O R I G I N A L P A P E R
One-Pot Synthesis of Poly(linoleic
acid)-g-Poly(styrene)-g-Poly(e-caprolactone) Graft Copolymers
Abdulkadir Allı• Sema Allı•C. Remzi Becer• Baki Hazer
Received: 15 August 2013 / Revised: 28 November 2013 / Accepted: 7 January 2014 / Published online: 22 January 2014 Ó AOCS 2014
Abstract One-pot synthesis of graft copolymers by ring-opening polymerization and free radical polymerization using polymeric linoleic acid peroxide (PLina) is reported. Graft copolymers having structures of poly(linoleic acid)-g-polystyrene-g-poly(e-caprolactone) were synthesized from PLina, possessing peroxide groups on the main chain by the combination of free radical polymerization of sty-rene and ring-opening polymerization of e-caprolactone in one-step. Principal parameters, such as monomer concen-tration, initiator concenconcen-tration, and polymerization time, which effect the one-pot polymerization reactions were evaluated. The obtained graft copolymers were character-ized by1H-NMR and DOSY-NMR spectroscopy, gel per-meation chromatography, thermal gravimetric analysis and differential scanning calorimetry techniques.
Keywords Autoxidation One-pot polymerization e-Caprolactone Polymeric linoleic acid peroxides
Introduction
Macroperoxy initiators have been attracting a great deal of attention and are widely used in obtaining block/graft copolymers via free radical polymerization [1–10]. Autoxidation of the polyunsaturated oil is one of the most prevalent ways of synthesizing an oil-based polymer. It is implemented under oxygen and sunlight mainly via hy-droperoxidation, peroxidation, epoxidation, and perepoxi-dation reactions respectively. Polyunsaturated oil acids are used to obtain macroperoxy initiators using this method [11–15]. According to Porter et al. the formed primary products are hydroperoxides, when polyunsaturated fatty acids are subjected to oxidative stress [16,17]. This oxi-dation process is a free radical chain reaction, which targets the nonconjugated diene moieties of polyunsaturated oil [18]. Oxidation is initiated by abstraction of the bis-allylic hydrogen atom generating a radical, which can undergo trapping at either at the terminus or at the central bis-allylic position. The free radical polymerization of vinyl mono-mers can be initiated by these oil acid macroperoxides, leading to graft-shaped copolymers [19–23].
In recent years, a one-pot process has been successfully utilized for the synthesis of block or graft shaped copoly-mers using different techniques, which indeed has several advantages over other widely employed methods [24–26]. Because of the applicability of at least two transformation steps simultaneously, side reactions that lead to homopol-ymer formation are minimized [27–42]. Barner-Kowollik and coworkers carried out the synthesis of poly(2-hydroxyethyl methacrylate-g-e-caprolactone) graft copolymers through the one-pot combination of ring opening polymerization (ROP) and reversible addition fragmentation chain transfer polymerization (RAFT) polymerization in the presence of cyanoisopropyl Electronic supplementary material The online version of this
article (doi:10.1007/s11746-014-2418-1) contains supplementary material, which is available to authorized users.
A. Allı (&) S. Allı
Department of Chemistry, Du¨zce University, 81620 Du¨zce, Turkey
e-mail: abdulkadiralli@yahoo.com; abdulkadiralli@duzce.edu.tr S. Allı B. Hazer
Department of Chemistry, Bu¨lent Ecevit University, 67100 Zonguldak, Turkey
C. R. Becer
School of Engineering and Materials Science, Queen Mary University of London, Mile End Road, London E1 4NS, UK DOI 10.1007/s11746-014-2418-1
dithiobenzoate and tin-2-ethyl hexanoate, using toluene as the solvent [27]. Furthermore, the synthesis of various copolymers containing styrene [28–37], N-isopropylacryl-amide [38,39], lactide [32,37,38,40], e-caprolactone [33,
34, 39], 2-hydroxyethyl methacrylate [33, 34], methyl acrylate [40], 2-hydroxyethyl acrylate [40] and methyl methacrylate [41] have been reported using a combination of the ROP and RAFT polymerization techniques.
Benoit et al. [44] developed a new one-pot strategy for novel functionalized block copolymers. Huang et al. pro-pose a new strategy for the one-pot synthesis of block copolymers by using a combination of conventional free radical or reverse atom transfer radical polymerization (RATRP) and ring opening polymerizations [43]. De Geus et al. [45] investigated the synthetic parameters for the chemoenzymatic cascade synthesis of block copolymers combining enzymatic ring-opening polymerization (EROP) and atom transfer radical polymerization (ATRP) in one pot. Ozturk and Cakmak [46] synthesized multiphase block copolymers having the structure of poly(e-caprolacton-b-ethylene glycol-b-styrene-b-poly(e-caprolacton-b-ethylene glycol-b-e-caprolac-ton) from poly(ethylene oxide) possessing an azo group in the main chain by the combination of free radical merization (FRP) of styrene (St) and ring opening poly-merization (ROP) of e-caprolacton (e-CL) in one-pot.
