum of porphyrin is

derived from transitions between two highest occupied molecular orbitals (HOMOs)

and lowest unoccupied molecular orbitals (LUMOs), as shown in Fig. 3a. The

electron transition behaviors between the orbitals can induce two excited states in

Fig. 2 1H NMR spectra of A porphyrin-OH8 in DMSO-d6, B porphyrin-Br8 in CDCl3, and C porphyrin-CTA8 in CDCl3 at room temperature


123

the energy level including higher energy states with larger oscillator strength

leading to a Soret-band (380–450 nm) and a lower energy state with less oscillator

strength leading to the Q-bands (500–700 nm), which is due to the conjugation of 18

p-electrons of porphyrins (Fig. 3a) [47].

The UV–Vis absorption spectrum of porphyrin-Br8 showed the higher intensity

of a Soret-band absorption peak at 415 nm and the lower intensity of Q-band

absorption peaks in the range of 500–700 nm (I–IV) (Fig. 3b). In Q-bands, the

relative intensities of I–IV exhibited an order of IV[ III[ II[ I, indicating etio-

type porphyrin [48]. After Pd complex with the porphyrin-Br8, we observed the red-

shift of the absorption spectrum in Q-bands (Fig. 3b inset). The relative intensity of

Q-bands can be changed with different positions of substituents and metal

complexes [48]. In particular, the UV–Vis absorption spectrum in Q-bands can be

shifted to higher wavelength, and this red-shift behavior of porphyrins can provide

highly promising capability to use them as a photocatalyst in the visible range,

which can reduce the energy consumption and damages by UV irradiation. The

mechanism for metalloporphyrin formation reaction is generally explained by

incorporating a metal ion Mn? into the porphyrin H2P to form MP(n-2)?, in which

the two amine protons in H2P are dissociated from the two pyrrole groups as

followed equation: Mn? ? H2P $ MP(n-2)? ? 2H? [48]. In addition, after Pd

complex, the order of Q-band intensity was not much changed, exhibiting IV[ I–

III, which indicates good stability of the metal complex derived from a

stable square-planar complex of a metal ion with the porphyrin (Fig. 3b) [49].

The similar photophysical properties in the absorption spectra of the porphyrin-

CTA8 and the porphyrin(Pd)-CTA8 were observed as shown in the UV–Vis

absorption spectra of the porphyrin-Br8 and porphyrin(Pd)-Br8 (Fig. 3c). These

results indicated that the porphyrin-based ATRP and RAFT initiators with Pd-

complex were successfully synthesized.

Fig. 3 Energy levels of the four Gouterman orbitals showing the transitions of a porphyrinsystem A. UV–Vis spectra for before and after Pd complex with B porphyrin-Br8 and C porphyrin-CTA8 measured in THF at room temperature


123

Synthesis of (I) porphyrin(Pd)-(PnBA-b-PPEGMEMA)8 amphiphilic starblock copolymers via ATRP

The porphyrin(Pd)-cored PnBA-b-PPEGMEMA amphiphilic star block copolymer

was synthesized by the Cu-catalyzed ATRP system following Scheme 2. The

poly(n-butyl acrylate) (PnBA) inner block segment in the arm chains of the

porphyrin(Pd)-(PnBA-b-PPEGMEMA)8 star polymer was designed to provide

hydrophobic packing near the porphyrin core due to its hydrophobicity with

relatively low glass transition temperature, which was synthesized by polymeriza-

tion of nBA in the presence of CuBr with dNbpy in bulk at 80 �C. After 34 h, 26%

conversion of nBA was acquired, and the SEC curve of the obtained porphyrin(Pd)-

PnBA8 exhibited 31,000 g/mol with narrow polydispersity (Mw/Mn = 1.1)

Scheme 2 Synthesis of porphyrin(Pd)-(PnBA-b-PPEGMEMA)8 amphiphilic star block copolymers viaATRP process


123

(Fig. 4a). The further reaction for a higher conversion was performed up to reaching

