Syntheses and properties of amphiphilic poly (diethyl vinylphosphonate-co-2-chloroethyl methacrylate) copolymers

Abstract

Poly (diethyl vinylphosphonate-co-2-chloroethyl methacrylate) (P(DEVP-co-CEMA)) copolymers are synthesized by free radical copolymerization initiated by benzoyl peroxide. The reactivity ratios for the free radical copolymerization of CEMA (M₁) and DEVP (M₂) are r₁ = 19.45 and r₂ = 0.11, respectively. The desired amphiphilic copolymers with relatively low polydispersity index (PDI) and different DEVP contents are isolated and purified from the reaction mixtures through precipitation fractionation. The structures and molecular characteristics of the obtained products are characterized by ¹H NMR, FTIR, and SEC analysis. All of these fractionated copolymers have a unimodal distribution and moderate PDI. The thermal properties of the P(DEVP-co-CEMA) copolymers are investigated by TGA and differential scanning calorimetry (DSC) measurements. Single glass transition temperature (T_g) appears in the DSC profiles differing from the existence of two T_gs in the blend of poly (diethyl vinylphosphonate) and poly (2-chloroethyl methacrylate), which indicates the random structure of the copolymers. The MALDI–ToF mass analysis further reveals that DEVP and CEMA units are randomly distributed in the copolymer chains. The self-assembly behavior of the P(DEVP-co-CEMA) copolymers in aqueous solution is preliminarily investigated.

Keywords:

• amphiphilic copolymers
• 2-chloroethyl methacrylate
• diethyl vinylphosphonate
• phosphorus-containing polymers
• radical polymerization
• self-assembly

Introduction

Phosphorus-containing polymers are particularly attractive for their extensive application in fuel cells,[1–6] flame retardant [7–10], and the biomedical field.[11,12] Phosphorus-containing polymers include genetic materials DNA and RNA,[13] and synthetic polymers functionalized at the main chain (e.g. polyphosphazene [14,15] polyphosphoesters [16]) and those functionalized at the side chain. Vinylphosphonate is one of the simplest vinyl monomers with the phosphonate groups at the side chain. Since the late 1940s, different routes for vinylphosphonate synthesis have been reported.[17–21] Researches on the polymerization of vinylphosphonates are following shortly after.[21,22] So far, quite a number of reports have been published investigating the polymerization of vinylphosphonates with the methods of radical,[17,21–24] anionic,[25–27] coordinative-anionic,[28] and living rare earth metal-mediated group transfer polymerization.[29–38] Among these techniques, coordinative-anionic polymerization and living rare earth metal-mediated group transfer polymerization are efficient to generate poly(vinylphosphonates) with higher molecular weight and higher conversions. Except for poly(vinylphosphonic acid) (which can be obtained in high yield and moderate molecular weight by free radical polymerization),[39,40] relatively few investigations into the homo and copolymerization of vinylphosphonate monomers via radical polymerization have been reported. The few reports show that vinylphosphonate monomers fail to homopolymerize to high molecular weight products by the method of radical polymerization (especially for diethyl vinylphosphonate (DEVP)), which usually lead to low yields and provide polymers of low molecular weight.[17,21–24] In the case of radical copolymerization, the final results were either unsuccessful or afforded insufficient characterization.[24,29,41,42] Arcus reported the copolymerization of DEVP with styrene initiated by tert-butyl hydroperoxide and determined the reactivity ratios of this monomer pair. For relatively low DEVP contents in the copolymers, DEVP is reluctant to enter the growing polymer chain as compared to styrene.[42,43] Except for styrene, radical copolymerizations of DEVP with ethylene glycol dimethacrylate,[41] methyl methacrylate ,[44] acrylonitrile,[44] and trimethoxyvinylsilane [24] are achieved, but afford inadequate characterization. Therefore, radical copolymerizations of DEVP with other monomers to get relatively high DEVP-containing copolymers with clearly characterized structure are still a significant and challenging issue.