To the best of our knowledge, there are no reports describing the synthesis of poly(e-caprolactone) copoly-mers containing unsaturated fatty acid polycopoly-mers. Here, we report for the first time one-pot synthesis of PLina-g-PCL and PLina-g-PSt-g-PCL graft copolymers by ROP of e-caprolactone initiated from the carboxylic acid groups of PLina. In addition, PLina-g-PSt-g-PCL graft copolymers were synthesized by free radical polymerization of styrene initiated by the peroxy groups of PLina.
Materials and Methods Materials
Linoleic acid (cis–cis-9-12-octadecadienoic acid) was supplied by Fluka (Steinheim, Germany), and used as received. e-caprolactone (e-CL) was supplied by Aldrich and dried over anhydrous CaSO4 and then fractionally distilled prior to use. Styrene (S) was supplied by Aldrich, which was purified extensively by washing with 10 wt% aqueous NaOH solution, drying over anhydrous CaCl2 overnight, and distilling over CaH2under reduced pressure prior to use. All other chemicals were of analytical grade and used without further purification. PLina was obtained through autoxidation of linoleic acid as previously reported [23]. The 1H-NMR spectrum of PLina contained charac-teristic peaks of the related groups: (oˆ, ppm): 5.6–6.3 ppm
(the vinyl protons of the fatty acid macroperoxides), 2.3 ppm (–CH2–COOH of fatty acid macroperoxide). Peroxide analysis of the PLina fraction was carried out by a reflux of a mixture of 2-propanol (50 ml)/acetic acid (10 ml)/saturated aqueous solution of KI (1 ml) and 0.1 g of PLina for 10 min and titrating the released iodine against thiosulfate solution, according to a procedure reported in the literature [21]. The peroxygen content of the PLina sample was found to be approximately 1.0. One-Pot Polymerization Procedure
The typical polymerization procedure was as follows: 0.50 g of PLina and 0.01 g Sn(Oc)2were charged into a flame-dried Schlenk flask fitted with a magnetic stirring bar. Then 1.00 g of e-caprolactone and 1.00 g of styrene were injected into the Schlenk flask with a syringe under a nitrogen atmosphere. The flask was placed in an oil bath preheated at 110 °C. The crude polymer was dissolved in THF and poured into excess petroleum ether to precipitate the polymer. Then, precipitated polymer was dried under vacuum at 40 °C for 24 h.
Fractional Precipitations of the Graft Copolymers
Fractional precipitations of the polymers were carried out according to a literature procedure [47, 48]. A vacuum-dried polymer sample (0.5 g) was dissolved in 10 mL of THF. Petroleum ether was added drop-wise as a non-sol-vent to the solution, which was stirred continuously until completion of the first precipitation. After decantation, the upper layer of the solvent was treated by adding a non-solvent for the second precipitation to recover the maxi-mum amount of polymer. The same procedure was repe-ated until no more precipitation was observed. The gamma (c) values were calculated as the ratios of the total volume of petroleum ether used for each fraction to the volume of THF used for the same. The polymer fractions were sub-sequently dried under a vacuum.
Instrumentation
The1H-NMR and13C-NMR spectra of the polymers were recorded on a Bruker AVANCE 400 spectrometer (400 MHz), using CDCl3 as a solvent. 1H-DOSY-NMR spectra of polymers were recorded on a Bruker DRX-500 spectrometer (500 MHz). SEC measurements were per-formed using PL50 system equipped with a UV (254 nm) and an RI detector. Calibration was carried out using poly(styrene) standards provided by Polymer Laboratories. Tetrahydrofuran (THF) was used as an eluent at 40°C at a flow rate of 1 mL/min. Thermal analysis of the product was carried out using a Shimadzu differential scanning
calorimetry (DSC) DSC 60 series system under nitrogen. In a typical experiment, the polymer sample was dried for 24 h in a vacuum oven at 40°C. Then 10 mg of the sample was sealed in an aluminum DSC pan and heated from -50 to 150°C at a rate of 10 °C/min under N2atmosphere. The midpoint of the sharp curve was marked as the Tgof the measured sample [22]. The thermal decomposition of the samples was investigated using a Shimadzu-DTG 60H thermo-gravimetric analyzer; 10 mg of the sample was sealed in an aluminum DSC pan and heated from 20 to 600°C at a rate of 10 °C/min under N2 atmosphere. Fractional precipitation method was also used to charac-terize graft copolymers to separate their homopolymers according to the method reported in the literature [47]. Fractional precipitation was carried out as follows: the graft copolymer was dissolved in THF (solvent) and aliquot samples of the solution were withdrawn for the precipita-tion by adding different volumes of petroleum ether (non-solvent).
