Synthesis, characterization and bulk properties of well-defined poly(hexafluorobutyl methacrylate)-block-poly(glycidyl methacrylate) via consecutive ATRP

Synthesis, characterization and bulk properties of well-defined poly(hexafluorobutyl methacrylate)-block-poly(glycidyl methacrylate) via consecutive ATRP

Journal of Fluorine Chemistry 153 (2013) 74–81 Contents lists available at SciVerse ScienceDirect Journal of Fluorine Chemistry journal homepage: ww...

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Journal of Fluorine Chemistry 153 (2013) 74–81

Contents lists available at SciVerse ScienceDirect

Journal of Fluorine Chemistry journal homepage: www.elsevier.com/locate/fluor

Synthesis, characterization and bulk properties of well-defined poly(hexafluorobutyl methacrylate)-block-poly(glycidyl methacrylate) via consecutive ATRP Bingyan Jiang a,b, Lei Zhang a,b, Jingzhi Shi a,b, Shoufa Zhou a,b, Bing Liao a, Hailu Liu a, Jingxin Zhen a, Hao Pang a,* a b

Guangzhou Institute of Chemistry, Chinese Academy of Sciences, Guangzhou 510650, China University of Chinese Academy of Sciences, Beijing 100049, China

A R T I C L E I N F O

A B S T R A C T

Article history: Received 6 October 2012 Received in revised form 23 April 2013 Accepted 6 May 2013 Available online 31 May 2013

A well-defined fluorine-containing copolymer with pendant epoxy groups, poly(2,2,3,4,4,4-hexafluorobutyl methacrylate-block-glycidyl methacrylate) (PHFBMA-b-PGMA), was prepared by sequential atom transfer radical polymerization (ATRP). The amphiphilic copolymer PHFBMA-b-PGMA(OH) with pendant hydroxyl groups was obtained after ring-opening reaction of the epoxy groups from PGMA. The macroinitiator agent PHFBMA-Br and its copolymers were proved to be successfully synthesized by characterization of FTIR, 1H NMR and gel permeation chromatography (GPC). The chain growth experiment demonstrated that a linear first-order relationship was fitted under the conditions. In addition, the fluorinated copolymers with functional groups in the side chain could keep the contact angle and the advantages of fluoropolymers while improving the hydrophilic property. Meanwhile, TGA testing showed that the copolymers had better thermal stability than its homopolymer. TEM observation indicated that microspheres were embedded in the stable micelles when the final copolymer concentration of aqueous solution was 1 wt%. ß 2013 Elsevier B.V. All rights reserved.

Keywords: Fluorinated copolymer Glycidyl methacrylate ATRP Amphiphilic

1. Introduction Fluoropolymers with high electro-negativity and small fluorine atoms possess a number of unique features, such as high chemical and thermal resistance, oil and water repellence, low surface energy and low refractive index [1–3]. Additionally, fluorine monomers have good compatibility with other (methyl)acrylates and can be incorporated conveniently [4,5]. So many functional fluorinated polymers apply in various ways, such as surfactants, paints, biomaterials and lubricants, etc. [6–9]. To obtain multifunctional fluorinated polymers with welldefined structure and features, the most popular and efficient controlled/living radical polymerization (CLRP) techniques [10– 14] are atom transfer radical polymerization (ATRP) with good controllability with monomers and well-defined property [15–18]. Many hydrophobic fluoropolymers are synthesized by ATRP method, such as poly(butyl methacrylate)-b-poly(perfluoroalkyl acrylate) (PBMA-b-PPFAA) [19], poly(styrene)-b-poly(2,2,3,3,4,4,4heptafluorobutyl methacrylate) (PS-b-PHFBMA) [20], poly(methyl

* Corresponding author. Tel.: +86 20 852 31236; fax: +86 20 852 31445. E-mail address: [email protected] (H. Pang). 0022-1139/$ – see front matter ß 2013 Elsevier B.V. All rights reserved. http://dx.doi.org/10.1016/j.jfluchem.2013.05.012