41% conversion of nBA (47 h). However, the SEC curve of porphyrin(Pd)-PnBA8

showed a shoulder in high molecular weight, which is ascribed to coupling reactions

of PnBA propagating radicals. The star–star coupling behaviors are often observed

in the synthesis of branched polymers [33]. To alleviate this side reaction, the earlier

conversion was chosen to synthesize for the porphyrin(Pd)-PnBA8 macroinitiator,

which was then used for block copolymerization of PEGMEMA in the presence of

CuCl with dNbpy in DMF at 90 �C to give the porphyrin(Pd)-(PnBA-b-

PPEGMEMA)8 amphiphilic star block copolymers. After 24 h reaction, the

conversion of PEGMEMA was reached to [ 95% and the SEC curve smoothly

shifted to a higher molecular weight with narrow polydispersity (Mw/Mn = 1.2),

which indicated that the porphyrin(Pd)-(PnBA-b-PPEGMEMA)8 amphiphilic star

block copolymers were successfully synthesized by block copolymerization of

PPEGMEMA from the porphyrin(Pd)-PnBA8 macroinitiator by Cu-catalyzed ATRP

system (Fig. 4b).

To evaluate the molecular structure, the molecular weight, and the weight

fraction of the block copolymer arm chains, 1H NMR analysis of the porphyrin(Pd)-

PnBA8 and the porphyrin(Pd)-(PnBA-b-PPEGMEMA)8 was performed (Fig. 5). 1H

NMR spectrum of porphyrin(Pd)-PnBA8 exhibited the specific broadened peaks (a–

f) derived from the protons in the PnBA star polymer macroinitiator, specifically the

absorption peaks (a and b) corresponded to the acrylate backbone, and the

absorption peaks (c–f) corresponded to ester butyl groups (Fig. 5a). After block

copolymerization of PPEGMEMA from porphyrin(Pd)-PnBA8, the new absorption

peaks appeared at g and h-j positions, which corresponded well to the methacryl

backbone and poly(ethylene glycol) groups, respectively (Fig. 5b). These charac-

teristic assignments in the 1H NMR spectra indicated that porphyrin(Pd)-cored

PnBA-b-PPEGMEMA amphiphilic star block copolymers were well synthesized.

Based on the conversion derived from monomer consumption in the 1H NMR

spectrum, the molecular weights of the porphyrin(Pd)-PnBA8 and the por-

phyrin(Pd)-(PnBA-b-PPEGMEMA)8 were theoretically calculated using Eq. (1) as

follows:

Fig. 4 SEC curves forA porphyrin(Pd)-PnBA8

macroinitiator andB porphyrin(Pd)-(PnBA-b-PPEGMEMA)8 amphiphilic starblock copolymer


123

Mn cal:ð Þ ¼ ð monomer½ �0�MW;monomer � qÞ= I½ �0þMW;I; ð1Þ

where [monomer]0 and [I]0 are initial mole concentration of monomer and initiator,

respectively and MW, monomer and MW, I are molecular weight of monomer and

initiator, respectively. q is conversion of the monomer [33]. The calculated

molecular weight of the porphyrin(Pd)-PnBA8 and the porphyrin(Pd)-(PnBA-b-

PPEGMEMA)8 exhibited 56,000 and 150,000 g/mol, respectively, which were

larger than those by SEC (31,000 and 78,000 g/mol, respectively). These differ-

ences are probably due to the smaller hydrodynamic volume of the star polymer in

comparison to the corresponding linear polymer; specifically, the linear polymer

was applied for SEC calibration as a standard. The weight fraction of the block

segments was calculated from integration ratio of the peak c from the PnBA to the

peaks h and j from the PPEGMEMA as shown in Fig. 5b, exhibiting 70 wt% of the

PPEGMEMA in the porphyrin(Pd)-(PnBA-b-PPEGMEMA)8 amphiphilic star block

copolymer.