Results and Discussion
Synthesis of the Macroperoxy Initiator from Linoleic Acid
We have recently demonstrated the use of PLina, macr-operoxy initiator, in the free radical polymerization of selected vinyl monomers [20, 23]. PLina is useful for
incorporating hydrophobic and biodegradable oil-sourced polymers into graft copolymer structures. PLina has both peroxide groups for free radical polymerization of vinyl monomers and carboxylic groups for ring opening poly-merization of e-caprolactone. Thus, PLina has been used in one-pot polymerization of styrene and e-caprolactone to prepare PLina-g-PCL, PLina-g-PSt, and PLina-g-PSt-g-PCL graft shaped copolymers. The reaction pathway is shown in Scheme1. PLina, the macroperoxy initiator, was autoxidized for 90 days and the molar mass of 1,870 Da (PDI = 1.49) was obtained in quantitative yields. Peroxy-gen content of the soluble part of the PLina was found to be 1.10 wt%. The soluble part of the autoxidized linoleic acid acted as the macroperoxidic initiator in the polymerization of styrene and e-caprolactone.
One-Pot Graft Copolymerization
As mentioned above, PLina has both peroxide groups and carboxylic groups to simultaneously initiate the ring-opening polymerization of e-caprolactone and free radical polymerization of styrene. A monomer mixture of styrene and e-caprolactone that was initiated by the PLina initiator in the presence of Sn(Oc)2 as the ring opening catalyst provides PLina-g-PCL and PLina-g-PSt-g-PCL graft copolymers. This one-pot graft copolymerization approach has been studied extensively by varying the polymerization time, styrene concentration, e-caprolactone concentration as well as the PLina macroperoxy initiator concentration.
O O O O O R1 R2 R1 R2 R1 R2 R1 R2 OOH OO OOH Linoleic acid Air(O2) R1=C5H11 R2=(CH2)7COOH styrene ε-caprolactone + COOH COOH COOH
PLina-g-PSt-g-PCL graft copolymer
.
Scheme 1 Reaction design ofthe one-pot polymerization of styrene and e-caprolactone initiated by polymeric linoleic acid peroxide (PLina)
The obtained results are summarized in Tables1,2,3and
4. All graft copolymers obtained were precipitated from the THF/petroleum ether system.
The effect of the amount of e-caprolactone on one-pot graft copolymerization is presented in Table1.
PLina-g-PSt, PLina-g-PCL and PLina-g-PSt-g-PCL graft copoly-mers are also evaluated in Table 1. The increasing amount of e-caprolactone caused an expected increase in the yield and molar mass of the graft copolymers. The molar mass of the PLina-g-PSt graft copolymer is 22,700 Da (Mn) while Table 1 Free radical polymerization (FRP) and ring opening polymerization of PLina with styrene and e-caprolactone (e-CL) at 110°C for 5 h and effect of the amount of e-CL on one-pot graft copolymerization
Code e-CL (g) Yield (%) PLina* (wt%) PSt* (wt%) PCL* (wt%) Mn,SEC(kDa) Mw,SEC(kDa) PDI
PLiSta – 71.00 14.00 86 – 22.7 59.8 2.76 PLiCL 1.00 70.00 11.00 – 89 2.2 4.8 2.18 PLiStCL-1 1.00 61.41 13.30 61.3 25 48.69 133.23 2.74 PLiStCL-2 2.00 56.00 5.31 37.4 57 51.38 111.51 2.17 PLiSrCL-4 3.00 61.82 4.87 23.1 72 63.97 140.43 2.19 PLiStCL-5 4.00 56.15 5.29 17.8 77 70.95 141.49 2.20
Catalyst (Tin(II)-ethyl hexanoate)/Monomer: 1/100; PLina: 0.50 g; S: 2.00 g * Calculated from1H NMR
a FRP of PLina with styrene at 80°C for 5 h without catalyst; S: 1:00 g
Table 2 Effect of the amount of styrene on graft copolymerization at 110°C for 5 h
Code S (g) Yield (%) PLina* (wt%) PSt* (wt%) PCL* (wt%) Mn,SEC(kDa) Mw,SEC(kDa) PDI
PLiStCL-6 0.50 63 8.3 18.4 73.3 – – –
PLiStCL-7 1.50 63 6.1 45.7 48.2 46 85 1.82
PLiStCL-8 2.50 69 – – – – – –
PLiStCL-9 3.60 77 – – – 53 136 2.55
Catalyst (Tin(II)-ethyl hexanoate)/Monomer: 1/100; PLina: 0.50 g; e-CL: 1.00 g * Calculated from1H NMR