acrylate)-b-poly(2,2,3,3,3-pentafluoropropyl acrylate) (PMA-bPPFPA) [21], poly(2,3,4,5,6-pentafluorostyrene)-b-poly(styrene)b-poly(2,3,4,5,6-pentafluorostyrene) (PFS-b-PS-b-PFS) [22], poly (hexafluorobutyl methacrylate)-b-poly(isobutyl methacrylate) (PHFMA-b-PIBMA) [23] and poly(ethylene oxide)-(o-nitrobenzyl)-poly[2-(perfluorooctyl)ethyl methacrylate]-b-poly(2-cinnamoyloxyethyl methacrylate) (PEO-ONB-PFOEMA-b-PCEMA) [24]. In addition, many amphiphilic fluorinated polymers also have been attracted significant research interest in many fields. For example, He et al. used hydroxyethyl methylacrylate (HEMA) and trifluoroethyl methacrylate (TFEMA) as monomers to synthesize diblock copolymers by ATRP, and then compared the controllability of the polymerization process by using different ligands [25]; Luo et al. prepared well-defined diblock copolymers poly(dimethylsiloxane)-b-poly(2,2,3,3,4,4,4-heptafluorobutyl methacrylate) by ATRP and then investigated their self-assembly behavior with microphase-separation when containing enough PHFBMA segments [26]; Tan et al. synthesized well-defined fluorinated brush-like amphiphilic copolymers of methoxy poly(ethylene glycol)-bpoly[poly(ethylene glycol)methyl ether methacrylate]-b-poly (pentafluorostyrene) (PEO-b-PmPEGMA-b-PPFS) via ATRP method and studied the self-assembly behavior in aqueous solutions [27]; Guo et al. prepared novel amphiphilic fluorinated ABC-type

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triblock copolymers of poly[(ethylene oxide) monomethyl ether]-bpoly(styrene)-b-poly(perfluorohexylethyl acrylate) (mPEG-b-PS-bPPFHEA) by ATRP [28]. Other amphiphilic copolymers synthesized by ATRP method include (Zonyl FSO-100)-b-poly[(ethylene glycol) methyl ether methacrylate] (FSO-b-PmPEGMA) [29], poly(1,1dihydroperfluorooctyl methacrylate)-b-poly(2-dimethylaminoethyl methacrylate) (PFOMA-b-PDMAEMA) [30], poly(methyl methacrylate)-b-poly[(ethylene glycol)methyl ether methacrylate]b-poly(3,3,4,4,5,5,6,6,7,7,8,8,9,9,10,10,10-heptade-cafluorodecyl methacrylate) (PMMA-b-PmPEGMA-b-PFM) [31], poly(acrylic acid)-b-poly[4-(40 -p-tolyloxy perfluorocyclobutoxy)benzyl methyacrlate] (PAA-b-PTPFCBBMA) [32], and so on. However, it is difficult to dissolve many fluoropolymers with excellent hydrophobicity and other advantages in common solvents, which greatly limits their application. Some work have been reported about fluorinated copolymers with active groups by ATRP method. Davis et al. synthesized poly(pentafluorostyrene)-b-poly(glycidyl methyacrylate) (PPFS-bPGMA) using PGMA as the macro-RAFT agent and then hydrolyzed the epoxy groups to obtain amphiphilic copolymer [33]. Yu group prepared poly(2,2,2-trifluoroethyl acrylate)-b-poly(glycidyl methacrylate) (PTFEA-b-PGMA) diblock copolymer via sequential reversible addition-fragmentation chain transfer (RAFT) polymerization and then incorporated it into epoxy to form nano-structure thermosets [34]. However, few reports investigate the properties of fluorinated copolymers with many active groups on the side chain, especially obtaining active hydroxyl groups by ring-opening of epoxy groups to increase the hydrophilicity or to supply active sites. Fluorinated homopolymers with low initiating efficiency and poor compatibility with other hydrophilic polymer greatly limit their further research. So it is essential to investigate the mechanism of copolymerization by using fluoropolymer as initiator agent, and to prepare many functional polymers by post-modification of the active sites to broaden their application. In this study, hexafluorobutyl methacrylate (HFBMA) was chosen as the fluorine-containing monomer. The other functional monomer was glycidyl methyacrylate (GMA) with reactive pendant oxirane rings. Homopolymer poly(hexafluorobutyl methacrylate) was firstly synthesized by ATRP and then was used as macroinitiator to prepare copolymer poly(hexafluorobutyl methacrylate)-b-poly(glycidyl methacrylate), which was followed by ring-opening reaction. The aim of this work is to investigate the polymerization kinetic of the fluorinated homopolymer and the surface property of the as-prepared fluorinated copolymers. The surface property and the thermal stability of the polymers were investigated as well. The copolymers with epoxy groups and hydroxyl groups would provide many active sites to prepare many novel materials, and this work is currently in progress. 2. Results and discussion The copolymer was prepared by consecutive ATRP method after monomer HFBMA was transformed into the macroinitiator agent PHFBMA-Br, and then hydrolyzed the epoxy groups on PGMA conducted in the present of the acid. The scheme for the synthesis of well-defined copolymers is shown in Scheme 1. And the polymerization result and structural parameter are summarized in Table 1. 2.1. ATRP polymerization of PHFBMA-Br and PHFBMA-b-PGMA The macroinitiator PHFBMA-Br was prepared in cyclohexanone at 75 8C with CuBr/Bpy as catalyst and ethyl 2-bromoisobutyrate as initiator. The 1H NMR spectrum of PHFBMA is shown in Fig. 1a. The characteristic peaks of PHFBMA can be observed at