Synthesis of (II) porphyrin(Pd)-(PS-b-PDMAEA)8 amphiphilic star blockcopolymers via RAFT

Synthesis of porphyrin(Pd)-(PS-b-PDMAEA)8 amphiphilic star block copolymers

was carried out by RARF process to confirm the effect of hydrophobicity of the

amphiphilic star block copolymer in the photocatalytic reaction because the PS has

Fig. 5 1H NMR spectra of A porphyrin(Pd)-PnBA8 (Mn = 31,000, Mw/Mn = 1.1) and B porphyrin(Pd)-(PnBA-b-PPEGMEMA)8 (Mn = 78,000, Mw/Mn = 1.2, 70 wt% of PPEGMEMA) in CDCl3 at roomtemperature


123

a higher hydrophobicity than that of PnBA in the porphyrin(Pd)-(PnBA-b-

PPEGMEMA)8. The porphyrin(Pd)-PS8 macroinitiator was synthesized by poly-

merization of styrene from the porphyrin(Pd)-CTA8 in the presence of AIBN in bulk

at 80 �C, following Scheme 3. Based on our previous report for the polymerization

of PS from a porphyrin core using the RAFT system, a bulk polymerization system

was chosen for synthesis of the porphyrin(Pd)-PS8 because of the faster reaction

speed in comparison to a solution polymerization system; specifically, the bulk

polymerization led to 70% conversion of styrene within 89 h, while the solution

polymerization saturated at * 45% conversion at 135 h [33]. After 12 h, 22%

conversion of styrene was acquired, and the SEC curve of the obtained

porphyrin(Pd)-PS8 exhibited 37,000 g/mol with Mw/Mn = 1.1 (Fig. 6a). Although

the acquired porphyrin(Pd)-PS8 showed narrow molecular weight distribution, the

Scheme 3 Synthesis of porphyrin(Pd)-(PS-b-PDMAEA)8 amphiphilic star block copolymers via RAFTprocess


123

shoulder in high molecular weight derived from the star–star coupling was also

observed as same in ATRP system and the shoulder was more grown after block

copolymerization of DMAEA in the presence of AIBN in DMF at 90 �C for 24 h,

yielding the porphyrin(Pd)-(PS-b-PDMAEA)8 amphiphilic star block copolymer

with 83,000 g/mol and Mw/Mn = 1.2 (Fig. 6b).1H NMR analyses of the porphyrin(Pd)-PS8 and the porphyrin(Pd)-(PS-b-

PDMAEA)8 were performed to evaluate their molecular weight, the molecular

structure, and the weight fraction (Fig. 7). Based on the Eq. 1, the molecular weight

Fig. 6 SEC curves forA porphyrin(Pd)-PS8

macroinitiator andB porphyrin(Pd)-(PS-b-PDMAEA)8 amphiphilic starblock copolymer

Fig. 7 1H NMR spectra of A porphyrin(Pd)-PS8 (Mn = 37,000, Mw/Mn = 1.1) and B porphyrin(Pd)-(PS-b-PDMAEA)8 (Mn = 83,000, Mw/Mn = 1.2, 67 wt% of PDMAEA) in CDCl3 at room temperature


123

of the porphyrin(Pd)-PS8 and the porphyrin(Pd)-(PS-b-PDMEA)8 exhibited 42,000

and 110,000 g/mol, respectively. The calculated molecular weight values were

larger than those by SEC (37,000 and 83,000 g/mol, respectively), which were

similar in the cases of the porphyrin(Pd)-PnBA8 and the porphyrin(Pd)-(PnBA-b-

PPEGMEMA)8. The 1H NMR spectrum of the porphyrin(Pd)-PS8 showed the

broadened peaks (a–d) derived from the PS and the new peaks (e–g) originated from

the PDMAEA after copolymerization with DMAEA were appeared (Fig. 7). The

weight fraction of the block segments was calculated from integration ratio of the

peak c from the PS to the peak e from the PDMAEA as shown in Fig. 7b, exhibiting

67 wt% of the PDAMEA. The acquired porphyrin(Pd)-(PS-b-PDMAEA)8 amphi-

philic star block copolymer showed similar molecular weight and the block fraction

between the hydrophobic and the hydrophilic layers of the porphyrin(Pd)-(PnBA-b-

PPEGMEMA)8. In addition, a hydrophilic star polymer, porphyrin(Pd)-

PPEGMEMA8 (Mn,GPC = 86,000 g/mol and Mw/Mn = 1.2) without the hydropho-

bic layer was prepared to confirm the effect of the hydrophobic inner layer on the

photocatalytic reactions.