Table 3 Effect of the amount of PLina on graft copolymerization at 110°C for 5 h
Code PLina (g) Yield (%) PLina* (wt%) PSt* (wt%) PCL* (wt%) Mn,SEC(kDa) Mw,SEC(kDa) PDI
PLiStCL-10 0.20 55 5 12 83 96 126 1.31
PLiStCL-11 0.40 59 – – – 43 56 1.32
PLiStCL-12 0.60 53 9 23 68 38 53 1.40
PLiStCL-13 0.80 62 – – – 34 51 1.45
PLiStCL-14 1.00 59 16 27.5 6.5 29 46 1.59
Catalyst (Tin(II)-ethyl hexanoate)/Monomer: 1/100; S: 1.00 g; e-CL: 1.00 g * Calculated from1H NMR
Table 4 The effect of the polymerization time on one-pot graft copolymerization at 110°C
Code Time (h) Yield (g) Yield (wt%) ca M
n,SEC(kDa) Mw,SEC(kDa) PDI
PLiStCL-15 1 0.50 15 1.2–1.4 43.4 85.1 1.96
PLiStCL-16 3 1.10 33 1.6–2.5 47.4 92.2 1.95
PLiStCL-17 5 1.77 53 1.7–2.4 49.2 96.7 1.96
PLiStCL-18 8 2.14 64 1.3–1.6 56.3 111.2 1.98
PLiStCL-19 12 2.83 85 1.2–1.4 75.3 197.1 2.6
Catalyst (Tin(II)-ethyl hexanoate)/Monomer: 1/100; PLina: 0.50 g; S: 1.82 g; e-CL: 1.03 g
the molar mass of PLina-g-PCL is 2,200 Da (Mn). The molar masses of PLina-g-PSt-g-PCL three block graft copolymers range between 48,690 and 70,950 Da (Mn). It is evident that ring-opening polymerization is more effec-tive than free radical polymerization in this graft copoly-merization system.
Weight percentages of each block in the structure of the graft copolymers were also determined by1H NMR. The percentage of the amount of PCL is found to be 89 % in PLina-g-PCL (PLiCL) graft copolymers. The percentage of the amount of PSt is found to be 86 % in PLina-g-PSt (PLiSt) graft copolymers. The amount of polycaprolactone (PCL) in the triblock graft copolymer increased according to the amount of added e-caprolactone. The percentage of the amount of PCL is found to be 25 % PLiStCL-1, 57 % in 2, 72 % in PLiSrCL-4, and 77 % in PLiStCL-5, respectively.
The effect of the amount of styrene on one-pot graft copolymerization is shown in Table2. The increasing amount of styrene caused an expected increase in the yield and molar mass of the graft copolymers. At higher amounts of styrene, a deviation from normal behavior was observed, which may be attributed to the increase in viscosity of the medium.
The increased amount of polymeric linoleic acid per-oxide (PLina) in the reaction mixture leads to the formation of higher number of active centers. For this reason, more growing macro radicals are formed in the system, but they have shorter PSt segments, which is confirmed by a decrease in molar mass (96,000–29,000 Da) of the graft copolymers, as shown in Table3and Fig.1.
The effects of polymerization time on the copolymeri-zation by the application of simultaneous free radical polymerization and ring-opening polymerization processes
have been studied. The effect of the polymerization time on the one-pot graft copolymerization is presented in Table4. The SEC profile of PLina-g-PSt-g-PCL graft copolymers is
Fig. 1 Variation of the number average molar mass (Mn) with the increase in the initial PLina feeding
Fig. 2 SEC profiles of PLina and PLina-g-PSt-g-PCL graft copoly-mers [PLiStCL series in (Table4)] with time
Fig. 3 Variation of the molar mass (Mn) with the polymerization time
shown in Fig.2. The plot of Mn versus polymerization time is shown in Fig.3. For polymerizations of longer durations, polymers of higher molar mass are obtained. Longer polymerization times cause higher polymer yields. Higher amounts of the PLina cause a higher polymer yield (Table4). Increased amounts of initiator in the reaction mixture lead to the formation of a higher number of active centers. Consequently, increased numbers of growing macroradicals are formed in the system. Hence, it may be expected that they have shorter PSt segments, which is confirmed by a decrease in the molar masses of the graft copolymers, as shown in Table4.