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0.9–1.2 ppm and 1.8–2.0 ppm, corresponding to the methyl (CH3) and methylene (CH2) groups in the polymer backbone. The peaks of 4.3–4.4 ppm and 4.8–5.0 ppm are corresponding to –OCH2– and –CHF–, while the peaks of 5.67 ppm and 6.20 ppm (vinyl group in the monomer) are not presented in the spectrum. Fig. 2a shows the FTIR spectrum of homopolymer PHFBMA from ATRP. The characteristic band at 1750 cm1 corresponds to ester carbonyl (C5 5O) bonds, the peaks at 1290 cm1 (ys(CF2) + r(CF2)) and 1190 cm1 (ys(CF2) +d(CF2)) are ascribed to the characteristic absorbance of –CF2 and two medium bands at 685 cm1 and 723 cm1 are assigned to a combination of rocking and wagging vibrations of C–F [19]. Two characteristic bands at 3000– 3100 cm1 and 1650 cm1 (stretching vibration of C5 5C bond) disappear. The NMR result and FTIR spectroscopy confirmed that the homopolymer was successfully prepared. Meanwhile, the typical GPC trace of homopolymer is shown in Fig. 3a, revealing a monomodal and symmetric elution peak. Comparing to the results of the molecular weight in Table 1, the number average molecular weight (20, 300 g mol1) of PHFBMA-Br tested by GPC is higher than that (18, 900 g mol1) calculated by 1H NMR. This could be attributed to the difference of the hydrodynamic volume of PHFBMA to that of PS used for the calibrating the GPC columns. The controlled polymerization of block copolymer was confirmed by comparing the 1H NMR spectra of PHFBMA-b-PGMA (Fig. 1b) and PHFBMA (Fig. 1a). Additional peaks are observed at 3.21 ppm, 2.82 ppm and 2.62 ppm, corresponding to the methine protons and methylene protons on the epoxy ring. The peak of 3.78 ppm is attributed to the methylene protons near the ester groups, while the peak 4.30 ppm is a mixed peak of the methene protons copolymer of GMA and HFBMA. Meanwhile, FTIR spectrum of diblock PHFBMA-b-PGMA in Fig. 2b is clearly observed the characteristic band of epoxy group at 907 cm1, 844 cm1 and 755 cm1. The apparent number-average molecular weight and molecular weight distribution of diblock polymer are presented in Table 1, and the GPC trace is shown in Fig. 3b. It is obvious that the curve of block polymer is symmetric and nearly unimodal and the position of peak shifts toward high molecular weight compared with its precursor. The chain extension was further demonstrated well-controlled ATRP of copolymer. 2.2. Polymerization kinetic of PHFBMA-b-PGMA The polymerization kinetic of chain growth experiment was investigated from 1H NMR and GPC to better understand the controlled character of the polymerization macroinitiator PHFBMA. The monomer conversion was obtained by contrasting the sum of the peak intensity for the double bond protons (5.86 and 6.18 ppm) and that of the epoxy protons at 3.27 ppm of GMA. The molecular weight and PDI of all samples by intermittent sampling method were also applied for GPC testing. On the basis of the results of 1H NMR and GPC, the relationship of monomer conversion and ln([M]o/[M]t) with copolymerization time was conducted at [GMA]0/[I]0/[Cu(I)Cl]0/[PMDETA]0 = 80:1:1:2.3. It can be seen from the semilogarithmic kinetic plots for copolymerization of PHFBMA-b-PGMA in Fig. 4 that the monomer conversion increases with time increasing and reaches a relatively high value (>90%) after 20 h. As shown in Fig. 4, ln([M]o/[M]t) is proportional to the copolymerization time, which indicated that the copolymerization reaction could be expressed by the first-order reaction kinetic model under the conditions. This demonstrated that the copolymerization rate was proportional to monomer conversion and also indicated that the concentration of growing radicals remained constant during the copolymerization as well as no detectable termination occurred in the polymerization [16,35]. Therefore, the macroinitiator agent PHFBMA-Br has enough initiator capability to promote the copolymerization