Evaluation of photocatalytic activity

Photocatalytic reactivity of the amphiphilic star block copolymers with similar

molecular weight (Mn,GPC = * 80,000 g/mol) and the block fraction (hydropho-

bic:hydrophilic = 30:70) were examined by degradation reaction of 2,4,6-TCP in

water under visible light ranging from 400 to 650 nm, which was well matched with

the absorption ranges of the porphyrin with Pd complex (Fig. 8). Pseudo-first order

reaction kinetics was applied to determine the reaction rate constant, which was

normalized by Eq. (2) as follows:

ln Ct=C0ð Þ ¼ �kt; ð2Þ

where Ct was the concentration of 2,4,6-TCP at time t, C0 was the concentration of

2,4,6-TCP, and k was the pseudo-first order rate constant [24, 42]. In Fig. 8a, ln(Ct/

C0) versus t plot was shown for (I) porphyrin(Pd)-(PnBA-b-PPEGMEMA)8, (II)

porphyrin(Pd)-(PS-b-PDMAEA)8, and (III) porphyrin(Pd)-(PPEGMEMA)8. All

samples showed a linear relationship between ln(Ct/C0) and t, indicating well-

followed pseudo-fist order reaction kinetics [42]. To examine the effect of the

hydrophobic layer in the star block copolymers, the rate constants of the (I) por-

phyrin(Pd)-(PnBA-b-PPEGMEMA)8 amphiphilic star block copolymer and the (III)

porphyrin(Pd)-(PPEGMEMA)8 hydrophilic star polymer were compared, exhibiting

that the (I) porphyrin(Pd)-(PnBA-b-PPEGMEMA)8 (k = 1.39 h-1) showed a

46-fold higher rate constant than that of the (III) porphyrin(Pd)-(PPEGMEMA)8

(k = 0.03 h-1) (Fig. 8a). In addition, the photocatalytic reactivity was strongly

dependent on the hydrophobicity in the amphiphilic star block copolymers such as

the PnBA and the PS inner block segments; specifically, the (I) porphyrin(Pd)-

(PnBA-b-PPEGMEMA)8 with a less hydrophobic and soft inner layer showed 3.7-

fold higher rate constant in comparison to the (II) porphyrin(Pd)-(PS-b-PDMAEA)8

with a more hydrophobic and hard inner layer (k = 0.38 h-1).


123

These results indicated that the nature of the hydrophobic inner layer of the

amphiphilic star block copolymer was strongly affected to the photocatalytic

reactions in water, which led to enhanced diffusion of the hydrophobic 2,4,6-TCP

near the porphyrin core by hydrophobic–hydrophobic interaction. However, the

hydrophobic inner layer with rigid packing near the metalloporphyrin core such as

PS slightly reduced the photocatalytic activity. These photocatalytic reactions with

the amphiphilic star block copolymer photocatalysts showed much higher rate

constants in comparison to those with conventional heterogeneous photocatalyts

such as organic porphyrin and TiO2-based catalysts for the photocatalytic

degradation reaction of 2,4,6-TCP, which was probably due to the homogeneous

photocatalytic reactions in water (Table 1) [32, 50, 51]. To confirm the hydropho-