The monomer 2-chloroethyl methacrylate (CEMA) is of special interest as halogen-functionalized comonomer for easy modification and post cross-linking.[45–47] With initiating haloalkyl groups, graft copolymers can be prepared via atom transfer radical polymerization (ATRP).[48] The chlorine atoms can be readily substituted by nucleophiles, for instance, azide groups, and then followed by click coupling of alkyne end-functionalized polymers to gain new properties.[49,50] Therefore, CEMA is a potential comonomer for DEVP to broaden the applications of phosphorus-containing polymers. To date, to the best of our knowledge, there is no report on the copolymerization of DEVP with CEMA. What is more, due to the existence of both hydrophobic units (CEMA) and hydrophilic units (DEVP), the copolymers are able to self-assemble into nanoparticles in aqueous solution, which are promising in the fields such as microreactors and encapsulation of guest molecules. The modified copolymers show great potential in biomedical fields for polyphosphonates and proved to be high biocompatibility and adjustable degradability.[11,12] Meanwhile, the chemical incorporation of a phosphorus-containing flame retardant into a methacrylate polymer via copolymerization may eliminate the leaching and heterogeneous problems associated with the additive approach.[9,51]

Herein, we synthesize a series of amphiphilic random copolymers, namely poly (diethyl vinylphosphonate-co-2-chloroethyl methacrylate) (P(DEVP-co-CEMA)), through free radical copolymerization using benzoyl peroxide (BPO) as initiator. The synthesis route of these random copolymers is presented in Scheme 1. Copolymers with relatively narrow molecular weight distribution are isolated through precipitation fractionation for the detailed investigation. The structures of the copolymers are confirmed by ¹H NMR, ³¹P NMR, Fourier transform infrared (FTIR), and MALDI–ToF mass analysis. The thermal properties of P(DEVP-co-CEMA) copolymers are determined by differential scanning calorimetry (DSC) and thermogravimetric analyses (TGA) measurements. Preliminary investigations on self-assembly behaviors of the copolymers in water are also performed, and the nanoparticles formed in water are observed by TEM.

Experimental

Materials

Triethyl phosphite (98.0%, Aladdin Reagent, China), ethylene bromide (99.0%, Aladdin Reagent, China), triethylamine (Sinopharm Chemical Reagent, China), benzene (Sinopharm Chemical Reagent, China), methacryloyl chloride (J&K Chemical Reagent, China), and 2-chloroethanol (Shanghai Nanxiang Reagent, China) were used as received. BPO (Shanghai Lingfeng Chemical Reagent, China) was recrystallized from methanol twice before use. THF was refluxed over potassium/benzophenone ketyl before use. All the other chemicals were used as received unless otherwise specified.

Synthesis of CEMA

2-chloroethanol (10 mL) and triethylamine (22 mL) were dissolved in THF (50 mL), then methacryloyl chloride (15 mL) was added slowly under argon atmosphere while cooling the solution in an ice bath. The reaction mixture was stirred for 48 h at room temperature and then filtered. The filtrate was washed thoroughly with deionized water and dried with anhydrous sodium sulfate. The pure product CEMA was obtained by distillation under reduced pressure as colorless liquid, bp: 38–40 °C/0.1 mbar. ¹H NMR (400 MHz, CDCl₃, δ): 6.16 (s, 1H, CH₂=), 5.61 (s, 1H, CH₂=), 4.40 (t, 2H, –OCH₂–), 3.73 (t, 2H, –CH₂Cl), 1.95 ppm (s, 3H, –CH₃). ¹³C NMR (400 MHz, CDCl₃, δ): 166.9 (s, C=O), 135.8 (s, CH), 126.3 (s, CH₂), 64.2 (s, CH₂O), 18.2 ppm (s, CH₂Cl).

Synthesis of DEVP

DEVP was prepared using the synthetic route we had reported before.[28] Raw diethyl 2-bromoethylphosphonate (165.7 g) was prepared in 79% yield from triethyl phosphite (142.9 g) and ethylene bromide (327.4 g), and converted in 48% yield into DEVP by Kosolapoff’s methods.[21] Then the crude product was distilled at 60–62 °C/0.1 mbar, and pure DEVP (60 g) was obtained. ¹H NMR (400 MHz, CDCl₃, δ): 1.34 (t, 6H, –CH₃), 4.10 (m, 4H, –CH₂O–), 6.19 ppm (m, 3H, –CH=CH₂). ¹³C NMR (400 MHz, CDCl₃, δ): 135.4 (s, CH₂), 126.8, 125.0 (d, PCH), 61.8 (d, CH₂O), 16.3 (d, CH₃). ³¹P NMR (400 MHz, CDCl₃, δ): 17.2 ppm.