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Scheme 1. Synthesis of (a) macroinitiator PHFBMA-Br, (b) its block copolymer PHFBMA-b-PGMA via two-step ATRP polymerization and (c) PHFBMA-b-PGMA(OH) by acid hydrolysis.

Table 1 Summary of structural parameters of polymers synthesized in this work. Polymer

Conversiona (%)

Mn,NMRb (104 g mol1)

Mn,GPCc (104 g mol1)

PDIc

PHFBMA75-Br PHFBMA75-b-PGMA52 PHFBMA75-b-PGMA52(OH)

62.5 65.3 –

1.89 2.73 –

2.03 3.02 3.15

1.14 1.25 1.42

a Monomer conversion was determined by 1H NMR method according to change the peaks in alkene (5.59 ppm and 6.15 ppm) and the characteristic peaks in chemical shift 4.8–5.0 ppm. b The molecular weights were determined by 1H NMR. c The number-average molecular weight and the polydispersity index were measured by gel permeation chromatograph (GPC) on PS standards.

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Fig. 3. GPC curves for (a) PHFBMA-Br, (b) PHFBMA-b-PGMA and (c) PHFBMA-bPGMA(OH).

Fig. 1. 1H NMR spectra for (a) macroinitiator PHFBMA-Br, (b) block copolymer PHFBMA-b-PGMA in deuterated chloroform.

reaction even though its molecular weight is higher than some small initiators. Other macromolecular initiators, such as PTFEMABr in reference [25], reached about 89% of high initiator efficiency from 2,2-dipyridyl system to prepare copolymer PTFEMA-bPHEMA. Narrow molecular weight distribution of fluoropolymers is very important for self-assembly and other applications, whereas it is difficult to get PHFBMA-b-PGMA with narrow distribution from other methods except ATRP technique. The GPC traces of relationship between the number molecular weight and polydispersity vs. monomer conversion by ATRP are depicted in Fig. 5. The straight line in the plot refers to the theoretical molecular weight at a certain monomer conversion. A linear increase of the molecular weight with monomer conversion is observed, and the measured values of Mn are very close to the theoretical prediction. Furthermore, the molecular weight distributions of all samples are very narrow (PDIs < 1.35) within the investigated conversion range. All these results revealed the controlled nature of the ATRP copolymerization of PHFBMA-b-PGMA.

Fig. 2. FTIR spectra for (a) PHFBMA-Br, (b) PHFMA-b-PGMA and (c) PHFBMA-bPGMA(OH).

Fig. 4. Semilogarithmic kinetic plot for ATRP of PHFBMA-b-PGMA in diphenyl ether and 2-butanone at 30 8C, and the concentration ratios [GMA]0/[I]0/[Cu(I)Cl]0/ [PMDETA]0 = 80:1:1:2.3.

Fig. 5. The dependence of molecular weight Mn (determined from GPC) and the molecular weight polydispersity (Mw/Mn) upon the monomer conversion for copolymerization of PHFBMA-b-PGMA at 30 8C (the solid line represented the theoretical molecular weight at certain monomer conversion, the solid square represented the molecular weight and the hollow triangle represented the polydispersity).

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between the contact angle and surface energy can be expressed by the Yong’s equation and the Fowkes theory [37,38]: 0:5

1 þ cosu ¼

2ðg dsv  g 1p Þ

g lv

0:5

þ

p 2ðg sv  g 1p Þ

(1)

g lv

g sv ¼ g dsv þ g svp

Fig. 6. 1H NMR spectrum for ring-opened copolymer PHFBMA-b-PGMA(OH). The spectrum of product was recorded in deuterated DMSO.