bicity difference, DLS analysis was performed with the star polymers in water at

room temperature (Fig. 8b). The (II) porphyrin(Pd)-(PS-b-PDMAEA)8 exhibited the

largest size (* 145.9 nm), followed by the (I) porphyrin(Pd)-(PnBA-b-

PPEGMEMA)8 (105.6 nm) and the (III) porphyrin(Pd)-(PPEGMEMA)8

(* 51.5 nm), indicating that the hydrophobicity of the PS was higher than that

Fig. 8 A The ln(Ct/C0) versus t plot, B DLS curves, C the half-life values, and D the degradationpercentages after 6 h for the photocatalytic degradation of 2,4,6-TCP in the presence of star polymersincluding (I) porphyrin(Pd)-(PnBA-b-PPEGMEMA)8, (II) porphyrin(Pd)-(PS-b-PDMAEA)8, and (III)porphyrin(Pd)-(PPEGMEMA)8. For DLS measurements, the polymer concentration was 0.2 mg/mL inwater


123

of PnBA because the PS was much harder than the PnBA (Fig. 8b). This result was

well matched with the Nabid’s report that they examined the diameter of micelles of

star-shaped poly(e-caprolactone-b-polyethylene glycol) (PCL-b-PEG) block copoly-

mers according to the length of hydrophobic, exhibiting that the increase of

molecular weight of the PCL from 9500 to 15,400 g/mol showed an increase of a

micelle diameter from 75 to 122 nm [52].

The photocatalytic reactivity of the star polymers was examined by calculation of

half-life and removal percentage of 2,4,6-TCP. The half-life of the (I) por-

phyrin(Pd)-(PnBA-b-PPEGMEMA)8, the (II) porphyrin(Pd)-(PS-b-PDMAEA)8,

and the (III) porphyrin(Pd)-(PPEGMEMA)8 star polymers for a first order reaction

was deduced from Eq. 3 as follows:

t1=2 ¼ 0:693=k; ð3Þ

exhibiting 0.5, 1.82, and 23.1 h, respectively (Fig. 8c and Table 1). Notably, the

(I) porphyrin(Pd)-(PnBA-b-PPEGMEMA)8 showed almost 100% removal of 2,4,6-

TCP. However, the (II) porphyrin(Pd)-(PS-b-PDMAEA)8 and the (III) por-

phyrin(Pd)-(PPEGMEMA)8 exhibited 90.5 and 20.8% of removal, despite a reten-

tion time of 6 h (Fig. 8d and Table 1). These results can also be explained by the

hydrophobic–hydrophobic interaction and the water solubility effects for the pho-

tocatalytic degradation of 2,4,6-TCP.

The photocatalytic degradation reaction of 2,4,6-TCP indicated that the efficient

photocatalytic reaction could be realized by the hydrophobic interaction between

2,4,6-TCP and the metalloporphyrin-cored star block copolymer. The modeling test

to confirm host–guest interaction was performed using 2,4,6-TCP with por-

phyrin(Pd)-(PnBA-b-PPEGMEMA)8 (Fig. 9). The schematic illustration for the

host–guest interaction between the star block copolymer host and the hydrophobic

guest is depicted in Fig. 9a. In the polar solvents, the hydrophobic guests possess

higher affinity to the hydrophobic inner block segment of the star block copolymer,

in which the guest molecules are thus efficiently captured and diffused to the near

Table 1 Catalytic performance for photocatalytic degradation of 2,4,6-TCP with different photocatalysts

Catalyst [Catalyst]a

(lM)

Rate constant

(h-1)

t1/2

(h)

Removal % at

6 h

Ref.

(I) porphyrin(Pd)-(PnBA-b-

PPEGMEMA)8

5.0 1.39 0.50 100 This

work

(II) porphyrin(Pd)-(PS-b-

PDMAEA)8

5.0 0.38 1.82 90.5 This

work

(III) porphyrin(Pd)-

(PPEGMEMA)8

5.0 0.03 23.10 20.8 This

work

Porphyrin(Fe)-SiO2 18.7 0.39 1.77 NA [32]

TiO2 4.0 (g/L) 0.20 3.47 93.3 [50]