Synthesis and fractionation of P(DEVP-co-CEMA) copolymer

A solution of DEVP (0.508 g), CEMA (0.233 g), and BPO (8 mg) in THF (3.5 mL) was introduced in a sealed tube and degassed by means of three freeze/pump/thaw cycles. The reaction mixture was then placed in a preheated (60 °C) oil bath; the reactant was allowed to cool to room temperature after reacted for 24 h, and the crude copolymer was precipitated in hexane. The desired amphiphilic P(DEVP-co-CEMA) copolymer was obtained by further precipitation fractionation using methanol/THF as nonsolvent-solvent system. The crude copolymer was dissolved in 5 mL THF, and then 50 mL methanol was added to the solution. Finally, the mixture became turbid, and the higher MW precipitate was separated through centrifugation. After centrifugation, the supernatant clear liquid was transferred to a round-bottom flask, and the organic solvents were removed using rotary evaporator. The residuum in flask was dissolved in THF, precipitated in hexane, and repeated three times. The final product was then filtered and dried under vacuum, to give a white powder.

Preparation of a self-assembly system

The assemblies were prepared using the typical procedure as follows: 2 mg copolymer was dissolved in 1 mL THF and followed by the addition of water dropwise to the desired water contents, then dialyzed against deionized water for three  days to exclude the organic solvent. Regenerated cellulose dialysis tubes were used, and the specific molecular weight cut-off is 1000.

Measurements

¹H NMR, ¹³C NMR, and ³¹P NMR spectra were recorded on Bruker Avance III 400 spectrometers using CDCl₃ as solvent and tetramethylsilane as internal reference. FTIR spectra were obtained with a Bruker Vector 22 FTIR spectrometer by signal averaging a total of 32 scans. Thin films were prepared by casting polymer/THF solutions onto KBr discs. Size exclusion chromatography (SEC) was performed on a Waters-150C apparatus in THF at a flow rate of 1.0 mL min⁻¹ at 40 °C using narrow MWD polystyrene standards. DSC analyses were performed on a TA Q20 instrument. Samples were heated from −80 to 200 °C at a rate of 10 °C min⁻¹ under a nitrogen purge, quenched to −75 °C and subjected to a second scan. The second thermo-scanning curves were recorded. TGA were performed on a TA Q50 instrument. Samples were first holding for 10 min at 150 °C and then heated from 50 to 600 °C at a rate of 10 °C min⁻¹ under a nitrogen purge. The hydrodynamic diameters of the nanoparticles were measured by dynamic light scattering (DLS) using a particle size analyzer (Zetasizer Nano Series, Malvern Instruments) at 25 °C. The measurements were taken at a fixed angle at 90° and a wavelength of 657 nm. The morphologies of nanoparticles in water were observed on JEOL JEM-1230 (HR) TEM instrument with the accelerating voltage of 80 kV. The samples were prepared by placing the solution on copper grids coated with carbon-film. After the solvent evaporated naturally, they were stained with one drop of phosphotungstic acid aqueous solution and dried under ambient condition. Matrix-assisted laser desorption/ionization time of fight (MALDI–ToF) mass spectra were collected on a Bruker UltraFLEX MALDI–ToF mass spectrometer. All polymer (3–5 mg mL⁻¹ in THF) mass spectra were recorded in the reflection mode with an acceleration voltage of 20 kV. Dithranol (36 mg mL⁻¹ in THF) was used as a matrix.

Results and discussion

Synthesis and characterization of P(DEVP-co-CEMA)

CEMA and DEVP monomers were prepared according to the procedures described in literatures [18,42,50,52] and our previous work.[28] The structures of the monomers are clearly confirmed by ¹H NMR, ¹³C NMR, and ³¹P NMR (Figures S1–S5 in Supplementary Information). Homo and copolymerization of DEVP and CEMA were carried out in THF at 60 and 50 °C initiated by BPO, and the results are summarized in Table 1. CEMA showed high reactivity for radical homopolymerization, and poly (2-chloroethyl methacrylate) (PCEMA) with high yield (85.6%) and high MW (67.0 kDa) was prepared (Sample P9 in Table 1), while only oligomers (0.4 kDa) were obtained in the case of DEVP homopolymerization (Sample P8 in Table 1). This low reactivity of DEVP is consistent with the results reported before.[17,21–24] The structures of PCEMA and PDEVP are confirmed by ¹H NMR (Figures S6 and S7) measurements. However, P(DEVP-co-CEMA) copolymers were obtained successfully by copolymerization of DEVP and CEMA; the copolymer was precipitated in hexane, which is the poor solvent for both DEVP and CEMA segments. The copolymerization yields vary between 26.6% (Sample P3) and 65.8% (Sample P4), and decrease noticeably with the increasing of initial DEVP feed molar ratios, due to the low reactivity of DEVP. The reaction temperature also influences the copolymerization results obviously. Lower temperature (50 °C) leads to higher MWs, but lower yields and DEVP contents (Sample P1–3, Table 1). From Table1, it can be seen that MWs decrease sharply with the increasing of the DEVP feed molar ratios, while DEVP contents in the copolymer increase correspondingly.