2.3. Hydrolysis of PHFBMA-b-PGMA The ring-opening reaction of diblock copolymer was carried out according to the literature [36] and characterized by 1H NMR and FTIR. A typical 1H NMR spectrum of ring-opened copolymer is shown in Fig. 6. Compared with its precursor, the signals of epoxy in PGMA at 3.22, 2.83, 2.62 ppm disappear completely, which indicated the successful ring-opening reaction under an acid aqueous solution. And new peaks are observed at 5.49 ppm representing the hydroxyl groups, 3.75–4.08 ppm representing methylene protons next to the ester groups, the methine and methylene protons next to the hydroxyl groups. Compared with the FTIR spectra of PHFBMA-b-PGMA and ringopened polymer (spectra b and c in Fig. 2), a broad peak at 3700– 3200 cm1 attributed to the vibration of hydroxyl groups is observed in spectra c, and the absorbance band of epoxy group (907 cm1) corresponding to asymmetric stretching of disappears completely. The GPC trace in Fig. 3c shows that the molecular weight distribution of ring-opened polymer is a little broad comparing with its precursors, which is probably attributed to the hydrogen bonding interactions between hydroxyl groups. All these results proved successful hydrolysis of copolymer PHFBMA-bPGMA. The hydroxyl groups on the side chain can supply many hydrophilic active sites in copolymer structure, which can further investigate the surface property and the phenomenon of microphase separation. 2.4. Surface properties of fluoropolymers It is well-known that the biggest advantage of fluorinated polymer is low surface energy, and the surface free energy for the solid materials is the important factor to influence the wetting property and adhesion property, so it is of great significance to use the contact angle of solid–liquid surface to characterize the wetting property and the surface free energy. The relationship

(2)

where u, glv, gsv are the contact angle, the interfacial tensions of liquid–vapor interfaces, the interfacial tensions of solid–vapor interfaces, and the superscripts d and p represent the dispersion force and polar force of solid or liquid surfaces, respectively. Table 2 summarizes the comparison of surface free energies calculated from contact angle for the surfaces of homopolymer and copolymers. It can be observed from this table that the contact angles of water and diiodomethane are gradually decreased with the fluorine relative content decreasing, which is consistent with other results [19,39]. The fluorinated homopolymer has high fluorine relative content, so it can keep low surface free energy and self-aggregate property and lead to high contact angles, which can show the advantage of the fluorinated polymers. After copolymerizing the other chain onto the homopolymer, the relative content of fluorine is obviously reduced compared to its precursor, and thus the contact angles also decrease. Even though the contact angles of CH2I2 decline gradually and show weak oleophobic property, the reducing rate of the water contact angles is slow and the value of contact angle has no less than 808. This result can be attributed to the process of the film formation. The process of the film formation existed the pull–push force in solution state, the fluorinecontaining segments whose polarity was completely different with the common carbon-hydrogen chain had enough time to automatically arranged around the air-polymer interface in order to keep the lowest interface energy under the thermodynamic driving force. So when the polymer contained the more content of the fluorine atom, the air-polymer interface was aggregated more hydrophobic fluorine-containing segments and the water contact angles had the more bigger values, such as PHFBMA-b-PGMA and PHFBMA. When the polymer contained some polar segments, such as hydroxyl groups, the water contact angles were reduced to about 84.38. Because the dropped water preferentially contacted with the polar segments and decreased the hydrophobic property. However, the water contact angles of the ring-opened copolymers was not reduced dramatically according to the experimental results. That may be ascribed to have the enough content of fluorine-containing components on the liquid–solid u interface region as well as to have a little surface roughness caused by the copolymer’s polarity in THF [40,41]. And the wettability of a film is closely related to the content of the fluorine composition and the surface roughness according to the references [42,43]. What’s more, both of dispersion force and polar force gradually decline as the relative contents of fluorine decrease, this tendency is similar to the change of the contact angles as well as the surface free energy for solid. These experimental data have a good correspondence with the fluorine content and the contact angles, which is consistent with the result of Han group [19].

Table 2 The fluorine content, contact angle and surface properties of a series of copolymers. Sample

WF (%)

u (H2O) (8)

u (CH2I2) (8)

gd (mN m1)

gp (mN m1)

gsv (mN m1)

PHFBMA75-Br PHFBMA75-b-PGMA52 PHFBMA75-b-PGMA52(OH)

39.1 27.4 24.5

99.2  1 93.1  1 84.3  2

77.6  1 71.2  1 60.4  2

16.63 19.29 23.69

2.61 3.80 5.87

19.24 23.09 29.54

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the fluorinated ethyl, or the ethyl pendant chain [44]. The second stage is attributed to the cleavage of part of the side chain and degradation of the main chain. These similar results are reported in other references [25,45]. The degradation pattern for copolymer is also seen in Fig. 7. The single-step degradation is observed at about 255 8C which is higher than that of homopolymer, and the difference for this result might be the different micro-structure and higher molecular weight. On the other hand, the ring-opened polymer shows the highest starting temperature for weight loss at about 310 8C. This result may be due to the different structure of the end monomer unit containing fluorinated segments and hydroxyl groups in the side chain, which is also reported by other researchers [46,47]. 2.6. Self-assembly behavior of copolymer PHFBMA-b-PGMA(OH) in water

Fig. 7. TGA thermograms of PHFBMA75-Br, PHFBMA75-b-PGMA52 and PHFBMA75-bPGMA(OH)52.