2%Ag-TiO2 1.0 (g/L) 0.45 1.54 NA [51]

a[Catalyst] is concentration of catalysts


123

porphyrin core. For this, the host–guest modeling reaction was carried out in

CD3OD and monitored by 1H NMR spectroscopy (Fig. 9b). 2,4,6-TCP itself showed

a sharp peak at 7.03 ppm (a) corresponded to the benzene ring of 2,4,6-TCP

(Fig. 8b). In the presence of 10 mg of porphyrin(Pd)-(PnBA-b-PPEGMEMA)8, the

peak a was shifted to downfield at 7.1 ppm (a0) with a slightly broadened peak

shape, indicating the encapsulation within the hydrophobic inner block segment of

the porphyrin(Pd)-(PnBA-b-PPEGMEMA)8. This result was well matched with our

previous report, which was studied with ethylbenzene and porphyrin-cored PS-b-

PNiPAM star block copolymer [33]. Meanwhile, an increase of porphyrin(Pd)-

(PnBA-b-PPEGMEMA)8 content exhibited an increase of the peak intensity for the

star block copolymer, while it was not strongly influenced on the proton peaks of

2,4,6-TCP, indicating that the presence of 10 mg of porphyrin(Pd)-(PnBA-b-

PPEGMEMA)8 was sufficient to capture of 0.5 M of 2,4,6-TCP in methanol.

Conclusions

The metalloporphyrin-cored water-soluble amphiphilic star block copolymers with

similar molecular weights and block fractions including PnBA-b-PEGMEMA

(Mn,GPC = 78,000, Mw/Mn = 1.2, 70 wt% of PPEGMEMA) and PS-b-PDMAEA

(Mn,GPC = 83,000, Mw/Mn = 1.2, 67 wt% of PDMAEA) block copolymer arm

chains were successfully synthesized by atom transfer radical polymerization

(ATRP) and reversible addition-fragmentation chain transfer (RAFT), respectively.

Fig. 9 A Schematic depiction for host–guest interaction between metalloporphyrin-cored star blockcopolymer and 2,4,6,-TCP via hydrophobic interaction. B 1H NMR spectra of 2,4,6-TCP (0.5 M) and2,4,6-TCP with different content of porphyrin(Pd)-(PnBA-b-PPEGMEMA)8 in CD3OD


123

The acquired amphiphilic star block copolymers were evaluated their photocatalytic

reactivity by degradation reactions of 2,4,6-TCP under visible light irradiation. The

porphyrin(Pd)-(PnBA-b-PPEGMEMA)8 showed the higher photocatalytic reactivity

with the higher rate constant and half-life (k = 1.39 h-1, t1/2 = 0.5 h) in

comparison to those of the porphyrin(Pd)-(PS-b-PDMAEA)8 (k = 0.38 h-1, t1/

2 = 1.82 h) and the porphyrin(Pd)-(PPEGMEMA)8 (k = 0.03 h-1, t1/2 = 23.1 h),

indicating the important role of the hydrophobic inner layers in the amphiphilic star

block copolymers, which was strongly dependent on the hydrophobicity of the inner

layer. Therefore, the selection of the hydrophobic block inner layer for designing the

metalloporphyrin-cored amphiphilic star block copolymers is an important param-

eter to degrade 2,4,6-TCP efficiently in the photocatalytic system in water. To this

end, the improvement of the porphyrin-based star polymers for more facile

recycling properties is desired in the forthcoming study.

Acknowledgements This work was supported by the National Research Council of Science and

Technology (NST) grant by the Korea government (MSIP) (No. CMP-16-04-KITECH) and partially

supported by R&D Convergence Program of Ministry of Science, ICT and Future Planning, National

Research Council of Science and Technology (No. CRC-14-1-KRICT).