The effect of monomer concentration on polydispersities is shown in Tables1,2and3. When both styrene and CL feed ratio is kept, low polydispersity is low. When amount of styrene is increased in graft copolymer, polydispersity increases because of free radical polymerization
mechanism. When amount of e-CL is increased, polydis-persity decreases because of ring opening polymerization effect (Tables1, 2). We see the effect of PLina concen-tration on polydispersity in Table 3. When PLina is increased in graft copolymer, polydispersity increases. The amount of peroxide increases as the PLina increases in graft copolymer structure. So, free radical polymerization becomes more dominant than ring opening polymerization. Characterization of Graft Copolymers
PLina, Poly(e-caprolactone), PLina-g-PCL, PLina-g-PSt, and PLinl-g-PSt-g-PCL graft copolymer samples were also characterized by using 1H-NMR and 1H-DOSY-NMR spectroscopy. 1H-NMR spectra of PLina and Poly(e-cap-rolactone) (PCL) are given in Figure S1 (supplementary information). Figure4 shows typical 1H-NMR spectra of
Fig. 4 1H-NMR spectra of g-PSt (PLiSt) and PLina-g-PSt-g-PCL (PLiStCL-1)
PLina-g-PSt (PLiSt), and PLina-g-PSt-g-PCL (PLiStCL-1) graft copolymer samples. 1H-NMR spectra of the graft copolymer samples contained characteristic peaks of the related segments: (d, ppm): 5.6–6.3 ppm (the vinyl protons of the fatty acid macroperoxides) and 0.9 ppm (–CH3 of fatty acid macroperoxide); (d, ppm): 4.1 ppm (–CH2–O– Poly(e-caprolactone); (d, ppm): 6.5–7.1 ppm (the phenyl protons in polystyrene). 1H NMR was also used to deter-mine the PLina, PCL, and PSt contents in mol% by cal-culating the peak areas of the methyl protons in PLina (0.9 ppm), phenyl protons in polystyrene (6.5–7.1 ppm) and (–CH2–O–) protons in Poly(e-caprolactone) segments (4.1 ppm) (given in Tables1,2,3).
Also, 1H DOSY NMR was used for characterization. Figure5shows a DOSY spectrum of PLina-g-PSt (PLiSt),
PLina-g-PCL (PLiCL) and PLina-g-PSt-g-PCL (PLiStCL-1) graft copolymers. In Fig.5a, PSt signals (–C6H5–) are seen in the region of 6.6–7.2 ppm. Also, PLina signals (– CH3) are seen in 0.9 ppm. PCL signals (–CH2–O) are also seen in 4.1 ppm in Fig.5b. In Fig.5c, a PLina-g-PSt-g-PCL (PLiStCL-1) graft copolymer sample of a well-rated DOSY spectrum is presented. It is possible to sepa-rate the three components and thus to obtain sepasepa-rate spectra for each of them because of their largely different diffusion coefficients. In this manner, pure graft copoly-mers isolated by fractional precipitation indicated the characteristic unimodal GPC traces, which can be attrib-uted pure graft copolymer confirmation (Fig.2).
Thermal analysis of graft copolymers was performed by DSC and TGA to determine the glass transition temperature Fig. 5 1H-DOSY spectrum of
aPLina-g-polystyrene (PLiSt), bPLina-g-poly(e-caprolactone) (PLiCL) and c PLina-g-
polystyrene-g-poly(e-caprolactone) (PLiStCL-1) graft copolymers
(Tg), the melting temperature (Tm), and decomposition temperatures (Td), respectively, in Table5. Figure6shows the DSC traces of the graft copolymers. A dramatic plasti-cizer effect of fatty acid macro peroxides was clearly observed. The melting temperatures related to PCL blocks were observed for each sample. Tm of the homo poly(e-caprolactone) (PCL) was observed to be 60.8°C. PLina-g-PCL graft copolymer sample (PLiCL)’s Tmwas observed to be 48°C. In addition, the PLina-g-PSt (PLiSt) graft copolymer has exhibited one Tg= 53°C. When we look at the DSC traces of the PLina-g-PSt-g-PCL graft copolymers, we see Tmand Tg. Tmand Tgvalues were observed for the samples for PLiStCL-2 (Tg= 40°C and Tm= 52°C) and Table 5 Thermal properties of the PLina,
Poly(e-caprolac-tone)(PCL), g-PCL (PLiCL), g-PSt (PLiSt) and PLina-g-PCL-g-PCL (PLiStCL) graft copolymers
Code DSC (°C) TGA (°C) Tg Tm Td1 Td2 Td3 PLinaa – 29 170 353 463 PCL – 60.8 370 – – PLiCL – 48 415 450 – PLiSt 53 – 100 425 – PLiStCL-2 40 52 425 460 – PLiStCL-7 38 50 420 435 – PLiStCL-14 5 38 420 455 –
a Taken from Ref. [20]
Fig. 6 DSC traces of the graft copolymers
PLiStCL-7 (Tg= 38°C and Tm= 50°C) and PLiStCL-14 (Tg= 5°C and Tm= 38°C).