2.5. Thermal property of polymers The thermal property of fluorinated copolymer materials is an important parameter, because it can determine their application scope. So we examined the thermal behaviors of PHFBMA, PHFBMA-b-PGMA and PHFBMA-b-PGMA(OH) by thermo-gravimetric analysis (TGA). Fig. 7 shows typical weight loss against temperature curves for three polymers. The curves show that the decomposition of the homopolymer shows two stages. The first temperature of the weight loss is about 202 8C and the second plateau is about 310 8C. The weight loss for the first stage can be associated with end groups which may be the ester groups between the ester group and

In this study, the structure of the ring-opened copolymer with two different units on each chain, one is PHFBMA and the other is PGMA(OH). The fluorinated segments have a strong hydrophobic property which can form the core in the selective solvent. While this copolymer contains many hydroxyl groups on the side chains, which can supply the hydrophilic structure and then can be soluble in dilute aqueous solution to form the shell. In order to investigate the morphology of self-assembly for the copolymer in water solution, the micelle solution was prepared by subsequent addition of water into polymer/THF solution with a long time under stirring drastically. The TEM micrograph is shown in Fig. 8, the scale bar in the figure (a) represents 200 nm and the other in the figure (b) represents 100 nm. It can be seen that some similar spherical shapes with core–shell structure (the white color in the middle and the black background around the spheres) are found in images (a) and (b), even though they are not very homogeneous structures. It could be explained that the fluorinecontaining segment is insoluble in water and then curls up to be

Fig. 8. TEM micrographs of the PHFBMA75-b-PGMA(OH)52 block copolymer using phosphotungstic acid negative staining (pH = 7): (a) micelles, Bar = 200 nm; (b) the highmagnification image of the micelles (a), Bar = 100 nm.

Fig. 9. A schematic diagram for the self-assembly of the block copolymer.

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random coils during the self-assembly process, while the hydrophilic moiety can be miscible with water and then stretches on the outside. This morphology is closely related with its structure, and the schematic diagram for the self-assembly of the block copolymer into micelle structure is shown in Fig. 9. Meanwhile, the sizes of these hollow micro-spheres are nearly homogeneous even though there are some small particles and the mean diameter is 50–80 nm, which can be measured from figure (b). According to the DP of this polymer, the total theoretical bond length of carbon-carbon skeleton for a polymer chain and the value is about 20 nm, which is smaller than that of the TEM micrograph observed. The reason may be ascribed to aggregate the particles in aqueous solution during the self-assembly process. 3. Conclusions A block fluorine-containing copolymer with epoxy group on the side chain was prepared by consecutive ATRP method. The welldefined macroinitiator and copolymer had been characterized by FTIR, 1H NMR and GPC. The polymerization was proved to be a controlled process. The ring-opened copolymer with two hydroxyl groups on the side chain of each unit could give the copolymer weak hydrophilic property. Fluorinated copolymers with lower fluorine content and smaller contact angles can improve the solubility and hydrophilic property as well as maintain the advantages of the fluoropolymers. The ring-opened polymer had the largest dispersion force and polar force. Moreover, TGA testing showed that the copolymers had a higher degradation temperature. TEM observation of the self-assembly structure of the copolymer in water indicated that microspheres with core–shell morphology were embedded in the stable micelles when the final copolymer concentration of aqueous solution was 1 wt%. 4. Experimental 4.1. Materials Monomers 2,2,3,4,4,4-hexafluorobutyl methacrylate (HFBMA) (Xeogia Fluorine-Silicon Chemical Co. Ltd., China) and glycidyl methacrylate (GMA) (Duodian Co. Ltd., Nanjing) were passed through a column of alumina powder to remove the inhibitor then purified by vacuum-distilled and stored in refrigerator. Initiator ethyl 2-bromoisobutyrate (EBB, 98%; Aladdin Co.) and ligand N,N,N0 ,N0 ,N00 -pentamethyldiehtylenetriamine (PMDETA, 99%; Aladdin Co.) were used as received. Catalysts CuBr and CuCl were purified by washing with glacial acetic acid in 90 8C for 8 h, and then washed by acetone and ethyl ether for 4 times before drying two days under vacuum. 2,20 -bipyridyl (Bpy, 98%; Aladdin Co.) was recrystallized in n-hexane and then dried in a vacuum oven to constant weight. Cyclohexanone, biphenyl ether and 2-butanone were dried through CaH2 for 24 h and then distilled. Other reagents were of analytical grade and used as received. 4.2. Synthesis of PHFBMA as a macroinitiator agent by ATRP The typical reaction for preparing the macroinitiator PHFBMABr was prepared by ATRP in cyclohexanone using CuBr as a catalyst in the present of Bpy. The reaction was performed in a home-made two-flask set, connecting two 25 mL round bottom flasks via a glass pipe. Cyclohexanone (7 mL), EBB (0.0395 g, 0.2 mmol), HFBMA (6.00 g, 24 mmol) and Bpy (0.0628 g, 0.4 mmol) were added in one flask, while CuBr (0.0291 g, 0.2 mmol) was loaded into the other flask equipped with a magnetic stirrer. After three freeze–pump– thaw cycles, the liquid mixture was carefully transferred to the flask containing catalyst and put into a preheated oil bath at 75 8C. The polymerization was stopped by transferring the flask into