Table 1. Homo and copolymerization of DEVP and CEMA initiated by BPO^a.

Sample	DEVP:CEMA (molar ratio)		Temp. (°C)	Mn^c (kDa)	PDI^c	Yield^d (%)	Tg (°C)
	Feed	Copolymer^b
P1	1:2	0.005:1	50	33.6	3.81	54.3	71.0
P2	1:1	0.065:1	50	14.5	2.10	40.0	72.7
P3	2:1	0.105:1	50	8.0	1.83	26.6	55.9
P4	1:2	0.040:1	60	16.0	4.34	65.8	66.7
P5	1:1	0.103:1	60	7.1	2.58	56.1	52.4
P6	2:1	0.192:1	60	4.1	2.01	53.6	36.5
P7	3:1	0.420:1	60	1.8	1.81	38.5	33.4
P8	1:0	–	60	0.4	1.01	14.1	–
P9	0:1	–	60	67.0	2.15	85.6	95.0

^a Polymerized in THF for 24 h and precipitated by hexane.

^b As calculated by ¹H NMR analyses.

^c As determined by SEC.

^d As determined by gravimetry.

The ¹H NMR spectrum (Figure 1(A)) demonstrates the presence of DEVP units in copolymer chains, which can be confirmed from the signals lined out at 4.1 and 1.3 ppm assigned to –OCH₂– and –OCH₂CH₃ in DEVP segments. The ³¹P NMR spectra (Figures S8–S13) show signals in the 28–36 ppm region, these results further confirm the presence of DEVP units. The characteristic absorption bands of DEVP units (υ_P–O = 1027 and 1052 cm⁻¹, υ_P=O = 1228 cm⁻¹) also appear clearly in the FTIR spectrum (Figure 2(A)). The copolymer compositions (DEVP:CEMA) range from 0.005:1 to 0.42:1 (molar ratio, Table 1), which deviates much from the feed molar ratios for the low reactivity of the DEVP. DSC analyses indicate that all of the copolymers prepared have single glass transition temperature (T_g), which ranges from 72.7 to 33.4 °C and decrease with the increasing of DEVP contents (Table 1). For instance, DSC profile of Sample P1 (Figure 3(A)) shows that the copolymer has a single T_g around 71 °C differing from the appearance of two T_gs in the blend of PCEMA and PDEVP (Figure 3(C)), which indicates the formation of the copolymers.

Figure 1. ¹H NMR spectra of Sample P1 (A) and Sample F1 (B).

Figure 2. FTIR spectra of Sample P1 (A) and Sample F1 (B).

Figure 3. DSC profiles of Sample P1 (A), F1 (B), and the blend of PCEMA and PDEVP (C).

To quantify the reactivity difference between the two monomers, reactivity ratios of CEMA and DEVP were determined by the Finemann and Ross method,[53] which was based on the results of ¹H NMR analysis. The monomer reactivity ratios for the free radical copolymerization of CEMA (M₁) and DEVP (M₂) are r₁ = 19.45 and r₂ = 0.11 (Table S1 and Figure S14), indicating that the copolymerization should produce long blocks of CEMA and randomly distributed short blocks of DEVP.

Although the P(DEVP-co-CEMA) copolymers have been synthesized successfully, and the structures of copolymers have been confirmed by NMR, FTIR, and DSC measurements, SEC traces (Figure 4(A), Figures S15A–S20A) of the unfractionated copolymers precipitated in hexane show multicomponents and quite broad MW distribution. To obtain the copolymer with higher DEVP content and narrower MW distribution, methanol and THF are selected as the nonsolvent-solvent system for the precipitation fractionation. DEVP-rich copolymer fractions with comparatively narrow MW distribution are isolated and purified according to the methods described in the experimental part, and the results are listed in Table 2. For instance, the fractionated copolymer sample F1 has a higher DEVP:CEMA (0.060:1) and a narrower MW distribution polydispersity index (PDI = 1.30) as compared to sample P1 (DEVP:CEMA = 0.005:1, PDI = 3.81) according to the ¹H NMR spectrum (Figure 1(B)) and SEC trace (Figure 4(B)).