Figure7shows the TGA traces of the graft copolymers. Decomposition temperatures, Td, of the graft copolymers were observed to be similar to those of PLina, PCL. One Td was observed for homo poly(e-caprolactone) (PCL): Td1= 370°C.
Fractional Precipitation
Fractional precipitation experiments also provided evidence for the formation of graft copolymers. The gamma values (c) of the PLina-g-PSt-g-PCL graft copolymers were between 1.20 and 2.50, as shown in Table4, when the solvent was THF and the nonsolvent was petroleum ether. In this solvent–nonsolvent system, the c values were found to be between 2.5 and 3.2 for homo-PSt and between 0.90 and 1.20 for homo-PCL. The c values of the block copolymers were ranged between those of homo-PSt and homo-PCL. It can also be concluded that homopolymer formation was not present because no polymer precipitation was observed at the c values of the related homopolymers.
Conclusions
Graft copolymers having the structure of poly(linoleic acid)-g-polystyrene-g-poly(e-caprolactone) were synthe-sized from polymeric linoleic acid peroxide (PLina) pos-sessing peroxide groups in the main chain by the combination of free radical polymerization of styrene and ring-opening polymerization of e-caprolacton in one-pot. A set of one-pot synthesis and FRP and ROP polymerization conditions of two different graft copolymers, poly(linoleic poly(e-caprolactone) and poly(linoleic acid)-g-polystyrene-g-poly(e-caprolactone), were evaluated. Graft copolymers of PCL are very important for medical appli-cations in drug-delivery systems and tissue engineering. The autoxidized linoleic acid peroxide used for the one-pot synthesis of these types of graft copolymers can be crucial for the synthesis of graft copolymers based on biodegrad-able polyesters.
Acknowledgments This work was supported financially by the Turkish Scientific Research Council (Grants Numbers: 110T884, 211T016), the Du¨zce University Research Fund (Grant Number: 2011.05.HD.026, 2011.05.03.068, 2011.05.HD.052) the Bu¨lent Ecevit University Research Fund (Grant Number: 2012-10-03-03).
References
1. Allı S, Allı A, Hazer B (2012) Hyperbranched homo and thermo responsive graft copolymers by using ATRP-macromonomer initiators. J Appl Polym Sci 124:536–548
2. Savaskan S, Hazer B (1996) Synthesis of a new macromonomeric peroxyinitiator (MMPI) having poly tetrahydrofurane units. An-gew Makromol Chem 239:13–26
3. Hazer B (1996) Poly(b-hydroxy nonanoate) and polystyrene or poly(methyl methacrylate) graft copolymers: microstructure characteristics and mechanical and thermal behavior. Macromol Chem Phys 197:431–441
4. Yildiz U, Hazer B, Tauer K (2012) Tailoring polymer architec-tures with macromonomer azoinitiators. Polym Chem 3:1107–1118
5. Bernaerts KV, Du Prez FE (2006) Dual/heterofunctional initiators for the combination of mechanistically distinct polymerization techniques. Prog Polym Sci 31:671–722
6. Hadjichristidis N, Iatrou H, Pispas S, Pistikalis M (2000) Anionic polymerization: high vacuum techniques. J Polym Sci Part A: Polym Chem 38:3211–3234
7. Grubbs RT, Tumas W (1989) Polym Synth Organotransition Metal Chem Sci 243:907–915
8. Kamigaito M, Ando T, Sawamoto M (2001) Metal-catalyzed living radical polymerization. Chem Rev 101:3689–3746 9. Matyjaszewski K, Xia J (2001) Atom transfer radical
polymeri-zation. Chem Rev 101:2921–2990
10. Hawker CJ, Bosman AW, Harth E (2001) New polymer synthesis by nitroxide mediated living radical polymerizations. Chem Rev 101:3661–3688
11. Keles¸ E, Hazer B (2009) Synthesis of segmented polyurethane based on polymeric soybean oil polyol and poly(ethylene glycol). J Polym Environ 17:153–158
12. C¸ akmakli B, Hazer B, Tekin I˙O¨ , Co¨mert FB (2005) Synthesis and characterization of polymeric soybean oil-g-methyl methacrylate (and n-butyl methacrylate) graft copolymers. Biomacromolecules 6:1750–1758