liquid nitrogen before exposure to air, then diluted with THF and passed through a neutral alumina column to remove the copper complex. The filtrate was concentrated with rotary-evaporation before precipitated in hexane. The crude product was purified for 3 times by dissolving in THF and precipitated in a large amount of hexane, and then dried 24 h under vacuum to get white powder. The conversion of polymer was determined by 1H NMR spectroscopy of the sample, which was taken from the polymerization mixture before stopped in liquid nitrogen. 1H NMR (400 MHz, CDCl3, d): 4.8–5.0 (d, H, –CHF–), 4.3 (s, 2 H, –OCH2–CF2–), 4.1–4.2 (m, 2H, –OCH2–CH3), 1.8–2.0 (m, 2H, –CH2–), 0.75–1.3 (m, 3H, – CH3). IR (KBr): y = 1750 (s), y = 1290 (s), 685 cm1 (m). On the basis of 1H NMR result, the conversion was about 62.5% by calculating the ratio both the area of the chemical shift of 4.8– 5.0 ppm of –CHF– for PHFBMA and that of 4.0–4.1 ppm of –CH2– for EBB. And the actual DP of PHFBMA-Br was 75, the product was denoted as PHFBMA75-Br. 4.3. Copolymerization of PHFBMA-b-PGMA by consecutive ATRP In a representative run, 2-butanone (2.6 mL), diphenyl ether (2.2 mL), GMA (0.600 g, 4.216 mmol), PHFBMA-Br (1.000 g, 0.0527 mmol), PMDETA (0.0210 g, 0.121 mmol) were added in one flask and CuCl (0.0055 g, 0.0556 mmol) was added into the other flask. After bubbled for half an hour with argon and three freeze–pump–thaw cycles, the liquid reactants were transferred into the flask containing catalyst CuCl. The light green solution was stirred in a preheated oil bath at 30 8C. Samples were withdrawn at different intervals for conversion analysis (1H NMR) and molecular weight (GPC). When the reaction ended, the mixture was stopped in liquid nitrogen and exposure to the air. After diluted with dichloromethane and removed the copper complex, the concentrated liquid was dissolved in CH2Cl2 and precipitated in hexane for 3 times before vacuum drying to constant weight. 1H NMR (400 MHz, CDCl3, d): 4.8–5.0 (d, 1 H, –CHF–), 4.3 (–OCH2–CF2–, –OCH2–CH–), 3.7 (s, 2H, –OCH2–CH–), 3.2 (s, 1H, –CH2–CH–O–), 2.8, 2.6 (d, 1H, –CH–CH2–O–), 1.8–2.0 (m, 2H, –CH2–), 0.8–1.3 (m, 2H, –CH3). FTIR (KBr): 907 cm1, 844 cm1, 755 cm1 (epoxy group). On the basis of 1H NMR result, the conversion was about 65.3% by calculating the ratio both the area of the chemical shift of 4.8–5.0 ppm of –CHF– for PHFBMA and that of 3.2 ppm of –CH– for PGMA. And the actual DP of PGMA was 52, the product was denoted as PHFBMA75-b-PGMA52. 4.4. Hydrolysis of copolymer PHFBMA-b-PGMA Hydrolysis of epoxy groups can be finished according to Ref. [36]. PHFBMA-b-PGMA (0.41 g), THF (12 mL) and acetic acid (24 mL) were mixed in a 150 mL round bottom flask. The reaction mixture was placed in an oil bath at 50 8C, followed by the slow addition of 39 mL water. After stirring for 24 h at 50 8C, the solvent was removed by a rotary evaporator. The isolated polymer was precipitated from THF into hexane for 3 times and dried under vacuum to constant weight. Yield was 0.38 g (93 wt%). 4.5. Instrumentation All 1H NMR spectra were recorded on a Bruker DMX-400 spectrometer in CDCl3 or deuterated DMSO as the solvents and tetramethylsilane as an internal reference. The apparent molecular weights (Mn) and molecular weight distributions (Mw/Mn) of the polymers were measured at 35 8C with a gel permeation chromatograph (GPC) by a Waters 1515 series GPC system, equipped with a Waters 717 autosampler and a Waters 2414 refractive index (RI) detector and a set column of styragel HR4 and HR3. THF was used as eluent at a flow rate of 1.0 mL/min and