References

1. M. Pera-Titus, V. Garcıa-Molina, M.A. Banos, J. Gimenez, S. Esplugas, Appl. Catal. B 47, 219

(2004)

2. K.C. Christoforidis, M. Louloudi, Y. Deligiannakis, Appl. Catal. B 95, 297 (2010)

3. T. Zhou, Y. Li, T.T. Lim, Sep. Purif. Technol. 76, 206 (2010)

4. G.C. Chen, X.Q. Shan, Y.S. Wang, B. Wen, Z.G. Pei, Y.N. Xie, T. Liu, J.J. Pignatello, Water Res. 43,

2409 (2009)

5. L. Liu, F. Chen, F. Yang, Y. Chen, J. Crittenden, Chem. Eng. J. 181–182, 189 (2012)

6. Z. Zhang, Q. Shen, N. Cissoko, J. Wo, X. Xu, J. Hazard. Mater. 182, 252 (2010)

7. B.W. Zhu, T.T. Lim, J. Feng, Chemosphere 65, 1137 (2006)

8. L. Zurich, R.P. Schwarzenbach, E. Molnar-kubica, W. Giger, S.G. Wakeham, Environ. Sci. Technol.

13, 1367 (1979)

9. S. Chaliha, K.G. Bhattacharyya, Chem. Eng. J. 139, 575 (2008)

10. A. Santos, P. Yustos, A. Quintanilla, F. Garcıa-Ochoa, J.A. Casas, J.J. Rodriguez, Environ. Sci.

Technol. 38, 133 (2004)

11. M. Alexander, Science 211, 132 (1981)

12. A. Santos, P. Yustos, A. Quintanilla, S. Rodrıguez, F. Garcıa-Ochoa, Appl. Catal. B 39, 97 (2002)

13. S.T. Kolaczkowski, P. Plucinski, F.J. Beltran, F.J. Rivas, D.B. McLurgh, Chem. Eng. J. 73, 143

(1999)

14. A.M.T. Silva, C.G. Silva, G. Drazic, J.L. Faria, Catal. Today 144, 13 (2009)

15. K. Mogyorosi, A. Farkas, I. Dekany, I. Ilisz, A. Dombi, Environ. Sci. Technol. 36, 3618 (2002)

16. N.F. Jaafar, A.A. Jalil, S. Triwahyono, J. Efendi, R.R. Mukti, R. Jusoh, N.W.C. Jusoh, A.H. Karim,

N.F.M. Salleh, V. Suendo, Appl. Surf. Sci. 338, 75 (2015)

17. M.A. Barakat, H. Schaeffer, G. Hayes, S. Ismat-Shah, Appl. Catal. B 57, 23 (2005)

18. H. Liu, L. Deng, C. Sun, J. Li, Z. Zhu, Appl. Surf. Sci. 326, 82 (2015)

19. H. Tada, T. Kiyonaga, S. Naya, Chem. Soc. Rev. 38, 1849 (2009)

20. V. Subramanian, E.E. Wolf, P.V. Kamat, J. Am. Chem. Soc. 126, 4943 (2004)

21. T.H. Kwon, K.Y. Cho, K.Y. Baek, H.G. Yoon, B.M. Kim, RSC Adv. 7, 11684 (2017)

22. A. Saffar-Teluri, Res. Chem. Intermed. 40, 1061 (2014)

23. J. Bennett, A.F. Lee, K. Wilson, J. Mater. Chem. A 4, 3617 (2016)

24. K.Y. Cho, Y.S. Yeom, H.Y. Seo, P. Kumar, A.S. Lee, K.-Y. Baek, H.G. Yoon, J. Mater. Chem. A 3,

20471 (2015)

25. L. Wang, N. Wang, L. Zhu, H. Yu, H. Tang, J. Hazard. Mater. 152, 93 (2008)


123

26. G. Hitoki, A. Ishikawa, T. Takata, J.N. Kondo, M. Hara, K. Domen, Chem. Lett. 31, 736 (2002)

27. K.Y. Cho, Y.S. Yeom, H.Y. Seo, P. Kumar, A.S. Lee, K.-Y. Baek, H.G. Yoon, A.C.S. Appl, Mater.

Interfaces 9, 1524 (2017)

28. K.Y. Cho, Y.S. Yeom, H.Y. Seo, P. Kumar, K.-Y. Baek, H.G. Yoon, J. Mater. Chem. A 5, 3129

(2017)