13. Ilter S, Hazer B, Borcakli M, Atici O (2001) Graft copolymeriza-tion of methyl methacrylate onto a bacterial polyester containing unsaturated side chains. Macromol Chem Phys 202:2281–2286 14. Hazer B, Demirel SI˙, Borcakli M, Eroglu MS, Cakmak M, Erman
B (2001) Free radical crosslinking of unsaturated bacterial poly-esters obtained from soybean oily acids. Polym Bull 46:389–394 15. Hazer B, Hazer DB, C¸ oban B (2010) Synthesis of microbial elastomers based on soybean oil. Autoxidation kinetics, thermal and mechanical properties. J Polym Res 17:567–577
16. Tallman KA, Pratt DA, Porter NA (2001) Kinetic products of linoleate peroxidation: rapid beta-fragmentation of nonconju-gated peroxyls. J Am Chem Soc 123:11827–11828
17. Weenen H, Porter NA (1982) Autoxidation of model membrane systems-co-oxidation of poly-unsaturated lecithins with steroids, fatty-acids, and alpha-tocopherol. J Am Chem Soc 104: 5216–5221
18. Wold CR, Ni H, Soucek MD (2001) Model reaction study on the interaction between the inorganic and organic phases in drying oil based ceramer coatings. Chem Mater 13:3032–3037
19. Cakmakli B, Hazer B, Tekin I˙O, Comert FB (2005) Synthesis and characterization of polymeric soybean oil-g-methyl methacrylate (and n-butyl methacrylate) graft copolymers: biocompatibility and bacterial adhesion. Biomacromolecules 6:1750–1758 20. Cakmakli B, Hazer B, Tekin I˙O¨ , Acikgoz S, Can M (2007)
PMMA-multigraft copolymers derived from linseed oil, soybean oil, and linoleic acid: protein adsorption and bacterial adherence. J Am Oil Chem Soc 84:73–81
21. Cakmakli B, Hazer B, Tekin I˙O¨ , Kizgut S, Koksal M, Mence-loglu Y (2004) Synthesis and characterization of polymeric lin-seed oil grafted methyl methacrylate or styrene. Macromol Biosci 4:649–655
22. Allı A, Hazer B (2008) Poly(N-isopropylacrylamide) thermore-sponsive cross-linked conjugates containing polymeric soybean oil and/or polypropylene glycol. Eur Polym J 44:1701–1713
23. Allı A, Hazer B (2011) Synthesis and characterization of poly(N-isopropyl acryl amide)-g-poly(linoleic acid)/poly(linolenic acid) graft copolymers. J Am Oil Chem Soc 88:255–263
24. O¨ ztu¨rk T, Go¨ktas¸ M, Hazer B (2010) One-step synthesis of triarm block copolymers via simultaneous reversible-addition fragmen-tation chain transfer and ring-opening polymerization. J Appl Polym Sci 117:1638–1645
25. Schmid C, Falkenhagen J, Barner-Kowollik CJ (2011) An effi-cient avenue to poly(styrene)-block-poly(epsilon-caprolactone) polymers via switching from RAFT to hydroxyl functionality: synthesis and characterization. Polym Sci Part A Polym Chem 49:1–10
26. Yu YC, Li G, Kang HU, Youk JU (2012) One-step synthesis of poly(alkyl methacrylate)-b-polyester block copolymers via a dual initiator route combining RAFT polymerization and ROP. Coll Polym Sci 290:1707–1712
27. Le Hellaye M, Lefay C, Davis TP, Stenzel MH, Barner-Kowollik CJ (2008) Simultaneous reversible addition fragmentation chain transfer and ring-opening polymerization. J Polym Sci Part A: Polym Chem 46:3058–3067
28. Hong J, Wang Q, Fan Z (2006) Synthesis of multiblock polymer containing narrow polydispersity blocks. Macromol Rapid Commun 27:57–62
29. Cheng C, Khoshdel E, Wooley KL (2007) One-pot tandem syn-thesis of a core: shell brush copolymer from small molecule reactants by ring-opening metathesis and reversible addition-fragmentation chain transfer (co)polymerizations. Macromole-cules 4:2289–2292
30. Mahanthappa MK, Bates FS, Hillmyer MA (2005) Synthesis of ABA triblock copolymers by a tandem ROMP-RAFT strategy. Macromolecules 38:7890–7894
31. Mori H, Masuda S, Endo T (2008) Ring-opening copolymerization of 10-methylene-9,10-dihydroanthryl-9-spirophenylcyclopropane via free radical and RAFT processes. Macromolecules 41:632–639 32. Han DH, Pan CY (2007) Preparation and characterization of heteroarm H-shaped terpolymers by combination of reversible addition-fragmentation transfer polymerization and ring-opening polymerization. J Polym Sci Part A: Polym Chem 45:789–799 33. Xu XQ, Jia ZF, Sun RM, Huang JL (2006) Synthesis of