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polystyrene as the calibration standards. Fourier transform infrared absorption spectrum (FTIR) was obtained using Bruker TENSOR 27 (Germany) at a scan range of 500–4000 cm1. The films for FTIR were prepared by mixing sample and KBr then pressed to a circular sheet before testing. The contact angle was obtained on the air-side surface of the coating film with a contact goniometer JC2000D1 (Powereach Digital Technology equipment Co. Ltd. in Shanghai, China) by a drop-shape method. The polymer was dissolved in THF at 1.5 g mL1 and stirred for 24 h followed by being dropped onto the already processed glass slides, and then evaporated the organic solvent in a sealed glass container at room temperature for 2 days. The films were dried in vacuum at 40 8C for 2 days and then cooled to room temperature before testing. The films were used to test the contact angles at least ten different positions for the same film (5 mL, pure water or CH2I2). In order to ensure that the results were sufficiently credible, the experimental errors in measuring the contact angles were evaluated to be less than  28. Fluorine content was obtained through X-ray energy dispersive analysis (HORIBA, Ltd., Japan). Thermo-gravimetric analysis (TGA) was performed on a thermoanalyzer system (TG209F3, Netzsch Co. Ltd., Germany) by heating from room temperature to 800 8C at a rate of 10 8C/min1 under nitrogen atmosphere. All samples were dried in vacuum for 48 h at 35 8C before testing. Transmission electron micrograph (TEM) images were obtained on a JEM-100CXII at an operating voltage of 200 kV. The TEM specimens were prepared by depositing solution containing 1 wt% of polymer solution on coating 200 meshes Formvar coated grids and dried in vacuum desiccators at room temperature. The specimen was stained by phosphotungstic acid (PTA, 1.5 wt% aqueous solution, pH = 7) for 3 min. References [1] A. Bruno, Macromolecules 43 (2010) 10163–10184. [2] R. Kaplanek, O. Paleta, J. Michalek, M.J. Pradny, J. Fluorine Chem. 126 (2005) 593–598. [3] L. Tong, Z. Shen, S. Zhang, Y.J. Li, G.L. Lu, X.Y. Huang, Polymer 49 (2008) 4534–4540. [4] T. Cai, K.G. Neoh, E.T. Kang, Langmuir 27 (2011) 2936–2945. [5] E.M.W. Tsang, Z.B. Zhang, A.C.C. Yang, Z.Q. Shi, T.J. Peckham, R. Narimani, B.J. Frisken, S. Holdcroft, Macromolecules 42 (2009) 9467–9480. [6] L.M. Tang, Y. Li, X.M. Wu, X.F. Shan, W.C. Wang, Adv. Powder Technol. 15 (2004) 39–42. [7] J. Eastoe, S. Gold, D.C. Steytler, Langmuir 22 (2006) 9832–9842. [8] J.E. Hensley, J.D. Way, Chem. Mater. 19 (2007) 4576–4584. [9] J.G. Riess, Curr. Opin. Colloid Interface Sci. 14 (2009) 294–304.

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