Figure 4. SEC traces of Sample P1 (A) and Sample F1 (B).

Table 2. Characterization of low MW fractions of P(DEVP-co-CEMA)^a.

Sample	DEVP:CEMA (molar ratio)		Temp. (°C)	Mn^c (kDa)	PDI^c	Fractionation ratio^d (%)	Tg (°C)
	Feed	Copolymer^b
F1	1:2	0.060:1	50	3.5	1.30	10.2	38.2
F2	1:1	0.110:1	50	3.9	1.31	29.1	48.1
F3	2:1	0.125:1	50	4.6	1.34	50.0	54.2
F4	1:2	0.115:1	60	2.9	1.38	26.6	42.4
F5	1:1	0.143:1	60	3.1	1.38	42.2	29.1
F6	2:1	0.215:1	60	4.2	1.36	46.9	28.5
F7	3:1	0.420:1	60	2.4	1.48	95.1	33.4

^a Fractionation system: methanol/THF.

^b As calculated by ¹H NMR analyses (polymer fractionated).

^c As determined by SEC (polymer fractionated).

^d As determined by gravimetry.

Due to the fractionation, the MWs and polydispersities of the copolymers fractionated are not much different. SEC measurements indicate that all the copolymers have a similar unimodal distribution after fractionation as shown in Figure 4(B), as well as other samples shown in Supplementary Information (Figures S15B–S20B). The MWs of the copolymers are ranging from 2.4 to 4.6 kDa. All the copolymers of CEMA and DEVP exhibit moderate PDIs (1.31–1.48). The copolymer compositions (DEVP:CEMA) range from 0.06:1 to 0.42:1 (molar ratio, Table 2), which are also lower than the initial monomer feed ratios, but still remain positive relationship. The chemical structures of copolymer P(DEVP-co-CEMA) are confirmed by FTIR and ¹H NMR analyses. The FTIR spectrum of P(DEVP-co-CEMA) copolymer (Sample F1 in Table 2) is shown in Figure 2(B). The characteristic absorption bands of CEMA unit (υ_C=O = 1750 cm⁻¹, υ_C–O = 1140 cm⁻¹, υ_C–Cl = 745 cm⁻¹) appear clearly in the FTIR spectrum. The presence of peaks at 1228, 1027, and 1052 cm⁻¹ is attributed to the P = O, P–O stretching vibration of DEVP unit. The ¹H NMR spectrum of the P(DEVP-co-CEMA) copolymer (Figure 1(B)) exhibits signals from methylene and methine protons in the backbone of both CEMA and DEVP units between 1.5 and 2.5 ppm. The chemical shift at 3.7 ppm is the characteristic peak of the protons of –CH₂Cl of the CEMA segment. The characteristic peak of the protons of –CH₃ of DEVP unit is located at 1.3 ppm. The chemical shifts in the region of 3.9–4.6 ppm are assigned to the protons of –OCH₂– of both CEMA and DEVP units. Three protons of the methyl group of CEMA unit generate a broad doublet in 0.8–1.3 ppm range, which indicates partial isotacticity of the PCEMA structure.

A typical MALDI–ToF mass spectrum of P(DEVP-co-CEMA) (Sample F3 in Table 2) is shown in Figure 5, in which the dithranol (matrix) and the reflection mode are selected for the polymer. Five distinct peaks (A–E) are observed within each repeat signal group. The m/z spacings of 148 between the peak A and A₁, B and B₁, C and C₁, D and D₁, E and E₁ in the spectrum are equal to the mass of CEMA unit. The adjacent peaks (between A and B, B and C, C and D, D and E) are separated by the mass of 16, which are attributed to the mass difference between DEVP unit and CEMA unit. The detailed assignments of each peak are summarized in Table 3. The analysis result of MALDI–ToF mass spectrum indicates that the low weight fractions are random copolymer, namely DEVP and CEMA units are randomly distributed in the copolymer chains.

Figure 5. The MALDI–ToF mass spectrum of Sample F3 in Table 2.

Table 3. Structural assignments of ions appearing in the MALDI–TOF mass spectra of P(DEVP-co-CEMA) (Sample F3 in Table 2).