well-defined, brush-type, amphiphilic [poly(styrene-co-2-hydroxyethyl methacrylate)-graft-poly(epsilon-caprolactone)]-b-poly(ethylene oxide)-b-[poly(styrene-co-2-hydroxyethyl methacrylate)-graft-poly(epsilon-caprolactone)] and its aggregation behavior in aqueous media. J Polym Sci Part A: Polym Chem 44:4396–4408 34. Xu XW, Huang JL (2006) Synthesis and characterization of amphiphilic copolymer of linear poly(ethylene oxide) linked with [poly(styrene-co-2-hydroxyethyl methacrylate)graft-poly(epsi-lon-caprolactone)] using sequential controlled polymerization. J Polym Sci Part A: Polym Chem 44:467–476
35. Liu J, Pan CY (2005) Synthesis and characterization of H-shaped copolymers by combination of RAFT polymerization and CROP. Polymer 46:11133–11141
36. Wang WP, You YZ, Hong CY, Xu J, Pan CY (2005) Synthesis of comb-shaped copolymers by combination of reversible
addition-fragmentation chain transfer polymerization and cationic ring-opening polymerization. Polymer 46:9489–9494
37. Shi PJ, Li YG, Pan CY (2004) Block and star block copolymers by mechanism transformation: X. Synthesis of poly(ethylene oxide) methyl ether/polystyrene/poly(L-lactide) ABC miktoarm star copolymers of by combination of RAFT and ROP. Eur Polym J 40:1283–1290
38. You Y, Hong C, Wang W, Lu W, Pan CY (2004) Preparation and characterization of thermally responsive and biodegradable block copolymer comprised of PNIPAAM and PLA by combination of ROP and RAFT methods. Macromolecules 37:9761–9797 39. Chang C, Wei H, Quan CY, Li YY, Liu J, Wang ZC, Cheng SX,
Zhang XZ, Zhuo RX (2008) Fabrication of thermosensitive PCL-PNIPAAm-PCL triblock copolymeric micelles for drug delivery. J Polym Sci Part A Polym Chem 46:3048–3057
40. Luan B, Zhang BQ, Pan CY (2006) Synthesis and characteriza-tions of well-defined branched polymers with AB(2) branches by combination of RAFT polymerization and ROP as well as ATRP. J Polym Sci Part A: Polym Chem 44:549–560
41. Li YG, Wang YM, Pan CY (2003) Block and star block copolymers by mechanism transformation 9: preparation and characterization of poly(methyl methacrylate)/poly(1,3-dioxe-pane)/polystyrene ABC miktoarm star copolymers by combina-tion of reversible addition-fragmentation chain-transfer polymerization and cationic ring-opening polymerization. J Polym Sci Part A: Polym Chem 41:1243–1250
42. Huang CF, Kuo SW, Lee HF, Chang FC (2005) A new strategy for the one-step synthesis of block copolymers through simulta-neous free radical and ring opening polymerizations using a dual-functional initiator. Polymer 46:1561–1565
43. Sogah DY, Di J (2006) Exfoliated block copolymer/silicate nanocomposites by one-pot, one-step in situ living polymeriza-tion from silicate-anchored multifuncpolymeriza-tional initiator. Macromol-ecules 39:5052–5057
44. Benoit D, Hawker CJ, Huang EE, Lin Z, Russel TP (2000) One-step formation of functionalized block copolymers. Macromole-cules 33:1505–1507
45. Geus MD, Schormans L, Palmans ARA, Koning CE, Heise A (2006) Block copolymers by chemoenzymatic cascade polymer-ization: a comparison of consecutive and simultaneous reactions. J Polym Sci Part A: Polym Chem 44:4290–4297
46. O¨ ztu¨rk T, Cakmak I˙ (2008) One-step synthesis of multiphase block copolymers via simultaneous free radical and ring opening polymerization using poly(ethylene oxide) possessing azo group. J Macromol Sci Part A Pure and Appl Chem 45:572–577 47. Hazer B, Baysal BM (1986) Preparation of block copolymers
using a new polymeric peroxycarbamate. Polymer 27:961–968 48. Hazer B, Besirli N, Ayas A, Baysal BM (1989) Preparation of
ABCBA-type block copolymers by use of macro-initiators con-taining peroxy and azo groups. Makromol Chem Phys 190:1987–1996