29. W. Kim, J. Park, H.J. Jo, H.J. Kim, W. Choi, J. Phys. Chem. C 112, 491 (2008)

30. Y. Chen, A. Li, Z.-H. Huang, L.-N. Wang, F. Kang, Nanomaterials 6(51), 1 (2016)

31. G. Lente, J.H. Espenson, New J Chem 28, 847 (2004)

32. K.C. Christoforidis, E. Serestatidou, M. Louloudi, I.K. Konstantinou, E.R. Milaeva, Y. Deligian-

nakis, Appl. Catal. B 101, 417 (2011)

33. K.Y. Cho, J.-W. Choi, S.-H. Lee, S.S. Hwang, K.-Y. Baek, Polym. Chem. 4, 2400 (2013)

34. H.J. Kim, K.Y. Cho, S.S. Hwang, D.H. Choi, M.J. Ko, K.Y. Baek, RSC Adv. 6, 49206 (2016)

35. W.R. Dichtel, K.-Y. Baek, J.M.J. Frechet, I.B. Rietveld, S.A. Vinogradov, J. Polym. Sci. Part A

Polym. Chem. 44, 4939 (2006)

36. K. Matyjaszewski, Macromolecules 45, 4015 (2012)

37. K.Y. Cho, S.S. Hwang, H.G. Yoon, K.-Y. Baek, J. Polym. Sci. Part A Polym. Chem. 51, 1924 (2013)

38. G. Moad, E. Rizzardo, S.H. Thang, Aust. J. Chem. 62, 1402 (2009)

39. K.Y. Baek, H.J. Kim, S.H. Lee, K.Y. Cho, H.T. Kim, S.S. Hwang, Macromol. Chem. Phys. 211, 613

(2010)

40. K.Y. Cho, A. Cho, H.J. Kim, S.H. Park, C.M. Koo, Y.J. Kwark, H.G. Yoon, S.S. Hwang, K.Y. Baek,

Polym. Chem. 7, 7391 (2016)

41. J.W. Choi, S.G. Chung, K.Y. Cho, K.Y. Baek, S.W. Hong, D.J. Kim, S.H. Lee, Water Air Soil Pollut.

223, 1437 (2012)

42. K.Y. Cho, H.Y. Seo, Y.S. Yeom, P. Kumar, A.S. Lee, K.-Y. Baek, H.G. Yoon, Carbon 105, 340

(2016)

43. J.-W. Choi, K.-Y. Baek, K.-Y. Cho, N.V. Shim, S.-H. Lee, Adv. Chem. Eng. Sci. 1, 77 (2011)

44. J.W. Choi, S.G. Chung, K.Y. Baek, K.Y. Cho, S.W. Hong, D.J. Kim, S.H. Lee, Water Air Soil Pollut.

223, 609 (2012)

45. M. Gouterman, J. Mol. Spectrosc. 6, 138 (1961)

46. M. Gouterman, J. Chem. Phys. 30, 1139 (1959)

47. R. Yang, K. Wang, L. Long, D. Xiao, X. Yang, W. Tan, Anal. Chem. 74, 1088 (2002)

48. M. Tabata, M. Tanaka, Trends Anal. Chem. 10, 128 (1991)

49. S.L. Bailey, P. Hambright, Inorg. Chim. Acta 344, 43 (2003)

50. T. Pandiyan, O. Martınez Rivas, J. Orozco Martınez, G. Burillo Amezcua, M.A. Martınez-Carrillo, J.

Photochem. Photobiol. A Chem. 146, 149 (2002)

51. S. Rengaraj, X.Z. Li, J. Mol. Catal. A Chem. 243, 60 (2006)

52. M.R. Nabid, S.J. Tabatabaei Rezaei, R. Sedghi, H. Niknejad, A.A. Entezami, H.A. Oskooie, M.M.

Heravi, Polymer 52, 2799 (2011)


123

synthesis of water soluble metalloporphyrin-cored amphiphilic … · synthesis of water soluble...

Documents