Peak	Assignment
A	n × MCEMA + m × MDEVP + End group
B	(n-1) × MCEMA + (m + 1) × MDEVP + End group
C	(n-2) × MCEMA + (m + 2) × MDEVP + End group
D	(n-3) × MCEMA + (m + 3) × MDEVP + End group
E	(n-4) × MCEMA + (m + 4) × MDEVP + End group

Thermal properties

DSC analyses of P(DEVP-co-CEMA) copolymers (Sample F1, Table 2) have been performed compared with the blend of PCEMA and PDEVP on thermal behavior. The low MW fractionated copolymer presents an intermediary T_g of 38.2 °C (Figure 3(B)), which is between the T_g of PCEMA (95 °C, M_n = 67.0 kDa) and PDEVP (−3 °C, M_n = 107.3 kDa (Figure S21), obtained from coordinative-anionic polymerization, and the synthetic procedure was described in Supplementary Information.) (Figure 3(C)). The incorporation of DEVP units into the chain of PCEMA lowers the T_g value of PCEMA due to the steric hindrance of phosphonate group. Two T_gs appear clearly in the DSC profile of the blend of PCEMA and PDEVP, which imply the poor compatibility between PCEMA and PDEVP in the blend (Figure 3(C)). Copolymers fractionated (Sample F1–F7) show lower T_gs (28–54 °C) as compared to the products precipitated directly in hexane (Tables 1 and 2), which may attribute to the low MW and narrow molecular weight distribution.

TGA profile of P(DEVP-co-CEMA) copolymer (Figure 6(A)) exhibits a two-step degradation which is quite different from the blend of PCEMA and PDEVP (which shows a three-step degradation) (Figure 6(B)). The first step degradation happens because of the side-chain cleavage for PDEVP according to the theory of Bernhard Rieger.[30] The second degradation step is presumably caused by the main-chain scission of both CEMA and DEVP units. The main decomposition step occurs at 260–370 °C.

Figure 6. TGA profiles of Sample F3 (A) and the blend of PCEMA and PDEVP (B).

Self-assembly behavior of amphiphilic random copolymers

P(DEVP-co-CEMA) is a class of amphiphilic copolymers, so the self-assembly behavior of the copolymers in aqueous solution is investigated. The copolymer aggregates are obtained by adding deionized water dropwise, as a precipitant, to the solutions of P(DEVP-co-CEMA) in THF and then followed by dialysis against deionized water to remove the organic solvent. DLS analyses demonstrate that the sample F3 forms nanoparticles with a size of 207 nm (PDI = 0.036) in aqueous solution (Figure 7). TEM image indicates that regular spherical nanoparticles are formed in water with a diameter of 50 to 200 nm (Figure 7). Sample F6 forms nanoparticles with a diameter of 203 nm (PDI = 0.05) in aqueous solution (Figure S22). The size of the nanoparticles seems to vary little with the tuning of copolymer composition, which may relate to the random structure of the copolymers.

Figure 7. TEM image and the corresponding DLS result of P(DEVP-co-CEMA) (Sample F3 in Table 2) nanoparticles in water.

Scheme 1. A representative reaction procedure for the synthesis of P(DEVP-co-CEMA) copolymers via conventional free radical polymerization.

Conclusions

P(DEVP-co-CEMA) copolymers are successfully synthesized by conventional free radical copolymerization. The amphiphilic copolymers with relatively narrow MW distribution and higher DEVP content are isolated and purified from the reaction mixtures through precipitation fractionation. MALDI–ToF and DSC measurements demonstrate the random structure of the resultant copolymers. The copolymers exhibit a two-step degradation, and the main degradation occurs at about 300 °C. Furthermore, P(DEVP-co-CEMA) copolymers can self-assemble into nanoparticles in aqueous solution for their amphiphilic properties. P(DEVP-co-CEMA) copolymers are of special interest not only for being a class of phosphorus-containing copolymers, but also for the presence of the chlorine atom in the side chain. They can either serve as a macroinitiator for ATRP or become azido functionalities for click chemistry. The modified copolymers show great potential in biomedical fields and flame retardant area.

Supplementary material

The supplementary material for this paper is available online at http://dx.doi.10.1080/15685551.2015.1041078.

Acknowledgments

The authors gratefully acknowledge the financial supports of the National Natural Science Foundation of China (21174121), the Special Funds for Major Basic Research Projects (G2011CB606001), and Zhejiang Provincial Natural Science Foundation of China (LY13B040001).

Additional information

Funding

This work was supported by National Natural Science Foundation of China [grant number 21174121]; the Special Funds for Major Basic Research Projects [grant number G2011CB606001]; Zhejiang Provincial Natural Science Foundation of China [grant number LY13B040001].